Scholars@Duke
Christoph F. Schmidt

Christoph F. Schmidt

Hertha Sponer Distinguished Professor of Physics
Physics
christoph.schmidt@duke.edu
Box 90305, Durham, NC 27708
2316 French Family Science Center, Duke Box 90305, 124 Science Drive, Durham, NC 27708
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Selected Publications

Minimal vertex model explains how the amnioserosa avoids fluidization during Drosophila dorsal closure.

Journal Article bioRxiv · December 22, 2023 UNLABELLED: Dorsal closure is a process that occurs during embryogenesis of Drosophila melanogaster . During dorsal closure, the amnioserosa (AS), a one-cell thick epithelial tissue that fills the dorsal opening, shrinks as the lateral epidermis sheets con ... Full text Link to item Cite

Minimal vertex model explains how the amnioserosa avoids fluidization during Drosophila dorsal closure.

Journal Article ArXiv · December 20, 2023 Dorsal closure is a process that occurs during embryogenesis of Drosophila melanogaster. During dorsal closure, the amnioserosa (AS), a one-cell thick epithelial tissue that fills the dorsal opening, shrinks as the lateral epidermis sheets converge and eve ... Link to item Cite

DNA-Based Optical Sensors for Forces in Cytoskeletal Networks

Journal Article ACS Applied Nano Materials · September 8, 2023 Mechanical forces are relevant for many biological processes, from wound healing and tumor formation to cell migration and differentiation. Cytoskeletal actin is largely responsible for responding to forces and transmitting them in cells, while also mainta ... Full text Cite

Nucleotide-free structures of KIF20A illuminate atypical mechanochemistry in this kinesin-6.

Journal Article Open biology · September 2023 KIF20A is a critical kinesin for cell division and a promising anti-cancer drug target. The mechanisms underlying its cellular roles remain elusive. Interestingly, unusual coupling between the nucleotide- and microtubule-binding sites of this kinesin-6 has ... Full text Cite

DeepProjection: specific and robust projection of curved 2D tissue sheets from 3D microscopy using deep learning.

Journal Article Development · November 1, 2022 The efficient extraction of image data from curved tissue sheets embedded in volumetric imaging data remains a serious and unsolved problem in quantitative studies of embryogenesis. Here, we present DeepProjection (DP), a trainable projection algorithm bas ... Full text Link to item Cite

DeepProjection: Rapid and structure-specific projections of tissue sheets embedded in 3D microscopy stacks using deep learning

Journal Article bioRxiv · November 17, 2021 AbstractThe efficient extraction of local high-resolution content from massive amounts of imaging data remains a serious and unsolved problem in studies of complex biological tissues. Here we present DeepProjection, a train ... Full text Cite

Multiscale Microrheology Using Fluctuating Filaments as Stealth Probes.

Journal Article Physical review letters · October 2021 The mechanical properties of soft materials can be probed on small length scales by microrheology. A common approach tracks fluctuations of micrometer-sized beads embedded in the medium to be characterized. This approach yields results that depend on probe ... Full text Cite

Mapping Activity-Dependent Quasi-stationary States of Mitochondrial Membranes with Graphene-Induced Energy Transfer Imaging.

Journal Article Nano letters · October 2021 Graphene-induced energy transfer (GIET) was recently introduced for sub-nanometric axial localization of fluorescent molecules. GIET relies on near-field energy transfer from an optically excited fluorophore to a single sheet of graphene. Recently, we demo ... Full text Cite

Rapid local compression in active gels is caused by nonlinear network response.

Journal Article Soft matter · October 2020 The actin cytoskeleton in living cells generates forces in conjunction with myosin motor proteins to directly and indirectly drive essential cellular processes. The semiflexible filaments of the cytoskeleton can respond nonlinearly to the collective action ... Full text Open Access Cite

Introduction to Active Matter.

Journal Article Soft matter · August 2020 Full text Cite

Length-Selective Dielectrophoretic Manipulation of Single-Walled Carbon Nanotubes.

Journal Article Analytical chemistry · July 2020 Single-walled carbon nanotubes (SWNTs) possess unique physical, optical, and electrical properties with great potential for future nanoscale device applications. Common synthesis procedures yield SWNTs with large length polydispersity and varying chirality ... Full text Cite

Towards separation of single walled carbon nanotubes with insulator-based dielectrophoresis

Conference 21st International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2017 · January 1, 2020 Single-walled carbon nanotubes (SWNT) display large structural and length polydispersity when produced by common methods. Electrical and optical applications therefore could strongly profit from selection and purification methods. Insulator-based dielectro ... Cite

Carbon Dots for Studying Muscle Architecture

Journal Article ACS Applied Nano Materials · December 27, 2019 We introduce a carbon-dot-based fluorescent label for F-actin with high labeling specificity that allowed us to perform three-dimensional fluorescence imaging of thick muscle tissues. Actin-binding proteins play a pivotal role in the sarcomere, regulating ... Full text Cite

Chromophore-Independent Roles of Opsin Apoproteins in Drosophila Mechanoreceptors.

Journal Article Current biology : CB · September 2019 Rhodopsins, the major light-detecting molecules of animal visual systems [1], consist of opsin apoproteins that covalently bind a retinal chromophore with a conserved lysine residue [1, 2]. In addition to capturing photons, this chromophore contributes to ... Full text Cite

Physics meets medicine - At the heart of active matter.

Journal Article Progress in biophysics and molecular biology · July 2019 Full text Cite

Minimal vertex model explains how the amnioserosa avoids fluidization during Drosophila dorsal closure.

Journal Article bioRxiv · December 22, 2023 UNLABELLED: Dorsal closure is a process that occurs during embryogenesis of Drosophila melanogaster . During dorsal closure, the amnioserosa (AS), a one-cell thick epithelial tissue that fills the dorsal opening, shrinks as the lateral epidermis sheets con ... Full text Link to item Cite

Minimal vertex model explains how the amnioserosa avoids fluidization during Drosophila dorsal closure.

Journal Article ArXiv · December 20, 2023 Dorsal closure is a process that occurs during embryogenesis of Drosophila melanogaster. During dorsal closure, the amnioserosa (AS), a one-cell thick epithelial tissue that fills the dorsal opening, shrinks as the lateral epidermis sheets converge and eve ... Link to item Cite

DNA-Based Optical Sensors for Forces in Cytoskeletal Networks

Journal Article ACS Applied Nano Materials · September 8, 2023 Mechanical forces are relevant for many biological processes, from wound healing and tumor formation to cell migration and differentiation. Cytoskeletal actin is largely responsible for responding to forces and transmitting them in cells, while also mainta ... Full text Cite

Nucleotide-free structures of KIF20A illuminate atypical mechanochemistry in this kinesin-6.

Journal Article Open biology · September 2023 KIF20A is a critical kinesin for cell division and a promising anti-cancer drug target. The mechanisms underlying its cellular roles remain elusive. Interestingly, unusual coupling between the nucleotide- and microtubule-binding sites of this kinesin-6 has ... Full text Cite

DeepProjection: specific and robust projection of curved 2D tissue sheets from 3D microscopy using deep learning.

Journal Article Development · November 1, 2022 The efficient extraction of image data from curved tissue sheets embedded in volumetric imaging data remains a serious and unsolved problem in quantitative studies of embryogenesis. Here, we present DeepProjection (DP), a trainable projection algorithm bas ... Full text Link to item Cite

DeepProjection: Rapid and structure-specific projections of tissue sheets embedded in 3D microscopy stacks using deep learning

Journal Article bioRxiv · November 17, 2021 AbstractThe efficient extraction of local high-resolution content from massive amounts of imaging data remains a serious and unsolved problem in studies of complex biological tissues. Here we present DeepProjection, a train ... Full text Cite

Multiscale Microrheology Using Fluctuating Filaments as Stealth Probes.

Journal Article Physical review letters · October 2021 The mechanical properties of soft materials can be probed on small length scales by microrheology. A common approach tracks fluctuations of micrometer-sized beads embedded in the medium to be characterized. This approach yields results that depend on probe ... Full text Cite

Mapping Activity-Dependent Quasi-stationary States of Mitochondrial Membranes with Graphene-Induced Energy Transfer Imaging.

Journal Article Nano letters · October 2021 Graphene-induced energy transfer (GIET) was recently introduced for sub-nanometric axial localization of fluorescent molecules. GIET relies on near-field energy transfer from an optically excited fluorophore to a single sheet of graphene. Recently, we demo ... Full text Cite

Rapid local compression in active gels is caused by nonlinear network response.

Journal Article Soft matter · October 2020 The actin cytoskeleton in living cells generates forces in conjunction with myosin motor proteins to directly and indirectly drive essential cellular processes. The semiflexible filaments of the cytoskeleton can respond nonlinearly to the collective action ... Full text Open Access Cite

Introduction to Active Matter.

Journal Article Soft matter · August 2020 Full text Cite

Length-Selective Dielectrophoretic Manipulation of Single-Walled Carbon Nanotubes.

Journal Article Analytical chemistry · July 2020 Single-walled carbon nanotubes (SWNTs) possess unique physical, optical, and electrical properties with great potential for future nanoscale device applications. Common synthesis procedures yield SWNTs with large length polydispersity and varying chirality ... Full text Cite

Towards separation of single walled carbon nanotubes with insulator-based dielectrophoresis

Conference 21st International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2017 · January 1, 2020 Single-walled carbon nanotubes (SWNT) display large structural and length polydispersity when produced by common methods. Electrical and optical applications therefore could strongly profit from selection and purification methods. Insulator-based dielectro ... Cite

Carbon Dots for Studying Muscle Architecture

Journal Article ACS Applied Nano Materials · December 27, 2019 We introduce a carbon-dot-based fluorescent label for F-actin with high labeling specificity that allowed us to perform three-dimensional fluorescence imaging of thick muscle tissues. Actin-binding proteins play a pivotal role in the sarcomere, regulating ... Full text Cite

Chromophore-Independent Roles of Opsin Apoproteins in Drosophila Mechanoreceptors.

Journal Article Current biology : CB · September 2019 Rhodopsins, the major light-detecting molecules of animal visual systems [1], consist of opsin apoproteins that covalently bind a retinal chromophore with a conserved lysine residue [1, 2]. In addition to capturing photons, this chromophore contributes to ... Full text Cite

Physics meets medicine - At the heart of active matter.

Journal Article Progress in biophysics and molecular biology · July 2019 Full text Cite

Drebrin-like protein regulates body bending ofC. elegansvia suppression of NCA cation leak channels

Journal Article · 2019 Drebrin-like protein (DBN-1) in C. elegans is an adaptor protein that connects different cellular pathways to the actin cytoskeleton. Using a CRISPR-Cas9 system, we generated a new dbn-1 allele, which lacks 80% of C-terminal part of DBN-1. The mutant displ ... Full text Cite

Reply to the 'Comment on "A symmetrical method to obtain shear moduli from microrheology"' by M. Tassieri, Soft Matter, 2018, 14, DOI.

Journal Article Soft matter · October 2018 The Comment on our paper introducing "a symmetric method to obtain shear moduli from microrheology" proposes an interpolation method to generate oversampled data from an original time series that are then used to approximate shear moduli at frequencies "be ... Full text Cite

Comment on "A symmetrical method to obtain shear moduli from microrheology" by K. Nishi, M. L. Kilfoil, C. F. Schmidt, and F. C. MacKintosh, Soft Matter, 2018, 14, 3716.

Journal Article Soft matter · October 2018 Nishi et al. have presented a new analytical method for transforming the time-dependent materials' compliance into their frequency-dependent complex shear modulus, without the need of a preconceived fitting function nor the use of Kramers-Kronig transforma ... Full text Cite

Self-organized stress patterns drive state transitions in actin cortices.

Journal Article Science advances · June 2018 Biological functions rely on ordered structures and intricately controlled collective dynamics. This order in living systems is typically established and sustained by continuous dissipation of energy. The emergence of collective patterns of motion is uniqu ... Full text Cite

A symmetrical method to obtain shear moduli from microrheology.

Journal Article Soft matter · May 2018 Passive microrheology typically deduces shear elastic loss and storage moduli from displacement time series or mean-squared displacements (MSD) of thermally fluctuating probe particles in equilibrium materials. Common data analysis methods use either Krame ... Full text Cite

Topology determines force distributions in one-dimensional random spring networks.

Journal Article Physical review. E · February 2018 Networks of elastic fibers are ubiquitous in biological systems and often provide mechanical stability to cells and tissues. Fiber-reinforced materials are also common in technology. An important characteristic of such materials is their resistance to fail ... Full text Cite

Topology Counts: Force Distributions in Circular Spring Networks.

Journal Article Physical review letters · February 2018 Filamentous polymer networks govern the mechanical properties of many biological materials. Force distributions within these networks are typically highly inhomogeneous, and, although the importance of force distributions for structural properties is well ... Full text Cite

Microfluidic device for chemical and mechanical manipulation of suspended cells

Journal Article Journal of Physics D: Applied Physics · January 10, 2018 Microfluidic devices have proven to be useful and versatile for cell studies. We here report on a method to adapt microfluidic stickers made from UV-curable optical adhesive with inserted permeable hydrogel membrane micro-windows for mechanical studies of ... Full text Cite

Mechanical Properties of a Drosophila Larval Chordotonal Organ.

Journal Article Biophysical journal · December 2017 Proprioception is an integral part of the feedback circuit that is essential for locomotion control in all animals. Chordotonal organs perform proprioceptive and other mechanosensory functions in insects and crustaceans. The mechanical properties of these ... Full text Cite

Single-Walled Carbon Nanotubes Probed with Insulator-Based Dielectrophoresis.

Journal Article Analytical chemistry · December 2017 Single-walled carbon nanotubes (SWNTs) offer unique electrical and optical properties. Common synthesis processes yield SWNTs with large length polydispersity (several tens of nanometers up to centimeters) and heterogeneous electrical and optical propertie ... Full text Cite

Physical probing of cells

Journal Article Journal of Physics D: Applied Physics · October 13, 2017 In the last two decades, it has become evident that the mechanical properties of the microenvironment of biological cells are as important as traditional biochemical cues for the control of cellular behavior and fate. The field of cell and matrix mechanics ... Full text Cite

Feedback-tracking microrheology in living cells.

Journal Article Science advances · September 2017 Living cells are composed of active materials, in which forces are generated by the energy derived from metabolism. Forces and structures self-organize to shape the cell and drive its dynamic functions. Understanding the out-of-equilibrium mechanics is cha ... Full text Cite

Nonequilibrium dynamics of probe filaments in actin-myosin networks.

Journal Article Physical review. E · August 2017 Active dynamic processes of cells are largely driven by the cytoskeleton, a complex and adaptable semiflexible polymer network, motorized by mechanoenzymes. Small dimensions, confined geometries, and hierarchical structures make it challenging to probe dyn ... Full text Cite

Molecular force sensors to measure stress in cells

Journal Article Journal of Physics D: Applied Physics · May 15, 2017 Molecularly generated forces are essential for most activities of biological cells, but also for the maintenance of steady state or homeostasis. To quantitatively understand cellular dynamics in migration, division, or mechanically guided differentiation, ... Full text Cite

Designing deoxidation inhibiting encapsulation of metal oxide nanostructures for fluidic and biological applications

Journal Article Applied Surface Science · December 30, 2016 Due to their photoluminescence, metal oxide nanostructures such as ZnO nanostructures are promising candidates in biomedical imaging, drug delivery and bio-sensing. To apply them as label for bio-imaging, it is important to study their structural stability ... Full text Cite

Broken Detailed Balance of Filament Dynamics in Active Networks.

Journal Article Physical review letters · June 2016 Myosin motor proteins drive vigorous steady-state fluctuations in the actin cytoskeleton of cells. Endogenous embedded semiflexible filaments such as microtubules, or added filaments such as single-walled carbon nanotubes are used as novel tools to noninva ... Full text Cite

Phosphorylation of FEZ1 by Microtubule Affinity Regulating Kinases regulates its function in presynaptic protein trafficking.

Journal Article Scientific reports · June 2016 Adapters bind motor proteins to cargoes and therefore play essential roles in Kinesin-1 mediated intracellular transport. The regulatory mechanisms governing adapter functions and the spectrum of cargoes recognized by individual adapters remain poorly defi ... Full text Cite

The natural diterpene tonantzitlolone A and its synthetic enantiomer inhibit cell proliferation and kinesin-5 function.

Journal Article European journal of medicinal chemistry · April 2016 Tonantzitlolone A, a diterpene isolated from the Mexican plant Stillingia sanguinolenta, shows cytostatic activity. Both the natural product tonantzitlolone A and its synthetic enantiomer induce monoastral spindle formation in cell experiments which indica ... Full text Cite

Broken detailed balance at mesoscopic scales in active biological systems.

Journal Article Science (New York, N.Y.) · April 2016 Systems in thermodynamic equilibrium are not only characterized by time-independent macroscopic properties, but also satisfy the principle of detailed balance in the transitions between microscopic configurations. Living systems function out of equilibrium ... Full text Cite

Game of Zones: how actin-binding proteins organize muscle contraction.

Journal Article Worm · April 2016 Locomotion of C. elegans requires coordinated, efficient transmission of forces generated on the molecular scale by myosin and actin filaments in myocytes to dense bodies and the hypodermis and cuticle enveloping body wall muscles. The complex organization ... Full text Cite

Super-Resolution Optical Fluctuation Bio-Imaging with Dual-Color Carbon Nanodots.

Journal Article Nano letters · January 2016 Success in super-resolution imaging relies on a proper choice of fluorescent probes. Here, we suggest novel easily produced and biocompatible nanoparticles-carbon nanodots-for super-resolution optical fluctuation bioimaging (SOFI). The particles revealed a ... Full text Cite

Sulfo-SMCC Prevents Annealing of Taxol-Stabilized Microtubules In Vitro.

Journal Article PloS one · January 2016 Microtubule structure and functions have been widely studied in vitro and in cells. Research has shown that cysteines on tubulin play a crucial role in the polymerization of microtubules. Here, we show that blocking sulfhydryl groups of cysteines in taxol- ... Full text Cite

Mechanical properties of the lch5 organ of Drosophila.

Conference MOLECULAR BIOLOGY OF THE CELL · 2016 Cite

Force fluctuations in three-dimensional suspended fibroblasts.

Conference MOLECULAR BIOLOGY OF THE CELL · 2016 Cite

Deletion of the Tail Domain of the Kinesin-5 Cin8 Affects Its Directionality.

Journal Article The Journal of biological chemistry · July 2015 The bipolar kinesin-5 motors are one of the major players that govern mitotic spindle dynamics. Their bipolar structure enables them to cross-link and slide apart antiparallel microtubules (MTs) emanating from the opposing spindle poles. The budding yeast ... Full text Cite

Drebrin-like protein DBN-1 is a sarcomere component that stabilizes actin filaments during muscle contraction.

Journal Article Nature communications · July 2015 Actin filament organization and stability in the sarcomeres of muscle cells are critical for force generation. Here we identify and functionally characterize a Caenorhabditis elegans drebrin-like protein DBN-1 as a novel constituent of the muscle contracti ... Full text Cite

Swelling and softening of the cowpea chlorotic mottle virus in response to pH shifts.

Journal Article Biophysical journal · May 2015 Cowpea chlorotic mottle virus (CCMV) forms highly elastic icosahedral protein capsids that undergo a characteristic swelling transition when the pH is raised from 5 to 7. Here, we performed nano-indentation experiments using an atomic force microscope to t ... Full text Cite

The mechanical properties of early Drosophila embryos measured by high-speed video microrheology.

Journal Article Biophysical journal · April 2015 In early development, Drosophila melanogaster embryos form a syncytium, i.e., multiplying nuclei are not yet separated by cell membranes, but are interconnected by cytoskeletal polymer networks consisting of actin and microtubules. Between division cycles ... Full text Cite

Intracellular and extracellular forces drive primary cilia movement.

Journal Article Proceedings of the National Academy of Sciences of the United States of America · February 2015 Primary cilia are ubiquitous, microtubule-based organelles that play diverse roles in sensory transduction in many eukaryotic cells. They interrogate the cellular environment through chemosensing, osmosensing, and mechanosensing using receptors and ion cha ... Full text Cite

Force fluctuations in three-dimensional suspended fibroblasts.

Journal Article Philosophical transactions of the Royal Society of London. Series B, Biological sciences · February 2015 Cells are sensitive to mechanical cues from their environment and at the same time generate and transmit forces to their surroundings. To test quantitatively forces generated by cells not attached to a substrate, we used a dual optical trap to suspend 3T3 ... Full text Cite

Microporous device for local electric recordings on model lipid bilayers

Journal Article Journal of Physics D: Applied Physics · January 21, 2015 A powerful approach for characterizing lipid membranes and embedded proteins is the reconstitution of model lipid bilayers. The extreme fragility of 5 nm thick bilayers is a challenge for device design and requires a trade off of stability against accessib ... Full text Cite

Elasticity of 3D networks with rigid filaments and compliant crosslinks.

Journal Article Soft matter · January 2015 Disordered filamentous networks with compliant crosslinks exhibit a low linear elastic shear modulus at small strains, but stiffen dramatically at high strains. Experiments have shown that the elastic modulus can increase by up to three orders of magnitude ... Full text Cite

Viscoelastic mechanics of non-adhering cells

Conference EUROPEAN BIOPHYSICS JOURNAL WITH BIOPHYSICS LETTERS · 2015 Cite

Force fluctuations in three-dimensional suspended fibroblasts

Conference MOLECULAR BIOLOGY OF THE CELL · 2015 Cite

High-resolution mapping of intracellular fluctuations using carbon nanotubes.

Journal Article Science (New York, N.Y.) · May 2014 Cells are active systems with molecular force generation that drives complex dynamics at the supramolecular scale. We present a quantitative study of molecular motions in cells over times from milliseconds to hours. Noninvasive tracking was accomplished by ... Full text Cite

A surprising twist.

Journal Article eLife · April 2014 X-ray crystallography has revealed an unusual structural element in kinesin-5 motor proteins. ... Full text Cite

Scale-dependent nonaffine elasticity of semiflexible polymer networks

Journal Article Physical Review Letters · February 24, 2014 The cytoskeleton of eukaryotic cells provides mechanical support and governs intracellular transport. These functions rely on the complex mechanical properties of networks of semiflexible protein filaments. We study the impact of local network deformations ... Full text Cite

Kinesin-5 Kip1 is a bi-directional motor that stabilizes microtubules and tracks their plus-ends in vivo.

Journal Article Journal of cell science · September 2013 In this study, we examined the anaphase functions of the S. cerevisiae kinesin-5 homolog Kip1. We show that Kip1 is attached to the mitotic spindle midzone during late anaphase. This attachment is essential to stabilize interpolar microtubule (iMTs) plus-e ... Full text Cite

Differential interference contrast microscopy using light-emitting diode illumination in conjunction with dual optical traps.

Journal Article The Review of scientific instruments · May 2013 Differential interference contrast (DIC) microscopy is a common mode of biological light microscopy used to achieve maximal resolution and contrast with label-free, weakly absorbing specimens such as cells. Maintaining the polarization state of the illumin ... Full text Cite

A chimeric kinesin-1 head/kinesin-5 tail motor switches between diffusive and processive motility.

Journal Article Biophysical journal · January 2013 Homotetrameric kinesin-5 motors are essential for chromosome separation and assembly of the mitotic spindle. These kinesins bind between two microtubules (MTs) and slide them apart, toward the spindle poles. This process must be tightly regulated in mitosi ... Full text Cite

Neck-linker length dependence of processive Kinesin-5 motility.

Journal Article Journal of molecular biology · October 2012 Processive motility of individual molecules is essential for the function of many kinesin motors. Processivity for kinesins relies on communication between the two heads of a dimeric molecule, such that binding strictly alternates. The main communicating e ... Full text Cite

High-resolution microrheology in the pericellular matrix of prostate cancer cells.

Journal Article Journal of the Royal Society, Interface · August 2012 Many cells express a membrane-coupled external mechanical layer, the pericellular matrix (PCM), which often contains long-chain polymers. Its role and properties are not entirely known, but its functions are believed to include physical protection, mechano ... Full text Cite

Control of Directionality of Individual Kinesin-5 Motors

Conference Biophysical Journal · January 2012 Full text Cite

Endoplasmic reticulum sorting and kinesin-1 command the targeting of axonal GABAB receptors.

Journal Article PloS one · January 2012 In neuronal cells the intracellular trafficking machinery controls the availability of neurotransmitter receptors at the plasma membrane, which is a critical determinant of synaptic strength. Metabotropic γ amino-butyric acid (GABA) type B receptors (GABA( ... Full text Cite

Directionality of individual kinesin-5 Cin8 motors is modulated by loop 8, ionic strength and microtubule geometry.

Journal Article The EMBO journal · November 2011 Kinesin-5 motors fulfil essential roles in mitotic spindle morphogenesis and dynamics as slow, processive microtubule (MT) plus-end directed motors. The Saccharomyces cerevisiae kinesin-5 Cin8 was found, surprisingly, to switch directionality. Here, we hav ... Full text Cite

Directionality of the yeast Kinesin-5 Cin8 is controlled by molecular structure and salt conditions

Conference EUROPEAN BIOPHYSICS JOURNAL WITH BIOPHYSICS LETTERS · August 1, 2011 Link to item Cite

Discrete fracture patterns of virus shells reveal mechanical building blocks.

Journal Article Proceedings of the National Academy of Sciences of the United States of America · August 2011 Viral shells are self-assembled protein nanocontainers with remarkable material properties. They combine simplicity of construction with toughness and complex functionality. These properties make them interesting for bionanotechnology. To date we know litt ... Full text Cite

Control of the fast, slow and reverse gear of the yeast mitotic kinesin-5 Cin8

Conference EUROPEAN BIOPHYSICS JOURNAL WITH BIOPHYSICS LETTERS · August 1, 2011 Link to item Cite

Detecting protein conformational states in C. elegans in vivo by confocal fluorescence anisotropy

Conference EUROPEAN BIOPHYSICS JOURNAL WITH BIOPHYSICS LETTERS · August 1, 2011 Link to item Cite

Carbon nanotubes as mechanical probes of equilibrium and non-equilibrium cytoskeletal networks

Conference EUROPEAN BIOPHYSICS JOURNAL WITH BIOPHYSICS LETTERS · August 1, 2011 Link to item Cite

Non-Gaussian athermal fluctuations in active gels

Journal Article Soft Matter · May 16, 2011 Dynamic networks designed to model the cell cytoskeleton can be reconstituted from filamentous actin, the motor protein myosin and a permanent cross-linker. They are driven out of equilibrium when the molecular motors are active. This gives rise to atherma ... Full text Cite

Kinesin walks the line: single motors observed by atomic force microscopy.

Journal Article Biophysical journal · May 2011 Motor proteins of the kinesin family move actively along microtubules to transport cargo within cells. How exactly a single motor proceeds on the 13 narrow lanes or protofilaments of a microtubule has not been visualized directly, and there persists contro ... Full text Cite

Moving into the cell: single-molecule studies of molecular motors in complex environments.

Journal Article Nature reviews. Molecular cell biology · March 2011 Much has been learned in the past decades about molecular force generation. Single-molecule techniques, such as atomic force microscopy, single-molecule fluorescence microscopy and optical tweezers, have been key in resolving the mechanisms behind the powe ... Full text Cite

Neck-Linker-Length Dependence of Processive Kinesin-5 Motility

Conference BIOPHYSICAL JOURNAL · February 2, 2011 Link to item Cite

Bidirectional power stroke by ncd kinesin.

Journal Article Biophysical journal · December 2010 Optical trapping experiments reveal details of molecular motor dynamics. In noisy data, temporal structure within the power stroke of motors can be analyzed by ensemble averaging, but this obscures infrequent subcategories of events. We have here developed ... Full text Cite

The effect of monastrol on the processive motility of a dimeric kinesin-5 head/kinesin-1 stalk chimera.

Journal Article Journal of molecular biology · May 2010 Controlled activity of several kinesin motors is required for the proper assembly of the mitotic spindle. Eg5, a homotetrameric bipolar kinesin-5 from Xenopus laevis, can cross-link and slide anti-parallel microtubules apart by a motility mechanism compris ... Full text Cite

Active cellular materials.

Journal Article Current opinion in cell biology · February 2010 The materials cells are made of are strikingly different from man-made materials. Metabolism keeps cells out of equilibrium. Motor proteins and energy-consuming polymerization drive shape changes and motion. In contrast to macroscopic machines, though, the ... Full text Cite

Stiff-Filament Microrheology

Conference BIOPHYSICAL JOURNAL · January 1, 2010 Link to item Cite

Dissociation kinetics of the GroEL-gp31 chaperonin complex studied with Förster resonance energy transfer.

Journal Article Biochemistry · December 2009 Propagation of bacteriophage T4 in its host Escherichia coli involves the folding of the major capsid protein gp23, which is facilitated by a hybrid chaperone complex consisting of the bacterial chaperonin GroEL and the phage-encoded co-chaperonin, gp31. I ... Full text Cite

Biochemistry. Friction in motor proteins.

Journal Article Science (New York, N.Y.) · August 2009 Full text Cite

Viscoelastic response of a model endothelial glycocalyx.

Journal Article Physical biology · July 2009 Many cells cover themselves with a multifunctional polymer coat, the pericellular matrix (PCM), to mediate mechanical interactions with the environment. A particular PCM, the endothelial glycocalyx (EG), is formed by vascular endothelial cells at their lum ... Full text Cite

High-resolution probing of cellular force transmission.

Journal Article Physical review letters · April 2009 Cells actively probe mechanical properties of their environment by exerting internally generated forces. The response they encounter profoundly affects their behavior. Here we measure in a simple geometry the forces a cell exerts suspended by two optical t ... Full text Cite

Leveraging single protein polymers to measure flexural rigidity.

Journal Article The journal of physical chemistry. B · March 2009 The micrometer-scale length of some protein polymers allows them to be mechanically manipulated in single-molecule experiments. This provides a direct way to measure persistence length. We have used a double optical trap to elastically deform single microt ... Full text Cite

Deconstructing Viral Shells To Understand Its Building Blocks

Conference Biophysical Journal · February 2009 Full text Cite

Response of Viral Shells under Nano-Indentation

Conference Biophysical Journal · February 2009 Full text Cite

Microrheology of the pericellular matrix

Conference Biophysical Journal · February 2009 Full text Cite

High-bandwidth viscoelastic properties of aging colloidal glasses and gels.

Journal Article Physical review. E, Statistical, nonlinear, and soft matter physics · December 2008 We report measurements of the frequency-dependent shear moduli of aging colloidal systems that evolve from a purely low-viscosity liquid to a predominantly elastic glass or gel. Using microrheology, we measure the local complex shear modulus G;{*}(omega) o ... Full text Cite

The homotetrameric kinesin-5 KLP61F preferentially crosslinks microtubules into antiparallel orientations.

Journal Article Current biology : CB · December 2008 The segregation of genetic material during mitosis is coordinated by the mitotic spindle, whose action depends upon the polarity patterns of its microtubules (MTs). Homotetrameric mitotic kinesin-5 motors can crosslink and slide adjacent spindle MTs, but i ... Full text Cite

Laser trapping and laser interferometry for high-bandwidth micromechanical probing of biomaterials

Conference 2008 Asia Optical Fiber Communication and Optoelectronic Exposition and Conference, AOE 2008 · December 1, 2008 We present techniques based on optical trapping of micron-sized particles as probes and detecting their motion with sub-nanometer accuracy at 100 kHz bandwidth that can measure viscoelastic properties of biomaterials and cells on micrometer scales. © Optic ... Cite

Microtubule-driven multimerization recruits ase1p onto overlapping microtubules.

Journal Article Current biology : CB · November 2008 Microtubule (MT) crosslinking proteins of the ase1p/PRC1/Map65 family play a major role in the construction of MT networks such as the mitotic spindle. Most homologs in this family have been shown to localize with a remarkable specificity to sets of MTs th ... Full text Cite

Active and passive microrheology in equilibrium and nonequilibrium systems

Journal Article Macromolecules · October 14, 2008 Quantitatively measuring the mechanical properties of soft matter over a wide range of length and time scales, especially if a sample is as complex as typical biological materials, remains challenging. Living cells present a further complication because fo ... Full text Cite

Effective temperatures from the fluctuation-dissipation measurements in soft glassy materials

Journal Article EPL · October 1, 2008 We have investigated the validity of the fluctuation-dissipation theorem (FDT) and the applicability of the concept of effective temperature in a number of non-equilibrium soft glassy materials. Using a combination of passive and active microrheology to me ... Full text Cite

Microrheology of hyaluronan solutions: implications for the endothelial glycocalyx.

Journal Article Biomacromolecules · September 2008 The endothelial glycocalyx (EG) is a complex biopolymer network produced by vascular endothelial cells that forms a layer with multiple functions at the luminal side of blood vessels. The EG acts as an anti-adhesive protection layer, as a molecular sieve, ... Full text Cite

Microtubule cross-linking triggers the directional motility of kinesin-5.

Journal Article The Journal of cell biology · August 2008 Although assembly of the mitotic spindle is known to be a precisely controlled process, regulation of the key motor proteins involved remains poorly understood. In eukaryotes, homotetrameric kinesin-5 motors are required for bipolar spindle formation. Eg5, ... Full text Cite

Combined macro- and microrheometer for use with Langmuir monolayers.

Journal Article The Review of scientific instruments · June 2008 A Langmuir monolayer trough that is equipped for simultaneous microrheology and standard rheology measurements has been constructed. The central elements are the trough itself with a full range of optical tools accessing the air-water interface from below ... Full text Cite

Short-time inertial response of viscoelastic fluids measured with Brownian motion and with active probes.

Journal Article Physical review. E, Statistical, nonlinear, and soft matter physics · June 2008 We have directly observed short-time stress propagation in viscoelastic fluids using two optically trapped particles and a fast interferometric particle-tracking technique. We have done this both by recording correlations in the thermal motion of the parti ... Full text Cite

Twin optical traps for two-particle cross-correlation measurements: eliminating cross-talk.

Journal Article The Review of scientific instruments · April 2008 The correlated motions of two micron-sized particles reflect the (micro-) rheological properties of a fluid and can be conveniently detected using two optical traps in combination with interferometric displacement detection. When the correlations become sm ... Full text Cite

Round versus flat: bone cell morphology, elasticity, and mechanosensing.

Journal Article Journal of biomechanics · January 2008 There is increasing evidence that cell function and mechanical properties are closely related to morphology. However, most in vitro studies investigate flat adherent cells, which might not reflect physiological geometries in vivo. Osteocytes, the mechanose ... Full text Cite

Laser trapping and laser interferometry for high-bandwidth micromechanical probing of biomaterials

Conference Optics InfoBase Conference Papers · January 1, 2008 We present techniques based on optical trapping of micron-sized particles as probes and detecting their motion with sub-nanometer accuracy at 100 kHz bandwidth that can measure viscoelastic properties of biomaterials and cells on micrometer scales. © Optic ... Cite

Laser trapping and laser interferometry for high-bandwidth micromechanical probing of biomaterials

Conference Optics InfoBase Conference Papers · January 1, 2008 We present techniques based on optical trapping of micron-sized particles as probes and detecting their motion with sub-nanometer accuracy at 100 kHz bandwidth that can measure viscoelastic properties of biomaterials and cells on micrometer scales. © Optic ... Full text Cite

Linear and nonlinear laser-trapping microrheology

Conference Proceedings of SPIE - The International Society for Optical Engineering · December 1, 2007 We have developed a high-bandwidth technique for active 2-particle microrheology (AMR) with which we can probe linear and nonlinear responses of soft materials. Micron-sized colloidal probe particles are driven by an oscillating optical trap, and the resul ... Full text Cite

Load-dependent release limits the processive stepping of the tetrameric Eg5 motor.

Journal Article European biophysics journal : EBJ · July 2007 Tetrameric motor proteins of the Kinesin-5 family are essential for eukaryotic cell division. The microscopic mechanism by which Eg5, the vertebrate Kinesin-5, drives bipolar mitotic spindle formation remains unknown. Here we show in optical trapping exper ... Full text Cite

Tau protein binding forms a 1 nm thick layer along protofilaments without affecting the radial elasticity of microtubules.

Journal Article Journal of structural biology · June 2007 Tau is one of the most abundant microtubule-associated proteins involved in kinetic stabilization and bundling of axonal microtubules. Although intense research has revealed much about tau function and its involvement in Alzheimer's disease during the past ... Full text Cite

Fluctuation-dissipation theorem in an aging colloidal glass.

Journal Article Physical review letters · March 2007 We provide a direct experimental test of the fluctuation-dissipation theorem (FDT) in an aging colloidal glass. The use of combined active and passive microrheology allows us to independently measure both the correlation and response functions in this none ... Full text Cite

Mechanical failure of viral shells

Conference BIOPHYSICAL JOURNAL · January 1, 2007 Link to item Cite

Nonequilibrium mechanics of active cytoskeletal networks.

Journal Article Science (New York, N.Y.) · January 2007 Cells both actively generate and sensitively react to forces through their mechanical framework, the cytoskeleton, which is a nonequilibrium composite material including polymers and motor proteins. We measured the dynamics and mechanical properties of a s ... Full text Cite

The mechanosensitive part of a single osteocyte, cell body or cell process?

Conference CALCIFIED TISSUE INTERNATIONAL · January 1, 2007 Link to item Cite

Viscoelasticity and force traction of bone cells in 3-dimensional morphology

Conference CALCIFIED TISSUE INTERNATIONAL · January 1, 2007 Link to item Cite

Failure of viral shells.

Journal Article Physical review letters · December 2006 We report a combined theoretical and experimental study of the structural failure of viral shells under mechanical stress. We find that discontinuities in the force-indentation curve associated with failure should appear when the so-called Föppl-von Kármán ... Full text Cite

Bio imaging of intracellular NO production in single bone cells after mechanical stimulation.

Journal Article Journal of bone and mineral research : the official journal of the American Society for Bone and Mineral Research · November 2006 UnlabelledWe show the intracellular upregulation of NO production after mechanical stimulation, an essential chemical signal in bone remodeling. This is done in real time using the fluorescent chromophore DAR-4M AM. Differences in cellular respons ... Full text Cite

Allosteric inhibition of kinesin-5 modulates its processive directional motility.

Journal Article Nature chemical biology · September 2006 Small-molecule inhibitors of kinesin-5 (refs. 1-3), a protein essential for eukaryotic cell division, represent alternatives to antimitotic agents that target tubulin. While tubulin is needed for multiple intracellular processes, the known functions of kin ... Full text Cite

Elastic response, buckling, and instability of microtubules under radial indentation.

Journal Article Biophysical journal · August 2006 We tested the mechanical properties of single microtubules by lateral indentation with the tip of an atomic force microscope. Indentations up to approximately 3.6 nm, i.e., 15% of the microtubule diameter, resulted in an approximately linear elastic respon ... Full text Cite

Power spectrum analysis for optical tweezers. II: Laser wavelength dependence of parasitic filtering, and how to achieve high bandwidth

Journal Article Review of Scientific Instruments · July 11, 2006 In a typical optical tweezers detection system, the position of a trapped object is determined from laser light impinging on a quadrant photodiode. When the laser is infrared and the photodiode is of silicon, they can act together as an unintended low-pass ... Full text Cite

Correlated fluctuations of microparticles in viscoelastic solutions: quantitative measurement of material properties by microrheology in the presence of optical traps.

Journal Article Physical review. E, Statistical, nonlinear, and soft matter physics · June 2006 The Brownian motions of microscopic particles in viscous or viscoelastic fluids can be used to measure rheological properties. This is the basis of recently developed one- and two-particle microrheology techniques. For increased temporal and spatial resolu ... Full text Cite

Nanoindentation studies of full and empty viral capsids and the effects of capsid protein mutations on elasticity and strength.

Journal Article Proceedings of the National Academy of Sciences of the United States of America · April 2006 The elastic properties of capsids of the cowpea chlorotic mottle virus have been examined at pH 4.8 by nanoindentation measurements with an atomic force microscope. Studies have been carried out on WT capsids, both empty and containing the RNA genome, and ... Full text Cite

High-bandwidth one-and two-particle microrheology in solutions of wormlike micelles

Conference Rheologica Acta · April 1, 2006 We have developed a large-bandwidth two-particle microrheology technique to measure loss and storage moduli of viscoelastic materials from 0.1 Hz to about 100 kHz using laser trapping and interferometry. We found that quantitative agreement between one- an ... Full text Cite

High-frequency stress relaxation in semiflexible polymer solutions and networks.

Journal Article Physical review letters · April 2006 We measure the linear viscoelasticity of sterically entangled and chemically cross-linked networks of actin filaments over more than five decades of frequency. The high-frequency response reveals rich dynamics unique to semiflexible polymers, including a p ... Full text Cite

Structural and mechanical study of a self-assembling protein nanotube.

Journal Article Nano letters · April 2006 We report a structural characterization of self-assembling nanostructures. Using atomic force microscopy (AFM), we discovered that partially hydrolyzed alpha-lactalbumin organizes in a 10-start helix forming tubes with diameters of only 21 nm. We probed th ... Full text Cite

Optical trap stiffness in the presence and absence of spherical aberrations.

Journal Article Applied optics · March 2006 Optical traps are commonly constructed with high-numerical-aperture objectives. Oil-immersion objectives suffer from spherical aberrations when used for imaging in aqueous solutions. The effect of spherical aberrations on trapping strength has been modeled ... Full text Cite

Calibrating bead displacements in optical tweezers using acousto-optic deflectors

Journal Article Review of Scientific Instruments · February 6, 2006 Displacements of optically trapped particles are often recorded using back-focal-plane interferometry. In order to calibrate the detector signals to displacements of the trapped object, several approaches are available. One often relies either on scanning ... Full text Cite

A practical guide to optical tweezers

Chapter · January 1, 2006 This chapter provides a brief review of the physical principles behind the method of trapping microscopic dielectric particles by focused laser light (optical tweezers) and then discusses some of the practical possibilities and limitations encountered when ... Cite

Rapid chiral assembly of rigid DNA building blocks for molecular nanofabrication.

Journal Article Science (New York, N.Y.) · December 2005 Practical components for three-dimensional molecular nanofabrication must be simple to produce, stereopure, rigid, and adaptable. We report a family of DNA tetrahedra, less than 10 nanometers on a side, that can self-assemble in seconds with near-quantitat ... Full text Cite

Short-time inertial response of viscoelastic fluids: observation of vortex propagation.

Journal Article Physical review letters · November 2005 We probe the response of viscous and viscoelastic fluids on micrometer and microsecond length and time scales using two optically trapped beads. In this way we resolve the flow field, which exhibits clear effects of fluid inertia. Specifically, we resolve ... Full text Cite

Comparing macrorheology and one- and two-point microrheology in wormlike micelle solutions

Journal Article Macromolecules · October 18, 2005 We present here a comparison between three rheological techniques to verify a recently developed optical microrheology technique. As a model viscoelastic fluid we have used wormlike micelle solutions which are well-characterized Maxwell fluids. Using the s ... Full text Cite

High-frequency microrheology of wormlike micelles.

Journal Article Physical review. E, Statistical, nonlinear, and soft matter physics · July 2005 We have measured the frequency-dependent shear modulus of entangled solutions of wormlike micelles by high-frequency microrheology and have compared the results with those from macrorheology experiments done on the same samples. Using optical microrheology ... Full text Cite

The bipolar mitotic kinesin Eg5 moves on both microtubules that it crosslinks.

Journal Article Nature · May 2005 During cell division, mitotic spindles are assembled by microtubule-based motor proteins. The bipolar organization of spindles is essential for proper segregation of chromosomes, and requires plus-end-directed homotetrameric motor proteins of the widely co ... Full text Cite

Squeezing self-assembled nanocontainers: AFM indentation studies of viral capsids

Conference ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY · March 13, 2005 Link to item Cite

Squeezing CCMV: AFM nanoindentation studies of viruses

Conference BIOPHYSICAL JOURNAL · January 1, 2005 Link to item Cite

The mitotic motor Eg5 slides anti-parallel microtubules apart

Conference BIOPHYSICAL JOURNAL · January 1, 2005 Link to item Cite

Mapping vortex diffusion in viscous and viscoelastic fluids

Conference BIOPHYSICAL JOURNAL · January 1, 2005 Link to item Cite

Parasitic filtering in position detection systems for optical tweezers

Conference Proceedings of SPIE - The International Society for Optical Engineering · December 1, 2004 In a typical position detection system for optical tweezers, laser light impinges on a quadrant photodiode, and the signal from the four quadrants of the diode is used to determine the position of a trapped object. A widely used position detection system c ... Full text Cite

Minimizing photobleaching in experiments combining optical tweezers and single-molecule fluorescence

Conference ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY · August 22, 2004 Link to item Cite

Microrheology of solutions of semiflexible biopolymer filaments using laser tweezers interferometry.

Journal Article Physical review. E, Statistical, nonlinear, and soft matter physics · August 2004 Semiflexible polymers are of great biological importance in determining the mechanical properties of cells. Techniques collectively known as microrheology have recently been developed to measure the viscoelastic properties of solutions of submicroliter vol ... Full text Cite

Resolving the molecular structure of microtubules under physiological conditions with scanning force microscopy.

Journal Article European biophysics journal : EBJ · August 2004 We have imaged microtubules, essential structural elements of the cytoskeleton in eukaryotic cells, in physiological conditions by scanning force microscopy. We have achieved molecular resolution without the use of cross-linking and chemical fixation metho ... Full text Cite

Bacteriophage capsids: tough nanoshells with complex elastic properties.

Journal Article Proceedings of the National Academy of Sciences of the United States of America · May 2004 The shell of bacteriophages protects the viral DNA during host-to-host transfer and serves as a high-pressure container storing energy for DNA injection into a host bacterium. Here, we probe the mechanical properties of nanometer-sized bacteriophage phi 29 ... Full text Cite

Combining optical trapping and single-molecule fluorescence spectroscopy: enhanced photobleaching of fluorophores.

Journal Article The journal of physical chemistry. B · May 2004 To obtain high-resolution information on position or conformation of a molecule and at the same time apply forces to it, one can combine optical trapping with single-molecule fluorescence microscopy. The technical challenge in such an experiment is to disc ... Full text Cite

Deformation and collapse of microtubules on the nanometer scale.

Journal Article Physical review letters · August 2003 We probe the local mechanical properties of microtubules at the nanometer scale by radial indentation with a scanning force microscope tip. We find a linear elastic regime that can be described by both thin-shell theory and finite element methods, in which ... Full text Cite

Extending the bandwidth of optical-tweezers interferometry

Journal Article Review of Scientific Instruments · July 1, 2003 The extension of the bandwidth of optical-tweezers interferometry was discussed. It was found that the detection bandwidth was extended to at least 100 KHz, either by using wavelengths below 850 nm or by using different detectors at longer wavelengths. The ... Full text Cite

Laser-induced heating in optical traps.

Journal Article Biophysical journal · February 2003 In an optical tweezers experiment intense laser light is tightly focused to intensities of MW/cm(2) in order to apply forces to submicron particles or to measure mechanical properties of macromolecules. It is important to quantify potentially harmful or mi ... Full text Cite

Observation of microtubules with scanning force microscopy in liquid

Conference Nanotechnology · February 1, 2003 We present the application of scanning force microscopy using the jumping mode to investigate microtubules adsorbed to glass in air and in liquid. To fix the microtubules the glass surfaces were silanized with aminopropyl-triethoxy-silane. The observed str ... Full text Cite

Optical trapping near resonance absorption.

Journal Article Applied optics · April 2002 Expressions for radiation-induced forces are presented for the case of a Rayleigh particle near the focus of a Gaussian laser beam at near-resonant conditions. Classical electromagnetic theory was used to obtain the dependence of the scattering and gradien ... Full text Cite

Resonance effects in optical trapping

Conference BIOPHYSICAL JOURNAL · January 1, 2002 Link to item Cite

Cooperative behavior of molecular motors.

Journal Article Journal of muscle research and cell motility · January 2002 Both experimental evidence and theoretical models for collective effects in the working mechanism of molecular motors are reviewed at three different levels, namely: (i) interaction between the two heads of double-headed motors, particularly in processive ... Full text Cite

One- and two-particle microrheology in entangled solutions of fd virus

Journal Article Materials Research Society Symposium - Proceedings · January 1, 2002 We have used one- and two-particle microrheology, employing μm-sized beads and laser interferometric displacement detection, to study the rheological properties of entangled solutions of the filamentous fd virus. Thermal fluctuations of the embedded probes ... Cite

Laser tweezing near resonance absorption

Conference Proceedings of SPIE - The International Society for Optical Engineering · December 1, 2001 Expressions for radiation-induced forces are presented for the case of a Rayleigh particle at the focus of a Gaussian laser beam. Classical electromagnetic theory was used to obtain the dependence of the scattering and gradient forces on the incident laser ... Full text Cite

Instability of myelin tubes under dehydration: deswelling of layered cylindrical structures.

Journal Article Physical review. E, Statistical, nonlinear, and soft matter physics · November 2001 We report experimental observations of an undulational instability of myelin figures. Motivated by this, we examine theoretically the deformation and possible instability of concentric, cylindrical, multilamellar membrane structures. Under conditions of os ... Full text Cite

Working strokes by single molecules of the kinesin-related microtubule motor ncd.

Journal Article Nature cell biology · October 2000 The ncd protein is a dimeric, ATP-powered motor that belongs to the kinesin family of microtubule motor proteins. Here we resolve single mechanochemical cycles of recombinant, dimeric, full-length ncd, using optical-tweezers-based instrumentation and a thr ... Full text Cite

Imaging microtubules and kinesin decorated microtubules using tapping mode atomic force microscopy in fluids.

Journal Article European biophysics journal : EBJ · January 2000 The atomic force microscope has been used to investigate microtubules and kinesin decorated microtubules in aqueous solution adsorbed onto a solid substrate. The netto negatively charged microtubules did not adsorb to negatively charged solid surfaces but ... Full text Cite

Microrheology

Journal Article Current Opinion in Colloid and Interface Science · August 1, 1999 Several complementary techniques have been developed in recent years that make it possible to measure viscoelastic properties of soft materials on micrometer scales. Such methods provide new prospects for the characterization of local inhomogeneities in ma ... Full text Cite

Three-bead assay for kinesin motors.

Conference BIOPHYSICAL JOURNAL · January 1, 1999 Link to item Cite

Viscoelasticity and its microscopic characterization in semiflexible biopolymer solutions

Conference Materials Research Society Symposium - Proceedings · December 1, 1998 Plant and animal cells contain a complex polymeric network known as the cytoskeleton. A principal component of this is the actin cortex, a gel-like network of F-actin protein filaments. Recently, solutions of reconstituted F-actin have provided in vitro mo ... Cite

Model for dynamic shear modulus of semiflexible polymer solutions

Conference Materials Research Society Symposium - Proceedings · December 1, 1998 We discuss a dynamical model for the frequency-dependent shear modulus of an entangled solution of semiflexible polymers, based on longitudinal fluctuations in filaments between entanglement points or crosslinks. The goal is to explain non-Rouse, power-law ... Cite

High resolution two-dimensional detection of ncd motility with optical tweezers

Conference Materials Research Society Symposium - Proceedings · December 1, 1998 The ATP-dependent motility of the kinesin-related non claret disjunctional (ncd) mechanoenzyme was observed in an in vitro bead motility assay using optical tweezers in combination with a new two-dimensional displacement detection method. The detection tec ... Cite

Microscopic dynamics of proteins probed with optical tweezers.

Conference ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY · August 23, 1998 Link to item Cite

Evidence for non-processive ncd motility in vitro.

Conference BIOPHYSICAL JOURNAL · February 1, 1998 Link to item Cite

Back-focal-plane detection of force and motion in optical traps

Conference BIOPHYSICAL JOURNAL · February 1, 1998 Link to item Cite

Two-dimensional tracking of ncd motility by back focal plane interferometry.

Journal Article Biophysical journal · February 1998 A technique for detecting the displacement of micron-sized optically trapped probes using far-field interference is introduced, theoretically explained, and used to study the motility of the ncd motor protein. Bead motions in the focal plane relative to th ... Full text Cite

Protein structural changes studied by near-field spectroscopy.

Conference BIOPHYSICAL JOURNAL · February 1, 1998 Link to item Cite

Thermal noise limitations on micromechanical experiments

Journal Article European Biophysics Journal · January 1, 1998 Thermal motions of microscopic probes limit the possibilities of experiments that are designed to resolve single-macromolecule dynamics in aqueous conditions. We investigate theoretical strategies for maximizing signal-to-noise ratios or resolution in typi ... Full text Cite

Interference model for back-focal-plane displacement detection in optical tweezers.

Journal Article Optics letters · January 1998 The lateral position of an optically trapped object in a microscope can be monitored with a quadrant photodiode to within nanometers or better by measurement of intensity shifts in the back focal plane of the lens that is collimating the outgoing laser lig ... Full text Cite

Highly processive motility is not a general feature of the kinesins.

Journal Article European biophysics journal : EBJ · January 1998 Evidence is presented that the kinesin-related ncd protein is not as processive as kinesin. In low surface density motility experiments, a dimeric ncd fusion protein behaved mechanistically more similar to non-processive myosins than to the highly processi ... Full text Cite

Determining microscopic viscoelasticity in flexible and semiflexible polymer networks from thermal fluctuations

Journal Article Macromolecules · December 15, 1997 We have developed a new technique to measure viscoelasticity in soft materials such as entangled polymer solutions, by monitoring thermal fluctuations of embedded probe particles using laser interferometry in a microscope. Interferometry allows us to obtai ... Full text Cite

Microrheology in actin gels: Experiment and theory.

Conference BIOPHYSICAL JOURNAL · February 1, 1997 Link to item Cite

Microscopic viscoelasticity: Shear moduli of soft materials determined from thermal fluctuations

Journal Article Physical Review Letters · January 1, 1997 We describe a high-resolution, high-bandwidth technique for determining the local viscoelasticity of soft materials such as polymer gels. Loss and storage shear moduli are determined from the power spectra of thermal fluctuations of embedded micron-sized p ... Full text Cite

Local viscoelasticity of biopolymer solutions

Conference Materials Research Society Symposium - Proceedings · January 1, 1997 We describe a new, high-resolution technique for determining the local viscoelastic response of polymer gels on a micrometer scale. This is done by monitoring thermal fluctuations of embedded probe particles. We derive the relationship between the amplitud ... Cite

Protein tracking and detection of protein motion using atomic force microscopy.

Journal Article Biophysical journal · May 1996 Height fluctuations over three different proteins, immunoglobulin G, urease, and microtubules, have been measured using an atomic force microscope (AFM) operating in fluid tapping mode. This was achieved by using a protein-tracking system, where the AFM ti ... Full text Cite

Microscopic approaches to dynamics and structure of biological motors

Journal Article Current Opinion in Solid State and Materials Science · January 1, 1996 It has become increasingly clear that the interior of biological cells, the cytoplasm, is intricately organized and ordered by complex networks of protein polymers and membranes. Transport processes, as well as large-scale mechanical processes, are driven ... Full text Cite

Imaging Globular and Filamentous Proteins in Physiological Buffer Solutions with Tapping Mode Atomic Force Microscopy

Journal Article Langmuir · September 1, 1995 Two different types of proteins were imaged in buffer solution with tapping mode atomic force microscopy (AFM) in liquids: the globular proteins lysozyme and monomeric actin (G-actin); the filamentous proteins actin (F-actin) and microtubules. To calibrate ... Full text Cite

Imaging adhesion forces on proteins with the atomic force microscope

Conference Proceedings of SPIE - The International Society for Optical Engineering · January 1, 1995 We investigated the adhesion forces between single protein molecules and the silicon-nitride tip of an atomic force microscope. Force curves were taken on a sample with single adsorbed proteins while the tip was raster scanned laterally. Out of these force ... Cite

Imaging microtubules in buffer solution using tapping mode atomic force microscopy

Conference Proceedings of SPIE - The International Society for Optical Engineering · January 1, 1995 Taxol stabilized microtubules were imaged in their native state in buffer solution without any fixation by an atomic force microscope (AFM) operated in tapping mode in liquids. Glass cover slips were derivatized with a positively charged silane to adsorb t ... Cite

DIRECT OBSERVATION OF KINESIN STEPS

Conference BIOPHYSICAL JOURNAL · February 1, 1994 Link to item Cite

Direct observation of kinesin stepping by optical trapping interferometry.

Journal Article Nature · October 1993 Do biological motors move with regular steps? To address this question, we constructed instrumentation with the spatial and temporal sensitivity to resolve movement on a molecular scale. We deposited silica beads carrying single molecules of the motor prot ... Full text Cite

Existence of a flat phase in red cell membrane skeletons.

Journal Article Science (New York, N.Y.) · February 1993 Biomolecular membranes display rich statistical mechanical behavior. They are classified as liquid in the absence of shear elasticity in the plane of the membrane and tethered (solid) when the neighboring molecules or subunits are connected and the membran ... Full text Cite

Conformation and elasticity of the isolated red blood cell membrane skeleton.

Journal Article Biophysical journal · September 1992 We studied the structure and elasticity of membrane skeletons from human red blood cells (RBCs) during and after extraction of RBC ghosts with nonionic detergent. Optical tweezers were used to suspend individual cells inside a flow chamber, away from all s ... Full text Cite

Absolute quantities and equilibrium kinetics of macromolecular adsorption measured by fluorescence photobleaching in total internal reflection

Journal Article Journal of Colloid And Interface Science · October 1, 1990 A combination of total internal reflection fluorescence and fluorescence recovery after photobleaching was used to measure the adsorption of 7-chloro-4-nitrobenz-2-oxa-1,3-diazole (NBD) labeled bovine serum albumin and NBD labeled lysozyme to plain quartz ... Full text Cite

Multilayer adsorption of lysozyme on a hydrophobic substrate.

Journal Article Biophysical journal · March 1990 Macromolecular adsorption is known to occur as a complex process, often in a series of steps. Several models are discussed in the literature which describe the microscopic structure of the adsorbate. In the present study we investigated the adsorption of h ... Full text Cite

Chain Dynamics, Mesh Size, and Diffusive Transport in Networks of Polymerized Actin: A Quasielastic Light Scattering and Microfluorescence Study

Journal Article Macromolecules · September 1, 1989 Dynamical (chain excitations, reptational diffusion) and structural (mesh size) properties of semidilute solutions (gels) of polymerized actin and their concentration dependencies were studied by quasielastic light scattering (QELS) and microfluorescence e ... Full text Cite

Kinetics of Symmetric and Asymmetric Phospholipid Transfer between Small Sonicated Vesicles Studied by High-Sensitivity Differential Scanning Calorimetry, NMR, Electron Microscopy, and Dynamic Light Scattering

Journal Article Biochemistry · August 1, 1988 The transfer of Laphosphatidylcholines of different acyl chain length between small unilamellar vesicles via the aqueous phase was studied by using high-sensitivity differential scanning calorimetry (hs-DSC),1H NMR, dynamic light scattering, and freeze-fra ... Full text Cite