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147 results on '"Wei, Ming-Tzo"'

2. Non-Stokes Drag Coefficient in Single-Particle Electrophoresis: New Insights on a Classical Problem

Author

Liao, Maijia, Wei, Ming-Tzo, Xu, Shixin, Ou-Yang, H. Daniel, and Sheng, Ping

Subjects
Condensed Matter - Soft Condensed Matter
Abstract

We measured the intrinsic drag coefficient of a single charged particle by optically trapping the particle and applying an alternating electric field, and found it to be markedly different from that of the Stokes drag.

Published
2019
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4. Composition-dependent thermodynamics of intracellular phase separation

Author

Riback, Joshua A., Zhu, Lian, Ferrolino, Mylene C., Tolbert, Michele, Mitrea, Diana M., Sanders, David W., and Wei, Ming-Tzo

Subjects
Cell separation -- Methods -- Analysis -- Thermal properties, Thermodynamics -- Analysis -- Thermal properties -- Methods, Environmental issues, Science and technology, Zoology and wildlife conservation
Abstract

Intracellular bodies such as nucleoli, Cajal bodies and various signalling assemblies represent membraneless organelles, or condensates, that form via liquid-liquid phase separation (LLPS).sup.1,2. Biomolecular interactions--particularly homotypic interactions mediated by self-associating intrinsically disordered protein regions--are thought to underlie the thermodynamic driving forces for LLPS, forming condensates that can facilitate the assembly and processing of biochemically active complexes, such as ribosomal subunits within the nucleolus. Simplified model systems.sup.3-6 have led to the concept that a single fixed saturation concentration is a defining feature of endogenous LLPS.sup.7-9, and has been suggested as a mechanism for intracellular concentration buffering.sup.2,7,8,10. However, the assumption of a fixed saturation concentration remains largely untested within living cells, in which the richly multicomponent nature of condensates could complicate this simple picture. Here we show that heterotypic multicomponent interactions dominate endogenous LLPS, and give rise to nucleoli and other condensates that do not exhibit a fixed saturation concentration. As the concentration of individual components is varied, their partition coefficients change in a manner that can be used to determine the thermodynamic free energies that underlie LLPS. We find that heterotypic interactions among protein and RNA components stabilize various archetypal intracellular condensates--including the nucleolus, Cajal bodies, stress granules and P-bodies--implying that the composition of condensates is finely tuned by the thermodynamics of the underlying biomolecular interaction network. In the context of RNA-processing condensates such as the nucleolus, this manifests in the selective exclusion of fully assembled ribonucleoprotein complexes, providing a thermodynamic basis for vectorial ribosomal RNA flux out of the nucleolus. This methodology is conceptually straightforward and readily implemented, and can be broadly used to extract thermodynamic parameters from microscopy images. These approaches pave the way for a deeper understanding of the thermodynamics of multicomponent intracellular phase behaviour and its interplay with the nonequilibrium activity that is characteristic of endogenous condensates. Heterotypic multicomponent interactions are shown to dominate the liquid-liquid phase separation that enables the formation of intracellular condensates., Author(s): Joshua A. Riback [sup.1] , Lian Zhu [sup.1] , Mylene C. Ferrolino [sup.2] , Michele Tolbert [sup.2] , Diana M. Mitrea [sup.2] [sup.5] , David W. Sanders [sup.1] , [...]

Published
2020
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11. Complex Fluids: Probing Mechanical Properties of Biological Systems with Optical Tweezers

Author

Ou-Yang, H. Daniel and Wei, Ming-Tzo

Subjects
Chemistry
Abstract

Byline: H. Daniel Ou-Yang, Department of Physics and Bioengineering University, Bethlehem, Pennsylvania 18015; email: hdo0@lehigh.edu, Department of Bioengineering, Lehigh University, Bethlehem, Pennsylvania 18015; email: miw206@lehigh.edu; Ming-Tzo Wei, Department of Bioengineering, Lehigh University, Bethlehem, Pennsylvania 18015; email: miw206@lehigh.edu Keywords: microrheology, viscoelasticity, nonequilibrium thermodynamics, motor proteins, DNA, actin filaments, focal adhesion complexes, cytoskeleton Abstract The mechanical properties of cells are crucial for cell sensing and reaction to mechanical environments. This review describes the basic principles of optical tweezers and their use as force sensors for studying the mechanical properties of biological systems. It covers experiments of four groups of biological systems arranged by increasing complexity: (a) packaging DNA into viral capsids by bacteriophage portal motors and the dynamical stiffness of DNA upon protein binding, (b) actin-coated giant vesicles and the myosin-II embedded actin polymer network, (c) suspension cells, and (d) adhesion cells. These examples demonstrate how optical tweezers have been used to improve the understanding of the mechanical properties of biological systems at subcellular and molecular levels.

Published
2010

13. Competing Protein-RNA Interaction Networks Control Multiphase Intracellular Organization

Author

Sanders, David W., primary, Kedersha, Nancy, additional, Lee, Daniel S.W., additional, Strom, Amy R., additional, Drake, Victoria, additional, Riback, Joshua A., additional, Bracha, Dan, additional, Eeftens, Jorine M., additional, Iwanicki, Allana, additional, Wang, Alicia, additional, Wei, Ming-Tzo, additional, Whitney, Gena, additional, Lyons, Shawn M., additional, Anderson, Paul, additional, Jacobs, William M., additional, Ivanov, Pavel, additional, and Brangwynne, Clifford P., additional

Published
2020
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18. Regulating substrate mechanics to achieve odontogenic differentiation for dental pulp stem cells on TiO2 filled and unfilled polyisoprene

Author

Chuang, Ya-Chen, primary, Yu, Yingjie, additional, Wei, Ming-Tzo, additional, Chang, Chung-Chueh, additional, Ricotta, Vincent, additional, Feng, Kuan-Che, additional, Wang, Likun, additional, Bherwani, Aneel K., additional, Ou-Yang, H. Daniel, additional, Simon, Marcia, additional, Zhang, Liudi, additional, and Rafailovich, Miriam, additional

Published
2019
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34. Transverse Force Profiles of Individual Dielectric Particles in an Optical Trap

Author

Wei, Ming Tzo, Ng, Tsz Fai Jack, Chan, Che Ting, Chiou, Arthur, Ou-Yang, H. Daniel, Wei, Ming Tzo, Ng, Tsz Fai Jack, Chan, Che Ting, Chiou, Arthur, and Ou-Yang, H. Daniel

Abstract

The transverse force profile of a particle in an optical trap is important for the designs of optical trapping-based force transducers. We mapped these force profiles for micron-size polystyrene beads using a pair of overlapping optical traps produced by two highly focused Gaussian beams with unequal intensity; the stronger trap serves as a force transducer to measure the force of the weaker trap in both linear and nonlinear regimes. For particles with size smaller or comparable to the laser wavelength, the force profiles follow closely the gradient of the Gaussian profile, but as the particle size increases, the force profiles deviate from the shape of the gradient of Gaussian for the distance beyond the position of the maximum force. The distance from the center of the trap to the position of the maximum trapping force was found to increase linearly with the particle size. The experimental results are in good agreements with our theoretical model, based on a combination of the Mie theory, vector Debye integral, and Maxwell stress tensor; except that the experimental particle-size dependence of the maximum trapping forces was found to be weaker than that predicted by the theory. © 2012 SPIE.

Published
2012

35. Measurement of Optical Binding Force Between Two Colloidal Particles

Author

Wei, Ming Tzo, Ng, Jack, Chan, Che Ting, Ou-Yang, H. Daniel, Wei, Ming Tzo, Ng, Jack, Chan, Che Ting, and Ou-Yang, H. Daniel

Abstract

Optical binding has been proposed to be responsible for the cluster formation of micron size dielectric spheres in coherent light fields. However, a direct measurement of the forces involved in binding is missing. We report an experimental study of optical binding forces between two optically trapped dielectric spheres. Results for optical forces are presented as a function of three parameters: inter particle separation, particle size, and respective polarizations. A comprehensive calculation based on the generalized Mie scattering theory for the experiment has also been conducted. This paper will present a comparison between experimental and theoretical results. © 2009 SPIE.

Published
2009

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