Ben O'Shaughnessy

Bio: Ben O'Shaughnessy is an academic researcher from Columbia University. The author has contributed to research in topics: Lipid bilayer fusion & Myosin. The author has an hindex of 32, co-authored 96 publications receiving 3056 citations. Previous affiliations of Ben O'Shaughnessy include Weizmann Institute of Science.

Assembly Mechanism of the Contractile Ring for Cytokinesis by Fission Yeast

Abstract: Animals and fungi assemble a contractile ring of actin filaments and the motor protein myosin to separate into individual daughter cells during cytokinesis. We used fluorescence microscopy of live fission yeast cells to observe that membrane-bound nodes containing myosin were broadly distributed around the cell equator and assembled into a contractile ring through stochastic motions, after a meshwork of dynamic actin filaments appeared. Analysis of node motions and numerical simulations supported a mechanism whereby transient connections are established when myosins in one node capture and exert force on actin filaments growing from other nodes.

Tropomyosin controls sarcomere-like contractions for rigidity sensing and suppressing growth on soft matrices

Abstract: Cells test the rigidity of the extracellular matrix by applying forces to it through integrin adhesions. Recent measurements show that these forces are applied by local micrometre-scale contractions, but how contraction force is regulated by rigidity is unknown. Here we performed high temporal- and spatial-resolution tracking of contractile forces by plating cells on sub-micrometre elastomeric pillars. We found that actomyosin-based sarcomere-like contractile units (CUs) simultaneously moved opposing pillars in net steps of ∼2.5 nm, independent of rigidity. What correlated with rigidity was the number of steps taken to reach a force level that activated recruitment of α-actinin to the CUs. When we removed actomyosin restriction by depleting tropomyosin 2.1, we observed larger steps and higher forces that resulted in aberrant rigidity sensing and growth of non-transformed cells on soft matrices. Thus, we conclude that tropomyosin 2.1 acts as a suppressor of growth on soft matrices by supporting proper rigidity sensing.

Molecular Mechanism of Cytokinesis.

Abstract: Division of amoebas, fungi, and animal cells into two daughter cells at the end of the cell cycle depends on a common set of ancient proteins, principally actin filaments and myosin-II motors. Anillin, formins, IQGAPs, and many other proteins regulate the assembly of the actin filaments into a contractile ring positioned between the daughter nuclei by different mechanisms in fungi and animal cells. Interactions of myosin-II with actin filaments produce force to assemble and then constrict the contractile ring to form a cleavage furrow. Contractile rings disassemble as they constrict. In some cases, knowledge about the numbers of participating proteins and their biochemical mechanisms has made it possible to formulate molecularly explicit mathematical models that reproduce the observed physical events during cytokinesis by computer simulations.

A fast, single-vesicle fusion assay mimics physiological SNARE requirements

Abstract: Almost all known intracellular fusion reactions are driven by formation of trans-SNARE complexes through pairing of vesicle-associated v-SNAREs with complementary t-SNAREs on target membranes. However, the number of SNARE complexes required for fusion is unknown, and there is controversy about whether additional proteins are required to explain the fast fusion which can occur in cells. Here we show that single vesicles containing the synaptic/exocytic v-SNAREs VAMP/synaptobrevin fuse rapidly with planar, supported bilayers containing the synaptic/exocytic t-SNAREs syntaxin-SNAP25. Fusion rates decreased dramatically when the number of externally oriented v-SNAREs per vesicle was reduced below 5–10, directly establishing this as the minimum number required for rapid fusion. Docking-to-fusion delay time distributions were consistent with a requirement that 5–11 t-SNAREs be recruited to achieve fusion, closely matching the v-SNARE requirement.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

Nanoparticle Polymer Composites: Where Two Small Worlds Meet

Abstract: The mixing of polymers and nanoparticles is opening pathways for engineering flexible composites that exhibit advantageous electrical, optical, or mechanical properties. Recent advances reveal routes to exploit both enthalpic and entropic interactions so as to direct the spatial distribution of nanoparticles and thereby control the macroscopic performance of the material. For example, by tailoring the particle coating and size, researchers have created self-healing materials for improved sustainability and self-corralling rods for photovoltaic applications. A challenge for future studies is to create hierarchically structured composites in which each sublayer contributes a distinct function to yield a mechanically integrated, multifunctional material.

The theory of polymer dynamics

Abstract: Recent years have brought exciting theoretical advances to understanding the behavior of macromolecular systems under nonequilibrium conditions. Developments in diffusion-controlled reactions of polymers are bringing molecular insights to reactive blending technologies, and improved theories relating to associating polymers should aid in the design of thickening agents and coatings. Recent progress in molecular theories of flow and deformation may facilitate the design of branched polymers with tailored rheological properties and improved adhesives.

Actin, a Central Player in Cell Shape and Movement

Abstract: The protein actin forms filaments that provide cells with mechanical support and driving forces for movement. Actin contributes to biological processes such as sensing environmental forces, internalizing membrane vesicles, moving over surfaces, and dividing the cell in two. These cellular activities are complex; they depend on interactions of actin monomers and filaments with numerous other proteins. Here, we present a summary of the key questions in the field and suggest how those questions might be answered. Understanding actin-based biological phenomena will depend on identifying the participating molecules and defining their molecular mechanisms. Comparisons of quantitative measurements of reactions in live cells with computer simulations of mathematical models will also help generate meaningful insights.