Article Information
PubMed
Related Articles
- Dynamic Contact Forces on Leukocyte Microvilli and Their Pen...Dynamic Contact Forces on Leukocyte Microvilli and Their Penetration of the Endothelial Glycocalyx
Biophysical Journal, Volume 80, Issue 3, 1 March 2001, Pages 1124-1140
Yihua Zhao, Shu Chien and Sheldon Weinbaum
AbstractWe develop a theoretical model to examine the combined effect of gravity and microvillus length heterogeneity on tip contact force () during free rolling in vitro, including the initiation of L-, P-, and E-selectin tethers and the threshold behavior at low shear. grows nonlinearly with shear. At shear stress of 1dyn/cm, is one to two orders of magnitude greater than the 0.1pN force for gravitational settling without flow. At shear stresses >0.2dyn/cm only the longest microvilli contact the substrate; hence at the shear threshold (0.4dyn/cm for L-selectin), only 5% of microvilli can initiate tethering interaction. The characteristic time for tip contact is surprisingly short, typically 0.1–1ms. This model is then applied in vivo to explore the free-rolling interaction of leukocyte microvilli with endothelial glycocalyx and the necessary conditions for glycocalyx penetration to initiate cell rolling. The model predicts that for arteriolar capillaries even the longest microvilli cannot initiate rolling, except in regions of low shear or flow reversal. In postcapillary venules, where shear stress is ∼2dyn/cm, tethering interactions are highly likely, provided that there are some relatively long microvilli. Once tethering is initiated, rolling tends to ensue because and contact duration will both increase substantially to facilitate glycocalyx penetration by the shorter microvilli.
Abstract | Full Text | PDF (302 kb) - Pretransitional Effects in Dimyristoylphosphatidylcholine Ve...Pretransitional Effects in Dimyristoylphosphatidylcholine Vesicle Membranes: Optical Dynamometry Study
Biophysical Journal, Volume 79, Issue 1, 1 July 2000, Pages 340-356
R. Dimova, B. Pouligny and C. Dietrich
AbstractWe used micron-sized latex spheres to probe the phase state and the viscoelastic properties of dimyristoylphosphatidylcholine (DMPC) bilayers as a function of temperature. One or two particles were manipulated and stuck to a DMPC giant vesicle by means of an optical trap. Above the fluid-gel main transition temperature, ≅ 23.4°C, the particles could move on the surface of the vesicle, spontaneously (Brownian motion) or driven by an external force, either gravity or the laser beam’s radiation pressure. From the analysis of the particle motions, we deduced the values of the membrane hydrodynamic shear viscosity, , and found that it would increase considerably near . Below , the long-distance motion of the particles was blocked. We performed experiments with two particles stuck on the membrane. By optical dynamometry, we measured the elastic resistance of the membrane to a variation in the interparticle distance and found that it would decrease considerably (down to zero) when the temperature was increased to . We propose an interpretation relating the elastic response to the membrane curvature modulus, . In this scheme, the two-bead dynamometry experiments provide a direct measurement of in the P′ phase of lipid bilayers.
Abstract | Full Text | PDF (381 kb) - One chromosome: one DNA moleculeOne chromosome: one DNA molecule
Trends in Biochemical Sciences, Volume 24, Issue 3, 1 March 1999, Pages 121-123
Bruno H. Zimm
Full Text | PDF (85 kb) - …more
Copyright © 1979 The Biophysical Society. All rights reserved.
Biophysical Journal, Volume 28, Issue 1, 93-105, 1 October 1979
doi:10.1016/S0006-3495(79)85161-9
Research Article
Viscoelastic behavior of mammalian DNA
E.S. Chase and R.H. Shafer
Abstract
The viscoelastic behavior of rat 9L cellular DNA was studied as a function of the detergent used for lysis, the pH and duration of lysis, and gamma ray dose. For nondenaturing lysis conditions, a model of the DNA was proposed to account for the effects of these agents on the viscoelastic retardation time. It was concluded that these agents affect the hydrodynamic radius of the DNA rather than its molecular weight. For denaturing lysis conditions, molecular weights calculated from the relaxation time were consistent with those calculated from alkaline sucrose sedimentation profiles.
