Biomedical subjects

Lawrence C-L Lin

Publications and source records attributed to Lawrence C-L Lin.

6 recordsLinked to original sources

PubMed2006

Analysis of shape, fluctuations, and dynamics in intermembrane junctions.

A dynamic-elastic model for weakly adhered intermembrane junctions is presented. Helfrich membrane energetics coupled to hydrodynamic modes of the surrounding solvent reproduce the average shape, fluctuations, and dynamics of these junctions as measured experimentally. Comparison between numerical results and experimental data provides the first direct measure of surface tension in these systems (0.01-0.06 dyn/cm). The measurements suggest bilayer-bilayer adhesion energetics as the dominant source of surface tension in the experimental systems.

Computer Simulation↗

PubMed2006

Nonequilibrium membrane fluctuations driven by active proteins.

We extend a model for nonthermal membrane undulations driven by active (adenosine triphosphate-dependent or light-harvesting) membrane proteins [N. Gov, Phys. Rev. Lett. 93, 268104 (2004)]. The present model accounts for the fact that proteins can diffuse laterally across the membrane surface and that individual proteins are expected to exert forces preferentially in one normal direction over the other (due to their orientation within the bilayer). The addition of these effects alters the scaling of fluctuation amplitudes with system size. Additionally, theoretical arguments and dynamic simulations both suggest that, in certain regimes, the probability distribution of fluctuation amplitudes is expected to be non-Gaussian (in contrast to thermal systems).

Biomechanical Phenomena↗

PubMed2005

Implicit solvent simulation models for biomembranes.

Fully atomic simulation strategies are infeasible for the study of many processes of interest to membrane biology, biophysics and biochemistry. We review various coarse-grained simulation methodologies with special emphasis on methods and models that do not require the explicit simulation of water. Examples from our own research demonstrate that such models have potential for simulating a variety of biologically relevant phenomena at the membrane surface.

Biophysical Phenomena↗

PubMed2005

Dynamic simulations of membranes with cytoskeletal interactions.

We describe a simulation algorithm for the dynamics of elastic membrane sheets over long length and time scales. Our model includes implicit hydrodynamic coupling between membrane and surrounding solvent and allows for arbitrary external forces acting on the membrane surface. In particular, the methodology is well suited to studying membranes in interaction with cytoskeletal filaments. We present results for the thermal undulations of a lipid bilayer attached to a regular network of spectrin filaments as a model for the red blood cell membrane. The dynamic fluctuations of the bilayer over the spectrin network are quantified and used to predict the macroscopic diffusion constant of band 3 on the surface of the red blood cell. We find that thermal undulations likely play a role in the mobility of band 3 in the plane of the erythrocyte membrane.

Algorithms↗

PubMed2004

Brownian dynamics in Fourier space: membrane simulations over long length and time scales.

A simulation algorithm for elastic membrane sheets is presented. Overdamped stochastic dynamics including hydrodynamic coupling to surrounding solvent and arbitrary external forces are generated by employing Fourier modes of the sheet as the primary dynamic variables. Simulations over the micron length scale and second time scale are easily achieved. The dynamics of a lipid bilayer attached to an underlying network of cytoskeletal filaments is used to estimate the diffusion constant of membrane-bound proteins on the surface of the red blood cell.

Animals↗

PubMed2004

Dynamics of pinned membranes with application to protein diffusion on the surface of red blood cells.

We present a theoretical treatment and simulation algorithm for the dynamics of Helfrich elastic membrane surfaces in the presence of general harmonic perturbations and hydrodynamic coupling to the surrounding solvent. In the limit of localized and strong interactions, this harmonic model can be used to pin the membrane to intracellular/intercellular structures. We consider the case of pinning to the cytoskeleton and use such a model to estimate the macroscopic diffusion constant for band 3 protein on the surface of human erythrocytes. Comparison to experimental results suggests that thermal undulations of the membrane surface should play a significant role in protein mobility on the red blood cell.

Adsorption↗