Lateral diffusion of proteins in cell membrane: the anomalous case

We present a method describing the lateral movement of proteins in cell membranes as observed in FRAP experiments. We extend earlier results derived for normal diffusion [1] to account for the case of anomalous subdiffusion. Our analytic closed forms are compared to computer simulations of anomalous diffusion and both show excellent agreement. The approach sheds light on the behavior of proteins in such complex systems and provides a tool to analyze experimental results

A Role for the Juxtamembrane Cytoplasm in the Molecular Dynamics of Focal Adhesions

Focal adhesions (FAs) are specialized membrane-associated multi-protein complexes that link the cell to the extracellular matrix and play crucial roles in cell-matrix sensing. Considerable information is available on the complex molecular composition of these sites, yet the regulation of FA dynamics is largely unknown. Based on a combination of FRAP studies in live cells, with in silico simulations and mathematical modeling, we show that the FA plaque proteins paxillin and vinculin exist in four dynamic states: an immobile FA-bound fraction, an FA-associated fraction undergoing exchange, a juxtamembrane fraction experiencing attenuated diffusion, and a fast-diffusing cytoplasmic pool. The juxtamembrane region surrounding FAs displays a gradient of FA plaque proteins with respect to both concentration and dynamics. Based on these findings, we propose a new model for the regulation of FA dynamics in which this juxtamembrane domain acts as an intermediary layer, enabling an efficient regulation of FA formation and reorganization

Lateral diffusion of proteins in cell membrane: the anomalous case

We present a method describing the lateral movement of proteins in cell membranes as observed in FRAP experiments. We extend earlier results derived for normal diffusion [1] to account for the case of anomalous subdiffusion. Our analytic closed forms are compared to computer simulations of anomalous diffusion and both show excellent agreement. The approach sheds light on the behavior of proteins in such complex systems and provides a tool to analyze experimental results

Lateral diffusion of proteins in cell membrane: the anomalous case

We present a method describing the lateral movement of proteins in cell membranes as observed in FRAP experiments. We extend earlier results derived for normal diffusion [1] to account for the case of anomalous subdiffusion. Our analytic closed forms are compared to computer simulations of anomalous diffusion and both show excellent agreement. The approach sheds light on the behavior of proteins in such complex systems and provides a tool to analyze experimental results

Fluorescence Recovery after Photobleaching: The Case of Anomalous Diffusion

The method of FRAP (fluorescence recovery after photobleaching), which has been broadly used to measure lateral mobility of fluorescent-labeled molecules in cell membranes, is formulated here in terms of continuous time random walks (CTRWs), which offer both analytical expressions and a scheme for numerical simulations. We propose an approach based on the CTRW and the corresponding fractional diffusion equation (FDE) to analyze FRAP results in the presence of anomalous subdiffusion. The FDE generalizes the simple diffusive picture, which has been applied to FRAP when assuming regular diffusion, to account for subdiffusion. We use a subordination relationship between the solutions of the fractional and normal diffusion equations to fit FRAP recovery curves obtained from CTRW simulations, and compare the fits to the commonly used approach based on the simple diffusion equation with a time dependent diffusion coefficient (TDDC). The CTRW and TDDC describe two different dynamical schemes, and although the CTRW formalism appears to be more complicated, it provides a physical description that underlies anomalous lateral diffusion