Biology subjects

Florin, E.-L.

Publications and source records attributed to Florin, E.-L..

3 recordsLinked to original sources

bioRxiv2018

Resolving Filament Level Mechanics in Collagen Networks using Activity Microscopy

Collagen is the most abundant protein in humans and the primary component of the extracellular matrix, a meshwork of biopolymer networks, which provides structure and integrity to tissues. Its mechanical properties profoundly influence the fate of cells. The cell-matrix interaction, however, is not well understood due to a lack of experimental techniques to study the mechanical interplay between cells and their local environment. Here we introduce Activity Microscopy, a new way to visualize local network mechanics with single filament resolution. Using collagen I networks in vitro, we localize fibril positions in two-dimensional slices through the network with nanometer precision and quantify the fibrils transverse thermal fluctuations with megahertz bandwidth. Using a fibrils thermal fluctuations as an indicator for its tension, we find a heterogeneous stress distribution, where \"cold\" fibrils with small thermal fluctuations surround regions of highly fluctuating \"hot\" fibrils. We seed HeLa cells into collagen networks and quantify the anisotropy in the propagation of their forces.

biophysics↗

bioRxiv2018

Reversible solidification of fission yeast cytoplasm after prolonged nutrient starvation

Cells depend on a highly ordered organization of their content and they must develop strategies to maintain the anisotropic distribution of organelles during periods of nutrient shortage. One of these strategies, observed in bacteria and in yeast cells with acutely interrupted energy production, is to solidify the cytoplasm. Here, we describe a different type of cytoplasm solidification that occurs in fission yeast cells having slowly run out of nutrients after multiple days of culturing. It provides the most profound reversible cytoplasmic solidification of yeast cells described to date. Our data suggest the involvement of a matrix with a certain mesh size that immobilizes cellular components in a size-dependent manner. We provide experimental evidence that cells need time, intrinsic nutrients and intrinsic energy sources to enter this state in the absence of external sources. Such cytoplasmic solidification may provide a robust means to protect cellular architecture in dormant cells.

cell biology↗

bioRxiv2017

Nucleotide-dependent stiffness suggests role of interprotofilament bonds in microtubule assembly

Many eukaryotic cell functions depend on dynamic instability, meaning the nucleotide-driven assembly and disassembly of microtubules. Assembly requires the constituent tubulin dimers to bind the nucleotide GTP, and its subsequent hydrolysis to GDP induces disassembly. The underlying structural mechanisms, however, are not well understood. Here, we determine the strength of contacts in the microtubule lattice by combining high precision measurements of the bending stiffness of analogues of GTP and GDP microtubules with a recent theoretical model. While previous structural studies have focussed on how the curvature of the tubulin dimer is affected by nucleotide binding, we present evidence of a dramatic regulation of the lateral interactions between the parallel protofilaments that dimers form in the microtubule. We conclude that the shear coupling between neighboring protofilaments is at least two orders of magnitude stronger in the GTP state than in the GDP state, and discuss the implications for the microtubule assembly.

biophysics↗