PubMed · 930551
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
R Glaser. 1977. Mathematical biophysics.. https://pubmed.ncbi.nlm.nih.gov/930551/
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
Following Fröhlich we consider a system that models a biological one, for example, a long chain of proteins possessing polar modes of vibration and where energy is pumped through metabolic processes. We consider the effect produced by free electrons that are usually present as hole carriers in proteins with electron-donor molecules. A theory of relaxation based on the non-equilibrium statistical operator method is used in the derivation of the kinetic equations to introduce non-linearities due to interactions of the polar vibrations with the carriers and with a thermal bath. These non-linearities arising from high order relaxation processes lead to the emergence of the Fröhlich effect in the polar modes, i.e. the occurrence of a (non-equilibrium) Bose-Einstein-like condensation. It points to an instability of the system that seems to be followed by a morphological transformation in the form of a spatially ordered dissipative structure.
An investigation of the statistical properties of the native conformations of proteins, observed from crystal structures, is reported. Protein conformations were analyzed in terms of a bond vector correlation function and molecular volume. It was observed that, while the volume of a protein structure varies nearly linearly with the number of residues, the bond vector correlation function exhibits a universal feature for all sizes of proteins. To interpret the nature of the bond vector correlation function of native protein structures quantitatively, Monte Carlo simulations of realistic polypeptide chains of specific but arbitrary amino acid sequence were carried out. The molecule was constrained in an ellipsoidal volume determined by its chain length, and conformations with unacceptable nonbonded contacts between different amino acid residues were excluded. The interactions within a terminally blocked single residue, which correlate two nearest-neighbor peptide groups in a chain, were taken into account by an energetically biased sampling of its phi-psi space. The simulated chain correlation functions were found to be in good agreement with those of the crystal structures of beta-sheet-type and mixed-type (alpha+beta) proteins of similar length. On the basis of these calculations, it is concluded that the observed conformations of these native proteins may arise from two basic factors: the compactness of structures under hydrophobic interactions and the intrinsic stiffness of polypeptide chains due to the interactions within each terminally blocked residue.
A parallel-plate flow chamber is developed in order to study cellular adhesion phenomena. An image analysis system is used to observe individual cells exposed to flow in situ and to determine area, perimeter, and shape of these cells as a function of time and shear stress. With this flow system the behavior of human fibroblasts spread on glass is studied when exposed to an increasing laminar flow. The flow system appears to be well-suited for following individual cells during detachment. After 75 to 90 min, at a shear stress of 350 dynes/cm2, more than 50% of the spread cells are detached from the surface. Cells with higher spreading areas stay longer at the glass surface. Cells round up before detaching. Sometimes the cell body is attached to the substratum through a thin filament during detachment. At the scanning electron microscopy level numerous filopodial extensions are observed. Cell material could only rarely be observed at the light or scanning electron microscopic level on the substratum once a cell was detached.