PubMed · 5666810
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L Demetrius. 1968. Cellular systems as graphs.. https://doi.org/10.1007/bf02476942
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The dielectric properties of the human skin stratum corneum (SC) in the frequency range higher than 107 Hz are not well understood because of the difficulty in selective scanning of the SC area in vivo. The present study was carried out to make clear factors responsible for the dielectric properties using a measuring system specially developed for the study of SC [S. Naito, M. Hoshi, S. Mashimo, Anal. Biochem. 251 (1997) 163-172]. We found that the dielectric properties of SC can be expressed by the linear combination of two relaxation processes and d.c. conduction. The faster relaxation is that of free water. The slower relaxation and d. c. conduction were analyzed using a model assuming interfacial polarization between dissimilar materials. We concluded that the polarization is the origin of the slower relaxation process because the experimental data could be well interpreted according to the above mechanism. We also concluded that the polarization of swelled SC locates at the interface between SC cells and the intercellular lipid layer, or at the interface between the lipophilic and the hydrophilic part of the lamellar structured intercellular lipid layer.
A new approach in implementing classical molecular dynamics simulation for parallel computers has enabled a simulation to be carried out on a protein with explicit representation of water an order of magnitude longer than previously reported and will soon enable such simulations to be carried into the microsecond time range. We have used this approach to study the folding of the villin headpiece subdomain, a 36-residue small protein consisting of three helices, from an unfolded structure to a molten globule state, which has a number of features of the native structure. The time development of the solvation free energy, the radius of gyration, and the mainchain rms difference from the native NMR structure showed that the process can be seen as a 60-nsec "burst" phase followed by a slow "conformational readjustment" phase. We found that the burial of the hydrophobic surface dominated the early phase of the folding process and appeared to be the primary driving force of the reduction in the radius of gyration in that phase.
Human mitochondrial RNase P does not distinguish itself from other RNase P enzymes by most of its basic properties. 5' phosphates on tRNA products, strict dependence on a divalent cation, independence of ATP or other cofactors, and sensitivity to puromycin are generally characteristic for RNase P. Slow sedimentation of human mitochondrial RNase P in glycerol gradients suggests a molecular weight considerably lower than that of bacterial or nuclear RNase P. In contrast to fungi, all putative components of mammalian mitochondrial RNase P are encoded by the nucleus. Intriguingly, no indication of the involvement of a trans-acting RNA was found in mammalian mitochondrial tRNA processing. Mitochondrial RNase P is resistant to rigorous treatments with nucleases and exhibits a protein-like density in Cs2SO4 gradients. Moreover, an analysis of copurifying RNAs revealed no putative RNase P RNA candidates. These data suggest that mammalian mitochondrial RNase P, unlike its nuclear counterpart or its bacterial relatives, is not a ribonucleoprotein but a protein enzyme.