The “depth of compensation” of isostasy was determined for the Maldive Islands and the Chagos archipelago, Indian Ocean. The compensation depth in the region becomes shallow according as the age of the ridge becomes old. The ascending speed of the depth of compensation is about 10km/10ma (1mm/year). To explain the time variation of the depth of compensation, we proposed two models: bubble model and two layers model. In the bubble model, low density material at the deep part of the mantle moves upward. In the two layers model, low density material lies at two layers of different depth and the buoyancy due to these low density material at each depth varies with time, keeping constant the sum of the buoyancy.
Enzymatic ring-opening copolymerization of lactones was carried out by using Pseudomonas fluorescens lipase in bulk. In the copolymerizaton of ε-caprolactone (ε-CL) and δ-valerolactone at 60°C for 10 days a copolymer with molecular weight of 3.7×103 was obtained and its structure was found to be of random structure having both units from 13C NMR anlaysis. Effects of the feed ratio, the reaction time and temperature on the copolymerization have been examined. The enzymatic copolymerization of ε-CL with other lactones and D-lactide also gave corresponding copolymers.
Direct genomic DNA sequencing (DGS) of Butyrivibrio fibrisolvens 16S rDNA genes, and of regions 3' and 5' to the genes, was achieved using a linear amplification sequencing reaction with a single oligonucleotide primer, without prior cloning or amplification of the target sequence. The utility of the method was demonstrated by comparison with PCR-amplified template sequencing methods. Sequence differences were revealed by DGS between 16S rRNA genes from two strains of the rumen bacterium Butyrivibrio fibrisolvens isolated in different countries. Using DGS we were able to determine the sequence of the 5'- and 3'-termini and flanking regions, as well as the sequence of the gene itself.
We studied the dynamic turnover of bone by measuring metabolic markers in 6 healthy pregnant women, aged 23-28. Resorption markers, tartrate-resistant acid phosphatase and deoxypyridinoline, increased in the last trimester and after partrition decreased until puerperium day 30. The serum level of intact osteocalcin, a formation marker, exhibited a slight decrease during pregnancy and increased following childbirth. In the last trimester, the peripheral monocyte secreted much amount of interleukin (IL)-1 and tumor necrosis factor (TNF)-α, potent stimulants of osteoclast, in parallel with the resorption markers. Estrogen has the bone sparing effect by inhibiting cytokine secretion in the bone microenvironment and peripheral mononuclear cell. Biomarker changes, however, disclosed uncoupling of bone with high resorption and low formation in the last trimester with a higher estrogen level than any other period of life, which might be mediated by a high amount of IL-1 and TNF-α through stimulating osteoclast activity.
The mechanism of secondary active transport processes has been proposed as an ordered binding model, based on substrate binding studies dependent on coupling cation concentrations (Yamato, I. (1992) FEBS Lett., 298, 1-5). The reason why the systems adopt the ordered binding mechanism is discussed from the point of view of the coupling efficiency of the energy transduction. It is proposed that the mechanism guarantees the tight coupling of the system. The ordered binding mechanism is then proposed as the general mechanistic model for various bioenergy transducing systems with tight coupling.
Infrared spectra of an oriented fiber made from 1200 kDa fragment of rabbit skeletal muscle connectin (titin) showed an abundance of β-sheet structures. Infrared dichroism revealed that the β-sheets were alligned with their mainchain axes parallel to the fibre axis. This conclusion is in good agreement with the results of chicken breast muscle β-connectin (Uchida, K. et al., FEBS Lett., 295, 35-38 (1991)). A model of molecular structure of connectin is presented.
Recently, observed large values of 'step size' in in vivo muscle contraction1), 2) and in vitro actomyosin motility assays3)-5) have raised new questions about the nature of coupling in biological systems. It has been experimentally demonstrated7) that multiple working strokes occur during the hydrolysis of one ATP molecule. It is difficult to explain these observations by conventional enzyme kinetics. In this paper, we propose a novel enzymatic mechanism (the 'coupling ratio constraint' mechanism). By 'free energy mixing' between the two coupled degrees of freedom, we can explain the mechanism underlying the large values of step size and the multiple working strokes per ATP hydrolyzed observed in muscle. We predict that myosin would behave in an unconventional manner during the multiple working strokes. This prediction can be tested experimentally. Finally, we propose that 'thermal interference', similar to quantum interference20)(but of different physical origin) is involved in the observed phenomenon.