A depth profile of lanthanide tetrad effect is presented for a water column collected in the southeastern Atlantic Ocean. The ABEXEL value to quantitatively indicate the lanthanide tetrad effect is plotted against the water depth. The features of the ABEXEL-depth profile provide understanding for the unique marine conditions of the Antarctic Ocean, and are quite different from those observed in the eastern Indian Ocean and the eastern North Pacific Ocean. The water column can be divided into six layers based on the features of the ABEXEL-depth profile. The development of a unique structure in the ABEXEL-depth profile and its implications are discussed together with the potential use of the lanthanide tetrad effect in elucidation of our understanding of the formation of deep seawaters within the oceans.
A composite diapir model for extensive basaltic volcanism is proposed on the basis of the melting phase relations of subducted oceanic crust in the mantle. Ascending peridotitic diapir across 660km discontinuity drags fragments of subducted oceanic crust stagnating there into the diapir and forms a“composite diapir”. Because of the differential melting between peridotite and oceanic crust, ascent of such a composite diapir can produce voluminous basaltic magma by melting of subducted oceanic crust, capsulated in solid peridotite. Release of the voluminous basalt magma would be triggered by partial melting of diapir-forming peridotite in the shallow upper mantle. Physical and chemical properties of the resulting hybrid magma can explain most features of continental flood basalt.
This article briefly reviews our recent investigation on the synthesis and biological functions of artificial glycopeptide-conjugates via ring-opening polymerization of D-glucose- or N-acetyl-D-glucosamine-substituted L-serine N-carboxyanhydrides (glycoNCAs). Primary amine-initiated polymerization of glycoNCAs proceeded without side reactions to give linear glycopeptide-conjugates of controlled chain lengths. A variety of block copolymers and graft copolymers containing glycopeptide segments were synthesized by utilizing the living nature of the ring-opening polymerization of glycoNCAs. Reaction of primary amine-terminated poly(amido amine) dendrimers of different generations with a slight excess of glycoNCAs at -30°C gave a new type of dendrimers whose surfaces were modified with the corresponding mono(glycopeptide) moieties. Oligomerization of glycoNCAs with poly(amido amine) dendrimer as a multifunctional macroinitiator at 27°C provided globular macromolecules coated with oligo(glycopeptide) chains. Molecular recognition abilities of these linear and globular glycopeptide-conjugate macromolecules were evaluated by the hemagglutination inhibition assay.
A new way of solubilizing hydrolytic enzymes in organic media was achieved by coating the enzyme with lipid monolayers. Lipid-coated enzymes have been used successfully for a number of types of reactions in organic media or organic-aqueous two-phases, for example enantioselective esterification by lipase, transphosphatidylation of water-insoluble phospholipids by phospholipase D, hydrolysis of a lipophilic substrate by a catalytic antibody, and transglycosylation by, β-D-galactosidase.
In cardiac muscle of the chicken, slow skeletal form of troponin I (STnI) is initially expressed in the embryo, but it is later replaced by the cardiac form (CTnI). In contrast, in fast and slow skeletal muscles, CTnI is never expressed throughout the course of development. To examine how such a normally absent cardiac isoform behaves in embryonic skeletal muscle if force-expressed, we established several C2C12 skeletal muscle cell lines that stably express CTnI. We used CTnI/9, whose amino acid sequence corresponds to 90% of that of CTnI. In all of these clones, fusion of myoblasts to form myotubes was inhibited. In a clone expressing CTnI/9 at the highest level, networks of thick actin bundles were found. Thus, expression of the TnI isoform, specific for adult cardiac muscle and absent in embryonic skeletal muscle, disturbs normal myogenic differentiation and myofibrillogenesis in skeletal muscle cells.
In order to investigate the sorting specificity of myosin essential light chain (ELC) isoproteins for myosin heavy chain (MHC) of the nonmuscle type of stress fibers, epitope-tagged ELC cDNAs of the nonmuscle and fast skeletal muscle types were force-expressed in cultured cardiac fibroblasts from chicken embryos. Although the expressed ELC of the former type was found in the cytoplasm and nucleus as well as on stress fibers, that of the latter was found only along stress fibers. Thus, compared to ELC of the nonmuscle type, that of the fast skeletal muscle type has a higher affinity for the nonmuscle MHC present endogenously in fibroblast stress fibers. Together with the observation that this isoform has the highest affinity for MHC of the cardiac muscle type in myofibrils of caridomyocytes (Komiyama et al., 1996, J. Cell Sci. 109, 2089-2099), it can be concluded that ELC of the fast skeletal muscle type is an evolved isoform possessing the ability to associate tightly with a variety of MHC isoforms.