A new titration system of a novel split-type superconducting magnet NMR spectrometer.

A new titration system for studying protein-ligand interactions has been developed. In this system, the sample solution is circulated in the route formed by an access path in a split superconducting magnet to maintain a constant protein concentration during the titration experiments. A concentration-control procedure for the ligand/protein ratio is devised, and the ligand/protein ratio is well controlled by this apparatus.

A study of the calcium complex of a glucosylceramide, soya-cerebroside II.

In order to study calcium ion complex of soya-cerebroside II (1), an ionophoretic glucosylceramide isolated from soybean, C8-cerebroside (3) and 3,3'',6''-trideoxy-C8-cerebroside (4) are designed and synthesized. On the basis of extensive 1H-NMR studies in the presence of Ca2+ and a continuous variation method via (1)H-NMR, soya-cerebroside II is suggested to form a calcium complex with 1/Ca2+ ratio of 1 : 1. Soya-cerebroside II serves as a tridentate chelating ligand for Ca2+; the amide carbonyl, C2'-hydroxy, and C2''-hydroxy oxygens are responsible for the Ca2+ binding. Soya-cerebroside II is structurally analogous to a neural glucosylceramide. Thus, the accumulated neural glucosylceramide inside of endoplasmic reticulum (ER) membrane may serve as an endogenous Ca2+-binding and -transport molecule (ionophore) that result in mobilization of Ca2+ from intracellular calcium stores.

Malformation of immature starfish oocytes by theonellapeptolide Ie, a Tridecapeptide lactone from a marine sponge Petrosia species, through disturbance of cortical F-actin distribution.

Theonellapeptolide Ie (Tp), an oligopeptide lactone isolated from a marine sponge, Petrosia sp., was shown to induce an unprecedented morphological change in the immature oocytes of the starfish Asterina pectinifera. The cortical F-actin was disturbed and assembled to form dots and rings, as evidenced by staining with rhodamine-conjugated phalloidin. The oocyte eventually became malformed. When Tp was added to an immature oocyte which had been pretreated with cytochalasin B or D, inhibitors of actin polymerization, no malformation was observed. When Tp was added to an oocyte which had been induced to mature by 1-methyladenine (1-MeAde), a maturation-inducing substance in starfishes, no morphological changes were observed in the maturing oocytes which reached the first meiotic prometaphase 40 min after the start of 1-MeAde treatment. This is the first description of a chemical that induces aberrant redistribution of F-actin-based cytoskeleton in an animal oocyte which is arrested at the first meiotic prophase.