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S Chen

Publications and source records attributed to S Chen.

At least 1,567 records · Page 87Linked to original sources
PubMed1973

Biosynthesis of monensin.

The biosynthesis of monensin by Streptomyces cinnamonensis was studied by using (14)C-labeled glucose, acetate, propionate, butyrate, and methionine. The results indicated that the antibiotic is synthesized from five acetate, seven propionate, and one butyrate molecules. The o-methyl group of monensin is derived from methionine, whereas the terminal hydroxymethyl group is incorporated from acetate.

Anti-Bacterial Agents↗
PubMed1972

An investigation of sodium transport in barnacle muscle fibres by means of the microsyringe technique.

1. The cation composition of single barnacle muscle fibres following damage by axial insertion of a microsyringe has been measured. The Na and Ca contents of these fibres were raised.2. Electronmicroscopic studies of fibres following insertion of a microsyringe indicated that the damage done resulted in tubular obstruction of the T-system.3. Fibres loaded with radiosodium by micro-injection showed that the Na(*) efflux declined exponentially with time, but that in most fibres the slope ratio of d/dt ln [Na(*)](1) to d/dt (ln d[Na(*)](i)/dt) was less than unity. Injections of distilled water deep in the fibre failed to influence the course of the Na(*) efflux.4. K removal reduced the Na efflux by 47%. However, a few fibres displayed very little K-dependence.5. When measured in fibres already soaked in a K-free medium for long periods the sodium efflux consisted of a brief rapid phase, followed by a slow phase of Na loss.6. In the presence of 30 mM-K, there was little or no rise in the Na efflux. Raising the external K to 50 or 100 mM caused a marked rise in the Na efflux. Raising the external K to 30 mM in the absence of external Ca(2+) led to a rise in the Na efflux. A high K solution always caused shortening of these fibres.7. Internal application of 1 M or 1 mM-CaCl(2) often caused a significant rise in the Na efflux.8. Internal application of 2.5 or 5 M saline caused a prompt and large fall in the Na efflux. In the presence of high K saline-loaded fibres failed to contract.9. Internal application of 0.5 M-ATP stimulated the Na efflux. A larger effect was not observed in fibres pre-treated with 2 M-MgCl(2). Internal application of 0.5 M-ArP was without effect.10. The results indicate that the barnacle fibre is a suitable preparation for the study of Na fluxes by means of the micro-injection technique. They also indicate that the mechanism regulating the Na efflux is not quite the same as that found in squid axon or frog muscle.

Adenosine Triphosphate↗