Absorption of di- and tripeptides by the intestine of the guinea-pig

This paper describes a method of quantifying the amount of smaller peptides in physiological fluids and reports the preliminary results of studying the mesenteric blood of adult guinea-pigs during absorption of a partial hydrolysate of casein. Because of the different roles suggested for plasma and erythrocytes in the inter-organ transport of amino acids, both plasma and whole blood have been studied. Whole blood and plasma samples were deproteinized with sulphosalicylic acid, and amino acids and small peptides separated from residual small amounts of protein on a Sephadex G-25 column. Ion exchange chromatography was then performed before and after acid hydrolysis. The concentration of small peptides in blood seems to be much lower than was previously believed. The adult guinea-pig did not absorb small peptides across the intestine into mesenteric whole blood or plasma in our experiments. However, casein hydrolysates are not necessarily representative of all protein hydrolysates, and further studies are required using different proteins and varying degrees of hydrolysis. The possibility of peptide transfer during development, and in conditions involving mucosal damage, should also be investigated. The present investigation confirms the assumption that predominantly plasma, and not red blood corpuscles, carries amino acids from the gut to the liver. It is worth noting, however, that taurine, aspartic acid, glutamic acid, citrulline and arginine were found in higher concentrations in whole mesenteric blood than in plasma.

Nalidixic acid-induced protein alterations in Escherichia coli

The effect of nalidixic acid on pulse-labeled protein patterns was analyzed by sodium dodecyl sulfate-polyacrylamide slab gel electrophoresis. The drug was found to alter protein patterns in a drug-sensitive strain but not in the isogenic drug-resistant strain of Escherichia coli. The drug-induced alteration of protein patterns was demonstrated by the appearance of some and the disappearance of other pulse-labeled peptides elicited by the drug.

Ribonucleotides covalently linked to deoxyribonucleic acid in T4 bacteriophage

Bacteriophage T4 was grown in the presence of labeled uridine. The deoxyribonucleic acid (DNA) of the phage was shown to contain covalently attached ribonucleotides. The label appears not to be internal in the DNA strands. Presumably, it is at the ends of the DNA strands and this may be related to DNA initiation.

Purification and properties of glycogen isolated from a blue-green alga, Nostoc muscorum

Alpha granules were isolated from a blue-green alga, Nostoc muscorum, in large quantities and high purity by sucrose density gradient centrifugation. Sodium deoxycholate was used to eliminate membrane contamination. Isolated alpha granules from this species have average dimension of 31 nm in width and 65 nm in length. Each alpha granule consists of two equal parts. Attempts to dissociate the intact granule under mild conditions into relatively large subunits did not succeed. Analytical centrifugation of the alpha granules yields a sedimentation coefficient of 265S (S(20, w)). Chemical analysis reveals that alpha granules contain highly branched polyglucosyl units with short external chain lengths.