Harold Tarver

The metabolism of methyl mercaptan in the intact animal

Abstract In experiments in which methyl mercaptan-C 14 or S 35 had been administered to rats in vitro the following has been found: 1. 1. Both the carbon and the sulfur of the mercaptan are rapidly oxidized to carbon dioxide and sulfate, respectively. 2. 2. The methyl carbon of the mercaptan is converted to the β-carbon of serine and methyl groups of methionine, choline, and creatine. 3. 3. Sulfur from methyl mercaptan does not appear to any significant extent in the methionine or cystine of liver protein.

Studies on protein synthesis in vitro. IV. Concerning the apparent uptake of methionine by particulate preparation from liver

Abstract 1. 1. When incubated with methionine-C14H3 or methionine-S35, the proteins in mitochondria from rat liver retain radioactivity which is not removed by washing with trichloroacetic acid, alcohol, or ether. 2. 2. Most of the radioactivity retained is removed by reducing agents to give a product soluble in ether. 3. 3. By using the carrier technique the product has been shown to be methyl mercaptan (methanethiol). 4. 4. Methyl mercaptan is formed from the keto acid corresponding to methionine more rapidly than from the amino acid itself. 5. 5. The system responsible for methyl, mercaptan formation is not identical with the thionase preparation of Binkley and Okeson. It is rather labile and insensitive to respiratory poisons, but sensitive to thiols such as homocysteine. 6. 6. The label taken up by the protein of liver slices incubated with methiol-labeled methionine is stable to reducing agents.

Breakdown of Urea in the Rat

Summary A rapid breakdown of urea-C14 is observed in the intact rat but this is entirely absent in the eviscerated animal. Due to the existence of this breakdown which is immediately followed by resynthesis, there is a type of urea cycle in the intact animal. No significant breakdown of urea occurs in either liver, kidney or stomach, but the intestinal washings rapidly decompose the substance.

The conversion of methionine-S35 to cystathionine-S35 and taurine-S35 in the rat

Abstract 1. 1. Evidence has been presented which shows that methionine S is converted to cystathionine S in the intact rat. 2. 2. Methionine S is also converted to glutathione S and taurine S at a rapid rate.

Plasma Protein. IV. Results with Generally Labeled Plasma Protein.

Summary It is possible to produce generally labeled plasma protein with very high specific activity in rats by feeding them suitable bacteria (Rhodospirillum rubrum) cultured in media containing labeled bicarbonate. These bacteria have protein in which all the amino acids present are labeled. The metabolism, in the recipient rats; of the C14 in the plasma protein from these donor animals (B) has been investigated and compared with that already described ( 1 , 2 , 7 ) for plasma protein labeled by feeding donor rats serine-β-C14 (A), with the following results: (1) The disappearance of the C14-labeled protein B from the circulation, following its intravenous injection, follows the same curve as that found when protein A was employed. (2) The appearance of C14O2 in the respiratory gases is significantly less in these animals following the parenteral injection, but more following the oral administration than in recipients A. (3) As compared with A, the tissues of recipients B contain more C14-labeled protein no matter which route of administration is employed, and this is particularly true when the C14-labeled protein is given orally.

Electrophoresis of rat plasma. III. Preparation of S35 labeled albumin.

Abstract A procedure involving ethanol fractionation for obtaining purified S 35 -labeled albumin from 2 ml. of rat plasma has been described. The albumin was 95% pure, as revealed by boundary electrophoresis. An apparently homogeneous product was obtained by zone electrophoresis on starch. Paper chromatography and radioautography of the hydrolyzate of albumin reveal that cystine is responsible for the greatest amount of radioactivity.

Biosynthesis of C14-labeled protein and amino acids with Rhodospirillum rubrum☆

Abstract Conditions are described for the culture of Rhodospirillum rubrum in media containing labeled carbon dioxide and unlabeled alcohol as sole carbon sources such that protein and amino acids of high specific activity are produced. As much as 40% of the radioactive carbon employed is found in the acid hydrolyzate of the trichloroacetic acid- and alcohol-washed bacteria. Of this amount most is in the form of labeled amino acids, particularly in the dicarboxylic acids, glycine, alanine, and in a mixture of phenylalanine and arginine.

[146] Determination of inorganic sulfur compounds

Publisher Summary In determination of total sulfur sample is digested with nitric acid and perchloric acid, which results in the conversion of all the sulfur compounds to sulfate. Sulfate is then precipitated either as barium sulfate or as benzidine sulfate. In the former case the sulfate is determined gravimetrically, in the latter volumetrically by titration with standard base (or colorimetrically). If the material contains significant amounts of phosphorus, relative to the sulfur, it is necessary to resort to preprecipitation of the phosphate either as magnesium ammonium phosphate or as uranyl phosphate; otherwise benzidine phosphate may be precipitated along with the sulfate. Also, the completeness of precipitation of the benzidine sulfate should be checked when the salt concentration, e.g., NaC1, in the unknown is high. Moreover, free sulfate can be determined either by precipitation as the barium or benzidine salts. When ethereal sulfates are present, however, as in urine, these may be hydrolyzed to a considerable extent under hot acidic solution. Consequently it is advisable to precipitate tile free sulfate as the barium salt in the cold. When it is necessary to deal wittl very small amounts of free sulfate, the sulfate may be precipitated as benzidine sulfate and determined colorimetrically.

Isotopic studies on the reconstitution of insulin under normal and at high pressure. Exchange and adsorption of alanine to insulin

Abstract After removal of the terminal alanine from insulin by carboxypeptidase, it was impossible to demonstrate the recombination of alanine with the protein, using alanine-1-C14 as an indicator. The presence of the active enzyme in 20 % sucrose, either at normal atmospheric pressure or at a high pressure (6000 atm.) did not affect the uptake of alanine-1-C14 by the insulin. Experiments of this type yielded negative results in spite of varying the pH, time of reaction, and concentration of alanine over wide ranges. However, alanine, particularly at high pH, did become, firmly bound to insulin (and albumin) by a reaction which is mediated by heavy-metal ions. The dependence of this amino acid binding to protein on metal-ion concentration, pH, and time of reaction has been investigated. In addition to the previously mentioned results with respect to the recombination of alanine with insulin from which the terminal alanine had been removed, it has also been found impossible to demonstrate any exchange of alanine in insulin for alanine-1-C14 in solution in the presence of either carboxypeptidase or trypsin.

The Preparation of Labeled Albumin for Turnover Studies

The preparation of labeled-serum albumin for turnover studies has assumed increasing importance in recent years. Whereas originally the study of turnover with albumin appeared to be primarily of basic and theoretical interest, more recently it has assumed practical and clinical importance. This latter fact has come about because certain syndromes associated with low serum albumin and excessive loss of albumin into the gastrointestinal tract can only be diagnosed by the use of labeled albumin, and calculation of turnover rates. Since the inception of turnover studies various techniques of labeling have been developed. Considerable controversy has existed and still exists as to their relative merits.