Glenn E. Pollock

Stereoisomers of isovaline in the Murchison meteorite

Abstract Isovaline is present in the Murchison meteorite as a racemic mixture (about equal concentrations of the R and S enantiomers). Since isovaline does not have a hydrogen atom on its asymmetric α-carbon atom, the racemic mixture could not have formed by commonly accepted mechanisms of racemization. Thus, isovaline in the meteorite most probably was synthesized as a racemic mixture and is not the result of the racemization of either the R or S enantiomer. Other chiral amino acids in the meteorite are present as racemic mixtures, and were probably synthesized in a similar manner by abiotic, extraterrestrial processes.

Search for Organic Compounds in the Lunar Dust from the Sea of Tranquiblity

A sample of lunar dust was examined for organic compounds. Carbon detected in concentrations of 157 micrograms per gram had a δ13C per mil (PDB) value of + 20. Treatment with hydrochloric acid yielded hydrocarbons of low molecular weight, suggesting the presence of carbides. The gas chromatogram of the acylated and esterified derivatives of the hydrolyzate was similar to that obtained for the Pueblito de Allende meteorite. There were no detectable amounts of extractable high-molecular-weight alkanes, aromatic hydrocarbons, isoprenoid hydrocarbons, normal alkanes, fatty acids, amino acids, sugars, or nucleic acid bases. Traces of porphyrins were found, perhaps arising from rocket exhaust materials.

The extent of racemization of some amino acids in dilute alkali-treated protein and soil humic and fulvic acid.

Abstract A study was made of the racemizing effect of mild alkaline treatment upon two proteins and humic and fulvic acid fractions from soils. It was found that the two proteins differed considerably so far as the beginning of racemization was concerned. Racemization of the soil fractions was significant in 24 hr, but was not radically different from gelatin, and in no case was the amino acid optical activity completely destroyed. Of the nine amino acids reported, all were less than 30% racemized by the 24 hr alkali treatment, and most were less than 20% racemized. Even in the amino acids most highly racemized—alanine, aspartic acid, phenylalanine, glutamic acid, and lysine—complete racemization did not occur after 96 hr. All other amino acids (valine, isoleucine, leucine, and proline) were less than 20% racemized in any 24 hr sample and that value was approached only by valine in the fulvic acid sample. While these results indicate that 0.5 N NaOH could be used as a soil extractant to indicate optical activity for life detection purposes, a milder extractant which would not affect the optical properties of the molecules of interest would be desirable. Further studies are now in progress.

Stereochemistry of amino acids in surface samples of a marine sediment

Abstract In two surface samples of marine sediment, the percentages of d -alanine and d -aspartic acid are significantly higher than the other d -amino acids and are similar to the range found in soils. The percentage of d -glutamic acid is also higher than the other amino acids but less than d -alanine and d -aspartic acid. These d -amino acids may come mainly from bacteria.

The preparation of R(−)-β-aminoisobutyric acid using Saccharomyces cerevisiae: An unexpected result

Abstract R(−)-β-aminoisobutyric acid was prepared by the action of Saccharomyces cerevisiae on the racemic acid. The analysis was followed by ninhydrin and gas chromatographic methods for separating diastereoisomers. It was found that the elution pattern of the diastereoisomers is reversed compared to the normal protein amino acids, i.e., the SR derivatives elute before the RR derivatives.