Alteration of tissue levels of 13C in pigs by natural abundance 13C labeling of diets.

A study was conducted to determine the feasibility of using differences in the natural abundance of dietary 13C as a means of in vivo labeling. Four female pigs were fed a C3 plant diet (barley, soybean meal and alfalfa) and four were fed a C4 plant diet (corn and corn gluten meal). The pigs were continually fed the diets from 8 wks of age to maturity and through pregnancy until they had themselves produced offspring. The resulting piglets were sacrificed at various time intervals (0 to 165 days) after switching either the piglets or their mothers' to the opposite diet. Changes in the delta 13C levels in samples of milk and tissues following the diet change were monitored by isotope ratio mass spectrometry. The differences in the delta 13C content of the two diets was 12.9 parts per mil (/1000). After piglets born to a sow fed the C3 diet were switched at one day of age to a surrogate sow fed the C4 diet, tissue delta 13C levels of the piglets were nearly identical to the diet of the surrogate sow by 11 days while those switched from C4 to C3 grew more slowly and differed from the diet by 2-5/1000. When the mothers diet was switched, 15-20 days later the delta 13C in the milk had changed by only 2-3/1000, indicating that the body rather than the diet was the primary source of carbon in the milk. At 28 days after the piglets diet was switched at weaning, the tissue delta 13C had changed by 8.4/1000 (C4 to C3) and 2.9/1000 (C3 to C4). The delta 13C level in the liver changed more rapidly than in the muscle or fat and the rate of change was also influenced by the size and growth rate of the pig.

Dating pleistocene archeological sites by protein diagenesis in ostrich eggshell.

Eggshells of the African ostrich (Struthio camelus), ubiquitous in archeological sites in Africa, have been shown by laboratory simulation experiments to retain their indigenous organic matrix residues during diagenesis far better than any other calcified tissue yet studied. The rate of L-isoleucine epimerization to D-alloisoleucine follows reversible first-order kinetics and has been calibrated for local temperature effects and used to estimate the age range of stratified archeological sites. Age estimates are consistent with radiocarbon dates from several stratified archeological sites. With adequate calibration, this technique can provide accurate ages to within 10 to 15 percent for strata deposited within the last 200,000 years in the tropics and the last 1,000,000 years in colder regions such as China.

Amino acids in a carbonaceous chondrite from Antarctica.

A carbonaceous chondrite from the Antarctic, referred to as the Allan Hills meteorite 77306, appears to be free from terrestrial organic contamination. The presence of both protein and non-protein amino acids and an equal abundance of D- and L-enantiomers of amino acids, is testimony to the extraterrestrial nature of these compounds.

Separation of D and L amino acids by liquid chromatography: use of chiral eluants.

An aqueous eluant containing a chiral copper-proline complex effects the separation of underivatized amino acid enantiomers on an ion-exchange column. The stereoselectivity is ascribed to differences in stability of the diastereomeric amino acid-copper compexes formed in solution. A simple change in the chirality of the eluant reverses the order of the enantiomer elution. For detection and quantification of picomole amounts of amino acids, the eluant is monitored for fluorescence after reaction with o-phthalaldehyde, a reagent insensitive to proline but highly sensitive for amino acids containing a primary amino group.

O-phthalaldehyde: fluorogenic detection of primary amines in the picomole range. Comparison with fluorescamine and ninhydrin.

O-Phthalaldehyde, in the presence of 2-mercaptoethanol, reacts with primary amines to form highly fluorescent products. Picomole quantities of amino acids, peptides, and proteins can be detected easily. o-Phthalaldehyde is five to ten times more sensitive than fluorescamine and is soluble and stable in aqueous buffers.

Amino Acid composition of planktonic foraminifera: a paleobiochemical approach to evolution.

A unique, species-specific amino acid composition is identified with each of 16 species of planktonic Foraminifera isolated from the tops of deep-sea sediment cores. This amino acid pattern appears to directly reflect the genotype. The total amino acid content ranges from 2.0 to 4.2 micromoles per gram of calcified tissue or 0.02 to 0.04 percent by weight. Analyses of two Early Miocene species indicate that characteristic compositional differences are sufficiently well preserved over geologic time to determine phylogenetic affinities among extinct species living at least 18 million years ago.

Racemization of amino acids in marine sediments.

Isoleucine, one of several amino acids isolated from a suite of welldated deep-sea cores, shows a progressive increase in the degree of racemization with the age of the sediment. Amino acids in sediments show an initial rate of racemization almost an order of magnitude faster than the rate observed for free amino acids at a comparable pH and temperature. The observed kinetics depend on a variety of diagenetic processes, but it appears that the ratio of alloisoleucine to isoleucine is a reliable indicator of age for samples less than 400,000 years old; for older samples the results are more ambiguous. Isoleucine is racemic in samples older than about 15 x 10(6) years.

Evidence for compounds hydrolyzable to amino acids in aqueous extracts of apollo 11 and apollo 12 lunar fines.

Hydrolyzates of aqueous extracts of Apollo 11 fines, an Apollo 12 trench sample, and an Apollo 12 surface sample have been analyzed on an ultrasensitive amino acid analyzer. The total content of amino acids recovered ranged from 20 to 70 parts per billion of lunar soil. Amino acids are not recovered by the direct hydrolysis of lunar fines, presumably because of decomposition in the presence of the large excess of lunar mineral. As judged by retention time, glycine is the dominant amino acid found; alanine is secondarily present in each case in the profile. Only a few amino acids have been recorded in each analysis. The pattern is relatively consistent in the samples from the three locations; the pattern from either hydrolyzed or unhydrolyzed extracts differs markedly from that of hydrolyzed or unhydrolyzed handprints. The evidence is not consistent with contamination of the kind expected by many investigators.

Bio-organic compounds and glassy microparticles in lunar fines and other materials.

Acid hydrolyzates of aqueous extracts indicated: glycine, alanine, glutamic acid, serine, aspartic acid, threonine, and I-diaminopropionic acid. The sources of these amino acids may be terrestrial contaminants, fuel exhaust products, or indigenous lunar material. The lunar particles found in the sample include: (i) spherules, rotational ellipsoids, dumbbells, tear-drops, rings, and crescents which have (ii) diameters of 0.1 to 500 microns; (iii) budlike features on the particles; and (iv) chemical inhomogeneity (electron probe). Some of the processes and results inferred for the moon have been simulated by the electron beam and low pressure of the electron microscope. Basalt (Kilauea-lki) and chondrite (Orgueil) have been found to behave similarly.