Acid-labile amino acid precursors in the Murchison meteorite. 1: Chromatographic fractionation.

The amino acid content of a hot water extract of the Murchison meteorite can be increased by over 100 per cent by subjecting the extract to acid hydrolysis. The acid-labile compounds in the extract that account for this increase were fractionated by column chromatography on a cation exchange resin. Seventy mole per cent behaved as neutral or acidic compounds and were eluted from the column with an initial water wash. The remaining 30 mole per cent (basic precursors) were retained on the column and were eluted with the free amino acids by aqueous NH4OH. The acid-labile amino acid precursors in the water eluate could be retained and further fractionated on an anion exchange column, indicating that they are acidic compounds.     

Acid-labile amino acid precursors in the Murchison meteorite. II: A search for peptides and amino acyl amides.

The basic fraction of the acid-labile amino acid precursors found in hot water extracts of the Murchison meteorite was treated with ninhydrin under conditions that give destruction of free amino acids but allow nearly complete recovery to peptides and amino acylamides. After this treatment and a subsequent acid hydrolysis, the amount of amino acids found corresponded to less than 30 per cent of the precursor content of the basic fraction. Since only 30 percent of the total extract precursors are found in the basic fraction, these results indicate that such compounds, if present, account for no more than 9 mole per cent of the total acid-labile amino acid precursors of the meteorite hot water extract.     

氨基酸前体对棘白霉素B发酵合成的影响

以构巢曲霉(Aspergillus nidulans)发酵生产酯肽类化合物棘白霉素B,研究棘白霉素B己肽环结构的前体性氨基酸对产物的代谢影响,显示出脯氨酸、鸟氨酸、苏氨酸在发酵48 h 补入,对发酵代谢有促进作用.利用响应面统计学方法进行前体及有机氮源配方优化,得出优化配方:脯氨酸4.55 mg/mL,鸟氨酸1.85 mg/mL,苏氨酸0.97 mg/mL,棉籽粉2.62％,摇瓶发酵水平达到3 270μg/mL,较原水平提高30.2％.新工艺在50 L罐上放大,发酵水平进一步提高至3 520 μg/mL,显示出良好的工业应用前景.     

Uptake of amino acids and nucleic acid precursors by regenerating rat liver

1. At 0.5-1.0h after partial hepatectomy the intracellular acid-soluble fraction of rat liver took up twice as much radioactivity from [(3)H]orotic acid, [(3)H]uridine and [(3)H]thymidine as did similar fractions from sham-operated animals. This increase in penetration was not prevented by adrenalectomy or actinomycin, both of which decreased precursor uptake into nuclear RNA at this time. The increase in entry was still shown by thymidine at 22h after operation, at the height of the S period. Adenine penetration was not increased 1h after partial hepatectomy. 2. Plasma concentrations of ornithine and possibly methionine, tyrosine and lysine were raised 1.5h after partial hepatectomy. [(3)H]Lysine entry into regenerating liver at this time was increased by 60%; [(3)H]valine uptake was unaffected. Intracellular amounts of tyrosine, phenylalanine and ornithine in the liver were also increased. 3. The relation of these events to the start of liver regeneration is discussed.     

The amino acid precursors and odor formation in society garlic (Tulbaghia violacea Harv.)

Identification and isolation of (R(S)R(C))-S-(methylthiomethyl)cysteine-4-oxide from rhizomes of Tulbaghia violacea Harv. is reported. The structure and absolute configuration of the amino acid have been determined by NMR, MALDI-HRMS, IR, and CD spectroscopy. Its content varied in different parts of the plant (rhizomes, leaves, and stems) between 0.12 and 0.24 mg g(-1) fr. wt, being almost equal in the stems and rhizomes. In addition, S-methyl- and S-ethylcysteine derivatives have been detected in minute amounts (<3 microg g(-1) fr. wt) in all parts of the plant. The enzymatic cleavage of the amino acid and subsequent odor formation are discussed. 2,4,5,7-Tetrathiaoctane-4-oxide, the primary breakdown product, has been detected and isolated for the first time.     

Biosynthesis of hyperforin and adhyperforin from amino acid precursors in shoot cultures of Hypericum perforatum

Hyperforin and adhyperforin contribute to the antidepressant effects of Hypericum perforatum. The involvement of branched-chain amino acids in the biosynthesis of hyperforin and adhyperforin was demonstrated in H. perforatum shoot cultures. L-[U-(13)C(5)]Valine and L-[U-(13)C(6)]isoleucine, upon administration to the shoot cultures, were incorporated into acyl side chain of hyperforin and adhyperforin, respectively. Feeding the shoot cultures with unlabelled L-isoleucine at a concentration of 2mM induced a 3.7-fold increase in the production of adhyperforin. The addition of 3mM L-threonine, a precursor of isoleucine, stimulated a 2.0-fold increase in the accumulation of adhyperforin. The administration of L-valine at concentrations of 0-5mM had no stimulating effect on the hyperforin production in H. perforatum shoot cultures.     

The formation of amino acid precursors in the reaction of atomic carbon with water and ammonia at 77 K

When atomic carbon is condensed on a surface at 77 K containing ammonia and water, glycine, N-methylglycine, alanine, β-alanine, aspartic acid and serine are generated. It is postulated that these reactions may mimic those which occur when an extraterrestrial carbon atom condenses on a frozen surface coated with water and ammonia and may provide a route to extraterrestrial amino acids. Experiments designed to elucidate the mechanisms of amino acid formation under these conditions have been carried out.