Although lowering the pK2 of neutral amino acids only weakens their concentrative uptake by Ehrlich cells, the same change greatly enhances uptake of diamino acids. This effect does not arise merely from putting the distal amino group in its uncharged form, but depends on an enhanced deprotonation of the alpha-amino group. Parallel effects are seen for the transport system for basic amino acids...

abstract        background and objective: measurement of amino acids is an important tool for metabolic studies and evaluation of patients’ clinical condition. the aim of this study was to analyze the plasma amino acids using reverse phase high performance liquid chromatography techniques (rp-hplc) with pre-column derivatization by o-phthalaldehyde (opa) in combination with 3- mercaptopropionic...

Seven D-amino acids, including D-valine, D-phenylalanine, D-leucine, D-isoleucine, D-tryptophan, D-methionine, and D-alpha-aminobutyric acid, are markedly less stimulative than the corresponding L-isomers that can stimulate the labellar sugar receptor of the fleshfly. A distinct effect of len;th of the amino acid side chain is clearly observed. Esterification and amidation of the alpha-carboxyl...

The development of syntheses providing enantiomerically pure alpha-amino acids has intrigued generations of chemists and been the subject of intense research. This report describes a general approach to functionalized alpha-amino acids based on catalytic asymmetric synthesis. Proline catalyzed Mannich-type reactions of N-PMP-protected alpha-imino ethyl glyoxylate with a variety of unmodified ke...

Male albino rats (110-120 g) were fed for 10 days on an amino acid diet low in nitrogen (nitrogen = 1.05%) devoid of valine, leucine and isoleucine and supplemented with branched-chain alpha-ketoacids (9.4%) (BCKA-diet). Pair-fed controls received an isocaloric diet (AA-diet) which contained the three branched-chain amino acids (1.4%) instead of the alpha-ketoacids (nitrogen = 1.2%). A third gr...

The unique aroma of melons (Cucumis melo L., Cucurbitaceae) is composed of many volatile compounds biosynthetically derived from fatty acids, carotenoids, amino acids, and terpenes. Although amino acids are known precursors of aroma compounds in the plant kingdom, the initial steps in the catabolism of amino acids into aroma volatiles have received little attention. Incubation of melon fruit cu...

The host-specific toxin of Helminthosporium carbonum (C(32)H(50)N(6)O(10)) was hydrolyzed by 6 n HCl to yield a number of alpha-amino acids. The common amino acids, proline and alanine, occurred in a ratio of 1:2. Two other unstable alpha-amino acids that produced lower color values with ninhydrin were also produced. One of these was tentatively identified as 2-amino-2,3-dehydro-3-methylpentano...

arginine (arg) requirements of male broilers (ross 308) reared at high altitude (2100 mabove sea level) during the 1-to 3-week period was estimated in a graded supplementationmethod, in which six diets (230 g kg-1 cp and 3200 kcal me kg-1) with arg increments of1.25 g kg-1 were applied to four pens of fifteen birds each. dietary arg content of theexperimental groups ranged from 10 g kg-1 (80% o...