Amino acids tests

Recovery 93% from amino acid test mixture. b Recovery 100.6% from amino acid test mixture. e Recovery 99.2% from amino acid test mixture. d Decarboxylase-CO method (108, 106). 

Dry the sheet again and keep on the vapor of concentrated HCl. Identify the red spots in comparison with a chromatogram of DABTH amino acid test mixture and determine migration relative to the bluish spots of the markers (schematic drawing of a 2 x 2-cm TLC plate is given in Fig. 3.1). 

Calfskin gelatin (60 bloom strength), bovine casein and the amino acids tested (phenylalanine, leucine, tyrosine, tryptophan) were all purchased from Sigma Chemical Company (St. Louis, MO). 

It may also be necessary to determine the free fatty acid content of oily materials as an index of rancidity, since this will affect palatability. Analyses of amino acids can only be conducted in specialized laboratories and are conducted less frequently. Instead most feed mixers (including commercial feed manufacturers) use procedures such as prediction equations based on the protein content of the sample to predict the content of important amino acids. Tests for minerals are more routine and are offered by most laboratories. Tests for vitamins are offered by certain laboratories but are not very frequent since commercial feed manufacturers often disregard any vitamin contribution from the dietary ingredients and add all the necessary vitamins in the form of a supplement. 

Incubations of crude pH 5 Supernatant with several C14-aminoacyl sRNA preparations, differing only in the nature of the C14-amino acid, showed that all amino acids tested were incorporated into ribosomal protein. With combined transferases I and n, the results presented in Table VII indicated that all of the amino acids tested were also incorporated in the presence of these purified fractions (8). When either of the transferases was omitted from these incubations, little amino acid transfer was observed with any of the C14-aminoacyl sRNA preparations. Variations in total amounts of C14 incorporated, as shown here, are probably due to variations in the specific radioactivity of the various sRNA-bound amino acids used. These purified transferase preparations did not catalyze the incorporation of free amino acids into sRNA or ribosomes. 

The method described above and outlined in Scheme 1 is particularly suitable for the synthesis of symmetrically substituted NDIs but originally it was of limited value for the synthesis of naphthalenemonoimide (NMI) and N-desymmetrised NDI derivatives. This is due to the difficulty of selective imide formation in a cross-conjugated dianhydride containing two equivalent electrophilic sites such as 1,4,5,8-naphthalenetetracarboxylic dianhydride (NDA). For all the aliphatic amines and amino acids tested, carrying out the reaction for 5 min at 140 °C only led to the formation of a 1 2 1 statistical mixture of dianhydride monoimide diimide (Table 1). 

Among the various amino acids tested, cysteine and aspartic acid were found to strongly enhance the RLU of RL-1 (Table 1), whereas arginine showed an adverse effect on the luminescence, as reported previously (Table 2). The effects of the amino acids were independent of their isomeric forms (D-type and L-type). Chitosan also enhanced the RLU of RL-1. 

Scoliosis has been reported after feeding fish a tryptophan-deficient diet.1617 Using tryptophan-deficient and nondeficient synthetic amino acid test diets, Kloppel and Post16 reported that scoliosis was observed in the tryptophan-deficient rainbow fish after 1 week of feeding. Histological studies of scoliotic fish revealed hyperemia, disorganization of myomere septa and protrusions of the fibrous matrix sheath, which invests the notochord. Conditions returned to normal within 1 week upon replacement of tryptophan in the diet. 

Further information was gleaned from feeding [l- C]glucose. ° This compound was found to label only C-1 and C-10 of the C7N unit, a labelling pattern which is similar to that observed in shikimic acid (191) formed from [1- C]glucose. Neither shikimic acid, however, nor the labelled aromatic amino-acids tested were found to be precursors for the C7N unit of rifamycin S. This does not, of course, exclude earlier intermediates on the shikimate pathway and it was suggested that 3-dehydroquinate (189) or 3-dehydroshikimate (192) may be the key intermediate in the biosynthesis of this unit in rifamycin S (193). 

As to the applications of proline, it can modify the surface of palladium on charcoal to give an enantioselective hydrogenation catalyst (Section D.2.3.1.). Forming amides with aromatic carboxylic acids, proline has served as an auxiliary in the enantioselective Birch reduction of the aromatic system (Section D. 1.1.1.3.1.). An interesting application is the catalysis of the aldol-type cyclization of triketones. Among the amino acids tested, it is often the best choice for high enantiomeric excess3 4. 

This section on chemical factors related to quality in soybeans is divided into subparts on protein and oil, fatty acids, amino acids, tests for protein, carbohydrates and sugars, and other factors that are often discussed, particularly as soybeans are enhanced for more specific end uses. The other factors include tests for fiber, phosphorus, to-copherols, and isoflavones. The intent is to discuss the importance of these factors, to provide background, and, because of increased use of near-infrared spectroscopy as a measurement method for whole and ground soybeans, to include that technology in the discussion of test measurements. While many primary and other methods for measuring these chemical factors are available, this chapter does not intend to cover those methods. 

Effects of amino acids The effects of 18 kinds of amino acids on crystal appearance are summarized in table 4. Among these amino acids tested, only leucine and tryptophan affected the change in crystal form from pillars to thin plates at concentrations relative to Lmore than 3%. These two amino acids are hydrophobic, so they might interact with the Lrphenylalanine skeleton in the crystal structure of di-L-phenylalanine sulfate monohydrate and are supposed to suppress growth in the a-axis direction. Isoleucine, valine and tyrosine which are analogous... 

The so-called activation of lipase action by proteins such as egg albumin or gelatin (322), by serum (65), and by inactivated serum (323) is probably primarily the restilt of better emulsification of the substrate. Amino acids and polypeptides, especially those containing glycine, are reported as very effective activators (324). Of several amino acids tested, histidine was found to be the most effective and more so than histamine (325, 326). The activation of lipase action by gall bladder extracts may also be a result of amino acids present in the extract (327). Extracts of small intestine or pancreas of the chick lost from a third to a half of their lipase activity after 2 hours of dialysis, and the activity was partially restored by ad tion of histidine or ascorbic acid (328). Wills (280), however, was unable to activate a preparation of purified lipase by histidine or any other amino acid tested, but found that histidine and several other amino acids were excellent protectors of lipase against the toxic effects of small amounts of metals such as Cu++. He concluded that amino aeid activation effects might be explained on this basis. 

Table 5, Pair-wise comparisons of amino acids, tested at 0.01 M. 

Among many L-amino acids tested, only L-valine and L-a-amino-butyric acid can replace L-alanine in MDP to give enhanced adjuvant active analogues (76). 

This method, although requiring longer reaction times than the symmetrical method, results in products virtually free of impurities arising horn enantio-merization and dipeptide formation (6). It involves formation of a mixed anhydride between an Fmoc-amino acid derivative and 2,6-dichlorobenzoyl chloride (DCB) in DMF/pyridine (Figure 3). This anhydride effects esterification of resin-bound hydroxyl groups in yields of typically > 70% in 18 h. Levels of D-isomer and dipeptide formation for most amino acids are typically less than 1%, with 5-acetamidomethyl cysteine giving the most enantio-merization (6.5% D-isomer) of the amino acids tested (8). 

The effect of addition of amino acids to medium 3 (which already contains aspartate, arginine, and histidine as nitrogen sources) was studied by Cheng et al. (76). Of 18 amino acids tested at 1 g/liter, only L-lysine showed a marked stimulation of both volumetric and specific rapamycin production. Its effect was maximal at 10 g/liter, the highest concentration examined. Lysine stimulation is probably due to its conversion to pipccolic acid, a precursor of rapamycin (58). Suppression of rapamycin production was observed with L-methionine and L-phenylalanine. Since methionine is a rapamycin precursor (20), it is peculiar that it interferes with rapamycin formation. However, for some unknown reason, methionine often suppresses formation of antibiotics for which it acts as precursor (77-80). One possibility for phenylalanine suppression of rapamycin formation was considered to be feed-back inhibition of shikimic add formation, since shikimate is a precursor of rapamycin (20), However, in a recent study (81) demonstrating stimulation of rapamycin biosynthesis by exogenous shikimate (57 mM), it was also shown that shikimate does not reverse phenylalanine interference. 

Of several amino acids tested, methionine is one of the more effective in stabilizing chromium(III) reaction mixtures, but its action is strongly dependent on concentration, the effect of which is shown in Fig. 2 and Table 2. 

The ability to oxidize L-amino adds is widespread among bacteria, but the enzymes responsible have not been well characterized. Proteus vulgaris is able to oxidize a large series of L-amino acids, but on storage at 0 C. loses the ability to oxidize 9 out of 20 amino acids tested. The relative rates of oxidation of the other 11 amino adds do not remain constant. An active cell-free preparation was obtained, but it is not known how many amino acid oxidases may exist in these organisms. ... 

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