Peptides, detection amino acids

Zhang H, Le Potier I, Smadja C et al (2006) Fluorescent detection of peptides and amino acids for capillary electrophoresis via on-line derivatization with 4-fluoro-7-nitro-2,l, 3-benzoxadiazole. Anal Bioanal Chem 386 1387-1394... 

Hydroperoxides may be determined by measuring at 290 nm (e = 44100 M cm ) or 360 nm (e = 28000 cm ) the concentration of 13 formed in the presence of a large excess of ions. The reaction may be too slow for practical purposes, unless a catalyst is present. For example, an assay for lipid hydroperoxides conducted without a catalyst may require several measurements every 6 min until the absorbance reaches a maximum. Exclusion of air from the sample cuvette is important. The method is about 1000-fold more sensitive than thiosulfate titration The iodometric method with UVD at 360 was adopted for detecting the presence of hydroperoxides derived from protein, peptide or amino acid substrates subjected to y-radiation, after destroying the generated H2O2 with catalase. ... 

To detect peptides and amino acid derivatives using the chlorine peptide spray the following procedure is carried out. Solution I (1% tert-butyl hypochlorite in cyclohexane) and solution II (1% soluble starch and 1% KI in water) are prepared. To prepare solution II starch is dissolved in boiling water first and potassium iodide is added to the cold solution. A small amount of chloroform is added to inhibit bacterial growth. 

Content of the meal also affects gastric pH. For example, a pure carbohydrate meal has no detectable effect on acidity,whereas a high protein meal matched for calorific content confirming that it is not the protein but its digestion products, the peptides, and amino acids, which are the potent stimulators of... 

Ninhydrin reagent. Most peptides and amino acids can be detected on papers by dipping the paper in a solution containing ninhydrin (or spraying the paper with this solution) and heating in an oven at 60°C for 15-60 min. Further color development will sometimes occur overnight. Various colors ranging from yellow to violet are often observed and can be used to help identify certain peptides or amino acids. 

Determination of specific peptides or amino acid composition after hydrolysis e.g., tryptic hydrolysis). In this case the big disadvantage is the possible interference from other proteins moreover, it is a laborious method and not sensitive enough to detect traces of soy. 

Fig. 9.6. Composite diagram showing the elution position of some peptides and amino acids. Chromatographic conditions column, Lichrosorb Si 60 7 fim (treated with 0.1 M copper(II) sulphate/1 M ammonia) mobile phase, (A) water/acetonitrile (10 90)-0.1 M ammonia, 1 ppm Cu " ", (B) water-acetonitrile (60 40)-0.95 M ammonia, 1 ppm Cu " ". Elution was achieved with a concave gradient of 0% B to 100% B over 70 min flow rate, 2 ml/min detection, UV at 254 nm. 1, Phe-Phe 2, Ala-Ala-Ala 3, mixture 4, Ala-Ser 5, Pro-Glu 6, Phe 7, Gly-Gly-Gly 8, Lys-Phe 9, Leu 10, Leu 11, Glu 12, Ala 13, Ser-Ser-Ser 14, Gly-His-Gly 15, Arg-Glu 16, Lys-Gly 17, Arg-Tyr 18, Pro-Gly-Lys-Ala-Arg,Lys-Lys-Gly-Glu A, hydrophobic, large peptides B, dipetides C, amino acids, hydrophilic peptides, basic peptides.

The prevalence of the carboxylate moiety in both biogenic and man-made molecules of interest makes this functional group a popular target for anion host chemistry. Needless to say, carboxylates are a major constituent of proteins, peptides and amino acids, and the expansion of proteomics begets increasing requirements for means of specific detection of such biomolecules. Other relevant examples of carboxylates include fatty acids, while many small molecule di- and tricarboxylates are implicated in key metaboUc pathways such as the citric acid cycle (e.g. citrate, succinate, fumarate and malonate). Carboxylated anthropogenic molecules include trichloroacetic acids, anionic surfactants and S-lactam antibiotics. 

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