Amino acids HPLC analysis

Recently, Peace and Gilani [229] reviewed chromatographic determination of amino acids. HPLC analysis of free amino acids can be a powerful tool in the control of food authenticity. Cotte et al. [230] demonstrated that HPLC analysis of free amino acids, followed by statistical processing of... 

Chlorination of Individual Amino Acids. HPLC analysis of an extract of chlorinated humic acids indicated that the chlorination products compose a highly complex mixture of organic material. Thus, the task of identification of mutagenic products of chlorination would not be simplified by the use of the humic acid model. In contrast, the amino acid model of production of mutagenic compounds can be readily simplified by the use of individual compounds as precursors. 

Figure 6. Membrane assisted condensation of amino acids. HPLC analysis (at 289 nm) of the products of the oligomerization of NCA-Trp assisted by POPC liposomes. There are several products (for reaction conditions and other details see ref. 21). It is important to notice the difference between the liposome-assisted oligomerization (A) and the control experiment, in the absence of liposomes (B). In this second case, the highest product has a oligomerization degree n = 7 in the case of liposomes we reach n = 29, although in minimal amounts.

Amino Acids HPLC Analysis Advanced Techniques... 

Period 2 Part B—Work up the dansyl hydrolysate and spot on the TLC plate with standard dansyl amino acids. Part A. 1—Work up peptide hydrolysate and prepare FMOC derivatives of amino acids for analysis by HPLC or CE. Part A.2-If applicable, develop paper chromatogram in solvent system. 

Lysine is an essential amino acid. Since lysine is a fairly acid-stable amino acid, its analysis as total lysine by the traditional hydrochloric acid hydrolysis is straightforward. Fairly recent examples for the successful determination of total lysine employing either ion-exchange (82) or reversed-phase (101) HPLC are available. 

The amino-terminal amino acid sequence analysis of each fraction revealed that every fraction was comprised of three kinds of peptides with different proportions. One of them showed the same amino-terminal sequence, G-N-I-Q-V-E-N-Q-A-I-P-D-P-, as observed in the previous experiment, and the other two peptides had shortened sequences, N-Q-A-I-P-D-P- and Q-A-I-P-D-P-, in which six or seven amino acid residues were deleted from the amino-terminal of the former sequence. However, all active fractions possessed similar amino acid compositions and, in addition, after V8 protease digestion, showed almost identical peptide mapping patterns on HPLC. 

Peptides were sequenced using either an Applied Biosystems Model 470 or 477 or a Hewlett Packard GIOOOA protein sequencer, each equipped with narrow bore RP-HPLC for on-line analysis of the PTH-amino acids. Mass analysis of peptides was performed using matrix-assisted laser desorption/ionization mass spectrometry on a KRATOS MALDl 111 with a-cyano-4 hydroxy-cinnamic acid as the matrix. 

Proteins and Amino Acids Total protein in food and feed samples is commonly determined by Kjeldahl (acid digestion/titration) or Dumas (pyrolysis) or elemental analysis.14 FIPLC can separate major proteins and furnish protein profiles and speciation information. HPLC can be used to further characterize specific proteins via peptide mapping and amino acid sequence analysis. HPLC modes used for protein include IEC, SEC, RPC, and affinity chromatography with typical UV detection at 215 nm or MS analysis. Details on protein separations are discussed in the life sciences section. 

The Pj-22 isoforms were further purified by reverse phase HPLC (separation on the basis of hydrophobicity data not shown) and subjected to amino acid composition analysis. The data are summarized in Table 1. Knowing the relative amounts of each amino acid will define an enzymatic fragmentation strategy that will permit determination of the total Pj-22 sequence. 

Microcolumn reverse-phase HPLC electrospray ionization tandem mass spectrometry (ESI-MS/MS) is a rapid and sensitive technique for the analysis of complex mixtures of peptides. This technique is used to determine the amino acid sequence of unknown peptides, to verify the structure of proteins, and to determine posttrans-lational modifications (see also the article by Beth L. Gillece-Castro). In particular, the strength of this approach is the analysis of peptides in complicated mixtures, such as amino acid sequence analysis of peptides isolated from class I and II major histocompatibility T-cell receptor complexes (Hunt et al., 1992a). 

However, the use of a HPLC separation step enabled a remarkable acceleration of the deconvolution process. Instead of preparing all of the sublibraries, the c(Arg-Lys-O-Pro-O-P-Ala) library was fractionated on a semipreparative HPLC column and three fractions as shown in Fig. 3-2 were collected and subjected to amino acid analysis. According to the analysis, the least hydrophobic fraction, which eluted first, did not contain peptides that included valine, methionine, isoleucine, leucine, tyrosine, and phenylalanine residues and also did not exhibit any separation ability for the tested racemic amino acid derivatives (Table 3-1). 

Amino acid analysis, by reverse-phase HPLC, of acid-hydrolyzed uncross-linked recombinant resilin and cross-linked recombinant resilin clearly shows the presence of dityrosine in the cross-linked sample (Figure 9.3c). Further evidence of the presence of dityrosine was obtained by UV irradiation (Xmax,ex 315 nm Xmax,em 409 nm). Dityrosine endows natural resilin with pH-dependent blue fluorescence [38] on UV irradiation. The cross-linked recombinant resilin material was similarly fluorescent, strongly suggesting dityrosine cross-links. 

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