Amino acids assays

In this work we discuss some bioanalytes such as amino acids assay by electrokinetic microfluidic chip with ECE detection. 

Part 1 of this chapter is intended to provide background material for the analytical procedures described later in this chapter for amino acids and peptides, but it also provides a broad survey of the topic that can be read in isolation from the analytical context. The derivatisation of amino acids is the basis of many of the sensitive analytical amino-acid assay procedures in current use and this chapter covers the normal profile of reactions of the amino and carboxy groups, knowledge of which is an essential prerequisite for appreciating the analytical context. Reactions of peptides are also covered here (e.g. peptide and protein hydrolysis is covered in Section 4.4.7), though the coverage is restricted in scope because parts of this topic are discussed in Chapter 5, where it is relevant to sequence-determination procedures (see also Barrett, 1985). 

In some cases the quantities p(/ Ci t), and m yielded by analysis of titration curves may furnish special clues to the structure of particular proteins. For example, if ordinarily dissociable groups participate in formation of intramolecular bonds abnormal values for their intrinsic dissociation constants may result, or their number may even appear to be smaller than that found by amino acid assay. Examples will be furnished in the later sections on stoichiometry and on unreactive prototropic groups. 

Throughout this review the amino acid assays referred to are those tabulated by Tristram (1953), unless otherwise indicated. 

With collagen (Bowes and Kenten, 1948) the number of groups dissociating in the region of pH attributed to e-ammonium groups is less than the lysine content from amino acid assay hence the possibility that some of these groups are unreactive must be considered, especially since lysine assays are more often low than high. 

For samples containing several substrates, a preliminary separation should be considered or the total must be determined. In the case of L-amino acid assay the use of decarboxylating enzymes acting selectively on different amino acids is an attractive possibility, and enzyme electrodes of this type are known for L-tyrosine, L-phenylalanine, and L-tryptophan. These sensors will be coupled with a carbon dioxide base sensor. 

Similar to the toxicity of the mebendazole Polymorph toxicity due to co-crystallization was investigated recently. Cases of renal failure in cats and infants were attributed to the melamine added to pet foods and baby formulas to increase the amino acid assay based on nitrogen content. Melamine is suspected to form a 1 1 co-crystal with cyanuric acid in vivo via strong N-H- O hydrogen bonds, which is the cause of renal toxicity due to its complete insolubility in water. Disruption of amino acid metabolism from increased melamine content could be another reason for renal failure. ... 

When Severo Ochoa left the Biochemistry Department at New York University I had to search for another mentor and I was fortunate to be able to continue my graduate work with Albert Keston. While developing the isotope derivative method for amino acid assay we showed for the first time that hydroxyproline was uniquely present in collagen. This observation made a great impression on me. Furthermore, I had the good fortune while at New York University Medical School to meet and to get to know the late Joseph Bunim. It was from him that I learned about the role of collagen in connective tissue and also about collagen diseases. 

Devall AJ, Blake R, Langman N, Smith CG, Richards DA, Whitehead KJ. Monolithic column-based reversed-phase liquid chromatography separation for amino acid assay in microdialysates and cerebral spinal fluid. J Chromatogr B Anal Tech Biomed Life Sci 2007 848 323-8. 

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