Amino acids: characteristic chemical derivatives

In vitro modification of proteins, producing a variety of well-defined amino acid derivatives, can occur as a result of deliberate manipulation or by inadverent modification during isolation or subsequent handling. In either case, the derivatives, if properly identified, can provide useful information about that protein or peptide. Many are stable to acid or alkali, thus facilitating their determination, and all, at least in theory, should be recoverable from total enzymatic digests. This recovery can be facilitated if the substituent contains a radioactive nuclide or has some other prominent chemical characteristic such as absorption in the visible region of the spectrum. 

Hormones are chemically diverse, physiologically potent molecules that are the primary vehicle for intercellular communication with the capacity to override the intrinsic mechanisms of normal cellular control. They can be classified broadly into four groups according to their physicochemical characteristics (1) steroid hormones, (2) peptide and protein hormones, (3) those derived from amino acids, principally the aromatic amino acid tyrosine, and (4) the eicosanoids (fatty acid derivatives). 

As animals require specific amounts of proteins, carbohydrates, vitamins, and minerals for proper growth, plants require nutrients in the form of ions derived from the soil. Insufficient quantities of protein, or even specific amino acids of proteins, can limit growth or specific biological processes in animals. Similarly, each nutrient plays a specific role in the structure of plant cells and the enzyme and energy transfer molecules that carry out the metabolic processes of plants. Because of the unique chemical characteristics of these nutrients, other elements cannot be used as substitutes for them. 

Arrays for amino acid detection focus primarily on differentiating amino adds by their various side-chain characteristics. These differing characteristics, such as being hydrophobic, positively charged, negatively charged, and aromatic, derive from the chemical stracture of the particular side chain on an amino acid. Since amino acids have such a wide range of side chains, with various chemical characteristics, discrimination of these analytes is in certain ways simplified, especially in comparison to more subtly different analytes such as nucleotides discussed in the subsequent section. 

The two matrix representations of the protein segments, the amino acid adjacency matrix and the decagonal isometries matrix, are derived from the sequence information alone. As has been demonstrated, mathematical descriptors, dependent on the sequence information alone, have successfully revealed the underlying characteristics and patterns of given sequences. Their numerical nature also makes them easier to incorporate into a mathematical model. In addition, as has been well illustrated in chemical graph theory, when considering characterization of molecules, one can... 

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