Amino acids preservation

Citric acid is used in carbonated beverages to provide tartness, modify and enhance flavors, and chelate trace metals. It is often added to jams and jellies to control pH and provide tartness. It is used in cured and freeze-dried meat products to protect the amino acids (qv) and improve water retention. Bakers use it to improve the flavor of fmit fillings in baked goods. Because citric acid is a good chelator for trace metals, it is used as an antioxidant synergist in fats and oils, and as a preservative in frozen fish and shellfish (7) (see Antioxidaisits). 

A hybridoma can live indefinitely in a growth medium that includes salts, glucose, glutamine, certain amino acids, and bovine serum that provides essential components that have not been identified. Serum is expensive, and its cost largely determines the economic feasibihty of a particular ciilture system. Only recently have substitutes or partial replacements for serum been found. Antibiotics are often included to prevent infection of the culture. The pH, temperature and dissolved oxygen, and carbon dioxide concentration must be closely controlled. The salt determines the osmotic pressure to preserve the integrity of the fragile cell. 

Lesk and Chothia did find, however, that there is a striking preferential conservation of the hydrophobic character of the amino acids at the 59 buried positions, but that no such conservation occurs at positions exposed on the surface of the molecule. With a few exceptions on the surface, hydrophobic residues have replaced hydrophilic ones and vice versa. However, the case of sickle-cell hemoglobin, which is described below, shows that a charge balance must be preserved to avoid hydrophobic patches on the surface. In summary, the evolutionary divergence of these nine globins has been constrained primarily by an almost absolute conservation of the hydro-phobicity of the residues buried in the helix-to-helix and helix-to-heme contacts. 

Write the complete Lewis structure for each of the following compounds (a) formaldehyde, HCHO, which as its aqueous solution formalin is used to preserve biological specimens (b) methanol, CH3OH, the toxic compound also called wood alcohol (c) glycine, H2C(NH2)COOH, the simplest of the amino acids, the building blocks of proteins. 

The fifteen samples analyzed for amino acid composition were compared to a human type 1 collagen standard. There are no significant differences in amino acid composition among these samples, which range in age from stillbirth to adult. Analytical error is 10%. All samples show the typical composition of type 1 collagen (Table 1.1). Based on these results there is no reason to suspect differential preservation of specific amino acids in the small bones of infants in comparison to bones of adults and older children. 

Since it is possible to differentiate well-preserved from badly preserved collagen through amino acid analysis and gel electrophoresis, it is also possible to determine which bone samples are likely to give erroneous isotopic ratios. At least for 8 C, it should be possible to estimate the in vivo isotopic signature by correcting the changed amino acid concentrations of the collagen extract. This way, a reasonable approach to the reconstruction of pale-odiet should be possible. 

Part of the diet consists of fats, which are triglycerol esters of fatty acids (FAs). The FAs from digestion of ingested fats can be metabolized in a variety of pathways. Fragments of the original FAs are preserved in these processes and can be utilized in the biosynthesis of other molecules. It is important to note that, during metabolism, almost all FAs are broken down into two-carbon units. The only exceptions are FAs with odd numbers of carbon atoms these are relatively rare in the diet. It ean be shown further that there is a partial barrier to the incorporation of FA-derived carbon into the amino acids which constitute collagen. 

While a number of drugs, e.g. a-methyl dopa, inhibit the enzyme they have little effect on the levels of brain DA and NA, compared with inhibition of tyrosine hydroxylase and they also affect the decarboxylation of other amino acids. Some compounds, e.g. a-methyl dopa hydrazine (carbidopa) and benserazide, which do not easily enter the CNS have a useful role when given in conjunction with levodopa in the treatment of Parkinsonism (see Chapter 15) since the dopa is then preserved peripherally and so more enters the brain. 

Amino acids are provided to preserve or replete lean body mass and visceral proteins and to promote protein anabolism and wound healing. 

Amino acids are the building blocks of body proteins. There is no excess storage form of protein in the body, so amino acids are an essential component of the PN admixture. Amino acids are provided to preserve or replete lean body mass and visceral proteins and to promote protein anabolism and wound healing. Amino acids are a source of calories with a caloric value of 4 kcal/g. 

---