TOPICAL amino acid content

An example of an enzyme which has different isoenzyme forms is lactate dehydrogenase (LDH) which catalyzes the reversible conversion of pyruvate into lactate in the presence of the coenzyme NADH (see above). LDH is a tetramer of two different types of subunits, called H and M, which have small differences in amino acid sequence. The two subunits can combine randomly with each other, forming five isoenzymes that have the compositions H4, H3M, H2M2, HM3 and M4. The five isoenzymes can be resolved electrophoretically (see Topic B8). M subunits predominate in skeletal muscle and liver, whereas H subunits predominate in the heart. H4 and H3M isoenzymes are found predominantly in the heart and red blood cells H2M2 is found predominantly in the brain and kidney while HM3 and M4 are found predominantly in the liver and skeletal muscle. Thus, the isoenzyme pattern is characteristic of a particular tissue, a factor which is of immense diagnostic importance in medicine. Myocardial infarction, infectious hepatitis and muscle diseases involve cell death of the affected tissue, with release of the cell contents into the blood. As LDH is a soluble, cytosolic protein it is readily released in these conditions. Under normal circumstances there is little LDH in the blood. Therefore the pattern of LDH isoenzymes in the blood is indicative of the tissue that released the isoenzymes and so can be used to diagnose a condition, such as a myocardial infarction, and to monitor the progress of treatment. 

Topics of relevance to the content of this chapter which have been reviewed during the year include photoactive [2]rotaxanes and [2]catenanes, photochemical synthesis of macrocycles, phototransformations of phthalimido amino acids, photoaddition reactions of amines with aryl alkenes and arenes, photoreactions between arenenitriles and benzylic donors, photostability of drugs, polycyclic heterocycles from aryl- and heteroaryl-2-propenoic acids, photoreactions of pyrroles, photoamination reactions in heterocyclic synthesis, switching of chirality by light, photochromic diarylethenes for molecular photoionics and solid state bimolecular photoreactions. 

Traditionally considered of benefit to the complexion and to prolong life mei rang yan nian), lycium fruit has been consumed for 2000 years in China for these purposes in recent years it is also used successfully in the topical treatment of bums, ulcers, bedsores, frostbite, canker sores, and fumncles. Its high contents of free amino acids, P-carotene, and bioactive polysaccharides as well recent evidence of its ability to increase skin hydroxyproline levels and at the same time with no known human toxicity make it a potentially useful cosmetic ingredient. 

An interesting topic is related to the data of trace element contents in human hair. The results of analysis of trace element contents in human hair are useful for the diagnosis of some diseases. These data can also provide valuable information about the influence of environment on human health. Like the trace element analysis of serum or urine, hair analysis can provide valuable information. Contrary to the results of the analysis of serum or urine, the results of hair analysis can reflect metabolic process in the body over a period of several months. Metal ions, moreover, are permanently built into the a-helical structure of hair keratin, thereby creating chelate links with the acid and basic radicals of amino acids, as a result of which the content of some metallic elements in hair is much higher than that in other tissues. Up to now, 78 elements have been detected in human hair. 

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