Biological Material thiols

Only a few 1-thioglycosiduronic acids have been encountered in biological material as metabolites of thiols or of compounds transformed... 

Thiol group-containing compoimds are widely distributed in industrial, urban waste, and biological materials. The analysis of thiol contents in biological molecules gives valuable information in pharmacodynamic studies of drugs and in diagnosis of some diseases. 

Several examples of the applications of polarography in these fields have been already mentioned in Chapters VI and VII, viz. determinations of benzene, toluene, naphthalene and phenols in the atmosphere, breath, blood or urine, of amino acids (with particular interest to tyrosine, tryptophane, phenylalanine, histidine and histamine), of ketoacids, ketosteroids, carbon disulphide in air and blood, ethanol, acetoin, sugars and morphine in blood, of lactic acid, mandelic acid in bile and urine, adrenaline and thyroxine in iodinated proteins and last, but not least, of thiol compounds, both soluble and bound in biological materials. A few further examples will be given here. 

The electrochemical detector is extremely sensitive, but suffers from two main drawbacks. Firstly, the mobile ( ase has to be extremely pure, in particular, free of oxygen and metal ions. Secondly, by-products of the oxidation or reduction processes are often absorbed on the surface of the electrodes and thus, if quantitative activity is required, frequent calibration is necessary. Ultimately the electrodes have to be cleaned usually by mechanical abrasion and replaced in the cell. Electrochemical detection is particularly suitable for small bore columns and possibly, in the future, LC capillary columns, due to the fact that the detector can be made extremely small in size. The detector has had a fairly wide area of application. It has been used under oxidizing conditions for the detection of phenols, hydroquinone and catechols and in particular for many compounds of biological interest including, catecholamines (35). It has been used to determine substances of industrial interest, and agricultural chemicals (36). In its oxidation form, it has been used to detect amines of various types together with i enols and thiols. It has also been used in the analysis of ascorbic acid in food and biological materials, and in the pharmaceutical industry, for the analysis of multivitamin products. 

I 2 Biological- and Field-Responsive Polymers Expanding Potential in Smart Materials Thiol response... 

Finally, some biological materials, mainly enzymes, have been introduced into carbon composite matrices and the resulting electrodes used as environmental biosensors (in addition to numerous other biosensing applications ). The main examples are based on tyrosinase (or polyphenol oxidase) for the detection of phenolic compounds or thiols, acetylcholinesterase for organophosphate and carbamate pesticides, ° ° organophosphorous hydrolase for pesticides, or bienzymatic systems for amperometric immunosensor for polycyclic aromatic hydrocarbons. ... 

The reaction of 1-amino-1-deoxyketoses, and their N-alkyl and N-aryl derivatives, with alkyl or aryl isothiocyanates (Huber et al, 1960) was studied in more detail, and new 4-(alditol-l-yl)-l-alkyl(aryl)-3-alkyl(aryl)-l,3-dihydro-2H-imidazole-2-thiones were obtained. These compounds were used as starting materials for the synthesis of OL-histidines, DL-histidine-2-thiol, and other imidazole derivatives of biological interest. 

SAM, S-adenosylmethionine, has been encountered as a biological methylating agent, carrying out its function via a simple Sn2 reaction (see Box 6.5). This material is a nucleoside derivative formed by nucleophilic attack of the thiol group of methionine on to ATP (see Box 6.5). It provides in its structure an excellent leaving group, the neutral S-adenosylhomocysteine. 

The choice of working electrode material is an important factor in amperometric detection. For catechols and similar substances, such as phenolic acids, electrodes made of glassy carbon have shown good performances. Other good detectable and biological important substances include thiols and disulfides (e.g., cysteine, glutathione, and their disulfides which... 

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