In biochemical processes

Optically inactive starting materials can give optically active products only if they are treated with an optically active reagent or if the reaction is catalyzed by an optically active substance. The best examples are found in biochemical processes. Most biochemical reactions are catalyzed by enzymes. Enzymes are chiral and enantiomerically homogeneous they provide an asymmetric environment in which chemical reaction can take place. Ordinarily, enzyme-catalyzed reactions occur with such a high level of stereoselectivity that one enantiomer of a substance is formed exclusively even when the substrate is achiral. The enzyme ftimarase, for example, catalyzes hydration of the double bond of fumaric acid to malic acid in apples and other fruits. Only the S enantiomer of malic acid is formed in this reaction. 

The Bioreactor is the major equipment used in biochemical processes. It differs totally from a simple chemical reaction vessel. To control physical operating parameters and microbial environmental conditions, there are several influential variables ... 

When they are protonated, amines are compatible with water, a property critical in biochemical processes because it helps biological macromolecules dissolve in water. The N—H bond in an amine is fairly easy to break, so amines participate in the formation of several important classes of polymers, including nylon and proteins. 

Gressin, J. C., Online process chromatography a useful tool in biochemical processes, Biotech. Forum, 5, 38, 1988. 

In view of the importance in biochemical processes of pteridines such as folic acid, methotrexate, L-biopterin, and leucettidine <1996CHEC-II(7)679>, synthetic routes to fused pteridines continue to occupy considerable attention. Imidazo-fused pteridines have now been prepared from 3-aminopyrazine-2-carboxamides via carbodiimide intermediates. If the amido-nitrogen in the starting compound is further substituted, as in the scheme, the... 

Sections I-V of this chapter deal with the syntheses of unsaturated organic compounds playing an essential role in biochemical processes of life. Numerous polyunsaturated compounds have been synthesized in order to elucidate their physiological role, for instance in brain. However, the main impact on permanent searches for new improved methods of synthesis of isotopically labelled dienes and polyenes comes from nuclear medicine and nuclear pharmacy. The deuterium and carbon-13 labelled polyunsaturated compounds are needed as internal standards in mass spectral determinations of very low concentrations of biologically active substances in biological fluids. 

Surfactants are produced on very large or medium technical scales. Their analysis by manufacturers in products and their formulations sometimes may be complicated because of the great variety of surfactants [5]. After use as directed in aqueous systems they were discharged mainly with wastewaters. Their analysis in environmental samples then becomes quite difficult because analysis must be performed at trace concentrations with limited sample amounts after essential matrix-dependent pre-concentrations steps. In addition, homologues and isomers that exist for many surfactants, besides metabolites which are generated in biochemical processes, complicate their specific determination [6]. 

Gandour, R. D. and Schowen, R. L. (eds) (1978). Transition States in Biochemical Processes. Plenum, New York... 

In a simplified model, the metal ions equilibrate on the outside of the cell with biologically produced and excreted ligands l 2 or ligands on the cell surface L3 these reactions are followed by a slow transport step to the inside of the cell. In the cell, the metal ions may be used in biochemical processes or become trapped in inactive forms as a detoxification mechanism. (After Williams, 1983) (cf. Fig. 4.15a). (From Sigg, 1987)... 

The shape of a molecule has quite a bit to do with its reactivity. This is especially true in biochemical processes, where slight changes in shape in three-dimensional space might make a certain molecule inactive or cause an adverse side effect. One way to predict the shape of molecules is the valence-shell electron-pair repulsion (VSEPR) theory. The... 

Aldehydes, ketones and carboxylic acids are widespread in plants and animal kingdom. They play an important role in biochemical processes of life. They add fragrance and flavour to nature, for example, vanillin (from vanilla beans), salicylaldehyde (from meadow sweet) and cinnamaldehyde (from cinnamon) have veiy pleasant fragrances. 

The amount of heat generated by a reaction is the same whether the reaction takes place in one step or in several steps. Hence, A//values (and, thus, AG values) are additive. This law, also known as the Law of Constant Heat Summation, was the earliest example of the Additivity Principle, which also states that AG values are additive. In biochemical processes, especially when dealing with multiple steps as in protein folding, application of the Additivity Principle can give spurious results if the accuracy and precision of the thermodynamic parameters is insufficient. 

Because ATP and GTP hydrolysis play such central roles in biochemical processes, kinetic assays of orthophos-... 

Methodology of Zinc Determinations and the Role of Zinc in Biochemical Processes... 

Many polysaccharides besides starch and cellulose are important components of animal tissues, or play a vital role in biochemical processes. One example is chitin, a celluloselike material that is the structural component of the hard shells of insects and crustaceans. The difference between chitin and cellulose is that instead of being a polymer of glucose, chitin is a polymer of 2-deoxy-2-A-ethanamidoglucose (M-acetyl-jS-D-glucosamine) ... 

Obviously, chemical induction is of great interest, because, on one hand, it allows the induction and acceleration of non-spontaneous reaction and, intrinsically, remains the unique method by which to affect such reactions (except for reactions proceeding under the influence of photochemical and ionizing radiation). On the other hand, chemical induction plays a significant role in biochemical processes. The literal translation from Latin term interference is mutual (inter) collision (ferio), which shows the total situation. 

In biochemical processes the presence of substrates and products of both conjugated reactions in the matrix (i.e. in the same zone of the reaction system) allows finer control of their rates an increase of ADP concentration to some maximum intensifies respiration and, vice versa, ATP accumulation in sufficient amounts suppresses it. 

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