Subject biological function

Proteins are the indispensable agents of biological function, and amino acids are the building blocks of proteins. The stunning diversity of the thousands of proteins found in nature arises from the intrinsic properties of only 20 commonly occurring amino acids. These features include (1) the capacity to polymerize, (2) novel acid-base properties, (3) varied structure and chemical functionality in the amino acid side chains, and (4) chirality. This chapter describes each of these properties, laying a foundation for discussions of protein structure (Chapters 5 and 6), enzyme function (Chapters 14-16), and many other subjects in later chapters. 

Macrocyclic polyamines may be viewed as an extended form of linear polyamines 13-161 with one less degree of saturation. Polyamines with lower degrees of saturation, have important biological functions. Compounds such as macrocyclic polyimines 171 and porphyrines 18), function as 02 carriers and activators, promote photosynthesis, form the basic structure of vitamine B12, etc., and for these reasons have been subjects of intense investigation. 

Carbohydrates are the first major class of biomolecules we ll discuss. We ll see in this chapter what the structures and primary biological functions of carbohydrates are, and then in Chapter 29, we ll return to the subject to see how carbohydrates are biosynthesized and degraded in organisms. 

Recent advances in mass spectrometry (MS) technology have provided researchers with an unparalleled ability to identify the types and patterns of secondary biochemical modifications found on proteins in living cells. Matrix-assisted laser desorption/ionization-MS (MALDI-MS) analyses have shown, for example, that HMGA proteins in vivo are simultaneously subject to complex patterns of phosphorylation, acetylation and methylation and that, within the same cell type, different isoforms of these proteins can exhibit quite different modification patterns [33]. Furthermore, these in vivo modifications have been demonstrated to markedly alter the binding affinity of HMGA proteins for both DNA and chromatin substrates in vitro [33]. Nevertheless, due to their number and complexity, it has been difficult to determine the actual biological function(s) played by these biochemical modifications in living cells. 

Although the real biological function of SOD continues to be a subject of debate (Fee, 1982), the high degree of conservation of many of these residues, particularly of those in the electrostatic loop, argues for dis-mutation of O2 as a significant function (Tainer et al., 1983 Getzoff et al., 1983). 

Discussion in this section is confined to the matter mentioned in the introduction, which has provided such a fresh and energetic impetus to this whole subject, namely the direct and quantitative correlation between the amounts of several specific and identifiable photoproducts formed in the photolysis of nucleic acids and the amount of inactivation of the nucleic acid biological function. This specific area, however, is one which has drawn much attention, and to which several of the recent reviews are devoted.8,10,113"90 There is little need to extend these excellent articles, and so a comprehensive survey of the literature will not be attempted here, but merely a summary and interpretation. 

The ongoing research into the structure and mechanism of flavoenzymes has been the subject of several recent excellent reviews The proceedings of six symposia held at intervals over the past 16 years provide an overall perspective on the progress of flavoenzyme research over this time period. The intent of this article will be to focus directly on the chemical and physical properties of the semiquinone form of flavin coenzymes to the extent that current knowledge permits, from the point of view of both model system studies and from existing knowledge of their properties in flavoenzyme systems. For an in-depth treatment of flavin and flavoenzyme redox properties in which the oxidized and hydroquinone forme as well as the semiquinone form are discussed as related to their biological function, the reader is refered to the article by F. Muller in this volume. 

The target of singlet oxygen in vivo has been the subject of a huge number of studies as it has the potential to change chemical reactivity, and hence biological function, at many sites. Unsaturated fatty acids, for example, are excellent targets [316] and peroxidation of cell membranes is probably... 

Phosphate esters, particularly AMP, ADP and ATP, have vital biological functions and this fact has generated intense interest in their reaction mechanisms. Subtle stereochemical experiments, such as the use of isotopically chiral compounds, have been important and, since all biological phosphorylation reactions appear to involve metal ion catalysis, the stereochemistry of phosphate ion coordination has also been subject to much attention.229,230 Apart from its biological significance, this work has revealed some interesting contrasts with the stereochemistry of ligand systems in which saturated carbon units link the donor atoms. 

Many biological functions have been attributed to complex carbohydrates, but the subject is still mainly a matter of speculation. It is in this direction that future research will put increasing effort, based on the progress in isolation and characterization methods, as well as in biosynthetic studies. We shall refer to some of the postulated functions, together with supporting experimental evidence. 

Polynomial equations are not rare in chemical/biological engineering problems, they are typically met in most local stability problems. However, nonalgebraic or transcendental equations are more common in our subject. A function in one variable x is called transcendental, if it is not merely a polynomial in x, nor a ratio of polynomials (called rational function), but contains nonalgebraic transcendental expressions in x, such as... 

This collection of papers is a record of the proceedings of a symposium on the chemistry, metabolism, and biological functions of glycolipids. It is also a review of some topics presented at an earlier meeting on the same subject, held in Honolulu, Hawaii in October, 1977 under the auspices of the Japan-United States Science Exchange Program. 

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