Proteins, classes derived

For the most part, plastics are man-made since very few plcistlcs are natural, i.e.- nature-made. Natural plastics include large molecular-wei t proteins and similar molecules. Man-made plastics can be classified as either thermoplastic or thermosetting. Each class derives its physical properties from the effects of application of heat, the former becoming "plastic" (that is- it becomes soft and tends to flow) while the latter becomes less "plastic" and tends to remain in a softened state. This difference in change of state derives from the actual nature of the chemical bonds in the polymer. Thermoplastic polymers generally consist of molecules composed of many monomeric units. A good example is that of polyethylene where the monomeric unit is -(CH2-CH2)-. The molecule is linear... 

Figure 33.22. Presentation of Peptides from Cytosolic Proteins. Class I MHC proteins on the surfaces of most cells display peptides that are derived from cytosolic proteins by proteolysis.

Also see color figure.) Major histocompatibility complex (MHC) proteins class II. The MHC class 11 proteins bind and present peptides that are synthesized outside the infected cell, i.e., peptides that are derived from proteins of the infecting organisms, bound to their specific T-cell receptors (TcRs). Interaction and stimulation of T-cell proliferation occurs with CDA" " T cells (Figure 35-16). The figure is derived from the coordinates published in the Protein Data Bank file 1A6A. 

Together with the protein classes BFP and CFP, also the first yellow fluorescent proteins (YFPs) were originally derived form Aequorea GFP by introduction of amino-acid exchanges at positions 65 (the first amino-acid of the chromophore) and 203 [51]. In fact, these mutants were rationally designed based on crystal structure of GFP in order to create a fluorescent protein sufficiently different in its fluorescence properties to allow for double-labeling experiments, FRET and other experimental applications. 

Isothiocyanate derivatives of stilbene sulfonates have been utilized with marked success as affinity labels for an anion transport protein of the erythrocyte membrane by Rothstein and his associates, - and glucosyl isothiocyanate has been employed to label a glucose transport protein of the human erythrocyte membrane. Both proteins fall in the 90,000-100,000 dalton range (band 3 in the terminology of Fairbanks et oZ. ). In both cases, transport has been reconstituted using phospholipid vesicles and a band 3 preparation - after aflBnity labeling with the appropriate isothiocyanate had provided preliminary evidence that this protein class might be involved in transport. 

Other major lipid classes in the fatty acyl category include fatty add esters, such as wax monoesters and diesters and the lactones. The fatty ester class also has subclasses that include important biochemical intermediates, such as fatty acyl thioester-CoA derivatives, fatty acyl thioester-acyl carrier protein (ACP) derivatives, fatty acyl carnitines (esters of carnitine), and fatty adenylates, which are mixed anhydrides. Fatty alcohols, fatty aldehydes, and fatty amides represent further subclasses, the last sometimes showing interesting biological activities in various organisms. 

Proteins are broken down into by hydrolysis into 20 different monomer units known as amino acids. Proteins comprise the largest percentage of organic molecules in the body. The term protein is derived from the greek word proteios meaning the first place. They are nitrogen containing macromolecules. They are 20 in number and can be divided into various classes and these perform a variety of... 

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