Proteins functions, generally

Figure 25.3 Electrophoresis patterns for normal human serum, (a) Stained strip (b) densitometric scan of strip The plasma proteins function generally ...

Proteins are essential to all living systems. Proteins are macromolecules and, like all biological macromolecules, polymers (Alberts et al. 1994). The structural units of proteins (monomers) are about 20 amino acids. Although no clear line exists, proteins are generally considered to have minimal chain lengths of about 50 amino acids, corresponding to molecular masses near 5000 daltons. The most complicated proteins contain several thousand amino acids and have molecular masses of several million daltons. The functional diversity ranges from ... 

An affinity label is a molecule that contains a functionality that is chemically reactive and will therefore form a covalent bond with other molecules containing a complementary functionality. Generally, affinity labels contain electrophilic functionalities that form covalent bonds with protein nucleophiles, leading to protein alkylation or protein acylation. In some cases affinity labels interact selectively with specific amino acid side chains, and this feature of the molecule can make them useful reagents for defining the importance of certain amino acid types in enzyme function. For example, iodoacetate and A-ethyl maleimide are two compounds that selectively modify the sulfur atom of cysteine side chains. These compounds can therefore be used to test the functional importance of cysteine residues for an enzyme s activity. This topic is covered in more detail below in Section 8.4. 

Kam, N.W.S. and Dai, H.J. (2005) Carbon nanotubes as intracellular protein transporters generality and biological functionality. Journal of the American Chemical Society, 127 (16), 6021-6026. Heller, D.A. et al. (2005) Single-walled carbon nanotube spectroscopy in live cells towards long-term labels and optical sensors. Advanced Materials, 17 (23), 2793-2799. 

Before we conclude the functions of the elements and the proteome, there is a second general feature of eukaryote cells, much of which evolved from that of the prokaryotes - the types of metal-binding protein. The general supposition is that the number of folds are limited and certainly the number of metal-binding sites for any one metal ion is closely limited (see Section 4.15). We find that there are some general rules for protein-binding centres of metal ions and their geometry, mentioned only in brief in Chapters 5 and 6. 

From the realization of the amphoteric nature of proteins and the importance of [H+] in many of their functions, and as increasing numbers of enzymes were identified, it became commonplace to report their optimum pH. Corrections for non-enzymic hydrolysis of the substrates were usually made but, as was critically reviewed by Dixon and Webb (1959), from many of the results it was not possible to distinguish effects of pH on the protein in general from those on the region actually involved in interaction with the substrate. Nevertheless, many... 

Kam NWS, Dai HJ (2005) Carbon nanotubes as intracellular protein transporters Generality and biological functionality. J. Am. Chem. Soc. 127 6021-6026. 

Advances in chemical synthesis have enabled considerable sophistication in the construction of diverse compound libraries to probe protein function [61, 62). However, few general techniques exist that can directly assess binding mechanisms and evaluate ligand afEnities in a multiplexed format. To realize the full potential of combinatorial chemistry in the drug discovery process, generic and efficient tools must be applied that combine mixture-based techniques to characterize protein-ligand interactions with the strengths of diversity-oriented chemical synthesis. 

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