Chemistry, protein chemical modifications

Another popular series of organic reagents for protein chemical modification is the isothiocyanates. They have found numerous applications in peptide and protein chemistry [92]. The best known examples are phenyl isothiocyanate 54 (Edmaris sequencing reagent) and fluorescein isothiocyanate 55. 

The subject of protein chemistry is too large to be surveyed systematically in one chapter. Various examples of chemical modifications are covered nonsystem-atically throughout this volume in discussions of individual enzymes and methods. To aid in locating these examples, some are listed in Table 9.1. 

Protein chemistry is an extensive and highly developed area of organic chemistry that deals with the chemical reactions of proteins. Much of this chemistry concerns reactions that occur in aqueous solution at ambient temperatures and neutral pH, that is, under conditions where proteins are stable. The objective is to modify residues in proteins chemically, either to provide mechanistic information or to produce useful alterations of activity. Some of the more frequent modification reactions are listed in Table 9.1. Spectroscopic probes may be covalently... 

Rademann, J. (2004). Organic protein chemistry drug discovery through the chemical modification of proteins. Angew. Chem. Int. Ed. 43, 4554-4556. 

In addition to structure control, metal ions can act as reactive centers of proteins or enzymes. The metals can not only bind reaction partners, their special reactivity can induce chemical reaction of the substrate. Very often different redox states of the metal ions play a crucial role in the specific chemistry of the metal. Non-redox-active enzymes, e.g. some hydrolytic enzymes, often react as a result of their Lewis-acid activity [2], Binding of substrates is, however, important not only for their chemical modification but also for their transport. Oxygen transport by hemoglobin is an important example of this [3]. 

Specific modifications of proteins result from adding a selected reagent to the pure protein or crude protein-rich material. This may be done in the course of a fundamental study in protein chemistry or as a step in the production of a bulk protein product for practical purposes. The same chemical modification can be useful in both processes. For example, enzyme chemists use charge-changing modifications to dissociate oligomeric proteins to their monomer components, while the same modifications are proposed as a means of solubilizing yeast proteins to permit their extraction for use in foods (11). This chapter is concerned mainly with the many types of intended modifications. 

Much of what has been discussed concerns the application of chemical modification to questions of basic protein chemistry. This is still the area of greatest activity. The reader should consult the many review articles and texts of the last decade for details (1,2, 3,4,91). New methods published each year are gathered and discussed briefly in the Chemical Society s Specialist Periodical Reports on Amino Acids, Peptides, and Proteins. 

Chemical modification of proteins is an important everyday tool of basic protein chemistry. Its role in applied protein chemistry appears to be increasing and branching into different areas such as food, nutrition, and pharmacology. 

Voziyan PA, Metz TO, Baynes JW, and Hudson BG (2002) A post-Amadori inhibitor pyri-doxamine also inhibits chemical modification of proteins by scavenging carbonyl intermediates of carbohydrate and lipid degradation. Journal of Biological Chemistry 277, 3397- 03. 

Post-Translational Modifications, Roles in Regulating Protein Function Proteins, Chemistry and Chemical Reactivity of... 

Expanding the Genetic Code Through Chemical Biology Metallo-enzymes and Metallo-Proteins, Chemistry of Proteins, in vivo Chemical Modification of... 

Chemical Modification of Proteins Amino Acids, Chemical Properties of Enzyme Catalysis, Chemical Strategies for Proteins, In Vivo Chemical Modifications of Peptides, Chemistry of... 

The site-specific modification of native proteins is not one of the routine procedures in protein chemistry. It cannot be placed in the same category as end-group labelling or determination of amino acid composition and sequence. The specific chemical modification of a native protein can never be guaranteed because the reactivity of amino acids in a native protein is rarely predictable even if the three-dimensional structure of the protein is known. Unusual pK s of side chains, steric and solvent effects and the proximity of the amino acid residue to a ligand-binding site all influence its reactivity, frequently in opposite directions. However certain well-defined avenues of in-... 

Polymer surface modifications are omnipresent in applications where the surface properties of materials with favorable bulk properties are insufficient. By altering the surface characteristics using physical or chemical modification the desired surface properties may be achieved. Such treatments are required e.g. to enhance printability of films, the adhesion of paints, metal or other coatings, biocompatibility, protein resistances/reduced biofouling, etc. The diverse approaches met in practice include, among others, wet chemical and gas phase chemistry, plasma or corona, UV/ozone and flame treatments. In most cases surface chemical modification reactions take place that alter the surface energy in a desired way. For example,... 

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