Chemical modifications of proteins: history and applications

Abstract

With roots in ancient formulations, methods for the chemical derivatization of proteins continue to expand and develop. The creation of this new journal dealing exclusively with bioconjugate chemistry was barely conceivable just a few years ago. An explosion of interest in the subject during the last decade is, however, easily seen. The tremendous growth in both the number of publications and in the number of research groups involved in these kinds of studies has been promoted by both practical interests related, for example, in some cases to possible pharmacological or medical diagnostic applications and by interest in questions of fundamental biochemical structure and function.Greatly Reagents have been designed to preserve electrostatic charge (4,5), to alter electrostatic charge (6), and to increase hydrophobicity (7,8). Reagents and procedures have been developed to decrease immunogenicity (9, 20), to increase and decrease susceptibility to proteolysis (22-23), to increase UV or visible absorbancy (14), to introduce fluorescent labels (25,16), spin labels (27), radiolabels , various metal ions (22), magnetic microspheres (22,23), and electron-dense substituents (24), to increase the content of certain low-abundance nonradioactive isotopes (25)

Vinyl Sulfone: A Multi-Purpose Function in Proteomics

“…In addition, the optimal pH needed for the reaction with lysine of these reagents (pH 9-9.5) is higher than for the formation of succinimidyl esters (pH 8-9) and may be unsuitable for modifying alkaline-sensitive proteins. Other approaches are: a) the reductive amination of an aldehyde (4) using water compatible hydrides, a two-step procedure that make this route more challenging (Jentoft & Dearborn, 1979); b) the amidination with imidoesters (5) at elevated pH ( 9) or with iminothiolane (6, Traut's reagent) near pH 8, reagents that conserve the overall charge of the side group (Means & Feeney, 1990), and c) the use of thioesters or dithioesters (7, X=O or S, respectively), being these last mild reagents for lysine residues in the absence of competing cysteine residues (Wieland et al, 1953) that reacts very fast, specifically and irreversibly although they have a limited solubility in water. In contrast with lysine, cysteine residues are perhaps the most convenient target of the proteogenic amino acids for selective modification of proteins owing to their low natural abundance (the second less abundant amino acid in proteins with a frequency of 1.36%) (Villar & Kauvar, 1994;Villar & Koehler, 2000;UniProtKB/TrEMBL database, 2011-06) and the strong nucleophilic character of the sulfhydryl side chain higher than a primary amine, especially at pH below 9, that results in a general kinetic selective modification of cysteine over lysine residues.…”

Engineering of protein thermodynamic, kinetic, and colloidal stability: Chemical Glycosylation with monofunctionally activated glycans

“…The strategy involved introduction of a single reactive amine into the polysaccharide followed by coupling with a bifunctional linker that can be changed to accommodate for different choices of chemical conjugation. For example, another linker functional group that is highly used for protein modification and can be easily incorporated into polysaccharides with this activation strategy is the maleimide group, which is selective for the thiol groups of cysteine amino acids (Means and Gallop, 1990). Employment of this linker chemistry may be more appropriate for applications were attachment of a single polysaccharide to the protein surface is desired (Shannon et al, 2003).…”

Characterization of an Antagonist Interleukin-6 Dimer by Stable Isotope Labeling, Cross-linking, and Mass Spectrometry

“…Techniques in mass spectrometry (MS) combined with cross-linking (28 -30) or other chemical labeling techniques such as hydrogen/deuterium exchange (31, 32) have been evaluated for rapid low-resolution three-dimensional study of proteins (30) or protein complexes (33,34). Cross-linking/MS methods involve chemically or photochemically cross-linking a protein complex (35), followed by digestion of the cross-linked complex and MS analysis of the resulting peptide mixture (36). Cross-linked peptides can be identified by parent ion mass and/or the fragmentation pattern produced by tandem mass spectrometry (MS/MS), thereby locating adjacent protein regions and enabling assembly of low-resolution models of proteins or protein complexes.…”