Reactivity of proteins

Some efforts have been taken to obtain the electrochemical response of Hb at solid electrode surfaces. Fan s electrochemical researches revealed that the electron-transfer reactivity of Hb could be greatly enhanced, simply by treating it with an organic solvent, dimethyl sulfoxide (DMSO) [115], Hb can also achieve its direct electron transfer in /V,/V-dimcthy I form am idc (DMF) film, as Xu [116] reported. These, therefore, suggested that there are many different factors that regulate electron-transfer reactivity of proteins. It also pointed out the complicated and precise regulation mechanisms of proteins in vivo. 

There are a number of findings suggesting that agents that facilitate elimination of protein carbonyls (by either proteolytic elimination or by enzymically mediated chemical reduction) may suppress neurodegenerative conditions in model systems (Botella et al., 2004). Consequently, as carnosine may also react with protein carbonyls, it is theoretically possible that it could suppress formation and /the reactivity of protein carbonyls in the brain. Whether carnosine participates in carbonyl reductase activity has not been investigated but it is also a reasonable speculation. 

For research on proteins, this article will only cover antibody-based technologies. The limitation in biological sample volume and the inabihty to amphfy unknown proteins in a similar fashion as nucleic acids determines the type of array. Another limitation is the cross-reactivity of proteins and antibodies that do not allow multiplexed probing of a complex biological mixture with more than 30 to 40 antibodies with sufficient sensitivity. 

Chemistry and Chemical Reactivity of Proteins, Matthew Francis Energetics of Protein Folding, Robert Baldwin NMR to Study Proteins, Angela Gronenborn Physical Chemistry in Biology, Allan Cooper... 

Proteins, Chemistry and Chemical Reactivity of Proteins, Structure, Function and Stabihty Self-Organization and Self-Assembly in Biology ... 

Nucleic acids do not display the same promiscuous chemical reactivity of proteins. Instead, individual synthetic nucleotides can display a unique functional group that can be exploited even more for direct attachment of probes (117). The simplest method of labeling DNA uses high-affinity bis-intercalating dyes such as ethidium bromide, acridine, and thiazole orange monomers... 

Chemistry and Chemical Reactivity of Proteins Struemre, Function and Stability of Proteins Lipidated Peptide Synthesis Synthesis of Natural and Unnatural Amino Acids... 

The predominant contribution of the folded native structure is amply illustrated by the findings that complete reduction of disulfide bonds and 5-carboxymethylation completely alters the immunochemical reactivity of protein antigens, such as ribonuclease, lysozyme, and other antigens.However, reduction of but two of the four disulfide bonds in ribonuclease had a negligible effect on the ability to precipitate with antibody to native ribonuclease. 

Electrostatics is one of the fundamental interactions that determine the structure, stability, binding affinity, chemical properties, and hence the biological reactivity, of proteins. Electrostatic interactions may contribute to the biological reactivity of proteins in a number of ways, which may be divided into the following general areas ... 

Taken together, these findings are compatible with the hypothesis that the reactivity of protein A for human immunoglobulin is at least divalently expressed in the molecule [71, 72], Thus, protein A can function as a bacterial superallergen that reproduces the releasing activity of anti-IgE and antigens on... 

In RNase the protonated histidyl residues and the cystyl residues are apparently the most reactive sites in reactions with the hydrated electron. This was concluded from measurements of the absolute reaction rates of amino acids, peptides, and proteins (I, 2) and from an analysis of the reactivity of proteins in terms of the reactivities of the individual amino acids. At a pH of about 9 the histidyl residues are dissociated and have a low reactivity. The absolute reaction rate constant of RNase at this pH is 5 X 109 M-1 sec.-1 (2) and can only be explained on the assumption that the four disulfide bridges inside the protein molecule contribute to its reactivity. This contribution, however, is less than would be expected for cystyl residues which show a rate constant of about Ke-aq = 2 X 1010 M 1 sec.-1. The lack of a full contribution from the disulfide bonds was ascribed to the shielding of these reactive groups by the unreactive peptide chains. 

When various Au/Cd ratios were employed, the results indicated a dramatic difference between the reactivities of protein-bound zinc and cadmium. Chromatograms for 2/1 and 5/1 ratios are presented in Figure 7 and data for these and other stoichiometries are summarized in Table II. Clearly the zinc is preferentially displaced by gold, in a reaction which goes to completion and is limited by the amount of gold present at the concentrations employed. However, when the zinc is completely displaced, an equilibrium displacement of cadmium is observed, and a decreasing proportion of the gold is MT bound. The chemistry can be represented as follows ... 

Coenzymes play a specific role in enzyme catalysis in a sense that they enable the enzyme to catalyze reactions that are outside the chemical reactivity of protein s amino adds alone. Table 4 lists the stmctures of principal coenzymes (Zubay, 1988 Walsh, 1998). 

In the early sixties Herries and Richards [12] studied the differences in reactivity of protein molecules before and after denaturation. They considered micelles as possible models since surfectants were well-established demturating agents. Their studies led them to be involv i in kinetic studies of reactions where the reactants partition differently between an aqueous and micellar phase. For their calculations they needed the partition cc fficient of the various reactant molecules between the aqueous and micellar phase. The gel permeation chromatography (GPC) technique was used for this purpose. 

Simply incubating a protein solution with the enzyme at a certain temperature can carry out the crosslinking of proteins by transglutaminase. The outcome, however, depends on several factors, including the ratio of enzyme to substrate (E/S), the reaction conditions, and the reactivity of protein substrates. As it has already been mentioned, some proteins can hardly be crosslinked by transglutaminase, although they contain both glutamine and lysine residues. Therefore, the reactivity of the protein substrate is the most important factor that... 

Eyring, H., F. H. Johnson, and R. L. Gensler. 1946. Pressure and Reactivity of Proteins, with Particular Reference to Invertase. Journal of Physical Chemistry 50 (6) 453-464. 

Recognizing the direction in which such research must eventually lead us, we shall confine ourselves here to studies of one class of biologically important molecules—the proteins. Even with this restriction we have an enormous twofold task first, we mus. determine the structure of various proteins and, second, we must explain their biological functions in terms of their molecular structures. The material in this book concerns the first problem, that of protein structure and the thermodynamics, kinetics, and mechanisms of various reactions of individual proteins. It is hoped that an understanding of the reactivity of proteins in isolated systems will ultimately contribute to our knowledge of the interactions between the proteins and the other constituents of the living cell. 

Rate measurements on pepsin and serum albumin have led Li (300) to conclude that all tyronnes in a ven protein molecule are not iodinated at the same rate. He also suggests that availability of groups in the protein may be a factor. The availability or reactivity of protein groups is receiving considerable attention. Anson (34) and Greenstein and Edsall (83) have discussed it in connection with SH determinations while Crammer and Neuberger (75), Cannan (74), Philpot and Small... 

Some possible explanations of the lack of reactivity of protein disulphide bonds have been discussed previously (4,11,12,13), It has been suggested that the important factors were steric hindrance and negative charges adjacent to the bonds. 

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