Oxidation on proteins

Effect of Deuterium Oxide on Protein Aggregation in Deuterio and Protio Phycocyanin and Other Proteins... 

Group counting may be used of course to study any chemical modification of proteins. A recent example is provided by the use of difference counting in a study of the effect of photo-oxidation on proteins (Vodrazka et al., 1961). 

To examine the effects of oxidation on proteins, one must understand which amino acids are most susceptible to oxidation and what the resulting products of oxidation are. Methionine is one of the most readily oxidized amino acid in proteins. Under mild oxidation conditions, Met-sulfoxide is formed. This is the primary oxidation mechanism under acidic conditions. The reaction to form Met-sulfoxide is reversible... 

Solubilized vat dyes behave towards wool very much as if they were acid dyes. Thus the rate of exhaustion is increased by the addition of acid to the dyebath and they are fixed to the protein fibre by chemical bonds. They are, however, much more difficult to oxidize on protein than on cellulosic fibres. Soluble Vat Blues O and OR are dyed in fairly strongly acid liquors containing 2 to 4 per cent of formic acid, one per cent of sulphoxylate and 5 per cent of sodium sulphate. Most of the other soluble... 

C. E. Bobst et al. Impact of oxidation on protein therapeutics conformational dynamics of intact and oxidized acid-p-glucocerebrosidase at near-physiological pH. 2010. Protein Sci. 19(12), p. 2366. DOI 10.1002/pro.517. 

Several aryl esters of 6-chloromethyl-2-oxo-2//-l -benzopyran-3-carboxylic acid act as human Lon protease inhibitors (alternate substrate inhibitors)46 without having any effect on the 20S proteasome. Proteasomes are the major agents of protein turnover and the breakdown of oxidized proteins in the cytosol and nucleus of eukaryotic cells,47 whereas Lon protease seems to play a major role in the elimination of oxidatively modified proteins in the mitochondrial matrix. The coumarin derivatives are potentially useful tools for investigating the various biological roles of Lon protease without interfering with the proteasome inhibition. 

It is unfortunately the case that when we incubate apoferritin with a certain number of iron atoms (for example as ferrous ammonium sulfate), the product, after elimination of non-protein-bound iron, does not have a homogeneous distribution of iron molecules which were able to (i) take up iron rapidly through the three fold channels, (ii) quickly transfer it and form a diiron centre on a ferroxidase site, and (iii) to transfer the iron inward to a nucleation site, where (iv) it will begin to catalyse iron oxidation on the surface of the growing crystallite, will accumulate iron much more rapidly, and in much greater amounts than molecules in which steps (i), (ii) and (iii) are slower, for whatever reasons (perhaps most importantly subunit composition, and the disposition of subunits of the two types H and L, one with regard to the other). This polydispersity makes the analysis of the process of iron uptake extremely difficult. 

From a broader perspective, protein oxidation can result in covalent modification at many sites other than just at cysteine thiols. The earliest reports on protein oxidation date from the first decade of the twentieth century, but it took many more years to characterize these reactions and their products (Dakin, 1906). 

It is obvious that the oxidation of protein molecules can have detrimental effects on protein structure and function. However, there are some unique methods in bioconjugation wherein controlled and purposeful oxidation is done to study protein-protein interactions (Chapter 28, Section 4). 

Unfortunately, there are no universal methods to detect all types of protein oxidation, because the products formed can be so diverse in nature. However, some forms of protein oxidation can be assayed using chemical modification (Davies et al., 1999 Shacter, 2000). In particular, the formation of carbonyl groups on proteins can be targeted using the reagent 2,4-dinitrophenyl-hydrazine (DNPH). This compound reacts with aldehydes to form 2,4-dinitrophenylhydrazone derivatives, which create chromogenic modifications that can be detected at high sensitivity in microplate assays or Western blot analysis (Buss et al., 1997 Winterbourn et al., 1999). 

Similar to lipids the oxidation of proteins has already been studied for more than 20 years. Before discussing the data on protein oxidation, it should be mentioned that many associated questions were already considered in previous chapters. For example, the oxidation of lipoproteins, which is closely connected with the problems of nonenzymatic lipid peroxidation was discussed in Chapter 25. Many questions on the interaction of superoxide and nitric oxide with enzymes including the inhibition of enzymatic activities of prooxidant and antioxidant enzymes are considered in Chapters 22 and 30. Therefore, the findings reported in those chapters should be taken into account for considering the data presented in this chapter. 

The effects of antioxidants on protein oxidation were also studied in animal experiments. Barja et al. [73] demonstrated that feeding guinea pigs with vitamin C decreased endogenous protein oxidative damage in the liver. Administration of the mixture of antioxidants containing Trolox C, ascorbic palmitate, acetylcysteine, (3-carotene, ubiquinones 9 and 10, and (+)-catechin in addition to vitamin E and selenium to rats inhibited heme protein oxidation of kidney homogenates more efficiently than vitamin E + selenium [74]. 

Chen LY, Mehta P, Mehta JL (1996) Oxidized LDL decreases L-arginine uptake and nitric oxide synthase protein expression in human platelets relevance of the effect of oxidized LDL on platelet function. Circulation 93 1740-1746... 

Fig. 11.6 Optical properties of thermal oxide on silicon for three oxide thickness of 80, 100, and 120 nm. (a) The reflectance as a function of wavelength, (b) The relative change in reflectance upon immobilization of 1 nm protein...

---