Performic acid-oxidized

Two examples among many may suffice to demonstrate the diverse spectroscopic variability of chemically modified flavin. Fig. 7 1185) shows the hypsochromic shift of 25 nm (solely) of the UV-peak of a flavin pentapeptide, isolated from monoamine oxidase by performic acid oxidation the visible peak is not influenced. Fig. 7 2,69) demonstrates the dramatic change of 8-acetoxy flavin upon conversion to the anion... 

Another approach is based on the electrophilic halogenation of 39 in the presence of water, affording 4,8-dibromo-2-oxaadamantane (108) in 40.6% yield. Boiling 108 with Raney nickel in methanol yields 104.137,138 4,8-Dihydroxy-2-oxaadamantane (109) is obtained by performic acid oxidation of 39.137... 

V5. van Roon, J. H., Haex, A. J. Ch., Seeder, W. A., and de Jong, J., Clinical and biochemical analysis of gluten-toxicity. II. Clinical experiments on patients suffering from idiopathic steatorrhea after the administration of bromine treated performic acid oxidized polypeptides originating from wheat gluten. Gastroenterologia 94, 227-235 (1960). 

To investigate stabilizing interactions involving a tyrosine residue, Haas et a/. 186) prepared the 105-124 tryptic peptide from performic acid-oxidized RNase A, which included the residues Pro-114 and Tyr-115. They measured... 

E. Haas, G. T. Montelione, C. A. McWherter, and H. A. Scheraga, Local structure in a tryptic fragment of performic acid oxidized ribonuclease A corresponding to a proposed polypeptide chain-folding initiation site detected by tyrosine fluorescence lifetime and proton magnetic resonance measurements, Biochemistry 26, 1672-1683 (1987). 

Incomplete oxidation can be a problem. Higher recoveries of cysteine and cystine have been achieved by reduction of those amino acids with 2-mercaptoethanol followed by incubation with 4-vinylpyridine. This converts cysteine and cystine to S-(4-pyridylethyl)-L-cysteine, a derivative that can be separated by ion-exchange chromatography. Performic acid oxidation of methionine in the presence of phenol is a suitable method for analysis of cysteine. 

Solution in 0.1 M acetate buffer, pH 3.5, resulted in an enzymically active species (8n) of 240,000 daltons (46). Tanis and Naylor (47) have reported that at low concentration of protein the 18 S form predominated above pH 5.3 and the 12 S form below pH 4.8. Between these pH values a rapid equilibrium of the 12 S and 18 S species was observed The dissociation behavior of urease at low pH depends on the buffer used. In 0.1 M potassium phosphate buffer, adjusted to pH 2.0 with HC1, a heterogeneous mixture of dissociated forms was obtained (d) with an Mw of about 150,000. In acetate buffer at pH 3.5 dissociation into a 120,000 molecular weight species (4n) was observed (48). In 34% acetic acid at pH 2.2 there is effected a dissociation to subunits (n) of 30,000 daltons (7). This same value was obtained for urease ultracentrifuged in 8 M urea -f- 0.5 M thiol and in performic acid oxidized urease (48). 

The two preparations from A. oryzae reportedly differ in amino acid and carbohydrate composition. The enzyme prepared by Minato contained 25% carbohydrate no cysteine was detected either by titration with p-mercuribenzoate in 6M urea or by cysteic acid analysis after performic acid oxidation (179). In contrast, Wolfenden et al. (92) reported 14 cysteine residues per mole of enzyme which reacted instantaneously with p-mercuribenzoate in the absence of urea. No explanation is available for this apparent discrepancy. 

After performic acid oxidation, cysteic acid 8.2 residues. 

Methionine and half-cystine were determined in duplicate as methionine sulfone and cysteic acid on the performic acid-oxidized protein [8. Moore, JBC 238, 235 (1963)). 

The cysteic acid value was obtained from analyses of performic acid-oxidized protein (37). 

Finally, it is very common for methionine to be determined as part of the standard hydrochloric acid hydrolysis. Indeed, methionine is not nearly as labile to oxidation as cysteine is. While this is appropriate for many samples, there are studies (27,91) that indicate that seriously flawed recoveries (10-40% low) may result from methionine determination by standard acid hydrolysis if the samples contain high levels of carbohydrate. For these sorts of samples, it is recommended that determination of methionine as methionine sulfone (by performic acid oxidation) be pursued. 

Determined after performic acid oxidation. d Based on 72-hr hydrolysate. 

CuBS4 has an apparent molecular mass of approximately 13 000 Da. Attempts to determine the amino acid analysis of this material have revealed that it contains very little amino nitrogen after performic acid oxidation, however, the sample was shown to contain abundant amino nitrogen. 

That the hydroxyamino group is in all cases attached to the 8 carbon is evident from the fact that periodate oxidation yields nitrosodimer (rather than N2O, which would arise from an N -hydroxyamino acid (42, 89)), performic acid oxidation affords glutamic acid (136) and, finally, deacylation followed by catalytic hydrogenation, reaction with fluoro-dinitrobenzene and hydrolysis gives N8-dinitrophenylornithine (63). 

Temperature is another parameter that must be dealt with carefully since it, too, may affect the microenvironment of reactive groups. Some competitive side reactions may be minimized or prevented by thoughtful choices of temperature. Performic acid oxidations of proteins generally are done at low temperatures — 10°C) to limit reaction to cysteines,... 

Bigelow (1960) has found that all six of the phenolic groups of performic acid-oxidized ribonuclease behave normally, which is to be expected since the oxidized protein is believed to be highly unfolded. More interesting is his finding that a pepsin-inactivated preparation of ribonuclease can be prepared which contains five normal phenolic groups and one buried one. 

The demonstration by Thompson (1954) that chlorination of the aromatic ring of tyrosine can result from performic acid oxidation of proteins in the presence of chloride is also worth noting. If this occurs, it is certain to alter the spectrum of the oxidation product. 

Ribonuclease, oval- Performic acid oxidation nor- Tramor and Shugar... 

Figure 16. Hydrolysis rate of bovine ribonuclease relative to that of performic acid-oxidized ribonuclease as a function of temperature (155). The follotving enzymes were used O, aminopeptidase , carboxy-peptidase A A, trypsin and , chymotrypsin.

Popenoe EA Jr, du Vigneaud V. Degradative studies on vasopressin and performic acid-oxidized vasopressin. J. Biol. Chem. 128. 

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