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Performic acid, oxidation with

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... [Pg.99]

Some of the earliest work in the oxidation of alkenes was performed by oxidation with potassium permanganate. Under acidic and neutral conditions the intermediately formed glycols are oxidized, generally leading to cleavage of the carbon-carbon bond. Thus, such procedures have seldom been synthetically applied to diene oxidation. One notable... [Pg.891]

In the oxidation of pentafluoroaniline with performic acid, along with the expected pentafluoronitrosobenzene, a 17% yield of decafluoroazoxy-benzene was isolated. Separate experiments showed that the condensation of the nitrosobenzene with the residual amine did not lead to the clean-cut preparation of the azoxy compound, whereas the thermal degradation of the nitroso compound did afford the azoxy compound. The implications of these observations are that either the azoxy product was formed, at least in part, by direct oxidation of the amine or the thermal history of the reaction permitted its formation from the intermediate nitroso compound [29]. [Pg.437]

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. [Pg.130]

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). [Pg.9]

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. [Pg.74]

It is possible to perform an oxidation with Dess-Martin periodinane under almost neutral conditions by adding pyridine to the reaction flask in order to neutralize the acetic acid, which is generated during the oxidation, and performing the work-up by treatment with sodium thiosulfate in the presence of a sodium bicarbonate buffer.2... [Pg.183]

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). [Pg.72]

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,... [Pg.29]

Fig. 8. Purification of chain C by chromatography on Sephadex G-50 (79). Sepha-dex G-50 column (1.8 X 35 cm) equilibrated with 0.05 M HCl. Lyophilized aqueous extract of 30 mg of DFP-inhibited, performic acid-oxidized a-chymotrypsin (A4) is dissolved in 1 ml 0.05 M HCl, put into the column, and eluted (5 ml/hr) by 0.05 M HCl. Solid line, absorption of the fractions at 280 mu. Dotted line, absorption at 230 mil. Ordinates, optical density. Abscissas, volume of eluatein milliliters. A, chain A C, chain C. Fig. 8. Purification of chain C by chromatography on Sephadex G-50 (79). Sepha-dex G-50 column (1.8 X 35 cm) equilibrated with 0.05 M HCl. Lyophilized aqueous extract of 30 mg of DFP-inhibited, performic acid-oxidized a-chymotrypsin (A4) is dissolved in 1 ml 0.05 M HCl, put into the column, and eluted (5 ml/hr) by 0.05 M HCl. Solid line, absorption of the fractions at 280 mu. Dotted line, absorption at 230 mil. Ordinates, optical density. Abscissas, volume of eluatein milliliters. A, chain A C, chain C.
The relative ease of oxidation of a model disulfide, di-DNP-cystine, is illustrated in Table XIXe, where the amount of oxidant used was just in 50% excess (Ramacbandran, 1961). The yield of 73% DNP-cysteic acid is not far from values for yields of cysteic acid (80-90 %) from performic acid oxidation of cystine (Schram et ah, 1954). Proteins with reactive —SH, —S—S—, or free —NH2 groups therefore pose problems when side reactions in the oxidative cleavage of peptide bonds is to be avoided (cf. Section V, B). [Pg.283]

As in the past, some facilities delivered successful analyses employing any of the cystine analytical methods (Table IV). Thus performic acid oxidation (PAO), still the most popular method, provided highly accurate analyses although also many bad analyses. Interestingly, direct determination as cystine was as successful as PAO, with a third of the values within 10% of the expected value. The most successful method was that using disulfide exchange, 6/9 sites being accurate within 15%. [Pg.190]

Analogous results have been obtained with reduced-carboxymethyl-ated bovine serum albumin, performic acid-oxidized ribonuclease, re-duced-carboxymethylated lysozyme, and several other proteins. [Pg.54]

If appropriate precautions have been taken in the preparation of a protein, and if oxygen is completely removed before hydrolysis, methionine will usually be recovered from acid hydrolysates in yields greater than 95 %. However, in some proteins (particularly those that are chemically modified) and in many peptides the methionine may be at least partially oxidized to the sulfoxide or sulfone forms, and even though these may be analyzed with amino acid analyzers (see below), the total yield of methionine (and oxidized products) is usually somewhat low. A good check on total methionine content in a peptide or protein is obtained by analyzing for methionine sulfone after performic acid oxidation, since methionine and its sulfoxides are quantitatively converted to the sulfone by this procedure. [Pg.22]

Methionine carboxymethylsulfonium salts These derivatives of methionine (isomers) are prepared by treating proteins with iodoacetic acid the reaction is most specific for methionine at acid pH ( 3.5). These derivatives are not affected by performic acid oxidation (see under methionine sulfoxide), but are degraded by acid hydrolysis to give methionine, carboxymethyl-homocysteine, homoserine and homoserine lactone (Gundlach et al. 1959). [Pg.29]

Modification by performic acid oxidation Treatment of proteins with performic acid leads to the oxidation of cysteine and cystine residues to cysteic acid residues (Sanger 1949). Methionine residues are quantitatively converted to the sulfone (Hirs 1956), and tryptophan undergoes oxidative destruction (Toennies and Homiller 1942 Benassi et al. 1965). Other amino acids are not modified, provided that precautions are taken to avoid chlorination (Thompson 1954 Hirs 1956), or bromination (Sanger and Thompson 1963) of tyrosine residues. Cleavage of peptide bonds does not occur on performic acid oxidation at low temperature. [Pg.102]

The 2-D TLC was successfully applied to the separation of amino acids as early as the beginning of thin-layer chromatography. Separation efficiency is, by far, best with chloroform-methanol-17% ammonium hydroxide (40 40 20, v/v), n-butanol-glacial acetic acid-water (80 20 20, v/v) in combination with phenol-water (75 25, g/g). A novel 2-D TLC method has been elaborated and found suitable for the chromatographic identification of 52 amino acids. This method is based on three 2-D TLC developments on cellulose (CMN 300 50 p) using the same solvent system 1 for the first dimension and three different systems (11-IV) of suitable properties for the second dimension. System 1 n-butanol-acetone -diethylamine-water (10 10 2 5, v/v) system 11 2-propanol-formic acid-water (40 2 10, v/v) system 111 iec-butanol-methyl ethyl ketone-dicyclohexylamine-water (10 10 2 5, v/v) and system IV phenol-water (75 25, g/g) (h- 7.5 mg Na-cyanide) with 3% ammonia. With this technique, all amino acids can be differentiated and characterized by their fixed positions and also by some color reactions. Moreover, the relative merits of cellulose and silica gel are discussed in relation to separation efficiency, reproducibility, and detection sensitivity. Two-dimensional TLC separation of a performic acid oxidized mixture of 20 protein amino acids plus p-alanine and y-amino-n-butyric acid was performed in the first direction with chloroform-methanol-ammonia (17%) (40 40 20, v/v) and in the second direction with phenol-water (75 25, g/g). Detection was performed via ninhydrin reagent spray. [Pg.1667]

Metabisulfite analysis can be performed by oxidation with a measured volume of 0.1 N iodine in acid solution and determination of excess of iodine by titration with sodium thiosulfate. The metabisulfite titration can be performed manually using a starch indicator or potentiometrically using an autotitrator. [Pg.278]

The activity and selectivity are therefore governed by the balance of acidic and basic properties of a catalyst. When the basic property is too strong, the maximum yield of acrolein becomes low. Possibly polymerization of the produced acrolein is promoted by the strongly basic sites. However, when the basic property is suppressed too much by the incorporation of an acidic oxide, the catalyst loses the activity. On the other hand, the degradation of HCHO is promoted also by acid-base bifunctional properties. The control of the acid-base property of catalyst is performed by the combination of an acidic oxide with a more basic oxide. Therefore, it is considered that the acid-base properties of the Ni-P, Mn-P, Co-P, Fe-P, and V-P oxide systems are best fit for promoting solely the condensation reaction. [Pg.187]

Amino acids Acid hydrolysis (HCI 6N) followed by chromatography. There are many methods with variants in duration (24-48 hours) and temperature (110-I45°C). Methionine and cystine are obtained after performic acid oxidation and tryptophan after alkaline hydrolysis. [Pg.19]


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