Cyanogen bromide, 508 Table

Allyl alcohols readily react with trichloroacetonitrile to give the corresponding trichloroacetimidates 145. Activation of the double bond with electrophilic reagents results in ring closure to yield oxazolines 146. The most commonly employed electrophiles include iodine, iodine monochloride, phenylselenyl chloride, and mercuric trifluoroacetate. Other nitriles including cyanogen bromide and N,N-dimethylcyanamide can also be used. Since oxazolines readily hydrolyze to amides, the net effect of this reaction sequence is to produce p-amino alcohols 147 from an allyl alcohol. This strategy has been employed in numerous total syntheses of natural products. Examples are listed in Table 8.18 (Fig. 8.7 Scheme 8.43). ° ... 

Table IV. Cyanogen Bromide Molecular Weight Fingerprint Data from 6% and 10% Agarose—GuHCl Columns...

Cyanogen bromide cleavage of the polypeptide subunit should yield 4 peptides if the subunit contains 3 methionines (Table III). Cleavage products were isolated by gel filtration through Sephadex G-75 columns and analyzed for purity with polyacrylamide gel electrophoresis in 8 M urea containing 0.1 M thioglycolate. Four peptide products were obtained (34). 

The above interpretations are hypothetical, but they have led to other inquiries showing that selective modifications of the active site of catalase are not limited to reactions involving Compound I. Inhibition of catalases with cyanogen bromide is an example of such a reaction (125). This modification occurs only with the free enzyme in a pH-invariant reaction (pH 4.5-7.5) the inhibition resulting from the incorporation of one C moiety of BrCN into the apoenzyme of each subunit (Table IV) (63, 90,... 

Recently Fallante et al. (200) reported that GSH S-transferase had been Imsioblllzed on a cyanogen bromide activated Sepharose gel, by a procedure similar to that discussed above for Immobilization of UDP-glucuronyltransferase (39), and used successfully for synthesis of GSH conjugates. A variety of substrates (Table VIII) were conjugated with this system and the products were characterized by chromatographic methods and FAB mass spectrometry. 

Hydrolysis of a protein into peptides can be accomplished by group-specific chemical and enzymatic reagents (Table 3-2). N-Bromosuccinimide and cyanogen bromide hydrolyze proteins at tryptophan and methionine (Figure 3-12) residues, respectively. Trypsin hydrolyzes... 

Iodine vapor allows nonspecific, usually nondestructive detection of many sub-stances (e.g. surface active agents [129], pharmaceuticals [130, 131], polyethylene glycols [132], see also Table 12). In addition, reactions have also been described with the vapors of bromine [133—135], cyanogen bromide [136], chlorine [137-141, 209], ammonia [147-147] (see also the reagent Ammonia vapor ). 

Pseudohalogens such as cyanogen bromide or cyanogen chloride in the presence of aluminium trichloride react with retention of configuration as shown in Table 13(f). This has been explained in terms of complexation of the counter ion with aluminium chloride making it a poor nucleophile such that addition step D does not occur to any extent. Why this should alter the selectivity of ft carbon attack in 28 versus silicon attack in 27 is not clear. 

Jornvall and Harris (91) presented data for the structures around all of the 14 cysteine residues in each protein chain. Analysis by Jornvall (92,93) of different peptide mixtures obtained after treatment of the protein with trypsin (before or after maleylation), chymotrypsin, pepsin, cyanogen bromide, or thermolysin yielded amino acid sequence information for all parts of the subunit and the primary structure of the whole protein chain was deduced (5S). It was found to contain 374 residues and is shown in Table I. An acetylated serine residue is at the N-terminus and the reactive cysteine residue is at position 46. Some residues are unevenly distributed (PS). Six of the seven histidine residues are in the N-terminal half of the molecule, the two tryptophan residues are in either terminal region, the four tyrosine residues are in the middle of the primary structure, and none of the 14 cysteine residues occur in the C-terminal quarter of the molecule. A characteristic distribution of hydrophobic residues was also noticed (93), which may now be partly correlated with the presence of large hydrophobic cores in the tertiary structure of the protein (Section II,C,3). Most regions of the primary structure were analyzed in many different overlapping peptides (92-9 ) with a corresponding increase in reliability. The structure is in excellent agreement with the total composition determined by acid hydrolysis (93). It is compatible with independently determined partial structures of... 

TABLE I. Predicted Cyanogen Bromide Fragments from the Spinach psbB Gene Product (CPa-1) and Sequcncesof Isolated Peptides Bearing the Epitope of the Monoclonal Antibody FAC2. 

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