Peptides histidine-/methionine-containing

Perhaps the most obvious approach to the synthesis of heme protein models is to reproduce the local environment of the heme active site by covalently attaching various peptide fragments to a suitable porphyrin. If the peptide fragments contain suitable amino acids (e.g. histidine, methionine), reproduction of the coordination sphere of the heme protein may be possible. 

A synthetic receptor, which is bound via non-covalent interactions to a dye, is able to function as a chemosensor. The basic requirement is that the displacement of the dye by an analyte results in a change of its optical properties. " Recently, it was shown that the combination of an organometallic Gp Rh complex with the dye azophloxine allows to selectively detect histidine- and methionine-containing peptides in water at neutral Due to the high... 

In order to determine whether a mixture of 16 and 17 can be employed to detect histidine- or methionine-containing peptides, competition experiments with 16,17 and the dipeptides His-Ala or Val-Phe were performed [59]. When a mixture of 16 and 17 ([Rh] = [17] = 50 xM) in buffered aqueous so-... 

Mel, CH3CN morpholine or diethylamine, methanol, 76-95% yield. These conditions also cleave tlie 4 -pyridyl derivative. The Pet ester is stable to the acidic conditions required to remove the BOC and r-butyl ester groups, to the basic conditions required to remove the Fmoc and Fm groups, and to hydrogenolysis. It is not recommended for use in peptides that contain methionine or histidine since these are susceptible to alkylation with methyl iodide. 

Figure 2.5 The cisplatin reactive group can covalently couple to methionine-, cysteine-, and histidine-containing peptides or proteins. It also reacts with guanine groups to form a covalent modification on the N7 nitrogen.

Table 6 shows that spinach ferredoxin contains all the amino acids in bacterial ferredoxin plus one residue each of methionine, histidine, and tryptophan. Like bacterial ferredoxin, spinach ferredoxin has an abundance of acidic and a paucity of basic amino acids. Hill and San Pietro (53) found that parsley ferredoxin is similar to the one from spinach in composition and spectra, but differs in lacking tryptophan. Little is known of the structure of plant ferredoxin. It is known that spinach ferredoxin is a single peptide chain with alanine at both ends (Tsugita et al. (103)). 

Oxidation in proteins and peptides are highly amino acid specific. The amino acid residues that are susceptible to oxidation generally fall into two groups, viz. those containing a sulphur atom (methionine, cysteine) and those with an aromatic side chain (histidine, tryptophan and tyrosine) [49]. 

Amino acid residues are potential targets of free radical oxidation and nitration. Carbonyl derivatives of proteins may be formed by the interaction of protein amino acid side chains, mainly cysteine, histidine, and lysine residues with reactive aldehydes, such as HNE and ONE generated by peroxidation of PUFAs (polyunsaturated fatty acids). Amino acid and peptide biomarkers of oxidative stress are typically focused on specific proteins related to disease pathology. For instance, the oxidation of histidine and methionine are typically discussed in (3-amyloid plaque formation and HNE-derived histidine adducts are the main focus of modifications on low-density lipoprotein (LDL) (An-nangudi et al., 2008). However, there are several specific examples of general biomarkers of oxidative stress that include endogenous histidine containing dipeptides such as carnosine and anserine as well as the very stable o,o -dityrosine. These will be discussed below. 

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