Peptide condensation

Fatty Held—Peptide Condensates. These proteia detergents are reaction products of fatty acid chlorides and hydrolyzed proteias. They are used ia shampoos because of their mildness on skin, hair, and to eyes when used alone or ia combination with alkyl surfactants (8). 

Dicyclohexylcaibodiimide (43) [538-75-0] is an impoitant peptide-condensing agent and analytical reagent (86). 

Further investigations, however, have shown that the above four-component peptide condensation is exceptionally efficient in terms of stereoselectivity70. A number of factors, including side reactions and insufficient solubility, influence this complex multistep reaction and these results cannot be reproduced with other amino acid combinations71. 

Figure 8.17 Proposed mechanism for the Cu2+/NaCl-catalysed peptide condensation reaction...

Still with the prebiotic scenario, the conditions developed by Limtrakul et al. (1985) are interesting as a consequence of evaporation, high local concentrations may have arisen, and under such conditions the incompletely hydrated metal ions may activate a dehydration leading to peptide condensation. From this, the technique of the salt induced peptide condensation (SIPC) has been developed (Oie et al, 1983 Suwannachst and Rode, 1999 Rode et al, 1999). 

Figure 7.10 Coiled-coil structures during peptide condensation, (a) Two peptides containing heptad repeats (A to F and A to F ) able to form a-helices. Hydrophobic interactions (A-A and D-D ) lead to coiled-coil structures, (b) A full-length peptide (T) acts as a template forming a coiled-coil structure with peptide fragments and directing their condensation in other full-length peptides (B). (Adapted from (a) Paul and Joyce, 2004 (b) Ghosh and Chmielewsld, 2004.)...

Peptide condensation -in nonaqueous media [ENZYMES IN ORGANIC SYNTHESIS] (Vol 9)... 

The combinatorial approach is attractive for the synthesis of libraries of hydroxamic acids for screening as metalloenzyme inhibitors. A variety of hydroxylamine-linked resins (shown in Schemes 9-12) have been developed that allow peptide condensation reactions followed by cleavage of the hydroxamic acid from the resin. 

Aggregation. Protein aggregation has two forms non-covalent (involving the interaction of two or more denatured proteins) and covalent (e.g., disulfide bond formation and/or peptide condensation reactions). 

Ethoxytrimethylsilylacetylene, (CHS Esters, lactones, and peptides. condensation of RCOOH with alcob lactams, or peptides, usually in the pi... 

Also, template controlled ligation of peptide nucleic acids is possible using EDC in an imidazole buffer. The highest selectivity is obtained using a peptide condensation that forms an abasic site. An example is the following reaction which produces the peptide 673. 

Peptide analysis. The reagent was introduced by Sanger for identification of the amino-terminal group of a protein or peptide. Condensation occurs under mild conditions to form a 2,4-dinitrophenyl protein on acid hydrolysis the terminal... 

Not only transpeptidation, but also a certain amount of peptide-peptide condensation, is possibly involved in the plastein reaction. With some of the proteases used for plastein formation, especially a-chymotrypsin (26, 52, 53, 54), the acyl-enzyme intermediate can be formed at pHs 5 from the reversal of the degradative reaction (Equation 1 E-OH + HOOC-CHR-NH E-O-OCCHR-NH- + H20). Once the acyl-enzyme intermediate is formed, the acyl group can be transferred to a nucleophile resulting in peptide bond synthesis. 

Doubling reactions , in which two molecules of the activated peptide condense prior to cyclization, have been observed on several occasions, and have been used for the synthesis of gramicidin S . Because of these side-reactions, the careful characterization of the end-products, especially the determination of the molecular weights, is of paramount importance. 

Furthermore, using a concentric flow microfluidic device, different steps in silk assembly form solution to beta-like fibers were investigated and the assembly process was found to be similar to peptide condensation-ordering model suggested for amyloid cross-beta formation. ... 

Enzymatic techniques can be used to endow proteins with surface-active functionality. An enzymatic technique that has shown promise in enhancing surface properties of proteins is a modified version of the classical plastein reaction. The plastein reaction is known to be a protease-catalyzed reverse process in which a peptide-peptide condensation reaction [11,12] proceeds through the peptidyl-enzyme intermediate formation [13]. It is essentially a two-step process enzymatic hydrolysis of a protein and plastein formation from the hydrolysate peptides. A novel one-step process was developed as a modified type of the plastein reaction by Yamashita et al. [14,15], which... 

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