Amino acids peptide synthesis from

Transcription occurs in the 5 to the 3 direction for the mRNA. The AUG codon would start peptide synthesis and Gly would be the C-terminal amino acid. Peptide synthesis would continue until a stop codon (in this case, UAA) appears. The peptide fragment from the DNA strand would be ... 

Peptide synthesis from y9-amino acids is particularly attractive for first feasibility micro-reactor tests as there are no chiral centers which may complicate analysis of the products [5, 88]. y0-Peptides are also attractive owing to their stmctural and biological properties, especially concerning the stability versus degradation by peptidases as compared with their a-analogues (see original citations in [5]). 

Preparative applications of these reactions have included work on peptide synthesis from amino-acids (suitably protected) using triphenyl phosphine (120)10 7 >108 or a polymer-bound aryldiphenylphosphine (128).109 Coupling is generally very efficient,107 but racemization problems occur in some reactions.108 109 A typical coupling reaction using (128) is outlined in Scheme 9. 

A comparison of the mean amino acid composition of the soils with those of algae, bacteria, fungi, and yeasts showed the greatest similarity to that of bacteria. [4] This suggests, perhaps not too surprisingly, a major role for microorganisms in the synthesis in the soil of amino acids, peptides and proteins from plant and animal residues, and also explains the relatively uniform amino acid composition in different soils. 

Due to the vast numbers and rapidity of novel developments in solid-phase synthesis over the past ten years, a number of reports currently found in the literature deal with solid-phase syntheses of lanthionine peptides. There are at least two different approaches to synthesize lanthionine peptides in which the sulfide bond links amino acid halves that are not direct neighbors within the peptide chain (Scheme 10). One obvious approach, method A, is based on the coupling of a preformed, orthogonally protected lanthionine monomer to the N-terminus of a peptide oxime resin. 48 This is then followed by acid-catalyzed cyclization and simultaneous release from the resin during amide bond formation with the C-terminal carboxy group via the peptide cyclization method on oxime resin (see Section 6.73.2.2). The alternative approach is lanthionine formation after peptide synthesis from amino acid derivatives, such as serine and cysteine (method B). 

As the intermediate products resulting from individual synthetic steps cannot be purified, a virtually 100% selectivity is essential for the synthesis of larger-peptide molecules. Even at a selectivity of 99% per reaction step, the purity will drop to less than 75% for a dekapeptide (30 steps) It is practically infeasible to go beyond 10-15 amino acid peptides by using the solid-phase method. In order to prepare larger peptides, individual fragments are first produced, purified, and then combined with the final molecule by liquid phase synthesis. This combination of methods is listed under chemical hybrid in Table 4.2. 

Relaxin is another peptide that can be extracted from the ovary. The three-dimensional structure of relaxin is related to that of growth-promoting peptides and is similar to that of insulin. Although the amino acid sequence differs from that of insulin, this hormone, like insulin, consists of two chains linked by disulfide bonds, cleaved from a prohormone. It is found in the ovary, placenta, uterus, and blood. Relaxin synthesis has been demonstrated in luteinized granulosa cells of the corpus luteum. 

While the experiments of Fig. 3 were performed with glycine, other peptides have been synthesized from other amino acids such as lysine, phenylalanine or proline 27 28). Peptide synthesis from an eighteen amino acid mixture has been also demonstrated by using (histidine and lysine)-rich proteinoid. When the product is fractionated on Sephadex G-25, most of the oligopeptides appear to be in the dipeptide-tripeptide range or larger, and little of free amino acids survive from the reaction. Virtually all types of amino acid appear to yield peptides (Fig. 4) 29). 

Carboxylic mixed anhydrides are very important for the rapid synthesis of peptides by the stepwise procedure,however the use of carboxylic mixed anhydrides,e.g.those derived from pivalic acid and a protected amino acid (1),suffers from two disadvantages. Firstly,regiospecificity of attack at the desired carboxyl function is largely determined by steric effects and will not be 100% for all coupling reactions.Secondly,such mixed anhydrides have a propensity towards disproportionation to symmetric anhydrides which is highly undesirable in terms of reaction efficiency.This latter process can be depressed by operation of the reaction at -15 °C, but with the concurrent decrease in reaction rate and,on large scale manufacture,increased costs. 

PQQ is present as a noncovalently bound coenzyme in bacterial enzymes, and organisms that are incapable of its de novo synthesis can import it from the culture medium. It is synthesized by reaction between glutamate and tyrosine residues in a small (24 amino acid) peptide that is coded for by one of the bacterial genes known to be required for PQQ synthesis (Stites et af., 2000b). 

The total synthesis of the peptide derived macrocycle dendroamide A 163 has been accomplished in 19% overall yield from appropriately protected heterocyclic amino acids. The oxazole amino acid 162 resulted from cyclodehydration of P-ketodipeptide 161 with bis(triphenyl)oxodiphosphonium triflate, with notable chemo- and stereoselectivity <03JOC9506>. 

Synthetic steps for the attachment of the first amino acid may differ from those of chain elongation. The subsequent methods are a commonly used for the synthesis of peptides with C-terminal carboxylic acids or amides. 

Human a-thrombin and the fluorogenic substrate (Tos-Gly-Pro-Arg-AMC HCI) were purchased from Sigma. Fmoc derivatives of amino acids were purchased from Advanced ChemTech and Novabiochem. N-a-Fmoc-N-y-trityl-L-Gln-Wang resin was purchased from Applied Biosystem Inc. The solvents used in peptide synthesis were obtained from Anachemia Chemical Inc. and Applied Biosystems Inc. 

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