Forming Peptide Bonds

At temperatures that leave the substrate and the product intact, this reaction has no driving force 

Let us analyze once more with a different emphasis what has just been said An N-protected amino acid chloride can be deprotonated by an amino acid ester with a free NH2 group because the enolate produced is stabilized, among other things, by the electron-withdrawing inductive effect of the Cl atom. This immediately suggests a solution to circumvent the described dilemma Activating the N-protected amino acid requires a derivative in which the 

Organometallics, and Heteroatom-Stabilized Carbanions on the Carboxyl Carbon 

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As an example, Nakayama et al. thermally oxidized CNTs to introduce carboxyl groups at the opened CNT tips and then covalently linked ethylenediamine as a crosslinker (via EDC coupling) to provide primary amino groups that formed peptide bonds with N-hydroxysuccinimide-functionalized proteins (Fig. 5.2) [26]. 

Unactivated COOH groups form peptide bonds directly with N-terminal amino groups in the presence of... 

D is correct. Water is removed to form peptide bonds. 

Since water is lost during the condensation of amino acids to form peptide bonds, the residue weight of threonine will be 119- 18 = 101. If we assume a single threonine residue per molecule, then 101 represents 1.8 percent of the molecular weight, and... 

Peptide A peptide is a compound formed when at least two amino acids condense or react together. A peptide group is so formed, —CO-NH—. A larger compound containing thousands of amino acids forming peptide bonds is called a protein. 

Sheehan JC, Hess GP. A new method of forming peptide bonds. 

The kinetic approach can be more efficiently manipulated than the thermodynamic approach, but serine and cysteine proteases are not perfect acyl transferases. Undesired reactions may take place parallel to acyl transfer, for instance hydrolysis of the acyl-enzyme, secondary hydrolysis of the formed peptide bond, and other undesired proteolytic cleavages of possible protease-labile bonds in reactants and product. The elimination or minimization of these disadvantages can be performed by various manipulations on the level of the reaction medium, the enzyme, and the substrate, as well as on mechanistic features of the process. 

If the number of amino acids forming peptide bonds is n , (n-1) molecules of water are produced in the peptide formation. 

The active ester methodology has been much applied mainly to form peptide bonds under mild conditions in both liquid- and solid-phase synthesis. In liquid-phase synthesis, most frequently the activation of a carboxyl group has employed HOSu, followed by esters of electron-withdrawing-containing phenols (nitrophe-nols of pentafluorophenols), the most reactive HOBt esters usually being unstable and used in solid-phase synthesis. The preparation of these active esters requires the presence of a coupling reagent such as DCC or DIC. 

Figure 5 Representation of a general, four-module peptide synthetase. Each basic module consists of an adenylation domain (A) and a thiolation domain (T). Condensation domains (C) between modules form peptide bonds such that the peptide grows from amino to carboxy, with growing chain transferred to the amino acid bound to the next module. The substrate specificity of the individual modules is manifested in the amino acid (aa) sequence of the final peptide product.

Four general actions comprise protein translation The mRNA binds to a ribosome amino acids are carried to the ribosome by transfer RNA (tRNA) the amino acids are joined, forming peptide bonds and the completed protein molecule is released from the ribosome. The synthetic processes are called initiation, elongation, and termination and are assisted by protein factors essential for each step. 

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