Peptide linkage/bond

Proteias, amino acids bonded through peptide linkages to form macromolecular biopolymers, used as chiral stationary phases for hplc iaclude bovine and human semm albumin, a -acid glycoproteia, ovomucoid, avidin, and ceUobiohydrolase. The bovine semm albumin column is marketed under the name Resolvosil and can be obtained from Phenomenex. The human semm albumin column can be obtained from Alltech Associates, Advanced Separation Technologies, Inc., and J. T. Baker. The a -acid glycoproteia and ceUobiohydrolase can be obtained from Advanced Separation Technologies, Inc. or J. T. Baker, Inc. 

The peptide linkage is usually portrayed by a single bond between the carbonyl carbon and the amide nitrogen (Figure 5.3a). Therefore, in principle, rotation may occur about any covalent bond in the polypeptide backbone because all three kinds of bonds (N——C, and the —N peptide bond) are sin-... 

FIGURE 5.2 The peptide bond is shown in its usnal trans conformation of carbonyl O and amide H. The atoms are the oi-carbons of two adjacent amino acids joined in peptide linkage. The dimensions and angles are the average valnes observed by crystallographic analysis of amino acids and small peptides. The peptide bond is the light gray bond between C and N. (Adapted from Ramachandran, G. A., ct ai, 1974. Biochimica Biophysica Acta 359 298-302.)... 

Tasks (1) and (2) are relatively easy to accomplish. The sample is first heated with hydrochloric acid to break all of the peptide linkages (amide bonds) in the protein. The resulting solution is then passed through a chromatographic column (recall the discussion on pp. 5-6 in Chapter 1). This separates the different amino acids and allows you to determine their identities and concentrations. 

In peptide chemistry, the term "pseudopeptide" is commonly used to denote a peptide in which some or all of the amino acids are linked together by bonds other than the conventional peptide Linkage (13). Such pseudopeptides have found applications as specific structural... 

The secondary structure of a protein is determined by hydrogen bonding between CDO and N—H groups of the peptide linkages that make up the backbone of the protein. Hydrogen bonds can exist within the same protein... 

The peptide bond is characterized by a fixed planar structure, as was discovered by X-ray crystallography of peptides more than 60 years ago. The arrangement of the atoms in the peptide bond is due to resonance stabilisation the lowest-energy state of the system is that in which the four atoms forming the peptide linkage lie in a plane, while the C-N bond has partial double bond character. 

Fig. 19 Structure of LA-PRX (above) and degradation of LA-PRX (below), (a) Threaded a-CDs prevent hydrolysis of PLLA in LA-PRX. (b) LA-PRX converts into LA-pPRX by peptide linkage cleavage at bulky end-capping groups through action of papain, (c) Ester bond hydrolysis in the PLLA chain begins by an exposure of PLLA to water by release of a-CDs from LA-pPRX. Reprinted from [292] with permission...

Phenolic compounds can be condensed forming aryl-aryl and aryl-oxygen-aryl (ether linkages) bonds to yield diaryl and diaryl ether polymers (59). These are in many ways similar to natural humic acids, confirming earlier research by others (60-62) that humic acids are formed from the copolymerization of phenolic compounds with amino acids, peptides, and amino sugars. 

Figure 2-5 Dimensions of the peptide linkage. Interatomic distances in nm, including the hydrogen bond length to an adjacent peptide linkage, are indicated. The atoms enclosed by the dotted lines all lie approximately in a plane. However, as indicated in the lower drawing, the nitrogen atom tends to retain some pyramidal character.

---