Cyclic oligopeptides structure

Peptide antibiotics. Antibiotics with linear or cyclic oligopeptide structures containing not only L- amino acids but often also unusual, non-proteinogenic amino acids. Homopeptides are built up exclusively of amino acids (e.g., gramicidins), the so-called heteropeptides also contain other structural elements, e.g., hydroxamic acids. Macrocyclic Ra. containing one or more ester bonds in the ring are known as peptide lactones (e.g., hormaomycin) or depsipeptides (e.g., valinomycin). 

Chemical Name Cyclic oligopeptide (See Structural Formula)... 

A cyclic oligopeptide-containing azobenzene unit A-12 took a (3-tum-like structure after UV irradiation, while it was rather an extended structure before irradiation, as elucidated by NMR and molecular dynamics calculations [83]. ... 

The final chapter, by Itokawa, Takeya, Hitotsuyanagi, and Morita, reviews the various macrocyclic peptide alkaloids isolated from plants. In addition to a general overview of the many new peptide and amide alkaloids that have been isolated recently from a diverse range of plant families, this review places particular emphasis on the structure-activity relationships, the conformational analysis, and the antitumor activity of the RA series of cyclic oligopeptides from Rubia spp. 

Structure 4 Cyclodextrin analogous and glycosylated cyclic oligopeptides... 

Two In-bearing HPMA conjugates targeted with RGDfK or RGD4C (for structure, see Figure 1.21), the cyclic oligopeptides... 

All cyclosporines (A,B,C,. .. U,V,W), are oligopeptides containing 11 amino acids closed in a cyclic form. All of these are known amino acids except the first, which sometimes has not been isolated from natural sources. All of them are L-amino acids except for the amino acids in positions 3 and 8. Because of all of the hydrogen bonds, the structure of cyclosporine is quite rigid. Cyclosporines (A,B,C,. .. U,V,W) only differ in the second amino acid. 

Though this peptide has considerably increased conformational flexibility over the cyclic peptide tentoxin, it contains two backbone and side chain modifications which confer increased conformational rigidity to the molecule when compared with backbone non-mod1fied oligopeptides. It is helpful to recall that the conformation of a peptide is determined by its overall three-dimensional structure (14). If the bond angles and bond... 

In 2010, Tanaka s group investigated whether a chiral cyclic a-amino acid included in an oligopeptide chain could catalyze the epoxidation of different enones with high enantiomeric excess. They demonstrated that the a-helical secondary structure of the peptide catalyst is directly related to the chosen a,a-disubstituted amino acid [134]. Thus, they found that 5 mol% of a-helical nonamer 92 with urea-H2O2 as oxidant can catalyze the reaction with ee > 95% (Scheme 12.18). 

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