Peptides cyclo

Table III. Relative Potencies of -Methyl Lysine Analogs and Reference Peptides cyclo-(Pro-Phe-X-Y-Thr-Phe)a...

As an extension of Ghadiri s study, a 12-residue cyclic peptide, cyclo[(Gln-D-Ala-Glu-D-Ala),], afforded self-assembled nanotube materials having a uniform 13-A tailored pore diameter. Specifically sized tubular nanostructures with channel structures can expect various applications. ... 

Recently, we have published [49] the first observation of a VCD signal which appears to be due to a U-turn in a model peptide, cyclo-(-Gly-Pro-Gly-D-Ala-Pro-), which is known from NMR and X-ray studies to contain a Type II B-tum [50,51]. This molecule exhibits in solution a very distinct negative-positive-positive-negative VCD spectrum cf. Figure 10) unlike any other peptide conformation. 

The amino acid sequence 79-93 of VEGF is that involved in the interaction with VEGFR2. Arg-82, Lys-84 and His-86 are key residues in this interaction. The sequence is within a P-sheet structure built with ps and P6 antiparallel strands linked by a type II P-tum. Zilberberg et al. [263] synthesized a 17-amino acid cyclic peptide (cyclo-VEGI) that inhibited binding of VEGF to its receptor in a dose-dependent manner. Cyclo-VEGI... 

Peptides. The correlation of deuterium quadrupolar tensors by spin diffusion under slow magic-angle-spinning conditions can provide accurate measurements of their relative orientation. This work showed the technique applied to the cyclo-P-peptide cyclo[(5)- 3-homoalanyl-(R)-P-homoalanyl-(S)-P-homoalanyl-(i )-P-homoalanyl] with its amide hydrogens labeled by deu-terons. From the 2D spin-diffusion spectrum, the mutual orientation of the amide deuteron quadrupolar coupling tensors were found. Eight conformations that are all consistent with the NMR measurement were determined. 

Considering the knowledge of the elemental composition of the molecular ion M as well as the other data presented here, the authors [213a,b] were able to propose the following structure for this type of peptide [cyclo(L-AT-methyl-alanyl-L-valyl-D-3-oxo-3-phenyl-propionyl-L-2-oxo-3-methyl-butyryl)] (Fig. 62). 

On the other hand, Imanishi, Tanihara, Sugihara and Higashimura (27) prepared the cyclic peptides cyclo(glycyl-S-histidyl) and cyclo(S-leucyl-S-histidyl) and examined the catalytic activity for the hydrolysis of the. same ester as mentioned above. But no difference in rate was observed between the enantiomers of the substrate. 

The peptide cyclo [(D-Ala- L-Glu- D-Ala- L-Glu)2] with an even number of alternating d- and L-amino acids adopts a flat conformation. This macrocyclic synkinon forms extended stacks in water and vesicle membranes. A contiguous P-sheet in the form of tubules may reach a length of a few hundred nanometers and an inner diameter of about 7-8 A in water (Fig. 9.5.4). The tubules also condense to form bundles of about 100 parallel strands. In lipid bilayers these peptide nanotubes are aligned parallel to the hydrocarbon chain and act as ion channels at their rigid outer surfaces. Their regulation by molecular stoppers, applied potentials, etc. has not been achieved so far (Kim et al., 1998). 

Antamanide (AA), anti-amanita peptide , cyclo-(-Val-Pro-Pro-Ala-Phe-Phe-Pro-Pro-Phe-Phe °-), a non-toxic cyclic 10-peptide from Amanita phaUoides. Antamanide was isolated from the lipophilic part of extracts of A. phaUoides by chromatographic procedures, stmcturaUy characterized, and synthesized by Th. Wieland and co-workers in 1968. Administration at... 

Bartlett and co-workers at the University of California at Berkeley targeted the development of a peptide mimetic scaffold that would present the key molecular recognition features of the three amino acid binding loop to a-amylase. The cyclic peptides cyclo(D-Pro-Phe-Ala-Trp-Arg-Tyr) and cyclo(D-Pro-Phe-Ser-Trp-Arg-Tyr) were found to exhibit fC values of 14 and 32 pM, respectively, against a-amylase. The objective was then to locate a suitable mimic for the -turn region for incorporation into these cyclic peptides. 

Hilton, C. W., Prasad, C., Vo, P., Mouton, C. (1991). Food contains the bioactive peptide cyclo (His-Pro). Journal of Clinical Endocrinology arul Metabolism, 75, 375-378. 

The peptide cyclo- Pro-Gly-) forms complexes with different alkali and alkaline earth metals that show spectra with sensitivity to the conformation of the peptide the arrangement of the carbonyl groups is especially of interest. The solvent plays the most important role in the development of conformation. The size of the ion-binding cavity formed by the carbonyl groups and the size and charge of the cation are only of secondary importance. 

The heteronuclear shift correlated 2D-NMR spectrum of a cyclic peptide, cyclo(Pro-Phe-Gly-Phe-Gly), is presented in Figure 5.53. The proton chemical shifts (0-5 ppm) are on the horizontal axis while the chemical shifts (20-70 ppm) are on the vertical axis. The cross peaks establish the interconnection between the chemical shifts of protons and the chemical shifts of carbon atoms to which those protons are attached. 

Figure 5.53. Heteronuclear shift correlated 2D-NMR spectrum of a cyclic peptide, cyclo(Pro- Phe-Gly- Phe-Gly).

Scheme 2.1 UV-light-induced unfolding of peptide cyclo(Boc-Cys-Pro-Aib-OMe).

Polymer supports also can enable high yields in the synthesis of cyclic peptides. Cyclo-(Gly-His)3 was produced in 42% overall yield from attachment, five deprotection-coupling sequences, and cleavage from the resin.It was isolated by chromatography with no detectable amounts of oligomeric linear or cyclic peptides. 

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