[Effective synthesis of cyclic analogs of bradykinin]. / Effektivnyi sintez tsiklicheskikh analogov bradikinina.

Cyclo-epsilon-(L-lysine1, glycine6-bradykinin) (CLGB) and cyclo-epsilon-kallidin have been synthesised in solution. To prepare linear precursors, fragment condensation (3 + 3 or 4) + 3 was used. Peptide bond formation, including cyclization, was carried out mainly through intermediate pentafluorophenyl esters. After purification on silicagel, protected cyclopeptides were obtained with a 50 to 60% yield. The protecting groups were eliminated by treatment with hydrogen fluoride in the presence of anisole. CLGB and CK were purified by droplet countercurrent chromatography and by reversed-phase HPLC, respectively.

[Study of bradykinin conformation in a dimethylsulfoxide solution by two-dimensional 1H-NMR spectroscopy]. / Issledovanie konformatsionnogo sostoianiia bradikinina v rastvore dimetilsul'foksida metodami dvumernoi spektroskopii 1H-IaMR.

The role of charged groups of the nonapeptide bradykinin in stabilization of its spatial structure in dimethyl sulfoxide solution was investigated. The signal assignment in the 1H-NMR spectra was achieved by means of two dimensional correlated spectroscopy (COSY) and nuclear Overhauser enhancement spectroscopy (NOESY). The changes in the NH and C alpha H proton chemical shifts of the Arg1 and Arg9 residues, variations both in temperature coefficients of chemical shifts of NH-resonances and coupling constants, as well as the appearance of additional NOE cross-peaks in NOESY spectra for d alpha N and d beta N 1H-1H distances were revealed by comparing the NMR spectra for two states--with the protonated C-terminal carboxyl group and deprotonated one. The experimental results are in agreement with the assumption that the conformation of the peptide in (CD3)2SO is stabilized by electrostatic interaction between the oppositely charged N- and C-terminal groups. The conformation with deprotonated alpha-carboxyl group is characterized by two beta-turns in the sequences Pro2-Pro-Gly-Phe5 and Ser6-Pro-Phe-Arg9.

[Substance P. New cyclic analogs]. / Veshchestvo P. Tsiklicheskie analogi novogo tipa.

[Adpoc-Glu(N3)6, (Met-N3)11] substance P-(6-11)-peptide was reacted with diamines H2N(CH2) nNH2 (n = 3-10, 12) to give cyclopeptides. Subsequent careful cleavage of the Adpoc group leads to the formation of compounds of type cyclo-[H-Glu-Phe-Phe-Gly-Leu-Met-NH-(CH2) n-NH-] X HCl. The substances produce a specific two-phase myotropic effect in experiments on isolated guinea pig ileum. The compounds where n is 3, 7, 12 exhibit also a hypotensive activity when assayed on anaesthetized rats.

[Study of the spatial structure of des-Gly9-[Arg8]vasopressin by two-dimensional NMR spectroscopy and theoretical conformation analysis]. / Issledovanie prostranstvennoi struktury des-Gly9-[Arg8]vazopressina metodami dvumernoi spektroskopii IaMR i teoreticheskogo konformatsionnogo analiza.

2D 1H-NMR spectra of des-Gly9-[Arg8]vasopressin in dimethylsulfoxide have been taken and the 1H resonances have been assigned. The coupling constants and amide proton temperature coefficients (delta delta/delta T) have been measured and the NOE cross-peaks in the NOESY spectrum have been analyzed. The most essential information on the spatial structure of des-Gly9-[Arg8]vasopressin is extracted from the low delta delta/delta T value for Asn5 amide proton and from the NOE between the Cys1 and Cys6 alpha-protons. A diminished accessibility of the Asn5 NH proton for the solvent is ascribed to the presence of a beta-turn in the fragment 2-5. The distance between the Cys1 and Cys6 C alpha H protons seems to be less than 4 A. These constraints were taken into account in the conformational analysis of the title peptide. The derived set of the low-energy backbone conformations was analyzed against the background of the all available NMR data. The most probable conformation of the cyclic moiety in des-Gly9-[Arg8]vasopressin was found to be the type III beta-turn. The corner positions are occupied by the residues 3, 4, while the residues 1-2 and 5-6 are at the extended sites. Some NMR data indicate that this structure is in a dynamic equilibrium with other minor conformers.

[Study of the spatial structure of a cyclic analog of bradykinin in solution by two-dimensional NMR spectroscopy]. / Issledovanie prostranstvennoi struktury tsiklicheskogo analoga bradikinina v rastvore metodami dvumernoi spektroskopii IaMR.

H NMR resonances of [cyclo (9----18) Lys1, Gly6]bradykinin (CBK) in (CD3)2SO and H2O solution have been assigned by combined analysis of two-dimensional COSY and NOESY spectra. The presence of two slowly interchangeable conformers of CBK in (CD3)2SO is established, the minor conformer not exceeding 15% in the population. The minor conformer is absent from the aqueous solution, chemical shifts of the CBK and bradykinin NH and C alpha H protons differ insignificantly. The major CBK conformer contains at least two X-Pro trans-peptide groups and three amide protons NH Phe5, NH Arg9 and N zeta H Lys1 protected from solvent. A system of cross-peaks from the NOESY spectra of CBK in (CD3)2SO has been analysed and the maximum distance between backbone protons and neighbouring amino acid residues evaluated. The experimental data agree well with the assumed type II beta-bend in the sequence Pro2-Pro3-Gly4-Phe5. Spatial structure models for the backbone fragment 6-9 of CBK containing two intramolecular hydrogen bonds that involve the NH Arg9 and N zeta H Lys1 protons and the carbonyl groups of Phe5 and Gly4 are proposed.