Cyclic Analogue of Human Heat Shock Protein 70(29-42) Fragment. Synthesis, Conformational Studies and Evaluation of Its Immunogenicity

The cyclic hexadecapeptide containing human heat shock protein 70(29-42) fragment cyclized by the disulfide bridge between two L-cysteine residues introduced at the N- and C-termini was synthesized by the solid phase method. It was established that the cyclic analogue, contrary to its linear counterpart, had much lower ability to generate immune response in rabbits. Conformational studies of cyclic peptide performed using 1D and 2D 1H-NMR spectroscopy in conjunction with theoretical conformational analysis revealed that the cyclization constrained the 3D structure of this peptide, reflected by the observed rate of cis/trans isomerization of Arg9-Thr10 peptide bond and the presence of Gly7-Asn8 peptide bond in cis geometry.We, therefore, postulate that the conformational flexibility in the case of Human Heat Shock Protein fragments is a key element for their immunogenicity.