ABSTRACT
Cyclosporins B, C, D, and E were characterized by NMR spectroscopy, and backbone flexibility was studied by molecular dynamics simulation. Structures of the molecules were characterized by nuclear Overhauser effect spectroscopy, which revealed that the studied peptides have many common features. Molecular dynamics simulation showed that the backbone of cyclosporin E is relatively more rigid than in other peptides. Calcium-dependent swelling of liver mitochondria under the influence of four considered compounds was also investigated. Three of them were found to have the activity similar to cyclosporin A, inhibiting opening of the mitochondrial pore at concentrations within 100-300 nM. However, cyclosporin E did not show any biological effect at concentrations up to 1 µM. Results of this study agree with the idea on the correlation between the peptide chain flexibility and its bioavailability.
Subject(s)
Cyclosporine/chemistry , Cyclosporine/pharmacology , Mitochondrial Membranes/metabolism , Animals , Carbon-13 Magnetic Resonance Spectroscopy , Computer Simulation , Mitochondria, Liver/metabolism , Mitochondrial Membrane Transport Proteins/metabolism , Mitochondrial Membranes/drug effects , Mitochondrial Permeability Transition Pore , Proton Magnetic Resonance Spectroscopy , Rats, Wistar , Time FactorsABSTRACT
The protein hormone insulin exists in several forms in nature, and a large number of modified sequences are used in pharmacy. They differ by physicochemical properties and efficiency of biological action. Pancreatic bovine insulin was studied in an acidic solution by nuclear magnetic resonance spectroscopy. [Formula: see text]H and [Formula: see text]C NMR signal assignment of backbone and side chains was made by analysis of a set of 2D spectra obtained on a sample with natural isotope abundance. The presence of certain secondary structure elements was revealed on a qualitative level based on nuclear Overhauser effect spectroscopy, which are similar to those observed in the crystal structure. The C-terminus of the B-chain possessed a remarkable flexibility. The molecule was shown to exist in exchange with oligomers based on its self-diffusion coefficient and correlation time measurements performed at different concentrations. Certain signals in the NOESY and HSQC spectra are consistent with the presence of minor conformers; this is an obstacle in simulating the molecular structure under the conditions used in the experiment.
