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ABSTRACT: The new technique of pulsed electron-electron double resonance in electron spin-echo (PELDOR) in combination with the CW-ESR method has been used to investigate the secondary structure of a double spin-labeled peptide (the [TOAC-1,8]-analogue of the peptaibol antibiotic trichogin GA IV) that is hidden into a tetrameric supramolecular assembly of unlabeled peptide molecules. The magnetic dipole-dipole relaxation of spin labels has been experimentally studied in glassy solutions of the double-labeled peptide frozen to 77 K in a mixture of chloroform-toluene with an excess of unlabeled peptide. The PELDOR signal oscillations have been observed at high degrees of dilution with unlabeled peptide. The intramolecular distance between the spin labels of the peptide molecule in the aggregate has been determined from the oscillation frequency to be 15.7 A which is close to the value of (approximately equal to) 14 A calculated for a 3(10)-helical structure. Estimation of the fraction of this ordered secondary structure shows that about 19% of the peptide molecules in aggregates are folded in the 3(10)-helical conformation. The present experimental results are consistent with our molecular model presented in J. Am. Chem. Soc. 2000, 122, 3843-3848, wherein four amphiphilic 3(10)-helical peptide molecules form a vesicular system with the polar amino acid side chains pointing to the interior, and the apolar side chains, to the exterior of the cluster. The experimental data were compared with the results obtained with other techniques.
Journal of the American Chemical Society 05/2001; 123(16):3784-9. · 9.91 Impact Factor
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ABSTRACT: Possibilities of the structure determination of radical pairs having fixed geometry with the help of ELDOR in ESE technique
are considered. It is demonstrated that one can obtain information on relative orientation of paramagnetic centers in weakly
coupled pairs in addition to the energy parameters of the spin Hamiltonian. Appropriate requirements for such experiments
are formulated.
Applied Magnetic Resonance 04/1998; 14(1):101-113. · 0.75 Impact Factor
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ABSTRACT: The papers related to the theoretical background and experimental investigations by pulsed electron double resonance (PELDOR)
are reviewed. The main aim of this pulsed ESR application is to study the dipole-dipole spin interaction. In PELDOR the ESR
spectrum is excited by two ESE pulses at frequencyω
a and additional pumping pulse atω
b. Decay functionV(T) of the ESE signal, when the time intervalT between the first ESE pulse and pumping pulse is varied, contains the information on dipole-dipole couplings in the spin
system. The kinetics ofV(T) decay strongly depends upon distance, mutual orientation inside interacting spin pairs and space distribution of radicals
throughout the sample. The distances between spins which were measured or estimated using PELDOR in the papers reviewed are
in the range of 15 ÷ 130 Å. This pulsed ESR technique turns now to be a powerful supplement to conventional ESE in studying
the free radicals space distribution..
Applied Magnetic Resonance 04/1998; 15(1):107-143. · 0.75 Impact Factor
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Doklady biochemistry: proceedings of the Academy of Sciences of the USSR, Biochemistry section / translated from Russian 370(1-6):8-11.
