RIDME spectroscopy on high-spin Mn2+ centers. Issue 44 (1st November 2016)

• Record Type: Journal Article
• Authors: Akhmetzyanov, D.; Ching, H. Y. V.; Denysenkov, V.; Demay-Drouhard, P.; Bertrand, H. C.; Tabares, L. C.; Policar, C.; Prisner, T. F.; Un, S.
• Is Part Of: Physical chemistry chemical physics. Volume 18:Issue 44(2016)
• Page Start: 30857
• Page End: 30866
• Publication Date: 2016-11-01
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.3
• DOI: 10.1039/c6cp05239h
• Languages: English
• ISSNs: 1463-9076

Abstract

Abstract : A bis-MnDOTA complex was investigated by EPR dipolar spectroscopy. RIDME experiment revealed higher modulation depth compared to PELDOR and featured harmonics of the dipolar coupling frequency. Abstract : Pulsed EPR dipolar spectroscopy is a powerful tool for determining the structure and conformational dynamics of biological macromolecules, as it allows precise measurements of distances in the range of 1.5–10 nm. Utilization of high-spin Mn 2+ species as spin probes for distance measurements is of significant interest, because they are biologically compatible and endogenous in numerous biological systems. However, to date dipolar spectroscopy experiments with this kind of species have been underexplored. Here we present pulsed electron electron double resonance (PELDOR also called DEER) and relaxation-induced dipolar modulation enhancement (RIDME) experiments, which have been performed at W-band (94 GHz) and J-band frequencies (263 GHz) on a bis-MnDOTA (DOTA = 1, 4, 7, 10-tetraazacyclododecane-1, 4, 7, 10-tetraacetate) model system. The distances obtained from these experiments are in good agreement with predictions. RIDME experiments reveal a significantly higher modulation depth compared to PELDOR, which is an important consideration for biological samples. These experiments also feature higher harmonics of the dipolar coupling frequency due to effective multiple-quantum relaxation of high-spin Mn 2+ as well as the multiple-component background function. Harmonics of the dipolar coupling frequency were taken into account by including additional terms in the kernel function of Tikhonov regularization analysis.