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Nusair NA, Mayo DJ, Dorozenski TD, Cardon TB, Inbaraj JJ, Karp ES, Newstadt JP, Grosser SM, Lorigan GA. Time-resolved EPR immersion depth studies of a transmembrane peptide incorporated into bicelles. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1818:821-8. [PMID: 22100865 DOI: 10.1016/j.bbamem.2011.11.009] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2011] [Revised: 10/31/2011] [Accepted: 11/02/2011] [Indexed: 11/25/2022]
Abstract
The reduction in EPR signal intensity of nitroxide spin-labels by ascorbic acid has been measured as a function of time to investigate the immersion depth of the spin-labeled M2δ AChR peptide incorporated into a bicelle system utilizing EPR spectroscopy. The corresponding decay curves of n-DSA (n=5, 7, 12, and 16) EPR signals have been used to (1) calibrate the depth of the bicelle membrane and (2) establish a calibration curve for measuring the depth of spin-labeled transmembrane peptides. The kinetic EPR data of CLS, n-DSA (n=5, 7, 12, and 16), and M2δ AChR peptide spin-labeled at Glu-1 and Ala-12 revealed excellent exponential and linear fits. For a model M2δ AChR peptide, the depth of immersion was calculated to be 5.8Å and 3Å for Glu-1, and 21.7Å and 19Å for Ala-12 in the gel-phase (298K) and L(α)-phases (318K), respectively. The immersion depth values are consistent with the pitch of an α-helix and the structural model of M2δ AChR incorporated into the bicelle system is in a good agreement with previous studies. Therefore, this EPR time-resolved kinetic technique provides a new reliable method to determine the immersion depth of membrane-bound peptides, as well as, explore the structural characteristics of the M2δ AChR peptide.
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Catallo N, Colacicchi S, Carnicelli V, Giulio AD, Lucari F, Gualtieri G. Static Magnetic Field Effect on the Fremy’s Salt−Ascorbic Acid Chemical Reaction Studied by Continuous-Wave Electron Paramagnetic Resonance. J Phys Chem A 2010; 114:778-83. [DOI: 10.1021/jp906376h] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- N. Catallo
- INFM, Department of Health Sciences, University of L’Aquila, Via Vetoio, Coppito 2, 67100 L’Aquila, Italy, Department of Biomedical Sciences and Technologies, University of L’Aquila, Via Vetoio, Coppito 2, 67100 L’Aquila, Italy, and INFM, Department of Physics, University of L’Aquila, Via Vetoio, Coppito 1, 67100 L’Aquila, Italy
| | - S. Colacicchi
- INFM, Department of Health Sciences, University of L’Aquila, Via Vetoio, Coppito 2, 67100 L’Aquila, Italy, Department of Biomedical Sciences and Technologies, University of L’Aquila, Via Vetoio, Coppito 2, 67100 L’Aquila, Italy, and INFM, Department of Physics, University of L’Aquila, Via Vetoio, Coppito 1, 67100 L’Aquila, Italy
| | - V. Carnicelli
- INFM, Department of Health Sciences, University of L’Aquila, Via Vetoio, Coppito 2, 67100 L’Aquila, Italy, Department of Biomedical Sciences and Technologies, University of L’Aquila, Via Vetoio, Coppito 2, 67100 L’Aquila, Italy, and INFM, Department of Physics, University of L’Aquila, Via Vetoio, Coppito 1, 67100 L’Aquila, Italy
| | - A. Di Giulio
- INFM, Department of Health Sciences, University of L’Aquila, Via Vetoio, Coppito 2, 67100 L’Aquila, Italy, Department of Biomedical Sciences and Technologies, University of L’Aquila, Via Vetoio, Coppito 2, 67100 L’Aquila, Italy, and INFM, Department of Physics, University of L’Aquila, Via Vetoio, Coppito 1, 67100 L’Aquila, Italy
| | - F. Lucari
- INFM, Department of Health Sciences, University of L’Aquila, Via Vetoio, Coppito 2, 67100 L’Aquila, Italy, Department of Biomedical Sciences and Technologies, University of L’Aquila, Via Vetoio, Coppito 2, 67100 L’Aquila, Italy, and INFM, Department of Physics, University of L’Aquila, Via Vetoio, Coppito 1, 67100 L’Aquila, Italy
| | - G. Gualtieri
- INFM, Department of Health Sciences, University of L’Aquila, Via Vetoio, Coppito 2, 67100 L’Aquila, Italy, Department of Biomedical Sciences and Technologies, University of L’Aquila, Via Vetoio, Coppito 2, 67100 L’Aquila, Italy, and INFM, Department of Physics, University of L’Aquila, Via Vetoio, Coppito 1, 67100 L’Aquila, Italy
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Gualtieri G, Colacicchi S, Carnicelli V, Di Giulio A. Improvements in technical assessment and protocol for EPR evaluation of magnetic fields effects on a radical pair reaction. Biophys Chem 2005; 114:149-55. [PMID: 15829348 DOI: 10.1016/j.bpc.2004.11.014] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2004] [Revised: 11/08/2004] [Accepted: 11/22/2004] [Indexed: 11/17/2022]
Abstract
The effects of either static or pulsed magnetic fields on the reaction rate of Fremy's salt-ascorbic acid were studied directly by EPR spectroscopy. Radical pair mechanism (RPM) accounts for the magnetic field effects, but the expected amounts are so small that they need to be observed with particular care with EPR technique. The method is based on the resolution of a pair of EPR signals by the addition of a stationary field gradient, where the signals are coming from the exposed and control capillary sample. To this purpose, a suitable device for the gradient generation was used. Others improvements were the strictly keeping of the same boundary temperature condition in the capillary pairs, obtained by a refrigerating system controlled by a thermocouple, and the use of a pair of Helmholtz coils to generate an external high homogeneous magnetic field. By this experimental set up, we found that the magnetic field induce the decrease of the studied radical reaction rate. This EPR approach is a significant alternative to the spectrophotometric one. Moreover, it offers the advantage to detect both the radicals and/or intermediates involved in the reaction.
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