Water accessibility in a membrane-inserting peptide comparing Overhauser DNP and pulse EPR methods
| Autor: | Takuya F. Segawa, Yevhen Polyhach, Luca Garbuio, Gunnar Jeschke, Maximilian Doppelbauer, Andrin Doll |
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| Rok vydání: | 2016 |
| Předmět: |
Magnetic Resonance Spectroscopy
Lipid Bilayers Analytical chemistry General Physics and Astronomy 02 engineering and technology Nuclear Overhauser effect 010402 general chemistry 01 natural sciences law.invention Nuclear magnetic resonance law Pyrroles Sulfhydryl Compounds Physical and Theoretical Chemistry Microwaves Electron paramagnetic resonance Spin label Pulsed EPR Chemistry Dynamic nuclear polarisation Electron Spin Resonance Spectroscopy Water Site-directed spin labeling Nuclear magnetic resonance spectroscopy 021001 nanoscience & nanotechnology 0104 chemical sciences Models Chemical Phosphatidylcholines Proton NMR Spin Labels Peptides 0210 nano-technology |
| Zdroj: | The Journal of Chemical Physics. 144:194201 |
| ISSN: | 1089-7690 0021-9606 |
| DOI: | 10.1063/1.4948988 |
| Popis: | Water accessibility is a key parameter for the understanding of the structure of biomolecules, especially membrane proteins. Several experimental techniques based on the combination of electron paramagnetic resonance (EPR) spectroscopy with site-directed spin labeling are currently available. Among those, we compare relaxation time measurements and electron spin echo envelope modulation (ESEEM) experiments using pulse EPR with Overhauser dynamic nuclear polarization (DNP) at X-band frequency and a magnetic field of 0.33 T. Overhauser DNP transfers the electron spin polarization to nuclear spins via cross-relaxation. The change in the intensity of the (1)H NMR spectrum of H2O at a Larmor frequency of 14 MHz under a continuous-wave microwave irradiation of the nitroxide spin label contains information on the water accessibility of the labeled site. As a model system for a membrane protein, we use the hydrophobic α-helical peptide WALP23 in unilamellar liposomes of DOPC. Water accessibility measurements with all techniques are conducted for eight peptides with different spin label positions and low radical concentrations (10-20 μM). Consistently in all experiments, the water accessibility appears to be very low, even for labels positioned near the end of the helix. The best profile is obtained by Overhauser DNP, which is the only technique that succeeds in discriminating neighboring positions in WALP23. Since the concentration of the spin-labeled peptides varied, we normalized the DNP parameter ϵ, being the relative change of the NMR intensity, by the electron spin concentration, which was determined from a continuous-wave EPR spectrum. |
| Databáze: | OpenAIRE |
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