title: Heating and temperature gradients of lipid bilayer samples induced by RF irradiation in MAS solid-state NMR experiments.
abstract: The MAS solid-state NMR has been a powerful technique for studying membrane proteins within the native-like lipid bilayer environment. In general, RF irradiation in MAS NMR experiments can heat and potentially destroy expensive membrane protein samples. However, under practical MAS NMR experimental conditions, detailed characterization of RF heating effect of lipid bilayer samples is still lacking. Herein, using1H chemical shift of water for temperature calibration, we systematically study the dependence of RF heating on hydration levels and salt concentrations of three lipids in MAS NMR experiments. Under practical1H decoupling conditions used in biological MAS NMR experiments, three lipids show different dependence of RF heating on hydration levels as well as salt concentrations, which are closely associated with the properties of lipids. The maximum temperature elevation of about 10 °C is similar for the three lipids containing 200% hydration, which is much lower than that in static solid-state NMR experiments. The RF heating due to salt is observed to be less than that due to hydration, with a maximum temperature elevation of less than 4 °C in the hydrated samples containing 120 mmol l-1of salt. Upon RF irradiation, the temperature gradient across the sample is observed to be greatly increased up to 20 °C, as demonstrated by the remarkable broadening of1H signal of water. Based on detailed characterization of RF heating effect, we demonstrate that RF heating and temperature gradient can be significantly reduced by decreasing the hydration levels of lipid bilayer samples from 200% to 30%. Copyright © 2016 John Wiley & Sons, Ltd.
authors.affiliation: Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Center for Magnetic Resonance, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, 430071, China.|University of Chinese Academy of Sciences, Beijing, 100049, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Wang
authors.affiliation: Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Center for Magnetic Resonance, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, 430071, China.
authors.forename: Zhengfeng
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Center for Magnetic Resonance, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, 430071, China.
authors.forename: Weijing
authors.initials: W
authors.lastname: Zhao
authors.affiliation: Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Center for Magnetic Resonance, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, 430071, China.
authors.forename: Liying
authors.initials: L
authors.lastname: Wang
authors.affiliation: Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Center for Magnetic Resonance, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, 430071, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Yang
keywords: MAS; RF field; hydration; lipid bilayers; salt concentration; sample heating; solid-state NMR