title: Using low-E resonators to reduce RF heating in biological samples for static solid-state NMR up to 900 MHz.
abstract: RF heating of solid-state biological samples is known to be a destabilizing factor in high-field NMR experiments that shortens the sample lifetime by continuous dehydration during the high-power cross-polarization and decoupling pulses. In this work, we describe specially designed, large volume, low-E 15N-1H solid-state NMR probes developed for 600 and 900 MHz PISEMA studies of dilute membrane proteins oriented in hydrated and dielectrically lossy lipid bilayers. The probes use an orthogonal coil design in which separate resonators pursue their own aims at the respective frequencies, resulting in a simplified and more efficient matching network. Sample heating at the 1H frequency is minimized by a loop-gap resonator which produces a homogeneous magnetic field B1 with low electric field E. Within the loop-gap resonator, a multi-turn solenoid closely matching the shape of the sample serves as an efficient observe coil. We compare power dissipation in a typical lossy bilayer sample in the new low-E probe and in a previously reported 15N-1H probe which uses a double-tuned 4-turn solenoid. RF loss in the sample is measured in each probe by observing changes in the 1H 360 degrees pulse lengths. For the same values of 1H B1 field, sample heating in the new probe was found to be smaller by an order of magnitude. Applications of the low-E design to the PISEMA study of membrane proteins in their native hydrated bilayer environment are demonstrated at 600 and 900 MHz.
authors.affiliation: National High Magnetic Field Laboratory, Tallahassee, FL 32310, USA. pgorkov@magnet.fsu.edu
authors.forename: Peter L
authors.initials: PL
authors.lastname: Gor'kov
authors.forename: Eduard Y
authors.initials: EY
authors.lastname: Chekmenev
authors.forename: Conggang
authors.initials: C
authors.lastname: Li
authors.forename: Myriam
authors.initials: M
authors.lastname: Cotten
authors.forename: Jarrod J
authors.initials: JJ
authors.lastname: Buffy
authors.forename: Nathaniel J
authors.initials: NJ
authors.lastname: Traaseth
authors.forename: Gianluigi
authors.initials: G
authors.lastname: Veglia
authors.forename: William W
authors.initials: WW
authors.lastname: Brey
mesh_terms: D001704:Biopolymers / Q000737:chemistry* / Q000528:radiation effects*; D017076:Computer-Aided Design; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006361:Heating / Q000295:instrumentation; D006358:Hot Temperature; D008051:Lipid Bilayers / Q000737:chemistry* / Q000528:radiation effects*; D009682:Magnetic Resonance Spectroscopy / Q000295:instrumentation* / Q000379:methods; D008280:Magnetics / Q000295:instrumentation*; D011208:Powders; D011846:Radio Waves; D013048:Specimen Handling / Q000295:instrumentation / Q000379:methods; D013696:Temperature; D014159:Transducers
chemical_list: D001704:Biopolymers; D008051:Lipid Bilayers; D011208:Powders