Cryogenic sample exchange NMR probe for magic angle spinning dynamic nuclear polarization.
We describe a cryogenic sample exchange system that dramatically improves the efficiency of magic angle spinning (MAS) dynamic nuclear polarization (DNP) experiments by reducing the time required to change samples and by improving long-term instrument stability. Changing samples in conventional cryogenic MAS DNP/NMR experiments involves warming the probe to room temperature, detaching all cryogenic, RF, and microwave connections, removing the probe from the magnet, replacing the sample, and reversing all the previous steps, with the entire cycle requiring a few hours. The sample exchange system described here-which relies on an eject pipe attached to the front of the MAS stator and a vacuum jacketed dewar with a bellowed hole-circumvents these procedures. To demonstrate the excellent sensitivity, resolution, and stability achieved with this quadruple resonance sample exchange probe, we have performed high precision distance measurements on the active site of the membrane protein bacteriorhodopsin. We also include a spectrum of the tripeptide N-f-MLF-OH at 100K which shows 30 Hz linewidths.
Barnes
Alexander B
AB
Department of Chemistry and Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Mak-Jurkauskas
Melody L
ML
Matsuki
Yoh
Y
Bajaj
Vikram S
VS
van der Wel
Patrick C A
PC
Derocher
Ronald
R
Bryant
Jeffrey
J
Sirigiri
Jagadishwar R
JR
Temkin
Richard J
RJ
Lugtenburg
Johan
J
Herzfeld
Judith
J
Griffin
Robert G
RG
D001436:Bacteriorhodopsins / Q000737:chemistry; D003080:Cold Temperature; D008239:Lysine / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy / Q000295:instrumentation / Q000379:methods*; D008872:Microwaves; D009584:Nitrogen; D055100:Optical Fibers; D012172:Retinaldehyde / Q000737:chemistry; D013056:Spectrophotometry, Ultraviolet; D013696:Temperature
D001436:Bacteriorhodopsins; D008239:Lysine; D009584:Nitrogen; D012172:Retinaldehyde