Cryogenic sample exchange NMR probe for magic angle spinning dynamic nuclear polarization.

Area of Science:

• Biophysics
• Analytical Chemistry
• Spectroscopy

Background:

• Conventional magic angle spinning (MAS) dynamic nuclear polarization (DNP) experiments require lengthy sample changes, involving probe warming, disconnections, and reassembly, taking several hours.
• This downtime limits experimental throughput and can affect long-term instrument stability in cryogenic DNP/NMR studies.

Purpose of the Study:

• To introduce and validate a novel cryogenic sample exchange system for MAS DNP experiments.
• To demonstrate the system's ability to reduce sample exchange time and improve overall experimental efficiency and stability.

Main Methods:

• Development of a cryogenic sample exchange system featuring an eject pipe and a vacuum-jacketed dewar with a bellowed hole.
• Implementation of the system on a quadruple resonance probe for MAS DNP/NMR.
• Performance of high-precision distance measurements on bacteriorhodopsin and acquisition of a spectrum for N-f-MLF-OH.

Main Results:

• The new system dramatically reduces sample exchange time compared to conventional methods.
• High sensitivity, resolution, and stability were achieved, as demonstrated by experiments on bacteriorhodopsin.
• A spectrum of N-f-MLF-OH at 100K exhibited narrow linewidths of 30 Hz.

Conclusions:

• The developed cryogenic sample exchange system significantly enhances the efficiency and stability of MAS DNP experiments.
• This technological advancement facilitates more streamlined and reliable DNP/NMR investigations, particularly for complex biological systems.