Nuclear spin relaxation in proteins and models at low temperature

✍ Scribed by Eric A. Marshall; Robert G. Bryant

• Publisher: John Wiley and Sons
• Year: 1992
• Tongue: English
• Weight: 334 KB
• Volume: 30
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.1260300310

✦ Synopsis

Abstract

^13^C NMR spectra were obtained using cross‐polarization methods at temperatures near 5 K to examine the magnetization transfer spin dynamics and the practicality of routinely making low‐temperature measurements as a means for gaining sensitivity. The magnetization transfer rate between protons and carbon was generally found to be more rapid at 5 K than at room temperature, and the proton and carbon relaxation times in the rotating frame were considerably longer. Both conspire to improve the sensitivity of the cross‐polarization experiment. The limiting factor in the ease of executing the experiment rapidly is the value for the proton spin–lattice relaxation time, which in samples with few methyl groups may become much longer than is common at higher temperatures. However, when the methyl group concentration is high, the proton spin–lattice relaxation rate at 5 K may be in the range of seconds, making the low‐temperature experiment a highly sensitive and practical opportunity.