High-resolution NMR field-cycling device for full-range relaxation and structural studies of biopolymers on a shared commercial instrument
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Improvements are described in a shuttling field-cycling device (Redfield in Magn Reson Chem 41:753–768, 2003), designed to allow widespread access to this useful technique by configuring it as a removable module to a commercial 500 MHz NMR instrument. The main improvements described here, leading to greater versatility, high reliability and simple construction, include: shuttling provided by a linear motor driven by an integrated-control servomotor; provision of automated bucking magnets to allow fast two-stage cycling to nearly zero field; and overall control by a microprocessor. A brief review of history and publications that have used the system is followed by a discussion of topics related to such a device including discussion of some future applications. A description of new aspects of the shuttling device follows. The minimum round trip time to 1T and above is less than 0.25 s and to 0.002 T is 0.36 s. Commercial probes are used and sensitivity is that of the host spectrometer reduced only by relaxation during travel. A key element is development of a linkage that prevents vibration of the linear motor from reaching the probe.
KeywordsDynamics Relaxation dispersion Sample shuttle Commercial instrument Motor drive
This development was supported by National Institutes of Health grant GM077974, and, previously, grant CHE-0109575 from the National Science Foundation Chemical Instrumentation Program, and grant 36680-ACF from the American Chemical Society Petroleum Research Fund. Marcel Reese suggested the use of a servomotor, and its supplier, for this device. We thank our research collaborators, especially Mary Roberts, for performing much of the research reviewed here, and helping prepare the figures. David Roberts provided the photographs, and Thomas Pochapsky kindly read this manuscript. We received much technical help from many individuals in building this shuttler, especially from Frank Mello who fabricated parts for us as well as providing many useful suggestions, and Annemarie Rom-Weisenbach for expert programming. We thank Tai-huang Huang for sending us the recent paper describing the new shuttle design (Chou et al. 2011).
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