A temperature-jump NMR probe setup using rf heating optimized for the analysis of temperature-induced biomacromolecular kinetic processes

Abstract

A novel temperature jump (T-jump) probe operational at B0 fields of 600MHz (14.1Tesla) with an integrated cage radio-frequency (rf) coil for rapid (<1s) heating in high-resolution (HR) liquid-state NMR-spectroscopy is presented and its performance investigated. The probe consists of an inner 2.5mm “heating coil” designed for generating rf-electric fields of 190–220MHz across a lossy dielectric sample and an outer two coil assembly for 1H-, 2H- and 15N-nuclei. High B0 field homogeneities (0.7Hz at 600MHz) are combined with high heating rates (20–25K/s) and only small temperature gradients (<±1.5K, 3s after 20K T-jump). The heating coil is under control of a high power rf-amplifier within the NMR console and can therefore easily be accessed by the pulse programmer. Furthermore, implementation of a real-time setup including synchronization of the NMR spectrometer’s air flow heater with the rf-heater used to maintain the temperature of the sample is described. Finally, the applicability of the real-time T-jump setup for the investigation of biomolecular kinetic processes in the second-to-minute timescale is demonstrated for samples of a model 14mer DNA hairpin and a 15N-selectively labeled 40nt hsp17-RNA thermometer.