A capacitively coupled temperature-jump arrangement for high-resolution biomolecular NMR

Abstract

A simple design for performing rapid temperature jumps within a high-resolution nuclear magnetic resonance (NMR) setting is presented and exemplified. The design is based on mounting, around a conventional NMR glass tube, an inductive radiofrequency (RF) irradiation coil that is suitably tuned by a resonant circuit and is driven by one of the NMR's console high-power RF amplifiers. The electric fields generated by this coil's thin metal strips can lead to a fast and efficient heating of the sample, amounting to temperature jumps of ≈ 20 °C in well within a second-particularly in the presence of lossy dielectric media like those provided by physiological buffers. Moreover, when wound around a 4-mm NMR tube, the resulting device fits a conventional 5-mm inverse probe and is wholly compatible with the field homogeneities and sensitivities expected for high-resolution biomolecular NMR conditions. The performance characteristics of this new system were tested using saline solutions, as well as on a lyotropic liquid crystal capable of undergoing nematic → isotropic transitions in the neighborhood of ambient temperature. These settings were then incorporated into the performance of a new kind of single-scan 2D NMR spectroscopy acquisition, correlating the anisotropic and isotropic patterns elicited by solutes dissolved in such liquid-crystalline systems, before and after a sudden temperature jump occurring during an intervening mixing period.