[NMR paper] DNP-enhanced MAS NMR of Bovine Serum Albumin Sediments and Solutions.

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DNP-enhanced MAS NMR of Bovine Serum Albumin Sediments and Solutions.

DNP-enhanced MAS NMR of Bovine Serum Albumin Sediments and Solutions.

J Phys Chem B. 2014 Jan 24;

Authors: Ravera E, Corzilius B, Michaelis VK, Luchinat C, Griffin RG, Bertini I

Abstract
Protein sedimentation sans cryoprotection is a new approach to magic angle spinning (MAS) and dynamic nuclear polarization (DNP) nuclear magnetic resonance (NMR) spectroscopy of proteins. It increases the sensitivity of the experiments by a factor of ~4.5 in comparison to the conventional DNP sample preparation and circumvents intense background signals from the cryoprotectant. In this paper we investigate sedimented samples and concentrated frozen solutions of natural abundance bovine serum albumin (BSA) in the absence of a glycerol-based cryoprotectant. We observe DNP signal enhancements ?~66 at 140 GHz in a BSA pellet sedimented from an aqueous solution containing the biradical polarizing agent TOTAPOL and compare this with samples prepared using the conventional protocol (i.e., dissolution of BSA in a glycerol/water cryoprotecting mixture). The dependence of DNP parameters on the radical concentration points to the presence of an interaction between TOTAPOL and BSA, so much so that a frozen solution sans cryoprotectant still gives ?~50. We also tested the binding behavior of SPIROPOL and found it to interact and to give ?~26 close to its maximum achievable concentration. Under these conditions TOTAPOL gives ?~31, pointing to a less efficient interaction of SPIROPOL but to a similar efficiency when fully bound. Altogether, these results demonstrate that DNP is feasible in self-cryoprotecting samples.


PMID: 24460530 [PubMed - as supplied by publisher]



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