title: Dynamic nuclear polarization of sedimented solutes.
abstract: Using the 480 kDa iron-storage protein complex, apoferritin (ApoF), as an example, we demonstrate that sizable dynamic nuclear polarization (DNP) enhancements can be obtained on sedimented protein samples. In sedimented solute DNP (SedDNP), the biradical polarizing agent is co-sedimented with the protein, but in the absence of a glass-forming agent. We observe DNP enhancement factors ε > 40 at a magnetic field of 5 T and temperatures below 90 K, indicating that the protein sediment state is "glassy" and suitable to disperse the biradical polarizing agent upon freezing. In contrast, frozen aqueous solutions of ApoF yield ε ≈ 2. Results of SedDNP are compared to those obtained from samples prepared using the traditional glass-forming agent glycerol. Collectively, these and results from previous investigations suggest that the sedimented state can be functionally described as a "microcrystalline glass" and in addition provide a new approach for preparation of samples for DNP experiments.
authors: Department of Chemistry Ugo Schiff and Magnetic Resonance Center (CERM), University of Florence, 50019 Sesto Fiorentino (FI), Italy.
authors: Enrico
authors: E
authors: Ravera
authors: Björn
authors: B
authors: Corzilius
authors: Vladimir K
authors: VK
authors: Michaelis
authors: Camilla
authors: C
authors: Rosa
authors: Robert G
authors: RG
authors: Griffin
authors: Claudio
authors: C
authors: Luchinat
authors: Ivano
authors: I
authors: Bertini
mesh_terms: D001052:Apoferritins / Q000737:chemistry*; D060526:Magnetic Fields; D019906:Nuclear Magnetic Resonance, Biomolecular; D012996:Solutions; D013696:Temperature
chemical_list: D012996:Solutions; D001052:Apoferritins