A new polarized target for neutron scattering studies on biomolecules: first results from apoferritin and the deuterated 50S subunit of ribosomes

Abstract

A new polarized target for neutron scattering has been designed by CERN and tested successfully using the reactor FRG‐1 at the GKSS Research Centre. The nuclear spins are aligned with respect to the external field – parallel or antiparallel – by dynamic nuclear polarization (DNP). To avoid absorption of neutrons by 3He, the frozen solutions of biomolecules are immersed in liquid 4He which in turn is thermally coupled to the cooling mixture of 3He/4He of the dilution refrigerator. Compared with earlier experiments where the sample had been cooled directly by 3He, the rate of detectable neutrons increased by a factor of 30. Another factor of 30 is due to the installation of the cold source and the beryllium reflector in FRG‐1. Polarized neutron scattering from apoferritin in deuterated solvent shows that the proton spin polarization is homogeneous in apoferritin molecules. After saturation of proton nuclear magnetic resonance (NMR), polarized neutron scattering is dominated by deuteron spin contrast. With the deuterated large subunit of E. coli ribosomes, three different basic scattering functions are derived from spin‐contrast variation, reflecting the known scattering‐length‐density distribution of the architecture of rRNA and ribosomal proteins. The planned in situ structure determination of a mRNA fragment is discussed in the light of the present results.

Direct localization of the tRNAs within the elongating ribosome by means of neutron scattering (proton-spin contrast-variation)

“…Nevertheless, the extremely unfavorable ratio of coherent/incoherent scattering intensities of neutrons scattered by protons was the principal obstacle to a structural analysis with these techniques. (Knop et al, 1992) Rocek (1979, 1985) (Scha È rpf, 1989). The alignment of the proton spins in the sample with respect to an external magnetic ®eld is achieved by dynamic nuclear spin polarization (DNP; e.g.…”

Contrast variation by dynamic nuclear polarization and time-of-flight small-angle neutron scattering. I. Application to industrial multi-component nanocomposites

“…After that pioneering work, several papers reported the utilization of proton spin polarization in neutron scattering experiments (Kohgi et al, 1987;Knop et al, 1992;Fermon et al, 1992;Grinten et al, 1995;Brandt et al, 2006Brandt et al, , 2007Noda et al, 2009Noda et al, , 2011Noda et al, , 2013Kumada et al, 2010;Stuhrmann, 2015). Bunyatova (2004) originally developed the vapour sorption technique of TEMPO [(2,2,6,6-tetramethylpiperidine-1-yl) Figure 2 Chemical structure formulae of (a) TEMPO and (b) styrene-butadiene random copolymer, SBR.…”

Small-angle scattering and its interplay with crystallography, contrast variation in SAXS and SANS

“…In the mid 80's, several groups embarked on experiments of polarized SANS from dynamically polarized proton spins in crown ethers (Kohgi et al, 1987), polymers (Glä ttli et al, 1989) and biological macromolecules (Knop et al, 1986(Knop et al, , 1992. All of them took advantage of a new type of polarized target material which had been optimized for high-energy-physics experiments.…”