Crystallization of Arthrobacter sp. strain 1C N-(1-D-carboxyethyl)-L-norvaline dehydrogenase and its complex with NAD+

The novel NAD+-linked opine dehydrogenase from a soil isolate Arthrobacter sp. strain 1C belongs to an enzyme superfamily whose members exhibit quite diverse substrate specificites. Crystals of this opine dehydrogenase, obtained in the presence or absence of co-factor and substrates, have been shown to diffract to beyond 1.8 ? resolution. X-ray precession photographs have established that the crystals belong to space group P21212, with cell parameters a = 104.9, b = 80.0, c = 45.5 ? and a single subunit in the asymmetric unit. The elucidation of the three-dimensional structure of this enzyme will provide a structural framework for this novel class of dehydrogenases to enable a comparison to be made with other enzyme families and also as the basis for mutagenesis experiments directed towards the production of natural and synthetic opine-type compounds containing two chiral centres.     

Excited state production and temperature measurement in a heavy ion reaction

An effective temperature inferred from the slope of kinetic energy spectra of the emitted fragments is not reflected in the relative populations of excited states of the emitted nuclei. We found that the excited state populations of ⁶Li, ⁷Li and ⁷Be emitted near 90° in the lab from the reaction of 490 MeV ¹⁴N with Ag are significantly lower than those expected on the basis of their effective temperature.     

Helium induced pressure broadening and shifting of HCN hyperfine transitions between 1.3 and 20 K

We have measured the helium induced pressure broadening and shifting of the distinct hyperfine components of the j = 1 <-- 0 and j = 2 <-- 1 transitions of HC14N at temperatures between 1.3 and 20 K. The HCN molecules were cooled to these temperatures using the collisional cooling technique. As a test of this cooling technique we measured the Doppler contribution to the spectral lines, and these measurements confirm that the molecules are at the same temperature as the walls of the spectroscopic cell. We observed that the hyperfine components of the 2 <-- 1 transition have distinct broadening coefficients that differ from one another by as much as 5%. The measured differences are in reasonable agreement with theoretical predictions. We have also performed molecular scattering calculations on three He-HCN potential energy surfaces in order to compare our results with theoretical expectations. At the lowest temperatures these calculations predict broadening coefficients that are considerably larger than the measured coefficients. We have previously found a similar discrepancy for two other molecules at these low temperatures, and we discuss possible experimental and theoretical origins for this persistent discrepancy.     

Reaction filters. Charged-particle multiplicity and linear momentum transfer

The relation between charged-particle multiplicity and linear momentum transfer to heavy reaction residues has been investigated with a 4π charged-particle detector for the reactions ³⁶Ar+²³⁸U at E/A=35 MeV and ¹⁴N+²³⁸U at E/A=50 MeV. The multiplicity of charged particles at backward angles (θ > 35°) incrreases linear momentum transfer while the multiplicity of charged particles in the forward direction is almost independent of the linear momentum transfer.     

Observation of particle alignment in the octupole band of 172Yb

Members of the octupole band up to spin 14^? have been identified with the ${}^{170}\text{Er}\text{(α,2}\text{n}\text{)}{}^{172}\text{Yb}$ reaction. The band is strongly perturbed by Coriolis effects and has a high moment of inertia with variations characteristic of particle alignment. Vabrational alignment is insufficient to explain the data.     

Mean life of the 854 keV 02+ state in 74Se and the coexistence model

The mean life of the first excited 0₂⁺ state in ⁷⁴Se, only 219 keV above the first excited 2⁺ state at 635 keV, was measured to be 1.2±0.2 nsec, with delayed coincidence techniques. The 0₂⁺ state was populated by the decay of ⁷⁴Br produced via the ⁶⁰Ni(¹⁶O, pn)⁷⁴Br reaction. The extracted B(E2; 0₂⁺ → 20₁⁺) value is 14±2 s.p.u. which suggests that the 0₂⁺ state is collective. Application of a coexistence model in terms of spherical and deformed shapes is discussed for ⁷⁴Se.     

Fragment spin distribution in 400 MeV40Ar+93Nb collisions investigated by light-particle anisotropies

In and out-of-plane angular correlations between light particles and projectile-like fragments from deeply inelastic collisions of 400 MeV⁴⁰Ar+⁹³Nb were measured. At backward angles, the equilibrium emission of a particles and protons from the target-like fragment was identified. By analysing the out-of-plane angular correlations in the framework of a semi-classical statistical model, an average spin of 30±2? and an average alignment ofP _zz =0.80±0.15 for the target-like fragment were deduced.