a b s t r a c tDiscrimination of tRNA Gln is an integral function of several bacterial glutamyl-tRNA synthetases (GluRS). The origin of the discrimination is thought to arise from unfavorable interactions between tRNA Gln and the anticodon-binding domain of GluRS. From experiments on an anticodon-binding domain truncated Escherichia coli (E. coli) GluRS (catalytic domain) and a chimeric protein, constructed from the catalytic domain of E. coli GluRS and the anticodon-binding domain of E. coli glutaminyl-tRNA synthetase (GlnRS), we show that both proteins discriminate against E. coli tRNA Gln . Our results demonstrate that in addition to the anticodon-binding domain, tRNA Gln discriminatory elements may be present in the catalytic domain in E. coli GluRS as well.
21 , similar results for the two non-equivalent sites have been found but site fractions are in reverse order. In this alloy, a different contaminating phase, possibly due to HfNi 3 , has been found from PAC measurements but is not found from XRD measurement. Density functional theory (DFT) based calculations of electric field gradient (EFG) and asymmetry parameter (η) at the sites of 181 Ta probe nucleus allowed us to assign the observed EFG fractions to the various lattice sites in (Zr/Hf) 8 Ni 21 compounds.
From temperature dependent perturbed angular correlation (PAC) measurements (77–873 K) in equiatomic TiNi intermetallic alloy, martensitic phase transformations have been observed. Three frequency components corresponding to three different phases of TiNi have been found in the temperature range 298–873 K. The results of quadrupole frequency and asymmetry parameters at room temperature are found to be: ωQ = 14(1) Mrad/s, η = 0 (33%), ωQ = 40.0(5) Mrad/s, η = 0.66(3) (52%) and ωQ = 56.7(3)Mrad/s, η = 0.39(2) (15%). The frequency component with η = 0 and which enhances to ~52% at 373 K can be attributed to the cubic austenite phase. The predominant component (~52%) found at room temperature has been attributed to monoclinic martensitic phase of TiNi and the third component with values of ωQ and η similar to those for the martensitic phase is attributed to the intermediate orthorhombic phase. At 77 K, no intermediate and austenite phases have been found but only the martensite phase is observed at this temperature. From XRD measurements at room temperature also, three phases of TiNi have been observed.
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