Prevalence of the thioamide {···H-N-C=S}2 synthon-solid-state (X-ray crystallography), solution (NMR) and gas-phase (theoretical) structures of O-methyl-N-aryl-thiocarbamides

Structural investigations, i.e. solid-state (X-ray), solution (¹H NMR) and gas-phase (theoretical), on molecules with the general formula MeOC(S)N(H)C₆H₄-4-Y: Y = H (1), NO₂ (2), C(O)Me (3), Cl (4) have shown a general preference for the adoption of an E-conformation about the central C–N bond. Such a conformation allows for the formation of a dimeric hydrogen-bonded {H–N–C=S}₂ synthon as the building block. In the cases of 1–3, additional C–H^...O interactions give rise to the formation of tapes of varying topology. A theoretical analysis shows that the preference for the E-conformation is about the same as the crystal packing stabilisation energy and consistent with this, the compound with Y = C(O)OMe, (5), adopts a Z-conformation in the solid-state that facilitates the formation of N–H^...O, C–H^...O and C–H^...S interactions, leading to a layer structure. Global crystal packing considerations are shown to be imperative in dictating the conformational form of molecules 1–5.

Experiment and theoretical prediction of martensitic transformation crystallography in a Ni–Mn–Ga ferromagnetic shape memory alloy

A detailed study of martensitic transformation crystallography and microstructural characteristics in the Ni53Mn25Ga22 ferromagnetic shape memory alloy (FSMA) was performed by both experimental observation and theoretical calculation. It is revealed that there are two microscopically twin-related martensitic variants with a misorientation of ∼82° around the 〈1 1 0〉_M axis in each initial austenite grain. The twin interface plane was determined to be {0.399 0.383 0.833}_M (1.79° away from {1 1 2}_M). The ratio of the amounts of the two variants inherited from one single austenite grain is about 1.70. The prevalent orientation relationship between austenite and martensite was found to be Kurdjumov–Sachs (K–S) relationship with (1 1 1)_A//(1 0 1)_M, [110]A//[111]_M. A successful explanation of the crystallographic features during martensitic transformation will shed light on the development of FSMAs with optimal performance.

X-ray crystallography : applications in the biotechnology research

X-ray crystallography is essentially a form of very high resolution microscopy. It enables us to visualize protein structures at the atomic level and enhances our understanding of protein function. Specifically we can study how proteins interact with other molecules, how they undergo conformational changes, and how they perform catalysis in the case of enzymes. Armed with this information we can design novel drugs that target a particular protein, or rationally engineer an enzyme for a specific industrial process.