Limit analysis of rectangular R.C. slabs on ground

A method is presented for obtaining lower bound on the carrying capacity of reinforced concrete foundation slab-structures subject to non-uniform contact pressure distributions. Functional approach suggested by Vallance for simply supported square slabs subject to uniform pressure distribution has been extended to simply supported rectangular slabs subject to symmetrical non-uniform pressure distributions. Radial solutions, ideally suited for rotationally symmetric problems, are shown to be adoptable for regular polygonal slabs subject to contact pressure paraboloids with constant edge pressures. The functional approach has been shown to be well suited even when the pressure is varying along the edges.

1-[(2-Chloro-8-methylquinolin-3-yl)methyl]pyridin-2(1H)-one

In the title compound, C16H13ClN2O, the quinoline ring system is approximately planar [maximum deviation 0.021 (2) angstrom] and forms a dihedral angle of 85.93 (6)degrees with the pyridone ring. Intermolecular C-H center dot center dot center dot O hydrogen bonding, together with weak C-H center dot center dot center dot pi and pi-pi interactions [centroid-to-centroid distances 3.5533 (9) and 3.7793 (9) angstrom], characterize the crystal structure.

1,3,6-Trimethylpyrano[4,3-b]pyrrol-4(1H)-one

All the non-H atoms of the title compound, C10H11NO2, are almost coplanar [maximum deviation = 0.040 (3) angstrom]. The crystal structure is stabilized by C-H center dot center dot center dot O hydrogen bonds.

2-Chloro-8-methyl-3-[(pyrimidin-4-yloxy)methyl]quinoline

In the title compound, C15H12ClN3O, the quinoline ring system is essentially planar, with a maximum deviation of 0.017 (1) angstrom. The crystal packing is stabilized by pi-pi stacking interactions between the quinoline rings of adjacent molecule, with a centroid-centroid distance of 3.5913 (8) angstrom. Aweak C-H center dot center dot center dot pi contact is also observed between molecules.

5-(4-Chlorophenyl)-3-(2,4-dimethylthiazol-5-yl)-1,2,4-triazolo[3,4-a]isoquinoline

In the title molecule, C21H15ClN4S, the triazoloisoquinoline ring system is approximately planar, with an r.m.s. deviation of 0.054 (2) angstrom and a maximum deviation of 0.098 (2) angstrom from the mean plane for the triazole ring C atom that is bonded to the thiazole ring. The thiazole and benzene rings are twisted by 66.36 (7) and 56.32 (7)degrees respectively, with respect to the mean plane of the triazoloisoquinoline ring system. In the crystal structure, molecules are linked by intermolecular C-H center dot center dot center dot N interactions along the a axis. The molecular conformation is stabilized by a weak intramolecular pi-pi interaction involving the thiazole and benzene rings, with a centroid-centroid distance of 3.6546 (11) angstrom . In addition, two other intermolecular pi-pi stacking interactions are observed, between the triazole and benzene rings and between the dihydropyridine and benzene rings [centroid-centroid distances = 3.6489 (11) and 3.5967 (10) angstrom, respectively].

Cloning, expression, purification, crystallization and preliminary X-ray crystallographic study of the putative SAICAR synthetase (PH0239) from Pyrococcus horikoshii OT3

The study of proteins involved in de novo biosynthesis of purine nucleotides is central in the development of antibiotics and anticancer drugs. In view of this, a protein from the hyperthermophile Pyrococcus horikoshii OT3 was isolated, purified and crystallized using the microbatch method. Its primary structure was found to be similar to that of SAICAR synthetase, which catalyses the seventh step of de novo purine biosynthesis. A diffraction-quality crystal was obtained using Hampton Research Crystal Screen II condition No. 34, consisting of 0.05 M cadmium sulfate hydrate, 0.1 M HEPES buffer pH 7.5 and 1.0 M sodium acetate trihydrate, with 40%(v/v) 1,4-butanediol as an additive. The crystal belonged to space group P3(1), with unit-cell parameters a = b = 95.62, c = 149.13 angstrom. Assuming the presence of a hexamer in the asymmetric unit resulted in a Matthews coefficient (V-M) of 2.3 angstrom(3) Da(-1), corresponding to a solvent content of about 46%. A detailed study of this protein will yield insights into structural stability at high temperatures and should be highly relevant to the development of antibiotics and anticancer drugs targeting the biosynthesis of purine nucleotides.

Structure and electron transport anomalies in InSe-In6Se 7 composite

Rapid solidification of an equiatomic In-Se alloy resulted in the formation of an equilibrium InSe-In6Se7 phase mixture. The InSe phase was found to be polytypic and exhibited the structural variants 2H, 3H, and 4H. The 4H polytype was found to be in considerably higher proportion compared to 2H and 3H types. The In6Se7 phase was found to be hexagonal with a=0.8919 nm and c=1.4273 nm. Both In6Se 7 and the polytypes of InSe could be identified with the space group P61. The conductivity σ variation with temperature was found to be similar to that observed in disordered semiconducting materials. For temperatures >200 K, ln σ decreased linearly with T-1, phonon-assisted carrier excitation. For temperatures <200 K, ln σ decrease followed T-1/3 behavior, representative of variable-range hopping conduction of electrons.

The Critical Role of N- and C-Terminal Contact in Protein Stability and Folding of a Family 10 Xylanase under Extreme Conditions

Background: Stabilization strategies adopted by proteins under extreme conditions are very complex and involve various kinds of interactions. Recent studies have shown that a large proportion of proteins have their N- and C-terminal elements in close contact and suggested they play a role in protein folding and stability. However, the biological significance of this contact remains elusive. Methodology: In the present study, we investigate the role of N- and C-terminal residue interaction using a family 10 xylanase (BSX) with a TIM-barrel structure that shows stability under high temperature,alkali pH, and protease and SDS treatment. Based on crystal structure,an aromatic cluster was identified that involves Phe4, Trp6 and Tyr343 holding the Nand C-terminus together; this is a unique and important feature of this protein that might be crucial for folding and stabilityunder poly-extreme conditions. Conclusion: A series of mutants was created to disrupt this aromatic cluster formation and study the loss of stability and function under given conditions. While the deletions of Phe4 resulted in loss of stability, removal of Trp6 and Tyr343 affected in vivo folding and activity. Alanine substitution with Phe4, Trp6 and Tyr343 drastically decreased stability under all parameters studied. Importantly,substitution of Phe4 with Trp increased stability in SDS treatment.Mass spectrometry results of limited proteolysis further demonstrated that the Arg344 residue is highly susceptible to trypsin digestion in sensitive mutants such as DF4, W6A and Y343A, suggesting again that disruption of the Phe4-Trp6-Tyr343 (F-W-Y) cluster destabilizes the N-and C-terminal interaction. Our results underscore the importance of N- and C-terminal contact through aromatic interactions in protein folding and stability under extreme conditions, and these results may be useful to improve the stability of other proteins under suboptimal conditions.

(2-Chloro-8-methylquinolin-3-yl)methanol

The molecule of title compound, C11H10ClNO, is close to being planar (r.m.s deviation for the non-H atoms = 0.017 angstrom). In the crystal, molecules interact by way of O-H center dot center dot center dot O hydrogen bonds, generating C(2) chains propagating in [010]. The crystal structure is consolidated by C-H center dot center dot center dot pi interactions and aromatic pi-pi stacking interactions [centroid-centroid distance = 3.661 (2) angstrom].

(2-Chloro-6-methylquinolin-3-yl)methanol

The title compound, C11H10ClNO, is close to being planar (r.m.s deviation for the non-H atoms = 0.026 angstrom). In the crystal,molecules are linked by O-H center dot center dot center dot O hydrogen bonds, generating C(2) chains, and weak C-H center dot center dot center dot pi interactions and aromatic pi-pi stacking interactions [centroid-centroid distance = 3.713 (3) angstrom] help to consolidate the sturcture.

3-[(2-Chloro-6-methylquinolin-3-yl)methyl]quinazolin-4(3H)-one

In the title molecule, C19H14ClN3O, the quinoline and quinazoline ring systems form a dihedral angle of 80.75 (4)degrees. In the crystal, the molecules are linked by pairs of C-H center dot center dot center dot N hydrogen bonds into centrosymmetric dimers, generating R-2(2)(6) ring motifs. The structure is further stabilized by C-H center dot center dot center dot pi interactions and pi-pi stacking interactions [centroid-centroid distances = 3.7869 (8) and 3.8490 (8) angstrom].

(Z)-2-(2-Isopropyl-5-methylphenoxy)-N`-(2-oxoindolin-3-ylidene)acetohydrazide

In the title Mannich base, C20H21N3O3, an isatin derivative of thymol the O-CH2-C(=O)-N(H)-N fragment connecting the aromatic and fused-ring systems is approximately planar, with the N-N single bond in a Zmconfiguration. The amino H atom of this N-N fragment is intramolecularly hydrogen bonded to the carbonyl O atom of the indolinone fused ring as well as to the phenoxy O atom of the aromat ring. The amino H atom of the indoline fused ring forms a hydrogen bond with the double-bond O atom of an adjacent molecule, this hydrogen bond giving rise to a linear chain motif.