A comparative study for the intermediate states of myelin oligodendrocyte glycoprotein in the absence and presence of glycan - A computational approach.

Myelin Oligodendrocyte glycoprotein (MOG) is found to play an important role in providing structural integrity to myelin sheath at the same time it acts as an auto-antigen which might lead to Multiple Sclerosis (MS). What causes this specific property of being an auto-antigen is still not known. Here we present molecular dynamics simulation studies of unfolding and folding of the protein MOG in both the absence and presence of N-glycan in order to understand the role of glycosylation in the stability and flexibility of the protein. The main results from these studies show that the glycosylation increases the stability of the protein MOG and inhibits the complete unfolding of MOG in the SMD. From the folding studies using TMD, it was observed that the glycan helps the protein to attain the near-native folded conformation. However, it was also observed from the direct TMD studies that the pathway of protein folding was enhanced by the trace-back of intermediate states in the presence of glycan.

Cloning, expression, crystallization and preliminary X-ray crystallographic analysis of aspartyl aminopeptidase from the apeB gene of Pseudomonas aeruginosa.

Aminopeptidases (APs) are a group of exopeptidases that catalyze the removal of amino acids from the N-termini of proteins and peptides. The APs are ubiquitous in nature and are of critical biological and medical importance because of their key role in protein degradation. Pseudomonas aeruginosa aspartyl aminopeptidase (PaAAP), which is encoded by the apeB gene, was expressed in Escherichia coli, purified and crystallized using the microbatch method. A preliminary structural study has been performed using the X-ray crystallographic method. The PaAAP crystal diffracted to 2.0 Å resolution and belonged to the rhombohedral space group H3, with unit-cell parameters a = b = 133.6, c = 321.2. The unit-cell volume of the crystal is compatible with the presence of four monomers in the asymmetric unit, with a corresponding Matthews coefficient V(M) of 2.95 Å(3) Da(-1) and a solvent content of 58.3%.

1'-Methyl-4'-phenyl-2''-sulfanylidene-dispiro-[indoline-3,2'-pyrrolidine-3',5''-1,3-thia-zolidine]-2,4''-dione.

The title compound, C(20)H(17)N(3)O(2)S(2), crystallizes with two mol-ecules in the asymmetric unit. The pyrrolo-dine rings have envelope conformations in both mol-ecules, the N atoms deviating by 0.574 (3) and 0.612 (2) Šfrom the mean planes through the other ring atoms. The 1'-methyl and 4'-phenyl groups on the pyrrolidine rings are substituted in equatorial positions. In the crystal, mol-ecules are linked into a three-dimensional network by N-H⋯O, N-H⋯N and C-H⋯O and N-H⋯π hydrogen bonds.

(Z)-2-[(4-Methyl-phen-yl)sulfon-yl]-1,2-diphenyl-ethene-selenol.

In the title compound, C(21)H(18)O(2)SSe, the dihedral angle between the cis phenyl rings is 64.3 (1)° and those between the toluene and the phenyl rings are 21.1 (2) and 72.0 (1)°, respectively. An intra-molecular Se-H⋯O hydrogen bond occurs. In the crystal, mol-ecules are connected by C-H⋯O hydrogen bonds and weak C-H⋯π inter-actions help to consolidate the crystal packing.

4-Amino-3-(4-chloro-phen-yl)-1H-1,2,4-triazole-5(4H)-thione.

In the title compound, C(8)H(7)ClN(4)S, the benzene ring is statistically disordered over two conformations rotated about the Cl-C⋯C-C axis, which subtend dihedral angles of 24.7 (3) and 9.9 (2) ° with respect to the triazole ring. An intra-molecular C-H⋯N close contact occurs. In the crystal, N-H⋯N and N-H⋯S hydrogen bonds link the mol-ecules into (001) sheets: R(2) (2)(8) and R(2) (2)(10) graph-set motifs result. Weak C-H⋯N hydrogen bonds and aromatic π-π stacking inter-actions [shortest centroid-centroid separation = 3.681 (7) Å] complete the structure.

2,4-Diamino-5-(4-chloro-phen-yl)-6-ethyl-pyrimidin-1-ium 2-acet-amido-benzoate.

The title compound, C(12)H(14)ClN(4) (+)·C(9)H(8)NO(3) (-), is a salt with a 1:1 ratio of cation and anion components inter-acting with each other forming an R(2) (2)(8) ring motif. The crystal structure is stabilized by hydrogen bonds (N-H⋯O) involving two different eight-membered rings. One of them is formed between the pyrimidine ring (donor) and the carboxylate group (acceptor) from the benzoate, whereas the other ring is formed by N-H⋯O interactions, which help to form a dimer between two symmetry-related salts in the unit cell. In addition, an intramolecular C-H⋯N and intermolecular C-H⋯Cl interactions help to control the molecules in the unit-cell packing.

2,4-Diamino-5-(4-chloro-phen-yl)-6-ethyl-pyrimidin-1-ium 2-propanamido-benzoate.

In the title salt, C(12)H(14)ClN(4) (+)·C(10)H(10)NO(3) (-), zwitterionic N-H⋯O inter-actions form an R(2) (2)(8) ring. The crystal structure is stabilized by N-H⋯O and N-H⋯N hydrogen bonds involving two different eight-membered rings. An N-H⋯O inter-action occurs between the pyrimidine ring (donor) and carboxyl-ate group (acceptor) while the other ring is formed by N-H⋯N inter-actions, which form a dimer between two symmetry-related salts. An intra-molecular N-H⋯O hydrogen bond forms a six-membered ring in the benzoate. Inter-molecular C-H⋯O inter-actions are also observed.

3-Nitroso-2,4,6,8-tetra-phenyl-3,7-diaza-bicyclo-[3.3.1]nonan-9-one.

In the title compound, C(31)H(27)N(3)O(2), the two piperidine rings fused to each other each adopt a slightly distorted chair conformation. The phenyl rings on the N-unsubstituted piperidine ring occupy an equatorial position, while those on the N-nitroso-substituted piperidine ring are in axial positions. The NO group is approximately coplanar with the piperidine ring with a maximum deviation of 0.048 (4) Å. The dihedral angles between the mean planes of the axially and equatorially oriented phenyl rings are 27.7 (1) and 31.9 (1)°, respectively. Mol-ecular packing is stabilized by weak inter-molecular C-H⋯O and C-H⋯π inter-actions.

Ethyl 3-methyl-2,6-diphenyl-piperidine-1-carboxyl-ate.

In the title compound, C(21)H(25)NO(2), the piperidine ring adopts a twisted boat conformation characterized by puckering parameters θ = 89.5 (1) and ϕ = 257.5 (2)°. The phenyl groups are located in equatorial and axial positions on the central piperidine ring, while the methyl group is in an equatorial position. The dihedral angle between the phenyl rings is 49.8 (1)°. An intra-molecular C-H⋯O inter-action occurs. The crystal structure features weak inter-molecular C-H⋯O inter-actions and a stabilizing inter-molecular C-H⋯π contact involving the axial phenyl ring.

4-({(E)-[2-(But-3-en-1-yl)-1-(prop-2-en-1-yl)-4-sulfanyl-1H-imidazol-5-yl]methyl-idene}amino)-3-phenyl-1H-1,2,4-triazole-5(4H)-thione.

In the title compound, C(19)H(20)N(6)S(2), the dihedral angle between the phenyl and triazole rings is 24.1 (2)° while the dihedral angles between the imidazole ring and the triazole and phenyl rings are 39.9 (2) and 55.3 (2)°, respectively. The crystal structure is stabilized by inter-molecular N-H⋯N hydrogen bonds which form chains along [10[Formula: see text]].