Fluorescence polarization as a tool to study lectin-sugar interaction. An investigation of the binding of 4-methylumbelliferyl beta-D-galactopyranoside to Abrus precatorious agglutinin

Polarization of ligand fluorescence was used to study the binding of 4-methylumbelliferyl beta-D-galactopyranoside (MeUmb-Galp) to Abrus precatorious agglutinin. The binding of the fluorescent sugar to the lectin led to considerable polarization of the MeUmb-Galp fluorescence, which was also quenched by about 30% on binding to the lectin. The binding of the fluorescent sugar was carbohydrate-specific, as evidenced by inhibition of both fluorescence polarization and quenching when lectin was preincubated with lactose. The association constant as determined by fluorescence polarization is 1.42 x 10(4) M-1 at 25 degrees C and is in excellent agreement with those determined by fluorescence quenching (Ka = 1.51 x 10(4) M-1) and equilibrium dialysis (Ka = 1.62 x 10(4) M-1) at 25 degrees C. The numbers of binding sites as determined by fluorescence polarization, quenching and equilibrium dialysis agree very well with one another, n being equal to 2.0 +/- 0.05. The consistency between the association constant value determined by fluorescence polarization, quenching and equilibrium dialysis shows the validity of this approach to study lectin-sugar interaction.

1-(4-Chlorophenyl)-2-[(3-phenylisoquinolin 1-yl)sulfanyl]ethanone

The title compound, C23H16ClNOS, exhibits dihedral angles of 11.73 (1) and 66.07 (1)degrees, respectively, between the mean plane of the isoquinoline system and the attached phenyl ring, and between the isoquinoline system and the chlorophenyl ring. The dihedral angle between the phenyl and chlorophenyl rings is 54.66 (1)degrees.

A new open-framework zinc arsenate [C4N3H16](2)[Zn-5(AsO4)(4)(HAsO4)(2)]

A three-dimensional zinc arsenate with an interrupted zeolitic framework (-IIO), [C4N3H16](2)[Zn-5(AsO4)(4)(HAsO4)(2)], I has been synthesized solvothermally. The structure is built up from ZnO4, AsO4 and HAsO4 tetrahedral units connected alternatively through their vertices forming the 3-D structure possessing one-dimensional channels bound by 10 T-atoms (T = Zn, As), The framework density of the structure is 10.4 T-atoms which indicates considerable openness in its structure. (C) 2009 Elsevier B.V. All rights reserved.

Ethyl 2-acetyl-3-(4-bromoanilino)butanoate

The title compound, C14H18BrNO3, adopts an extended conformation, with all of the main-chain torsion angles associated with the ester and amino groups close to trans. In the crystal, inversion dimers linked by pairs of N-H center dot center dot center dot O hydrogen bonds are observed.

Diethyl 4-(2,4-dichlorophenyl)-2,6-dimethyl 1,4-dihydropyridine-3,5-dicarboxylate

In the title compound, C19H21Cl2NO4, the dihydropyridine ring adopts a flattened boat conformation. The dichlorophenyl ring is oriented almost perpendicular to the planar part of the dihydropyridine ring [dihedral angle = 89.1 (1)degrees]. An intramolecular C-H center dot center dot center dot O hydrogen bond is observed. In the crystal structure, molecules are linked into chains along the b axis by N-H center dot center dot center dot O hydrogen bonds.

5-Phenyl-3-(2-thienyl)-1,2,4-triazolo[3,4-a]isoquinoline

In the title molecule, C20H13N3S, the triazoloisoquinoline ring system is approximately planar, with an r.m.s. deviation of 0.045 angstrom and a maximum deviation of 0.090 (2) angstrom from the mean plane for the triazole ring C atom which is bonded to the thiophene ring. The phenyl ring is twisted by 52.0 (1)degrees with respect to the mean plane of the triazoloisoquinoline ring system. The thiophene ring is rotationally disordered by approximately 180 degrees over two sites, the ratio of refined occupancies being 0.73 (1): 0.27 (1).

2-(4-Chloro-3-nitrophenyl)-4-(4-chlorophenyl)-1,3-thiazole

The title compound, C15H8Cl2N2O2S, crystallizes with two molecules in the asymmetric unit. The dihedral angles between the 4-chloro-3-nitrophenyl ring and the thiazole ring are 0.5 (1) and 7.1 (1)° and those between the 4-chlorophenyl ring and the thiazole ring are 7.1 (1) and 7.4 (1)° in the two molecules. The crystal structure is stabilized by intermolecular C-H...Cl and C-H...O hydrogen bonds.

2-[(E)-(4-hydroxy-3-methoxybenzylidene)amino]-N-(2-methylphenyl)-4,5,6,7-tetrahydro-1-benzothiophene-3-carboxamide

The title compound, C24H24N2O3S, exhibits antifungal and antibacterial properties. The compound crystallizes with two molecules in the asymmetric unit, with one molecule exhibiting 'orientational disorder' in the crystal structure with respect to the cyclohexene ring. The o-toluidine groups in both molecules are noncoplanar with the respective cyclohexene-fused thiophene ring. In both molecules, there is an intramolecular N-H...N hydrogen bond forming a pseudo-six-membered ring which locks the molecular conformation and eliminates conformational flexibility. The crystal structure is stabilized by O-H...O hydrogen bonds; both molecules in the asymmetric unit form independent chains, each such chain consisting of alternating 'ordered' and 'disordered' molecules in the crystal lattice.

2,6-Bis(3-methoxyphenyl)-3-methylpiperidin-4-one

In the molecule of the title compound, C20H23NO3, the bulky methoxyphenyl substituents at the equatorial 2,6-positions crowd the vicinity of the equatorial amino H atom and prevent it from forming intermolecular hydrogen bonds. The piperidine ring adopts a distorted chair conformation.

6,8-Dibromo-5-hydroxy-4-oxo-2-phenyl-4H-chromen-7-yl acetate

In the title compound, C17H10Br2O5, the chromene ring is almost planar with minimal puckering [total puckering amplitude = 0.067 (4) angstrom]. The dihedral angle between chromeme ring system and phenyl ring is 3.7 (2)degrees. The crystal structure is stabilized by intermolecular C-H center dot center dot center dot O interactions and an intramolecular O-H center dot center dot center dot O hydrogen bond also occurs.

Unusual Anisotropic Effects from 1,3-Dipolar Cycloadducts of 4-Azidomethyl Coumarins

4-Bromomethylcoumarins (1) reacted with sodium azide in aqueous acetone to give 4-azidomethyl-coumarins (2), which underwent 1,3-dipolar cycloaddition with acetylenic dipolarophiles to give triazoles (3). These triazoles (3) have been found to exhibit interesting variations in the chemical shifts of C-3-H and C-4-methylene protons. Protonation studies indicate that the shielding effect of the C-3-H of coumarin is due to pi-electrons of the triazole ring, further supported by diffraction and computational studies.

Crystal Structures of a New Polymorphic Form of Gabapentin Monohydrate and the E and Z Isomers of 4-Tertiarybutylgabapentin

Gabapentin, a widely used antiepileptic drug, crystallizes in multiple polymorphic forms. A new crystal form of gabapentin monohydrate in the space group Pbca is reported and the packing arrangement compared with that of a previously reported polymorph in the space group P2(1)/c [Ibers, J.A. (2001) Acta Crystallogr; C57:641]. Gabapentin polymorphs can also occur from a selection of one of the two distinct chair forms of the 1,1-disubstituted cyclohexane. Crystal structures of the E and Z isomers of 4-tert-butylgabapentin provide models for analyzing anticipated packing modes in the conformational isomers of gabapentin. The E isomer crystallized in the space group Pca2(1), while the Z isomer crystallized in the space group P2(1)/c. The crystal structure of E-4-tert-butylgabapentin provides the only example of a structure in a non-centrosymmetric space group. Crystal structures of the hydrochloride and hydrobromide salts of 4-tert-butyl derivatives are reported. The results suggest that for gabapentin, a large 'polymorph-space' may be anticipated, in view of the multiple conformational states that are accessible to the molecule.

Ethyl 6-chloro-2-methyl-4-phenylquinoline-3-carboxylate

In the title compound, C19H16ClNO2, the quinoline ring system is planar (r.m.s. deviation = 0.008 angstrom). The phenyl group and the -CO2 fragment of the ester unit form dihedral angles of 60.0 (1) and 60.5 (1)degrees, respectively, with the quinoline ring system.

Comparison of performance parameters of poly(3,4 ethylenedioxythiophene) (PEDOT) based electrochromic device on glass with and without counter electrode

Conjugated polymers are promising materials for electrochromic device technology. Aqueous dispersions of poly(3,4-ethylenedioxythiophene)-(PEDOT) were spin coated onto transparent conducting oxide (TCO) coated glass substrates. A seven-layer electrochromic device was fabricated with the following configuration: glass/transparent conducting oxide (TCO)/PEDOT (main electrochromic layer)/gel electrolyte/prussian blue (counter electrode)/TCO/glass. The device fabricated with counter electrode (Prussian blue) showed a contrast of 18% and without counter electrode showed visible contrast of 5% at 632 nm at a voltage of 1.9 V. The comparison of the device is done in terms of the colouration efficiency of the devices with and without counter electrode.

Dielectric anisotropy and relaxation studies of the homologous series of N-(4-n-alkyloxy-2-hydroxy-benzylidene)-4-carbethoxyaniline

Dielectric properties of the homologous series of newly synthesized nonchiral compounds N-(4-n-alkyloxy-2-hydroxy-benzylidene)-4-carbethoxyaniline, (n = 6, 8, 10, 12) having wide temperature range (∼60°C) smectic A (SmA) phase, have been studied by the impedance spectroscopy in the frequency range of 100 Hz to 1 MHz. Measurements have been carried out for two principal alignments (planar as well as homeotropic) of the SmA phase. Dielectric anisotropy (Δε' = ε'∥ - ε'⊥) for all the members of the series has been found to be negative for the whole temperature range of SmA phase. Magnitude of the dielectric anisotropy (|Δε'|) has been found to decrease with the number of alkyl chains. Relaxation frequencies corresponding to the rotation of the individual molecules about their short axes, lie below 1 MHz and obey the Arrhenius law by which activation energies have been determined. However, the relaxation frequencies corresponding to the rotation of the molecules about their short axes apparently lie above 10 MHz.