Reactions of copper(I) aryloxides with phenyl isothiocyanate: steric and ligand control in the oligomerization of [N-phenylimino(aryloxy)methanethiolato]copper(I) complexes

The preparation of five different copper(I) complexes [CuSC(=NPh)(OAr)}L(n)]m (1-5) formed by the insertion of PhNCS into the Cu-OAr bond and the crystal structure analyses of three of them have been carried out. A monomeric species 1 (OAr = 2,6-dimethylphenoxide) is formed in the presence of excess PPh3 (n = 2, m = 1) and crystallizes as triclinic crystals with a = 12.419(4) angstrom, b = 13.298(7) angstrom, c = 15.936(3) angstrom, alpha = 67.09(3)-degrees, beta = 81.63(2)-degrees, gamma = 66.54(3)-degrees, V = 2224(2) angstrom3, and Z = 2. The structure was refined by the least-squares method to final R and R(w) values of 0.038 and 0.044, respectively, for 7186 unique reflections. Copper(I) 2,5-di-tert-butyl-4-methylphenoxide results in the formation of a dimeric species 2 in the presence of P(OMe)3 (n = 1, m = 2), where the coordination around Cu is trigonal. Crystals of 2 were found to be orthorhombic with a = 15.691(2) angstrom, b = 18.216(3) angstrom, c = 39.198(5) angstrom, v = 11204(3) angstrom3, and Z = 8. Least-squares refinement gave final residuals of R = 0.05 and R(w) = 0.057 with 6866 unique reflections. A tetrameric species 3 results when PPh3 is replaced by P(OMe)3 in the coordination sphere of copper(I) 2,6-dimethylphenoxide. It crystallizes in the space group P1BAR with a = 11.681 (1) angstrom, b = 13.373(2) angstrom, c = 20.127(1) angstrom, a = 88.55(l)-degrees, beta = 89.65(l)-degrees, gamma = 69.28(1)-degrees, V = 2940(l) angstrom3, and Z = 2. Least-squares refinement of the structure gave final values of 0.043 and 0.05 for R and R(w) respectively using 12214 unique reflections. In addition, a dimeric species 4 is formed when 1 equiv of PPh3 is added to the copper(I) 4-methylphenoxide, while with an excess of PPh3 a monomeric species 5 is isolated. Some interconversions among these complexes are also reported.

Cobalt(II) complexes of terpyridine bases as photochemotherapeutic agents showing cellular uptake and photocytotoxicity in visible light

Cobalt(II) complexes of terpyridine bases Co(L)(2)](ClO4)(2) (1-3), where L is 4'-phenyl-2,2':6',2''-terpyridine (ph-tpy in 1), 4'-(9-anthracenyl)-2,2':6',2''-terpyridine (an-tpy in 2) and 4'-(1-pyrenyl)-2,2':6',2''-terpyridine (py-tpy in 3), are prepared and their photo-induced DNA and protein cleavage activity and photocytotoxic property in HeLa cells studied. The 1 : 2 electrolytic and three-electron paramagnetic complexes show a visible band near 550 nm in DMF-Tris-HCl buffer. The complexes 1-3 show emission spectral bands at 355, 421 and 454 nm, respectively, when excited at 287, 368 and 335 nm. The quantum yield values for 1-3 in DMF-H2O (2 : 1 v/v) are 0.025, 0.060 and 0.28, respectively. The complexes are redox active in DMF-0.1 M TBAP. The Co(III)-Co(II) and Co(II)-Co(I) couples appear as quasi-reversible cyclic voltammetric responses near 0.2 and -0.7 V vs. SCE, respectively. Complexes 2 and 3 are avid binders to calf thymus DNA giving K-b value of similar to 10(6) M-1. The complexes show chemical nuclease activity. Complexes 2 and 3 exhibit oxidative cleavage of pUC19 DNA in UV-A and visible light. The DNA photocleavage reaction of 3 at 365 nm shows formation of singlet oxygen and hydroxyl radical species, while only hydroxyl radical formation is evidenced in visible light. Complexes 2 and 3 show non-specific photo-induced bovine serum albumin protein cleavage activity at 365 nm. The an-tpy and py-tpy complexes exhibit significant photocytotoxicity in HeLa cervical cancer cells on exposure to visible light giving IC50 values of 24.2 and 7.6 mu M, respectively. Live cell imaging study shows accumulation of the complexes in the cytosol of HeLa cancer cells.

Syntheses, spectroscopy, structures, and conformations of .lambda.3-cyclotriphosphazanes: role of negative hyperconjugation

The reactions of As-chlorocyclotriphosphazane [EtNPCl], with phenols or trifluoroethanol yield the respective aryloxy- or trifluoroethoxy-containingX 3-cyclotriphosphazanes [EtNP(OR)]3 (R = C6H4Br-4 (2),C 6H5 (3C,6 H3-Mez-3,5 (4), C6H3Mez-2,6 (5), CH2CF3 (6)) as their cis-transisomericmixtures. The products have beencharacterized by IRand NMRspectroscopy. Thecrystalstructuresofboth thecis (2a) and trans(2b) isomer_softhep-bromophenoxy derivative have been determined by X-ray diffraction. Crystal data for 2a: triclinic, P1, a = 9.872(4) A, b = 13.438(6) A, c = 13.548(8) A, CY = 117.02(5)', 0 = 96.00(6)', y = 105.38(4)O, Z = 2, final R = 0.080. Crystal data for 2b: monoclinic, P21/n, a = 12.721(6) A, b = 13.468(7) A, c = 17.882(5) A, /3 = 101.62(3)O, Z = 4, final R = 0.066. The cis isomer exhibits a chair-triaxial conformation and the trans isomer a boat-triaxial conformation. Conformational preferences of X3-cyclotriphosphazanes have been probed by both MNDO and ab initio calculations on model systems [HNPXIp (X = H, F). In addition to vicinal lone pair repulsions, negative hyperconjugative interactions involving the nitrogen lone pairs and adjacent P-X Q* orbitals are found to be important (especially when X is an electronegative substituent) in determining the conformational preferences of X3-cyclotriphosphazanes. The calculations also show that the axial - equatorial conversion at phosphorus has a large activation barrier in these systems

The variants of the protein toxins abrin and ricin A useful guide to understanding the processing events in the toxin transport

Kinetic data on inhibition of protein synthesis in thymocyte by three abrins and ricin have been obtained. The intrinsic efficiencies of A chains of four toxins to inactivate ribosomes, as analyzed by k1-versus-concentration plots were abrin II, III > ricin > abrin I. The lag times were 90, 66, 75 and 105 min at a 0.0744 nM concentration of each of abrin I, II, III and ricin, respectively. To account for the observed differences in the dose-dependent lag time, functional and structural variables of toxins such as binding efficiency of B chains to receptors and low-pH-induced structural alterations have been analyzed. The association constants obtained by stopped flow studies showed that abrin-I (4.13 × 105 M−1 s−1) association with putative receptor (4-methylumbelliferyl-α-D-galactoside) is nearly two times more often than abrin III (2.6 × 105 M−1 s−1) at 20°C. Equillibrium binding constants of abrin I and II to thymocyte at 37°C were 2.26 × 107 M−1 and 2.8 × 107 M−1 respectively. pH-induced structural alterations as studied by a parallel enhancement in 8-anilino-L-naphthalene sulfonate fluorescence revealed a high degree of qualitative similarity. These results taken with a nearly identical concentration-independent lag time (minimum lag of 41–42 min) indicated that the binding efficiencies and internalization efficiencies of these toxins are the same and that the observed difference in the dose-dependent lag time is causally related to the proposed processing event. The rates of reduction of inter-subunit disulfide bond, an obligatory step in the intoxication process, have been measured and compared under a variety of conditions. Intersubunit disulfide reduction of abrin I is fourfold faster than that of abrin II at pH 7.2. The rate of disulfide reduction in abrin I could be decreased 1 I-fold by adding lactose, compared to that without lactose. The observed differences in the efficiencies of A chains, the dose-dependent lag period, the modulating effect of lactose on the rates of disulfide reduction and similarity in binding properties make the variants a valuable tool to probe the processing events in toxin transport in detail.

Terpyridine Oxovanadium(IV) Complexes of Phenanthroline Bases for Cellular Imaging and Photocytotoxicity in HeLa Cells

Oxovanadium(IV) complexes VO(N-N-N)(N-N)](NO3)(2) (1-4) of (4'-phenyl)-2,2': 6',2 `'-terpyridine (ph-tpy in 1 and 2) or (4'-pyrenyl)-2,2':6',2 `'-terpyridine (py-tpy in 3 and 4) having N-N as 1,10-phenanthroline (phen in 1 and 3) or dipyrido3,2-a:2',3'-c]phenazine (dppz in 2 and 4) are prepared and characterized. The crystal structure of 1 has VO2+ group in VN5O coordination geometry. The terpyridine ligand coordinates in a meridional binding mode. The phen ligand displays a chelating mode of binding with an N-donor site trans to the vanadyl oxo group. The complexes show a d-d band in the range of 710-770 nm in aqueous DMF (4:1 v/v). The complexes exhibit an irreversible V-IV/V-III redox response near -1.0 V vs. SCE in aqueous DMF/0.1 M KCl. The complexes bind to CT DNA giving K-b values within 3.5 x 10(5) to 1.2 x 10(6) M-1. The complexes show poor chemical nuclease activity in dark. Complexes 2-4 show photonuclease activity in UV-A light of 365 nm forming O-1(2) and (OH)-O-center dot. Complex 4 shows DNA photocleavage activity at near-IR light of 785 nm forming (OH)-O-center dot radicals. Complexes 2 and 4 show significant photocytotoxicity in HeLa cancer cells. Uptake of the complexes in HeLa cells, studied by fluorescence imaging, show predominantly cytosolic localization inside the cells.

Studies in crystal engineering: structure�reactivity correlations of substituted styrylcoumarins and related systems

The solid state photochemical behaviour of 7-hydroxy-4-styrylcoumarin 1 and several of its derivatives and analogues has been investigated. All the compounds with the exception of 7-methoxy-4-styrylcoumarin 2 are photolabile and yield anti-HT dimers. It has been observed that chloro substitution in the systems studied does not lead to the expected beta-packing mode. The photobehaviour of 1 and 2 has been correlated with their crystal structures. Reasons for alpha-packing have been examined. The systematics in the arrangement of the carbonyl group and phenyl group of the close neighbours in the crystals of 1, 2 and a few other cases are presented.

Hydrography and circulation in the western Bay of Bengal during the northeast monsoon

The Bay of Bengal, a semienclosed tropical basin that comes under the influence of monsoonal wind and freshwater influx, is distinguished by a strongly stratified surface layer and a seasonally reversing circulation. We discuss characteristics of these features in the western Bay during the northeast monsoon, when the East India Coastal Current (EICC) flows southward, using hydrographic data collected during December 1991. Vertical profiles show uniform temperature and salinity in a homogeneous surface layer, on average, 25 m deep but shallower northward and coastward. The halocline, immediately below, is approximately 50 m thick; salinity changes by approximately 3 parts per thousand. About two thirds of the profiles show temperature inversions in this layer. Salinity below the halocline hardly changes, and stratification is predominantly due to temperature variation, The halocline is noticeably better developed and the surface homogeneous layer is thinner in a low-salinity plume that hugs the coastline along the entire east coast of India, The plume is, on average, 50 km wide, with isohalines sloping down toward the coast. Most prominent in the geostrophic velocity field is the equatorward EICC. Its transport north of about 13 degrees N, computed with 1000 dbar as the level of reference, varies between 2.6 and 7.1 x 10(6) m(3) s(-1); just south of this latitude, a northwestward flow from offshore recurves and merges with the coastal current. At the southern end of the region surveyed, the transport is 7.7 x 10(6) m(3) s(-1). Recent model studies lead us to conclude that the EICC during the northeast monsoon is driven by winds along the east coast of India and Ekman pumping in the interior bay. In the south, Ekman pumping over the southwestern bay is responsible for the northwestward flow that merges with the EICC.

Synthesis, characterisation and superoxide dismutase activity of a manganese(II) complex

A potent superoxide dismutase mimic; Mn-II(HL)(2) [H(2)L = 2,6-bis(benzimidazol-2-yl)pyridine] has been synthesised and characterised by its crystal structure determination and EPR spectroscopy.

Synthesis of DEF ring skeleton of naulafine alkaloid

6, 8-Dichloro-4, 5-dihydro-2-methyl-[2, 7]acenaphthyridin-1-one (5), obtained from the. reaction of 5-cyano-2, 6-dihydroxy-3, 4-cyclopentenopyridine with Vilsmeier reagent, has been transformed to the key synthon 4a in two steps.

Systematic crystallographic investigation of hydrogen-bonded networks involving monohydrogen tartrate-amine complexes: Potential materials for nonlinear optics

Crystal structures of six binary salts involving aromatic amines as cations and hydrogen tartrates as anions are presented. The materials are 2,6-xylidinium-L-monohydrogen tartrate monohydrate, C12H18O6.5N, P22(1)2(1), a = 7.283(2) Angstrom, b = 17.030(2) Angstrom, c = 22.196(2) Angstrom, Z = 8; 2,6-xylidinium-D-dibenzoyl monohydrogen tartrate, C26H25O8N, P2(1), a = 7.906(1) Angstrom, b = 24.757(1) Angstrom, c = 13.166(1) Angstrom, beta = 105.01(1)degrees, Z = 4; 2,3-xylidinium-D-dibenzoyl monohydrogen tartrate monohydrate, C26H26O8.5N, P2(1), a = 7.837(1) Angstrom, b = 24.488(1) Angstrom, c = 13.763(1) Angstrom, beta = 105.69(1)degrees, Z = 4; 2-toluidinium-D-dibenzoyl monohydrogen tartrate, C25H23O8N, P2(1)2(1)2(1), a = 13.553(2) Angstrom, b = 15.869(3) Angstrom, c = 22.123(2) Angstrom, Z = 8; 3-toluidinium-D-dibenzoyl monohydrogen tartrate (1:1), C25H23O8N, P1, a = 7.916(3) Angstrom, b = 11.467(6) Angstrom, c = 14.203(8) Angstrom, alpha = 96.44(4)degrees, beta = 98.20(5)degrees, = 110.55(5)degrees, Z = 2; 3-toluidinium-D-dibenzoyl tartrate dihydrate (1:2), C32H36O10N, P1, a = 7.828(3) Angstrom, b = 8.233(1) Angstrom, c = 24.888(8) Angstrom, alpha = 93.98 degrees, beta = 94.58(3)degrees, = 89.99(2)degrees, Z = 2. An analysis of the hydrogen-bonding schemes in terms of crystal packing, stoichiometric variations, and substitutional variations in these materials provides insights to design hydrogen-bonded networks directed toward the engineering of crystalline nonlinear optical materials.

The reaction of lambda 3-cyclotriphosphazanes with tetrachloro-ortho-benzoquinone: An unusual ring contraction-rearrangement

Oxidative addition of tetrachloro-ortho-benzoquinone to lambda(3)-cyclotriphosphazanes, [EtNP(OR)](3) results in an unprecedented ring contraction-rearrangement to give diazadiphosphetidines (EtN)(2)[P(OR)(O2C6Cl4)] [P(O2C6Cl4)-[N(Et)P(OR)(2)}] (R = C6H4Br-4 or C(6)H(3)Me(2)-2,6), a process indicated to be thermodynamically favourable on the basis of PM3 calculations.

The effect of malathion, an organophosphate, on the plasma FSH, 17 beta-estradiol and progesterone concentrations and acetylcholinesterase activity and conception in dairy cattle

The effect of malathion on jugular plasma concentrations of follicle-stimulating hormone (FSH), estradiol (E2), progesterone (P4) and acetylcholinesterase (AchE) on conception in dairy cattle during a cloprostenol (prostaglandin F2-alpha analogue, PG)-induced estrus was studied. Malathion (1 mg/kg, intraruminally) given at the onset of estrus (48 h after PG) did not alter the plasma FSH or E2 concentrations but significantly (P < 0.05) inhibited plasma P4 concentration. The mean P4 concentration in the malathion-treated group on days 8 and 12 were 0.8 +/- 0.4 and 1.0 +/- 0.5 ng/ml, as compared to 2.6 +/- 0.0 and 2.4 +/- 0.3 ng/ml in the control group. There was a nonsignificant (P > 0.05) inhibition of plasma AchE activity in malathion-treated cattle. Conception was 16.6% in malathion-treated cows and 50% in controls. Inhibition of progesterone secretion and poor conception occurred after the single intraruminal dose of malathion at the onset of estrus.

Unusual photobehaviour of crystalline 7-methoxy-4-methylcoumarin

7-Methoxy-4-methylcoumarin undergoes a solid-state photo [2 + 2] cycloaddition upon UV irradiation to yield two photodimers. The formation of the minor product appears to be a direct consequence of the formation of the topochemically controlled dimer.

Influence of metalaxyl on Glomus fasciculatum associated with wheat (Triticum aestivum L)

Soil incorporation of metalaxyl [methyl N-(2-methoxyacetyl)-N-(2,6,xylyl)-DL-alaninate] significantly enhanced root colonization of the vesicular-arbuscular (VA) mycorrhizal fungi Glomus fasciculatum associated with wheat. The stimulatory response of VA mycorrhizal fungi to low concentration of metalaxyl resulted in increased plant biomass production, nutrient uptake and grain yield of wheat. However, higher concentrations of metalaxyl, particularly 2.5 ppm of metalaxyl affected the mycorrhizal infection and seed yield of wheat, Addition of urban compost to an extent ameliorated the toxic effect of fungicide on VA mycorrhizal colonization, plant growth and yield of wheat when compared to unamended soil.

In vitro plant regeneration from different seedling explants of blackgram [Vigna mungo (L.) Hepper] via organogenesis

Callus induction and morphogenesis from different blackgram explants were tested on MS basal medium supplemented with B5 vitamins, IAA, NAA, IBA, KIN and BAP individually and in combinations. The explants were hypocotyl, epicotyl, axillary bud, cotyledonary node and immature leaf. The optimal levels of the frequency of callus induction was 22.8 mu M of IAA or 16.1 mu M NAA and in combination with 2.2 mu M of BAP. Among the seedling explants, hypocotyl was found to be more efficient in producing callus. Shoots mere induced from callus cultures of hypocotyls, epicotyls, axillary bud, cotyledonary node and immature leaf with varying frequencies in the medium containing KIN (2.3-9.3 mu M) or BAP (2.2-8.8 mu M) and in combination with IAA (2.8 mu M) or NAA (2.6 mu M). Multiple shoots were obtained using cotyledonary node segments. The regenerated shoots rooted best on MS basal medium containing 9.8 mu M IBA. Seventy three per cent of the shoots produced roots, and 80-85% of the plantlets survived under greenhouse condition.