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N Interactions (n + interaction)
Selected AbstractsSeveral components of global change alter nitrifying and denitrifying activities in an annual grasslandFUNCTIONAL ECOLOGY, Issue 4 2006R. BARNARD Summary 1The effects of global change on below-ground processes of the nitrogen (N) cycle have repercussions for plant communities, productivity and trace gas effluxes. However, the interacting effects of different components of global change on nitrification or denitrification have rarely been studied in situ. 2We measured responses of nitrifying enzyme activity (NEA) and denitrifying enzyme activity (DEA) to over 4 years of exposure to several components of global change and their interaction (increased atmospheric CO2 concentration, temperature, precipitation and N addition) at peak biomass period in an annual grassland ecosystem. In order to provide insight into the mechanisms controlling the response of NEA and DEA to global change, we examined the relationships between these activities and soil moisture, microbial biomass C and N, and soil extractable N. 3Across all treatment combinations, NEA was decreased by elevated CO2 and increased by N addition. While elevated CO2 had no effect on NEA when not combined with other treatments, it suppressed the positive effect of N addition on NEA in all the treatments that included N addition. We found a significant CO2,N interaction for DEA, with a positive effect of elevated CO2 on DEA only in the treatments that included N addition, suggesting that N limitation of denitrifiers may have occurred in our system. Soil water content, extractable N concentrations and their interaction explained 74% of the variation in DEA. 4Our results show that the potentially large and interacting effects of different components of global change should be considered in predicting below-ground N responses of Mediterranean grasslands to future climate changes. [source] Host-specific aphid population responses to elevated CO2 and increased N availabilityGLOBAL CHANGE BIOLOGY, Issue 11 2005Erika A. Sudderth Abstract Sap-feeding insects such as aphids are the only insect herbivores that show positive responses to elevated CO2. Recent models predict that increased nitrogen will increase aphid population size under elevated CO2, but few experiments have tested this idea empirically. To determine whether soil nitrogen (N) availability modifies aphid responses to elevated CO2, we tested the performance of Macrosiphum euphorbiae feeding on two host plants; a C3 plant (Solanum dulcamara), and a C4 plant (Amaranthus viridis). We expected aphid population size to increase on plants in elevated CO2, with the degree of increase depending on the N availability. We found a significant CO2× N interaction for the response of population size for M. euphorbiae feeding on S. dulcamara: aphids feeding on plants grown in ambient CO2, low N conditions increased in response to either high N availability or elevated CO2. No population size responses were observed for aphids infesting A. viridis. Elevated CO2 increased plant biomass, specific leaf weight, and C : N ratios of the C3 plant, S. dulcamara but did not affect the C4 plant, A. viridis. Increased N fertilization significantly increased plant biomass, leaf area, and the weight : height ratio in both experiments. Elevated CO2 decreased leaf N in S. dulcamara and had no effect on A. viridis, while higher N availability increased leaf N in A. viridis and had no effect in S. dulcamara. Aphid infestation only affected the weight : height ratio of S. dulcamara. We only observed an increase in aphid population size in response to elevated CO2 or increased N availability for aphids feeding on S. dulcamara grown under low N conditions. There appears to be a maximum population growth rate that M. euphorbiae aphids can attain, and we suggest that this response is because of intrinsic limits on development time and fecundity. [source] Theoretical studies on the S,N interaction in sulfinamidesJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 4 2002Prasad V. Bharatam Abstract The potential energy surface of sulfinamide H(O)S,NH2 (1) was searched, using ab initio and density functional methods, to study the conformational preferences. High-accuracy G2MP2 calculations showed that the S,N rotational barrier in 1 is 7.0,kcal,mol,1. The inversion around N in 1 goes through a very low energy barrier. Charge analysis using the NPA method was performed to elucidate the electronic factors responsible for the observed trends in the S,N interactions. The strength of negative hyperconjugation in 1 was estimated using NBO analysis and by studying the substituent effect. The repulsions between the lone pairs on oxygen and nitrogen and the nN , ,*S,O negative hyperconjugation play an important role in the conformations. Copyright © 2002 John Wiley & Sons, Ltd. [source] Ethyl 2-amino-4- tert -butyl-1,3-thiazole-5-carboxylate and 6-methylimidazo[2,1- b]thiazole,2-amino-1,3-thiazole (1/1)ACTA CRYSTALLOGRAPHICA SECTION C, Issue 8 2004Daniel E. Lynch The structure of ethyl 2-amino-4- tert -butyl-1,3-thiazole-5-carboxylate, C10H16N2O2S, (I), and the structure of the 1:1 adduct 6-methylimidazo[2,1- b]thiazole,2-amino-1,3-thiazole (1/1), C6H6N2S·C3H4N2S, (II), have been determined. The molecules in (I) associate via a hydrogen-bonded R(8) dimer consisting of N,H,N interactions, with the hydrogen-bonding array additionally involving N,H,O interactions to one of the carboxylate O atoms. The 2-aminothiazole molecules in (II) also associate via an N,H,N hydrogen-bonded R(8) dimer, with an additional N,H,N interaction to the Nsp2 atom of the imidazothiazole moiety, creating hydrogen-bonded quartets. [source] N,N,-Bis(2-pyridyl)benzene-1,2-diamineACTA CRYSTALLOGRAPHICA SECTION C, Issue 3 2004Maria Gdaniec Hindered rotation about the partial double C,N bonds between the amine and pyridine moieties in the title molecule, C16H14N4, results in two different conformations of the N -aryl-2-aminopyridine units. One, assuming an E conformation, is involved in a pair of N,H,N hydrogen bonds that generate a centrosymmetric (8) motif. The second, adopting a Z conformation, is not engaged in any hydrogen bonding and is flattened, the dihedral angle between the benzene and pyridine rings being 12.07,(7)°. This conformation is stabilized by an intramolecular C,H,N interaction [C,N,= 2.9126,(19),Å, H,N,=,2.31,Å and C,H,N,=,120°]. [source] Syntheses and Crystal Structure of Six-coordinated Diorgnotin Complexes with 2, 5-Dimercapto-4-phenyl-1, 3,4-thiodiazoIe,CHINESE JOURNAL OF CHEMISTRY, Issue 7 2003Chun-Lin Ma Abstract The reactions of diorganotin dichloride [Ph2SnCl2, (PhCH2)2 -SnCl2 or (n -Bu)2SnCl2] with potassium salt of 2, 5-dimercapto-4-phenyl-1, 3, 4-thiodiazole gave complexes R2Sn (S3N2C8H5)2 (4: R = Ph; 5: R = PhCH2 and 6: R = n -Bu), respectively. Characterizations were carried out for all complexes by IR, 1H NMR spectra and X-ray crystallography analysis. Including the Sn,N interaction, the three complexes all have six-coordinated distorted octahedral geometry. Based on the requence of stereochemical constraint sequence, phenyl,benzyl > n -butyl, the less the effect of the stereochemical constraint of R groups, the shorter the Sn,N length. In complexes 5 and 6, there exist S,S weak intra-molecular interactions, through which the complexes are dissociated into loose 2D polymers. All three complexes show antitumour activity in bioactivity measurements. [source] Theoretical studies on the S,N interaction in sulfinamidesJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 4 2002Prasad V. Bharatam Abstract The potential energy surface of sulfinamide H(O)S,NH2 (1) was searched, using ab initio and density functional methods, to study the conformational preferences. High-accuracy G2MP2 calculations showed that the S,N rotational barrier in 1 is 7.0,kcal,mol,1. The inversion around N in 1 goes through a very low energy barrier. Charge analysis using the NPA method was performed to elucidate the electronic factors responsible for the observed trends in the S,N interactions. The strength of negative hyperconjugation in 1 was estimated using NBO analysis and by studying the substituent effect. The repulsions between the lone pairs on oxygen and nitrogen and the nN , ,*S,O negative hyperconjugation play an important role in the conformations. Copyright © 2002 John Wiley & Sons, Ltd. [source] Mitochondrial respiratory pathways modulate nitrate sensing and nitrogen-dependent regulation of plant architecture in Nicotiana sylvestrisTHE PLANT JOURNAL, Issue 6 2008Till K. Pellny Summary Mitochondrial electron transport pathways exert effects on carbon,nitrogen (C/N) relationships. To examine whether mitochondria,N interactions also influence plant growth and development, we explored the responses of roots and shoots to external N supply in wild-type (WT) Nicotiana sylvestris and the cytoplasmic male sterile II (CMSII) mutant, which has a N-rich phenotype. Root architecture in N. sylvestris seedlings showed classic responses to nitrate and sucrose availability. In contrast, CMSII showed an altered ,nitrate-sensing' phenotype with decreased sensitivity to C and N metabolites. The WT growth phenotype was restored in CMSII seedling roots by high nitrate plus sugars and in shoots by gibberellic acid (GA). Genome-wide cDNA-amplified fragment length polymorphism (AFLP) analysis of leaves from mature plants revealed that only a small subset of transcripts was altered in CMSII. Tissue abscisic acid content was similar in CMSII and WT roots and shoots, and growth responses to zeatin were comparable. However, the abundance of key transcripts associated with GA synthesis was modified both by the availability of N and by the CMSII mutation. The CMSII mutant maintained a much higher shoot/root ratio at low N than WT, whereas no difference was observed at high N. Shoot/root ratios were strikingly correlated with root amines/nitrate ratios, values of <1 being characteristic of high N status. We propose a model in which the amine/nitrate ratio interacts with GA signalling and respiratory pathways to regulate the partitioning of biomass between shoots and roots. [source] Ethyl 2-amino-4- tert -butyl-1,3-thiazole-5-carboxylate and 6-methylimidazo[2,1- b]thiazole,2-amino-1,3-thiazole (1/1)ACTA CRYSTALLOGRAPHICA SECTION C, Issue 8 2004Daniel E. Lynch The structure of ethyl 2-amino-4- tert -butyl-1,3-thiazole-5-carboxylate, C10H16N2O2S, (I), and the structure of the 1:1 adduct 6-methylimidazo[2,1- b]thiazole,2-amino-1,3-thiazole (1/1), C6H6N2S·C3H4N2S, (II), have been determined. The molecules in (I) associate via a hydrogen-bonded R(8) dimer consisting of N,H,N interactions, with the hydrogen-bonding array additionally involving N,H,O interactions to one of the carboxylate O atoms. The 2-aminothiazole molecules in (II) also associate via an N,H,N hydrogen-bonded R(8) dimer, with an additional N,H,N interaction to the Nsp2 atom of the imidazothiazole moiety, creating hydrogen-bonded quartets. [source] Tris(2-pyridyl)phosphine oxide: how C,H,O and C,H,N interactions can affect crystal packing efficiencyACTA CRYSTALLOGRAPHICA SECTION C, Issue 4 2004Richard J. Bowen Tris(2-pyridyl)phosphine oxide, (I), C15H12N3OP, is isomorphous with tris(2-pyridyl)phosphine. Because of a combination of C,H,O and C,H,N interactions, the crystal packing is denser in the title compound than in the related compounds triphenylphosphine oxide and tris(2-pyridyl)phosphine. [source] catena -Poly[[bis[,-1,2-bis(1-methyltetrazol-5-yl)ethane-,2N4:N4,]bis[chlorocopper(II)]]-di-,-chloro]ACTA CRYSTALLOGRAPHICA SECTION C, Issue 6 2003Dmitry O. Ivashkevich In the title compound, [Cu2Cl4(C6H10N8)2]n, the ligand has C2 symmetry, and the Cu and Cl atoms lie on a mirror plane. The coordination polyhedron of the Cu atom is a distorted square pyramid, with the basal positions occupied by two N atoms from two different ligands [Cu,N,=,2.0407,(18),Å] and by the two Cl atoms [Cu,Cl,=,2.2705,(8) and 2.2499,(9),Å], and the apical position occupied by a Cl atom [Cu,Cl,=,2.8154,(9),Å] that belongs to the basal plane of a neighbouring Cu atom. The [CuCl2(C6H10N8)]2 units form infinite chains extending along the a axis via the Cl atoms. Intermolecular C,H,Cl contacts [C,Cl,=,3.484,(2),Å] are also present in the chains. The chains are linked together by intermolecular C,H,N interactions [C,N,=,3.314,(3),Å]. [source] Trimethyl[3-methyl-1-(o -tolenesulfonyl)indol-2-ylmethyl]ammonium iodide and benzyl[3-bromo-1-(phenylsulfonyl)indol-2-ylmethyl]tolylamineACTA CRYSTALLOGRAPHICA SECTION C, Issue 12 2002P. R. Seshadri The title compounds, C20H25N2O2S+·I,, (I), and C29H25BrN2O2S, (II), respectively, both crystallize in space group P. The pyrrole ring subtends an angle with the sulfonyl group of 33.6° in (I) and 21.5° in (II). The phenyl ring of the sulfonyl substituent makes a dihedral angle with the best plane of the indole moiety of 81.6° in (I) and 67.2° in (II). The lengthening or shortening of the C,N bond distances in both compounds is due to the electron-withdrawing character of the phenylsulfonyl group. The S atoms are in distorted tetrahedral configurations. The molecular structures are stabilized by C,H,O and C,H,I interactions in (I), and by C,H,O and C,H,N interactions in (II). [source] 4-Anilino-3-nitropyridineACTA CRYSTALLOGRAPHICA SECTION C, Issue 11 2000Daniel E. Lynch The structure of the title compound, C22H18N6O4, (I), comprises two unique molecules that separately form hydrogen-bonded polymer chains via N,H,N interactions. Molecular independence arises due to a difference in the dihedral angles between the linked rings, i.e. 52.19,(4) and 46.17,(5)°. [source] (2,2,-Bipyridine-,2N)bis[N -(2-pyridyl-,N)- p -toluenesulfonamido-,N]zinc(II)ACTA CRYSTALLOGRAPHICA SECTION C, Issue 3 2000Santiago Cabaleiro The structure of the title compound, [Zn(C12H11N2O2S)2(C10H8N2)], consists of monomeric molecules in which the central ZnN2N,N,, unit has a distorted tetrahedral geometry, with bond lengths ranging from 2.020,(3) to 2.109,(3),Å. The anionic ligands are potential bidentate donors and thus there are two secondary Zn,N interactions. The shorter of these is 2.317,(3),Å and completes at the Zn atom an irregular five-coordinated geometry, which can be described as a square pyramid showing 30% distortion towards the trigonal bipyramid; the other Zn,N contact is much longer at 2.549,(3),Å. [source] | |||||||||||||