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Tridentate Schiff base complexes of zinc and calcium were prepared and tested in the ring-opening polymerization of ζ-caprolactone and rac-lactide to generate biodegradable polymeric materials from biocompatible metals. Alteration of the pendant donor arm attached to the imine backbone provides some control over catalyst composition and polymerization activity. Complexes of the formula [ONN]ZnN[(Si[Me.sub.3]).sub.2], where [ONN] = 2-(N-donor arm-imine)[4,6-di(tert-butyl)phenoxide], were isolated with ethyldimethylamine, ethylpiperidine, and ethylmorpholine substituents, while disproportionation led to the isolation of [[ONN].sub.2]Zn complexes with methylpyridine, quinoline, and ethyldiisopropylamine derivatives, two of which were crystallographically characterized. Calcium complexes were more stable and novel [ONN]CaN[(Si[Me.sub.3]).sub.2] complexes with ethylpiperidine and ethyldiisopropylamine substituents were reported. Zinc and calcium catalysts coordinated to a single tridentate ligand were effective at initiating the polymerization of ζ-caprolactone, but did not control the polymerizations, whereas the bis(ligand) complexes produced no polymer. These catalysts were effective at controlling the polymerization of rac-lactide. Coordinatively saturated complexes inhibit the polymerization, while initiation from either the amido or ligand alkoxide functionalities produces poly(lactic acid) with low polydispersities. Key words: lactide, caprolactone, zinc, calcium, ring opening polymerization. On a prepare des complexes de zinc et de calcium avec des bases de Schiff tridentates et on a evalue la possibilite de les utiliser dans les polymerisations par ouverture de cycle de la ζ-caprolactone et du rac-lactide conduisant a des materiaux polymeres biodegradables a partir de produits metalliques biodegradables. L'alteration du bras donneur pendant attache au squelette de l'imine permet d'avoir un certain controle sur la composition du catalyseur et son activite dans la polymerisation. On a pu isoler des complexes de formule [ONN]ZnN[(Si[Me.sub.3]).sub.2] (dans lesquels [ONN] = 2-(imine avec bras N-donneur)[4,6-di(ieri-butyl)phenolate] portant des substituants ethyldimethylamine, ethylpiperidine et ethylmorpholine alors qu' une disproportionation permet d' isoler les complexes [[ONN].sub.2]Zn avec les derives de la methylpyridine, la quinoleine et l' ethyldiisopropylamine, dont deux ont ete caracterises par cristallographie. Les complexes du calcium sont plus stables et on a isole pour la premiere fois les nouveaux complexes [ONN]CaN[(Si[Me.sub.3]).sub.2] avec des substituants ethylpiperidine et ethyldiisopropylamine. Les catalyseurs du zinc et du calcium ne comportant qu'une coordination a un ligand tridentate sont efficaces pour initier la polymerisation de la ζ-caprolactone, mais ils ne permettent pas de controler les polymerisations alors que les complexes avec un bis(ligand) ne permettent pas de produire des polymeres. Ces catalyseurs sont efficaces pour controler la polymerisation du rac-lactide. Les complexes a coordination saturee inhibent la polymerisation alors qu' une initiation par des groupes fonctionnels amido-ou un ligand alcoolate conduisent a la production d'acide polylactique avec de faibles polydispersites. Mots-cles: lactide, caprolactone, zinc, calcium, polymerisation par ouverture de cycle. [Traduit par la Redaction], Aliphatic poly(esters) such as poly(lactic acid) (PLA) and poly(ζ-caprolactone) (PCL) have gained considerable interest in recent years because of their biodegradability and renewability. (1-4) These aliphatic polymers are also bioassimilable, [...]

From 1,11-bis(salicylaldimine)-3,6,9-trithiaundecane ([H.sub.2]LI), 1,11-bis(salicylaldimine)-6-oxa-3,9-dithiaundecane ([H.sub.2]L2), and 1,8-bis(salicylaldimine)-3,6-dithiaundecane ([H.sub.2]L3), syntheses for [[Cu(L1)].sub.2] (I), Cu(L2)*C[H.sub.3]OH (II), Cu(L3) (III), [Cu(HL3)][C[H.sub.3]COO] (IV), [Cu(HL1-sal)][Cl.sub.2] (V), [Cu.sub.4][(L1).sub.2][Br.sub.4][([H.sub.2][O.sub.2]).sub.2]*2[H.sub.2]O(VI) and [Cu.sub.2](L2)[Br.sub.2]*x[H.sub.2]O(VII) are described. Single crystal X-ray structural studies for I, III and VII are reported. Variable temperature magnetic susceptibility studies of I, VI and VII are discussed. The examination of VII represents the first magneto-structural study of a binuclear copper(II) species with NS[O.sub.3]Br coordination spheres. This study examines perturbation by one or more of the donor atoms so that none of the known magnetostructural models predicts the copper-copper coupling. Key words: binuclear copper(II) complexes, thioether, salicylaldimine ligands, variable temperature magnetic susceptibility, magnetostructural correlation, X-ray structure. Utilisant les 1,11-bis(salicylaldimine)-3,6,9-trithiaundecane ([H.sub.2]L1), 1,11-bis(salicylaldimine)-6-oxa-3,9- dithiaundecane ([H.sub.2]L2) et 1,8-bis(salicylaldimine)-3,6-dithiaundecane ([H.sub.2]L3), on a realise les syntheses des complexes [[Cu(L1)].sub.2] (I), Cu(L2>C[H.sub.3]OH (II), Cu(L3) (III), [Cu(HL3)][C[H.sub.3]COO] (IV), [Cu(HLI-sal)][Cl.sub.2] (V), [Cu.sub.4][(L1).sub.2]Brs[([H.sub.2][O.sub.2]).sub.2]*2[H.sub.2]O(VI)et [Cu.sub.2](L2)[Br.sub.2]*x[H.sub.2]O(VII). On a effectue la determination des structures des composes I, III et VII par diffraction des rayonsX sur un cristal unique. On discute des resultats d'etudes de susceptibilite magnetique des composes I, VI et VII, a temperature variable. L'examen du compose VII correspond a la premiere etude magneto-structurale d'une espece de cuivre(II) binucleaire comportant des spheres de coordination avec du NS[O.sub.3]Br. Cette etude permet d'examiner la perturbation par un ou plusieurs atomes donneurs; aucun des modeles magneto-structuraux ne predit le couplage cuivre-cuivre. Mots-cles : complexes de cuivre(II) binucleaire, thioether, ligands salicylaldimine, susceptibilite magnetique a temperature variable, correlation magneto-structurale, structure par diffraction des rayons X. [Traduit par la Redaction], Introduction Magnetostructural correlations involving multinuclear metal complexes remain of interest. (1-5) Although the nuclearity of complexes being reported continues to rise, (6,7) much that is of fundamental significance can be [...]

Plants activate distinct defense responses depending on the lifestyle of the attacker encountered. In these responses, salicylic acid (SA) and jasmonic acid (JA) play important signaling roles. SA induces defense against biotrophic pathogens that feed and reproduce on live host cells, whereas JA activates defense against necrotrophic pathogens that kill host cells for nutrition and reproduction. Cross-talk between these defense signaling pathways has been shown to optimize the response against a single attacker. However, its role in defense against multiple pathogens with distinct lifestyles is unknown. Here we show that infection with biotrophic Pseudomonas syringae, which induces SA-mediated defense, rendered plants more susceptible to the necrotrophic pathogen Alternaria brassicicola by suppression of the JA signaling pathway. This process was partly dependent on the cross-talk modulator NPR1. Surprisingly, this tradeoff was restricted to tissues adjacent to the site of initial infection; A. brassicicola infection in systemic tissue was not affected. Even more surprisingly, tradeoff occurred only with the virulent Pseudomonas strain. Avirulent strains that induced programmed cell death (PCD), an effective plant-resistance mechanism against biotrophs, did not cause suppression of JA-dependent defense. This result might be advantageous to the plant by preventing necrotrophic pathogen growth in tissues undergoing PCD. Our findings show that plants tightly control cross-talk between SA- and JA-dependent defenses in a previously unrecognized spatial and pathogen type-specific fashion. This process allows them to prevent unfavorable signal interactions and maximize their ability to concomitantly fend off multiple pathogens. biotroph | cross-talk | jasmonic acid | necrotroph | salicylic acid

AtPepl, a 23-aa peptide encoded by Arabidopsis PROPEP1, a member of a small, six-member gene family, activates expression of the defense gene PDF1.2 (encoding defensin) and its own precursor gene, PROPEP1, through the jasmonate/ethylene signaling pathway, mediated by a cell-surface receptor, PEPR1. Over-expression of two family members, PROPEP1 and PROPEP2, enhances resistance of Arabidopsis plants against the pathogen Pythium irregulare, and PROPEP2 and PROPEP3 are expressed at highly elevated levels in Arabidopsis in response to pathogen infections and to several pathogen-associated molecules (general elicitors). Here, we report that PDF1.2, PR-1 (pathogenesis protein), and PROPEP genes were differentially expressed in the leaves of intact plants sprayed with methyl jasmonate and methyl salicylate and in excised leaves supplied through cut petioles with peptides derived from the C terminus of each of the encoded proteins. The expression of PDF1.2 and PR-1 elicited by the peptides was blocked in mutant plants deficient in the jasmonate/ethylene and salicylate pathways, and in wild-type plants by treatment with diphenylene iodonium chloride, an inhibitor of hydrogen peroxide production. PROPEP1, PROPEP2, and PROPEP3 genes appear to have roles in a feedback loop that amplifies defense signaling pathways initiated by pathogens. defensin | jasmonate | plant defense | PR-1 | salicylic acid

Salicylic acid (SAL) may impact Staphylococcus aureus virulence by activating the sigB operon (rsbU-V-W-sigB), thus leading to reductions in alpha-toxin production and decreased fibronectin binding (L. I. Kupferwasser et al., J. Clin. Investig. 112:222-233, 2003). As these prior studies were performed in strain RN6390 (an rsbU mutant) and its rsbU-repaired variant, SH1000, the current investigation was designed to determine if the SAL effect occurs via rsbU- and/or rsbV-dependent pathways in an rsbU-intact S. aureus strain (FDA486). We thus quantified the transcription from two sigB-dependent promoters (asp23 and sara P3) in FDA486 in response to SAL exposure in vitro, using isogenic single-knockout constructs of rsbU, rsbV, or rsbW and a green fluorescent protein reporter system. SAL induced sarA P3 and asp23 promoter activities in a dose-dependent manner in the parental strain. In contrast, sigB activation by SAL was progressively more mitigated in the rsbU and rsbV mutants. As predicted, SAL caused significant reductions in both alpha-toxin production and fibrinogen and fibronectin binding in the parental strain. The extent of these reductions, compared with the parent, was reduced in the rsb mutants (rsbV > rsbU), especially at low SAL concentrations. Since generation of the free SigB protein usually requires a sequential rsbU-V-W-sigB activation cascade, the present phenotypic and genotypic data suggest key roles for both rsbU and rsbV in SAL-mediated activation of sigB in strains with a fully intact sigB operon.

Salicylic acid (SA) is a critical signal for the activation of plant defense responses against pathogen infections. We recently identified SA-binding protein 2 (SABP2) from tobacco as a protein that displays high affinity for SA and plays a crucial role in the activation of systemic acquired resistance to plant pathogens. Here we report the crystal structures of SABP2, alone and in complex with SA at up to 2.1-[Angstrom] resolution. The structures confirm that SABP2 is a member of the [alpha]/[beta] hydrolase superfamily of enzymes, with Ser-81, His-238, and Asp-210 as the catalytic triad. SA is bound in the active site and is completely shielded from the solvent, consistent with the high affinity of this compound for SABP2. Our biochemical studies reveal that SABP2 has strong esterase activity with methyl salicylate as the substrate, and that SA is a potent product inhibitor of this catalysis. Modeling of SABP2 with MeSA in the active site is consistent with all these biochemical observations. Our results suggest that SABP2 may be required to convert MeSA to SA as part of the signal transduction pathways that activate systemic acquired resistance and perhaps local defense responses as well. salicylic acid | salicylic-acid-binding protein | systemic acquired resistance | [alpha]/[beta] hydrolase

The heme peroxidase enzymes have been classified into three types on the basis of sequence homology with the Class I heme peroxidases containing the prokaryotic enzymes including ascorbate peroxidase (APX). The determination of the crystal structure of recombinant soybean cytosolic APX (rsAPX) in complex with salicylhydroxamic acid (SHA) provides a complete description of substrate binding in APX.

In this work, surface-enhanced vibrational spectroscopy and normal vibrational spectroscopy as well as density functional theory (DFT) computational methods have been employed to investigate the nature of the chemical adsorption and orientation of the surface species generated from salicylic acid at silver surfaces. The structure of salicylic acid and its IR and Raman spectra are determined at the B3LYP/6-31l+G(d,p) level of theory. These results are used in the assignment of the vibrational spectra. Surface-enhanced Raman scattering (SERS) spectra obtained from silver island films thinly coated with salicylic acid confirm chemical adsorption on the Ag nanostructures. To probe the nature of this surface complex, the optimized geometries and IR and Raman spectra of two model salicylate-silver complexes (Ag1 and Ag2) were calculated at the B3LYP/Lan12DZ level of theory. It was found that good agreement exists between experimentally observed SERS spectra and the simulated SERS spectra of a complex with the salicylate monoanion bound to a [Ag.sup.+] ion through its carboxylate group (Ag1). The carboxylate silver salt of salicylic acid (essentially the Ag1 complex) was also prepared, and its IR and Raman spectra were recorded for comparison with the surface-enhanced vibrational spectra. These results, along with the application of surface selection rules, suggest that salicylic acid is deprotonated at silver surfaces, interacting through its carboxylate group a|one, and is preferentially in a tilted head-on orientation. Key words: chemisorption, salicylic acid, silver, density functional theory, surface-enhanced Raman scattering, reflection-absorption IR spectroscopy, surface-enhanced IR absorption.

Full account of the total synthesis and absolute stereo chemical assignment of (+)-torreyanic acid is reported. Thermolysis experiments are conducted on a model dimer based on the torreyanic acid core structure and facile retro Diels-Alder reaction processes and equilibration of diastereomeric 2H- pyrans is observed.

Salicylic anion abstraction and effusion are analyzed in different solvents and solvent mixtures. The significant Stokes shift observed for this anion is considered to indicate a rapid excited phase proton transfer reaction to its keto form.

The total synthesis of both enantiomers of salicylihalamide A, a revision of the absolute configuration assigned to the natural product, and extensive structure-function studies with synthetic salicylihalamide variants are reported. The advantage of a flexible synthetic strategy was highlighted by quickly advance the ring-closing olefin metathesis approach as the method of choice to build the 12-membered benzolactone core of salicylihalamides.

Byline: Takahiro Fujibe (1), Kaori Watanabe (1), Nobuyoshi Nakajima (2), Yuko Ohashi (3), Ichiro Mitsuhara (3), Kotaro T Yamamoto (4), Yuichi Takeuchi (5) Keywords: Keywords: Pathogenesis-related proteins, Phenylalanine ammonia-lyase, Salicylic acid, Tobacco, UV-B Abstract: L. (cv. Petit Havana SR1) were grown under ultraviolet-B (UV-B, 290--320 nm) irradiation, and soluble proteins were extracted from the leaves. Two-dimensional electrophoresis revealed that a minimum of 12 polypeptides were induced by UV-B. Polypeptides which were so abundant as to be detectable by Coomassie brilliant blue staining were then subjected to N-terminal amino acid sequence analyses. Two of the polypeptides were identified as a 23 kDa protein of PS II and 6 as a pathogenesis-related protein 5 (PR-5). Immunoblotting demonstrated that other PR proteins, PR-1 and PR-3 were also induced by UV-B. Salicylic acid (SA), which is an important component of signal transduction that leads to the expression of PR proteins and exhibition of acquired resistance to pathogens, increased in response to exposure to UV-B. In addition, the activity of phenylalanine ammonialyase, which catalyzes the synthesis from phenylalanine of trans-cinnamic acid, the endogenous precursor of SA, was transiently increased by UV-B irradiation. These results suggest that UV-B activates the signal transduction pathway, which is a common step in pathogen infection. Author Affiliation: (1) Course of Environmental and Biological Sciences, Graduate School of Science and Engineering, Hokkaido Tokai University, Sapporo, 005--8601 Japan, JP (2) Biotechnology Research Team, National Institute for Environmental Studies, Tsukuba, 305--0053 Japan, JP (3) Department of Molecular Genetics, National Institute of Agrobiological Resources, Tsukuba, 305--0856 Japan, JP (4) Division of Biological Science, Graduate School of Environmental Earth Science, Hokkaido University, Sapporo, 060--0810 Japan, JP (5) Department of Bioscience and Technology, School of Engineering, Hokkaido Tokai University, Sapporo, 005--8601 Japan Article note: Received 8 May 2000/ Accepted in revised form 29 August 2000

Atomic force microscopy was used to study the kinetics of the dissolution of salicylic acid in aqueous solution. A three dimensional finite element fluid dynamics simulation resulted in precise calculations.

Research has been conducted on the salicylic acid. The role of this acid in iron metabolism has been investigated.

The characteristics of the process of hydrogen or proton transfer in neutral and single positive ions of salicylic acid, o-hydroxybenzaldehyde, and salicylaldimine were investigated using the B3LYP density functional method. Single-point computations at the CCSD(T) level were also conducted. For neutral systems, the reaction corresponds to a proton transfer process coupled with an electronic transfer, which leads to a compound with nonzwitterionic character. A similar behavior is seen for ionized pi radical cations.

Benzoic acid 2-hydroxylase (BA2H) catalyzes the biosynthesis of salicylic acid from benzoic acid. The enzyme has been partially purified and characterized as a soluble protein of 160 kDa. High-efficiency in vivo labeling of salicylic acid with [sup.18][O.sub.2] suggested that BA2H is an oxygenase that specifically hydroxylates the ortho position of benzoic acid. The enzyme was strongly induced by either tobacco mosaic virus inoculation or benzoic acid infiltration of tobacco leaves and it was inhibited by CO and other inhibitors of cytochrome P450 hydroxylases. The BA2H activity was immunodepleted by antibodies raised against SU2, a soluble cytechrome P450 from Streptomyces griseolus. The anti-SU2 antibodies immunoprecipitated a radiolabeled polypeptide of around 160 kDa from the soluble protein extracts of L-[[sup.35]S]methionine-fed tobacco leaves. Purified BA2H showed CO-difference spectra with a maximum at 457 nm. These data suggest that BA2H belongs to a novel class of soluble, high molecular weight cytochrome P450 enzymes.

Salicylic acid signaling appears to activate plant defense responses against pathogens and play an important role in binding catalase and impeding its enzymatic activity. Increased salicylic acid levels correlate with infection of tobacco with tobacco mosaic virus and induction of defense-related genes such as that which encodes pathogenesis-related protein 1 (PR-1). The PR gene expression and disease resistance inhibit catalytic activity. The results indicate that catalase can also act as receptor for salicylic acid.

Attenuated total reflection Fourier transform infrared spectroscopy was used to investigate the bonding of an organic ligand with hydrous metal oxide surfaces. Salicylate was used as the model organic ligand, and its binding with oxide surfaces such as corundum, lepidocrocite, hematite and geothite was observed. Changes in the spectrum of the organic ligand was taken as evidence of bonding. The results have implications for the understanding of the mechanisms of surface reactivity, corrosion control and geochemical processes such as soil formation, sedimentation and weathering.

Agrobacterium and certain viruses express gene in plants through a group of promoter ocs elements. Auxin treatment and salicyclic acid, a plant disease-resistance signal, enhanced ocs element activity in certain regions of the plant.

A complementary DNA encoding a salicylic acid (SA)--binding protein has been cloned. Its properties suggest involvement in SA-mediated induction of systemic acquired resistance (SAR) in plants. The sequence of the protein is similar to that of catalases and the protein exhibits catalase activity. Salicylic acid specifically inhibited the catalase activity in vitro and induced an increase in [H.sub.2][O.sub.2] concentrations in vivo. [H.sub.2][O.sub.2] or compounds, such as SA, that inhibit catalases or enhance the generation of [H.sub.2][O.sub.2], induced expression of defense-related genes associated with SAR. Thus, the action of SA in SAR is likely mediated by elevated amounts of [H.sub.2][O.sub.2]., Infection of plants, particularly by necrotizing pathogens, leads to enhanced resistance to subsequent attacks by the same or even unrelated pathogens (1). This phenomenon is referred to as systemic acquired [...]

A study was done on the formation of 2,5-dihydroxybenzoic acid (DHBA) during the reaction between (super 1)O(sub 2) and salicylic acid using ESR oximetry and electrochemical detection. Results show that the exclusive formation of 2,5 DHBA is highly diagnostic of (super 1)O(sub 2) intermediacy in photochemical and biochemical systems lacking metabolic activity. Furthermore, HPLC-EC was found to be a valuable adjunct to ESR oximetry in the characterization of (super 1)o(sub 2).

INTRODUCTION Chemical peeling continues to be the gold standard in cosmetic enhancement of racial skin. Chemical peeling of the face has been performed for many years. The ancient Egyptians used [...]

Proton tautomerizaton plays an important role in many fields of chemistry and biochemistry. A study is conducted to demonstrate that salicylideneanilines are generally thermochromic in the fluid solution of isopentane or the isopentane/methylcyclohexane mixture and that the proton tautomerization, which is the origin of the thermochromism, is controlled by the aggregation of molecules.

Rice University has produced a new picture of all the 5 million atoms in the protective coat of viruses. Florida scientists, meanwhile, have found bilirubin, a pigment believed to exist only in animals, in certain plants. UK scientists' research on the ability of humans to produce salicylic acid on their own is also discussed.