Bacterial Calcium Carbonate Precipitation in Cave Environments: A Function of Calcium Homeostasis

To determine if microbial species play an active role in the development of calcium carbonate (CaCO ₃ ) deposits (speleothems) in cave environments, we isolated 51 culturable bacteria from a coralloid speleothem and tested their ability to dissolve and precipitate CaCO ₃ . The majority of these isolates could precipitate CaCO ₃ minerals; scanning electron microscopy and X-ray diffractrometry demonstrated that aragonite, calcite and vaterite were produced in this process. Due to the inability of dead cells to precipitate these minerals, this suggested that calcification requires metabolic activity. Given growth of these species on calcium acetate, but the toxicity of Ca ²⁺ ions to bacteria, we created a loss-of-function gene knock-out in the Ca ²⁺ ion efflux protein ChaA. The loss of this protein inhibited growth on media containing calcium, suggesting that the need to remove Ca ²⁺ ions from the cell may drive calcification. With no carbonate in the media used in the calcification studies, we used stable isotope probing with C ¹³ O ₂ to determine whether atmospheric CO ₂ could be the source of these ions. The resultant crystals were significantly enriched in this heavy isotope, suggesting that extracellular CO ₂ does indeed contribute to the mineral structure. The physiological adaptation of removing toxic Ca ²⁺ ions by calcification, while useful in numerous environments, would be particularly beneficial to bacteria in Ca ²⁺ -rich cave environments. Such activity may also create the initial crystal nucleation sites that contribute to the formation of secondary CaCO ₃ deposits within caves.     

Potent inhibitory effects of benzyl and p-xylidine-bis dithiocarbamate sodium salts on activities of mushroom tyrosinase

A novel monofunctional benzyldithiocarbamate, C₆H₅CH₂NHCSSNa (I), and a bifunctional p-xylidine-bis(dithiocarbamate), NaSSCNHCH₂C₆H₄CH₂NHCSSNa (II), as sodium salts, were synthesized by reaction between p-xylylenediamine or benzylamine with CS₂ in the presence of NaOH. They were characterized by spectroscopic techniques such as ¹H NMR, IR, and elemental analysis. These water-soluble compounds were examined for their inhibition of both activities of mushroom tyrosinase (MT) from a commercial source of Agricus bisporus. l-3,4- Dihydroxyphenylalanine (L-DOPA) and l-tyrosine were used as natural substrates for the catecholase and cresolase enzyme reactions, respectively. Kinetic studies showed noncompetitive inhibition of I and mixed type inhibition of II on both activities of MT. The inhibition constant (K_I) of II was smaller than that of I. Raising the temperature from 27 to 37°C caused a decrease in K_I values of I and an increase in values of II. The binding process for inhibition of I was only entropy driven, which means that the predominant interaction in the active site of the enzyme is hydrophobic; meanwhile, the electrostatic interaction can be important for the inhibition of II due to the enthalpy driven binding process. Fluorescence studies showed a decrease of emission intensity without a shift of emission maximum in the presence of different concentrations of compounds. An extrinsic fluorescence study did not show any considerable change of the tertiary structure of MT. Probably, the conformation of inhibitor-bound MT is stable and inflexible compared with uninhibited MT.     

Metal-stabilized rare tautomers of nucleobases

 A Pt^II complex containing N4 bound neutral 1-methylcytosine (1-MeC), trans–[Pt(NH₃)₂(1-MeC-N4)₂](ClO₄)₂ (5), has been prepared and characterized by X-ray analysis. The complex contains the rare iminooxo tautomer form of the cytosine nucleobase. Pt^II binding is through the exocyclic N4 position of the nucleobases, with Pt and the N3 positions in a syn orientation. As a consequence, the proton at N3 is pointing toward the heavy metal, thereby allowing an agostic Pt···HN interaction. Formation of 5 is achieved via oxidation of the linkage isomer trans–[Pt(NH₃)₂(1-MeC-N3)₂]²⁺ (1) to a Pt^IV species (2), followed by metal migration to N4, and subsequent reduction to Pt^II. This process is a text-book example for a redox-assisted metal migration at a heterocyclic ligand. The existence of various rotamers of 5 in aqueous solution is evident from ¹H NMR spectroscopy. The possible role of these rotamers of the metalated rare tautomer, and in particular of those having Pt and the N3 position in an anti arrangement, with regard to base mispairing is discussed. Received: 27 February 1996 / Accepted: 10 June 1996     

Characterization and mapping of R Pi-ber , a novel potato late blight resistance gene from Solanum berthaultii

Phytophthora infestans, the causal agent of late blight, threatens potato production worldwide. An important tool in the management of the disease is the use of resistant varieties. Eleven major resistance genes have been identified and introgressed from Solanum demissum. However, new sources of resistance are continually sought. Here, we report the characterization and refined genetic localization of a resistance gene previously identified as Rber in a backcross progeny of Solanum tuberosum and Solanum berthaultii. In order to further characterize Rber, we developed a set of P. infestans isolates capable of identifying each of the 11 R-genes known to confer resistance to late blight in potato. Our results indicate that Rber is a new resistance gene, different from those recognized in S. demissum, and therefore, it has been named R _Pi-ber according to the current system of nomenclature. In order to add new molecular markers around R _Pi-ber , we used a PCR-based mapping technique, named MASP-map, which located R _Pi-ber in a 3.9 cM interval between markers CT240 and TG63 on potato chromosome X. The location of R _Pi-ber coincides with an area involved in resistance to different pathogens of potato and tomato.     

Isolation of Antibabesial Compounds from Brucea javanica,Curcuma xanthorrhiza,and Excoecaria cochinchinensis

One new curcuminoid, 3′-demethoxycyclocurcumin (1), was isolated from Curcuma xanthorrhiza as an antibabesial compound, together with p-hydroxybenzaldehyde (2) and cleomiscosin A (3) from Brucea javanica and (+)-epiloliolide (4) from Excoecaria cochinchinensis. The antibabesial activities were examined in vitro, and compounds 1–4, and diminazene aceturate were studied with IC₅₀ values of 16.6, 7.6, 15.6, 10.0, and 0.6 μg/ml, respectively.     

Formation of Ni- and Zn-Sulfides in Cultures of Sulfate-Reducing Bacteria

The purpose of this study was to characterize Ni- and Zn-sulfides precipitated in sulfate-reducing bacterial cultures. Fe-free media containing 58 mM SO ₄ ^2? were amended with Ni and Zn chloride followed by inoculation. Precipitates were sampled from cultures after two weeks of incubation at 22, 45, and 60 ^° C. Abiotic controls were prepared by reacting bacteria-free liquid media with Na ₂ S solutions under otherwise identical conditions. Precipitates were collected anaerobically, freeze-dried and analyzed by x-ray diffraction (XRD), scanning electron microscopy, and for total Ni, Zn, and S. In Ni-containing media, biogenic sulfide precipitates were mostly heazelwoodite (Ni ₃ S ₂ ), whereas abiotic precipitates were mixed heazelwoodite and vaesite (NiS ₂ ). The biogenic Ni-precipitates were better crystalline than the corresponding abiotic samples. Sphalerite (ZnS) was identified by XRD in precipitates sampled from Zn-containing media. Scanning electron microscopy revealed disordered morphological features for the sulfides, which occurred mostly as aggregates of fine particles in biogenic samples, whereas abiotic precipitates contained more plate- and needle-like structures.     

Novel achiral titanocene anti-cancer drugs synthesised from bis-<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-dimethylamino fulvene and lithiated heterocyclic compounds

Abstract From the carbolithiation of 6-bis-N,N-dimethylamino fulvene (3a) and different ortho-lithiated heterocycles (furan, thiophene and N-methylpyrrole), the corresponding lithium cyclopentadienide intermediate (4a–c) was formed. These three lithiated intermediates underwent a transmetallation reaction with TiCl₄ resulting in bis-N,N-dimethylamino-functionalised titanocenes 5a–c. When these titanocenes were tested against LLC-PK cells, the IC₅₀-values obtained were of 240, and 270 μM for titanocenes 5b and 5c, respectively. The most cytotoxic titanocene in this paper, 5a with an IC₅₀-value of 36 μM was found to be approximately six times less cytotoxic than its mono-N,N-dimethylamino substituted analogue Titanocene C (IC₅₀ = 5.5 μM) and almost ten times less cytotoxic than cisplatin, which showed an IC₅₀-value of 3.3 μM, when tested on the LLC-PK cell line. Graphical abstract Bis-(bis- (N,N-dimethylamino)-2-(N′-methylpyrrolyl)methylcyclopentadienyl) titanium (IV) dichloride, {η⁵-C₅H₄-CH[N(CH₃)₂]₂[C₅H₃NCH₃]}₂TiCl₂ was synthesised starting from 6-bis-(N,N-dimethylamino) fulvene and 2-N-methylpyrrolyl lithium. Herein, we present the synthesis and DFT structure of the titanocene and two further derivatives followed by MTT-based cytotoxicity tests on pig kidney epithelial (LLC-PK) cells. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

The relationship of the phase and amplitude of the annual cycle of CO2 to phenological events

Background: A key current issue in studies of global CO₂ is the cause of the recent pronounced changes in the timing (phase) and amplitude of its annual cycle.

Aim: To use a sensitivity analysis in order to identify the most influential parameters in a new four-box diffusion model of global CO₂ transport.

Methods: A new diffusion model of global atmospheric transport is developed, implemented by optimisation and used to assess the effects of oceanic, terrestrial and anthropogenic CO₂ fluxes on the annual CO₂ cycle. As the terrestrial phenology of living organisms in the temperate zones is identified as the central process of concern an improved phenological model for the temperate zones is proposed and used in up-scaling from plant to planet.

Results: The diffusion model is found to be able to mimic many of the features observed by the GLOBALVIEW-CO₂ network, including the global trend, latitudinal gradient, and annual waveform.

Conclusions: It is concluded that, out of five rival hypotheses considered at the outset, the springtime phenology of terrestrial biomes is the dominant controller of recent changes to the annual CO₂ cycle.     

Antimicrobial Butyrolactone I Derivatives from the Ecuadorian Soil Fungus Aspergillus terreus Thorn. var terreus

Summary The fungus Aspergillus terreus Thorn var. terreus isolated from an Ecuador soil sample was cultured in liquid and solid media and yielded three main metabolites identified as terreic acid (1), butyrolactone I (2) and lovastatin (3). The natural products as well as three synthetic butyrolactone I derivatives were assessed for antimicrobial activity against Gram-positive and Gram-negative bacteria and fungi as well as for seed germination and seedling growth. Furthermore, the compounds were assessed as inhibitors towards the enzymes acetylcholinesterase, β-glucosidase, and β-glucuronidase. Terreic acid, butyrolactone I, butyrolactone 4′,4′′-diacetate (2.1), and 3′-(3-methylbutyl)-butyrolactone II (2.2) were active towards the phytopathogenic bacteria Erwinia carotovora with IC₅₀ of 5 and 4–18 μg/ml, respectively. Under the same experimental conditions, the IC₅₀ of streptomycin was 1.9 μg/ml. 3′-(3-Methylbutyl)-butyrolactone II was moderately active against Pseudomonas syringae and Botrytis cinerea with IC₅₀ of 21μg/ml and MIC of 15.6 μg/ml, respectively. Butyrolactone I also inhibited germination of the dicot Lactuca sativa with an IC₅₀ of 5 × 10⁻⁵ M. The IC₅₀ of reference herbicide acetochlor was 1 × 10⁻⁵ M. The effect of 2.2 and 2.3, known as butyrolactone III on Panicum millaceum germination and growth was stronger than that of 2 and 2.1. Reduction of the double bond in the isoprenyl side chain of butyrolactone I increased the antibacterial effect against E. carotovora as well as acetylation. To our best knowledge, this is the first report on the antibacterial effect of butyrolactone derivatives towards Erwinia carotovora and the phytopathogenic fungus Botrytis cinerea. The butyrolactone I derivative 2.2 presented a moderate inhibitory effect against the enzyme acetylcholinesterase with an IC₅₀ of 47 μg/ml. Under the same experimental conditions, the reference inhibitor galanthamine had an IC₅₀ of 3 μg/ml.     

Structural and reactivity studies on the ternary system guanine/methionine/trans-[PtCl2(NH3)L] (L=NH3, quinoline): implications for the mechanism of action of nonclassical trans-platinum antitumor complexes

 The present model study explores the chemistry of methionine complexes and ternary methionine-guanine adducts formed by trans-[PtCl₂(NH₃)₂] (1) and antitumor trans-[PtCl₂(NH₃)quinoline] (2) using 1D (¹H, ¹⁹⁵Pt) and 2D NMR spectroscopy. Compound 2 was substitution inert in reactions with N-acetyl-lmethionine [AcMet(H)]. Reactions of trans-[PtCl(NO₃)(NH₃)quinoline] (5) ("monoactivated" 2) with AcMetH in water and acetone at various stoichiometries point to Pt(II)-S binding that requires prior activation of the Pt-Cl bond by labile oxygen donors. Trans-[PtCl{AcMet(H)-S}(NH₃)quinoline](NO₃) (6) and trans-[Pt{AcMet(H)-S}₂(NH₃)quinoline](NO₃)₂ (7) were isolated from these mixtures. At high [Cl^–], AcMet(H) is displaced from 7, giving 6. Frozen stereodynamics in 6 at the thioether-S and slow rotation about the Pt-N_quinoline bond result in four spectroscopically distinguishable diastereomers. ¹H NMR spectra of 7 show faster exchange dynamics due to mutual trans-labilization of the sulfur donors. Substitution of chloride in trans-[PtCl(9-EtGua)(NH₃)L]NO₃ (L=NH₃, 3; L=quinoline, 4; 9-EtGua=9-ethylguanine, which mimics the first DNA binding step of 1 and 2) by methionine-sulfur proceeded ca. 2.5 times slower for the quinoline compound. Both reactions, in turn, proved to be ca. 4 times faster than binding of a second nucleobase under analogous conditions. From the resulting mixtures the ternary adducts trans-[Pt(AcMet-S)(9-EtGua-N7)(NH₃)L](NO₃, Cl) (L=NH₃, 8; L=quinoline, 9) were isolated. A species analogous to 9 formed in a rapid reaction between 6 and 5′-guanosine monophosphate (5′-GMP). From NMR data an AMBER-based solution structure of the resulting adduct, trans-[Pt(AcMet-S)(5′-GMP-N7)(NH₃)quinoline] (10), was derived. The unusual reactivity along the N7-Pt-S axis in 8–10 resulted in partial release of both 9-EtGua and AcMet at high [Cl^–]. Possible consequences of the kinetic and structural effects (e.g., trans effect of sulfur, steric demand of quinoline) observed in these systems with respect to the (trans)formation of potential biological cross-links are discussed. Received: 25 May 1998 / Accepted: 6 August 1998     

Applications of the ETS-NOCV method in descriptions of chemical reactions

The present study characterizes changes in the electronic structure of reactants during chemical reactions based on the combined charge and energy decomposition scheme, ETS-NOCV (extended transition state–natural orbitals for chemical valence). Decomposition of the activation barrier, ΔE ^#, into stabilizing (orbital interaction, ΔE _orb, and electrostatic, ΔE _elstat) and destabilizing (Pauli repulsion, ΔE _Pauli, and geometry distortion energy, ΔE _dist) factors is discussed in detail for the following reactions: (I) hydrogen cyanide to hydrogen isocyanide, HCN → CNH isomerization; (II) Diels-Alder cycloaddition of ethene to 1,3-butadiene; and two catalytic processes, i.e., (III) insertion of ethylene into the metal-alkyl bond using half-titanocene with phenyl-phenoxy ligand catalyst; and (IV) B–H bond activation catalyzed by an Ir-containing catalyst. Various reference states for fragments were applied in ETS-NOCV analysis. We found that NOCV-based deformation densities (Δρ _i) and the corresponding energies ΔE _orb(i) obtained from the ETS-NOCV scheme provide a very useful picture, both qualitatively and quantitatively, of electronic density reorganization along the considered reaction pathways. Decomposition of the barrier ΔE^# into stabilizing and destabilizing contributions allowed us to conclude that the main factor responsible for the existence of positive values of ΔE ^# for all processes (I, II, III and IV) is Pauli interaction, which is the origin of steric repulsion. In addition, in the case of reactions II, III and IV, a significant degree of structural deformation of the reactants, as measured by the geometry distortion energy, plays an important role. Depending on the reaction type, stabilization of the transition state (relatively to the reactants) originating either from the orbital interaction term or from electrostatic attraction can be of vital importance. Finally, use of the ETS-NOCV method to describe catalytic reactions allows extraction of information on the role of catalysts in determination of ΔE ^#.     

Bioorganometallics: First examples of cyclometalated iridium(III) complexes containing di- and tripeptide ester ligands

The synthesis of bis-cyclometalated [Ir(ptpy)₂(gly-gly-OEt)] (2, ptpy = 2-(p-tolyl)pyridinato; gly-gly-OEt = glycylglycine ethyl ester) and [Ir(ptpy)₂(gly-gly-gly-OEt)] (3, gly-gly-gly-OEt = glycylglycylglycine ethyl ester) from the reaction of [{Ir(μ-Cl)(ptpy)₂}₂] (1) with the corresponding peptide ester hydrochlorides in the presence of NaOMe is described. The molecular structure of 2 was confirmed by a single-crystal X-ray diffraction study. The compound crystallized from dichloromethane/iso-hexane in the space group P2₁/a. In the crystal packing the molecules of 2 exhibit N–H?O hydrogen bonds to the neighbor molecules to form dimeric units. The absorption and emission spectra of 2 and 3 were recorded and exhibit these compounds as strong green-emitting complexes.     

克雷伯氏菌属(Klebsiella)细菌比较基因组学分析揭示多复制子抗性质粒介导广泛的抗性基因传播

[目的] 研究克雷伯氏菌与多复制子抗性质粒间的关系,分析细菌携带多复制子质粒对抗生素环境的响应机制。[方法] 以2018-2020年分离的56株不同来源克雷伯氏菌（Klebsiella sp.）分离株为研究对象,利用微量肉汤稀释法评估其多重耐药表型,对分离菌株进行全基因组测序（WGS）,通过细菌全基因组关联分析（BGWAS）技术和比较基因组学方法深入解析多复制子抗性质粒形成的机制。[结果] 耐药表型分析发现野生动物来源的菌株具有更广的耐药谱系,总体Klebsiella sp.对氨苄西林表现出很高的耐药率（80.36%）,尤其是马来穿山甲来源菌株对头孢类抗生素高度耐受,同时对氯霉素、左氧氟沙星和复方新诺明等药物耐受,基因组分析发现这些菌株携带了抗性质粒和更多的抗生素抗性基因。进一步对69个质粒序列分析,发现有28个质粒为多复制子质粒,主要携带bla_CTX-M-15、bla_CTX-M-14、bla_CTX-M-55、bla_OXA-1和bla_TEM-1等β-内酰胺酶基因。细菌携带质粒类型分析认为Klebsiella pneumoniae可能是多复制子质粒的重要宿主,质粒骨架与结构分析发现多复制子质粒多由2个或2个以上单个质粒融合而成,携带此类质粒的菌株不仅获得了更广的耐药表型,而且在全球传播扩散分布逐年增加,因此产生对抗生素环境更强的适应性。[结论] 多重耐药性细菌呈现的表型与携带的多复制子质粒有关,相比较下多复制子质粒比非多复制子质粒有更强的抗性基因携带能力,或许是细菌在强大的抗生素压力下产生的重要响应机制。本研究对于未来探索细菌抗性基因的传播扩散机制具有重要意义。     

Complete basis set,hybrid-DFT study and NBO interpretation of conformational analysis of 2-methoxytetrahydropyran and its thiopyran and selenopyran analogues in relation to the anomeric effect

2-Methoxytetrahydropyran (1), -thiopyran (2) and -selenopyran (3) have been chosen as model compounds to investigate the origin of the anomeric effect (AE). The impacts of the hyperconjugation, electrostatic and steric interactions on the conformational preferences of compounds 1–3 have been analysed by means of complete basis set-4, hybrid-density functional theory (B3LYP/6-311+G**) based methods and natural bond orbital (NBO) interpretation. Both levels of theory showed that the axial conformations of compounds 1–3 are more stable than their equatorial conformations. The Gibbs free energy difference (G _eq–G _ax) values (i.e. ΔG _eq–ax) between the axial and equatorial conformations increase from compound 1 to compound 2 but decrease from compound 2 to compound 3. Based on the NBO results obtained, the AE associated with the electron delocalisation [i.e. Σ(endo-AE_eq + exo-AE_eq) ? Σ(endo-AE_ax + exo-AE_ax)] increase slightly from compound 1 to compound 2 but decrease from compound 2 to compound 3. Similar trend is also observed for the differences between the calculated total steric exchange energy values [i.e. Δ(TSEE)_eq–ax]. On the other hand, the calculated differences between the dipole moment values of the axial and equatorial conformations [i.e. Δ(μ_eq–μ_ax)] decrease from compound 1 to compound 3. These findings led to the proposal that the AE associated with the electron delocalisation (the hyperconjugation effect) is more significant for the explanation of the conformational preferences of compounds 1–3 than the electrostatic model. The correlations between the AE associated with the electron delocalisation, bond orders, TSEE, ΔG _eq–ax, dipole–dipole interactions, structural parameters and conformational behaviours of compounds 1–3 have been investigated.     

A Novel Zeolite Coating for Protection of Concrete Sewers from Biological Sulfuric Acid Attack

Microbial growth inhibition and resistance to biological deterioration of concrete specimens coated with silver-loaded zeolite was evaluated by measuring the time course of bacterial growth, biological sulfur oxidation, and sulfate production using Acidithiobacillus thiooxidans as a corrosive agent. Live bacterial cells declined from an initial inoculum concentration of 1.1 × 10₄ cell ml_-1 to zero in 10 days, during which only 0.5–1% of the initial sulfur concentration of 10 g l_-1 was biologically oxidized, corresponding to sulfate production rates of 35–42 mg SO ₄ ^{2 ?} g ^{? 1} S ^{? 1} . Leaching coefficients of calcium and silicon in the specimens coated with silver-loaded zeolite of 1.6 × 10 ^{? 4} to 4.6 × 10 ^{? 2} cm ² d ^{? 1} respectively, were only 0.8% and 1% of the uncoated specimens.     

The Origin and Age of Biogeochemical Trends in Deep Fracture Water of the Witwatersrand Basin,South Africa

Water residing within crustal fractures encountered during mining at depths greater than 500 meters in the Witwatersrand basin of South Africa represents a mixture of paleo-meteoric water and 2.0–2.3 Ga hydrothermal fluid. The hydrothermal fluid is highly saline, contains abiogenic CH ₄ and hydrocarbon, occasionally N ₂ , originally formed at ～ 250–300°C and during cooling isotopically exchanged O and H with minerals and accrued H ₂ , ⁴ He and other radiogenic gases. The paleo-meteoric water ranges in age from ～ 10 Ka to > 1.5 Ma, is of low salinity, falls along the global meteoric water line (GMWL) and is CO ₂ and atmospheric noble gas-rich. The hydrothermal fluid, which should be completely sterile, has probably been mixing with paleo-meteoric water for at least the past ～100 Myr, a process which inoculates previously sterile environments at depths > 2.0 to 2.5 km. Free energy flux calculations suggest that sulfate reduction is the dominant electron acceptor microbial process for the high salinity fracture water and that it is 10 ⁷ times that normally required for cell maintenance in lab cultures. Flux calculations also indicate that the potential bioavailable chemical energy increases with salinity, but because the fluence of bioavailable C, N and P also increase with salinity, the environment remains energy-limited. The ⁴ He concentrations and theoretical calculations indicate that the H ₂ that is sustaining the subsurface microbial communities (e.g. H ₂ -utilizing SRB and methanogens) is produced by water radiolysis at a rate of ～1 nM yr ^?1 . Microbial CH ₄ mixes with abiogenic CH ₄ to produce the observed isotopic signatures and indicates that the rate of methanogenesis diminishes with depth from ～ 100 at < 1 kmbls, to < 0.01 nM yr ^?1 at > 3 kmbls. Microbial Fe(III) reduction is limited due to the elevated pH. The δ¹³C of dissolved inorganic carbon is consistent with heterotrophy rather than autotrophy dominating the deeper, more saline environments. One potential source of the organic carbon may be microfilms present on the mineral surfaces.     

Acrolein-detoxifying isozymes of glutathione transferase in plants

Main conclusion

Acrolein is a lipid-derived highly reactive aldehyde, mediating oxidative signal and damage in plants. We found acrolein-scavenging glutathione transferase activity in plants and purified a low K _M isozyme from spinach.

Various environmental stressors on plants cause the generation of acrolein, a highly toxic aldehyde produced from lipid peroxides, via the promotion of the formation of reactive oxygen species, which oxidize membrane lipids. In mammals, acrolein is scavenged by glutathione transferase (GST; EC 2.5.1.18) isozymes of Alpha, Pi, and Mu classes, but plants lack these GST classes. We detected the acrolein-scavenging GST activity in four species of plants, and purified an isozyme showing this activity from spinach (Spinacia oleracea L.) leaves. The isozyme (GST-Acr), obtained after an affinity chromatography and two ion exchange chromatography steps, showed the K _M value for acrolein 93 μM, the smallest value known for acrolein-detoxifying enzymes in plants. Peptide sequence homology search revealed that GST-Acr belongs to the GST Tau, a plant-specific class. The Arabidopsis thaliana GST Tau19, which has the closest sequence similar to spinach GST-Acr, also showed a high catalytic efficiency for acrolein. These results suggest that GST plays as a scavenger for acrolein in plants.

     

Construction of analytically solvable models for interacting species

By observing that the n-tuple of rate functionsQ(c) is orthogonal to the c-space gradients of each of the (n - 1) constants of the motion Φ _v (c), a generic canonical expression for the rate functions is given in terms of the exterior product of the gradients of the (n - 1) Φ _v 's. For models withQ so prescribed from the outset, an analytical general solution is obtainable directly for the system of autonomous ordinary differential equations dc/dt =Q(c). Thus, the generic canonical expression for the rate functions can be utilized to construct analytically solvable models for interacting biological species, as ilIus~rated by examples here.     

Synthesis and antileishmanial evaluation of 1-aryl-4-(4,5-dihydro-1H-imidazol-2-yl)-1H-pyrazole derivatives

A series of 1-aryl-4-(4,5-dihydro-1H-imidazol-2-yl)-1H-pyrazoles (4a–g) and 5-amino-1-aryl-4-(4,5-dihydro-1H-imidazol-2-yl)-1H-pyrazoles (5a–g) were synthesized and evaluated in vitro against three Leishmania species: L. amazonensis, L. braziliensis and L. infantum (L. chagasi syn.). The cytotoxicity was assessed. Among the derivatives examined, six compounds emerged as the most active on promastigotes forms of L. amazonensis with IC₅₀ values ranging from 15 to 60 μM. The reference drug pentamidine presented IC₅₀ = 10 μM. However, these new compounds were less cytotoxic than pentamidine. Based on these results, the more promising derivative 5d was tested further in vivo. This compound showed inhibition of the progression of cutaneous lesions in CBA mice infected with L. amazonensis relative to an untreated control.     

Structures of Gibberellins A39, A48, A49 and a New Kaurenolide in Cucurbita pepo L.

The structures of three new gibberellins A₃₀, A₄₈ and A₄₉ and a new kaurenolide, isolated from seeds of Cucurbita pepo L., were elucidated. The structures of GA₃₉, GA₄₈ and GA₄₉ were shown to be ent-3α,12β-dihydroxygibberell-16-ene-7,19,20-trioic acid (1), ent-2α,3α,10,12α-tetrahydroxy-20-norgibberell-16-ene-7,19-dioic acid 19,10-lactone (5) and the epimer at C–12 of GA₄₈ (8), respectively. The kaurenolide was shown to have the structure: ent-6β,7α,12β-trihydroxykaur-16-en-19-oic acid 19,6-lactone (14).