Effects of Nano-anatase TiO<Subscript>2</Subscript> on Absorption,Distribution of Light,and Photoreduction Activities of Chloroplast Membrane of Spinach

The effects of nano-anatase TiO₂ on light absorption, distribution, and conversion, and photoreduction activities of spinach chloroplast were studied by spectroscopy. Several effects of nano-anatase TiO₂ were observed: (1) the absorption peak intensity of the chloroplast was obviously increased in red and blue region, the ratio of the Soret band and Q band was higher than that of the control; (2) the great enhancement of fluorescence quantum yield near 680 nm of the chloroplast was observed, the quantum yield under excitation wavelength of 480 nm was higher than the excitation wavelength of 440 nm; (3) the excitation peak intensity near 440 and 480 nm of the chloroplast significantly rose under emission wavelength of 680 nm, and F ₄₈₀ / F ₄₄₀ ratio was reduced; (4) when emission wavelength was at 720 nm, the excitation peaks near 650 and 680 nm were obviously raised, and F ₆₅₀ / F ₆₈₀ ratio rose; (5) the rate of whole chain electron transport, photochemical activities of PSII DCPIP photoreduction and oxygen evolution were greatly improved, but the photoreduction activities of PSI were a little changed. Together, the studies of the experiments showed that nano-anatase TiO₂ could increase absorption of light on spinach chloroplast and promote excitation energy to be absorbed by LHCII and transferred to PSII and improve excitation energy from PSI to be transferred to PSII, thus, promote the conversion from light energy to electron energy and accelerate electron transport, water photolysis, and oxygen evolution.     

Characterization of a xylitol dehydrogenase and a d-arabitol dehydrogenase from the thermo- and acidophilic red alga Galdieria sulphuraria

Galdieria sulphuraria (Galdieri) Merola can grow heterotrophically on at least ten different polyols. We investigated their metabolic path to glycolysis/gluconeogenesis and identified two NAD-dependent polyol dehydrogenases. Activity of other enzymes metabolizing mannitol or sorbitol could not be detected. The two dehydrogenases had a broad substrate specificity and were termed xylitol dehydrogenase (EC 1.1.1.14; substrate specificity: xylitol > d-sorbitol > d-mannitol > l-arabitol) and d-arabitol dehydrogenase (EC 1.1.1.11; substrate specificity: d-arabitol > l-fucitol > d-mannitol > d-threitol) according to the substrate with the lowest K _m value. The xylitol dehydrogenase was stable during purification. In contrast, the d-arabitol dehydrogenase was thermolabile and depended on divalent ions for stability and activity, preferentially Mn²⁺ and Ni²⁺. The molecular mass of the xylitol dehydrogenase was estimated to be 295 kDa by size-exclusion chromatography and 220 kDa by rate-sedimentation centrifugation. The d-arabitol dehydrogenase had a molecular mass of 105 kDa as determined by rate-sedimentation centrifugation. The specific activity of both enzymes increased about fourfold when cells were transferred from autotrophic to heterotrophic conditions regardless of whether sugars or polyols were supplied as substrates. The significance of polyol metabolism in Galdieria sulphuraria with regard to the natural habitat of the alga is discussed. Received: 15 January 1997 / Accepted: 12 February 1997     

DFT and MP2 investigations of <Emphasis Type="SmallCaps">L</Emphasis>-proline and its hydrated complexes

A theoretical study of L-proline-nH₂O (n = 1–3) has been performed using the hybrid DFT-B3LYP and MP2 methods together with the 6-311++G(d,p) basis set. The results show that the P2 conformer is energetically favorable when forming a hydrated structure, and the hydration of the carboxyl group leads to the greatest stability. For hydrated complexes, the adiabatic and vertical singlet–triplet excitation energies tend to decrease with the addition of water molecules. The hydration energy indicates that in the hydrated complexes the order of stability is: binding site 2 > binding site 1 > binding site 3, and binding site 12 > binding site 23 > binding site 13. As water molecules are added, the stabilities of these hydrated structures gradually increase. In addition, an infrared frequency analysis indicated that there are some differences in the low-frequency range, which are mainly dominated by the O–H stretching or bending vibrations of different water molecules. All of these results should aid our understanding of molecular behavior and provide reference data for further studies of biological systems.     

A physical model for PDZ-domain/peptide interactions

The PDZ domain is an interaction motif that recognizes and binds the C-terminal peptides of target proteins. PDZ domains are ubiquitous in nature and help assemble multiprotein complexes that control cellular organization and signaling cascades. We present an optimized energy function to predict the binding free energy (ΔΔG) of PDZ domain/peptide interactions computationally. Geometry-optimized models of PDZ domain/peptide interfaces were built using Rosetta, and protein and peptide side chain and backbone degrees of freedom are minimized simultaneously. Using leave-one-out cross-validation, Rosetta’s energy function is adjusted to reproduce experimentally determined ΔΔG values with a correlation coefficient of 0.66 and a standard deviation of 0.79 kcal mol⁻¹. The energy function places an increased weight on hydrogen bonding interactions when compared to a previously developed method to analyze protein/protein interactions. Binding free enthalpies (ΔΔH) and entropies (ΔS) are predicted with reduced accuracies of R = 0.60 and R = 0.17, respectively. The computational method improves prediction of PDZ domain specificity from sequence and allows design of novel PDZ domain/peptide interactions.     

High-cell-density cultivation for co-production of ergosterol and reduced glutathione by <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis>

Two different high-cell-density cultivation processes based on the mutant Saccharomyces cerevisiae GE-2 for simultaneous production of glutathione and ergosterol were investigated. Compared with keeping the ethanol volumetric concentration at a constant low level, feedback control of glucose feeding rate (F) by keeping the descending rate of ethanol volumetric concentration (ΔE/Δt) between −0.1% and 0.15% per hour was much more efficient to achieve a high glutathione and ergosterol productivity. This bioprocess overcomes some disadvantages of traditional S. cerevisiae-based cultivation process, especially shortening cultivation period and making the cultivation process steady-going. A classical on or off controller was used to manipulate F to maintain ΔE/Δt at its set point. The dry cell weight, glutathione yield and ergosterol yield reached 110.0 ± 2.6 g/l, 2,280 ± 76 mg/l, and 1,510 ± 28 mg/l in 32 h, respectively.     

Syntheses of dopa glycosides using glucosidases

Syntheses of l-dopa 1a glucoside 10a,b and dl-dopa 1b glycosides 10–18 with d-glucose 2, d-galactose 3, d-mannose 4, d-fructose 5, d-arabinose 6, lactose 7, d-sorbitol 8 and d-mannitol 9 were carried out using amyloglucosidase from Rhizopus mold, β-glucosidase isolated from sweet almond and immobilized β-glucosidase. Invariably, l-dopa and dl-dopa gave low to good yields of glycosides 10–18 at 12–49% range and only mono glycosylated products were detected through glycosylation/arylation at the third or fourth OH positions of l-dopa 1a and dl-dopa 1b. Amyloglucosidase showed selectivity with d-mannose 4 to give 4-O-C1β and d-sorbitol 8 to give 4-O-C6-O-arylated product. β-Glucosidase exhibited selectivity with d-mannose 4 to give 4-O-C1β and lactose 7 to give 4-O-C1β product. Immobilized β-glucosidase did not show any selectivity. Antioxidant and angiotensin converting enzyme inhibition (ACE) activities of the glycosides were evaluated glycosides, out of which l-3-hydroxy-4-O-(β-d-galactopyranosyl-(1′→4)β-d-glucopyranosyl) phenylalanine 16 at 0.9 ± 0.05 mM and dl-3-hydroxy-4-O-(β-d-glucopyranosyl) phenylalanine 11b,c at 0.98 ± 0.05 mM showed the best IC₅₀ values for antioxidant activity and dl-3-hydroxy-4-O-(6-d-sorbitol)phenylalanine 17 at 0.56 ± 0.03 mM, l-dopa-d-glucoside 10a,b at 1.1 ± 0.06 mM and dl-3-hydroxy-4-O-(d-glucopyranosyl)phenylalanine 11a-d at 1.2 ± 0.06 mM exhibited the best IC₅₀ values for ACE inhibition. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Ascitic fluid and serum from rats with acute pancreatitis injure rat pancreatic tissues and alter the expression of heat shock protein 60

Acute pancreatitis (AP) is an inflammatory process in which cytokines and chemokines are involved. After onset, extrapancreatic stimuli can induce the expression of cytokines in pancreatic acinar cells, thereby amplifying this inflammatory loop. To further determine the role and mechanism of irritating agents in the pathogenesis of AP, rat pancreatic tissues were stimulated with ascitic fluid (APa) and serum (APs) from rats with AP or with lipopolysaccharide (LPS). In addition, the alteration of heat shock protein 60 (HSP60) expression was evaluated. Rat pancreas was removed and meticulously snipped to fragments. The snips were cultured for up to 48 h. During this period, the tissue viability as well as amylase and TNF-α levels in the supernatant and the HSP60 expression in the pancreatic tissue before and after stimulation by APa, APs, and LPS were assayed time-dependently. At different time-points during the culture, the viability and the amylase activity in the pancreatic tissue remained largely stable. After stimulation with APa, APs, or LPS for 1 h, the pancreatic tissues showed some damage, and this was followed by a sharp decrease in the viability accompanied by increased levels of amylase and TNF-α in the culture medium 2 or 4 h after stimulation (p < 0.05). In contrast, both the HSP60 mRNA and protein levels had a relatively high expression in the freshly prepared tissue fragments (0 h). As the culturing period was extended, the expression of HSP60 mRNA decreased only slightly; at the same time, the HSP60 protein levels decreased over a prolonged culture time, significantly so from 12 through 48 h (p < 0.05). After stimulation with APs, APa, or LPS, both the expression of HSP60 mRNA and protein in the tissue fragments increased slightly at 1 h and decreased significantly thereafter at 2 and 4 h (p < 0.05). APa, APs, or LPS induce injuries on isolated pancreatic tissues, accompanied by an altered HSP60 expression pattern in a time-dependent manner.     

Age and composition of carbonate shoreface sediments, Kailua Bay, Oahu, Hawaii

The origin, age, and dynamics of carbonate sediments in Kailua Bay on Oahu, Hawaii, are described. The shoreface (from shoreline to 4 km offshore) consists of a broad (5 km²) fringing coral reef ecosystem bisected by a sinuous, shore-normal, sand-filled paleostream channel 200–300 m wide. The median grain diameter of surface sands is finest on the beach face (<0.3 mm) and increases offshore along the channel axis. Kailua sands are >90% biogenic carbonate, dominated by skeletal fragments of coralline algae (e.g. Porolithon, up to 50%) followed by the calcareous green alga Halimeda (up to 32%), coral fragments (1–24%), mollusc fragments (6–21%), and benthic foraminifera (1–10%). Sand composition and age across the shoreface are correlated to carbonate production. Corals and coralline algae, principal builders of the reef framework, are younger and more abundant in sands along the channel axis and in offshore reefal areas, while Halimeda, molluscs, and foraminifera are younger and more dominant in nearshore waters shoreward of the main region of framework building. Shoreface sediments are relatively old. Of 20 calibrated radiocarbon dates on skeletal constituents of sand, only three are younger than 500 years b.p.; six are 500–1000 years b.p.; six are 1000–2000 years b.p.; and five are 2000–5000 years b.p. Dated fine sands are older than medium to coarse sands and hence may constitute a reservoir of fossil carbonate that is distributed over the entire shoreface. Dominance of fossiliferous sand indicates long storage times for carbonate grains, which tend to decrease in size with age, such that the entire period of relative sea-level inundation (∼5000 years) is represented in the sediment. Despite an apparently healthy modern coral ecosystem, the surficial sand pool of Kailua Bay is dominated by sand reflecting an antecedent system, possibly one that existed under a +1–2 m sea-level high stand during the mid- to late Holocene. Accepted: 20 December 1999     

Artificially increased ascorbate content affects zeaxanthin formation but not thermal energy dissipation or degradation of antioxidants during cold-induced photooxidative stress in maize leaves

Infiltrating detached maize (Zeamays L.) leaves with L-galactono-1,4-lactone (L-GAL) resulted in a 4-fold increase in the content of leaf ascorbate. Upon exposure to high irradiance (1000 μmol photons m⁻² s⁻¹) at 5 °C, L-GAL leaves de-epoxidized the xanthophyll-cycle pigments faster than the control leaves; the maximal ratio of de-epoxidized xanthophyll-cycle pigments to the whole xanthophyll-cycle pool was the same in both leaf types. The elevated ascorbate content, together with the faster violaxanthin de-epoxidation, did not affect the degree of photoinhibition and the kinetics of the recovery from photoinhibition, assayed by monitoring the maximum quantum efficiency of photosystem II primary photochemistry (F_v/F_m). Under the experimental conditions, the thermal energy dissipation seems to be zeaxanthin-independent since, in contrast to the de-epoxidation, the decrease in the efficiency of excitation-energy capture by open photosystem II reaction centers (F_v′/F_m′) during the high-irradiance treatment at low temperature showed the same kinetic in both leaf types. This was also observed for the recovery of the maximal fluorescence after stress. Furthermore, the elevated ascorbate content did not diminish the degradation of pigments or α-tocopherol when leaves were exposed for up to 24 h to high irradiance at low temperature. Moreover, a higher content of ascorbate appeared to increase the requirement for reduced glutathione. Received: 20 May 1999 / Accepted: 29 October 1999     

Kinetic studies on the reactions of Fusarium galactose oxidase with five different substrates in the presence of dioxygen

 Reactions (25  °C) of galactose oxidase, GOase_ox from Fusarium NRRL 2903 with five different primary-alcohol-containing substrates RCH₂OH:- D-galactose (I) and 2-deoxy-d-galactose (II) (monosaccharides); methyl-β-d-galactopyranoside (III) (glycoside);d-raffinose (IV) (trisaccharide); and dihydroxyacetone (V) have been studied in the presence of O₂. The GOase_ox state has a tyrosyl radical coordinated at a square-pyramidal Cu^II active site, and is a two-equivalent oxidant. Reactant concentrations were [GOase_ox] (0.8–10 μM), RCH₂OH (1.0–6.0 mM), and O₂ (0.14–0.29 mM), with I=0.100 M (NaCl). The reactions, monitored at 450 nm by stopped-flow spectrophotometry, terminated with depletion of the O₂. Each trace was fitted to the competing reactions GOase_ox+RCH₂ OH → GOase_redH₂+RCHO (k ₁), and GOase_redH₂+O₂→ GOase_ox+H₂O₂ (k ₂), with GOase_redH₂ written as the doubly protonated two-electron-reduced Cu^I product. It was necessary to avoid auto-redox interconversion of GOase_ox and GOase_semi . Information obtained at pH 7.5 indicates a 5 : 95 (ox : semi) "native" mix equilibration complete in ∼3 h. At pH >7.5, rate constants 10^–4 k ₁ / M^–1 s^–1 for the reactions of GOase_ox with (I) (1.19), (II) (1.07), (III) (1.29), (IV) (1.81), (V) (2.94) were determined. On decreasing the pH to 5.5, k ₁ values decreased by factors of up to a half, and acid dissociation pK _as in the range 6.6–6.9 were obtained. UV-Vis spectrophotometric studies on GOase_ox gave an independently determined pK _a of 6.7. No corresponding reactions of the Tyr495Phe variant were observed, and there are no similar UV-Vis absorbance changes for this variant. The pK _a is therefore assigned to protonation of Tyr-495 which is a ligand to the Cu. The rate constant k ₂ (1.01×10⁷ M^–1 s^–1) is independent of pH in the range 5.5–9.0 investigated, suggesting that H⁺ (or H-atoms) for the O₂ → H₂O₂ change are provided by the active site of GOase_red . The Cu^I of GOase_red is less extensively complexed, and a coordination number of three is likely. Received: 4 February 1997 / Accepted: 16 May 1997     

Comparison of Different Forms of Dietary Selenium Supplementation on Growth Performance,Meat Quality,Selenium Deposition,and Antioxidant Property in Broilers

This study was conducted to investigate the effects of different sources of dietary selenium (Se) supplementation on growth performance, meat quality, Se deposition, and antioxidant property in broilers. A total of 600 one-day-old Ross 308 broilers with an average body weight (BW) of 44.30 ± 0.49 g were randomly allotted to three treatments, each of which included five replicates of 40 birds. These three groups received the same basal diet containing 0.04 mg Se/kg, supplemented with 0.15 mg Se/kg from sodium selenite (SS) or from l-selenomethionine (l-Se-methionine (Met)) or from d-selenomethionine (d-Se-Met). The experiment lasted 42 days. Both Se source and time significantly influenced (p < 0.01) drip loss of breast muscle. Supplementation with l-Se-Met and d-Se-Met were more effective (p < 0.05) in decreasing drip loss than SS. Besides, the pH value of breast muscle was also significantly influenced (p < 0.05) by time. The SS-supplemented diet increased more (p < 0.05) liver, kidney, and pancreas glutathione peroxidase (GSH-Px) activities than the d-Se-Met-supplemented diet. In addition, l-Se-Met increased more (p < 0.01) liver and pancreas GSH-Px activities than d-Se-Met. The antioxidant status was greatly improved in broilers of l-Se-Met-treated group in comparison with the SS-treated group and was illuminated by the increased glutathione (GSH) concentration in serum, liver, and breast muscle (p < 0.05); superoxide dismutase (SOD) activity in liver (p < 0.01); total antioxidant capability (T-AOC) in kidney, pancreas, and breast muscle (p < 0.05) and decreased malondialdehyde (MDA) concentration in kidney and breast muscle (p < 0.05) of broilers. Besides, supplementation with d-Se-Met was more effective (p < 0.01) in increasing serum GSH concentration and decreasing breast muscle MDA concentration than SS. l-Selenomethionine supplementation significantly increased GSH concentration in liver and breast muscle (p < 0.05); SOD activity in liver (p < 0.01); and T-AOC in liver, pancreas, and breast muscle (p < 0.05) of broilers, compared with broilers fed d-Se-Met diet. The addition of l-Se-Met and d-Se-Met increased (p < 0.01) Se concentration in serum and different organs studied of broilers in comparision with broilers fed SS diet. Therefore, dietary l-Se-Met and d-Se-Met supplementation could improve antioxidant capability and Se deposition in serum and tissues and reduce drip loss of breast muscle in broilers compared with SS. Besides, l-Se-Met is more effective than d-Se-Met in improving antioxidant status in broilers.     

Study of Antibacterial Activity of ZnZnbisporphyrin Complexes and its Free Components on <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> by Microcalorimetry

The antibacterial effect of Zn(II), tetraphenyl porphyrin (TPP), propdioxyl bridged tetraphenyl bisporphyrin 1, and its metallobisporphyrin complexes (ZnMnbisporphyrin 2 and ZnZnbisporphyrin 3) towards Staphylococcus aureus growth was investigated by microcalorimetry at 37°C. Differences in their capacities to inhibit the growth metabolism of S. aureus were observed. By analyzing the power–time curves, crucial parameters such as the rate constant of bacterial growth (k), inhibitory ratio (I), and generation time (t _G) were determined. The growth rate constant (k) of S. aureus (in the log phase) in the presence of the drugs decreased linearly with increasing concentrations of the complexes. The sequence of the antibacterial activities of these compounds tested was 3 > 2 > 1 > Zn(II) > TPP. ZnZnbisporphyrin 3 is proposed to benefit from the synergetic effects of Zn(II) and 1.     

Regulation of auxin transport by aminopeptidases and endogenous flavonoids

 The 1-N-naphthylphthalamic acid (NPA)-binding protein is a putative negative regulator of polar auxin transport that has been shown to block auxin efflux from both whole plant tissues and microsomal membrane vesicles. We previously showed that NPA is hydrolyzed by plasma-membrane amidohydrolases that co-localize with tyrosine, proline, and tryptophan-specific aminopeptidases (APs) in the cotyledonary node, hypocotyl-root transition zone and root distal elongation zone of Arabidopsisthaliana (L.) Heynh. seedlings. Moreover, amino acyl-β-naphthylamide (aa-NA) conjugates resembling NPA in structure have NPA-like inhibitory activity on growth, suggesting a possible role of APs in NPA action. Here we report that the same aa-NA conjugates and the AP inhibitor bestatin also block auxin efflux from seedling tissue. Bestatin and, to a lesser extent, some aa-NA conjugates were more effective inhibitors of low-affinity specific [³H]NPA-binding than were the flavonoids quercetin and kaempferol but had no effect on high-affinity binding. Since the APs are inhibited by flavonoids, we compared the localization of endogenous flavonoids and APs in seedling tissue. A correlation between AP and flavonoid localization was found in 5- to 6-d-old seedlings. Evidence that these flavonoids regulate auxin accumulation in vivo was obtained using the flavonoid-deficient mutant, tt4. In whole-seedling [¹⁴C]indole-3-acetic acid transport studies, the pattern of auxin distribution in the tt4 mutant was shown to be altered. The defect appeared to be in auxin accumulation, as a considerable amount of auxin escaped from the roots. Treatment of the tt4 mutant with the missing intermediate naringenin restored normal auxin distribution and accumulation by the root. These results implicate APs and endogenous flavonoids in the regulation of auxin efflux. Received: 2 December 1999 / Accepted: 16 January 2000     

A Series of Novel Rare Earth Molybdotungstosilicate Heteropolyoxometalates Binding to Bovine Serum Albumin: Spectroscopic Approach

Heteropolyoxometalate complexes have been widely applied in many fields. In this paper, the interaction between a series of novel rare earth molybdotungstosilicate heteropolyoxometalates, K₁₀H₃[Ln(SiMo₆W₅O₃₉)₂]·xH₂O (abbr. LnW₅, Ln = Pr (x = 30), Gd (x = 29), Dy (x = 28), and Yb (x = 31)), and bovine serum albumin (BSA) was investigated by spectroscopic approach under the physiological conditions. In the mechanism discussion, it was proved that the fluorescence quenching of BSA by LnW₅ is a result of the formation of LnW₅–BSA complex. Fluorescence quenching constants were determined using the Stern–Volmer equation to provide a measure of the binding affinity between LnW₅ and BSA. The binding affinity ranked in the order GdW₅ > DyW₅ > PrW₅ > YbW₅. The results of thermodynamic parameters ΔG, ΔH, and ΔS at different temperatures indicate that van der Waals interactions and hydrogen bonds play a major role for LnW₅–BSA association. Furthermore, the distance r between donor (BSA) and acceptor (LnW₅) was obtained according to fluorescence resonance energy transfer.     

Hydrogen bonding interactions in PN···HX complexes: DFT and ab initio studies of structure, properties and topology

Spin-restricted DFT (X3LYP and B3LYP) and ab initio (MP2(fc) and CCSD(fc)) calculations in conjunction with the Aug-CC-pVDZ and Aug-CC-pVTZ basis sets were performed on a series of hydrogen bonded complexes PN···HX (X = F, Cl, Br) to examine the variations of their equilibrium gas phase structures, energetic stabilities, electronic properties, and vibrational characteristics in their electronic ground states. In all cases the complexes were predicted to be stable with respect to the constituent monomers. The interaction energy (ΔE) calculated using a super-molecular model is found to be in this order: PN···HF > PN···HCl > PN···HBr in the series examined. Analysis of various physically meaningful contributions arising from the Kitaura-Morokuma (KM) and reduced variational space self-consistent-field (RVS-SCF) energy decomposition procedures shows that the electrostatic energy has significant contribution to the over-all interaction energy. Dipole moment enhancement (Δμ) was observed in these complexes expected of predominant dipole-dipole electrostatic interaction and was found to follow the trend PN···HF > PN···HCl > PN···HBr at the CCSD level. However, the DFT (X3LYP and B3LYP) and MP2 levels less accurately determined these values (in this order HF < HCl < HBr). Examination of the harmonic vibrational modes reveals that the PN and HX bands exhibit characteristic blue- and red shifts with concomitant bond contraction and elongation, respectively, on hydrogen bond formation. The topological or critical point (CP) analysis using the static quantum theory of atoms in molecules (QTAIM) of Bader was considered to classify and to gain further insight into the nature of interaction existing in the monomers PN and HX, and between them on H-bond formation. It is found from the analysis of the electron density ρ _c , the Laplacian of electron charge density ∇²ρ_c, and the total energy density (H _c ) at the critical points between the interatomic regions that the interaction N···H is indeed electrostatic in origin (ρ_c > 0, ∇²ρ_c > 0 and H_c > 0 at the BCP) whilst the bonds in PN (ρ_c > 0, ∇²ρ_c > 0 and H_c < 0) and HX ((ρ_c > 0, ∇²ρ_c < 0 and H_c < 0)) are predominantly covalent. A natural bond orbital (NBO) analysis of the second order perturbation energy lowering, E⁽²⁾, caused by charge transfer mechanism shows that the interaction N···H is n(N) → BD*(HX) delocalization.     

Inheritance of high palmitic acid content in the seed oil of sunflower mutant CAS-5

 Sunflower genotypes with increased levels of palmitic acid (C16 : 0) in the seed oil could be useful for food and industrial applications. The objective of the present study was to determine the inheritance of the high C16 : 0 content in the sunflower mutant line CAS-5 (>25% of the total oil fatty acids). This mutant was reciprocally crossed with the lines HA-89 (5.7% C16 : 0) and BSD-2-691 (5.4% C16 : 0), the latter being the parental line from which CAS-5 was isolated. No maternal effect for the C16 : 0 content was observed from the analysis of F₁ seeds in any of the crosses. The inheritance study of the C16 : 0 content in F₁, F₂ and BC₁F₁ seeds from the crosses of CAS-5 with its parental line BSD-2-691 indicated that the segregation fitted a model of two alleles at one locus with partial dominance for the low content. The analysis of the fatty acid composition in the F₂ populations from the crosses with HA-89 revealed a segregation fitting a ratio 19 : 38 : 7 for low (<7.5%), middle (7.5–15%), and high (>25%) C16 : 0 content, respectively. This segregation was explained on the basis of three loci (P1, P2, P3) each having two alleles showing partial dominance for low content. The genotypes with a high C16 : 0 content were homozygous for the recessive allele p1 and for at least one of the other two recessive alleles, p2 or p3. This model was further confirmed with the analysis of the F₃ and the BC₁F₁ generations. It was concluded that both the recessive alleles p2 and p3 were already present in the BSD-2-691 line, the allele p1 being the result of a mutation from P1. This genetic study will facilitate breeding strategies associated with the incorporation of the high C16 : 0 trait into agronomically acceptable sunflower hybrids. Received: 30 March 1998 / Accepted: 13 August 1998     

Transport of Ca2+ across the tonoplast of intact vacuoles from Chenopodium album L. suspension cells: ATP-dependent import and inositol-1,4,5-trisphosphate-induced release

The removal of Ca²⁺ from the medium by intact vacuoles and microsomes of Chenopodium album was investigated by measuring INDO-1 fluorescence emission at 400 and 480 nm and the response of Ca²⁺ -selective mini-electrodes. The removal of Ca²⁺ depended on the presence of MgATP, displaying an apparent K _mATP of about 50 μM, a K _mCa of 400–500 nM, and a nucleotide specificity (%) of ATP (100) > CTP (49) > GTP (28) > UTP (20) > ADP = AMP (0). In the presence of saturating MgATP, the vacuoles reduced the [Ca²⁺] of the medium below 30 nM. Part of the Ca²⁺ removed from the medium was released again after adding micromolar concentrations of inositol-1,4,5-trisphosphate. This release of Ca²⁺ was inhibited by heparin. Since digitonin caused the release of the entire amount of Ca²⁺ removed from the medium in the presence of MgATP, we argue that the Ca²⁺ is not bound to membranes or sequestered otherwise, but is transported into the vacuoles (or vesicles) and remains freely mobile there. In accordance with the current literature, we conclude that the plant vacuole is an important store for mobile Ca²⁺ to be released for purposes of signal transduction. Since changes in the trans-tonoplast ΔpH and inhibition of the H⁺-translocating pumps had no significant influence on the ATP-dependent removal of Ca²⁺ from the cytoplasmic side, we argue that in C. album ATP-driven Ca²⁺ transport is the predominant form of Ca²⁺ translocation into the vacuole. Received: 11 July 1996 / Accepted: 18 October 1996     

Fagopyritol B1, O-α-D-galactopyranosyl-(1→2)-D-chiro-inositol, a galactosyl cyclitol in maturing buckwheat seeds associated with desiccation tolerance

O-α-D-Galactopyranosyl-(1→2)-D-chiro-inositol, herein named fagopyritol B1, was identified as a major soluble carbohydrate (40% of total) in buckwheat (Fagopyrum esculentum Moench, Polygonaceae) embryos. Analysis of hydrolysis products of purified compounds and of the crude extract led to the conclusion that buckwheat embryos have five α-galactosyl D-chiro-inositols: fagopyritol A1 and fagopyritol B1 (mono-galactosyl D-chiro-inositol isomers), fagopyritol A2 and fagopyritol B2 (di-galactosyl D-chiro-inositol isomers), and fagopyritol B3 (tri-galactosyl D-chiro-inositol). Other soluble carbohydrates analyzed by high-resolution gas chromatography included sucrose (42% of total), D-chiro-inositol, myo-inositol, galactinol, raffinose and stachyose (1% of total), but no reducing sugars. All fagopyritols were readily hydrolyzed by α-galactosidase (EC 3.2.1.22) from green coffee bean, demonstrating α-galactosyl linkage. Retention time of fagopyritol B1 was identical to the retention time of O-α-D-galactopyranosyl-(1→2)-D-chiro-inositol from soybean (Glycine max (L.) Merrill, Leguminosae), suggesting that the α-ga-lactosyl linkage is to the 2-position of D-chiro-inositol. Accumulation of fagopyritol B1 was associated with acquisition of desiccation tolerance during seed development and maturation in planta, and loss of fagopyritol B1 correlated with loss of desiccation tolerance during germination. Embryos of seeds grown at 18 °C, a condition that favors enhanced seed vigor and storability, had a sucrose-to-fagopyritol B1 ratio of 0.8 compared to a ratio of 2.46 for seeds grown at 25 °C. We propose that fagopyritol B1 facilitates desiccation tolerance and storability of buckwheat seeds. Received: 21 May 1997 / Accepted: 5 June 1997     

Influence of nitric oxide synthase inhibition on vasopressin and corticosterone secretion during water deprivation in rats

Nitric oxide (NO) is a short-lived radical that functions as a neurotransmitter in the central nervous system and plays a physiological role in the regulation of hypothalamic–pituitary–adrenal axis and vasopressinergic axis. In the present study, we aimed to investigate the interaction between the generation of NO and vasopressin (AVP) and corticosterone release after 3 days of water deprivation in rats. Animals were previously treated with intraperitoneal (i.p.) saline or l-nitro-arginine methyl ester (L-NAME) injection. l-NAME is a nonspecific inhibitor of nitric oxide synthases. In control rats given i.p. saline or l-NAME, hypothalamic, pituitary, and plasma AVP levels and plasma corticosterone did not change from baseline levels (p > 0.05). Three days of water deprivation increased significantly the corticosterone levels in plasma (p < 0.01) and AVP levels in hypothalamus and plasma (p < 0.01), but not in pituitary, which showed a significant decrease. These variations were concomitant with the elevation of nitrates/nitrates in plasma. l-NAME injection abolished significantly (p < 0.01) the elevation of plasma corticosterone and hypothalamic AVP levels induced by water deprivation. These findings showed that in water-deprived rats, nitric oxide synthase inhibition by l-NAME inhibits corticosterone and vasopressin release, suggesting a potent stimulatory role of NO.     

Probing binding site of bacteriochlorophyll a and carotenoid in the reconstituted LH1 complex from Rhodospirillum rubrum S1 by Stark spectroscopy

Stark spectroscopy is a powerful technique to investigate the electrostatic interactions between pigments as well as between the pigments and the proteins in photosynthetic pigment–protein complexes. In this study, Stark spectroscopy has been used to determine two nonlinear optical parameters (polarizability change Tr(Δα) and static dipole-moment change |Δμ| upon photoexcitation) of isolated and of reconstituted LH1 complexes from the purple photosynthetic bacterium, Rhodospirillum (Rs.) rubrum. The integral LH1 complex was prepared from Rs. rubrum S1, while the reconstituted complex was assembled by addition of purified carotenoid (all-trans-spirilloxanthin) to the monomeric subunit of LH1 from Rs. rubrum S1. The reconstituted LH1 complex has its Q_y absorption maximum at 878 nm. This is shifted to the blue by 3 nm in comparison to the isolated LH1 complex. The energy transfer efficiency from carotenoid to bacteriochlorophyll a (BChl a), which was determined by fluorescence excitation spectroscopy of the reconstituted LH1 complex, is increased to 40%, while the efficiency in the isolated LH1 complex is only 28%. Based on the differences in the values of Tr(Δα) and |Δμ|, between these two preparations, we can calculate the change in the electric field around the BChl a molecules in the two situations to be E _Δ ≈ 3.4 × 10⁵ [V/cm]. This change can explain the 3 nm wavelength shift of the Q_y absorption band in the reconstituted LH1 complex.