Study of Chemical Structure and of Photochemical Activity of Abiogenic Flavin Pigment

A product with molecular mass of 500–550 Da was isolated from a pigmented material formed by thermolysis (185°C) of a mixture of glutamic acid, glycine, and lysine (the optimal molar ratio of 8:3:1). After purification by chromatography the spectra of absorption and luminescence as well as IR- and PMR-spectra of the isolated pigment were studied. Based on the obtained data, the pigment was identified as a structural analogue of biological flavins: isoalloxazine heterocycle with two hydroxyl groups as well as a substitute of the amino acid nature. Like natural flavins, the abiogenic pigment photosensitized in solution both anaerobic and aerobic reactions of electron transfer from donors (ascorbate, Na₂-EDTA) to acceptors (redox- sensitive dyes, nicotinamide, Mo(IV) ), with the rate practically identical to that in the case of use of riboflavin. The ability of abiogenic flavin and riboflavin to photosensitize redox reactions was preserved after absorption of their molecules on particles of clay minerals (kaolinite, bentonite, celite) ; however, the absorption affected the rate of individual photochemical reactions.     

Biotic and Abiotic Drivers of Peatland Growth and Microtopography: A Model Demonstration

Peatlands are important carbon reserves in terrestrial ecosystems. The microtopography of a peatland area has a strong influence on its carbon balance, determining carbon fluxes at a range of spatial scales. These patterned surfaces are very sensitive to changing climatic conditions. There are open research questions concerning the stability, behaviour and transformation of these microstructures, and the implications of these changes for the long-term accumulation of organic matter in peatlands. A simple two-dimensional peat microtopographical model was developed, which accounts for the effects of microtopographical variations and a dynamic water table on competitive interactions between peat-forming plants. In a case study of a subarctic mire in northern Sweden, we examined the consequences of such interactions on peat accumulation patterns and the transformation of microtopographical structure. The simulations demonstrate plausible interactions between peatland growth, water table position and microtopography, consistent with many observational studies, including an observed peat age profile from the study area. Our model also suggests that peatlands could exhibit alternative compositional and structural dynamics depending on the initial topographical and climatic conditions, and plant characteristics. Our model approach represents a step towards improved representation of peatland vegetation dynamics and net carbon balance in Earth system models, allowing their potentially important implications for regional and global carbon balances and biogeochemical and biophysical feedbacks to the atmosphere to be explored and quantified.     

Photophosphorylation Associated with Photosystem II: II. Effects of Electron Donors, Catalyst Oxidation, and Electron Transport Inhibitors on Photosystem II Cyclic Photophosphorylation

Incubation of KCN-Hg-NH₂OH-inhibited spinach (Spinacia oleracea L.) chloroplasts with p-phenylenediamine for 10 minutes in the dark prior to illumination produced rates of photosystem II cyclic photophosphorylation up to 2-fold greater than the rates obtained without incubation. Partial oxidation of p-phenylenediaine with ferricyanide produced a similar stimulation of ATP synthesis; addition of dithiothreitol suppressed the stimulation observed with incubation. Addition of ferricyanide in amounts sufficient to oxidize completely p-phenylenediamine failed to inhibit completely photosystem II cyclic activity. This is due at least in part to the fact that the ferrocyanide produced by oxidation of p-phenylenediamine is itself a catalyst of photosystem II cyclic photophosphorylation. N,N,N′N′-Tetramethyl-p-phenylenediamine catalyzes photosystem II cyclic photophosphorylation at rates approaching those observed with p-phenylenediamine. The activities of both proton/electron and electron donor catalysts of the photosystem II cycle are inhibited by dibromothyoquinone and antimycin A. These findings are interpreted to indicate that photosystem II cyclic photophosphorylation requires the operation of endogenous membrane-bound electron carriers for optimal coupling of ATP synthesis to electron transport.     

The Effect of Light Intensity on Total Photophosphorylation and the ATP Level in Scenedesmus

The dependence of in vivo photophosphorylation on light intensity was studied in the unicellular green alga Scenedesmus obtusiusculus. By selective use of the inhibitor DCMU, phosphorylation in (I) the complete system, (II) the pseudocyclic system alone, and (III) the true cyclic system alone, were followed. When the total binding of phosphate was studied, all reaction types became light saturated in about the same manner. The effect of DCMU on the level of ATP varied according to light intensity. As for the specific systems of photophosphorylation, the following ATP data were found: (I) In the complete system the level of ATP decreases with light intensity. (II) Under pseudo-cyclic conditions light first increases and then decreases the ATP level. Under the atmospheric conditions used (i.e. CO₂-free nitrogen) this indicates a regulation between photophosphorylation and glycolysis, for which possible explanations are discussed. (III) In the true cyclic conditions light has little effect on the ATP level. The possibility is indicated that there is a structural difference between the non-cyclic (site 1) and the pseudocyclic (site 2) sites of photophosphorylation on the one hand and the true cyclic site (3) on the other.     

Clotrimazole对菠菜叶绿体光合磷酸化和电子传递的抑制作用

10μmol/的clotrimazole不仅抑制光合磷酸化活力,而且抑制各种类型的电子传递,是一个典型的电子传递抑制剂。经过它对叶绿体放氧,荧光和毫秒延迟发光影响的比较研究表明:clotri—mazole在光合电子传递链上的作用部位在Q与PQ之间,即与DGMU的作用部位相同或相近。     

Photophosphorylation after chilling in the light : effects on membrane energization and coupling factor activity

The response of in situ photophosphorylation in attached cucumber (Cucumis sativus L. cv Ashley) leaves to chilling under strong illumination was investigated. A single-beam kinetic spectrophotometer fitted with a clamp-on, whole leaf cuvette was used to measure the flash-induced electrochromic absorbance change at 518 minus 540 nanometers (ΔA_518−540) in attached leaves. The relaxation kinetics of the electric field-indicating ΔA_518−540 measures the rate of depolarization of the thylakoid membrane. Since this depolarization process is normally dominated by proton efflux through the coupling factor during ATP synthesis, this technique can be used, in conjuction with careful controls, as a monitor of in situ ATP formation competence. Whole, attached leaves were chilled at 5°C and 1000 microeinsteins per square meter per second for up to 6 hours then rewarmed in the dark at room temperature for 30 minutes and 100% relative humidity. Leaf water potential, chlorophyll content, and the effective optical pathlength for the absorption measurements were not affected by the treatment. Light- and CO₂-saturated leaf disc oxygen evolution and the quantum efficiency of photosynthesis were inhibited by approximately 50% after 3 hours of light chilling and by approximately 75% after 6 hours. Despite the large inhibition to net photosynthesis, the measurements of ΔA_518−540 relaxation kinetics showed photophosphorylation to be largely unaffected by the chilling and light exposure. The amplitude of the ΔA_518-540 measures the degree of energization of the photosynthetic membranes and was reduced significantly by chilling in the light. The cause of the decreased energization was traced to impaired turnover of photosystem II. Our measurements showed that the chilling of whole leaves in the light caused neither an uncoupling of photophosphorylation from photosynthetic electron transport nor any irreversible inhibition of the chloroplast coupling factor in situ. The sizeable inhibition in net photosynthesis observed after chilling in the light cannot, therefore, be attributed to any direct effect on photophosphorylation competence.     

Flavin containing monooxygenase 3 exerts broad effects on glucose and lipid metabolism and atherosclerosis

We performed silencing and overexpression studies of flavin containing monooxygenase (FMO) 3 in hyperlipidemic mouse models to examine its effects on trimethylamine N-oxide (TMAO) levels and atherosclerosis. Knockdown of hepatic FMO3 in LDL receptor knockout mice using an antisense oligonucleotide resulted in decreased circulating TMAO levels and atherosclerosis. Surprisingly, we also observed significant decreases in hepatic lipids and in levels of plasma lipids, ketone bodies, glucose, and insulin. FMO3 overexpression in transgenic mice, on the other hand, increased hepatic and plasma lipids. Global gene expression analyses suggested that these effects of FMO3 on lipogenesis and gluconeogenesis may be mediated through the PPARα and Kruppel-like factor 15 pathways. In vivo and in vitro results were consistent with the concept that the effects were mediated directly by FMO3 rather than trimethylamine/TMAO; in particular, overexpression of FMO3 in the human hepatoma cell line, Hep3B, resulted in significantly increased glucose secretion and lipogenesis. Our results indicate a major role for FMO3 in modulating glucose and lipid homeostasis in vivo, and they suggest that pharmacologic inhibition of FMO3 to reduce TMAO levels would be confounded by metabolic interactions.     

基于图像RGB特征值的甘薯色素与肉色关系初步探讨

为明确甘薯色素、干率与肉色的关系,给图像RGB特征值评估甘薯色素含量提供依据,测定了甘薯240份品系的胡萝卜素含量及234份品系的花青素含量、干率和薯肉RGB颜色特征值。结果表明,甘薯胡萝卜素含量与RGB值的相关系数r=-0.913,偏相关系数为-0.872,花青素含量与RGB值的相关系数r=-0.838,偏相关系数为-0.836,说明甘薯色素含量与肉色是高度正相关的,是肉色的决定因子,但胡萝卜素与肉色关系更紧密。干率与胡萝卜素RGB值的相关系数r=0.597,偏相关系数为0.273,干率与花青素RGB值的相关系数r=-0.273,偏相关系数为0.255,说明干率与对肉色有极明显的负面影响,但是在RGB值≥200的低胡萝卜素(约含量3 mg/100 g·FW以下)群体中,干率与RGB值的偏相关系数为-0.0066(P=0.9426),干率对低胡萝卜素含量品系的肉色没有影响。采用R值、G值、B值、干率的二次多项式回归模型,RGB值≥200的低胡萝卜素群体、RGB值200的较高或高胡萝卜素群体和花青素群体的拟合方程的复相关系数R分别为0.975、0.982和0.937,说明拟合值与实测值关系十分密切。对胡萝卜素含量高于3 mg/100 g·FW的品种,拟合值能达到约90%的精确度,对胡萝卜素含量低于3 mg/100g·FW的品种,也能达到约83%的精确度,对花青素品种能达到约86%的精确度。因此,图像RGB特征值法不仅能够很好地反映甘薯品种间的色素差异,还能较精确地估测甘薯色素含量,可为甘薯早代育种的大批量样品提供便捷、客观的色素含量评估方法。     

Participations of Iron and Flavin Adenine Dinucleotide on the Enzymatic Hydroxylation of p-Hydroxybenzoate.

The effects of oxygen and carbon dioxide in inosine fermentation were investigated from the industrial viewpoint. Oxygen supply at the rate of more than 5 × 10^-7 mole/ml-min was indispensable for maintaining the high productivity of inosine in jar fermentors as well as in shaking flasks. Oxygen deficiency due to insufficient oxygen supply, on the other hand, resulted in the inhibition of inosine production, even though glucose added to the medium was entirely assimilated. In addition to sufficient oxygen supply ventilation was also indispensable since an increased tension of carbon dioxide reduced the inosine-producing capability of the cells.     

Effect of Hill Reaction Inhibitors on the Photoreduction of Ferricyanide and Cyclic Photophosphorylation by Spinach Chloroplasts

Some derivatives of phenylurea, N-phenylcarbamate, s-triazine and acylanilide inhibited the cyclic photophosphorylation of spinach chloroplasts catalyzed by phenazine methosulfate and accelerated the photosystem I-dependent electron flow estimated as the disproportionation of diphenylcarbazone. Acceleration was slightly stimulated by the simultaneous addition of methylamine. Thus, these Hill reaction inhibitors act as uncouplers of cyclic photophosphorylation as does methylamine. The inhibiting activities of the chemicals on the photoreduction of ferricyanide and on photophosphorylation had a parabolic relation to the partition coefficient in the octanol-water system of the chemicals.     

Effects of Aluminium on Pigments and Pigment-Protein Complexes of Soybean

The effect of aluminium (0.5 –1.0 mM) on contents of phosphorus, pigments, and pigment-protein complexes was studied in soybean (Glycine max Merril.) grown in different nutrient medium with and without P. Increased Al concentrations led to the decrease in the contents of chlorophylls (Chl) a and b, and carotenoids (Car) in soybean leaves, but Chl a/b ratio did not vary significantly. In long-term experiments, P ameliorates the negative effects of Al.     

Promotive Effect of Low Concentrations of NaHSO3 on Photophosphorylation and Photosynthesis in Phosphoenolpyruvate Carboxylase Transgenic Rice Leaves

Spraying a 1-2 mmol/L solution of NaHSO3 on the leaves of wild-type rice (Oryza sativa L.)Kitaake (WT), phosphoenolpyruvate carboxylase (PEPC) transgenic (PC) rice and PEPC phosphate dikinase (PPDK) transgenic rice (PC PK), in which the germplasm was transformed with wild-type Kitaake as the gene receptor, resulted in an enhancement of the net photosynthetic rate by 23.0%, 28.8%, and 34.4%,respectively, for more than 3 d. It was also observed that NaHSO3 application caused an increase in the ATP content in leaves. Spraying PMS (a cofactor catalysing the photophosphorylation cycle) and NaHSO3 separately or together on leaves resulted in an increase in photosynthesis with all treatments. There was no additional effect on photosynthetic rate when the mixture was applied, suggesting that the mechanism by which NaHSO3 promotes photosynthesis is similar to the mechanism by which PMS acts and that both of compounds enhanced the supply of ATP. After spraying a solution of NaHSO3 on leaves, compared with the WT Kitaake rice, a greater enhancement of net photosynthetic rate was observed in PEPC transgenic (PC) and PEPC PPDK transgenic (PC PK) rice, with the greatest increase being observed in the latter group. Therefore ATP supply may become the limiting factor that concentrates CO2 in rice leaves transformed with an exogenous PEPC gene and exogenous PEPC PPDK genes.     

水曲柳FmJAZ1基因在非生物胁迫中的响应模式和激素诱导表达分析

克隆FmJAZ1基因,明确其在低温和NaCl胁迫中的响应模式和激素诱导下的转录表达特性。通过基因克隆的方法得到水曲柳中的FmJAZ1基因,利用生物信息学软件对所得到的序列进行分析并构建系统进化树,对水曲柳FmJAZ1基因进行了时空表达特异性的分析,对根、茎、叶、芽、雄花、雌花、种子等7个部位以及在5-9月5个月份分别取样,对水曲柳进行低温(4℃)和盐胁迫(200 mmol/L NaCl)2种非生物胁迫处理以及脱落酸(ABA)、赤霉素(GA3)、生长素(IAA)、茉莉酸(JA)、水杨酸(SA)等激素信号诱导处理,然后对试验材料进行荧光定量分析。克隆出全长为684 bp的核苷酸序列。生物信息学软件分析得到JZA1基因具有完整的开放阅读框,编码227个氨基酸,JAZ1蛋白不含有信号肽,不属于跨膜蛋白,为不稳定亲水性蛋白。时空表达结果显示,FmJAZ1基因在茎中表达量最高,且在8月份表达量最高;非生物胁迫结果表明低温处理后FmJAZ1在6h、24h表达量较高;而NaCl处理后,在24 h表达量较高,且该基因响应低温胁迫较NaCl胁迫迅速;激素信号诱导结果显示,处理后不同时间,基因表达量变化较为明显,其中GA3处理后3h最为明显,为对照组的77.3倍,分析了FmJAZ1基因在低温、NaCl胁迫和激素诱导下的表达模式。FmJAZ1基因充分响应了逆境胁迫和激素信号诱导,通过蛋白和基因层面对逆境进行响应,JAZ蛋白在其中起到了桥梁的作用,并扮演了重要的角色。     

大型真菌色素的研究现状与应用前景

真菌色素是一类重要的化合物,其化学结构多样,生物活性显著并往往兼有营养和保健功能。近年来,对大型真菌色素的研究开发已成为一项热门领域,对真菌资源综合利用有着重要的意义。作者对大型真菌色素的类型、稳定性及其应用前景方面进行了简要综述。     

黑果枸杞色素的提取和精制工艺研究

本文采用正交实验法对黑果枸杞色素的提取和精制工艺进行了研究。结果表明,黑果枸杞色素的最佳提取条件为:以pH 3.0的80%乙醇作浸提剂,提取温度50℃,提取时间3 h,固液配比1:40;用X-5大孔吸附树脂对色素进行精制,以树脂柱径高比1:15、流速3 mL/minp、H 3.0、色素液浓度1 g/L为最佳吸附条件,色素的吸附量可达0.03715 g/mL湿树脂体积;而以95%乙醇做洗脱液,在pH 2.0、流速5 mL/min、3倍于柱床体积的洗脱液条件下解吸附效果最佳,色素回收率达到97.78%;制取的色素产品外观呈紫红色,色价为36.7。     

Effects of Nutrient Limitation on Pigments in Thalassiosira weissflogii and Prorocentrum donghaiense

The response of Prorocentrum donghaiense and Thalassiosira weissfiogii pigments under nitrate （N） and phosphate （P） limitation were studied using HPLC and in vivo fluorescence protocols in batch cultures. For P. donghaiense, the pigment ratio was kept stable under different nutrient conditions from the results of HPLC. For T. weissflogii, there was a lower ratio of chlorophyllide to Chl a during the exponential phase, but the reverse during the stationary phase. Different members of the phytoplankton had different pigments response mechanisms under nutrient limitation. From the results of in vivo fluorescence, the ratio of peridinin to Chl a for P. donghaiense increased in nutrient-free culture, while it was kept stable for nutrient-limited cultures during the exponential phase. For T. weissflogii, the ratio of fucoxanthin to Chl a for each culture increased during the exponential phase, but the ratio under N limitation was apparently lower than that for P limitation during the stationary phase. The results indicate that both pigment ratios from HPLC and in vivo fluorescence of To weissflogii were changed greatly under different nutrient conditions, which suggests that both ratios could be used as indicators of algal physiological status in different nutrient conditions.