共查询到20条相似文献,搜索用时 367 毫秒
1.
M. Sang X. -C. Qin W. -D. Wang J. Xie X. -B. Chen K. B. Wang J. -P. Zhang L. -B. Li T. Y. Kuang 《Photosynthetica》2011,49(1):48-54
The generation of superoxide anion radical (O2
·−) in the cytochrome b
6
f complex (Cyt b
6
f) of spinach under high-light illumination was studied using electron paramagnetic resonance spectroscopy. The generation
of O2
·− was lost in the absence of molecular oxygen. It was also suppressed in the presence of NaN3 and could be scavenged by extraneous antioxidants such as ascorbate, β-carotene, and glutathione. The results also indicate that O2
·−, which is produced under high-light illumination of the Cyt b
6
f from spinach, might be generated from a reaction involing 1O2, and the Rieske Fe-S protein could serve as the electron donor in the O2
·− production. The mechanism of photoprotection of the Cyt b
6
f complex by antioxidants is discussed. 相似文献
2.
Rau U Kuenz A Wray V Nimtz M Wrenger J Cicek H 《Applied microbiology and biotechnology》2009,81(5):827-837
Trametes versicolor ATCC 200801 secretes 4.1 g L−1 of exopolysaccharide (EPS) when synthetic minimal medium and low-shear bioreactor cultivation technique are used. Structural
and compositional analyses by thin layer chromatography, gas chromatography–mass spectrometry, electrospray ionization tandem
mass spectrometry, and nuclear magnetic resonance spectroscopy yielded predominantly glucose and small amounts of galactose,
mannose, arabinose, and xylose. The main EPS is composed of β-1,3/β-1,6-linked d-glucose molecules which is identical with Schizophyllan but does not possess a triple helical arrangement as secondary structure.
Two molar mass fractions were detected by size exclusion chromatography yielding weight-average molecular weights of 4,100
and 2.6 kDa. Protein content varies between 2–3.6% (w/w). The exopolysaccharide is different in the nature of the glycosidic linkage, composition of monosaccharides, protein content,
and weight-average molecular weight compared to the well-known polysaccharopeptide (PSP) and polysaccharopeptide Krestin (PSK). 相似文献
3.
A slow, long range electron transfer (SLRET) in human serum albumin (HSA) is observed from an intact tyrosine (Tyr) residue
to the neutral tryptophan (Trp) radical (Trp·) generated in pulse radiolysis. This radical is formed, at neutral pH, through
oxidation with Br2·− radical anions of the single Trp 214 present. The SLRET rate constant of ~0.2 s−1 determined is independent of HSA concentration and radiation dose, consistent with an intra-molecular process. This is the
slowest rate constant so far reported for an intra-molecular LRET. In sharp contrast with the LRET reported for other proteins,
the SLRET observed here is insensitive to oxygen, suggesting that the oxidized Trp is inaccessible to—or do not react with
radiolytically generated O2·−. In N2O-saturated solutions, the SLRET is inhibited by Cu2+ ions bound to the His 3 residue of the N-terminal group of HSA but it is partially restored in O2-saturated solutions. 相似文献
4.
Jun Liu Jianguang Luo Hong Ye Yi Sun Zhaoxin Lu Xiaoxiong Zeng 《Carbohydrate polymers》2010,79(1):206-213
In this study, response surface methodology was employed to optimize the medium compositions for the production of exopolysaccharides (EPS) from endophytic bacterium Paenibacillus polymyxa EJS-3. Firstly, fractional factorial design was applied to evaluate the effects of different components in the medium. It was found that sucrose, yeast extract and CaCl2 influenced significantly the production of EPS. Then, steepest ascent method and central composite design were used to optimize the concentrations of the three variables. As results, the optimal medium compositions were determined as following (g/L): sucrose 188.2, yeast extract 25.8, K2HPO4 5 and CaCl2 0.34, with a corresponding yield of 35.26 g/L. In addition, both polysaccharide fractions (EPS-1 and EPS-2) from crude EPS were mainly composed of (2 → 6)-linked β-d-fructofuranosyl residues backbone with (2 → 1)-linked branches based on their structural characterization by FT-IR spectroscopy, methylation analysis and 13C NMR spectroscopy. 相似文献
5.
Elin Säwén Eine Huttunen Xue Zhang Zhennai Yang Göran Widmalm 《Journal of biomolecular NMR》2010,47(2):125-134
The use of lactic acid bacteria in fermentation of milk results in favorable physical and rheological properties due to in
situ exopolysaccharide (EPS) production. The EPS from S. thermophilus ST1 produces highly viscous aqueous solutions and its structure has been investigated by NMR spectroscopy. Notably, all aspects
of the elucidation of its primary structure including component analysis and absolute configuration of the constituent monosaccharides
were carried out by NMR spectroscopy. An array of techniques was utilized including, inter alia, PANSY and NOESY-HSQC TILT
experiments. The EPS is composed of hexasaccharide repeating units with the following structure: → 3)[α-d-Glcp-(1 → 4)]-β-d-Galp-(1 → 4)-β-d-Glcp-(1 → 4)[β-d-Galf-(1 → 6)]-β-d-Glcp-(1 → 6)-β-d-Glcp-(1 →, in which the residues in square brackets are terminal groups substituting backbone sugar residues that consequently
are branch-points in the repeating unit of the polymer. Thus, the EPS consists of a backbone of four sugar residues with two
terminal sugar residues making up two side-chains of the repeating unit. The molecular mass of the polymer was determined
using translational diffusion experiments which resulted in Mw = 62 kDa, corresponding to 64 repeating units in the EPS. 相似文献
6.
The influence of ultraviolet-B radiation on the growth, pigment production and chlorophyll fluorescence of Norway spruce seedlings 总被引:3,自引:0,他引:3
Norway spruce (Picea abies (L.)Karst.) from seven seed sources was grown in a greenhouse with 8.3 and 14.7 kJ·m−2·d−1 m UV-BBE (biologically effective UV-B: 280–320 nm) irradiation, and with no supplemental irradiation as control. The seedlings total
biomass (dry weight) and shoot growth decreased with high UV-B treatment but spruce from low elevation seed sources were more
affected. The seedlings grown at the highest UV-B irradiance (14.7 kJ·m−2·d−1) showed from 5 to 38% inhibition of total biomass and 15 to 70 % shoot growth inhibition. Norway spruce populations from
higher altitude seed sources manifested greater tolerance to UV-B radiation compared to plants from low altitudes. Changes
in phospholipids and protective pigments were also determined. The plants grown at the lower UV-B irradiance (8.3 kJ·m−2·d−1) showed greater ability to concentrations UV-B-absorbing pigments then control plants. Chlorophyll a fluorescence parameter
Rfd, (Rfd=(Fm-Fs)/Fs) showed a significant decrease in needles of UV-B treated plants and this correlated with the altitude of seed source. Exposure
to UV-B affect levels of the ratio of variable to maximum fluorescence (Fv/Fm). Results from this study suggest that the response to increased levels of UV-B radiation is depended upon the ecotypic differentiation
of Norway spruce and involved changes in metabolites in plant tissues. 相似文献
7.
Beal AM 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2000,170(8):589-599
Intracarotid infusions of noradrenaline (0.15 nmol · kg−1 · min−1) either alone or accompanied by phentolamine (1.5 nmol · kg−1 · min−1) caused similar-sized increases in salivary protein, magnesium and bicarbonate, and decreases in osmolality, sodium, potassium
and chloride whereas intravenous noradrenaline stimulated much smaller responses. Concurrent infusions of the β1-antagonist, CGP20712A, blocked these noradrenaline-induced changes in salivary composition more effectively than equimolar
infusions of the β2-antagonist, ICI118551, thereby confirming the presence of β1-adrenoceptors. Intracarotid infusion of salbutamol at 0.15, 0.3 and 1.5 nmol · kg−1 · min−1 caused increasing but qualitatively similar changes in salivary composition, sodium excepted, to intracarotid noradrenaline
with 0.3 nmol being most similar quantitatively. Intravenous infusion of salbutamol caused larger changes in salivary composition
than equimolar intravenous noradrenaline thereby indicating that the response to salbutamol may, in part, be mediated by reflex
increases in general sympathetic tone triggered by lowered blood pressure. Eliminating this hypotensive effect by concurrent
intravenous and intracarotid infusions of β1-(CGP or atenolol) and β2-(ICI118551) antagonists with intracarotid salbutamol showed that ICI118551 was more potent than the β1-antagonists thereby demonstrating the presence of β2-receptors. It was concluded that the kangaroo mandibular has functional β1- and β2-adrenoceptor subtypes in both endpieces and excurrent ducts and that the duct system has two populations of cells, each expressing
one receptor subtype.
Accepted: 26 July 2000 相似文献
8.
Chaoning Liang Yanfen Xue Marco Fioroni Francisco Rodríguez-Ropero Cheng Zhou Ulrich Schwaneberg Yanhe Ma 《Applied microbiology and biotechnology》2011,89(2):315-326
A β-1,4-endoglucanase (Cel5A) was cloned from the genomic DNA of saccharolytic thermophilic eubacterium Thermoanaerobacter tengcongensis MB4 and functionally expressed in Escherichia coli. Substrate specificity analysis revealed that Cel5A cleaves specifically the β-1,4-glycosidic linkage in cellulose with high
activity (294 U mg−1; carboxymethyl cellulose sodium (CMC)). On CMC, kinetics of Cel5A was determined (K
m 1.39 ± 0.12 g l−1; k
cat/K
m 1.41 ± 0.13 g−1 s−1). Cel5A displays an activity optimum between 75 and 80 °C. Residues Glu187 and Glu289 were identified as key catalytic amino
acids by sequence alignment. Interestingly, derived from a non-halophilic bacterium, Cel5A exhibits high residual activities
in molar concentration of NaCl (3 M, 49.3%) and KCl (4 M, 48.6%). In 1 M NaCl, 82% of Cel5A activity is retained after 24
h incubation. Molecular Dynamics studies performed at 0 and 3 M NaCl, correlate the Cel5A stability to the formation of R-COO−···Na+ ···−OOC-R salt bridges within the Cel5A tertiary structure, while activity possibly relates to the number of Na+ ions trapped into the negatively charged active site, involving a competition mechanism between substrate and Na+. Additionally, Cel5A is remarkably resistant in ionic liquids 1-butyl-3-methyllimidazolium chloride (1 M, 54.4%) and 1-allyl-3-methylimidazolium
chloride (1 M, 65.1%) which are promising solvents for cellulose degradation and making Cel5A an attractive candidate for
industrial applications. 相似文献
9.
Aims: To study the optimization of submerged culture conditions for exopolysaccharide (EPS) production by Armillaria mellea in shake‐flask cultures and also to evaluate the performance of an optimized culture medium in a 5‐l stirred tank fermenter. Methods and Results: Shake flask cultures for EPS optimal nutritional production contained having the following composition (in g l?1): glucose 40, yeast extract 3, KH2PO4 4 and MgSO4 2 at an optimal temperature of 22°C and an initial of pH 4·0. The optimal culture medium was then cultivated in a 5‐l stirred tank fermenter at 1 vvm (volume of aeration per volume of bioreactor per min) aeration rate, 150 rev min?1 agitation speed, controlled pH 4·0 and 22°C. In the optimal culture medium, the maximum EPS production in a 5‐l stirred tank fermenter was 588 mg l?1, c. twice as great as that in the basal medium. The maximum productivity for EPS (Qp) and product yield (YP/S) were 42·02 mg l?1 d?1 and 26·89 mg g?1, respectively. Conclusions: The optimal culture conditions we proposed in this study enhanced the EPS production of A. mellea from submerged cultures. Significance and Impact of the Study: The optimal culturing conditions we have found will be a suitable starting point for a scale‐up of the fermentation process, helping to develop the production of related medicines and health foods from A. mellea. 相似文献
10.
Characterization of<Emphasis Type="Italic"> Aureobasidium pullulans</Emphasis> isolated from airborne spores in Thailand 总被引:1,自引:0,他引:1
Punnapayak H Sudhadham M Prasongsuk S Pichayangkura S 《Journal of industrial microbiology & biotechnology》2003,30(2):89-94
Isolates from air in several locations in Thailand were identified as Aureobasidium pullulans PR with dark pigmentation (Loei province), A. pullulans SU with an unusual conidial apparatus (Chiangmai province), and A. pullulans CU with burgundy-red pigmentation (from a shady area in Bangkok). The internal transcribed spacer sequences of the rDNA of A. pullulans SU and A. pullulans CU confirmed that they were A. pullulans. Both A. pullulans CU and A. pullulans PR preferred 30 °C and pH 7.5 for exopolysaccharide (EPS) production, while A. pullulans SU preferred 25 °C and pH 6.5. All three isolates preferred glucose over sucrose and (NH4)2SO4 over peptone for EPS production. Under optimal conditions, A. pullulans PR produced EPS yields of up to 0.225 g g−1, followed by A. pullulans CU (0.185 g g−1) and A. pullulans SU (0.158 g g−1). Amylase activities were detected during the course of EPS production but gradually decreased as the EPS yields increased.
IR spectra suggest that the EPS from these isolates was pullulan. EPS from the three isolates were partially sensitive to
pullulanase.
Electronic Publication 相似文献
11.
Yimin Shi Wenfeng Wang Jiuhong Kang Yanping Shi Zhongjian Jia Ying Wang Baoning Su Side Yao Nianyun Lin Rongliang Zheng 《中国科学C辑(英文版)》1999,42(4):420-426
The reaction of hydroxyl radical with 1 phenylpropanoid glycoside (PPG), cistanoside C, and its 3 derivatives: 1-0-β-D-2-(p-hydroxyphenyl)-ethanyl-glucose, 6-O-(E)-femloyl-glucose and 6-O-(E)-p-hydroxy-cinnarnoylglucose isolated from folk medicinal herbs was investigated by pulse radiolysis technique respectively. The reaction rate constants were determined by analysis of built-up trace of absorption at λmax of specific transient absorption spectra of PPG and its derivatives upon attacking · OH. All four compounds react with · OH at close to diffusion controlled rate (1. 03 × 109-19.139 × 109 L · mol−1 · s−1), suggesting that they are effective · OH scavengers. The results demonstrated that the numbers of phenolic hydroxyl groups of PPG and its derivatives are directly related to their scavenging activities. By comparing the reaction rates of · OH with 1-O-β-D-2-(p-hydroxyphenyl)-ethanyl-glucose, 6-O-(E)-feruloyl-glucose or 6-O-(E)-p-hydroxy-cinnomoyl-glucose, it is evident that the phenylethyl group is more impofiant than phenylacryloyl group for scavenging · OH. 相似文献
12.
Marina Naoumkina Ivone Torres-Jerez Stacy Allen Ji He Patrick X Zhao Richard A Dixon Gregory D May 《BMC plant biology》2007,7(1):62
Background
Guar, Cyamopsis tetragonoloba (L.) Taub, is a member of the Leguminosae (Fabaceae) family and is economically the most important of the four species in the genus. The endosperm of guar seed is a rich source of mucilage or gum, which forms a viscous gel in cold water, and is used as an emulsifier, thickener and stabilizer in a wide range of foods and industrial applications. Guar gum is a galactomannan, consisting of a linear (1→4)-β-linked D-mannan backbone with single-unit, (1→6)-linked, α-D-galactopyranosyl side chains. To better understand regulation of guar seed development and galactomannan metabolism we created cDNA libraries and a resulting EST dataset from different developmental stages of guar seeds. 相似文献13.
Hwang HS Lee SH Baek YM Kim SW Jeong YK Yun JW 《Applied microbiology and biotechnology》2008,78(3):419-429
In the present study, optimum culture conditions for the production of extracellular polysaccharides (EPS) in submerged culture
of an edible mushroom, Laetiporus sulphureus var. miniatus and their stimulatory effects on insulinoma cell (RINm5F) proliferation and insulin secretion were investigated. The maximum
mycelial growth (4.1 g l−1) and EPS production (0.6 g l−1) in submerged flask culture were achieved in a medium containing 30 g l−1 maltose, 2 g l−1 soy peptone, and 2 mM MnSO4·5H2O at an initial pH 2.0 and temperature 25°C. In the stirred-tank fermenter under optimized medium, the concentrations of mycelial
biomass and EPS reached a maximum level of 8.1 and 3.9 g l−1, respectively. Interestingly, supplementation of deep sea water (DSW) into the culture medium significantly increased both
mycelial biomass and EPS production by 4- and 6.7-fold at 70% (v/v) DSW medium, respectively. The EPS were proved to be glucose-rich polysaccharides and were able to increase proliferation
and insulin secretary function of rat insulinoma RINm5F cells, in a dose-dependent manner. In addition, EPS also strikingly
reduced the streptozotocin-induced apoptosis in RINm5F cells indicating the mode of the cytoprotective role of EPS on RINm5F
cells. 相似文献
14.
The marine cyanobacterium Phormidium sp. strain C86 changes the phycobilisome type depending on light quality. Red-light-adapted cells contained hemidiscoidal
phycobilisomes with a photosystem II:phycobilisome ratio of 2.2, while green-light-adapted cells exhibited hemiellipsoidal
phycobilisomes with a photosystem II:phycobilisome ratio of 4.4, as determined by a combined analysis of freeze-fractured
thylakoid membranes and ultrathin sections and by photochemical determinations of photosystems and phycobilisomes. Core complexes
of phycobilisomes of red- and green-light-adapted cells were isolated by affinity chromatography and were subsequently separated
into two allophycocyanin-containing fractions. The high-molecular-weight fraction, with a sedimentation coefficient of 24
S and a calculated mol. wt. of 860,000, contained complexes of the quaternary structure (αAP
9βAP
8β19.5AP)2· (LCM)2 and tricylindrical shape, previously designated APCM. This fraction was similar in size in red- and green-light-adapted cells; however, differences were detected in the low-molecular-weight
allophycocyanin fraction containing the "trimeric" complexes with a sedimentation coefficient of 6 S. As shown by comparison
of spectral and stoichiometric data of intact phycobilisomes and isolated core complexes, the amount of the αAPB-containing core complex (αAP
2αAPBβAP
3) · LC
10 was greater in core fractions of green-light phycobilisomes, whereas the amount of the core complexes (αAP
3βAP
3) · LC
10, designated AP · LC
10, was higher in cores of red-light phycobilisomes. Phormidium sp. is the first organism examined that exhibits a new type of complementary chromatic adaptation by altering the composition
of the phycobilisome core and the number and composition of peripheral rods and by changing the ratio of photosystem II to
phycobilisomes. A model summarizing the structural consequences of the results is presented.
Received: 5 December 1995 / Accepted: 10 April 1995 相似文献
15.
L. G. Yarullina N. B. Troshina E. A. Cherepanova E. A. Zaikina I. V. Maksimov 《Applied Biochemistry and Microbiology》2011,47(5):549-555
Influence of mediators of the signal systems of salicylic (SA) and jasmonic (JA) acids and their mixture on reactive oxygen
species’ (ROS) (superoxide radical and O2·− H2O2) generation and activity of oxidoreductases (oxalate oxidase, peroxidase and catalase) in leaves of wheat Triticum aestivum L. infected by Septoria leaf blotch pathogen Septoria nodorum Berk has been studied. Presowing treatment of seeds by SA and JA decreased the development rate of fungus on wheat leaves.
SA provided earlier inductive effect on production of O2·− and H2O2 compared with JA. The protective effect of the salicylic and jasmonic acids against Septoria leaf blotch pathogen was caused
by activation of oxalate oxidase, induction of anion and cation peroxidases, and decrease of catalase activity. Ability of
compounds to stimulate ROS in the plant tissues can be used as criteria for evaluation of immune-modulating activity of new
substances for protection of the plants. 相似文献
16.
The reaction of hydroxyl radical with 1 phenylpropanoid glycoside ( PPG), cistanoside C, and its 3 derivatives: 1-O-β-D-2-(p-hydroxyphenyl)-ethanyl-glucose, 6-O-(E)-feruloyl-glucose and 6-O-(E)-p-hydroxy-cinnamoylglucose isolated from folk medicinal herbs was investigated by pulse radiolysis technique respectively. The reaction rate constants were determined by analysis of built-up trace of absorption at λ_(max) of specific transient absorption spectra of PPG and its derivatives upon attacking·OH. All four compounds react with·OH at close to diffusion controlled rate (1.03×10~9—19.139×10~9 L·mol~(-1)·s~(-1)), suggesting that they are effective·OH scavengers. The results demonstrated that the numbers of phenolic hydroxyl groups of PPG and its derivatives are directly related to their scavenging activities. By comparing the reaction rates of·OH with 1-O-β-D-2-(p-hydroxyphenyl)-ethanyl-glucose, 6-O-(E)-feruloyl-glueose or 6-O-(E)-p-hydroxy-cinnomoyl-glucose, it is evident that the phenylethyl g 相似文献
17.
The effects of temperature (20, 24 and 28 °C) and irradiance (15 and 40 μmol photon m−2 s−1) on the nitrate and ammonium uptake rates of the subtropical red alga, Laurencia brongniartii, were investigated to prepare for tank cultivation. Nitrate uptake followed saturation kinetics and was faster at higher
irradiances and temperatures. In contrast, ammonium uptake was linear over the experimental range and was not affected by
an increase in temperature. A parameter, β, was calculated to compare substrate uptake rates of nitrate along the linear portion
of the uptake curve with that of ammonium. For nitrate, β was lower at low irradiance and higher at high irradiance (β = 0.007
± 0.003 and 0.030 ± 0.002 [μmol N L−1 (μmol N gww−1 d−)−1], respectively). However, β was 0.023 ± 0.002 and 0.034 ± 0.002 [μmol N L−1 (μmol N gww−1 d−1)−1] for ammonium, suggesting a preference for ammonium over nitrate. 相似文献
18.
Yu Qiu Hai Niu Wen Huang Yang He Xiao-Hua Wu 《Biotechnology and Bioprocess Engineering》2011,16(5):858-866
A tannase with a molecular mass of 72 kDa was obtained from Penicillium herquei isolated from valonia acorns following fermentation in a 5 L bioreactor. This tannase showed optimum activity at pH 6.0 and
30°C. The enzyme was inhibited by Fe3+, Zn2+, dithiothrietol (DTT), β-mercaptoethanol, formaldehyde, and ethanol, and induced by K+, Mn2+, Tween 80, and Triton X-100. The Michaelis constant (K
m) and the second-order constant (k
cat/K
m) values of the tannase for propyl gallate (PG) were 0.62 mM and 174.1 mM/sec. The circular dichroism (CD) spectra indicated
that the secondary structure of the tannase contained 14% α helix, 32.4% anti-parallel β-sheet, 4.8% β-sheet, 18.8% β-turn,
and 30% random coil. Native tannase in ultrapure water manifested as spherical nano-particle aggregates with diameters ranging
from 50 to 300 nm determined by atomic force microscopy (AFM). 相似文献
19.
20.
Protective effects of prostaglandins in the isolated gastric mucosa of the eel, Anguilla anguilla 总被引:1,自引:0,他引:1
Faggio C Denaro MG Lionetto MG Trischitta F 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2000,170(5-6):357-363
The protective effect of endogenous prostaglandins on the fish gastric mucosa was evaluated by studying the effect of indomethacin
and aspirin, known cyclooxigenase inhibitors, on the mucosal ulceration in the isolated gastric sacs of Anguilla anguilla. Gastric sacs devoid of muscle layers were incubated in the presence of indomethacin (10−4 mol · l−1) or aspirin (10−4 mol · l−1) in different experimental conditions. Both the anti-inflammatory drugs produced ulcers, but the effects were more severe
in the presence of histamine and in the absence of HCO3
− in the incubation bath. The effects of prostaglandin E2 (PGE2) on acid secretion rate (JH) and on alkaline secretion rate (JOH) were evaluated (with the aid of the pH stat method) in isolated gastric mucosa mounted in Ussing chambers. We found that
PGE2 (10−8–10−5 mol · l−1) increased JH in a dose-dependent manner. In tissues pretreated with luminal omeprazole (10−4 mol · l−1), PGE2 stimulated gastric alkaline secretion. It was nullified by serosal removal of HCO3
− or Na+ and by serosal ouabain (10−4 mol · l−1). These results suggested that prostaglandins also exert their protective effects in fish gastric mucosa. This protection
seems partially due to a stimulation of exogenous HCO3
− transport from the serosal to the mucosal side. It is likely that this transport is an active transcellular mechanism coupled
to Na+ transport.
Accepted: 14 April 2000 相似文献