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1.
An endophytic fungus, Gibberella pulicaris, produced an amylase which degraded raw starches from cereals and other crops including raw potato, sago, tapioca, corn, wheat and rice starch. In each case, glucose was the main product. Among the raw starches used, raw potato starch gave the highest enzyme activity (85 units mg–1 protein) and raw wheat starch the lowest (49 units mg–1 protein). The highest amylase production (260 units mg–1 protein) was achieved when the concentration of raw potato starch was increased to 60 g l–1. Optimum hydrolysis was at 40°C and pH 5.5. 相似文献
2.
Murthy GS Johnston DB Rausch KD Tumbleson ME Singh V 《Bioprocess and biosystems engineering》2011,34(7):879-890
Efficiency of the starch hydrolysis in the dry grind corn process is a determining factor for overall conversion of starch
to ethanol. A model, based on a molecular approach, was developed to simulate structure and hydrolysis of starch. Starch structure
was modeled based on a cluster model of amylopectin. Enzymatic hydrolysis of amylose and amylopectin was modeled using a Monte
Carlo simulation method. The model included the effects of process variables such as temperature, pH, enzyme activity and
enzyme dose. Pure starches from wet milled waxy and high-amylose corn hybrids and ground yellow dent corn were hydrolyzed
to validate the model. Standard deviations in the model predictions for glucose concentration and DE values after saccharification
were less than ±0.15% (w/v) and ±0.35%, respectively. Correlation coefficients for model predictions and experimental values
were 0.60 and 0.91 for liquefaction and 0.84 and 0.71 for saccharification of amylose and amylopectin, respectively. Model
predictions for glucose (R
2 = 0.69–0.79) and DP4+ (R
2 = 0.8–0.68) were more accurate than the maltotriose and maltose for hydrolysis of high-amylose and waxy corn starch. For
yellow dent corn, simulation predictions for glucose were accurate (R
2 > 0.73) indicating that the model can be used to predict the glucose concentrations during starch hydrolysis. 相似文献
3.
Joanna Kotyńska Izabela Dobrzyńska Zbigniew Artur Figaszewski 《Journal of bioenergetics and biomembranes》2008,40(6):637-641
We examined the effect of adsorbed monovalent ions on the surface charge of phosphatidylcholine (PC) – decylamine (DA) liposomal
membranes. Surface charge density values were determined from electrophoretic mobility measurements of lipid vesicles performed
at various pH levels. The interaction between solution ions and the PC-DA liposomal surface was described by a six component
equilibrium model. The previously determined association constants of the -PO(-) and –N(+)(CH3)3 groups of PC with H+, OH-, Na+ and Cl- ions (K
A1H, K
B1OH, K
A1Na, K
B1C1) were used to calculate K
B2OH, and K
B2C1, the association constants of the –N(+)H3 group of DA with OH- and Cl- ions, providing an experimental verification for the proposed model. 相似文献
4.
The interfacial tension of lipid membranes composed of phosphatidylcholine (lecithin, PC)–valine (Val), phosphatidylcholine–isoleucine
(Ile), phosphatidylcholine–tyrosine (Tyr), and phosphatidylcholine–phenylalanine (Phe) has been studied. The membrane components
formed 1:1 complexes. The interfacial tension measurements were used to determine the membrane surface concentration A
3−1, the membrane interfacial tension γ3, and the stability constant K. 相似文献
5.
M Chellapandian C Larios M Sanchez-Gonzalez A Lopez-Munguia 《Journal of industrial microbiology & biotechnology》1998,21(1-2):51-56
Dextransucrase was produced from a Leuconostoc mesenteroides isolated from pulque, a traditional Aztec alcoholic beverage produced from agave juice containing sucrose as the main carbon source. Almost all
the dextransucrase activity (87%) was associated with the cells, and was unusually high (1.04 U mg−1 of cells). The culture medium composition was optimized through a Box-Behnken method resulting in a process yielding 2.2 U ml−1 of insoluble glucosyltransferase activity. The enzyme had a molecular weight of 166 kDa. Optimal temperature was 35°C with
a half-life of 137 min at the same temperature. As with dextransucrase from the industrial strain L. mesenteroides NRRL B-512F, the enzyme showed Michaelis–Menten kinetic behavior with excess substrate inhibition (K
m and K
i values of 0.026 M and 1.23 M respectively); produced soluble linear dextran with glucose molecules linked mainly in α(1–6)
with branching in α(1–3) in a proportion of 4:1 as shown by NMR studies; and produced a high yield of isomalto-oligosaccharides
in the presence of maltose.
Received 4 February 1998/ Accepted in revised form 25 July 1998 相似文献
6.
Theoretical studies of an unsymmetrical calix[4]-crown-5-N-azacrown-5 (1) in a fixed 1,3-alternate conformation and the complexes 1·K+(a), 1·K+(b), 1·K+(c) and 1·K+K+ were performed using density functional theory (DFT) at the B3LYP/6-31G* level. The fully optimized geometric structures
of the free macroligand and its 1:1 and 1:2 complexes, as obtained from DFT calculations, were used to perform natural bond
orbital (NBO) analysis. The two main types of driving force metal–ligand and cation–π interactions were investigated. NBO
analysis indicated that the stabilization interaction energies (E
2) for O…K+ and N…K+ are larger than the other intermolecular interactions in each complex. The significant increase in electron density in the
RY* or LP* orbitals of K+ results in strong host–guest interactions. In addition, the intermolecular interaction thermal energies (ΔE, ΔH, ΔG) were calculated by frequency analysis at the B3LYP/6-31G* level. For all structures, the most pronounced changes in the
geometric parameters upon interaction are observed in the calix[4]arene molecule. The results indicate that both the intermolecular
electrostatic interactions and the cation–π interactions between the metal ion and π orbitals of the two pairs that face the
inverted benzene rings play a significant role. 相似文献
7.
The chemical composition of rainwater is altered upon its passage through tree canopies. In order to investigate how rainwater
chemistry is affected by canopy-dependent processes in characteristic forest types of Northwest German sandy lowland regions
– oak–birch-forests, Betula pubescens Ehrh. swamp forests, and stands of Pinus sylvestris L. – comparative studies on the chemical composition of throughfall were carried out at seven forest sites, situated in close
proximity within a nature reserve. Additionally, rainwater was sampled at three heathland sites for analysis of open-field
precipitation and at three sites along an oak–birch-forest edge. Throughfall concentrations of most of the parameters analysed
were significantly higher than open-field concentrations, especially with regard to electric conductivity, NH4-N, K+, and KMnO4-index. Ion concentrations in throughfall were the lowest in a 10-year-old stand of Betula pendula Roth. and Pinus sylvestris and in a Betula pubescens swamp forest and were highest beneath a stand of Pinus sylvestris. Except for Na+, Cl−, and NO3−, ion concentrations in both throughfall and open-field precipitation increased during the growing season (May–October). In
throughfall, Ca2+, Mg2+, K+, and Mn2+ were strongly correlated. Enrichment ratios between throughfall and open-field deposition varied among sites and elements
and were the highest for K‰+, Mg2‰+, and Mn2‰+. Estimates of canopy leaching indicated high leaching rates of K‰+ and Mn2‰+ and moderate leaching of Mg2‰+. The contribution of foliar leaching to throughfall deposition was higher at the deciduous than at the coniferous stands. 相似文献
8.
The objective of this work was to develop matrix sustained-release tablets of highly water-soluble tramadol HCl using natural
gums (xanthan [X gum] and guar [G gum]) as cost-effective, nontoxic, easily available, and suitable hydrophilic matrix systems
compared with the extensively investigated hydrophilic matrices (ie, hydroxypropyl methylcellulose [HPMC]/carboxymethyl cellulose
[CMC] with respect to in vitro drug release rate) and hydration rate of the polymers. Matrix tablets of tramadol (dose 100
mg) were produced by direct compression method. Different ratios, of 100∶0, 80∶20, 60∶40, 20∶80, 0∶100 of G gum (or X):HPMC,
X gum:G gum, and triple mixture of these polymers (G gum, X gum, HPMC) were applied. After evaluation of physical characteristics
of tablets, the dissolution test was, performed in the phosphate buffer media (pH 7.4) up to 8 hours. Tablets with only X
had the highest mean dissolution time (MDT), the least dissolution efficiency (DE8%), and released the drug following a zero-order model via swelling, diffusion, and erosion mechanisms. Guar gum alone could
not efficiently control the drug release, while X and all combinations of natural gums with HPMC could retard tramadol HCl
release. However, according to the similarity factor (f
2), pure HPMC and H8G2 were the most similar formulations to Topalgic-LP as the reference standard.
Published: March 17, 2006 相似文献
9.
Potassium (K+) and chloride (Cl−) are two essential elements for plant growth and development. While it is known that plants possess specific membrane transporters
for transporting K+ and Cl−, it remains unclear if they actively use K+-coupled Cl− cotransporters (KCC), as used in animals, to transport K+ and Cl−. We have cloned an Oryza sativa cDNA encoding for a member of the cation–Cl− cotransporter (CCC) family. Phylogenetic analysis revealed that plant CCC proteins are highly conserved and that they have
greater sequence similarity to the sub-family of animal K+–Cl− cotransporters than to other cation–Cl− cotransporters. Real-time PCR revealed that the O. sativa cDNA, which was named OsCCC1, can be induced by KCl in the shoot and root and that the expression level was higher in the leaf and root tips than in any
other part of the rice plant. The OsCCC1 protein was located not only in onion plasma membrane but also in O. sativa plasma membrane. The OsCCC1 gene-silenced plants grow more slowly than wild-type (WT) plants, especially under the KCl treatment regime. After 1 month
of KCl treatment, the leaf tips of the gene-silenced lines were necrosed. In addition, seed germination, root length, and
fresh and dry weight were distinctly lower in the gene-silenced lines than in WT plants, especially after KCl treatment. Analysis
of Na+, K+, and Cl− contents of the gene-silenced lines and WT plants grown under the NaCl and KCl treatment regimes revealed that the former
accumulated relatively less K+ and Cl− than the latter but that they did not differ in terms of Na+ contents, suggesting OsCCC1 may be involved in K+ and Cl− transport. Results from different tests indicated that the OsCCC1 plays a significant role in K+ and Cl− homeostasis and rice plant development. 相似文献
10.
Nicola D’Amelio Luca Fontanive Fulvio Uggeri Furio Suggi-Liverani Luciano Navarini 《Food biophysics》2009,4(4):321-330
Caffeine complexation by chlorogenic acid (3-caffeoylquinic acid, CAS Number [327-97-9]) in aqueous solution as well as caffeine–chlorogenate
complex in freshly prepared coffee brews have been investigated by high-resolution 1H-NMR. Caffeine and chlorogenic acid self-associations have also been studied and self-association constants have been determined
resorting to both classical isodesmic model and a recently introduced method of data analysis able to provide also the critical
aggregation concentration (cac). Furthermore, caffeine–chlorogenate association constant was measured. For the caffeine, the
average value of the self-association constant determined by isodesmic model (K
i = 7.6 ± 0.5 M−1) is in good agreement with the average value (K
a = 10 ± 1.8 M−1) determined with the method which permits the determination of the cac (8.43 ± 0.05 mM). Chlorogenic acid shows a slight
decreased tendency to aggregation with a lower average value of association constants (K
i = 2.8 ± 0.6 M−1; K
a = 3.4 ± 0.6 M−1) and a critical concentration equal to 24 ± 1 mM. The value of the association constant of the caffeine–chlorogenate complex
(30 ± 4 M−1) is compatible with previous studies and within the typical range of reported association constants for other caffeine–polyphenol
complexes. Structural features of the complex have also been investigated, and the complex conformation has been rediscussed.
Caffeine chemical shifts comparison (monomeric, complexed, coffee brews) clearly indicates a significant amount of caffeine
is complexed in beverage real system, being chlorogenate ions the main complexing agents. 相似文献
11.
O. M. Rozhmanova E. V. Dolgaya N. Kh. Pogorelaya I. S. Magura Z. Yu. Tkachuk I. A. Mikhailopulo 《Neurophysiology》2006,38(2):81-85
We studied the effect of an epoxy derivative of dephosphorylated 2′,5′-trioligoadenylate (5′,5′ApApAepoxy) resistive to the
action of cellular phosphodiesterase on cells of human neuroblastoma IMR 32 cultured in vitro. Twenty-two hours after the addition of 5·10−6 M 2′,5′ApApAepoxy to the culture medium, the number of cells decreased by 20% (P < 0.05), while the content of protein in these cells increased, on average, by 52% (P < 0.01), as compared with the control. The activities of Na+,K+-and Ca2+, Mg2+-ATPases in a microsomal fraction obtained from cells cultured in the presence of 2′, 5′ ApApAepoxy decreased by 50% (P < 0.001) as compared with those in the control cells. Our data indicate that 2′,5′ApApAepoxy possess antiproliferative activity.
According to our findings, the antiproliferative effect of 2′,5′ ApApAepoxy can, to a great extent, be explained by the fact
that this oligoadenylate derivative significantly modulates the activities of Na+,K+-and Ca2+,Mg2+-ATPases.
Neirofiziologiya/Neurophysiology, Vol. 38, No. 2, pp. 97–102, March–April, 2006. 相似文献
12.
Luo H Wang Y Wang H Yang J Yang Y Huang H Yang P Bai Y Shi P Fan Y Yao B 《Applied microbiology and biotechnology》2009,82(3):453-461
Using degenerate polymerase chain reaction (PCR) and thermal asymmetric interlaced PCR, a 1,347-bp full-length complementary
DNA fragment encompassing the gene man5A, which encodes a 429-amino acid β-mannanase with a calculated mass of 46.8 kDa, was cloned from acidophilic Bispora sp. MEY-1. The deduced amino acid sequence (catalytic domain) displayed highest identity (54.1%) with the Emericella nidulans endo-β-1,4-d-mannanase, a member of the glycoside hydrolase family 5. Recombinant MAN5A was overexpressed in Pichia pastoris, and its activity in the culture medium reached 500 U ml−1. The enzyme was acidophilic, with highest activity at pH 1.0–1.5, lower than any known mannanases, and optimal temperature
for activity was 65°C. MAN5A had good pH adaptability, excellent thermal and pH stability, and high resistance to both pepsin
and trypsin. The specific activity, K
m, and V
max for locust bean gum substrate was 3,373 U mg−1, 1.56 mg ml−1, and 6,587.6 μmol min−1 mg−1, respectively. The enzymatic activity was not significantly affected by ions such as Ca2+, Cr3+, Co2+, Zn2+, Na+, K+, and Mg2+ and enhanced by Ni2+, Fe3+, Mn2+ and Ag+. These favorable properties make MAN5A a potential candidate for use in various industrial applications. 相似文献
13.
We have identified two types of invertases, one bound ionically and the other covalently to the particulate fraction in grains
of heat tolerant C 306 and heat susceptible WH 542 cultivars of wheat (Triticum aestivum L.). The cell walls contained a high level of invertase activity, of which 79.2–72.8% was extractable by 2 M NaCl and 14.9–21.1%
by 0.5% EDTA in C 306 and WH 542, respectively. The NaCl-released invertase constituted the predominant fraction. Using 5–100 mM
sucrose and pH range of 4.0–7.0, the apparent Michaelis constant (K
m, enzyme substrate affinity measure) of enzyme ranged from 5.73 to 16.06 mM for C 306 and from 6.08 to 19.86 mM for WH 542.
The V
max (maximum catalytic rate) values at these pH were higher in C 306 (0.63–11.04 μg sucrose hydrolysed min−1) than WH 542 (0.51–8.73 μg sucrose hydrolysed min−1). By employing photo-oxidation and by studying the effect of pH on K
m and V
max, the involvement of histidine and α-carboxyl groups at the active site of the enzyme was indicated. The two cultivars also
showed differential response in terms of thermodynamic properties of the enzyme i.e. energy of activation (E
a), enthalpy change (ΔH) and entropy change (ΔS). NaCl-released invertase showed differential response to metal ions in two cultivars suggesting their distinctive nature.
Mn2+, Cu2+, Hg2+, Mg2+, Zn2+ and Cd2+ were strong inhibitors in WH 542 as compared to C 306 while K+, Ca2+ were stimulators in both the cultivars. Overall the results suggest that genetic differences exist in wall bound invertase
properties of wheat grains as evident in its altered kinetic behaviour. 相似文献
14.
This study describes the application of the laser photoacoustic spectroscopy (PAS) for quantification of total carotenoids
(TC) in corn flours and sweetpotato flours. Overall, thirty-three different corn flours and nine sweetpotato flours were investigated.
All PAS measurements were performed at room temperature using 488-nm argon laser radiation for excitation and mechanical modulation
of 9 and 30 Hz. The measurements were repeated within a run and within several days or months. The UV–Vis spectrophotometry
was used as the reference method. The concentration range that allows for the reliable analysis of TC spans a region from
1 to 40 mg kg−1 for corn flours and from 9 to 40 mg kg−1 for sweetpotato flours. In the case of sweetpotato flours, the quantification may extend even to 240 mg kg−1 TC. The estimated detection limit values for TC in corn and sweetpotato flours were 0.1 and 0.3 mg kg−1, respectively. The computed repeatability (n = 3–12) and intermediate precision (n = 6–28) RSD values at 9 and 30 Hz are comparable: 0.1–17.1% and 5.3–14.7% for corn flours as compared with 1.4–9.1% and 4.2–23.0%
for sweetpotato flours. Our results show that PAS can be successfully used as a new analytical tool to simply and rapidly
screen the flours for their nutritional potential based on the total carotenoid concentration. 相似文献
15.
E. V. Navolotskaya T. A. Zargarova T. N. Lepikhova V. L. Turobov R. I. Nurieva N. V. Malkova V. P. Zav’yalov V. M. Lipkin 《Russian Journal of Bioorganic Chemistry》2000,26(1):27-33
The antiproliferative and immunosuppressivein vitro effects ofimmunocortin, a synthetic adrenocorticotropin-like (ACTH-like) decapeptide H-Val-Lys-Lys-Pro-Gly-Ser-Ser-Val-Lys-Val-OH, whose sequence
corresponds to segment 11–20 of the variable part of the human IgG1 heavy chain, were studied. At concentrations of 10−11−10−7 M, immunocortin was found to inhibit the growth of the human MT-4 T-lymphoblastoid cell line, to suppress the blast transformation
of thymocytes, and to decrease the spontaneous mobility of peritoneal macrophages and their bactericidal action toward the
virulent strainSalmonella typhimurium 415. By using a125I-labeled “addressing” fragment of ACTH {[125I]ACTH (13–24)}, we showed that MT-4 cells express specific receptors for ACTH (K
d 97 pM). Immunocortin and human ACTH (but not the heavy chain of IgG1) competitively inhibited the binding of [125I]ACTH-(13–24) to these receptors withK
i1 of 0.38 andK
i2 of 0.34 nM, respectively. Specific receptors for ACTH (K
d 5.8 nM) on mouse thymocytes were detected and characterized. The unlabeled immunocortin was shown to compete with labeled
ACTH-(13–24) for binding to these receptors (K
i=1.8 nM), and this binding of immunocortin to receptors on thymocytes activates adenylate cyclase from these cells and increases
the intracellular concentration of cAMP. 相似文献
16.
Chellappan S Jasmin C Basheer SM Kishore A Elyas KK Bhat SG Chandrasekaran M 《Journal of industrial microbiology & biotechnology》2011,38(6):743-752
An alkaline protease from marine Engyodontium album was characterized for its physicochemical properties towards evaluation of its suitability for potential industrial applications.
Molecular mass of the enzyme by matrix-assisted laser desorption ionization-mass spectrometry (MALDI-MS) analysis was calculated
as 28.6 kDa. Isoelectric focusing yielded pI of 3–4. Enzyme inhibition by phenylmethylsulfonyl fluoride (PMSF) and aprotinin
confirmed the serine protease nature of the enzyme. K
m, V
max, and K
cat of the enzyme were 4.727 × 10−2 mg/ml, 394.68 U, and 4.2175 × 10−2 s−1, respectively. Enzyme was noted to be active over a broad range of pH (6–12) and temperature (15–65°C), with maximum activity
at pH 11 and 60°C. CaCl2 (1 mM), starch (1%), and sucrose (1%) imparted thermal stability at 65°C. Hg2+, Cu2+, Fe3+, Zn2+, Cd+, and Al3+ inhibited enzyme activity, while 1 mM Co2+ enhanced enzyme activity. Reducing agents enhanced enzyme activity at lower concentrations. The enzyme showed considerable
storage stability, and retained its activity in the presence of hydrocarbons, natural oils, surfactants, and most of the organic
solvents tested. Results indicate that the marine protease holds potential for use in the detergent industry and for varied
applications. 相似文献
17.
Polymerization of 20% neutralized acrylic acid (Na form), AA, in presence of Karaya gum, KG, or tamarind seed gum, TG, at AA/gum weight ratio of 1/1 and 2/1 results in PAA/KG1, PAA/KG2, PAA/TG1 and PAA/TG2 adducts, respectively (where the suffix 1 or 2 stands for AA/gum ratios of 1/1 or 2/1). Infra red spectra of adducts are examined. Aqueous pastes of adducts, native gums and GG are of non-Newtonian thixotropic flow within a shear rate range of 4–40 s−1. Adduct pastes (7.5% w/v) are of higher apparent viscosities (η) than their native gums or GG, and pastes of TG adducts are of higher η than KG adducts. Except for PAA/TG2 adduct, the power law does not correlate well to the other pastes. Preliminary trials showed that adducts are excellent thickeners for reactive and acid printing on wool, silk and nylon 6. Prints by adducts are of higher color strength than those by native gums or GG. GG paste was completely destroyed after storing for 7 days, whereas η of pastes of adducts and native gums were noticeably decreased upon storing. 相似文献
18.
S. Benini Marco Borsari S. Ciurli Alexander Dikiy M. Lamborghini 《Journal of biological inorganic chemistry》1998,3(4):371-382
Direct cyclic voltammetry and 1H NMR spectroscopy have been combined to investigate the electrochemical and spectroscopic properties of cytochrome c
553 isolated from the alkaliphilic soil bacterium Bacillus pasteurii. A quasi-reversible diffusion-controlled redox process is exhibited by cytochrome c
553 at a pyrolitic graphite edge microelectrode. The temperature dependence of the reduction potential, measured using a non-isothermal
electrochemical cell, revealed a discontinuity at 308 K. The thermodynamic parameters determined in the low-temperature range
(275–308 K;ΔS°′=–162.7±1.2 J mol–1 K–1, ΔH°′=–53.0±0.5 kJ mol–1, ΔG°′=–4.5±0.1 kJ mol–1, E°′=+47.0±0.6 mV) indicate the presence of large enthalpic and entropic effects, leading, respectively, to stabilization and
destabilization of the reduced form of cytochrome c
553. Both effects are more accentuated in the high-temperature range (308–323 K;ΔS°′=–294.1±8.4 J mol–1 K–1, ΔH°′=–93.4±3.1 kJ mol–1, ΔG°′=–5.8±0.6 kJ mol–1, E°′=+60.3±5.8 mV), with the net result being a slight increase of the standard reduction potential. These thermodynamic parameters
are interpreted using the compensation theory of hydration of biopolymers as indicating the extrusion, upon reduction, of
water molecules from the hydration sphere of the cytochrome. The low-T and high-T conformers differ by the number of water molecules in the solvation sphere: in the high-T conformer, the number of water molecules extruded upon reduction increases, as compared to the low-T conformer. The ionic strength dependence of the reduction potential at 298 K, treated within the frame of extended Debye-Hückel
theory, yields values of E
°′
(I=0)
=–25.4±1.4 mV, z
red=–11.3, and z
ox=–10.3. The pH dependence of the reduction potential at 298 K shows a plateau in the pH range 7–10 and an increase at more
acidic pH, allowing the calculation of pK
O=5.5 and pK
R=5.7, together with the estimate of the reduction potentials of completely protonated (+71 mV) and deprotonated (+58 mV) forms
of cytochrome c
553. 1H NMR spectra of the oxidized paramagnetic cytochrome c
553 indicate the presence of a His-Met axial coordination of the low-spin (S=1/2) heme iron, which is maintained in the temperature interval 288–340 K at pH 7 and in the pH range 4.8–10.0 at 298 K.
The temperature dependence of the hyperfine-shifted signals shows both Curie-type and anti-Curie-type behavior, with marked
deviations from linearity, interpreted as indicating the presence of a fast equilibrium between the low-T and high-T conformers, having slightly different heme electronic structures resulting from the T-induced conformational change. Increasing the NaCl concentration in the range 0–0.2 M causes a slight change of the 1H NMR chemical shifts of the hyperfine-shifted signals, with no influence on their linewidth. The calculated lower limit value
of the apparent affinity constant for specific ion binding is estimated as 5.2±1.1 M–1. The pH dependence of the isotropically shifted 1H NMR signals of the oxidized cytochrome displays at least one ionization step with pK
O=5.7. The thermodynamic and spectroscopic data indicate a large solvent-derived entropic effect as the main cause for the
observed low reduction potential of B. pasteurii cytochrome c
553.
Received: 9 January 1998 / Accepted: 8 April 1998 相似文献
19.
Nhu-Ngoc Nguyen Thi Tuong Vi Tran Quoc-Duy Nguyen Tran-Phong Nguyen Tuyet-Ngan Lien 《Biotechnology progress》2023,39(4):e3344
Bacterial cellulose (BC) is a biopolymer with applications in numerous industries such as food and pharmaceutical sectors. In this study, various hydrocolloids including modified starches (oxidized starch—1404 and hydroxypropyl starch—1440), locust bean gum, xanthan gum (XG), guar gum, and carboxymethyl cellulose were added to the Hestrin-Schramm medium to improve the production performance and microstructure of BC by Gluconacetobacter entanii isolated from coconut water. After 14-day fermentation, medium supplemented with 0.1% carboxymethyl cellulose and 0.1% XG resulted in the highest BC yield with dry BC content of 9.82 and 6.06 g/L, respectively. In addition, scanning electron microscopy showed that all modified films have the characteristic three-dimensional network of cellulose nanofibers with dense structure and low porosity as well as larger fiber size compared to control. X-ray diffraction indicated that BC fortified with carboxymethyl cellulose exhibited lower crystallinity while Fourier infrared spectroscopy showed characteristic peaks of both control and modified BC films. 相似文献
20.
Scott GR Keir KR Schulte PM 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2005,175(7):499-510
We have explored the possible mechanisms by which mineralocorticoid (MR) and glucocorticoid (GR) receptors regulate the response
to freshwater transfer in the gills of the euryhaline killifish Fundulus heteroclitus. Killifish were implanted with RU486 (GR antagonist) or spironolactone (MR antagonist) at doses of 0.1–1.0 mg g−1, and subsequently transferred from 10‰ brackish water to freshwater. Compared to brackish water sham fish, mRNA expression
of CFTR and NKCC1 decreased in the gills of sham fish transferred to freshwater, whereas Na+,K+–ATPase α1a
mRNA expression and α protein abundance, as well as cell proliferation (detected using BrdU) increased. Spironolactone inhibited
the normal increase in cell proliferation and Na+,K+-ATPase expression after freshwater transfer. RU486 increased plasma cortisol levels and may have slightly inhibited Na+,K+–ATPase activity, but did not change α 1a
expression. RU486 had no effect on cell proliferation in the non-lamellar region of the gills, but increased proliferation
in the lamellar region. Neither antagonist inhibited the suppression of CFTR or NKCC1 expression after freshwater transfer.
Glucocorticoid receptor expression was reduced in all sham and antagonist treatments compared to untreated controls, but no
other consistent differences were observed. The effects of spironolactone suggest that MR is important for regulating ion
transport in killifish gills after freshwater transfer. 相似文献