Studies on reduced extent method for inhibited thermokinetics of enzyme-catalyzed reaction

The thermokinetic reduced extent equations of reversible inhibitions for Michaiels-Menten enzymatic reaction were deduced, and then the criteria for distinguishing inhibition type was given and the methods for calculating kinetic parameters,K _M,K _i andv _m were suggested. This theory was applied to inverstigate the inhibited thermokinetics of laccase-catalyzed oxidation ofo-dihydroxybenzene bym-dihydroxybenzene. The experimental results show the inhibition belongs to reversible competitive type,K _M=6.224×10⁻³ mol·L⁻¹,K _i=2.363×10⁻² mol·L⁻¹. Xiong Ya: born Sep. 1961, Ph. D. graduate student. Curent research interest is in biothermochemistry research Supported by the National Natural Science Foundation of China     

An improved method for measuring the stability of a three-state unfolding protein

In the current three-state protein unfolding model, the two transitions are considered to be independent and each transition is fitted to a two-state unfolding model. This three-state unfolding process is therefore composed of two sequential two-state unfolding processes. In this paper, a modified method is presented to determine the value of the unfolding free energy [δG _total⁰(H₂O)] for the three-state unfolding equilibrium of proteins. This method is demonstrated on the apoCopC protein mutant, Y79W-W83F-Cu, which unfolds via a three-state process. The value of ΔG _total⁰(H₂O) calculated using the modified method was found to be more accurate in determining ΔG _total⁰(H₂O) than the previously reported method.     

The Total Irredundance Numbers on Graphs

This paper discusses the total irredundance relations between the graph G and its clone-contraction graph H, that is, let H be the clone-contraction graph of G and v1,v2,...,vk be all contraction vertices ofH. IfS is a maximal total irredundant set of H such that A = S ∩ {V1,V2,…,Vk} contains as few vertices as possible, then S＇= S-A is the maximal total irredundant set of G. Furthermore, we obtain the bound of the total irredundance A（G） number： irt ≤△（G）/2△（G）＋1 n, which n is the order of graph G, and △（G） is maximum degree in G.     

Synthesis and Characterization of Polyamide-Containing 2, 6- （Substituded） pyridine Derivatives

0 IntroductionPayrriodminaetiics hoenteer oofc ythcleics m .os tC oambupnoduanndts a cnodn tbaeisntin kgno twhnepyridine ring are widely distributedin nature,principally asenzymes and alkaloids . Pyridine enzymes have been foundintissues of all plants and ani mals examined thus far ,andare derivedfromeither nicotinic acid or Vitamin B6[1].Pyr-idine derivatives are also the building block of many phar-maceuticals with a wide range of functionalities that includeantitubercular compounds ,antivi…     

Kinetic studies of the decomposition reaction of adducts of dinuclear Fe(Ⅱ)/O2

Kinetic studies of the decomposition reaction of dinuclear Fe(Ⅱ) adducts [Fe₂(N-Et-HPTB){O₂P(OPh)₂}](Cl- O₄)₂ (1) and [Fe₂(N-Et-HPTB) {O₂P(Ph)₂}] (ClO₄)₂ (2) with O₂ have been carried out at low temperature using UV-vis spectra. The decomposition reaction of Fe(Ⅱ)/O₂ adducts was first-order in the experimental conditions, and the activation parameters were obtained. ?H^¹ = 85.62 kJ·mol^-1, ?S¹ = 19.43 J·mol^-1·K^-1 for compound (1) and ?H^¹ = 97.97 kJ·mol^-1, ?S^¹ = 55.68 J·mol^-1·K^-1 for compound (2). These results are similar to those of dioxygen adducts of other metals complexes and natural enzymes such as methane mono- oxygenase (MMOH).     

An explanation to the high efficiency ofm-THPC (temporfin) used in photodynamic therapy

Meso-tetrahydroxylphenyl chlorin (m-THPC) is one of the most efficient prospective sensitizers used in photodynamic therapy (PDT). ESR spectroscopy, fluorescence quenching experiments and cyclic voltammogram measurement were used to study its redox properties. The results showed that the ability of m-THPC generating superoxide radical anions was very strong, and the rate constant of m-THPC fluorescence quenching by oxygen k_q (O₂)=1.46×10¹⁰ mol^-1·s^-1. The values of fluorescence quen- ching rate constant of m-THPC by some other electron acceptors, such as methyl viologen (MV²⁺) and anthraquinone (An), were also measured. And they were k_q (MV²⁺)=5.51×10⁹ mol^-1·s^-1, k_q (An)=7.81×10⁹ mol^-1·s^-1. The oxidation potential of m-THPC was examined to be +0.62 V (vs. NHE) in acetonitrile. All these suggested that m-THPC should be a much stronger electron donor than photofrin, the currently used in clinical photodrug, and may react easily through electron transfer with biological matter to yield various radicals. So it seemed reasonable that the type Ⅰ reaction may play an important role in the high activity of m-THPC-PDT.     

Fluorescence Determination of Artemisinin Using Hemoglobin as Catalyst and Pyronine B as Substrate

0 IntroductionMaalnadria siusb atr ompajicosr .he aAltrthe pmrisoibnlienmi (n qtihneghtraoopsiucs,QHS,Fig.1) is a sesquiterpene endoperoxide isola-ted fromArtemisia annuaL., an ancient Chineseherbal medicine usedfor treatment of fever and ma-laria.Studies of the structure and activity relation-ship have shownthat endoperoxide groupis essentialfor anti malarial activity of QHS and absence of thismoiety lead to completely loss in activity of thedrug. Many techniques have been developed to de…     

Determination of the solubility parameter of cellulose acrylate using inverse gas chromatography

The solubility parameters of cellulose acrylate substituted degree 2.12(CEA) have been calculated from the measured retention data by inverse gas chromatography at various temperatures. The weight frac-tion activity coefficients of the solvents at infinite dilution(Ω1∞),the Flory-Huggins thermodynamic in-teraction parameters between CEA and solvents(χ 1∞2),the excess molar heats of mixing(△H1s),the par-tial molar heats of mixing at infinite dilution(△H1∞),the solubility parameters of solvent(δ1),and the solubility parameters of CEA(δ2),were calculated at various temperatures. The δ2 of the CEA was 17.32,18.00,18.13,18.54,19.39 at 55,60,65,70 and 75℃,respectively.     

Investigation of charge transfer complexes formed between 3,3＇-dimethylbenzidine （o-toluidine） donor and DDQ, p-chloranil and TCNQ as π-acceptors

Charge-transfer (CT) complex of o-toluidine (o-tol) with the π-acceptor tetrachloro-p-benzoquinone (p-chloranil; CHL) has been synthesized and characterized, along with the products of the elimination reaction of o-toluidine (o-tol) with 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) and 7,7,8,8-tetracyanoquinodimethane (TCNQ). Their properties and structures have been investigated using electronic absorption and IR spectroscopy as well as elemental analyses of the isolated compounds. The o-tol/p-CHL CT complex is shown to consist of a CHL⁻ radical anion and o-tol⁺ radical cation. The formations of all three compounds result in the appearance of new UV-Vis spectral bands that peaked in intensity at a stoichiometric ratio of 1:1. ¹H-NMR and mass spectra were used to confirm the formation of the o-tol/DDQ and o-tol/TCNQ products. The new 7,8-dicyano-7′,8′-o-toluidilequino-dimethane and 2,3-dichloro-5-cyano-6-o-toluidil-p-benzoquinone products resulted from the rapid reaction of o-tol with TCNQ and DDQ, respectively. Thermogravimetric studies showed that the CT-complex decomposes in three steps whereas the new compounds decompose in a single step. Thermodynamic parameters were computed from the thermal decomposition data.     

Thermodynamic determination of fragility in La-based glass-forming liquid

Differences in the thermodynamic functions between the liquid and crystalline states of La-based bulk metallic glasses alloys were calculated with the specific heat capacity Cp and the fusion heat ΔHf,which we measured. Fragility indexes having different thermodynamic definitions were calculated from the temperature dependence of excess entropy ΔSliq-cry. It is ambiguous for La-based glass-forming liquid to evaluate fragility from the intercepts of ΔSliq-cry-temperature curves. We found that the thermodynam...     

邻香草醛缩胱氨酸双Schiff碱的合成及其对粟酒裂殖酵母细胞生长代谢的热动力学研究

用摩尔比为2:1的邻香草醛(C_8H_8O_3)与L-胱氨酸(C_6H_(12)N_2O_4S_2)反应,合成了一种新的双Schiff碱化合物--双{2-[(3-巯基丙酸钠)-2-亚胺基-甲基]-6-甲氧基-苯酚}(OVCS)。通过元素分析、红外光谱、核磁共振等手段对其组成和结构进行了表征,确定其化学式为Na_2(C_(22)H_(22)N_2O_8S_2),采用TAM air微量热仪测定了新合成的Schiff碱化合物(OVCS)在305.15 K时对粟酒裂殖酵母细胞作用的产热曲线;根据产热曲线计算了在OVCS作用下,粟酒裂殖酵母细胞生长代谢的最大发热功率p_(max)、速率常数k、传代时间tG、抑制率I和半抑制浓度C_(I,50)等热动力学参数。通过实验可以发现随着OVCS浓度的增加,粟酒裂殖酵母细胞的生长代谢速率常数k、生长代谢的总热效应Q_(total)、最大发热功率p_(max)均减小,抑制率I、达到生长代谢最大功率所需时间t_(max)、传代时间tG均增加等规律,半抑制浓度C_(I,50)为35.99 mg/L(或9.62×10~(-2)mol/L)。实验结果表明,OVCS对粟酒裂殖酵母细胞有抑制作用,且浓度越大,抑制作用越强。     

Minus domination number in cubic graph

An upper bound is established on the parameter Γ -(G) for a cubic graph G and two infinite families of 3-connected graphs G k, G * k are constructed to show that the bound is sharp and, moreover, the difference Γ -(G * k)-γ s(G * k) can be arbitrarily large, where Г -(G * k) and γ s(G * k) are the upper minus domination and signed domination numbers of G * k, respectively. Thus two open problems are solved.     

Effects of antisense CENP-B on the proliferation of HeLa (Tet-off) cells

In order to study the change of the expression of centromere protein B (CENP-B) caused by antisense transfection, proto-eukaryotically expressed fused protein GST-CENP-B (65 ku) was injected into mouse, and a peculiar anti-CENP-B serum MaCenpB was collected. A strain of transfected HeLa Tet-off cell HaCb, which contains antisense CENP-B expressing vector pBI-EGFP-as-CenpB, was prepared. Northern blot and Western blot were used to analyze the repression of internal CENP-B in transfected cells. According to the growth curve, the proliferation of HeLa (Tet-off) is repressed by antisense CENP-B, and the multiplication time is prolonged for 32.81 h. The analysis of flow cytometry revealed that, compared with HeLa (Tet-off), the G₁ cell population of HaCb is increased (ΔG₁= 9%) while S fraction is decreased (ΔS = 11%), but the G₂/M phase is nearly unchanged (ΔG₂/M=3%). In the meanwhile, the mitotic index of HaCb declines greatly compared with that of HeLa (Tet-off). Immunofluorescence showed that the assembling of centromeres in HaCb cell is arrested. These results suggest that a normal expression of CENP-B may be necessary for cell proliferation.     

The biomarkers of 2,6,10,15, 19-pentamethylicosenes and their carbon isotopic composition in the sediments from the Gulf of Mexico

The methanogenic archaea and sulfate reduction bacteria are flourishing in the sediments associated with gas venting and gas hydrate settings on the sea floor, where the anaerobic oxidation of methane (AOM) me-diated by these bacteria is the dominant path…     

The composition and distribution of metal clusters in the MoFe protein from a nifZ deletion strain （DJ 194） of Azotobacter vinelandii

Through the anaerobic chromatography on the columns of DEAE 52, Q-Sepharose and Sephacryl S-200, a nitrogenase MoFe protein (△nifZ Av1) was obtained from a nifZ deleted mutant of Azotobacter vinelandii (stain DJ194).The results of Western blotting after anoxic native electrophoresis and SDS-PAGE showed that △nifZ Av1 was similar to wild type MoFe protein (OP Av1) at the electrophoretic mobility, molecular weight and subunit composition. Furthermore, △nifZ Avl was also similar to OP Av1 at the molybdenum content, EPR signal (g≈4.3, 3.65 and 2.01), and the molar extinction coefficient (△ε) of circular dichroism (CD)at 660 nm region. All of these indicated that, besides having the same α2β2 composition as OP Av1, the △nifZ Av1 also contained equal amount of reductive FeMoco in the spin state of S=3/2 to OP Av1. However, the iron content and substrate (C2H2, H^ and N2)-reduction activity of △nifZ Av1 were 74% and 46%-50% of those of OP Av1, respectively. Furthermore, the △ε at around 450 nm, which reflects P-cluster in Av1, was obviously lower than that of OP Av1. It suggested that the difference between △nifZ Avl and OP Av1 resulted from P-cluster rather than FeMoco, and from the half number of P-cluster in △nifZ Av1, but the composition or redoxstate of P-cluster in △nifZ Av1 were not changed. Thus it could propose that △nifZ Av1 is composed of two different αβsubunit pairs. One is a FeMoco-and P-cluster-containing pair, and the other is a P-cluster-deficient but FeMoco-containing pair. Since the deletion of nifZ gene leads to the deficiency of only one of two P-clusters in a α2β2 tetramer, the assembly of P-cluster may not simply depend on one gene product, and so a possible mechanism of NifZ is supposed here.     

Variation of soil Δδ13C values in Xifeng loess-paleosol sequence and its paleoenvironmental implication

The carbon isotopic compositions of soil organic matter （SOM） and total carbonate （TC） in Xifeng Ioess-paleosol sequence have been studied. The δ^13CsoM values vary from -23.8‰ to -20.2‰, which are higher in interglacial than in glacial stages. Contrary to δ^13Csoi values, the δ^13CTc values vary from -8.5‰ to -3.6‰ and are lower in interglacial than in glacial stages. The differences （△δ^13C） between the δ^13CsoM and δ^13CTc values vary from 14.1‰ to 19.4‰. Our results from the Xifeng loesspaleosol sequence indicate that the △δ^13C values represent the ratio of primary carbonate （PC） to secondary carbonate （SC）. The △δ^13C values were high in the loess stages, and the maximal PC-to-SC ratio can reach 6：4. But in the paleosol stages, the △δ^13C values were low, with a small proportion of PC. The △δ^13C values in Ioess-paleosol sequence also indicate the contributions of the dust to the loess sediment in the Chinese Loess Plateau because the dust contains the PC.     

Standard molar enthalpy of formation of morin studied by rotating-bomb combustion calorimetry

Flavonols are plant pigments that are ubiquitous in nature. Morin and other related plant flavonols have come into recent prominence because of their usefulness as anticancer, anti-tumor, anti-AIDS, and other important therapeutic activities of significant potency and low systemic toxicity. The heat of combustion of morin (molecular formula, C₁₅H₁₀O₇·H₂O) in oxygen was measured by a rotating-bomb type combustion calorimeter, the standard molar enthalpy of combustion of morin at T = 298.15 K was determined to be Δ_c H _m^⦵ (C₁₅H₁₀O₇·H₂O, s) = −(5 937.99 ± 2.99) kJ · mol⁻¹. The derived standard molar enthalpy of the formation of morin in solid powder state at T = 298.15 K, Δ_f H _m^⦵ (C₁₅H₁₀O₇·H₂O, s), was −(1 682.12 ± 3.58) kJ · mol⁻¹, which provide an accurate data of the stability of morin to the pharmacy and pharmacology. Biography: HOU Hanna(1956–), female, Visiting researcher, Associate professor of Hubei University of Education, research direction: thermochemistry.     

Determination of free energy of protein folding on liquid-solid interface

Based on the fact that the stoichiometric displacement model for retention of solute and the total adsorption free energy of solute on a solid surface can be divided into two components, net adsorption and net desorbed energies, a new principle and an equation for calculating the free energy of protein folding, △△GF, on the solid surface are proposed. With high-performance hydrophobic interaction chromatography (HPHIC), an experimental method for determining the △△GF is established. Lysozyme and α-amylase have been selected as examples to test the new method, and their △△GF on the HPHIC stationary phase surface are found to be much higher than that reported from a solution. In addition, the △△GF of the two proteins are found to increase with the concentration of denaturing agent employed. The average standard deviations, ±4.7% for lysozyme and ±3.0% for α-amylase, indicate that the new method has a satisfactory reproducibility and reliability.     

On the Pólya conjecture and the weak Weyl-Berry conjecture

The Pólya conjecture and its connection with the weak Weyl-Berry conjecture are studied Specifically let Ω⊆R ⁿ (n≥1) be a non-empty bounded open set with boundary ∂Ω. LetN ₀(λ, −Δ,Ω) be the Dirichlet counting function and φ(λ) the associated Weyl term. If the interior Minkowski dimension of ∂Ω is δ∈[n−1,n], then under certain realisable conditions we prove that for λ sufficiently large the Pólya conjecture φ(λ) −N ₀(λ,−Δ,Ω)≥0 is true. Under related conditions we also prove thatϕ(λ)−N ₀(λ,−Δ, Ω)≈λ^5/2, as λ→+∞. That is, the Weak Weyl-Berry conjecture is true. Similar results are obtained for the Neumann counting function. Partially supported by the National Natural Science Foundation of China and the Royal Society of London Chen Hua: born in March 8, 1956, Professor     

Kinetic study of the hydrocarbon generation from marine carbonate source rocks characterization of products of gas and liquid hydrocarbon

The kinetic parameters of hydrocarbon generation from the marine carbonate source rocks were determined and calibrated through kinetic simulating experiment. The kinetic parameters of hydrocarbon generation then were extrapolated to geological condition by using the relative software. The result shows that gaseous hydrocarbons (C_1, C_2, C_3, C_(4-5)) were generated in condition of 150℃相似文献