The regulatory mechanisms in cellular signaling systems have been studied intensively from the viewpoint that the malfunction of the regulation is thought to be one of the substantial causes of cancer formation. On th...The regulatory mechanisms in cellular signaling systems have been studied intensively from the viewpoint that the malfunction of the regulation is thought to be one of the substantial causes of cancer formation. On the other hand, it is rather difficult to develop the theoretical framework for investigation of the regulatory mechanisms due to their complexity and nonlinearity. In this study, more general approach is proposed for elucidation of characteristics of the stability in cellular signaling systems by construction of mathematical models for a class of cellular signaling systems and stability analysis of the models over variation of the network architectures and the parameter values. The model system is formulated as regulatory network in which every node represents a phosphorylation-dephosphorylation cyclic reaction for respective constituent enzyme. The analysis is performed for all variations of the regulatory networks comprised of two nodes with multiple feedback regulation loops. It is revealed from the analysis that the regulatory networks become mono-stable, bi-stable, tri-stable, or oscillatory and that the negative mutual feedback or positive mutual feedback is favorable for multi-stability, which is augmented by a negatively regulated node with a positive auto-regulation. Furthermore, the multi-stability or the oscillation is more likely to emerge in the case of low value of the Michaelis constant than in the case of high value, implying that the condition of higher saturation levels induces stronger nonlinearity in the networks. The analysis for the parameter regions yielding the multi-stability and the oscillation clarified that the stronger regulation shifts the systems toward multi-stability.展开更多
α,α'-Dicinnamoyl ketene cyclic S, S-acetals 4 were reacted with ethylenediamine to afford α,α'-dicinnamoyl ketene cyclic N,N-acetals 5. This process provides a new method for thesynthesis of 5 in high yiel...α,α'-Dicinnamoyl ketene cyclic S, S-acetals 4 were reacted with ethylenediamine to afford α,α'-dicinnamoyl ketene cyclic N,N-acetals 5. This process provides a new method for thesynthesis of 5 in high yield under mild conditions.展开更多
The title compounds 3 and 4 condensed with aromatic aldehydes to give a--aroylsicinnamoyl ketene cyclic dithioacetals 5 and 6 with sodium ethoxide as the base. The stereochemistryofs and 6 was assigned as E-configurat...The title compounds 3 and 4 condensed with aromatic aldehydes to give a--aroylsicinnamoyl ketene cyclic dithioacetals 5 and 6 with sodium ethoxide as the base. The stereochemistryofs and 6 was assigned as E-configuration by 1H NMR.展开更多
The redox reaction of gold III chloride in acid solutions has been electro-chemically investigated using a cyclic voltammetry technique. This paper emphasizes the current and potential sites at which gold III chloride...The redox reaction of gold III chloride in acid solutions has been electro-chemically investigated using a cyclic voltammetry technique. This paper emphasizes the current and potential sites at which gold III chloride is reduced in hydrochloric acid that is vital to electrochemical evaluation of gold recovery. The solutions were prepared by reacting HCl with AuCl3 in various concentrations thus 30 and 60 mg/L AuCl3 in 0.1 and 0.5 M HCl, respectively. Solutions of 0.1 and 0.5 M HCl containing 0, 30 and 60 mg/L AuCl3, respectively were tested for possible reduction and oxidation reactions by cyclic voltammogram experiment using a glassy carbon, a saturated calomel and a platinum wire mesh as working, reference and counter electrodes, respectively. The results showed no peak in the case of the absence of AuCl3 in the solutions, but appreciable cathodic and anodic peaks for the reduction and oxidation of various concentrations of AuCl3 in acid solutions. The reaction between AuCl3 and HCl was found to be reversible because the ratio of oxidation peak current and reduction peak current was 1. The concentration of AuCl-4 on the surface of the working electrode at the reduction site for each AuCl3 concentration using Nernst equation was 1.22 × 109 ppm and 2.44 × 109 ppm. The reduction potentials were independent of concentration, while the current was highly dependent of concentration.展开更多
文摘The regulatory mechanisms in cellular signaling systems have been studied intensively from the viewpoint that the malfunction of the regulation is thought to be one of the substantial causes of cancer formation. On the other hand, it is rather difficult to develop the theoretical framework for investigation of the regulatory mechanisms due to their complexity and nonlinearity. In this study, more general approach is proposed for elucidation of characteristics of the stability in cellular signaling systems by construction of mathematical models for a class of cellular signaling systems and stability analysis of the models over variation of the network architectures and the parameter values. The model system is formulated as regulatory network in which every node represents a phosphorylation-dephosphorylation cyclic reaction for respective constituent enzyme. The analysis is performed for all variations of the regulatory networks comprised of two nodes with multiple feedback regulation loops. It is revealed from the analysis that the regulatory networks become mono-stable, bi-stable, tri-stable, or oscillatory and that the negative mutual feedback or positive mutual feedback is favorable for multi-stability, which is augmented by a negatively regulated node with a positive auto-regulation. Furthermore, the multi-stability or the oscillation is more likely to emerge in the case of low value of the Michaelis constant than in the case of high value, implying that the condition of higher saturation levels induces stronger nonlinearity in the networks. The analysis for the parameter regions yielding the multi-stability and the oscillation clarified that the stronger regulation shifts the systems toward multi-stability.
文摘α,α'-Dicinnamoyl ketene cyclic S, S-acetals 4 were reacted with ethylenediamine to afford α,α'-dicinnamoyl ketene cyclic N,N-acetals 5. This process provides a new method for thesynthesis of 5 in high yield under mild conditions.
文摘The title compounds 3 and 4 condensed with aromatic aldehydes to give a--aroylsicinnamoyl ketene cyclic dithioacetals 5 and 6 with sodium ethoxide as the base. The stereochemistryofs and 6 was assigned as E-configuration by 1H NMR.
文摘The redox reaction of gold III chloride in acid solutions has been electro-chemically investigated using a cyclic voltammetry technique. This paper emphasizes the current and potential sites at which gold III chloride is reduced in hydrochloric acid that is vital to electrochemical evaluation of gold recovery. The solutions were prepared by reacting HCl with AuCl3 in various concentrations thus 30 and 60 mg/L AuCl3 in 0.1 and 0.5 M HCl, respectively. Solutions of 0.1 and 0.5 M HCl containing 0, 30 and 60 mg/L AuCl3, respectively were tested for possible reduction and oxidation reactions by cyclic voltammogram experiment using a glassy carbon, a saturated calomel and a platinum wire mesh as working, reference and counter electrodes, respectively. The results showed no peak in the case of the absence of AuCl3 in the solutions, but appreciable cathodic and anodic peaks for the reduction and oxidation of various concentrations of AuCl3 in acid solutions. The reaction between AuCl3 and HCl was found to be reversible because the ratio of oxidation peak current and reduction peak current was 1. The concentration of AuCl-4 on the surface of the working electrode at the reduction site for each AuCl3 concentration using Nernst equation was 1.22 × 109 ppm and 2.44 × 109 ppm. The reduction potentials were independent of concentration, while the current was highly dependent of concentration.
文摘目的探究绿原酸(chlorogenic acid,CGA)氧化形成的CGA醌与氨基酸侧链基团在不同pH条件下的反应效率,为CGA与蛋白质共价互作反应位点的调控提供理论依据。方法利用循环伏安法研究了酸性(pH 5.0)、中性(pH 7.0)和碱性(pH 8.0)条件下CGA与氨基酸侧链基团的反应效率,采用超高效液相色谱-四极杆飞行时间串联质谱法(ultra performance liquid chromatography-quadrupole time of flight-tandem mass spectrometry,UPLC-QTOF-MS/MS)对反应产物进行结构鉴定。结果在pH7.0、扫描速率10mV/s,0.20mmol/LCGA与10.00mmol/L封闭α-氨基的氨基酸的反应效率依次为Nα-乙酰-L-半胱氨酸(~100.00%)≈Nα-乙酰-L-色氨酸(~100.00%)>Nα-乙酰-L-酪氨酸(39.20%±2.19%)>Nα-乙酰-L-赖氨酸(10.25%±0.83%)>Nα-boc-L-组氨酸(~0.00%)≈Nα-乙酰-L-精氨酸(~0.00%);在其他反应条件相同的情况下,缩小扫描电压范围至-0.4~0.4V,CGA与Nα-乙酰-L-半胱氨酸、Nα-乙酰-L-色氨酸及Nα-乙酰-L-酪氨酸的共价互作效率分别为~100%、12.83%±1.16%及~0%;pH 7.0或8.0时,GCA与氨基酸残基的共价互作效率高于pH 5.0;CGA醌与Nα-乙酰-L-赖氨酸、Nα-乙酰-L-精氨酸的反应产物以氧化态的醌-氨基酸形式存在,而CGA醌与Nα-乙酰-L-半胱氨酸、Nα-boc-L-组氨酸、Nα-乙酰-L-色氨酸的反应产物以还原态的酚-氨基酸形式存在。结论CGA氧化形成的CGA醌可与蛋白质中半胱氨酸、色氨酸、赖氨酸、组氨酸及精氨酸残基发生反应,其中半胱氨酸残基是CGA醌与蛋白质共价互作的主要位点,可通过调整食品体系的pH和绿原酸醌浓度实现绿原酸-蛋白质共价互作位点的调控。
