On the interaction of bovine serum albumin with ionic surfactants: temperature induced EPR changes of a maleimide nitroxide reflect local protein dynamics and probe solvent accessibility

The interaction of bovine serum albumin (BSA) with the ionic surfactants sodium dodecylsulfate (SDS, anionic), cetyltrimethylammonium chloride (CTAC, cationic) and N-hexadecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (HPS, zwitterionic) was studied by electron paramagnetic resonance (EPR) spectroscopy of spin label covalently bound to the single free thiol group of the protein. EPR spectra simulation allows to monitor the protein dynamics at the labeling site and to estimate the changes in standard Gibbs free energy, enthalpy and entropy for transferring the nitroxide side chain from the more motionally restricted to the less restricted component. Whereas SDS and CTAC showed similar increases in the dynamics of the protein backbone for all measured concentrations, HPS presented a smaller effect at concentrations above 1.5mM. At 10mM of surfactants and 0.15 mM BSA, the standard Gibbs free energy change was consistent with protein backbone conformations more expanded and exposed to the solvent as compared to the native protein, but with a less pronounced effect for HPS. In the presence of the surfactants, the enthalpy change, related to the energy required to dissociate the nitroxide side chain from the protein, was greater, suggesting a lower water activity. The nitroxide side chain also detected a higher viscosity environment in the vicinity of the paramagnetic probe induced by the addition of the surfactants. The results suggest that the surfactant-BSA interaction, at higher surfactant concentration, is affected by the affinities of the surfactant to its own micelles and micelle-like aggregates. Complementary DLS data suggests that the temperature induced changes monitored by the nitroxide probe reflects local changes in the vicinity of the single thiol group of Cys-34 BSA residue.     

不确定混沌系统的混合投影同步

本文研究了一类不确定混沌(超混沌)系统的混合投影问题.利用自适应方法和Lyapunov稳定性理论,获得了两个恒同或不同混沌系统实现混沌投影同步的一般方法.最后,数值仿真的结果验证了方法的有效性和鲁棒性.     

Interaction of giant extracellular Glossoscolex paulistus hemoglobin (HbGp) with zwitterionic surfactant N-hexadecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (HPS): effects of oligomeric dissociation

The present work focuses on the interaction between the zwitterionic surfactant N-hexadecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (HPS) and the giant extracellular hemoglobin of Glossoscolex paulistus (HbGp). Electronic optical absorption, fluorescence emission and circular dichroism spectroscopy techniques, together with Gel-filtration chromatography, were used in order to evaluate the oligomeric dissociation as well as the autoxidation of HbGp as a function of the interaction with HPS. A peculiar behavior was observed for the HPS–HbGp interaction: a complex ferric species formation equilibrium was promoted, as a consequence of the autoxidation and oligomeric dissociation processes. At pH 7.0, HPS is more effective up to 1 mM while at pH 9.0 the surfactant effect is more intense above 1 mM. Furthermore, the interaction of HPS with HbGp was clearly less intense than the interaction of this hemoglobin with cationic (CTAC) and anionic (SDS) surfactants. Probably, this lower interaction with HPS is due to two factors: (i) the lower electrostatic attraction between the HPS surfactant and the protein surface ionic sites when compared to the electrostatic interaction between HbGp and cationic and anionic surfactants, and (ii) the low cmc of HPS, which probably reduces the interaction of the surfactant in the monomeric form with the protein. The present work emphasizes the importance of the electrostatic contribution in the interaction between ionic surfactants and HbGp. Furthermore, in the whole HPS concentration range used in this study, no folding and autoxidation decrease induced by this surfactant were observed. This is quite different from the literature data on the interaction between surfactants and tetrameric hemoglobins, that supports the occurrence of this behavior for the intracellular hemoglobins at low surfactant concentration range. Spectroscopic data are discussed and compared with the literature in order to improve the understanding of hemoglobin–surfactant interaction as well as the acid isoelectric point (pI) influence of the giant extracellular hemoglobins on their structure–activity relationship.     

Two Novel Isomers of HPS3 System

Two new isomers of HPS3 system, FIP(S)S2 and HSSPS, are predicted by means of B3LYP method with 6-311 G(3df,3pd) basis set. The two isomers can isomerize into thermodynamically the most stable species HSPS2, which have been experimentally identified,with relatively higher reaction barriers. In view of their higher thermodynamical and kinetic stability and the experimental observation for I-IP(O)O2 and HOOPO in previous study, we can reasonably believe that the two species can be spectrosymmetrically characterized in future experiments.     

Structures and stabilities of HPS_2 isomers

The potential energy surface of HPS2 system containing nine isomers and fifteen transition states is obtained at MP2/6-311++G(d, p) and QCISD(t)/6-311++G(3df, 2p)(single-point) levels. On the potential energy surface, the lowest-lying frans-HSPS(EI) is found to be thermodynami-cally the most stable isomer followed by cis-HSPS(E2) and HP(S)S(C2v, E3) at 3.43 and 14.17 kJ/mol higher, respectively. The computed results show that species E1, E2, E3, stereo HP(S)S(Cs, E4) with PSS three-membered ring, isomers trans-HPSS(E5) and cis-HPSS(E6) which coexist with E4 are kinetically stable isomers. The products E6 and E5 in the reaction of HP with S2 can be isomerized into higher kinetic stable isomer E4 with 65.75 and 71.73 kJ/mol reaction barrier height, respectively. The predicated results may correct the possible inaccurate conclusion in that the product was experimentally assigned as isomer cis-HPSS(E6).     

新课标“硅及其化合物”定位的嬗变与教学重构——基于HPS模式改进的教学设计

《普通高中化学课程标准(2017年版) 》中明确提出化学学科核心素养,完成了三维目标的迭代。硅及其化合物相关内容发生了较大变化,虽然知识层面要求降低,但是作为认识对象和感性认识素材的要求却有所提高。这种定位的嬗变,势必要求进行主题教学的重构。结合化学发展史以及改进的HPS教学模式,进行了初步的教学实践探索。     

基于核心素养的HPS教学实践——以“甲烷”为例

基于化学核心素养,以“打开第二自然界的大门”开启甲烷的科学探究与体验之旅,在“历史线”“活动线”“知识线”等3条认知与体验路线中,经历科学概念的形成过程,实现对“稻草变黄金”科学本质的理解,有效地将HPS教育与化学核心素养结合起来,使学生体会化学发展的过程与方法,感受化学的学科魅力和发展成就,以提高学生的学习兴趣。     

新冠疫情与科学教育*——国外与新冠疫情相关的科学教育研究述评

新冠疫情是一个全球性的历史事件,科学教育也深受新冠疫情的影响。对新冠疫情爆发以来收录在Scopus数据库中的49篇有关科学教育的文章进行分类综述,主要围绕:新冠疫情下远程科学教育的机遇与挑战;新冠疫情:一个重要的社会性科学议题;HPS在新冠疫情时代对科学教育的贡献;由新冠疫情反思科学教育标准与科学素养;新冠疫情下的非正规科学教育与可持续教育等5个方面展开述评,总结新冠疫情中科学教育的经验以反思科学教育、前瞻后疫情时代的科学教育。     

光敏感核不育水稻愈伤组织的超低温保存和冻后再生植株的形成

研究了光敏感核不育水稻的悬浮细胞及愈伤组织的低温贮藏方法．实验采用１０％ＤＭＳＯ＋０．５ｍｏｌ·Ｌ－１山梨醇作冰冻保护剂，降温速率采用１．０℃·ｍｉｎ－１或０．５℃·ｍｉｎ－１，ＴＴＣ法测试的细胞存活率最高可达８５．９％，冻后材料经１５ｄ左右即可在暗培养条件下观察恢复生长的情况．３０ｄ后把长势良好的愈伤组织块转移至分化培养基中，来源于悬浮细胞团的绿苗分化率为１０．０％，愈伤组织的则为６６．６％．     

应用FTIR分析过量表达HPS/PHI转基因与野生型天竺葵叶片在甲醛胁迫下的生理特性差异

6-磷酸己酮糖合成酶(HPS)和6-磷酸果糖异构酶(PHI)是细菌同化甲醛的关键酶。13 C-NMR分析结果说明在天竺葵叶绿体中过量表达HPS/PHI融合蛋白可把RuMP途径整合成卡尔文循环的一个支路,在转基因天竺葵叶绿体中创造一个甲醛光合同化途径。运用FTIR技术分析过量表达HPS/PHI转基因与野生型天竺葵在甲醛胁迫下体内各物质含量的变化规律及光谱表征,考察FTIR能否成为一种鉴定有甲醛光合同化途径的转基因植物与野生型植物表型差异的新方法。分别用4mmol.L-1甲醛处理野生型和转基因植物0,1,2,3,4d,通过对两种植物经甲醛处理不同时间后各光谱特征的比较分析发现,用4mmol.L-1甲醛处理4d后转基因植物中的碳水化合物、蛋白质、脂肪族化合物等的含量明显高于野生型植物。这可能是由于安装HPS/PHI甲醛光合同化途径后使转基因植物同化代谢甲醛的能力更强,能将更多的甲醛固定为6-磷酸果糖,然后进入各种同化途径用于合成细胞内的各种组份所致,说明FTIR可作为一种鉴定有甲醛光合同化途径的转基因天竺葵与野生型天竺葵表型差异的新方法。