近红外光刺激神经细胞钙离子光激活

钙离子(Ca~(2+))是细胞的主要信息传输通道,研究Ca~(2+)激活对阐述亚细胞层次生物过程具有重要意义,光激活是目前研究细胞内Ca~(2+)传输和控制的主要方式之一.本文利用近红外脉冲激光刺激标记有金纳米棒(gold nanorods, GNRs)的人神经母细胞瘤细胞(SH-SY5Y)的Ca~(2+)信号传导,并利用钙离子指示剂(Fluo-4,AM)对其进行双光子荧光成像.实验采用功率为0.5 m W,波长为800 nm的激发光,平均10 s就可实现Ca~(2+)光激活,标记GNRs的神经细胞Ca~(2+)释放速度是未标记GNRs的6倍.研究结果表明GNRs通过局域表面等离子体共振将脉冲激光瞬间转化为热量,改变膜电容,使细胞膜去极化并引发动作电位,使细胞外Ca~(2+)流入,证明了借助GNRs来增强神经细胞Ca~(2+)激活的可行性,为神经细胞离子通道研究提供了一种光学手段.     

红外光谱、 XPS分析比较Ca~(2+),Fe~(3+)对石英的活化机理

铁精矿浮选脱硅过程中,矿浆中的难免阳离子(Ca~(2+), Fe~(3+))对阴离子捕收石英的可浮性有重要影响,而搞清难免阳离子对含石英等脉石矿物的活化机制,对解决超纯铁精矿脱硅技术难题有重要意义。目前关于捕收剂对石英吸附结构的研究较多,而难免离子活化石英的吸附结构及吸附强弱发生机制研究较少。因此,采用红外光谱、 XPS检测手段对难免离子(Ca~(2+), Fe~(3+))活化石英浮选进行光谱学表征,同时解析石英中含氧官能团及难免离子的赋存形式,分析其活化机理。红外检测结果表明,在适宜的pH值条件下, Ca~(2+)和Fe~(3+)的加入,对SDS捕收剂浮选石英均有活化作用,而活化后的石英与SDS作用,其间既包括物理吸附,也包括化学吸附;而且Fe~(3+)活化作用下的Si—O特征峰红移波数大于Ca~(2+)活化作用下的红移波数,是由于Ca~(2+)活化石英是单氧-硅键作用,其键能小,吸附弱,而Fe~(3+)活化石英是双氧-硅键作用,其键能大,吸附强。XPS测试表明, Fe~(3+)活化石英的结合能(Fe(2p)结合能为711.16 eV)强于Ca~(2+)活化石英的结合能(Ca(2p)结合能为346.93 eV),其Si(2s)和Si(2p)结合能化学位移量更大,说明Fe~(3+)活化作用下其化学吸附更稳定、更致密,且产生两个活性位点,在石英表面生成稳定的Fe基六元环螯合物;而对比Fe~(3+)和Ca~(2+)活化作用下的化学吸附不稳定、不致密,在石英表面生成Ca基链状络合物。综合红外光谱、 XPS分析表明, Fe~(3+)比Ca~(2+)有更强的活化作用,同时加强了药剂与石英表面的化学吸附和物理吸附,更利于活化石英的浮选。     

磷酸盐、氟磷酸盐和氟化物玻璃中离子的光谱和波谱研究Ⅱ:Mn~(2+)、Fe~(3+)

在前文[Ⅰ]的基础上对Mn~(2+)的吸收光谱和荧光光谱进行了研究。结合ESR实验结果,分析了Mn~(2+)的配位状况,认为在这三种玻璃中,Mn~(2+)都处于八面体配位中。理论计算与实验结果相符。对以Fe~(3+),Fe~(2+)两种稳定价态存在的铁离子吸收光谱进行了研究。结合其ESR波谱,认为Fe~(3+)也处于八面体中.     

金属离子Li~+,Na~+,K~+,Ca~(2+),Ba~(2+)掺杂Lu_2O_3:Pr~(3+)荧光粉的制备及发光特性研究

用高温固相法制备了Lu_2O_3∶x Pr~(3+)与Lu_2O_3∶0.1%Pr~(3+),y M(M=Li~+,Na~+,K~+,Ca~(2+),Ba~(2+))荧光粉。用XRD对其结构进行表征,测量了激发光谱、发射光谱和发光衰减曲线,分析了金属离子Li~+、Na~+、K~+、Ca~(2+)、Ba~(2+)掺杂对Lu_2O_3∶Pr~(3+)样品发光强度及荧光寿命的影响。结果显示:掺杂金属离子后的样品仍为纯Lu_2O_3立方晶相结构;与Lu_2O_3∶0.1%Pr~3样品在632 nm处的发光强度比较,分别掺杂12%的Li~+、8%的Na~+、8%的K~+获得样品的发光强度提高了7.32,4.11,2.55倍,掺杂了Ca~(2+)和Ba~(2+)的样品发光强度均减弱;与Lu_2O_3∶0.1%Pr~(3+)样品荧光寿命比较,掺杂Li~+、Na~+、K~+、Ca~(2+)、Ba~(2+)获得的样品~1D_2能级荧光寿命均缩短。     

磁化水防垢机理的探索

磁化水防垢效果与磁场处理条件有一定的关系,但井不是唯一决定的因素,水质也起了重要作用. 一、水质分析 各种天然水内都溶解有一定数量的杂质,其主要成份是钙、镁等盐类.所谓硬度就是指这两种盐类的含量.它们在水中常以两种形式存在: (1)钙、镁的碳酸盐:有碳酸钙(CaCO3)、碳酸镁(MgCO3)、重碳酸钙[Ca(HCO3)2]和重碳酸镁[Mg(HCO3)2]等.这些盐形成的硬度叫做碳酸盐硬度. (2)钙、镁的非碳酸盐:有硫酸钙(CaSO4)、硫酸镁(MgSO4)、氯化钙(CaCl2)、氯化镁(MgCl2)和硅酸钙CaSiO3等.这些盐形成的硬度叫做非碳酸盐硬度. 有的天然水中还含…     

Hes1调控 AKT-MDM2-p53-PTEN通路的一种物理机制

基于Hill动力学与Michaelis-Menten方程,建立理论模型研究发状分裂相关增强子1(hairy and enhancer of split 1,Hes1)调控蛋白激酶B (Protein Kinase B,AKT)-鼠双微体2 (Murine Double Minute2,MDM2)-抗癌基因p53(p53)-第10号染色体缺失的磷酸酶及张力蛋白同源的基因(Phosphatase and tensin homolog deleted on chromosome ten,PTEN)通路的一种物理机制.研究发现,Hes1通过与PTEN结合抑制PTEN表达,并调控AKT信号.表明了Hes1蛋白的合成,以及Hes1与PTEN相互作用调控AKTMDM2-p53-PTEN通路信号,将会有效地控制细胞结果 . Hes1作为AKT-MDM2-p53-PTEN信号通路中上游调节的重要因素,还可以在一定程度上通过影响p53蛋白功能,改变p53对肿瘤的抑制性.理论结果可用于预测Notch通路信号异常诱导的致癌性,并进一步揭示了Notch信号通路影响细胞AKT-MDM2-p53-PTEN通路的激活...     

GB1与金属离子相互作用的NMR研究（英文）

G群链球菌G蛋白的B1结构域——GB1蛋白,常被用作发展体外及体内基于顺磁核磁共振(NMR)的蛋白质结构测定方法的研究模型.为确保赝接触化学位移(PCS)、顺磁弛豫增强(PRE)等顺磁约束数据的准确性,了解GB1和金属离子,尤其是顺磁离子的相互作用非常必要.然而GB1和二价金属离子以及镧系金属离子的相互作用并不十分清楚.本文利用NMR波谱研究了GB1和镧系金属离子以及多种二价金属离子的相互作用.我们发现GB1和镧系金属离子之间存在弱特异性相互作用,和Mn~(2+)、Cu~(2+)以及Co~(2+)等顺磁二价离子弱结合,但不与Ca~(2+)、Mg~(2+)以及Zn~(2+)等抗磁二价离子结合.该研究表明在GB1上链接顺磁探针时,应使用与固有位点结合常数差异明显的顺磁标签以获取正确的PRE数据.     

二价金属离子与YycFN相互作用的NMR研究

YycGF最早发现于枯草芽孢杆菌,是与细胞存活密切相关的双组分信号转导系统存在于少量低鸟嘌呤和胞嘧啶(G+C)含量的革兰氏阳性菌中,包括金黄色葡萄球菌和肺炎链球菌等人类病原菌,在外界环境刺激下,胞膜上的组氨酸激酶YycG通过自身组氨酸磷酸化活化,将磷酸根转移至反应调节蛋白YycF的N端调节区(YycF_N)使之磷酸化,调控下游基因表达,实现特定细胞应答反应.二价金属离子在双组分信号转导系统反应调节蛋白的磷酸化过程中起着非常关键的作用,但它们与YycF_N相互作用的机制尚不清楚.该文利用液体核磁共振(NMR)方法研究了Ca~(2+)、Mg~(2+)两种离子与YycF_N的相互作用,对详细的相互作用界面进行了分析,并计算了Ca~(2+)、Mg~(2+)与YycF_N的解离常数(K_d).发现金属离子的关键作用位点是Asp9、Asp16和Asp53等残基,蛋白的整体构象也发生了一定变化,为阐明二价金属离子在反应调节蛋白信号转导过程中的作用机制提供了重要线索.     

Ca~(2+)掺杂对SmFeO_3的介电、铁磁特性及磁相变温度的影响

采用固相反应法制备Sm_(1-x)Ca_xFeO_3(x=0,0.1,0.2,0.3)样品,研究Ca~(2+)掺杂对SmFeO_3介电性能、铁磁性及磁相变温度的影响.X射线衍射图谱分析表明:所有样品的主衍射峰与SmFe03相符合且具有良好的晶体结构.随着x的增加,SmFeO_3样品的晶粒尺寸由原来的0.5μm逐渐增大到2μm.当f=1 kHz时,Sm_(1-x)Ca_xFeO_3(x=0.1,0.2,0.3)样品的ε_r分别是SmFe03的5倍、3倍和2.6倍,而tgσ增大一个数量级.在3T磁场作用下,SmFe03样品的M-H呈线性,随着x的增加,M-H逐渐趋向饱和,Sm_(1-x)Ca_xFeO_3(x=0.1,0.2,0.3)样品的M_r分别是SmFeO_3的20倍、31倍和68倍.X射线光电子能谱分析表明:Fe~(2+)和Fe3+共存于Sm_(1-x)Ca_xFeO_3样品中,Fe~(2+)/Fe~(3+)比例随着x的增加而增大,证明Ca~(2+)掺杂增加了Fe~(2+)的含量,形成Fe~(2+)—O~(2-)—Fe~(3+)超交换作用,增强SmFe03的铁磁特性.测量了Sm_(1-x)Ca_xFeO_3样品在外加磁场为1000 Oe(1 Oe=79.5775 A/m)的M-T变化关系,观测到其自旋重组温度(T_(SR))和尼尔温度(T_N)分别为438 K和687 K,发现SmFe03样品的T_(SR)和T_N均随着x的增加向低温方向移动,当x=0.3时,自旋重组现象消失.这主要是SmFeO_3样品磁结构的稳定性和Fe~(3+)—O~(2-)—Fe~(3+)及Sm~(3+)—O~(2-)—Fe~(3+)超交换三者共同作用的结果.     

胰岛素异常积累诱发转移性致癌通路激活的模型化研究

本文基于质量作用动力学与Michaelis-Menten方程建立理论模型,研究胰岛素异常积累诱发转移性致癌通路激活特性.理论模型考虑胰岛素通过激活PI3K-AKT-mTOR信号传导途径调控AKT-MDM2-P53-PTEN信号通路,以及胰岛素异常积累诱发JAK2/STAT5转移性致癌通路信号激活特性.研究发现,在JAK2/STAT5通路信号传导过程中,酪氨酸磷酸化的STAT5单体迅速转化为STAT5二聚体.随着异常胰岛素积累的增加,磷酸化的STAT5二聚体、酪氨酸磷酸化STAT5二聚体表达水平进一步提升.由此表明了,异常胰岛素积累诱发JAK2/STAT5转移性致癌通路激活.胰岛素异常积累通过直接提升JAK2的表达,导致了AKT的表达异常升高,致使细胞糖原代谢紊乱,P53蛋白抑癌作用降低,促进的癌症的发生发展. miR-378作为非常重要的抑癌因子,在JAK2/STAT5转移性致癌信号通路信号作用下,miR-378的抑癌效应被明显削弱,由此也表明了转移性癌症的复杂性.通过分析模型中各参数的敏感性,确定了JAK2/STAT5信号通路创设致癌微环境的灵敏性.本文理论结果符合实验理论观测,可为...     

Dual mechanisms of Bcl-2 regulation in IP3-receptor-mediated Ca2+ release: A computational study

Inositol 1,4,5-trisphosphate receptors (IP₃R)-mediated calcium ion (Ca²⁺) release plays a central role in the regulation of cell survival and death. Bcl-2 limits the Ca²⁺ release function of the IP₃R through a direct or indirect mechanism. However, the two mechanisms are overwhelmingly complex and not completely understood. Here, we convert the mechanisms into a set of ordinary differential equations. We firstly simulate the time evolution of Ca²⁺ concentration under two different levels of Bcl-2 for the direct and indirect mechanism models and compare them with experimental results available in the literature. Secondly, we employ one- and two-parameter bifurcation analysis to demonstrate that Bcl-2 can suppress Ca²⁺ signal from a global point of view both in the direct and indirect mechanism models. We then use mathematical analysis to clarify that the indirect mechanism is more efficient than the direct mechanism in repressing Ca²⁺ signal. Lastly, we predict that the two mechanisms restrict Ca²⁺ signal synergistically. Together, our study provides theoretical insights into Bcl-2 regulation in IP₃R-mediated Ca²⁺ release, which may be instrumental for the successful development of therapies to target Bcl-2 for cancer treatment.     

AuCl3催化炔酮分子内环化反应的机理

采用密度泛函理论的B3LYP方法研究炔酮发生分子内环化生成菲衍生物的反应机理.结果表明：在无催化剂和AuCl₃催化剂作用下,反应均可通过[2+2]和[6+2]途径生成产物.无催化剂时,两条途径控制步骤的能垒都较高,但是[2+2]途径的能垒比[6+2]途径的低32.01 kJ·mol^-1,故反应主要通过[2+2]途径进行.在AuCl₃催化作用下,反应的优势途径为[2+2]途径,其能垒为137.05 kJ·mol^-1.比较活化能发现,AuCl₃催化剂明显地降低了反应能垒,使反应能够顺利进行.     

Confocal calcium imaging with ultraviolet laser- scanning microscopy and indo-1

We developed a newly designed ultraviolet laser-scanning confocal microscopy (UV-LSCM) system and applied it for quantitative confocal imaging of intracellular calcium concentration ([Ca²⁺]_i) with the dual-emission wavelength indicator indo-1. The resolution and contrast of the biological sample images obtained using the current UV system were found to be comparable to those obtained with the conventional visible LSM optics and hence the UV-transmittable optics in our LSM system employing an achromatic objective lens provides appreciable confocality in the UV range. When indo-1 is used with this UV-LSCM system, dual- imaging ratiometric measurement of [Ca²⁺]_i can be easily performed without requiring time-consuming geometrical decalibration of the two simultaneously obtained images. The resulting confocal images allow quantitative analysis of [Ca²⁺]_i in rapidly contractile cardiac cells at a high temporal resolution in line-scan and fast frame-scan modes. The combined use of the UV-LSCM and dual- emission ratiometric indicator is now practical and we anticipate its widespread application in physiological and pathological studies in living cells.     

High-field MRS studies in brain slices

We are applying multi-nuclear high-field (500 MHz) MR spectroscopy of metabolising whole tissue preparations of the mammalian brain to studies on individual components of convulsions, which include prolonged depolarization, metabolic deprivation, and the effects of excitotoxins. The responses of glial cells and neurones can be partially distinguished by following labelling patterns of metabolic intermediates from ¹³C-labelled glucose or acetate (which enters only glial cells). This approach clearly confirmed our earlier indications that the metabolic response to depolarization (40 mM extracellular K⁺) occurs essentially in glial cells. Some evidence for metabolic shuttling between glia and neurones was obtained from the changes in C3/C4 ratios of glutamate and glutamine, and the C2/C3 of GABA. Mechanisms for metabolic support of neurones by glia may be of importance in neuronal protection under such metabolic stress as occurs in epilepsy. Changes in free intracellular divalent cations ([Ca²⁺]_i and [Zn²⁺]_i) were monitored using the ¹⁹F-MRS indicator, 5FBAPTA. Large increases in [Ca²⁺]_i and decreases in PCr were produced by excitotoxins (glutamate and NMDA), depolarization or ischaemia, but intracellular Zn²⁺ appeared only after exposure to the excitotoxins. The NMDA receptor blocker, MK801, removed all of the responses to NMDA, but only prevented the appearance of Zn²⁺ observed with glutamate. These results indicate that the damage caused to neurones by such insults as convulsions is not due simply to the presence of excessive excitotoxic glutamate.     

HOW TO DETERMINE THE NUCLEAR MATRIX ELEMENT IN 2β-Decay?-A DISCUSSION OF PCAC, 2β-DECAY AND DOUBLE-CHARGE EXCHANGE REACTION OF PIONS ON NUCLEI

It is shown that by applying PCAC, the 2β-decay process can be directly related to double-charge-exchange reaction. Therefore, by studying double-charge-exchange reactions one is able to determine the nuclear matrix element of the relevant 2β-decay experimentally. A preliminary analysis has indicated that if the experimental data of forward-angle cross section on Ca⁴⁰ with pion beam at 164 Mev^[9] are used and extrapolated to Ca⁴⁸, then the squared nuclear matrix element thus determined is smaller than that calculated for Ca⁴⁰→Ti⁴⁸+2e^-+2v^[11] by 10⁵～10⁶.     

La3+存在形式对白云鄂博稀选尾矿微晶玻璃性能的影响

选取白云鄂博稀选尾矿和粉煤灰为主要原料, 采用熔铸法制备了0–4 wt%La₂O₃掺杂的CaO-MgO-Al₂O₃-SiO₂系微晶玻璃. 利用DTA, XRD, SEM, TEM+EDS和性能测试手段研究La³⁺在白云鄂博稀选尾矿微晶玻璃中的存在形式及其对该微晶玻璃显微结构、抗折强度和耐腐蚀性的影响. 结果表明, La³⁺以置换固溶方式进入辉石主晶相, 1 wt%的La₂O₃可促进辉石主晶相形成. 超过1 wt%的La₂O₃与基础玻璃组分反应生成Ca₃La₆(SiO₄)₆第二相, 并与辉石相争夺Ca²⁺和Si⁴⁺离子来阻碍辉石相形成. 添加1 wt% La₂O₃的微晶玻璃综合性能最优, 其抗折强度和密度分别为198 MPa和3.18 g/cm³.     

多面体共替代对Sr_2(Al_(1–x) Mg_x)(Al_(1–x) Si_(1+x))O_7:Eu~(2+)晶体结构和发光颜色的影响

采用高温固相法合成Sr_(1.98)(Al_(1–x) Mg_x)(Al_(1–x) Si_(1+x))O_7: 2%Eu~(2+)荧光粉完全固溶体,利用X射线衍射、光致发光光谱和光学显微镜进行晶体结构和发光性能的研究. Sr_2Al_2SiO_7和Sr_2MgSi_2O_7同构化合物中包含[MgO_4]、[SiO_4]和[AlO_4]四面体,较大体积的[MgO_4]和较小体积的[SiO_4],共同替代体积相似的[AlO_4],导致[(Si/Al)O_4]收缩和[(Mg/Al)O_4]膨胀,晶胞参数c减少, a和V增大,使Eu~(2+)周围的环境发生改变,晶体场劈裂程度减小,发射峰位从503 nm蓝移至467 nm,实现发光光谱从绿色(0.2384, 0.3919)到蓝色(0.1342,0.1673)的转变.当x为0时,发射峰的半高宽为120 nm, x从0.25增加到1时,半高宽由89 nm逐渐减小至50 nm,多面体的替代会改变荧光粉的发光性能.     

Synthesis and properties of a new copper(II)-hafnium phosphate Cu0.5Hf2(PO4)3

Phosphates of general formula M_0.5Hf₂(PO₄)₃ with M=Cd²⁺, Ca²⁺, Sr²⁺ and Cu²⁺ were prepared by coprecipitation and characterized by several physical techniques. The compounds containing Cd²⁺, Ca²⁺, Sr²⁺ belong to the Nasicon-type structure, whereas Cu_0.5Hf₂(PO₄)₃ exhibited substantially different DRX patterns. Combined temperature programmed reduction (TPR) and temperature-programmed oxidation (TPO) showed that the copper in Cu_0.5Hf₂(PO₄)₃ was distributed between two energetically different sites in proportions respectively equal to 40 and 60%. Electron Paramagnetic Resonance (EPR) investigations confirmed the TPR/TPO results and revealed that the two sites hosting the Cu²⁺ ions are of orthorhombic symmetry. Moreover, the Cu²⁺ ions might be reduced by hydrogen to Cu⁺. These results were also supported by the UV–visible studies that showed the disappearance, under reducing conditions, of the band corresponding to crystal field transitions of Cu²⁺ ions and the emergence of a new peak attributed to the transitions between (3d)¹⁰ and (3d)⁹(4s)¹ Cu⁺ levels. At the same time, IR spectroscopy confirmed that protons entered the open lattice framework of the material and gave rise to a new protonated phase containing monovalent copper Cu_0.5^IH_0.5Hf₂(PO₄)₃. This redox process was proven to be reversible without any subsequent change in the network of the phosphate.     

The role of polarization of Xe by di- and monovalent cations in Xe NMR studies in zeolite A

We consider the role of polarization in the adsorption of Xe in zeolites of type A by direct comparative analysis of the adsorption isotherms, distributions of occupancies, and ¹²⁹Xe NMR chemical shifts of Xe_n in cages containing Ca_xNa_{12 −2x} ions per alpha cage (x = 0, 1, 2, 3, 5). We find that the qualitative trends in the adsorption isotherms, and in the progressions of Xe_n chemical shifts (for n = 0–8 in cages with x = 0, 1 Ca²⁺ ions and for n = 0–5 in cages with x = 2, 3 Ca²⁺ ions) upon increasing the level of Ca²⁺ ion for Na⁺ ion substitution could only be accounted for by including polarization of the Xe atom by the zeolite framework and its ions. This system, which permits observation of individual Xe_n peaks and of directly comparable adsorption isotherms in several cage types, provides a good model system for the interpretation of the more general case in which only the overall average ¹²⁹Xe NMR chemical shift is observed in open network zeolites, arising from free exchange of Xe among cavities of variable occupancy and variable cation distribution.     

Charge ordering in Eu3S4 determined by the valence-difference contrast of synchrotron X-ray diffraction

Synchrotron X-ray diffraction study for single crystals of Eu₃S₄ has revealed that a Th₃P₄-type structure transforms to a charge-ordered one at T_c=188.5 K. The crystal structures of Eu₃S₄ at T=300, 180 and 160 K were determined in the least-squares refinements with the Mo K intensity data. The valence-difference contrast method was applied at the L_II absorption edge of Eu, utilizing a large difference in anomalous scattering factors between Eu²⁺ and Eu³⁺. The cation distribution of Eu²⁺ and Eu³⁺ was determined by crystal-structure analyses based on the intensity data collected at two wavelengths of λ=1.6312 and 1.6298 Å.The least-squares structural refinements suggest that the most plausible atomic arrangement is [Eu³⁺]^4a[Eu²⁺Eu³⁺]^8dS₄. The charge-ordering scheme is that a half of Eu³⁺ ions occupy the whole 4a sites in the crystal structure, while the remaining half of Eu³⁺ ions mix with Eu²⁺ in the 8d sites. The scheme is also supported by the energy dependence of Bragg intensities for 400 and 004 reflections.