模板剂对SAPO-34分子筛晶粒尺寸和性能的影响

分别以三乙胺，四乙基氢氧化铵及二者的混合物为模板剂合成了硅磷酸铝分子筛ＳＡＰＯ－３４。应用ＸＲＤ，ＳＥＭ，ＤＴＡ和ＮＨ３－ＴＰＤ等方法考察了合成产品的物化性能，所得结果表明，模板剂的种类对ＳＡＰＯ－３４的晶粒大小和酸性质有显著影响。在甲醇转化制低碳烯烃的过程中，以不同模板剂合成的ＳＡＰＯ－３４的催化性能也不同，其中，以双模板剂合成的分子筛具有较高的低碳烯烃选择性。     

稀土离子对大肠杆菌亮氨酰-tRNA合成酶动力学性质的影响

采用含ｐＴｒｅ－９９Ｂ／ｌｅｕＳ２转化子的高表达菌株,简便快速地提取、纯化大肠杆菌亮氨酰－ｔＲＮＡ｜＾ｅｕ与未脱镁ｔＲＮＡ｜＾ｅｕ对ＡＴＰ和亮 酸的表观Ｋｍ值明显不同。高浓度ＡＴＰ对脱镁tＰＮＡ显示抑制作用,说明金属离子是氨酰化反应的底物之一。     

模板剂对SAPO—34分子筛性能的影响

分别以三乙胺、四乙基氢氧化铵以及二者的混合物为模板剂，采用水热法合成了三种ＳＡＰＯ－３４分子筛样品。用化学分析、ＸＲＤ、ＴＰＤ和ＩＲ方法研究了不同模板剂对ＳＡＰＯ－３４分子筛性能的影响。实验结果表明，四乙基氢氧化铵有利于硅进入分子筛骨架；三乙胺有利于生成较多的强酸中心；将三乙胺与四乙基氢氧化铵联用，能有效地调变所合成的ＳＡＰＯ－３４的酸中心分布，使其对甲醇转化制低碳烯烃具有较高的选择性。     

模板剂对SAPO─34分子筛性能的影响

分别以三乙胺、四乙基氢氧化铵以及二者的混合物为模板剂，采用水热法合成了三种ＳＡＰＯ－３４分子筛样品。用化学分析、ＸＲＤ、ＴＰＤ和ＩＲ方法研究了不同模板剂对ＳＡＰＯ－３４分子筛性能的影响。实验结果表明，四乙基氢氧化铵有利于硅进入分子筛骨架；三乙胺有利于生成较多的强酸中心；将三乙胺与四乙基氢氧化铵联用，能有效地调变所合成的ＳＡＰＯ－３４的酸中心分布，使其对甲醇转化制低碳烯烃具有较高的选择性。     

硅源及晶化时间对SAPO—5分子筛模板剂,酸性及催化性能的影响

改变硅源和晶化时间合成了系列ＳＡＰＯ－５分子筛，用原位红外光谱和ＮＨ３－ＴＰＤ研究了不同样品的酸碱性，用ＴＧ－ＤＴＡ和ＭＡＳ ＮＭＲ考察了硅源及晶化时间对分子筛模板剂的影响，评价了不同样品对正己烷裂解的催化活性。结果表明，ＳＡＰＯ－５分子筛孔道不仅与模板剂的胺基有作用，而且与其甲基也有作用。以硅凝胶为硅源时，在４８ｈ内，延长晶化时间可使分子筛中硅含量和强酸中心数目增加，低温下正己烷裂解活性提高；晶     

钛硅沸石合成过程中有机胺的作用

采用四丙基溴化铵（ＴＰＡＢｒ）为模板剂，分别以正丁胺（ＮＢＡ）、己二胺（ＨＤＡ）、二乙胺（ＤＥＡ）、乙二胺（ＥＤＡ）、三丙胺（ＴＰＡ）和四乙基氢氧化铵（ＴＥＡＯＨ）调节凝胶碱度，成功地合成出ＴＳ－１沸石．采用ＩＲ，ＸＲＤ，ＵＶ－Ｖｉｓ和ＮＭＲ等表征技术，详细考察了有机胺的作用及对钛进入沸石骨架的影响．结果表明，以ＴＥＡＯＨ为碱源时抑制钛进入骨架；以ＥＤＡ为碱源时合成的钛硅沸石结晶度低；以ＴＥＡＯＨ或ＮＢＡ为碱源时合成的钛硅沸石晶粒较均匀．有机胺在ＴＳ－１合成过程中只起到调节碱度的作用，未与ＴＰＡＢｒ联合起模板作用．     

不同方法制备的Cu－Co低碳醇含成催化剂的比较研究Ⅱ．H_2－TPD，CO－TPD及CO／H_2TPSR的研究

本文采用Ｈ２－ＴＰＤ，ＣＯ－ＴＰＤ及ＣＯ／Ｈ２ＴＰＳＲ技术对三种方法（ＳＭＡＤ、浸渍、共沉淀）制备的Ｃｕ－Ｃｏ催化剂进行了表征，并与低碳醇合成选择性进行了关联．Ｃｕ－Ｃｏ催化剂上Ｈ２－ＴＰＤ谱中共有四个脱附峰（Ａ，Ｂ，Ｃ，Ｄ），其中Ｃ峰对应于低配位Ｃｏ中心上的活化吸附氢，其面积百分数随不同催化剂的变化规律与醇选择性的变化规律一致．与ＣＯ－ＴＰＤ谱对比，Ｃｏ及Ｃｕ－Ｃｏ催化剂上ＣＯ／Ｈ２ＴＰＳＲ谱中都出现一个新的甲烷析出峰（４７３～５７３Ｋ），归属为活化吸附氢与表面活泼碳物种之间的反应，其面积百分数随不同催化剂的变化规律与醇选择性的变化一致。基于上述结果，就ＣＯ插入中心问题进行了讨论．     

钛酸盐分子筛的合成研究

以ＴＰＡＯＨ和ＴＥＡＯＨ模板剂分别合成了具有孔道结构的钛酸铜、钛铝酸钠和钛酸钠分子筛，采用Ｘ射线衍射，红外光谱，紫外光谱，扫描电镜，差热分析、ＮＨ３－脱附法及气体吸附法等测试手段对钛酸盐分子筛的物性及结构进行了表征。利用苯酚羟基化反应及气相色谱法证明了具有四配位ＴｉＯ４结构单元的钛酸铜分子筛的催化氧化性能。     

硅源及晶化时间对SAPO-5分子筛模板剂、酸性及催化性能的影响

改变硅源和晶化时间合成了系列ＳＡＰＯ５分子筛．用原位红外光谱和ＮＨ３ＴＰＤ研究了不同样品的酸碱性，用ＴＧＤＴＡ和ＭＡＳＮＭＲ考察了硅源及晶化时间对分子筛模板剂的影响，评价了不同样品对正己烷裂解的催化活性．结果表明，ＳＡＰＯ５分子筛孔道不仅与模板剂的胺基有作用，而且与其甲基也有作用．以硅凝胶为硅源时，在４８ｈ内，延长晶化时间可使分子筛中硅含量和强酸中心数目增加，低温下正己烷裂解活性提高；晶化７２ｈ时，分子筛的酸性减弱，正己烷裂解活性降低．以正硅酸乙酯为硅源时，延长晶化时间可使ＳＡＰＯ５的酸性增强，正己烷裂解性能提高．     

Gd－DTPA氨基酸、短肽衍生物的合成及其磁共振成像造影性能的研究

合成了一系列二乙三胺五乙酸（ＤＴＰＡ）的疏水性氨基酸、短肽衍生物的Ｇｄ（Ⅲ）螯合物，研究了其磁共振成像造影性能。结果表明：螯合物的急性毒性与Ｇｄ－ＤＴＰＡ相当，自旋－晶格弛豫性能Ｒ＿１比Ｇｄ－ＤＴＰＡ略高。Ｇｄ－ＤＴＰＡ，氨基酸，短肽，急性毒性，自旋－晶格弛豫性能     

Irreversibly electropermeabilized yeast retains the capability for ATP synthesis via oxidative phosphorylation

ATP synthesis in irreversibly electropermeabilized yeast Kluyveromyces lactis was studied by using different respiratory substrates. The permeabilization itself provoked a dramatic decrease of the total ATP level and the cells lost their ability to synthesize ATP via glycolysis. The addition of exogenous NADH supported ATP synthesis in irreversibly permeabilized cells for up to 4-6 h after substrate addition when the total ATP level became twice that of intact cells incubated for the same period with lactose.     

Molecular and Pharmacological Evidence for the Expression of Multiple Functional P2 Purinergic Receptors in Human Adipocytes

Extracellular ATP exerts important functions as an extracellular signaling molecule via the activation of specific P2 purinergic receptors (P2X and P2Y). We investigated the expression of the different P2 receptors and their possible functional activation in human adipocytes in primary culture. We performed molecular expression analysis of the P2 receptors in human mature adipocytes; examined their functional activation by different nucleotides evaluating [Ca²⁺]_i modifications and IL-6 secretion, and determined the ability of adipocytes to release ATP in the extracellular medium. Human adipocytes express different P2X and P2Y receptors. Extracellular ATP elicited a rise in [Ca²⁺]_i via the activation of P2X and P2Y receptor subtypes. Human adipocytes spontaneously released ATP in the extracellular medium and secreted IL-6 both at rest and after stimulation with ATP. This stimulatory effect of ATP on IL-6 secretion was inhibited by pre-incubation with apyrase, an ATP metabolizing enzyme. These results demonstrate that human adipocytes express different P2X and P2Y receptors that are functionally activated by extracellular nucleotides. Furthermore, human adipocytes spontaneously release ATP, which can act in an autocrine/paracrine fashion on adipocytes, possibly participating in the regulation of inflammatory cytokine release. Thus, P2 purinergic receptors could be a potential therapeutic target to contrast the inflammatory and metabolic complications characterizing obesity.     

Systematic investigation of sequence and structural motifs that recognize ATP

Interaction between ATP, a multifunctional and ubiquitous nucleotide, and proteins initializes phosphorylation, polypeptide synthesis and ATP hydrolysis which supplies energy for metabolism. However, current knowledge concerning the mechanisms through which ATP is recognized by proteins is incomplete, scattered, and inaccurate. We systemically investigate sequence and structural motifs of proteins that recognize ATP. We identified three novel motifs and refined the known p-loop and class II aminoacyl-tRNA synthetase motifs. The five motifs define five distinct ATP–protein interaction modes which concern over 5% of known protein structures. We demonstrate that although these motifs share a common GXG tripeptide they recognize ATP through different functional groups. The p-loop motif recognizes ATP through phosphates, class II aminoacyl-tRNA synthetase motif targets adenosine and the other three motifs recognize both phosphates and adenosine. We show that some motifs are shared by different enzyme types. Statistical tests demonstrate that the five sequence motifs are significantly associated with the nucleotide binding proteins. Large-scale test on PDB reveals that about 98% of proteins that include one of the structural motifs are confirmed to bind ATP.     

布朗动力学理论模拟动态肌动蛋白纤维的增长

肌动蛋白的聚合耦合三磷酸腺酐(ATP)分子水解成二磷酸腺苷(ADP)分子和磷酸(Pi)的释放两个过程. 因此, 肌动蛋白纤维上的原聚体存在三种不同状态, 即分别结合ATP, ADP/Pi和ADP分子. 原聚体的不同状态导致纤维具有不同的空间图谱, 这些状态的空间分布将影响纤维的各种行为. 为此,建立了相应的分子模型,在布朗动力学模拟中实现了遵循时间演化的连续马尔可夫随机过程的解聚和水解反应; 重点阐述了如何实现纤维两端的聚合和解聚达到化学平衡的方法, 并系统研究了纤维在结合ATP分子的肌动蛋白单体溶液中的增长行为.     

多种精氨酸衍生物与ＡＴＰ作用及其催化ＡＴＰ水解的影响研究

分别使用荧光光谱法、 ~1H和~(31)P核磁方法对腺苷-5′-三磷酸(ATP)和多种L-精氨酸衍生物(L)的相互作用做了系统的研究, 得到了一些有意义的结果.在荧光滴定实验中, L对ATP有很强的荧光猝灭作用, 说明两者有较强的相互作用. ~1H和~(31)P核磁结果进一步证实了L与ATP的识别位点在ATP的嘌呤环和磷酸链上, 结合力为氢键和静电作用. 另外, 用~(31)P 核磁滴定的方法考察了L对ATP水解的影响, 发现不同的精氨酸衍生物对ATP水解的催化影响有很大的差异, 说明L对ATP的识别和催化其水解作用有较强的选择性. 此识别及催化作用的研究对深入理解精氨酸残基在ATP合酶中起到"触点"作用有一定的参考价值.     

Recognition and catalytic hydrolysis of adenosine 5′-triphosphate by cadmium(II) and L-glutamic acid

Interactions among Cd²⁺, glutamic acid (Glu), and adenosine 5′-triphosphate (ATP) have been studied by potentiometric pH titration, IR, Raman, fluorescence, and NMR methods. In the Cd²⁺–ATP binary system, the main interaction sites are the α-, β-, and γ-phosphate groups, N-1, and/or N-7. Cd²⁺ binds to the N-1 site at relatively low pH and binds to the N-7 site of adenosine ring of ATP with increasing pH. In the Cd²⁺–Glu–ATP ternary system, ATP mainly binds to Cd²⁺ by the triphosphate chain. Oxygens of Glu coordinate with Cd²⁺ to form a complex to catalyze ATP hydrolysis. Hydrolysis of ATP catalyzed by the CdGlu complex was studied at pH 7.0 and 80°C by ³¹P-NMR spectrometry. Kinetics studies showed that the rate constant of ATP hydrolysis was 0.0199?min^?1 in the ternary system, which is 9.9-fold faster than that in the ATP solution (2.01?×?10^?3?min^?1). Hydrolysis occurs through an addition–elimination reaction mechanism with Cd²⁺ regulating the recognition and catalytic hydrolysis of ATP; water participates in the hydrolysis reaction of ATP at different steps with different functions in the ternary system.     

A Small-Molecule Fluorescence Probe for Nuclear ATP

Fluorescence monitoring of ATP in different organelles is now feasible with a few biosensors developed, which, however, show low sensitivity, limited biocompatibility, and accessibility. Small-molecule ATP probes that alleviate those limitations thus have received much attention recently, leading to a few ATP probes that target several organelles except for the nucleus. We disclose the first small-molecule probe that selectively detects nuclear ATP through reversible binding, with 25-fold fluorescence enhancement at pH 7.4 and excellent selectivity against various biologically relevant species. Using the probe, we observed 2.1–3.3-fold and 3.9–7.8-fold higher nuclear ATP levels in cancerous cell lines and tumor tissues compared with normal cell lines and tissues, respectively, which are explained by the higher nuclear ATP level in the mitosis phase. The probe has great potential for studying nuclear ATP-associated biology.     

Probing conformational variations at the ATPase site of the RNA helicase DbpA by high-field electron-nuclear double resonance spectroscopy

The RNA helicase DbpA promotes RNA remodeling coupled to ATP hydrolysis. It is unique because of its specificity to hairpin 92 of 23S rRNA (HP92). Although DbpA kinetic pathways leading to ATP hydrolysis and RNA unwinding have been recently elucidated, the molecular (atomic) basis for the coupling of ATP hydrolysis to RNA remodeling remains unclear. This is, in part, due to the lack of detailed structural information on the ATPase site in the presence and absence of RNA in solution. We used high-field pulse ENDOR (electron-nuclear double resonance) spectroscopy to detect and analyze fine conformational changes in the protein's ATPase site in solution. Specifically, we substituted the essential Mg(2+) cofactor in the ATPase active site for paramagnetic Mn(2+) and determined its close environment with different nucleotides (ADP, ATP, and the ATP analogues ATPγS and AMPPnP) in complex with single- and double-stranded RNA. We monitored the Mn(2+) interactions with the nucleotide phosphates through the (31)P hyperfine couplings and the coordination by protein residues through (13)C hyperfine coupling from (13)C-enriched DbpA. We observed that the nucleotide binding site of DbpA adopts different conformational states upon binding of different nucleotides. The ENDOR spectra revealed a clear distinction between hydrolyzable and nonhydrolyzable nucleotides prior to RNA binding. Furthermore, both the (13)C and the (31)P ENDOR spectra were found to be highly sensitive to changes in the local environment of the Mn(2+) ion induced by the hydrolysis. More specifically, ATPγS was efficiently hydrolyzed upon binding of RNA, similar to ATP. Importantly, the Mn(2+) cofactor remains bound to a single protein side chain and to one or two nucleotide phosphates in all complexes, whereas the remaining metal coordination positions are occupied by water. The conformational changes in the protein's ATPase active site associated with the different DbpA states occur in remote coordination shells of the Mn(2+) ion. Finally, a competitive Mn(2+) binding site was found for single-stranded RNA construct.     

Glucose oxidase/hexokinase electrode for the determination of ATP

A hydrogen peroxide based enzyme electrode for the determination of ATP has been developed by the immobilization of glucose oxidase and hexokinase. Competition between the enzymes for the substrate glucose allowed the measurement of ATP. Different immobilization procedures and different types of hexokinase have been tested. Using a BSA-glutaraldehyde procedure and hexokinase from an overproducing strain of bakers' yeast, ATP was measured in the 0.05–0.5 mmol l⁻¹ range with a detection limit of 0.01 mmol l⁻¹. ATP concentrations comparable to those reported in the literature and a good recovery were obtained when the enzyme electrode was used with human erythrocyte hemolysate.     

不同形态的氧氟沙星在凹凸棒土上的吸附特征

通过控制反应体系的pH值,探究了阳离子、兼性和阴离子形态的氧氟沙星(OFL,3种形态分别记为OFL~+,OFL~±和OFL~-)在凹凸棒土(ATP)上的吸附特征.实验结果表明,OFL~+主要通过与ATP表面的Ca~(2+),Mg~(2+)进行阳离子交换吸附于ATP上,当其吸附量较高时,会存在少量的氢键;OFL~±和OFL~-可与ATP表面的铁氧化物、铝氧化物进行表面络合,也可与溶液中从ATP中溶解出的Ca~(2+)和Mg~(2+)形成络合物,再通过静电作用吸附于ATP上.在中性至微碱性(pH=7.10~7.70)条件下,由于Ca的电负性小于Mg,[Ca~(2+)-OFL]+不能稳定地存在于溶液中,使得OFL±与Ca~(2+)进行阳离子交换而与Mg~(2+)形成络合物,再通过静电作用吸附于ATP上.当OFL主要以OFL~-形态存在于溶液中时(p H=9.00~10.00),Ca~(2+)和Mg~(2+)均可与OFL~-形成络合物,再通过静电作用吸附于ATP上.