联噻吩桥联双三联吡啶的合成、质子化及其与金属离子的配位

以2,5-二溴噻吩为底物, 经醛基化、Kröhnke吡啶合成反应、Suzuki偶联三步制备了联噻吩桥联双三联吡啶 (BTTPY,总产率13%).通过紫外吸收及荧光光谱研究了其在酸性介质中的质子化效应, BTTPY在乙酸和三氟乙酸中的吸收及荧光光谱较非质子溶剂中均有明显红移.借助紫外吸收滴定法研究了其与过渡金属离子(Ni²⁺、Zn²⁺、Cd²⁺、Cu²⁺)的配位作用.结果表明BTTPY可与这些金属离子形成1:1的配合物,原子力显微镜 (AFM)图像显示, BTTPY与铬离子所形成的配位聚合物主要呈现一维堆积.     

Competition between pi and non-pi cation-binding sites in aromatic amino acids: a theoretical study of alkali metal cation (Li+, Na+, K+)-phenylalanine complexes

To understand the cation-pi interaction in aromatic amino acids and peptides, the binding of M(+) (where M(+) = Li(+), Na(+), and K(+)) to phenylalanine (Phe) is studied at the best level of density functional theory reported so far. The different modes of M(+) binding show the same order of binding affinity (Li(+)>Na(+)>K(+)), in the approximate ratio of 2.2:1.5:1.0. The most stable binding mode is one in which the M(+) is stabilized by a tridentate interaction between the cation and the carbonyl oxygen (O[double bond]C), amino nitrogen (--NH(2)), and aromatic pi ring; the absolute Li(+), Na(+), and K(+) affinities are estimated theoretically to be 275, 201, and 141 kJ mol(-1), respectively. Factors affecting the relative stabilities of various M(+)-Phe binding modes and conformers have been identified, with ion-dipole interaction playing an important role. We found that the trend of pi and non-pi cation bonding distances (Na(+)-pi>Na(+)-N>Na(+)-O and K(+)-pi>K(+)-N>K(+)-O) in our theoretical Na(+)/K(+)-Phe structures are in agreement with the reported X-ray crystal structures of model synthetic receptors (sodium and potassium bound lariat ether complexes), even though the average alkali metal cation-pi distance found in the crystal structures is longer. This difference between the solid and the gas-phase structures can be reconciled by taking the higher coordination number of the cations in the lariat ether complexes into account.     

Calcium rubies: a family of red-emitting functionalizable indicators suitable for two-photon ca(2+) imaging

We designed Calcium Rubies, a family of functionalizable BAPTA-based red-fluorescent calcium (Ca(2+)) indicators as new tools for biological Ca(2+) imaging. The specificity of this Ca(2+)-indicator family is its side arm, attached on the ethylene glycol bridge that allows coupling the indicator to various groups while leaving open the possibility of aromatic substitutions on the BAPTA core for tuning the Ca(2+)-binding affinity. Using this possibility we now synthesize and characterize three different CaRubies with affinities between 3 and 22 μM. Their long excitation and emission wavelengths (peaks at 586/604 nm) allow their use in otherwise challenging multicolor experiments, e.g., when combining Ca(2+) uncaging or optogenetic stimulation with Ca(2+) imaging in cells expressing fluorescent proteins. We illustrate this capacity by the detection of Ca(2+) transients evoked by blue light in cultured astrocytes expressing CatCh, a light-sensitive Ca(2+)-translocating channelrhodopsin linked to yellow fluorescent protein. Using time-correlated single-photon counting, we measured fluorescence lifetimes for all CaRubies and demonstrate a 10-fold increase in the average lifetime upon Ca(2+) chelation. Since only the fluorescence quantum yield but not the absorbance of the CaRubies is Ca(2+)-dependent, calibrated two-photon fluorescence excitation measurements of absolute Ca(2+) concentrations are feasible.     

Atmospheric CO_2 capture and photofixation to near-unity CO by Ti~(3+)-V_o-Ti~(3+) sites confined in TiO_2 ultrathin layers

To realize efficient atmospheric CO_2 chemisorption and activation,abundant Ti~(3+) sites and oxygen vacancies in TiO_2 ultrathin layers were designed.Positron annihilation lifetime spectroscopy and theoretical calculations first unveil each oxygen vacancy is associated with the formation of two Ti~(3+) sites,giving a Ti~(3+)-V_o-Ti~(3+)configuration.The Ti~(3+)-V_o-Ti~(3+) sites could bond with CO_2 molecules to form a stable configuration,which converted the endoergic chemisorption step to an exoergic process,verified by in-situ Fourier-transform infrared spectra and theoretical calculations.Also,the adjacent Ti~(3+) sites not only favor CO_2 activation into COOH*via forming a stable Ti~(3+)–C–O–Ti~(3+) configuration,but also facilitate the rate-limiting COOH~* scission to CO~* by reducing the energy barrier from 0.75 to 0.45 e V.Thus,the Ti~(3+)-V_o-TiO_2 ultrathinlayers could directly capture and photofix atmospheric CO_2 into near-unity CO,with the corresponding CO_2-to-CO conversion ratio of ca. 20.2%.     

Protonation of triethyl (2-pyridylimido)phosphates

Protonation of triethyl (2-pyridylimido)phosphates has been studied by potentiometric titration in nitromethane, IR and NMR spectroscopy, and X-ray structure analysis. The substances studied are protonated in one step at the N-atom of the pyridine ring. The protonated cations may be represented, according to the X-ray data, as a resonance of two structures: pyridinium and pyridoniminium; the contribution of the latter probably being considerable. Changes in spectral parameters of POEt groups upon protonation of pyridylimidophosphates (PIP) have been noted.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No 1, pp. 88–91, January, 1993.     

Theoretical study of interaction of urate with li(+), na(+), k(+), be(2+), mg(2+), and ca(2+) metal cations

The geometries and energetics of complexes of Li(+), Na(+), K(+), Be(2+), Mg(2+), and Ca(2+)metal cations with different possible uric acid anions (urate) were studied. The complexes were optimized at the B3LYP level and the 6-311++G(d,p) basis set. Complexes of urate with Mg(2+), and Ca(2+)metal cations were also optimized at the MP2/6-31+G(d) level. Single point energy calculations were performed at the MP2/6-311++G(d,p) level. The interactions of the metal cations at different nucleophilic sites of various possible urate were considered. It was revealed that metal cations would interact with urate in a bi-coordinate manner. In the gas phase, the most preferred position for the interaction of Li(+), Na(+), and K(+) cations is between the N(3) and O(2) sites, while all divalent cations Be(2+), Mg(2+), and Ca(2+) prefer binding between the N(7) and O(6) sites of the corresponding urate. The influence of aqueous solvent on the relative stability of different complexes has been examined using the Tomasi's polarized continuum model. The basis set superposition error (BSSE) corrected interaction energy was also computed for complexes. The AIM theory has been applied to analyze the properties of the bond critical points (electron densities and their Laplacians) involved in the coordination between urate and the metal cations. It was revealed that aqueous solvation would have significant effect on the relative stability of complexes obtained by the interaction of urate with Mg(2+) and Ca(2+)cations. Consequently, several complexes were found to exist in the water solution. The effect of metal cations on different NH and CO stretching vibrational modes of uric acid has also been discussed.     

Protonation sites and hydrogen bonding in mono-hydrobromide salts of two N,4-diheteroaryl 2-aminothiazoles

Structural Chemistry - The synthesis and structural characterization of N-(6-methoxypyridin-3-yl)-4-(pyridin-2-yl)thiazol-2-amine mono-hydrobromide monohydrate (3) and...     

Protonation sites of isolated fluorobenzene revealed by IR spectroscopy in the fingerprint range

Protonated fluorobenzene ions (C6H6F+) are produced by chemical ionization of C6H5F in the cell of a FT-ICR mass spectrometer using either CH5+ or C2H5+. The resulting protonation sites are probed by IR multiphoton dissociation (IRMPD) spectroscopy in the 600-1700 cm-1 fingerprint range employing the free electron laser at CLIO (Centre Laser Infrarouge Orsay). Comparison with quantum chemical calculations reveals that the IRMPD spectra are consistent with protonation in para and/or ortho position, which are the thermodynamically favored protonation sites. The lack of observation of protonation at the F substituent, when CH5+ is used as protonating agent, is attributed to the low-pressure conditions in the ICR cell where the ions are produced. Comparison of the C6H6F+ spectrum with IR spectra of C6H5F and C6H7+ reveals the effects of both protonation and H F substitution on the structural properties of these fundamental aromatic molecules.     

Eu^2＋和Mn^2＋在Sr3MgSi2O8中的光致发光研究

研究了Ｅｕ＾２＋和Ｍｎ＾２＋共激活的Ｓｒ３ＭｇＳｉ２Ｏ８的荧光性质。Ｅｕ＾２＋和Ｍｎ＾２＋在４６０ｎｍ和６９０ｎｍ的发射峰分别由Ｅｕ＾２＋的５ｄ→４ｆ跃迁和Ｍｎ＾２＋的＾４Ｔ１（＾４Ｇ）→＾６Ａ１ｇ（＾６Ｓ）跃迁产生。未观察到单掺杂Ｍｎ＾２＋的Ｓｒ３ＭｇＳｉ２Ｏ８的荧光发射，而掺入Ｅｕ＾２＋后则出现了Ｍｎ＾２＋的６９０ｎｍ光致发光峰，表明Ｅｕ＾２＋对Ｍｎ＾２＋有敏化作用。Ｅｕ＾２＋的荧光寿命也受Ｍ     

Protonation states of buried histidine residues in human deoxyhemoglobin revealed by neutron crystallography

The protonation states of buried histidine residues in human deoxyhemoglobin were unambiguously identified by using a neutron crystallographic technique. Unexpectedly, the neutron structure reveals that both the alpha- and beta-distal histidines (Hisalpha58 and Hisbeta63) adopt a positively charged, fully (doubly) protonated form, suggesting their contribution to the Bohr effect. In addition, the neutron data provide an accurate picture of the alpha1beta1 hydrogen-bonding network and allow us to observe unambiguously the nature of the intradimeric interactions at an atomic level.     

Concerning the photophysical properties of Re2(4+) and Re2(6+) carboxylate compounds

The preparation and structure of Re(2)(dppm)(2)(O(2)CC(6)H(4)-p-NO(2))(2)Cl(2), where dppm = Ph(2)PCH(2)PPh(2), is reported together with its photophysical properties (absorption, steady state emission, fs- and ns-transient absorption spectroscopy) and electrochemistry. These data are compared with photophysical studies on the previously reported Re(2)(dppm)(2)(O(2)CCH(3))(2)Cl(2). The preparation of the complex Re(2)(O(2)CC(6)H(4)-p-NO(2))(4)Cl(2) is also reported together with its photophysical properties which allows for a comparison of the electronic structures and photophysical states of Re(2)(4+) and Re(2)(6+) containing complexes having MM configurations σ(2)π(4)δ(2)δ(*2) and σ(2)π(4)δ(2), respectively. An interesting comparison is also made with the related MM quadruply bonded complexes of molybdenum and tungsten.     

Proton character of the peptide unit in the Ca2+-binding sites of calcium pump

The effect of forming calcium pump structures in biological systems on the proton character of the peptide unit has been studied theoretically using the density-functional theory calculations with a large basis set. One acetic acid, one acetate, and three acetamide molecules as well as the modeling peptide unit (MPU) have been employed to mimic the amino acid residues forming the Ca2+-binding sites. To highlight the limiting case of the Ca2+-binding effect on the proton property and the proton countertransport possibility in the direction opposite to the ion, the MPU bounded by the bare or the hydrated Ca2+ has also been investigated. The natural bond orbital (NBO) analysis indicates that the increase of the p-character of the (N-H) sigma orbital results in weakening of the N-H bond which is lengthened when a Ca2+ ion is introduced to the MPU. Calculated NMR shielding sigma(H1) of the MPU shifts upfield upon the Ca2+ ion combination, which reveals the donating of the electron from the amide H as represented by the increase of the calculated positive natural charge for amide H of the MPU. Moreover, the proton affinities (PA) and gas-phase basicities (GB) for the amide nitrogen active site of the MPU are reduced; that is, the acidity of the amide hydrogen gets stronger because of the influence of the Ca2+ ion. To prove the transport possibility of the N-H proton in the direction opposite to the Ca2+ ion along the N-H...O=C hydrogen bond in the helical peptide linkage, NH3 and H2O are used here to assist the dissociation of the amide H of the MPU, and the calculated results show the notable decrease of the deprotonation energies compared to that of the case without this assistance. Moreover, calculated results also reveal that the variation of the quantities discussed here for amide H of the MPU gets smaller when the acidity of Ca2+ ion decreases. Ionization states of the acidic residues forming the Ca2+-binding sites may influence the activity of the amide H of the MPU and further affect the transport tendency of the peptide unit proton in the direction opposite to Ca2+.     

The effect of triethylenetetraamine (Trien) on the ion flotation of Cu(2+) and Ni(2+)

Ion flotation is a separation process involving the adsorption of a surfactant and counterions at an air/aqueous solution interface. It shows promise for removing toxic heavy metal ions from dilute aqueous solutions. Here we report the effect of a neutral chelating ligand, triethylenetetraamine (Trien), on the ion flotation of cations with dodecylsulfate, DS(-), introduced as sodium dodecylsulfate, SDS. Ion flotation in the aqueous SD-Cu(II)-Ca(II)-Trien system gave strongly preferential removal of Cu(II) over Ca(II), which is a reversal of the order of selectivity seen in the SDS-Cu(II)-Ca(II) system containing no Trien. The removal rates of Cu(2+) and Ni(2+) with DS(-) were much faster in the presence of Trien than for simple aquo ions, and the final metal concentration was significantly lower. Surface tension measurements showed that Trien enhanced the surface activity and adsorption density for SDS-Cu(II) and SDS-Ni(II) solutions. The overall change in the Gibbs free energy for adsorption resulting from complexation was -3.60 kJ/mol for Cu(II) and -3.50 kJ/mol for Ni(II). This included the effects of hydrophobic interactions between the metal-Trien complexes at the air/solution interface, along with changes in the amount of dehydration associated with cosorption of the metal-Trien complex with DS(-) at the air/solution interface.     

基于胸腺嘧啶-汞离子-胸腺嘧啶结构和纳米金放大传感器检测汞离子

利用Hg2+与DNA中胸腺嘧啶(T)结合的高度特异性和纳米金在石英晶体微天平(QCM)上的信号放大作用,设计了一种简便灵敏的Hg2+检测方法.纳米金采用柠檬酸钠还原法制备,其表面用末端带巯基的寡核苷酸探针进行自组装修饰,并用6-巯基己-1-醇(MCH)部分取代表面探针,以减少杂交空间位阻.结果表明,寡核苷酸链长为9bp、T个数为7的序列具有较高灵敏度;线性范围为5.0～100 nmol/L;检出限为2.0 nmol/L;Ca2+、Mg2+等其它金属离子无明显干扰.用于环境水样中Hg2+的测定, RSD<2.9%;加标回收率为97.3%～101.2%     

Theoretical study on the Co~(2+)OH_2/Co~(3+)OH_2 electron transfer reactivity

This paper presents a contact distance dependence analysis scheme and an ab initio calculation application for the electron transfer (ET) reactivity of Co2+OH2/Co3+OH2 reacting pair. The applicability of these schemes and the corresponding models has been discussed. The contact distance (Rcoco) dependence of the relevant quantities has been analyzed. The results indicate that the activation energy from the accurate PES method agrees well with that from the anharmonic potential method, and they are obviously better than that from the harmonic potential method. The pair distribution function varies from 10~(-2) to 10~(-5) along with Rcoco changing from 1.20 to 0.35 nm. The coupling matrix element exponentially decays along with the increase of Rcoco, and the effective electronic coupling requires Rcoco smaller than 0.75 nm. In the range from 0.50 to 0.75 nm for Rcoco, the corresponding electronic transmission coefficient falls within 1.0-10~(-6). The local ET rate also exponentially decays along with the incre     

金属离子Cu~(2+)，Co~(2+)，Ni~(2+)的微芯片电泳分离及化学发光检测

根据流动注射－化学发光的通用实验装置图，设计并通过标准光刻技术，湿化 学刻蚀及热键合技术制作了玻璃微芯片。在该芯片上将毛细管电泳分离与化学发光 检测相联用，鲁米诺和H_2O_2化学发光反应溶液通过实验室自制的微流泵输送。对 所用电压，缓冲溶液和发光试剂流速等实验条件进行了优化。在所选的最佳条件下 ，成功地实现了金属离子Cu~(2+)，Co~(2+)，Ni~(2+)的电泳分离－化学发光检测， 过渡金属离子。     

Utilization of an Hg(2+)-sensitive membrane-electrode in the complexometric determination of Bi(3+), Fe(3+) and Cr(3+)

The paper reports the results obtained in the complexometric determination of Bi(3+), Fe(3+) and Cr(3+) by using an Hg(2+)-sensitive membrane-electrode for the end-point indication. The determination of Bi(3+) and Fe(3+) is performed after addition of mercuric complexonate from which these cations release Hg(2+) by means of which the electrode senses the equivalence point. In the case of Cr(3+) an excess of complexone is added and the surplus is titrated with a standard solution of Hg(2+) in the presence of the Hg(2+)-sensitive membrane-electrode.     

Protonation of 1,4-bis(1-vinyl-2-pyrrolyl)benzene

In the reaction of 1,4-bis(1-vinyl-2-pyrrolyl)benzene with hydrogen chloride and hydrogen bromide the hydrogen halide adds at the vinyl groups, and -protonation takes place in both pyrrole rings. In reaction with the superacidic system HSO₃F+SbF₅ (in SO₂ClF) position 5 of one heterocycle and position 4 of the other are protonated with retention of the vinyl groups.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1041–1045, August, 1991.