含铥金属富勒烯的生成及其特殊的溶解行为

金属富勒烯的合成及结构研究是当前富勒烯化学研究的重要内容[1]．一些稀土金属元素，如Sc[2]、Y[3]及大部分斓系元素（La、Ce、Nd、Sin、Eu、Gd、Tb、Ho）[4]形成的金属富勒烯已被合成出来．但仍有一些稀土富勒烯的合成尚未见报道，使人们难以对金属富勒烯的形成机制及物化性能作出全面的判断．本文采用原位活化、交换电极回放电弧放电及两步提取法首次得到含锡金属富勒烯．通过空白对比实验确定了Tin＠C。怕9生成．对甲苯及毗院提取液的质谱研究表明含镀金属富勒烯具有区别于其它金属富勒烯的特殊的溶解性能，显示出其可能具有独特的…     

Structural study of three isomers of Tm@C(82) by (13)C NMR spectroscopy

The (13)C NMR spectra were measured for three isomers of Tm@C(82), which is one of the divalent metallofullerenes. The molecular symmetries were determined for each isomer: isomer I has C(s) symmetry, isomer II has C(2) symmetry, and isomer III has C(2v) symmetry. Moreover the cage structure of Tm@C(82)(III) was found to be C(82)(9). As a result, it was revealed that Tm@C(82)(III) has a cage identical to that of La@C(82), which is one of the trivalent metallofullerenes.     

The electronic and vibrational structure of endohedral Tm3N@C80 (I) fullerene--proof of an encaged Tm3+

The electronic and vibrational structure of the nitride clusterfullerene Tm3N@C80 (I) was investigated by cyclic voltammetry, FTIR, Raman, and X-ray photoemission spectroscopy. The electrochemical energy gap of Tm3N@C80 (I) is 1.99 V, which is 0.13 V larger than that of Sc3N@C80 (I). FTIR spectroscopy showed that the C80:7 (I(h)) cages in Tm3N@C80 (I), Er3N@C80 (I), Ho3N@C80 (I), Tb3N@C80 (I), Gd3N@C80 (I), and Y3N@C80 (I) have the same bond order. The analysis of low-energy Raman spectra points to two uniform force constants which can be used to describe the interaction between the encaged nitride cluster and the C80:7 (I(h)) cage in M3N@C80 (I) (M = Tm, Er, Ho, Tb, Gd, and Y). Because the M3N-C80 bond strength is strongly dependent on the charge of the metal ions, this is a direct hint for a 3+ formal valence state of the metal ions in these nitride clusterfullerene series, including Tm3N@C80 (I). Photoemission spectra of the Tm 4d core level and the Tm 4f valence electrons provided a direct proof for a (4f)12 electronic configuration of the encapsulated thulium. In conclusion, thulium in Tm3N@C80 (I) has a formal electronic ground state of +3, in contrast to the +2 state found in Tm@C82. It is demonstrated that the valence state of metal atoms encaged in fullerenes can be controlled by the chemical composition of the endohedral fullerene.     

Single samarium atoms in large fullerene cages. Characterization of two isomers of Sm@C92 and four isomers of Sm@C94 with the X-ray crystallographic identification of Sm@C1(42)-C92, Sm@C(s)(24)-C92, and Sm@C3v(134)-C94

Two isomers of Sm@C(92) and four isomers of Sm@C(94) were isolated from carbon soot obtained by electric arc vaporization of carbon rods doped with Sm(2)O(3). Analysis of the structures by single-crystal X-ray diffraction on cocrystals formed with Ni(II)(octaethylporphyrin) reveals the identities of two of the Sm@C(92) isomers: Sm@C(92)(I), which is the more abundant isomer, is Sm@C(1)(42)-C(92), and Sm@C(92)(II) is Sm@C(s)(24)-C(92). The structure of the most abundant form of the four isomers of Sm@C(94), Sm@C(94)(I), is Sm@C(3v)(134)-C(94), which utilizes the same cage isomer as the previously known Ca@C(3v)(134)-C(94) and Tm@C(3v)(134)-C(94). All of the structurally characterized isomers obey the isolated pentagon rule. While the four Sm@C(90) and five isomers of Sm@C(84) belong to common isomerization maps that allow these isomers to be interconverted through Stone-Wales transformations, Sm@C(1)(42)-C(92) and Sm@C(s)(24)-C(92) are not related to each other by any set of Stone-Wales transformations. UV-vis-NIR spectroscopy and computational studies indicate that Sm@C(1)(42)-C(92) is more stable than Sm@C(s)(24)-C(92) but possesses a smaller HOMO-LUMO gap. While the electronic structures of these endohedrals can be formally described as Sm(2+)@C(2n)(2-), the net charge transferred to the cage is less than two due to some back-donation of electrons from π orbitals of the cage to the metal ion.     

新型薄膜扩散梯度装置定量测量水环境中重金属形态

采用以纤维素透析膜为扩散相, 0.05 mol/L羧甲基纤维素钠(CMC)溶液为结合相的薄膜扩散梯度(DGT)装置(CMC-DGT)定量累积和测量水溶液中Cu²⁺, Cd²⁺和Pb²⁺的有效态; 考察了pH值和离子强度对CMC-DGT累积Cu²⁺, Cd²⁺和Pb²⁺的影响以及不同配体(乙二胺四乙酸二钠、 单宁酸和黄腐酸)对重金属有效态的影响; 测量了外加标的天然水和工业废水中重金属的有效态浓度; 并比较了不同结合相DGT装置对同一水体中重金属的有效态浓度. 实验结果表明, 0.05 mol/L CMC溶液对Cu²⁺, Cd²⁺和Pb²⁺累积容量分别为0.24, 0.11和0.45 mg/mL; 定量累积的最佳pH值范围分别为3.7～8.0, 4.7～9.0和4.7～8.0; 随着离子强度的增大, CMC-DGT对Cu²⁺, Cd²⁺和Pb²⁺的累积容量下降; CMC-DGT能够定量地累积配制水中的游离Cu²⁺, Cd²⁺和Pb²⁺, 回收率分别为92.1%, 100.6%和96.4%; 当有配体存在时, 随着配体浓度的增大, CMC-DGT测量的Cu²⁺, Cd²⁺和Pb²⁺有效态的浓度随之下降; 在过滤工业废水、 河水和湖水中, 不同结合相DGT装置对重金属有效态的测量值不同. 结果表明, CMC可作为DGT技术新的液态结合相.     

Size-specific interaction of alkali metal ions in the solvation of M+-benzene clusters by Ar atoms

The size-specific influence of the M+ alkali ion (M = Li, Na, K, Rb, and Cs) in the solvation process of the M+-benzene clusters by Ar atoms is investigated by means of molecular dynamic simulations. To fully understand the behavior observed in M+-bz-Ar(n) clusters, solvation is also studied in clusters containing either M+ or benzene only. The potential energy surfaces employed are based on a semiempirical bond-atom decomposition, which has been developed previously by some of the authors. The outcome of the dynamics is analyzed by employing radial distribution functions, studying the evolution of the distances between the Ar atoms and the alkali ion M+ or the benzene molecule for all M+-bz-Ar(n) clusters. For all members, in the M+-bz series, the benzene molecule (bz) is found to remain strongly bound to M+ even in the presence of solvent atoms. The radial distribution functions for the heavier clusters (K+-bz, Rb+-bz, and Cs+-bz), are found to be different than for the lighter (Na+-bz and Li+-bz) ones.     

Extreme stability of an unsolvated alpha-helix

High-temperature ion mobility measurements have been performed for alpha-helical Ac-A15K+H+ and globular Ac-KA15+H+ peptides. The alpha-helical and globular conformations do not melt into random coils as the temperature is raised. Instead, both conformations survive to the point where the peptide signals vanishes due to fragmentation. This occurs at 600 K for the globular Ac-KA15+H+ peptide and at 725 K for the alpha-helical Ac-A15K+H+. For the helical Ac-A15K+H+ peptide it appears that fragmentation is triggered by disruption of the helical conformation.     

Determination of vapor—liquid equilibrium diagrams of multicomponent systems

A method for the determination of vapor–liquid phase diagram structure of five-component systems based on the analysis of types and Poincare indexes of singular points of the geometric scan and full structure of the concentration simplex is proposed. Validity of the proposed method was demonstrated by vapor–liquid equilibrium modeling in five-component mixtures: ethanol + water + toluene + butanol + chlorbenzene and acetone + chloroform + ethanol + cyclohexane + water.     

Liquid-liquid equilibria of (cyclohexane + acetonitrile + methylcyclohexane + toluene) and of {(acetonitrile + methylcyclohexane) + benzene or + toluene or + cyclohexane or + chlorobenzene} at 298.15 K

Tie-line results at 298.15 K and atmospheric pressure are reported for (cyclohexane + acetonitrile + methylcyclohexane + toluene) and for {(acetonitrile + methylcyclohexane) + benzene or + toluene or + cyclohexane or + chlorobenzene). The extended UNIQUAC and UNIQUAC equations are used to correlate binary vapour-liquid equilibria and mutual solubilities for 10 mixtures constituting the ternary mixtures and to predict the ternary and quaternary liquid-liquid equilibria by use of only binary parameters.     

Fe3+/V5+/TiO2复合纳米微粒光催化性能的研究

采用溶胶凝胶法制备了Fe^3 /V^5 /TiO2复合纳米微粒作为光催化剂。光降解反应结果表明，其掺杂催化剂Fe^3 /V^5 /TiO2的光催化活性明显提高。光电化学研究显示，铁离子可以成为电荷陷阱，促进空穴的界面传递反应。适量钒离子掺杂使TiO2电极的光电流升高，导带中电子浓度的增大，加快了界面的电子传递反应。共掺杂催化剂中，Fe^3 、V^5 分别提供了空穴与电子的陷阱，同时加快了电子与空穴的界面传递反应，从 更有效地提高光催化活性。双组份共掺杂为提高TiO2光催化活性提供新的途径。     

亚相金属离子与两亲配体LB膜相互作用的研究

The complex formation of 2-hexadecylcarbamoyl-8-hydroxyquinoline(HHQ) monolayers at the air/water interface by reaction with metal ions from the subphase was investigated using X-ray photoelectron spectroscopy. The formation of HHQ-metal complexes leads to the appearance of new peaks assigned to the metal ions. The information on stoichimoetry provided by XPS indicated that a metal ion is coordinated by two HHQ molecules for La3+ and Cd2+ ions, but by one HHQ molecule for Mn2+ and Ni2+ ions.     

Preparation of monodisperse immobilized Ti affinity chromatography microspheres for specific enrichment of phosphopeptides

This study presented an approach to prepare monodisperse immobilized Ti⁴⁺ affinity chromatography (Ti⁴⁺-IMAC) microspheres for specific enrichment of phosphopeptides in phosphoproteome analysis. Monodisperse polystyrene seed microspheres with a diameter of ca. 4.8 μm were first prepared by a dispersion polymerization method. Monodisperse microspheres with a diameter of ca. 13 μm were prepared using the seed microspheres by a single-step swelling and polymerization method. Ti⁴⁺ ion was immobilized after chemical modification of the microspheres with phosphonate groups. The specificity of the Ti⁴⁺-IMAC microspheres to phosphopeptides was demonstrated by selective enrichment of phosphopeptides from mixture of tryptic digests of α-casein and bovine serum albumin (BSA) at molar ratio of 1 to 500 by MALDI-TOF MS analysis. The sensitivity of detection for phosphopeptides determined by MALDI-TOF MS was as low as 5 fmol for standard tryptic digest of β-casein. The Ti⁴⁺-IMAC microspheres were compared with commercial Fe³⁺-IMAC adsorbent and homemade Zr⁴⁺-IMAC microspheres for enrichment of phosphopeptides. The phosphopeptides and non-phosphopeptides identified by Fe³⁺-IMAC, Zr⁴⁺-IMAC and Ti⁴⁺-IMAC methods were 26, 114, 127 and 181, 11, 11 respectively for the same tryptic digest samples. The results indicated that the Ti⁴⁺-IMAC had the best performance for enrichment of phosphopeptides.     

Improved sensitivity for quantification of proteins using triply charged cleavable isotope-coded affinity tag peptides

Isotope-coded affinity tag (ICAT) methods, in conjunction with capillary liquid chromatography/tandem mass spectrometry (LC/MS/MS), represent a promising approach for accurate protein quantification. However, sensitivity remains a challenge for the quantification of low-copy proteins in complex biological matrices. Here we investigated the electrospray ionization (ESI) and collision-activated dissociation (CAD) behavior of peptides derivatized with the cleavable ICAT (cICAT) reagent. For cICAT-peptides that were either synthesized or obtained by digestion of model proteins, the cICAT moiety showed a tendency toward protonation under positive ESI, producing relatively intense triply charged cICAT-peptide ions ([IP+3H]3+). [IP+3H]3+ exhibited significantly higher CAD reactivity than did the doubly charged cICAT-peptide ([IP+2H]2+), and produced a greater abundance of fragments at lower collision energies. Fragmentation spectra of [IP+3H]3+ showed variable intensities of doubly charged y and b ions, and the amount of sequence information obtained was dependent on the position of the cICAT-labeled cysteine residue in the peptide sequence. However, the absolute abundances of major fragments of [IP+3H]3+ were much higher than for [IP+2H]2+. Although the efficiency of identification of cICAT-peptides was compromised by their charge distribution toward the triply charged state and by the unique CAD behavior of the [IP+3H]3+ ions, it was found that the triply charged ions provided higher sensitivity than [IP+2H]2+ for quantification using multiple reaction monitoring (MRM). ESI and CAD conditions for MRM of [IP+3H]3+ were optimized, and, for all cICAT-peptides studied, MRM using [IP+3H]3+ as precursors showed 2- to 8-fold higher sensitivity than obtained using [IP+2H]2+, without compromising quantitative accuracy. Using this approach, the time course of tyrosine aminotransferase induction by methylprednisolone was monitored in rat livers. A remarkably better signal-to-noise ratio was observed by using [IP+3H]3+ for quantification compared to [IP+2H]2+.     

Quantitative depth profiling of argon in tungsten films by secondary ion mass spectrometry.

Depth profiling of Ar in Ar-implanted tungsten (W) films with an excellent detection limit was investigated by secondary ion mass spectrometry (SIMS). Depth profiles of Ar with the detection of Ar+ and ArCs+ secondary ions, which were produced by O2+ and Cs+ primary ions, respectively, were compared in view of the detection limit and the depth resolution. The detection limit of Ar monitoring Ar+ was limited by the carbon- and oxygen-containing molecular ion (C2O+) in the sample as well as in the SIMS instrument. It was observed that some of the Ar+ ions were produced in the vacuum above the sample surfaces, whereas the ionization of almost all C2O+ occurred at the samples. By using different energy spectra between Ar+ and C2O+, we showed that the energy-filtering technique is advantageous for suppressing C2O+ ion detection. It is also confirmed that the ArCs+ secondary ion is only slighting by the C2OCs+ mass-interference ion. A detection limit of 4 x 10(18) cm(-3) for monitoring Ar+ and 3 x 10(16) cm(-3) for monitoring ArCs+ was achieved under a primary-ion current density of 0.16 mA/cm2. The detection of ArCs+ ion rather than Ar+ was found to be superior in the detection limit and the depth resolution. We conclude that SIMS is useful for the determination of the Ar depth distribution in W films.     

Role of fluctuations in a snug-fit mechanism of KcsA channel selectivity

The thermodynamic exclusion of Na+ relative to K+ in potassium channels is examined by calculating the distribution of binding energies for Na+ and K+ in a model of the selectivity filter of the KcsA potassium channel. These distributions are observed to take a surprisingly simple form: Gaussian with a slight positive skewness that is insignificant in the present context. Complications that might be anticipated from these distributions are not problematic here. Na+ occupies the filter with a mean binding energy substantially lower than that of K+. The difference is comparable to the difference in hydration free energies of Na+ and K+ in bulk aqueous solution. Thus, the average energies of binding to the filter do not discriminate Na+ from K+ when measured from a baseline of the difference in bulk hydration free energies. The strong binding of Na+ constricts the filter, consistent with a negative partial molar volume of Na+ in water in contrast with a positive partial molar volume of K+ in water. Discrimination in favor of K+)can be attributed to the scarcity of favorable binding configurations for Na+ compared to K+. That relative scarcity is quantified as enhanced binding energy fluctuations, which reflects both the energetically stronger binding of Na+ and the constriction of the filter induced by Na+ binding.     

Combined effect of osteopontin and BMP-2 derived peptides grafted to an adhesive hydrogel on osteogenic and vasculogenic differentiation of marrow stromal cells

The objective of this work was to investigate the combined effect of grafting the peptide corresponding to amino acid residues 162-168 of osteopontin (OPD peptide) and the peptide corresponding to amino acid residues 73-92 of bone morphogenetic protein-2 (BMP peptide) to an RGD-conjugated inert hydrogel on osteogenic and vasculogenic differentiation of bone marrow stromal (BMS) cells. RGD-conjugated three-dimensional (3D) porous hydrogel scaffolds with well-defined cylindrical pore geometry were produced from sacrificial wax molds fabricated by fused deposition modeling rapid prototyping system. Propargyl acrylate and 4-pentenal were conjugated to the hydrogel for orthogonal grafting of BMP and OPD peptides by click reaction and oxime ligation, respectively. The OPD peptide was grafted by the reaction between aminooxy moiety of aminooxy-mPEG-OPD (mPEG = mini-poly(ethylene glycol)) and the aldehyde moiety in the hydrogel. The BMP peptide was grafted by the reaction between the azide moiety of Az-mPEG-BMP and the propargyl moiety in the hydrogel. The hydrogels seeded with BMS cells were characterized by biochemical, immunocytochemical, and mRNA analyses. Groups included RGD control hydrogel (RGD), RGD and BMP peptides without OPD (RGD+BMP), RGD and BMP peptides with mutant OPD (RGD+BMP+mOPD), and RGD and BMP peptides with OPD (RGD+BMP+OPD) grafted hydrogels. The extent of mineralization of RGD, RGD+BMP, RGD+BMP+mOPD, and RGD+BMP+OPD groups after 28 days was 650 ± 70, 990 ± 30, 850 ± 30, and 1150 ± 40 mg/(mg of DNA), respectively, indicating that the BMP and OPD peptides enhanced osteogenic differentiation of the BMS cells. The BMS cells seeded on RGD+BMP+OPD grafted hydrogels stained positive for vasculogenic markers α-SMA, PECAM-1, and VE-cadherin while the groups without OPD peptide (RGD+BMP and RGD+BMP+mOPD) stained only for α-SMA but not PECAM-1 or VE-cadherin. These results were consistent with the significantly higher PECAM-1 mRNA expression for RGD+BMP+OPD group after 21 and 28 days, compared to the groups without OPD. These findings suggest that the RGD+BMP+OPD peptides provide a favorable microenvironment for concurrent osteogenic and vasculogenic differentiation of progenitor marrow-derived cells.     

Potentiometric study of the mixed-metal complex formation of tetracarboxylate-18-crown-6 with aluminum and alkali and alkaline earth cations

We give evidence for the formation of mixed-metal complexes of tetracarboxylate-18-crown-6 in the form of Al³⁺-macrocycle-M^Z+, with M^Z+ being an alkali or an alkaline earth cation. These binuclear systems are characterized by potentiometric p[H] titrations and the equilibrium constants for all major complexes formed are described. The results are presented in the form of distribution diagrams revealing the concentrations of individual complex species as a function of p[H]. The stability of the resulting mixed-metal complexes with Al³⁺ and alkali and alkaline earth cations vary in the order Na⁺>K⁺>Cs⁺ and Ca²⁺>Sr²⁺>Ba²⁺. The complex behavior can be rationalized in terms of electrostatic interactions and direct coordination of the cations by the carboxylate groups from the crown ether periphery.     

多组分氧化物Ag－Bi－V－Mo－O催化作用的光电子能谱研究

对于烃类选择氧化反应中复合氧化物的催化作用,普遍认为是Redox机理.迄今对于含有钥、秘复合氧化物催化剂的活性中心和作用机理还存在不同的看法.     

Differentiation of a pair of diastereomeric tertiarybutoxycarbonylprolylproline ethyl esters by collision-induced dissociation of sodium adduct ions in electrospray ionization mass spectrometry and evidence for chiral recognition by ab initio molecular orbital calculations

The fragmentation of the sodium adduct ions for tert-butoxycarbonyl-L-prolyl-L-proline ethyl ester (Boc-L-Pro-L-Pro-OEt) was compared with that for Boc-D-Pro-L-Pro-OEt in positive-ion electrospray ionization (ESI) mass spectrometry. In the collision-induced dissociation (CID) mass spectra of the [M + Na](+) ions, the abundance of the [M + Na - C(CH(3))(3) + H](+) ion, which is due to the loss of a tert-butyl group from the [M + Na](+) ion for Boc-D-Pro-L-Pro-OEt, was about eight times higher than that for Boc-L-Pro-L-Pro-OEt. In addition, in the CID spectra of the sodium adduct fragment ion ([M + Na - Boc + H](+)), the abundance of the [M + Na - Boc - prolylresidue + H](+) ion, which is due to the loss of prolyl residue from the [M + Na - Boc + H](+) ion for Boc-L-Pro-L-Pro-OEt, was about five times higher than that for Boc-D-Pro-L-Pro-OEt. These results indicate that Boc-L-Pro-L-Pro-OEt was distinguished from Boc-D-Pro-L-Pro-OEt by the CID mass spectra of the sodium adduct ions in ESI mass spectrometry. The optimized geometries of the [M + Na](+) and the [M + Na - Boc + H](+) ions calculated by ab initio molecular orbital calculations suggest that the chiral recognition of these diastereomers was due to the difference of the orientation of a sodium ion to the oxygen and nitrogen atoms in dipeptide derivatives, and to the difference of the total energies between them.     

Theoretical study of the gas-phase chemiionization reactions La + O and La + O2

The La + O and La + O 2 chemiionization reactions have been investigated with quantum chemical methods. For La + O 2(X (3)Sigma g) and La + O 2(a (1)Delta g), the chemiionization reaction La + O 2 --> LaO 2 (+) + e (-) has been shown to be endothermic and does not contribute to the experimental chemielectron spectra. For the La + O 2(X (3)Sigma g) reaction conditions, chemielectrons are produced by La + O 2 --> LaO + O, followed by La + O --> LaO (+) + e (-). This is supported by the same chemielectron band, arising from La + O --> LaO (+) + e (-), being observed from both the La + O( (3)P) and La + O 2(X (3)Sigma g) reaction conditions. For La + O 2(a (1)Delta g), a chemielectron band with higher electron kinetic energy than that obtained from La + O 2(X (3)Sigma g) is observed. This is attributed to production of O( (1)D) from the reaction La + O 2(a (1)Delta g) --> LaO + O( (1)D), followed by chemiionization via the reaction La + O( (1)D) --> LaO (+) + e (-). Potential energy curves are computed for a number of states of LaO, LaO* and LaO (+) to establish mechanisms for the observed La + O --> LaO (+) + e (-) chemiionization reactions.