Stabilities of ion/radical adducts in the liquid phase as derived from the dependence of electrochemical cleavage reactivities upon solvent.

The idea that significant ion/radical interactions should vary with solvent if they do exist in the liquid phase was pursued by an investigation of the dissociative electron-transfer reactivity of carbon tetrachloride and 4-cyanobenzyl chloride in four different solvents, 1,2-dichloroethane, N,N-dimethylformamide, ethanol, and formamide, by means of their cyclic voltammetric responses. Modification of the conventional dissociative electron transfer theory to take account of an interaction between fragments in the ion/radical pair resulting from the dissociative electron reaction allows a satisfactory fitting of the experimental data leading to the determination of the interaction energy. There is an approximate correlation between the interaction energies in the ion/radical pair and the solvation free energies of the leaving anion, Cl(-). The interaction is maximal in 1,2-dichloroethane, which is both the least polar and the least able to solvate Cl(-). The interaction is smaller in the polar solvents, albeit distinctly measurable. The two protic solvents, ethanol and formamide, which are the most able to solvate Cl(-), give rise to similar interaction energies. The interaction is definitely stronger in N,N-dimethylformamide, which has a lesser ability to solvate Cl(-) than the two other polar solvents. The existence of significant ion/radical interactions in polar media is thus confirmed and a route to their determination opened.     

Synthesis and photochromism of spirobenzopyran derivatives bearing an oxymethylcrown ether moiety: metal ion-induced switching between positive and negative photochromisms

Spirobenzopyran derivatives carrying an oxymethylcrown ether moiety were synthesized, and their photochromism was studied in the presence of various metal ions in acetonitrile. The metal ion complexing ability of the crown ether moiety in crowned spirobenzopyrans affects both thermal isomerization and photoisomerization of their spirobenzopyran moiety to a great extent. When the interaction of the crown ether moiety with a metal ion was strong enough to cause thermal isomerization of the spirobenzopyran moiety to its corresponding merocyanine form and to suppress UV-induced isomerization to the merocyanine form, a negative photochromism appears. On the other hand, a relatively weak interaction of the crown ether moiety with a metal ion affords a positive photochromism. This phenomenon enables us to switch the photochromic behavior between positive and negative photochromisms.     

亲和毛细管电泳法研究锌离子与人血清白蛋白的结合反应机制

建立了研究金属离子与人血清白蛋白(Human serum albumin,HSA)相互作用的亲和毛细管电泳(Affinity capillary electrophoresis,ACE)方法。生理条件下,构建配体(Zn2+)-受体(HSA)相互作用模型,以N,N-二甲基甲酰胺(N,N-Dimethylformamide,DMF)为内标物,基于Scatchard方程,依据有效淌度的变化,通过非线性模拟方程计算Zn2+-HSA结合反应的表观结合常数KB,定量表征了Zn2+-HSA相互作用的强度,并解析电泳谱图获得了Zn2+-HSA结合反应为一快平衡体系的结论。结果表明,建立的ACE方法简捷、有效,Zn2+-HSA相互作用的强度与Zn2+浓度之间存在明显的量效关系。     

Calculating critical relative humidity from solubility according to Pitzer ion interaction model

The solubility and the critical relative humidity (H(cr)) of 14 drugs and inorganic salts were determined, the relationship between the H(cr) and the solubility was explored theoretically, and the H(cr) was calculated in the light of Raoult's law and Pitzer ion interaction model from their solubility. The results indicate that the H(cr) values calculated by Raoult's law in high humidity (H(cr)>80%) and by Pitzer ion interaction model in low humidity (H(cr)<80%) are comparable to the measured ones.     

Retention of opioids and their glucuronides on a combined zwitterion and hydrophilic interaction stationary phase

A stationary phase combining zwitterionic ion chromatography and hydrophilic interaction chromatography (ZIC-HILIC) from SeQuant was evaluated for the chromatography of some opiates and their polar metabolites. The effects of mobile phase constitution on retention and resolution were extensively evaluated. Different aspects of mobile phase constitution such as ion strength and type of buffer, type and amount of organic modifier and pH were examined. The selectivity and retention of the opiates compared to their glucuronides could be substantially altered with small changes of the mobile phase, especially when the type of buffer, i.e., formate or acetate and organic modifier, i.e., acetonitrile or methanol were changed. The retention on the ZIC-HILIC was dominated by hydrophilic interaction chromatography (HILIC) but considerable effects on the selectivity was observed, possibly caused by an ion exchange mechanism due to interactions with the charges on the stationary phase.     

Interaction of diquat and paraquat with humic acid and the influence of salt concentration and pH on the strength of interaction

Summary The interaction of the herbicides diquat and paraquat with humic acid and the influence of various salts and pH on the strength of interaction was studied by charge-transfer chromatography. Interactions between humic acids and both herbicides, probably by complex formation, were confirmed; they were stronger with paraquat than with diquat. The complex formation makes the herbicides more hydrophilic, facilitating their movement on cellulose surface. Salts in the environment significantly decreased the strength of interaction, indicating the hydrophilic character of the interactive forces. The charge of the cation also influenced the strength of interaction whereas the effect of ion radii was negligible. The effect of pH was lower than that of salt concentration.     

Quantum-Chemical Study of the Adsorption of Pb2+ on Au(111)

The interaction between the Pb²⁺ ion and gold is studied using the cluster metal surface model and the density functional method. The geometric and energy characteristics of the interaction between this ion and the gold surface are estimated. The form in which the Pb²⁺ ion exists on the surface is more ad-ionic than ad-atomic. The electron structure of the Au–Pb_ads²⁺ system is analyzed. The participation of the adsorbed lead ion and its neighboring gold atoms in the formation of molecular orbitals in this system is estimated. It is established that the contribution to their formation is predominantly provided by the lead s-orbitals and the gold d-orbitals. The interaction with a solvent decreases the transfer of a charge from an adsorbed lead ion to gold. It is demonstrated that the hydrolyzability of a lead ion decreases upon its transition from the electrolyte phase to the surface.

     

Retention of β blockers on native titania stationary phase

In recent years, metal oxides such as titania have been commercially available as chromatographic beds that can potentially be used to achieve novel separations of polar compounds. For example β blockers, which are more often encountered in environmental sciences, have a wide range of polarity, and their basic character leads to difficult sample treatment and separation on conventional silica‐based sorbents. The contribution of titania to the selective analysis of nine β blockers was evaluated in terms of retention mechanisms observed in hydrophilic interaction LC using acetonitrile/water mobile phases with various additives. The mobile phase additives enabled to control the β blocker charge as well as the titania surface charge. Depending on their respective ionic state, various retention mechanisms were identified at low water contents (<40%), including mainly adsorption mixed with hydrophilic interaction LC partition, ion exchange and ion exclusion. An unexpected retention was also observed for high water content and high pH, changing the selectivity of the support.     

Theory of peak coalescence in Fourier transform ion cyclotron resonance mass spectrometry

Peak coalescence, i.e. the merging of two close peaks in a Fourier transform ion cyclotron resonance (FTICR) mass spectrum at a high number of ions, plays an important role in various FTICR experiments. In order to describe the coalescence phenomenon we would like to propose a new theory of motion for ion clouds with close mass‐to‐charge ratios, driven by a uniform magnetic field and Coulomb interactions between the clouds. We describe the motion of the ion clouds in terms of their averaged drift motion in crossed magnetic and electric fields. The ion clouds are considered to be of constant size and their motion is studied in two dimensions. The theory deals with the first‐order approximation of the equations of motion in relation to dm/m, where dm is the mass difference and m is the mass of a single ion. The analysis was done for an arbitrary inter‐cloud interaction potential, which makes it possible to analyze finite‐size ion clouds of any shape. The final analytical expression for the condition of the onset of coalescence is found for the case of uniformly charged spheres. An algorithm for finding this condition for an arbitrary interaction potential is proposed. The critical number of ions for the peak coalescence to take place is shown to depend quadratically on the magnetic field strength and to be proportional to the cyclotron radius and inversely proportional to the ion masses. Copyright © 2009 John Wiley & Sons, Ltd.     

含离子聚合物体系的动力学

离子作用的可逆性赋予了含离子聚合物丰富的力学和电学性能,使其广泛应用在高抗冲材料、记忆材料、自修复材料和智能响应材料等新兴领域.本专论结合作者近年的研究工作,介绍了含离子聚合物体系的构效关系和分子流变学,从3个方面展开:第1部分介绍了对于含离子聚合物的离子聚集状态的调控,和离聚物与聚电解质的相互转化;第2部分介绍了离子高度聚集的无规离聚物丰富的线性黏弹性,重点介绍了非缠结体系在链均一个离子浓度附近区域的溶胶凝胶转变以及缠结体系在平均每个缠结链段一个离子浓度附近区域的单平台到双平台模量的转变;第3部分介绍了如何进行分子设计,使得含离子聚合物成为有效的离子传输介质.最后总结了该研究领域的科学问题和面临的挑战.     

金属离子对溴碘化银乳剂微晶体的掺杂效应 Ⅲ.Cu2+的掺杂

在本工作中,用电镜法、介电损耗法和微波光导法研究了铜离子的掺杂对于卤化银乳剂微晶体的掺杂效应。试验结果表明,铜离子的掺杂使卤化银乳剂微晶体的颗粒变小,使微晶体的介电损耗峰向高频方向稍微移动0.3对数单位。使微晶体的光电导急剧地降低。实验证明,铜离子吸附在卤化银乳剂微晶体的表面,起着深电子陷阱的作用,是导致铜离子的掺杂使乳剂的感光度降低的主要原因。     

Double-armed crown ethers: synergic pi-coordination effect on potentiometric sensing for Ag(I)

Three diaza-18-crown-6 derivatives having methyl (L1), methoxy (L2) and phenyl (L3) end-groups in para-substituted phenolic side-arms have been investigated as potentiometric sensing materials for silver(I)-selective poly(vinyl chloride) membrane electrodes. The aim of the present work is to establish whether a combination of macrocyclic coordination to Ag+ ion and Ag-pi interaction might produce synergic effect in Ag+ ion sensing. The electrode based on the aromatic end-groups, L3 was found to give remarkably better electrochemical performance than their aliphatic counterparts (L1 and L2). The sensing ability for Ag+ ion with the proposed electrode was enhanced noticeably due to the pi-coordination of Ag+ ion, which was elucidated by NMR. The present findings may serve as an alternative approach for designing advanced sensing materials.     

The microenvironment of DNA switches the activity of singlet oxygen generation photosensitized by berberine and palmatine

The effect of the interaction between DNA and the photosensitizer on photosensitized singlet oxygen (1O2) generation was investigated using DNA-binding alkaloids, berberine and palmatine. These photosensitizers were bound to DNA by electrostatic force. Near-infrared luminescence measurement demonstrated that the photoexcited alkaloids can generate 1O2 only when the photosensitizers are bound to DNA. A fluorescence decay study showed significant enhancement of the lifetime of their photoexcited state with the DNA binding. A calculation study suggested that the electrostatic interaction with DNA inhibits the quenching of the photoexcited state of these alkaloids via intramolecular electron transfer, leading to the prolongation of the lifetime of their excited state. This effect should enhance their intersystem crossing and the yield of energy transfer to molecular oxygen. The results show that the electrostatic interaction with DNA significantly affects the 1O2 generation activity of a photosensitizer. In addition, this interaction may be applied to the control and the design of photosensitizers for medical applications such as photodynamic therapy.     

铕苯丙氨酸配合物与DNA相互作用的循环伏安法和紫外光谱法研究

运用循环伏安法和紫外光谱法研究了Ｅｕ（ｐｈｅ）３＾３＋与ＤＮＡ的相互作用。Ｅｕ（ｐｈｅ）３＾３＋与ＤＮＡ作用后，循环伏安曲线的峰电流密度减小，峰电位差稍有增中，扩散系数减小，紫外光谱的特征吸收峰呈明显的减色效应，这可能是Ｅｕ（ｐｈｅ）３＾３＋与ＤＮＡ因静电引力形成加合物以及Ｅｕ（ｐｈｅ）３＾３＋有很强的遮蔽负电荷 作用，促使碱基面与碱基面的进一步堆积所致。     

7-Methylguanine nucleotides and their structural analogues; protolytic equilibria, complexing with magnesium (II) ion and kinetics for alkaline opening of the imidazole ring

First-order rate constants for the alkaline opening of the imidazole ring of several 7-methylguanine nucleotides and their structural analogues were determined. The results obtained suggested that intramolecular interaction between the negatively charged 5'-phosphate group and the positively charged imidazole ring markedly retard the attack of hydroxide ion on the C8 atom of the 7-methylguanine ring. In contrast, hardly any influence on the acidities of the interacting base and phosphate moieties was detectable. No effect on the complexing of the phosphate group with magnesium(II) ion could be detected.     

An empirical potential function for the interaction between univalent ions in water

A hydration-shell model has been developed for calculating the interaction energy between ions in water. The hydration shell around each ion contains a few tightly bound water molecules and a larger number of less tightly bound molecules. The energies of their interaction with the ion and the size of the hydration shell have been derived from published experimental data for ion-water clusters in the gas phase. An expression derived for the interaction energy of two univalent ions in water incorporates the following effects: a Lennard-Jones 6–12 interaction, a Coulomb interaction between the charges, the polarization of the hydration shells by a neighboring ion, and an energy term for the removal of water from the hydration shells when the hydration shells of two ions overlap. The effective dielectric constant at small ion-ion distances is the only adjustable parameter. Computed interaction energies for aqueous solutions of twelve alkali halides match experimental values, derived from conductimetric measurements, with an average error of ±14%.     

Separation of Rare Earth Elements (REE) by Ion Interaction Chromatography (IIC) Using Diglycolic Acid (ODA) as a Complexing Agent

Chromatographia - The possibility of rare earth elements (REE) separation by ion interaction chromatography (IIC) employing their complexes with diglycolic acid (ODA) in anion exchange mode has...     

Correlated ab initio quantum chemical study of the interaction of the Na+, Mg2+, Ca2+, and Zn2+ ions with the tautomers of cytosine

The interaction of the metal ions Na(+), Mg(2+), Ca(2+), and Zn(2+) with cytosine have been reinvestigated at the density functional, M?ller-Plesset, and coupled cluster levels of theory, including hitherto unstudied tautomeric forms. It has been found that the interaction of the metal ion has a varying and often significant effect on the stabilities of the various tautomers, in some cases making most stable rare tautomeric forms. The results have been analyzed with respect to method and role of ion in binding, and confirm that, as has been found for the base cytosine tautomers, B3LYP does not give energetics consistent with highly accurate post-SCF methods for their interaction with these metal ions.     

Retention of glycopeptides analyzed using hydrophilic interaction chromatography is influenced by charge and carbon chain length of ion‐pairing reagent for mobile phase

Characterization of the glycans of glycoproteins is essential for the development and production of biologics. Numerous methods are available for analyzing the glycans of glycoproteins directly and labeled glycans. Nevertheless, glycopeptides are difficult to resolve because of their exceptional complexity and the microheterogeneity of glycans. These properties represent technical challenges to efforts to insure the accurate characterization of biopharmaceuticals to comply with regulatory requirements. Therefore, we investigated the retention behavior of peptides and glycopeptides in hydrophilic interaction chromatography‐mode HPLC in the presence of ion‐pairing reagents. Anionic ion‐pairing reagents decreased the retention times of glycopeptides and improved resolution in the presence of higher concentrations or hydrophobicities of ion‐pairing reagent. Anionic ion‐pairing reagents increased retention times of larger glycans because of their increased hydrophilicity. In contrast, in the presence of cationic ion‐pairing reagents, the retention times of glycopeptides with greater numbers of sialic acid residues decreased. It is appropriate to add an anionic ion‐pairing reagent to the mobile phase for good separation of glycopeptides. The collision cross‐sectional area values of glycopeptides determined using electrospray ionization‐ion mobility spectrometry‐mass spectrometry correlated with retention times. These findings support the implementation of hydrophilic interaction chromatography‐mode HPLC to improve the characterization of glycosylated biopharmaceuticals.     

Comprehensive analysis of fatty alcohol ethoxylates by ultra high pressure hydrophilic interaction chromatography coupled with ion mobility spectrometry mass spectrometry using a custom‐designed sub‐2 μm column

Comprehensive analysis of fatty alcohol ethoxylates has been conducted by coupling ultra high pressure hydrophilic interaction chromatography and ion mobility spectrometry mass spectrometry. A custom‐designed sub‐2 μm column was used for the chromatographic separation of fatty alcohol ethoxylates by hydrophilic interaction chromatography. Ion mobility spectrometry provided a post‐ionization resolution during a very short period of 6.4 ms. Distinguishable families of singly, doubly, and triply charged fatty alcohol ethoxylates were clearly observed. By virtue of the combination of hydrophilic interaction chromatography and ion mobility spectrometry, comprehensive resolution based on both hydrophobicity difference and mobility disparity has been achieved for fatty alcohol ethoxylates. The orthogonality of the developed separation and analysis system was evaluated with the correlation coefficient and peak spreading angle of 0.0224 and 88.72°, respectively. The actual peak capacity obtained was individually 40 and 193 times than those when hydrophilic interaction chromatography and ion mobility spectrometry were used alone. The collision cross‐sections of fatty alcohol ethoxylates were calculated by calibrating the traveling wave ion mobility device with polyalanine.