Stepwise assembly of linearly-aligned Ru-M-Ru (M = Pd, Pt) heterotrimetallic complexes with sigma-4-ethynylpyridine spacer

Two heterotrinuclear oligomeric complexes [trans-RuCl(C[triple bond, length as m-dash]Cpy-4)(dppm)(2)](2)[MCl(2)] (M = Pd ; M = Pt ) are prepared from the metalloligand trans-[RuCl(C[triple bond, length as m-dash]Cpy-4)(dppm)(2)] (dppm = Ph(2)PCH(2)PPh(2), ). The resultant linear alignment of the metals [Ru-M-Ru] is imposed by a combinative use of trans-directed spacers and planar metals with trans-juxtaposed donor sites. Ligand exchange of with [Pd(CH(3)CN)(4)][PF(6)](2) gives trans-[Ru(CH(3)CN)(C[triple bond, length as m-dash]Cpy-4)(dppm)(2)][PF(6)] (). All complexes are characterized by single-crystal X-ray crystallography and solution spectroscopy. Acid-base titration on suggested protonation of the pendant pyridyl. Complexes and also undergo protonation at the C[triple bond, length as m-dash]C moiety under acid conditions. The inter-conversion of alkynyl and vinylidene functionality is described. The dual acid and base characters of makes it a potential metalloligand towards basic and acidic fragments in multinuclear heterometallic assemblies.     

Charge‐Tagged DNA Radicals in the Gas Phase Characterized by UV/Vis Photodissociation Action Spectroscopy

Adenosine radicals tagged with a fixed‐charge group were generated in the gas phase and structurally characterized by tandem mass spectrometry, deuterium labeling, and UV/Vis action spectroscopy. Experimental results in combination with Born–Oppenheimer molecular dynamics, ab initio, and excited‐state calculations led to unambiguous assignment of adenosine radicals as N‐7 hydrogen atom adducts. The charge‐tagged radicals were found to be electronically equivalent to natural DNA nucleoside radicals.     

Stationary phase-based two-dimensional chromatography combining both covalent and noncovalent interactions on a single HPLC column

A new type of 2-D separation material was synthesized and studied. The material is suitable for 2-D chromatography utilizing both covalent and noncovalent interactions. The first dimension is boronate affinity chromatography, and the second dimension is RP chromatography (or vice versa). The polymeric media were prepared using p-vinylphenylboronic acid as the functional monomer. This monomer was selected due to the presence of the boronic acid group for the cis-diol/boronate interaction in boronate chromatography. Two crosslinkers were evaluated, namely ethylene glycol dimethacrylate and divinylbenzene. The crosslinker content was varied to maximize the polymer strength and the RP performance of the packed column. Several parameters were evaluated to define the optimum for polymer strength and column performance including crosslinker, porogen, initiator, and column-packing parameters. The polymer-based HPLC columns were successful in separating phenol, catechol, dimethylphthalate, and hydroquinone under RP conditions, and thus can be used as an RP HPLC column. The columns were also successful in separating catechol and adenosine under boronate chromatography conditions, and thus can be used as a boronate affinity column. Moreover, the two types of chromatography can be performed consecutively on the same column during one complete chromatographic run, making it a 2-D chromatography. Under these 2-D conditions, the catechol was separated from a mixture of phenol, catechol, dimethylphthalate, and hydroquinone; the adenosine ribonucleoside was separated from a mixture of adenosine ribonucleoside, adenosine deoxyribonucleoside, and uridine deoxyribonucleoside. This type of single-column 2-D HPLC eliminates the requirement of a complex and expensive multidimensional HPLC instrument and provides increased peak capacity for separation.     

Selective glucose sensing in complex media using a biomimetic receptor

Glucose is a key biomedical analyte, especially relevant to the management of diabetes. Current methods for glucose determination rely on the enzyme glucose oxidase, requiring specialist instrumentation and suffering from redox-active interferents. In a new approach, a powerful and highly selective achiral glucose receptor is mixed with a sample, l-glucose is added, and the induced CD spectrum is measured. The CD signal results from competition between the enantiomers, and is used to determine the d-glucose content. The involvement of l-glucose doubles the signal range from the CD spectrometer and allows sensitivity to be adjusted over a wide dynamic range. It also negates medium effects, which must be equal for both enantiomers. The method has been demonstrated with human serum, pre-filtered to remove proteins, giving results which closely match the standard biochemical procedures, as well as a cell culture medium and a beer sample containing high (70 mM) and low (0.4 mM) glucose concentrations respectively.

A highly selective receptor, circular dichroism and chiral competition are combined in this versatile method for d-glucose analysis.     

Matrix diversion methods for improved analysis of perchlorate by suppressed ion chromatography and conductivity detection

Two inline matrix diversion methods were developed for the sensitive analysis of perchlorate in a matrix comprising up to 1000 mg l⁻¹ of chloride, sulfate and bicarbonate ions using suppressed ion chromatography and conductivity detection. The first method used a cryptand C1 concentrator column, which exhibited a high selectivity for perchlorate ion over the other matrix anions. After retaining the sample anions in a concentrator column derivatized with a crytpand phase, a rinse step was implemented with a weak base to divert the matrix ions to waste while selectively retaining perchlorate in the concentrator column for subsequent analysis. The analysis was done using a 2 mm IonPac^® AS16 or 2 mm IonPac^® AS20 separator column. The second method was a two-dimensional matrix diversion method with a focus on improving the detection sensitivity. The first dimension was used to achieve some resolution of the matrix ions from perchlorate. The perchlorate ion was then diverted into a concentrator column for subsequent analysis in the second dimension. By pursuing analysis using a 4 mm IonPac^® AS16 or IonPac^® AS20 column in the first dimension and subsequently pursuing analysis using a 2 mm IonPac^® AS16 or IonPac^® AS20 column format, excellent sensitivities were achieved when the first and second dimensions were operated at the same linear flow velocity (cm min⁻¹). While sensitive detection of perchlorate in the low μg l⁻¹ regime was achieved by the above methods in the presence of matrix ions, superior recovery for perchlorate was demonstrated under a variety of matrix concentrations by the second method.     

酪氨酸磷酸化多肽的化学选择性富集

酪氨酸激酶在生物分子的信号转导中起着非常重要的作用,目前除抗体技术外尚无有效的化学方法能够实现对酪氨酸磷酸化蛋白或多肽的选择性富集,然而抗体通常成本较高,而且往往会有模体序列的选择性识别。本文发展了一种基于化学反应的酪氨酸磷酸化肽段的选择性富集,该方法利用了β消除反应只能发生在丝氨酸和苏氨酸磷酸化多肽的特性,以反相选择方法,从而实现对酪氨酸磷酸化肽段的选择性富集。以标准多肽对其反应效率和回收率进行了考察,20分钟内丝氨酸磷酸化多肽的β消除反应效率可达99%以上,而同时酪氨酸磷酸化肽段可保持70%的回收率。进一步以六种标准蛋白混合物的酶解产物对其进行考察,经β消除反应和亲和富集之后,只有酪氨酸磷酸化多肽可以被检测出来,该方法为蛋白质酪氨酸磷酸化的分析提供了一种新的手段。     

First fluorescence spectroscopic investigation of Am(III) complexation with an organic carboxylic ligand, pyromellitic acid

For the first time Am(III) complexation with a small organic ligand could be identified and characterized with time-resolved laser-induced fluorescence spectroscopy (TRLFS) at room temperature and trace metal concentration. With pyromellitic acid (1,2,4,5-benzene-tetracarboxylic acid, BTC) as ligand spectroscopic characteristics for the Am-BTC complex system were determined at pH 5.0, an ionic strength of 0.1 M (NaClO4) and room temperature. The fluorescence lifetimes were determined to be 23.2±2.2 ns for Am3+(aq) and 27.2±1.2 ns for the Am-BTC 1:1 complex; the emission maximum for the 5D1-(7)F1 transition is 691 nm for both species. The complex stability constant for the Am-BTC 1:1 complex was calculated to be logβ110=5.42±0.16.     

Application of Phosphorus-31 Nuclear Magnetic Resonance Spectrosocopy for the Study of Human Diabetic Cataractogenesis

Intact human Senses incubated at 5.5 mM (normal) and 35.5 mM glucose were examined by phosphorus-31 nuclear magnetic resonance (31P NMR) spectroscopy. Lense in 35.5 mM glucose showed an altered metabolic steady-state characterized by a lowered adenosine triphosphate/inorganic orthophosphate ratio. ³¹P NMR spectroscopy can be used to measure metabolic changes in the lens. This model offers an important means to study dynamic metabolism in the human lens in the setting of diabetic cataractogenesis.     

High capacity, charge-selective protein uptake by polyelectrolyte brushes

Surface plasmon resonance was used to measure binding of proteins from solution to poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) brushes end-grafted from gold surfaces by atom transfer radical polymerization (ATRP). PDMAEMA brushes were prepared with a variety of grafting densities and degrees of polymerization. These brushes displayed charge selective protein uptake. The extent of uptake for net negatively charged bovine serum albumin (BSA) scaled linearly with the surface mass concentration of grafted PDMAEMA, regardless of grafting density. BSA was bound at a constant ratio of 120 DMAEMA monomer units per protein molecule for all brushes examined. The equivalent three-dimensional concentration of BSA bound in the brush (i.e., the bound BSA surface excess concentration divided by the brush thickness) decreased monotonically with decreasing grafting density. The concentration of BSA bound within brushes prepared at higher grafting densities was comparable with the aqueous protein solubility limit. BSA desorption from the brush required changes in solution pH and/or ionic strength to eliminate its net electrostatic attraction to PDMAEMA. Net positively charged lysozyme was completely rejected by the PDMAEMA brushes.