A new fluorescent probe for zinc(II): an 8-hydroxy-5-N,N-dimethylaminosulfonylquinoline-pendant 1,4,7,10-tetraazacyclododecane

A new fluorescent probe for Zn2+, namely, 8-hydroxy-5-N,N-dimethylaminosulfonylquinolin-2-ylmethyl-pendant cyclen (L8), was designed and synthesized (cyclen=1,4,7,10-tetraazacyclododecane). By potentiometric pH, 1H NMR, and UV spectroscopic titrations, the deprotonation constants pKa1-pKa6 of L(8)4 HCl were determined to be <2, <2, <2 (for amino groups of the cyclen and quinoline moieties), 7.19+/-0.05 (for 8-OH of the quinoline moiety), 10.10+/-0.05, and 11.49+/-0.05, respectively, at 25 degrees C with I=0.1 (NaNO3). The results of 1H NMR, potentiometric pH, and UV titrations, as well as single-crystal X-ray diffraction analysis, showed that L8 and Zn2+ form a 1:1 complex [Zn(H-1L8)], in which the 8-OH group of the quinoline ring of L8 is deprotonated and coordinates to Zn2+, in aqueous solution at neutral pH. On addition of one equivalent of Zn2+ and Cd2+, the fluorescence emission of L8 (5 microM) at 512 nm in aqueous solution at pH 7.4 [10 mM HEPES with I=0.1 (NaNO3)] and 25 degrees C increased by factors of 17 and 43, respectively. We found that the cyclen moiety has the unique property of quenching the fluorescence emission of the quinolinol moiety when not complexed with metal cations, but enhancing emission when complexed with Zn2+ or Cd2+. In addition, the Zn2+-L8 complex [Zn(H-1L8)] is much more thermodynamically and kinetically stable (Kd{Zn(H-1L8)}=[Zn2+]free[L8]free/[Zn(H-1L8)]=8 fM at pH 7.4) than the Zn2+ complexes of our previous Zn2+ fluorophores ([Zn(H-1L2)] and [Zn(L3)]). Furthermore, formation of [Zn(H-1L8)] is much faster than those of [Zn(H-1L2)] and [Zn(L3)]. The staining of early-stage apoptotic cells with L8 is also described.     

Microwave-assisted preparations of amidrazones and amidoximes

In an operationally straightforward and efficient method, amidrazones and amidoximes are prepared in yields of 65-87% from imidoylbenzotriazoles by microwave heating for 5-20 min with the appropriate hydrazine or hydroxylamine.     

Monitoring yoctomole alkaline phosphatase by capillary electrophoresis with on-capillary catalysis-electrochemical detection

An electrophoretically mediated microanalysis method for detection of yoctomole (ymol) alkaline phosphatase (ALP) was developed by a combination of on-capillary enzyme-catalyzed reaction and electrochemical detection. In this method, ALP molecules were electrokinetically injected into a capillary of 10 μm i.d. and then electromigrated to the section of the capillary immersed in a warm water bath of 37 °C, where ALP reacted for a certain time with disodium phenyl phosphate as the enzyme substrate. ALP could be measured through determining the electroactive product phenol of the enzyme-catalyzed reaction by using electrochemical detection. The phenol concentration was proportional to the mass of ALP. As a catalyst, ALP was not consumed during the reaction, which provided amplification of signal with prolonged the reaction time. In order to enhance the signal-to-noise ratio, the detection end of the capillary was etched to a horn-shape and a single carbon fiber microcylinder electrode of 6 μm in diameter as the working electrode was inserted into the detection end of the capillary. Under these conditions, the mass of ALP as low as 1.2 × 10⁻²² mol (72 molecules) or 4.0 × 10⁻²³ mol (24 molecules) could be detected for the on-capillary reaction time of 15 min or 2 h.     

Towards a force field based on density fitting

Total intermolecular interaction energies are determined with a first version of the Gaussian electrostatic model (GEM-0), a force field based on a density fitting approach using s-type Gaussian functions. The total interaction energy is computed in the spirit of the sum of interacting fragment ab initio (SIBFA) force field by separately evaluating each one of its components: electrostatic (Coulomb), exchange repulsion, polarization, and charge transfer intermolecular interaction energies, in order to reproduce reference constrained space orbital variation (CSOV) energy decomposition calculations at the B3LYP/aug-cc-pVTZ level. The use of an auxiliary basis set restricted to spherical Gaussian functions facilitates the rotation of the fitted densities of rigid fragments and enables a fast and accurate density fitting evaluation of Coulomb and exchange-repulsion energy, the latter using the overlap model introduced by Wheatley and Price [Mol. Phys. 69, 50718 (1990)]. The SIBFA energy scheme for polarization and charge transfer has been implemented using the electric fields and electrostatic potentials generated by the fitted densities. GEM-0 has been tested on ten stationary points of the water dimer potential energy surface and on three water clusters (n = 16,20,64). The results show very good agreement with density functional theory calculations, reproducing the individual CSOV energy contributions for a given interaction as well as the B3LYP total interaction energies with errors below kBT at room temperature. Preliminary results for Coulomb and exchange-repulsion energies of metal cation complexes and coupled cluster singles doubles electron densities are discussed.     

Photo-control of kinesin-microtubule motility using caged peptides derived from the kinesin C-terminus domain

To design a nanoscale biodevice that can be controlled by an external stimulus, we have introduced photochemical switching peptides derived from the kinesin C-terminus domain into the kinesin-microtubule in vitro motility system.     

Fluorescent detection for cyclic and acyclic alcohol guests by naphthalene-appended amino-beta-cyclodextrins

Spectroscopic and thermodynamic investigations on complexation of naphthalene-appended amino-beta-cyclodextrins 1 and 2 with cyclic alcohols (cyclohexanol and cycloheptanol) and acyclic alcohols (1-pentanol, 2-pentanol, 1-hexanol, and 1-heptanol) have been carried out. Host 1 exhibits a drastic fluorescent enhanced-signal change in the presence of alcohol guests in aqueous solution. [structure: see text]     

A new cycloartane glycoside from Camptosorus sibiricus Rupr

A new cycloartane glycoside was isolated from the dried aerial parts of Camptosorus sibiricus Rupr. By means of chemical and spectroscopic methods (IR, 1D and 2D NMR, ESI-MS), the structure was established as 3beta, 7beta, 24beta, 25, 30-pentahydroxycycloartane-3-O-beta-D-glucopyranoside-24-O-beta-D-glucopyranosyl(1 --> 2)-D-glucopyranoside (1).     

Enzyme biosensors based on ion-selective field-effect transistors

The key theoretical principles of the work on ion-selective field-effect transistor connected with their application in bioanalytical practice, some specifics of modern microtechnologies for their creation, and measurement schemes with set-ups are discussed. The achievements in the creation of enzyme biosensors based on ion-selective field-effect transistors and prospects for their application are described in detail.     

Detection of Exposure to Environmental Pesticides During Pregnancy by the Analysis of Maternal Hair Using GC–MS

Several classes of pesticides were extracted from maternal hair by solid-liquid extraction. Analysis of their selected metabolites involved a methanolic/hydrochloric acid methyl ester derivatization and liquid-liquid extraction. Gas chromatography electron impact mass spectrometry was used to detect and quantify the pesticides and metabolites. Recovery of parent compounds and metabolites from the analysis of spiked hair ranged from 87 to 112% with coefficients of variation less than 11%. Limits of detection ranged from 0.031 to 5.88 μg g(-1). Analysis of hair samples from pregnant women in the Philippines showed maternal exposure during pregnancy to bioallethrin, propoxur, chlorpyrifos, pretilachlor and malathion.     

Confined helium atom low-lying S states analyzed through correlated Hylleraas wave functions and the Kohn-Sham model

Calculation including the electron correlation effects is reported for the ground 1 1S and lowest triplet 1 3S state energies of the confined helium atom placed at the center of an impenetrable spherical box. While the adopted wave-functional treatment involves optimization of three nonlinear parameters and 10, 20, and 40 linear coefficients contained in wave functions expressed in a generalized Hylleraas basis set that explicitly incorporates the interelectronic distance r12, via a Slater-type exponent and through polynomial terms entering the expansion, the Kohn-Sham model employed here uses the Perdew and Wang exchange-correlation functional in its spin-polarized version within the local-density approximation (LDA) with and without the self-interaction correction. All these calculations predict a systematic increase in the singlet-triplet energy splitting toward the high confinement regime, i.e., when the box radius is reduced. By using the variational results as benchmark, it is found that the LDA underestimates the singlet-triplet energy splitting, whereas the self-interaction correction overestimates such a quantity.