Photobiological impact of [{(bpy)2Ru(dpp)}2RhCl2]Cl5 and [{(bpy)2Os(dpp)}2RhCl2]Cl5 [bpy=2,2'-bipyridine; dpp=2,3-Bis(2-pyridyl)pyrazine] on vero cells

The in vitro photobiology of the supramolecular complexes [{(bpy)2Ru(dpp)}2RhCl2]Cl5 and [{(bpy)2Os(dpp)}2RhCl2]Cl5 [bpy=2,2'-bipyridine; dpp=2,3-bis(2-pyridyl)pyrazine] with African green monkey kidney epithelial (Vero) cells was investigated. Previously, the complexes have been shown to photocleave DNA in the presence or absence of O2. Vero cell replication was uninhibited for cells exposed to the metal complex but protected from light. Vero cells that were exposed to metal complex, rinsed, and illuminated with >460 nm light showed a replication response that was metal complex concentration-dependent. Vero cells exposed to 3.0-120 microM [{(bpy)2Ru(dpp)}2RhCl2]Cl5 and illuminated showed inhibition of cell growth, with evidence of cell death seen for complex concentrations>or=10 microM. Cells exposed to [{(bpy)2Os(dpp)}2RhCl2]Cl5 at concentrations of 5.5-110 microM, rinsed, and illuminated showed only inhibition of cell growth. The impact of [{(bpy)2Ru(dpp)}2RhCl2]Cl5 and [{(bpy)2Os(dpp)}2RhCl2]Cl5 on cell growth following illumination shows the promise of this new structural motif as a photodynamic therapy agent.     

URB602 inhibits monoacylglycerol lipase and selectively blocks 2-arachidonoylglycerol degradation in intact brain slices

The N-aryl carbamate URB602 (biphenyl-3-ylcarbamic acid cyclohexyl ester) is an inhibitor of monoacylglycerol lipase (MGL), a serine hydrolase involved in the biological deactivation of the endocannabinoid 2-arachidonoyl-sn-glycerol (2-AG). Here, we investigated the mechanism by which URB602 inhibits purified recombinant rat MGL by using a combination of biochemical and structure-activity relationship (SAR) approaches. We found that URB602 weakly inhibits recombinant MGL (IC(50) = 223 +/- 63 microM) through a rapid and noncompetitive mechanism. Dialysis experiments and SAR analyses suggest that URB602 acts through a partially reversible mechanism rather than by irreversible carbamoylation of MGL. Finally, URB602 (100 microM) elevates 2-AG levels in hippocampal slice cultures without affecting levels of other endocannabinoid-related substances. Thus, URB602 may provide a useful tool by which to investigate the physiological roles of 2-AG and explore the potential interest of MGL as a therapeutic target.     

IR-IR-UV hole-burning: conformation specific IR spectra in the face of UV spectral overlap

A new technique, IR-IR-UV hole-burning, is reported for obtaining conformation specific IR spectra when the electronic spectra are too closely overlapped to obtain clean spectra free from interference from other conformations via standard ion dip or fluorescence dip methods. The 4'-aminobenzo-15-crown-5 ether-(HDO) complex is used as an example, on which the method was applied to prove the presence of two conformations having overlapped electronic spectra and to assign IR transitions belonging to the same conformation.     

Ordered adsorption of coagulation factor XII on negatively charged polymer surfaces probed by sum frequency generation vibrational spectroscopy

Electrostatic interactions between negatively charged polymer surfaces and factor XII (FXII), a blood coagulation factor, were investigated by sum frequency generation (SFG) vibrational spectroscopy, supplemented by several analytical techniques including attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), quartz crystal microbalance (QCM), ζ-potential measurement, and chromogenic assay. A series of sulfonated polystyrenes (sPS) with different sulfonation levels were synthesized as model surfaces with different surface charge densities. SFG spectra collected from FXII adsorbed onto PS and sPS surfaces with different surface charge densities showed remarkable differences in spectral features and especially in spectral intensity. Chromogenic assay experiments showed that highly charged sPS surfaces induced FXII autoactivation. ATR-FTIR and QCM results indicated that adsorption amounts on the PS and sPS surfaces were similar even though the surface charge densities were different. No significant conformational change was observed from FXII adsorbed onto surfaces studied. Using theoretical calculations, the possible contribution from the third-order nonlinear optical effect induced by the surface electric field was evaluated, and it was found to be unable to yield the SFG signal enhancement observed. Therefore it was concluded that the adsorbed FXII orientation and ordering were the main reasons for the remarkable SFG amide I signal increase on sPS surfaces. These investigations indicate that negatively charged surfaces facilitate or induce FXII autoactivation on the molecular level by imposing specific orientation and ordering on the adsorbed protein molecules. Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users.     

Determination of aripiprazole in rat plasma and brain using ultra-performance liquid chromatography/electrospray ionization tandem mass spectrometry

Aripiprazole is an important antipsychotic drug. A simple, sensitive and rapid ultra‐performance liquid chromatography/electrospray ionization tandem mass spectrometry (UPLC‐ESI‐MS/MS) method was developed and validated for the simultaneous quantification of this compound in rat plasma and brain homogenate. The analyte was extracted from rat plasma and brain homogenate using a weak cation exchange mixed‐mode resin‐based solid phase extraction. The compound was separated on an Agilent Eclipse Plus C₁₈ (2.1 × 50 mm, 1.8 µm) column using a mobile phase of (A) 0.1% formic acid aqueous and (B) acetonitrile with gradient elution. The analyte was detected in positive ion mode using multiple reaction monitoring. The method was validated and the specificity, linearity, limit of quantitation (LOQ), precision, accuracy, recoveries and stability were determined. The LOQ was 0.5 ng/mL for aripiprazole in plasma and 1.5 ng/g in brain tissue. The MS response was linear over the concentration range 0.5–100 ng/mL for aripiprazole in plasma and 1.5–300 ng/g in brain tissue. The precision and accuracy for intra‐day and inter‐day were better than 14%. The relative and absolute recoveries were above 72% and the matrix effects were low. This validated method was successfully used to quantify the rat plasma and brain tissue concentrations of the analyte following chronic treatment with aripiprazole. Copyright © 2012 John Wiley & Sons, Ltd.     

Ion scattering and X-ray photoelectron spectroscopy of copper overlayers vacuum deposited onto mercaptohexadecanoic acid self-assembled monolayers

Metal overlayers deposited in vacuum onto self-assembled monolayer (SAM) systems serve as models for more complex metalized polymers. Metals (M) deposited onto SAMs with different organic functional end groups exhibit a wide range of behavior, ranging from strong chemical interactions with the end group to complete penetration of the metal through the SAM. In this work, we have characterized the interactions of Cu with the ---COOH of mercaptohexadecanoic acid (MHA, HOOC(CH₂)₁₅SH) SAMs self assembled on gold films by using X-ray photoelectron spectroscopy (XPS) to examine the chemical interactions, and a combination of XPS and ion scattering spectroscopy (ISS) to deduce the growth mode and penetration rate of the deposited Cu. We found that submonolayer amounts of Cu react with HOOC, whereas the rest of the Cu remains metallic and penetrates beneath the SAM surface to the SAM  Au interface. Considerable amounts of Cu (5 nm or more) will penetrate beneath the SAM layer, which is ca. 2.5 nm thick, despite the submonolayer presence of Cu at the SAM surface. The penetration rate depends strongly on the Cu deposition rate. Depositing copper onto MHA at 220 K or less, or using faster Cu deposition rates, results in slower or even completely suppressed penetration of the Cu through the SAM layer, whereas exposure to X-rays greatly enhances the penetration rate of large amounts of Cu through the SAM layer. The reacted copper is, based on the XPS 2p and LMM peaks, in the +2 oxidation state, but cannot be identified with a simple, stoichiometric oxide such as Cu₂O, CuO, or Cu (OH)₂.     

Electrostatic energy of aromatic ion radical crystals

The electrostatic energy of aromatic charge-transfer (CT) and free radical (FR) crystals is obtained by using the many-electron site representation and the modified Hubbard model previously developed to correlate the unusual magnetic, electric and optical properties of CT and FR crystals. Both π-electron overlap between adjacent ion radicals in a stack and configuration interaction with CT states are included, thus improving on the Madelung approximation of disjoint charge distributions. π-electron overlap leads to a Coulomb exchange energy E _ex which stabilizes both ionic CT and FR crystals, while configuration interaction scales the ground state charge densities, and thus the Madelung energy, in CT crystals. E _ex is obtained for 1 : 1 CT crystals and a numerical estimate of 10–15 kcal/mole is found for both TMPD-TCNQ and for TMPD-chloranil.     

Resonance Raman Scattering with Tunable Lasers

Abstract

Raman scattering has had a long and very fruitful development since the announcements in 1928 by Sir C. V. Raman [1] of theobservation of this inelastic light scattering in several liquids and by L. Mandelstam 121 of similar scattering in crystalline quartz. Most of the early work was performed with high intensity mercury lamps using especially the lines at 4358, 4046, and 2536 Å. The development of the continuous wave helium-neon laser in 1962 and the more power- ful argon-ion laser shortly thereafter quickly led to a renewed vigor in the field. With Porto's work in 1964 using the He[sbnd]Ne laser [3] and his contributions toward refinements of the double spectrometer [4], many workers began renewed studies of a great variety of materials - solids, liquids, and gases. These studies have extended the classification of the frequencies and symmetries of the normal modes of vibrations in molecules and crystals and of rotational and vibrational lines in molecular gases.     

Cobalt iron-oxide nanoparticle modified poly(methyl methacrylate) nanodielectrics

In this paper, we report the dielectric properties of composite systems (nanodielectrics) made of small amounts of mono dispersed magnetic nanoparticles embedded in a polymer matrix. It is observed from the transmission electron microscope images that the matrix polymeric material is confined in approximately 100 nm size cages between particle clusters. The particle clusters are composed of separated spherical particles which comprise unconnected networks in the matrix. The dielectric relaxation and breakdown characteristics of the matrix polymeric material are altered with the addition of nanometer size cobalt iron-oxide particles. The dielectric breakdown measurements performed at 77 K showed that these nanodielectrics are potentially useful as an electrical insulation material for cryogenic high voltage applications. Finally, structural and dielectric properties of nanocomposite dielectrics are discussed to present plausible reasons for the observed low effective dielectric permittivity values in the present and similar nanodielectric systems. It is concluded that polymeric nanoparticle composites would have low dielectric permittivity regardless of the permittivity of nanoparticles are when the particles are coordinated with a low dielectric permittivity surfactant.     

Numerical stability analysis for the explicit high-order finite difference analysis of rotationally symmetric shells

A numerical stability analysis has been formulated to accompany the already developed explicit high-order finite difference analysis of rotationally symmetric shells subjected to time-dependent impulsive loadings. This already developed analysis utilizes a constant nodal point spacing for the spatial finite difference mesh, with the governing field differential equations formulated in terms of the transverse, meridional, and circumferential displacements as the fundamental variables. The remaining quantities which enter into the natural boundary conditions at each edge of the shell are incorporated into the complete system of equations by defining those quantities at each boundary in terms of the displacements. Surface loadings and inertia forces in each of the three displacement directions of the shell have been considered in the governing equations. Ordinary finite difference representations are used for the time derivatives. All loadings and dependent variables in the circumferential direction of the shell are expressed in Fourier series expansions. The complete system of equations is solved implicitly for the first time increment, while explicit relations are used to determine the three primary displacements within the boundary edges of the shell for the second and succeeding time increments. Separate implicit solutions at each boundary are then used to determine the remaining unspecified primary variables on and outside the boundaries. Subsequently, the remaining primary variables within the boundary edges of the shell and all secondary variables are determined explicitly. Numerical stability (or instability) of numerical solutions for given choices of spatial and time increments is determined by evaluation of the eigenvalues of the explicit coefficient matrix and comparing the maximum eigenvalue with the requirements of a stability criterion developed before by the author. Solutions for typical shells and loadings together with results of stability analyses have been included, and comparisons of the stability requirements and solutions with the requirements and solutions based upon ordinary spatial finite difference representations are included.