On perturbations of solutions of the Einstein-Maxwell equations

By using the expressions for the solutions of the Einstein-Maxwell equations in terms of potentials, valid in the case where the spacetime admits a shear-free geodesic null congruence and the electromagnetic field is aligned to it, we show that a pair of complex potentials generates simultaneous perturbations of the gravitational and the electromagnetic fields. We also show that if the background electromagnetic field is null, then the pair of complex potentials is determined by a pair of coupled, linear, second-order differential equations.     

3‐[(E)‐(3‐tert‐Butyl‐1‐phenyl‐1H‐pyrazol‐5‐yl)iminomethyl]quinolin‐2(1H)‐one: chains built by π‐stacking of hydrogen‐bonded R22(8) dimers

In the title compound, C₂₃H₂₂N₄O, there is evidence for some bond fixation in the aryl component of the quinolinone unit. Pairs of molecules related by inversion are linked into R₂²(8) dimers by almost linear N—H...O hydrogen bonds, and dimers related by inversion are linked into chains by a single aromatic π–π stacking interaction.     

Microseparation techniques for the study of the enantioselectivity of drug–plasma protein binding

Stereoselectivity in protein binding can have a significant effect on the pharmacokinetic and pharmacodynamic properties of chiral drugs. The investigation of enantioselectivity of drugs in their binding with human plasma proteins and the identification of the molecular mechanisms involved in the stereodiscrimination by the proteins represent a great challenge for clinical pharmacology. In this review, the separation techniques used for enantioselective protein binding experiments are described and compared. An overview of studies on enantiomer–protein interactions, enantiomer–enantiomer interactions as well as chiral drug–drug interactions, including allosteric effects, is presented. The contribution of individual plasma proteins to the overall enantioselective binding and the animal species variability in drug–plasma protein binding stereoselectivity are reviewed. Copyright © 2008 John Wiley & Sons, Ltd.     

A ruthenium(II)-trithiacyclononane curcuminate complex: Synthesis,characterization, DNA-interaction,and cytotoxic activity

The coordination of ruthenium(II) complexes to anionic oxygen-based donors are very rare. This study describes a simple, one-pot method for obtaining [ruthenium(II)(trithiacyclononane)(curcumin)(S-DMSO)]Cl (1) in 37% yield. The structural characterization of complex 1 by elemental analysis, FT-IR, 1-D and 2-D NMR, ESI⁺-MS as well as UV–vis and fluorescence spectroscopies are presented. The DNA-melting temperature (T_m) assay shows that salmon sperm DNA (smDNA) in the presence of complex 1 has a higher melting temperature, with ΔT_m = 7.4 °C, while in the presence of curcumin the melting temperature remains unaltered. The in vitro cytotoxic activities of curcumin and complex 1 were investigated using the tumor human prostate cell line, PC-3, and the healthy cell line, PNT-2. Complex 1 is innocuous toward normal prostate epithelial cells and, whereas curcumin is toxic, with inhibition rates of ca. 35 and 65% at 50 and 80 μM, respectively. On the tumor cell line PC-3, complex 1 did not cause viability changes, whereas curcumin exhibited dose-dependent inhibition, with ca. 73% inhibition at the highest concentration tested, i.e. 80 μM. This study suggests that coordination with the trithiacyclononane ruthenium(II) scaffold stabilizes the photochemical properties of curcumin and strongly changes its biologic activity.     

Influence of the synthetic conditions on the structural diversity of extended manganese-oxalato-1,2-bis(4-pyridyl)ethylene systems

We report herein the synthesis and physicochemical characterization of eight new manganese-oxalato compounds with 1,2-bis(4-pyridyl)ethylene (bpe): {(Hbpe)(2)[Mn(2)(μ-ox)(3)]·～0.8(C(2)H(5)OH)·～0.4(H(2)O)}(n) (1), {[Mn(μ-ox)(μ-bpe)]·xH(2)O}(n) (2), [Mn(2)(μ-ox)(2)(μ-bpe)(bpe)(2)](n) (3), [Mn(μ-ox)(μ-bpe)](n) (4a and 4b), and {[Mn(4)(μ-ox)(3)(μ-bpe)(4)(H(2)O)(4)]·(X)(2)·mY}(n) with X = NO(3)(-) (5a), Br(-) (5b), and ClO(4)(-) (5c) and Y = solvation molecules. The appropriate selection of the synthetic conditions allowed us to control the crystal structure and to design extended 2D and 3D frameworks. Compound 1 is obtained at acid pH values and its crystal structure consists of stacked [Mn(2)(μ-ox)(3)](2-) layers with cationic Hbpe(+) molecules intercalated among them. Compound 2 was obtained at basic pH values with a manganese/bpe ratio of 1:1, and the resulting 3D structure consists of an interpenetrating framework in which metal-oxalato chains are bridged by bpe ligands, leading to a microporous network that hosts a variable number of water molecules (between 0 and 1) depending on the synthetic conditions. Compound 3, synthesized with a manganese/bpe ratio of 1:3, shows a 2D framework in which linear metal-oxalato chains are joined by bis-monodentate 1,2-bis(4-pyridyl)ethylene ligands. The thermal treatment of compound 3 permits the release of one of the bpe molecules, giving rise to two new 2D crystalline phases of formula [Mn(μ-ox)(μ-bpe)](n) (4a and 4b) depending on the heating rate. The open structures of 5a-5c were synthesized in a medium with a high concentration of nitrate, perchlorate, or bromide salts (potassium or sodium as cations). These anions behave as templating agents directing the crystal growing toward a cationic porous network, in which the anions placed in the voids and channels of the structure present high mobility, as inferred from the ionic exchange experiments. Variable-temperature magnetic susceptibility measurements show an overall antiferromagnetic behavior for all compounds, which are discussed in detail.     

Improvement of UV stability and mechanical properties of biopolyesters through the addition of β-carotene

β-carotene, the most abundant carotenoid in nature and a natural antioxidant, has been added at a concentration of 2 × 10⁻⁴ g per mL of polymer film forming solution to three biopolyester matrices, poly(lactic acid) (PLA), polycaprolactone (PCL) and polyhydroxybutyrate-co-valerate (PHBV). The dispersion and stability of the antioxidant within the films was studied using confocal Raman imaging spectroscopy, colorimetry and UV/visible spectrophotometry. The films were characterized in terms of thermal and mechanical properties in comparison with control films without β-carotene. Addition of β-carotene to the three biopolyesters studied resulted in significant increases in the deformation at break and lower Young modulus. This antioxidant is thought to act as a plasticizer in the biopolyesters, thus increasing their free volume and causing a change in their thermal properties. Moreover, when exposed to UV light the mechanical properties of the films with β-carotene were less affected displaying, in general, higher modulus and similar ultimate tensile strength while keeping the films more ductile than the pure films. Therefore, β-carotene can be potentially used as a natural additive to increase the UV stability of the biopolyesters.     

Application of thiophilic chromatography to deplete serum immunoglobulins in sample preparation for bidimensional electrophoresis

Serum is a typical sample for non-invasive studies in clinical research. Its proteome characterization is challenging, since requires extensive protein depletion. Methods used nowadays for removal of high-abundance proteins are expensive or show quite often a low loading capacity, which has strong repercussions on the number of samples and replicates per analysis.In order to deplete immunoglobulins (Igs) and albumin (HSA) from 1 mL serum samples, we have developed a protocol based on a combination of thiophilic chromatography, not previously used in clinical proteomics, and a HSA-specific resin. Ig/HSA-depleted samples, immunoglobulinome and albuminone were analyzed by 2-DE. Thiophilic chromatography, coupled with HSA-depletion, allows a good 2-DE resolution as well as the visualization of new spots. Moreover, it yields enough protein to evaluate technical variability and facilitate subsequent protein identification. To validate the protocol, we carried out a preliminary comparative study between triplicate Igs/HSA-depleted serum samples from healthy control individuals and recently diagnosed/untreated rheumatoid arthritis (RA) patients. RA patients showed several acute phase proteins, as well as additional serum proteins, differentially and significantly regulated.Therefore, thiophilic chromatography can be used as an efficient and economical method in 2-DE to deplete immunoglobulins from large human serum samples before a more extensive fractioning.     

Redox electrodeposition polymers: adaptation of the redox potential of polymer-bound Os complexes for bioanalytical applications

The design of polymers carrying suitable ligands for coordinating Os complexes in ligand exchange reactions against labile chloro ligands is a strategy for the synthesis of redox polymers with bound Os centers which exhibit a wide variation in their redox potential. This strategy is applied to polymers with an additional variation of the properties of the polymer backbone with respect to pH-dependent solubility, monomer composition, hydrophilicity etc. A library of Os-complex-modified electrodeposition polymers was synthesized and initially tested with respect to their electron-transfer ability in combination with enzymes such as glucose oxidase, cellobiose dehydrogenase, and PQQ-dependent glucose dehydrogenase entrapped during the pH-induced deposition process. The different polymer-bound Os complexes in a library containing 50 different redox polymers allowed the statistical evaluation of the impact of an individual ligand to the overall redox potential of an Os complex. Using a simple linear regression algorithm prediction of the redox potential of Os complexes becomes feasible. Thus, a redox polymer can now be designed to optimally interact in electron-transfer reactions with a selected enzyme.     

Development of a method based on on-line reversed phase liquid chromatography and gas chromatography coupled by means of an adsorption–desorption interface for the analysis of selected chiral volatile compounds in methyl jasmonate treated strawberries

A method based on the use of the through oven transfer adsorption–desorption (TOTAD) interface in on-line coupling between reversed phase liquid chromatography and gas chromatography (RPLC–GC) for the determination of chiral volatile compounds was developed. In particular, the method was applied to the study of the influence of methyl jasmonate (MJ) treatment on the production and enantiomeric composition of selected aroma compounds in strawberry. The compounds studied were ethyl 2-methylbutanoate, linalool and 4-hydroxy-2,5-dimethyl-3(2H)-furanone (i.e. furaneol), which were examined on days 3, 6 and 9 after treatment. The method developed resulted in relative standard deviations (RSDs) of 21.6%, 8.1% and 9.8% and limits of detection (LD) of 0.04, 0.07 and 0.02 mg/l for ethyl 2-methylbutanoate, linalool and furaneol, respectively. The application of the RPLC–TOTAD–GC method allowed higher levels of ethyl 2-methylbutanoate, linalool and furaneol to be detected, particularly after 9 days of treatment. Besides, MJ demonstrated to affect the enantiomeric distribution of ethyl 2-methylbutanoate. On the contrary, the enantiomeric composition of linalool and furaneol kept constant in both control and MJ-treated strawberries throughout the study. These results are discussed.