Separation of phenolic acids by capillary electrophoresis with indirect contactless conductometric detection

A new method for the electrophoretic separation of nine phenolic acids (derivatives of benzoic and cinnamic acids) with contactless conductometric detection is presented. Based on theoretical calculations, in which the mobility of the electrolyte co- and counterions and mobility of analytes are taken into consideration, the electrolyte composition and detection mode was selected. This approach was found to be especially valuable for optimization of the electrolyte composition for the separation of analytes having medium mobility. Indirect conductometric detection mode was superior to the direct mode as predicted theoretically. The best performance was achieved with 150 mM 2-amino-2-methylpropanol electrolyte at pH 11.6. The separation was carried out in a counter-electroosmotic mode and completed in less than 6 min. The LODs achieved were about 2.3-3.3 microM and could be further improved to 0.12-0.17 microM by using a sample stacking procedure. The method compares well to the UV-Vis detection.     

Conformational flexibility of L-alanine zwitterion determines shapes of Raman and Raman optical activity spectral bands

Detailed analysis of Raman and Raman optical activity (ROA) of L-alanine zwitterion (ALAZW) revealed that shapes of the spectral bands are to a large extent determined by the rotation of the NH(3)(+), CO(2)(-), and CH(3) groups. Aqueous solution ALAZW spectra were measured down to 100 cm(-1) and compared to complex simulations based on ab initio (B3LYP/CPCM/6-31++G**) computations of molecular energies and spectral parameters. The bands exhibit different sensitivities to the motion of the rotating group; typically, for more susceptible bands the Raman signal becomes broader and the ROA intensity decreases. When these dynamical factors are taken into account in Boltzmann averaging of conformer contributions, simulated spectra not only better agree with the experiment, but shapes of the rotational potentials can be estimated. Effects of the molecular flexibility could be also demonstrated on differences in Raman spectra of the solution, crystalline, and glass (gellike) solid states of ALAZW. Experimental Raman and ROA spectra of four model dipeptides of different rigidities (Ala-Pro, Pro-Ala, Pro-Gly, and Gly-Pro) indicate that the broadening of spectral lines can be used as a general site-specific indicator of molecular rigidity or flexibility.     

Determination of neopterin, kynurenine, tryptophan and creatinine in human serum by high throuput HPLC

A new HPLC method for simultaneous determination of neopterin, creatinine, kynurenine and tryptophan in human serum was developed and validated. Monolithic stationary phase's technology (two monolithic columns RP-18e were connected with guard monolithic cartridge 4.6 mm × 50 mm + 3.0 mm × 100 mm and 4.6 × 10 mm) and special auto sampler for micro titration plates (samples are storage in dark cooled place protected against evaporation) were combined with easy sample preparation step. As mobile phase 15 mmol/L phosphate buffer at pH 4.50 was used. Neopterin and tryptophan were detected using fluorescent detection and kynurenine and creatinine were detected by diode-array detection. This method may be suitable for large sequences of samples in clinical research and routine practice.     

Introducing an amine group to calix[5]arene: comparison of several methods

Abstract

Chemists often use an amine group as an intermediate in syntheses of imines, amides and ureas; however, in the case of syntheses of p-aminophenol type compounds, several problems might occur. In this article, we prepared p-aminocalix[5]arene-pentaol by reduction of both nitro and azo derivatives, and compared four methods of the amine preparation, focusing mainly on its gramme scale and time-consuming issues.     

Extracellular Enzymes of the White-Rot Fungus Fomes fomentarius and Purification of 1,4-β-Glucosidase

Production of the lignocellulose-degrading enzymes endo-1,4-β-glucanase, 1,4-β-glucosidase, cellobiohydrolase, endo-1,4-β-xylanase, 1,4-β-xylosidase, Mn peroxidase, and laccase was characterized in a common wood-rotting fungus Fomes fomentarius, a species able to efficiently decompose dead wood, and compared to the production in eight other fungal species. The main aim of this study was to characterize the 1,4-β-glucosidase produced by F. fomentarius that was produced in high quantities in liquid stationary culture (25.9 U?ml^?1), at least threefold compared to other saprotrophic basidiomycetes, such as Rhodocollybia butyracea, Hypholoma fasciculare, Irpex lacteus, Fomitopsis pinicola, Pleurotus ostreatus, Piptoporus betulinus, and Gymnopus sp. (between 0.7 and 7.9 U?ml^?1). The 1,4-β-glucosidase enzyme was purified to electrophoretic homogeneity by both anion-exchange and size-exclusion chromatography. A single 1,4-β-glucosidase was found to have an apparent molecular mass of 58 kDa and a pI of 6.7. The enzyme exhibited high thermotolerance with an optimum temperature of 60 °C. Maximal activity was found in the pH range of 4.5–5.0, and K _M and V _max values were 62 μM and 15.8 μmol?min^?1?l^?1, respectively, when p-nitrophenylglucoside was used as a substrate. The enzyme was competitively inhibited by glucose with a K _i of 3.37 mM. The enzyme also acted on p-nitrophenylxyloside, p-nitrophenylcellobioside, p-nitrophenylgalactoside, and p-nitrophenylmannoside with optimal pH values of 6.0, 3.5, 5.0, and 4.0–6.0, respectively. The combination of relatively low molecular mass and low K _M value make the 1,4-β-glucosidase a promising enzyme for biotechnological applications.     

Screening of medicinal plants traditionally used in Peruvian Amazon for in vitro antioxidant and anticancer potential

Plants mentioned in this study have numerous records in traditional Peruvian medicine being used in treatment of cancer and other diseases likely to be associated with oxidative stress. Amongst the eight plant species tested, only Dysphania ambrosioides exhibited combinatory antioxidant and anti-proliferative effect on a broad spectrum of cancer cells (DPPH and ORAC values = 80.6 and 687.3 μg TE/mg extract, respectively; IC₅₀ against Caco-2, HT-29 and Hep-G2 = 129.2, 69.9 and 130.6, respectively). Alkaloids and phenolic compounds might significantly contribute to anticancer/antioxidant activity of this plant. The results justify the traditional medicinal use of this plant. Our findings further suggest that D. ambrosioides might serve as a prospective material for further development of novel plant-based antioxidant and/or anti-proliferative agents. Detailed analysis of chemical composition together with toxicology assessments and in vivo antioxidant/anti-proliferative activity of this plant should be carried out in order to verify its potential practical use.     

Enantiomeric Discrimination by Surface‐Enhanced Raman Scattering–Chiral Anisotropy of Chiral Nanostructured Gold Films

A surface‐enhanced Raman scattering‐chiral anisotropy (SERS‐ChA) effect is reported that combines chiral discrimination and surface Raman scattering enhancement on chiral nanostructured Au films (CNAFs) equipped in the normal Raman scattering Spectrometer. The CNAFs provided remarkably higher enhancement factors of Raman scattering (EFs) for particular enantiomers, and the SERS intensity was proportional to the enantiomeric excesses (ee) values. Except for molecules with mesomeric species, all of the tested enantiomers exhibited high SERS‐ChA asymmetry factors (g), ranging between 1.34 and 1.99 regardless of polarities, sizes, chromophores, concentrations and ee. The effect might be attributed to selective resonance coupling between the induced electric and magnetic dipoles associated with enantiomers and chiral plasmonic modes of CNAFs.     

Kinetics of D,L–Lactide Polymerization Initiated with Zirconium Acetylacetonate

The kinetic of D,L-lactide polymerization in presence of biocompatible zirconium acetylacetonate initiator was studied by differential scanning calorimetry in isothermal mode at various temperatures and initiator concentrations. The enthalpy of D,L-lactide polymerization measured directly in DSC cell was found to be ΔH=−17.8±1.4 kJ mol⁻¹. Kinetic curves of D,L-lactide polymerization and propagation rate constants were determined for polymerization with zirconium acetylacetonate at concentrations of 250–1000 ppm and temperature of 160–220 °C. Using model or reversible polymerization the following kinetic and thermodynamic parameters were calculated: activation energy E_a=44.51±5.35 kJ mol⁻¹, preexponential constant lnA=15.47±1.38, entropy of polymerization ΔS=−25.14 J mol⁻¹ K⁻¹. The effect of reaction conditions on the molecular weight of poly(D,L-lactide) was shown.     

A Photochemical/Thermal Switch Based on 4,4′-Bis(benzimidazolio)stilbene: Synthesis and Supramolecular Properties.

Stilbene derivatives are well-recognised substructures of molecular switches based on photochemically and/or thermally induced (E)/(Z) isomerisation. We combined a stilbene motif with two benzimidazolium arms to prepare new sorts of supramolecular building blocks and examined their binding properties towards cucurbit[n]urils (n=7, 8) and cyclodextrins (β-CD, γ-CD) in water. Based on the ¹H NMR data and molecular dynamics simulations, we found that two distinct complexes with different stoichiometry, i. e., guest@β-CD and guest@β-CD₂, coexist in equilibrium in a water solution of the (Z)-stilbene-based guests. We also demonstrated that the bis(benzimidazolio)stilbene guests can be transformed from the (E) into the (Z) form via UV irradiation and back via thermal treatment in DMSO.     

Spectroscopic detection of DNA quadruplexes by vibrational circular dichroism

The four-stranded G-quadruplex motif is a conformation frequently adopted by guanine-rich nucleic acids that plays an important role in biology, medicine, and nanotechnology. Although vibrational spectroscopy has been widely used to investigate nucleic acid structure, association of particular spectral features with the quadruplex structure has to date been ambiguous. In this work, experimental IR absorption and vibrational circular dichroism (VCD) spectra of the model quadruplex systems d(G)(8) and deoxyguanosine-5'-monophosphate (5'-dGMP) were analyzed using molecular dynamics (MD) and quantum-chemical modeling. The experimental spectra were unambiguously assigned to the quadruplex DNA arrangement, and several IR and VCD bands related to this structural motif were determined. Involvement of MD in the modeling was essential for realistic simulation of the spectra. The VCD signal was found to be more sensitive to dynamical structural variations than the IR signal. The combination of the spectroscopic techniques with multiscale simulations provides extended information about nucleic acid conformations and their dynamics.