Two-Photon Solvatochromism II: Experimental and Theoretical Study of Solvent Effects on the Two-Photon Absorption Spectrum of Reichardt’s Dye

In this study, we report on the influence of solvent on the two-photon absorption (2PA) spectra of Reichardt’s dye (RD). The measurement of 2PA cross-sections is performed for three solvents (chloroform, dimethyl formamide, and dimethyl sulfoxide) using the Z-scan technique. The key finding of this study is the observation that the cross-section, corresponding to the 2PA of the intramolecular charge-transfer state, diminishes substantially upon increasing the solvent polarity. To unravel the solvent dependence of the 2PA cross-section, the electronic structure of RD is determined using a hybrid quantum mechanics/molecular mechanics (QM/MM) approach, in which polarization between the solute and solvent is taken into account by using a self-consistent scheme in the solvent polarization. The two-state approximation proves to be adequate for the studied system, and allowed the observed solvent-polarity-induced decrease of the 2PA cross-section to be related to the decrease of the transition moment and the increase in the excitation energy.     

Simultaneous quantitation of venlafaxine and its main metabolite,O‐desmethylvenlafaxine,in human saliva by HPLC

Venlafaxine is used for the treatment of major depression and generalized anxiety disorders. Because its active metabolite, O‐desmethylvenlafaxine, has also a similar activity, the purpose of this work was to develop a simple method for simultaneous quantitation of both drugs using HPLC with UV detection. The saliva was chosen as diagnostic material because of its easy accessibility and possibility of sampling by patients, for example, at home. The sample pretreatment by liquid–liquid extraction allows to separate both compounds from this diagnostic material with a high recovery, varying between 92.65 and 104.78%. The major advantage of the validated method lies in its sensitivity, reproducibility, and specificity for routine quantitation of the venlafaxine and O‐desmethylvenlafaxine in the human saliva. The low detection and quantification values (2.8–3.1 and 9.4–10.2 ng/mL, respectively) enable to quantify both species excreted with saliva at the nanogram level. The applicability of the method was verified by analysis of the saliva obtained from depressed women treated with venlafaxine. The results suggest that the method could be used for therapeutic drug monitoring in patients undergoing treatment with venlafaxine, especially when metabolic anomalies or low compliance are suspected, or in the case of polypharmacy.     

Drop‐coating deposition Raman spectroscopy of porphyrins

We report an improvement of the Raman detection sensitivity of porphyrins by factor of 10⁵ using drop‐coating deposition Raman spectroscopy (DCDR). We were able to obtain Raman spectra from ~20 nM initial (deposited) concentrations of cationic and anionic porphyrin. This detection limit is comparable with or even better than that of surface‐enhanced Raman scattering spectroscopy using Ag nanoparticles. Moreover, DCDR spectrum of protoporphyrin IX, which is known as a marker in clinical diagnostics of cancer, was also obtained from 10 nM deposited concentration. To our knowledge, it is the first demonstration of the resonance DCDR spectroscopy. Copyright © 2015 John Wiley & Sons, Ltd.     

Azines and Azoloazines,Part 1: Reactions of Triazolo[3,4‐a]phthalazine and Its Derivatives with Carbanions

Triazolo[3,4‐a]phthalazine as well as their chloro and nitro derivatives were subjected to the reactions with the carbanions typical for the vicarious nucleophilic substitution (VNS) of hydrogen. The reactions were strongly dependent on the substituents present on the triazolo[3,4‐a]phthalazine ring and resulted not only in the substitution of hydrogen but also in exchange of chlorine atom and pyridazine ring scission; the latter process dominated for the unsubstituted triazolophthalazine. Two of the products showed promising stimulating activity towards the central nervous system with no significant toxic effects.     

Physical and Bioengineering Properties of Polyvinyl Alcohol Lens-Shaped Particles Versus Spherical Polyelectrolyte Complex Microcapsules as Immobilisation Matrices for a Whole-Cell Baeyer–Villiger Monooxygenase

Direct comparison of key physical and chemical-engineering properties of two representative matrices for multipurpose immobilisations was performed for the first time. Polyvinyl alcohol lens-shaped particles LentiKats® and polyelectrolyte complex microcapsules were characterised by advanced techniques with respect to the size distribution of the particles, their inner morphology as revealed by fluorescent probe staining, mechanical resistance, size-exclusion properties, determination of effective diffusion coefficient and environmental scanning electron microscope imaging. While spherical polyelectrolyte complex microcapsules composed of a rigid semipermeable membrane and a liquid core are almost uniform in shape and size (diameter of 0.82 mm; RSD?=?5.6 %), lens-shaped LentiKats® are characterised by wider size distribution (diameter of 3.65 mm; RSD?=?10.3 % and height of 0.341 mm; RSD?=?32.3 %) and showed the same porous structure throughout their whole volume at the mesoscopic (micrometre) level. Despite differences in their inner structure and surface properties, the pore diameter of?～?2.75 nm for regular polyelectrolyte complex microcapsules and?～?1.89 nm for LentiKats® were similar. These results were used for mathematical modelling, which provided the estimates of the effective diffusion coefficient of sucrose. This value was 1.67?×?10^?10 m² s^?1 for polyelectrolyte complex microcapsules and 0.36?×?10^?10 m² s^?1 for LentiKats®. Recombinant cells Escherichia coli-overexpressing enzyme cyclopentanone monooxygenase were immobilised in polyelectrolyte complex microcapsules and LentiKats® for comparison of their operational stability using model Baeyer–Villiger oxidation of (±)-cis-bicyclo [3.2.0] hept-2-en-6-one to regioisomeric lactones as important chiral synthons for potential pharmaceuticals. Both immobilisation matrices rendered high operational stability for whole-cell biocatalyst with no reduction in the biooxidation rate over 18 repeated reaction cycles.     

Adsorption of La,Eu and Lu on raw and modified red clay

Adsorption of La, Eu, and Lu on red clay was studied in an initial concentration range of 10^?4–10^?3 mol/dm³ and a pH range of 2–10. Among the different forms of red clay: T-clay (thermally modified), R-clay (raw, unmodified), Na-clay (sodium form), H-clay (acid form), and HDTMA-clay (surfactant-modified form), T-clay was found to be the most effective adsorbent of the lanthanides studied. The adsorption/desorption isotherms, i.e. log K _d versus log c _eq dependencies, had a linear character. Among the investigated lanthanides, Eu was most strongly bound by the clay surface and, therefore, parameters a (slopes of the lines log K _d = alog c _eq + b) of Eu were the highest compared to those for La and Lu. Desorption isotherms were located above adsorption isotherms, which resulted from chemiadsorption of the investigated lanthanides. Changes in lanthanide adsorption with pH were successfully modelled based on the molar fractions of Ln³⁺, LnOH²⁺, LnCO₃ ⁺, and Ln(CO₃) ₂ ^? species in the aqueous phase [Ln—lanthanide(III)].     

Fouling of nanofiltration membranes used for separation of fermented glycerol solutions

In this study, the glycerol solutions were fermented using Lactobacillus casei bacteria. The broths were pre-treated by microfiltration, followed by a further separation with nanofiltration. The latter process was carried out in two stages, using the NF270 and NF90 membranes, respectively. The concentrates thus obtained were enriched with citric acid (first stage) and then with lactic acid and glycerol (second stage). By means of SEM and AFM microscopy, as well as ATR-FTIR analysis, the intensity of membrane-fouling was studied. The colloidal fouling and bio-fouling caused a more than two-fold decrease in the permeate flux during microfiltration of the broth. This pre-treatment stage was effective, and a permeate turbidity of less than 0.2 NTU was obtained. However, the nanofiltration membranes exhibited a 30 % flux decline over the course of the process, mainly due to the organic fouling.     

Poly(vinyl methyl ether) hydrogels at temperatures below the freezing point of water—molecular interactions and states of water

Water interacting with a polymer reveals a number of properties very different to bulk water. These interactions lead to the redistribution of hydrogen bonds in water. It results in modification of thermodynamic properties of water and the molecular dynamics of water. That kind of water is particularly well observable at temperatures below the freezing point of water, when the bulk water crystallizes. In this work, we determine the amount of water bound to the polymer and of the so-called pre-melting water in poly(vinyl methyl ether) hydrogels with the use of Raman spectroscopy, dielectric spectroscopy, and calorimetry. This analysis allows us to compare various physical properties of the bulk and the pre-melting water. We also postulate the molecular mechanism responsible for the pre-melting of part of water in poly(vinyl methyl ether) hydrogels. We suggest that above ?60 °C, the first segmental motions of the polymer chain are activated, which trigger the process of the pre-melting.     

Excitation-wavelength Dependent Fluorescence of Ethyl 5-(4-aminophenyl)-3-amino-2,4-dicyanobenzoate

The excitation wavelength dependence of the steady-state and time-resolved emission spectra of ethyl 5-(4-aminophenyl)-3-amino-2,4-dicyanobenzoate (EAADCy) in tetrahydrofuran (THF) at room temperature has been examined. It is found that the ratio of the fluorescence intensity of the long-wavelength and short-wavelength fluorescence bands strongly depends on the excitation wavelength, whereas the wavelengths of the fluorescence excitation and fluorescence bands maxima are independent on the observation/excitation wavelengths. The dynamic Stokes shift of fluorophore in locally excited (LE) and intramolecular charge transfer (ICT) states has been studied with a time resolution about 30 ps. The difference between Stokes shift in the LE and ICT states was attributed to the solvent response to the large photoinduced dipole moment of EAADCy in the fluorescent charge transfer state. On this base we can state that, the relaxation of the polar solvent molecules around the fluorophore was observed.     

The controlled separable projection property for Banach spaces

Let X, Y be two Banach spaces. We say that Y is a quasi-quotient of X if there is a continuous operator R: X → Y such that its range, R(X), is dense in Y.