Examination of Template Structural Effects on CEC Chiral Separation Performance of Molecule Imprinted Polymers Made by a Generalized Preparation Protocol

Some acidic chiral templates were used to prepare open tubular (OT) molecule imprinted polymer (MIP) capillary columns to explore the effects of molecular structures of templates on chiral recognition capabilities and to verify the feasibility of the general MIP preparation protocol introduced in the previous study. The templates are phenyl carboxylic acids and their derivatives. Optimization was carried out for chiral separation of template enantiomers for each MIP column through varying pH and composition of eluent. It was found that the preparation protocol can be successfully applied for the appropriate templates with functional groups fulfilling the three-points interaction rule. The chiral separation performances were quite satisfactory for MIPs of such templates although they are yet inferior to the separation performances of the MIP columns fabricated with the templates of profen drugs (2-arylpropionic acids with a large substituent on the phenyl ring). Subtle variations of the template molecular structures have been found to be critical to enhance chiral recognition ability of the resultant MIP column.     

An Identification Problem for First-Order Degenerate Differential Equations

We study a first-order identification problem in a Banach space. We discuss the nondegenerate and mainly the degenerate case. As a first step, suitable hypotheses on the involved closed linear operators are made in order to obtain unique solvability after reduction to a nondegenerate case; the general case is then handled with the help of new results on convolutions. Some applications to partial differential equations motivate this abstract approach.Communicated by I. GalliganiWork partially supported by MIUR (Ministero dell’ Istruzione, dell’ Università e dalla Ricerca), Project PRIN 2004011204 “Analisi Matematica nei Problemi Inversi,” and by the University of Bologna Funds for Selected Research Topics.     

Cetyl‐alcohol‐reinforced hollow fiber solid/liquid‐phase microextraction and HPLC–DAD analysis of ezetimibe and simvastatin in human plasma and urine

A new cetyl‐alcohol‐reinforced hollow fiber solid/liquid‐phase microextraction (CA–HF–SLPME) followed by high‐performance liquid chromatography–diode array detection (HPLC–DAD) method was developed for simultaneous determination of ezetimibe and simvastatin in human plasma and urine samples. To prepare the CA–HF–SLPME device, the cetyl‐alcohol was immobilized into the pores of a 2.5 cm hollow fiber micro‐tube and the lumen of the micro‐tube was filled with 1‐octanol with the two ends sealed. Afterwards, the prepared device was introduced into 10 mL of the sample solution containing the analytes with agitation. Under optimized conditions, calibration curves plotted in spiked plasma and urine samples were linear in the ranges of 0.363–25/0.49–25 μg L^?1 for ezetimibe/simvastatin and 0.193–25/0.312–25 μg L^?1 for ezetimibe/simvastatin in plasma and urine samples, respectively. The limit of detection was 0.109/0.174 μg L^?1 for ezetimibe/simvastatin in plasma and 0.058/0.093 μg L^?1 for ezetimibe/simvastatin in urine. As a potential application, the proposed method was applied to determine the concentration of selected analytes in patient plasma and urine samples after medication and satisfactory results were achieved. In comparison with reference methods, the CA–HF–SLPME–HPLC–DAD method demonstrates considerable potential in the biopharmaceutical analysis of selected drugs.     

Solvent interactions with [Val(5)]angiotensin II in ethanol-water

Intermolecular NOE experiments have been used to explore the interactions of water and ethanol molecules in 35% ethanol/65% water (v/v) with the octapeptide hormone [val (5)]angiotensin II at temperatures from 0 to 25 degrees C. Magnetic dipole-dipole cross relaxation terms sigma(HH)(NOE) and sigma(HH)(ROE) for interaction of both solvent components suggest that ethanol molecules interact with the peptide backbone atoms strongly enough to associate for times comparable to the rotational correlation time of the peptide; comparison of observed ROE and NOE cross relaxation terms indicate that lifetimes of these interactions are of the order 0.4 ns at 5 degrees C. Formation of such peptide-ethanol complexes can also account for larger-than-expected values of the cross relaxation terms at higher temperatures. Alternative explanations of the observations reported are shown to be unlikely, primarily because they require unreasonable and highly localized concentrations of the ethanol near the peptide. Side chains of the peptide appear to experience no unusual interactions with ethanol. Cross relaxation terms for water-peptide backbone interactions indicate long-lived interactions of water with the backbone atoms although the nonpolar side chains of the peptide (Val3, Val5, Pro7, and possibly Phe8) do not interact in any specific way with water molecules. Cross relaxation terms for protons of the polar (Tyr4 and His6) side chains may reflect strong interactions with water, but analysis of these is confounded by solvent proton exchange and possible spin diffusion effects.     

Interactions of trifluoroethanol with [val5]angiotensin II

Intermolecular 1H{19F} NOE experiments have been used to explore the interactions of trifluoroethanol (TFE) with the octapeptide hormone [val5]angiotensin II at temperatures from 5 to 25 degrees C. Circular dichroism spectra indicate that 40% trifluoroethanol has an influence on the conformations of the peptide, probably leading to beta-structures. Diffusion experiments show that the mean hydrodynamic radius of the peptide in 40% trifluoroethanol-water is about 8 A, consistent with significant folding of the peptide in this medium. Distance constraints derived from intramolecular NOESY data along with observed vicinal coupling constants (3JCalphaHNH) were used to develop conformations consistent with available data. Assuming that intermolecular 1H{19F} NOEs are the result of diffusive encounters of TFE and peptide molecules, it is shown that no single conformation is consistent with the experimental values of the sigmaHF cross-relaxation parameters. It is argued that the disagreements between observed and expected values of sigmaHF are the result of formation of long-lived (approximately 0.5 ns) fluoroalcohol-peptide complexes, a conclusion consonant with similar studies of other peptide-fluoroalcohol systems. Complex formation appears to be especially prevalent near the charged amino acid side chains of the hormone.     

Chitosan loaded with silver nanoparticles,CS‐AgNPs,using thymus syriacus,wild mint,and rosemary essential oil extracts as reducing and capping agents

The present study describes the green method for the preparation of chitosan loaded with silver nanoparticles (CS‐AgNPs) in the presence of 3 different extracted essential oils. The essential oils play dual roles as reductant and capping agents. The reducing power and DPPH (2,2‐diphenyl‐1‐picrylhydrazyl) assay for the 3 essential oils—Thymus syriacus (T), wild mint (M), and rosemary (R)—have been reported. The preparation of CS‐AgNPs was performed by 2 steps. The 3 previously extracted essential oils have been used as reducing and capping agent in the first step, while in the second step, silver nanoparticles were integrated in chitosan. The integration of AgNPs in the structure of chitosan was confirmed by ultraviolet‐visible, Fourier transform infrared spectroscopy, scanning electron microscopy techniques, and energy dispersive X‐ray. Surface plasmon resonance confirmed the formation of CS‐AgNPs with maximum absorbance at λ_max between 405 ‐ 410 and 410 ‐ 430 nm for colloidal and films of CS‐AgNPs, respectively. The intensity of bands at 3408 cm^?1 in the fourier transform infrared spectroscopy measurements was decreased substantially and shifted slightly to lower frequency (?υ = 43 cm^?1). Scanning electron microscopy shows a spherical morphology of AgNPs with size of 62 nm for both colloidal and film samples, and energy dispersive X‐ray analysis shows peaks confirming AgNPs formation.     

Enantioselective determination of modafinil in pharmaceutical formulations by capillary electrophoresis, and computational calculation of their inclusion complexes

A fast capillary electrophoretic method is described for the separation and determination of the enantiomers of the novel wake-promoting agent, modafinil. Several parameters affecting the separation were studied, including the type and concentration of chiral selector, buffer pH, buffer concentration, voltage and temperature. Good chiral separation of the racemic mixture was achieved in less than 5 min with resolution factor Rs?=?2.51, using a bare fused-silica capillary and a background electrolyte (BGE) of 25 mM H₃PO₄?1 M tris solution; pH 8.0; containing 30 mg mL^?1 of sulfated-β-cyclodextrin (S-β-CD). The separation was carried out in normal polarity mode at 25 ^?C, 18 kV and using hydrostatic injection. Acceptable validation criteria for selectivity, linearity, precision, and accuracy were included. The developed method was successfully applied to the assay of enantiomers of modafinil in pharmaceutical formulations. The computational calculations for the enantiomeric inclusion complexes rationalized the reasons for the different migration times between the modafinil enantiomers.