Study of 169Hf at high rotational frequency

High-spin properties of the nucleus ¹⁶⁹Hf have been studied through the fusion evaporation reaction ⁹⁶Zr(⁷⁶Ge,3n)¹⁶⁹Hf at a beam energy of 310 MeV. The known rotational bands have been extended considerably and 6 new bands have been established, four of which form coupled bands with pronounced M1 connections. Quasiparticle assignments are suggested for the new band structures, and it appears that coupling to vibrational degrees of freedom plays a role. Both coupled bands involve the excitation of quasiprotons. In the region of highest spin, a large alignment gain is interpreted in terms of a mixed crossing where an h _9/2 and an h _11/2 quasiproton provide the two signatures of the aligning configuration. Received: 23 March 2001 / Accepted: 20 September 2001     

Interaction of methoxy- and methylenedioxyamphetamines with carbon and polymeric adsorbents in polar liquids

Solid phase extraction (SPE) of methoxy- and methylenedioxyamphetamines from diluted aqueous solutions was investigated on carbon and polymeric adsorbents of different textures and chemical compositions. Those adsorbents were applied cartridges packed with three chemically modified carbons prepared from plum stones (initial A2PS, oxidized A2PS-O, and reduced A2PS-H) and commercially available adsorbents (polymeric LiChrolut EN, graphitized Hypercarb and Carboprep). Several factors influence the recovery rates of amphetamine derivatives such as the polarity of adsorbates (free energy of salvation), the specific surface area and surface composition of adsorbents, and the solvent characteristics. Different combinations of these factors affect the recovery rate (R1) for high- and low-surface area adsorbents. The minimal R1 values are observed for an amphetamine derivative at a maximal solvation effect and for a set of amphetamines adsorbed on graphitized carbons.      

Cyclic voltammetry of nitrophenyl N‐glycosides on mercury electrode

Ten nitrophenyl N‐glycosides have been studied electrochemically in neutral (at pH 7) water–organic solutions by cyclic voltammetry using static mercury drop electrode. For all compounds under investigation the two electrochemical processes have been observed: the four‐electron irreversible reduction of their nitro groups to the corresponding phenylhydroxylamine derivatives, as well as the two‐electron quasi‐reversible process between phenylhydroxylamine and nitroso derivatives. For three compounds the additional electrochemical processes have been also observed, which can be connected with the formation of azoxybenzene derivatives. The potentials of both redox processes: a two‐electron quasi‐reversible R? NHOH/R? NO (E_f) and four‐electron irreversible R? NO₂/R? NHOH (E_pc(I)) systems have been determined and discussed according to crystal structures of selected compounds. E_f and E_pc(I) depended strongly on the positive mesomeric effect (caused by glycosidic nitrogen atom), as well as on the intramolecular hydrogen bond between electroactive nitro group and the hydrogen atom at the glycosidic atom observed in N‐o‐nitrophenyl‐2,3,4,6‐tetra‐O‐acetyl‐β‐D ‐glucopyranosylamine. Moreover, the chirality of selected reactants has had the pronounced effect on the E_pc(I). Copyright © 2011 John Wiley & Sons, Ltd.     

Enantioselective hydrogenation of indoles derivatives catalyzed by Walphos/rhodium complexes

The enantioselective hydrogenation of indole esters has been carried out efficiently in the presence of a rhodium catalyst modified by Walphos-type chiral ligands. The addition of a base can be beneficial in some catalytic conditions.     

PEG‐dialdehyde–the new cross‐linking agent for collagen/elastin hydrogels

Collagen and elastin are the major proteins of an extracellular matrix. They possess attractive, complementary mechanical properties in their native state, but during isolation, its unique structure is destroyed, which affects the parameters of the materials. However, they still have excellent biological properties. The cross‐linking process improves the physicochemical properties of protein materials. The ideal cross‐linking agent should be effective and does not impair the biological properties of the material. Therefore, poly(ethylene) glycol‐dialdehyde was used in the study. The results show that the addition of poly(ethylene) glycol‐dialdehyde in combination with the neutralization of a collagen/elastin solution is a useful method for preparation of protein hydrogels. The gels are transparent and relatively stiff. They exhibit good mechanical properties, surface properties and are attractive for 3 T3 cells. Copyright © 2016 John Wiley & Sons, Ltd.     

Photophysical properties and photocytotoxicity of novel phthalocyanines - potentially useful for their application in photodynamic therapy

Two novel zinc(II) phthalocyanines bearing non-peripheral ester-alkyloxy substituents (Pc-4 and Pc-5) were synthesized, by a two-step procedure starting from 2,3-dicyanohydroquinone. Both sensitizers show promising photophysical properties, including solvatochromic study, qualitative evaluation of emission, aggregation behavior and singlet oxygen generation. It was proven that the photodynamic activity of the compounds studied depends on the molecular oxygen level. Comparison of the quantum yields of singlet oxygen generation as well as the oxidation rate constants using 1,3-diphenylisobenzofurane before and after deaeration proved the photodynamic effect of Pc-4 and Pc-5 to be governed by the photosensitization mechanism II. Changes in the quantities of the compounds exposed to irradiation were also estimated. Upon their exposure to light the changes in intensity of the Q band were monitored. The photodecomposition of Pc-4 and Pc-5 in DMSO or DMF solutions was found to proceed according to the first order kinetic reaction in two stages.The photosensitizing effect of Pc-4 in HSC-3 cells was significantly lower than that of ZnPc. Pc-4 was ineffective at 0.1 μM, while a low, approx. 15% photocytotoxicity was observed at 5 μM, at a distance of 5 and 10 cm. The efficacy of Pc-4 in photokilling of cultured cells is affected by hydrophobicity and the aggregation status of the photosensitizer.     

Ring-expanded bicyclic β-lactams: a structure-chiroptical properties relationship investigation by experiment and calculations

In the present work, the validity of the helicity rule relating the absolute configuration of the bridgehead carbon atom in bicyclic β-lactams to the sign of the 220 nm band observed in their electronic circular dichroism (ECD) spectra is examined for ring-expanded cephalosporin analogues. To this end, a series of model compounds with a seven-membered ring condensed with the β-lactam unit was synthesized. A key step of their synthesis was either the ring-closing metathesis (RCM) or the free radical cyclization leading to the seven-membered ring with an S, O, or C atom at the 6 position in the bicyclic skeleton. To investigate the scope and limitations of the simple, empirically established helicity rule, a combination of ECD spectroscopy, variable-temperature ECD measurements, X-ray analysis, and time-dependent density functional theory (TD-DFT) calculations was used. A comparison of the experimental ECD spectra with the spectra simulated by TD-DFT calculations gives a reasonable interpretation of the Cotton effects observed in the 240-215 nm spectral range. The results suggest that the helicity rule does not apply to the investigated compounds because of the planarity of their amide chromophore. Thus, these compounds do not constitute an exception to the rule that was established for bi- and polycyclic β-lactams with the nonplanar amide chromophore only.     

Kinetic studies on fluvastatin photodegradation in solutions

Summary The effect of solvent on the photodegradation kinetics of fluvastatin was evaluated. The degradation rate of fluvastatin was estimated on the basis of the quantum yields and kinetic parameters determination. The photodegradation appeared to follow first-order kinetics. In order to establish the light intensity absorbed by a system, Reinecke’s salt was used as a chemical actinometer.