Ultrafast dynamics of metal complexes of tetrasulphonated phthalocyanines

A promising material in medicine, electronics, optoelectronics, electrochemistry, catalysis, and photophysics, tetrasulphonated aluminum phthalocyanine (AlPcS(4)), is investigated by means of steady-state and time-resolved pump-probe spectroscopies. Absorption and steady-state fluorescence spectroscopy indicate that AlPcS(4) is essentially monomeric. Spectrally resolved pump-probe data are recorded on time scales ranging from femtoseconds to nanoseconds. The nature of these fast processes and pathways of the competing relaxation processes from the initially excited electronic states in aqueous and organic (dimethyl sulfoxide) solutions are discussed. The decays and bleaching recovery have been fitted in the ultrafast window (0-10 ps) and later time window extending to nanoseconds (0-1 ns). While the excited-state dynamics have been found to be sensitive to the solvent environment, we were able to show that the fast dynamics is described by three time constants in the ranges of 115-500 fs, 2-25 ps, and 150-500 ps. We were able to ascribe these three time constants to different processes. The shortest time constants have been assigned to vibrational wavepacket dynamics. The few picosecond components have been assigned to vibrational relaxation in the excited electronic states. Finally, the 150-500 ps components represent the decay from S(1) to the ground state. The experimental and theoretical treatment proposed in this paper provides a basis for a substantial revision of the commonly accepted interpretation of the Soret transition (B transition) that exists in the literature.     

DNA interstrand crosslinks are induced in cells prelabelled with 5-bromo-2'-deoxyuridine and exposed to UVC radiation

It has been observed previously that 5-bromo-2'-deoxyuridine (BrdU) potentiates the effect of UVC radiation on the level of sister chromatid exchanges. It is not known which type of DNA damage is responsible for this enhancing effect and we have proposed this to be the DNA interstrand crosslink (ICL) which, theoretically, may arise in cells that are labelled with BrdU for one round of replication and exposed to UVC radiation. The aim of the present investigation was to verify if ICLs are indeed formed during this irradiation scenario. CHO-K1 cells were prelabelled with BrdU and exposed to UVC. ICLs were detected by a modified version of the comet assay that relies on the reduction of induced DNA migration in the agarose gel. Carboplatin was used as a positive control. We found that BrdU+UVC treatment indeed results in a reduction of the damage induced by gamma-radiation. Furthermore, we observed that CL-V4B cells exposed to BrdU+UVC, but not to UVC alone, showed a very high level of chromosomal damage. These cells have a deficient Rad51C paralog that renders them extremely sensitive towards ICLs. Interestingly, the cytogenetic results did not correlate with cell survival, where it was found that the CL-V4B cells tolerate BrdU+UVC better than the wild type cells. The possible reasons are discussed. Taken together our results indicate that ICLs are formed in DNA that was prelabelled with BrdU and exposed to UVC radiation.     

Comparative molecular surface analysis (CoMSA) for virtual combinatorial library screening of styrylquinoline HIV-1 blocking agents

We used comparative molecular surface analysis to design molecules for the synthesis as part of the search for new HIV-1 integrase inhibitors. We analyzed the virtual combinatorial library (VCL) constituted from various moieties of styrylquinoline and styrylquinazoline inhibitors. Since imines can be applied in a strategy of dynamic combinatorial chemistry (DCC), we also tested similar compounds in which the -C=N- or -N=C- linker connected the heteroaromatic and aromatic moieties. We then used principal component analysis (PCA) or self-organizing maps (SOM), namely, the Kohonen neural networks to obtain a clustering plot analyzing the diversity of the VCL formed. Previously synthesized compounds of known activity, used as molecular probes, were projected onto this plot, which provided a set of promising virtual drugs. Moreover, we further modified the above mentioned VCL to include the single bond linker -C-N- or -N-C-. This allowed increasing compound stability but expanded also the diversity between the available molecular probes and virtual targets. The application of the CoMSA with SOM indicated important differences between such compounds and active molecular probes. We synthesized such compounds to verify the computational predictions.     

Optical force field mapping in microdevices

We present a method for characterizing microscopic optical force fields. Two dimensional vector force maps are generated by measuring the optical force applied to a probe particle for a grid of particle positions. The method is used to map out the force field created by the beam from a lensed fiber inside a liquid filled microdevice. We find transverse gradient forces and axial scattering forces on the order of 2 pN per 10 mW laser power which are constant over a considerable axial range (>35 microm). These findings suggest future useful applications of lensed fibers for particle guiding/sorting. The propulsion of a small particle at a constant velocity of 200 microm s(-1) is shown.     

About 1‐triphenylmethyl‐3‐tert‐butylaziridinone and some of its reactions

A high‐yield synthesis of 1‐triphenylmethyl‐3‐tert‐butylaziridinone ( 4 ), its physical and spectral properties, the limits of its thermal stability, and reactions with methanol, benzylamine and sodium methoxide in methanol are described.     

Characteristics of the oxidation process in the oleic acid-propionic acid system by means of dielectric constant measurements

The influence of the hydrogen-bond association on the course of autoxidation of oleic acid in the binary system oleic acid-propionic acid was discussed. The association was characterized with the help of dielectric constant measurements.     

t‐Butyl Hydroperoxide Oxidative Dealkylation of Hydroquinone Ethers to 1,4‐Quinones

Various organoselenium compounds (diselenides, benzisoselenazol‐3(2H)‐ones, and 1,3,2‐thiaselenazolones) are effective catalysts for oxidative dealkylation of hydroquinone ethers with t‐butyl hydroperoxide to 1,4‐quinones. The reactions is most efficient when t‐butyl hydroperoxide in the presence of poly(bis‐1,2‐phenyl) diselenide is used as an oxidizing agent. In this way 1,4‐benzo and 1,4‐naphthoquinones are produced in good to high yields.     

The partial system Pb3(PO4)2−P2O5−PbCl2

The present research proved that no stable compounds are formed in the partial ternary system Pb₃(PO₄)₂?P₂O₅?PbCl₂ of the ternary system PbO?P₂O₅?PbCl₂. Reactions which may proceed in this partial system were considered theoretically. Examinations were performed by thermal, X-ray and chemical analyses.