SENSIBILISIERTE PHOTOOXYDATION DURCH METHYLENBLAU THIOPYRONIN UND PYRONIN-III. MITTEILUNG: ÜBER DEN MECHANISMUS DER PHOTOSENSIBILISIERTEN OXYDATION DES GUANOSINS DURCH THIOPYRONIN

Abstract— The thiopyronin-sensitized photooxidation of guanosine was investigated, using flash photolysis techniques. The reaction kinetics of three short-lived intermediates (the triplet state, the reduced radical, and the oxidized radical) were followed by spectroscopy. The influence of guanosine concentration on the reaction rate shows that only the oxidized radical (reaction 7) of thiopyronin is affected by guanosine. This suggests that the primary step in the photodynamic destruction of DNA is the oxidation of guanosine by the oxidized radical of thiopyronin (reaction 9). This mechanism is discussed in terms of the redox potentials of the donor and the acceptor for three different cases: (1) where the oxidation potential of the donor is more negative than that of the triplet state, the acceptor being the triplet state ( F^T ); (2) where the oxidation potential of the donor is between the potentials of the triplet state and the oxidized radical, the acceptor being the oxidized radical (F_ox); and (3) where the oxidation potential of the donor is more positive than the reduction potential of both the triplet state and the oxidized radical; in this case no electron exchange takes place. The thiopyronin-guanosine system is an example of the second case.     

EVALUATION OF SULFONATED ALUMINUM PHTHALOCYANINES FOR USE IN PHOTOCHEMOTHERAPY. A STUDY ON THE RELATIVE EFFICIENCIES OF PHOTOINACTIVATION

The cellular photosensitivity caused by aluminum phthalocyanines sulfonated to different degrees (AlPcSn) has been investigated. The phototoxic effect increased with decreasing number of sulfonate groups on the macrocycle, with the exception of AlPcS1 which was less phototoxic than AlPcS2 but more phototoxic than AlPcS3 and AlPcS4. The tendency of the AlPcSns to aggregate in our cellular system increased with increasing lipophilicity of the sensitizers. The aggregates had little or no photosensitizing activity. The low efficiency of cell inactivation caused by AlPcS1 can be explained by the highly aggregated state of this sensitizer in the cells. AlPcS2 and AlPcS3 induced a lower degree of cell inactivation per fluorescing quantum and per quantum absorbed by monomeric species than did AlPcS2 and AlPcS1. AlPcS4 and AlPcS3 are therefore suggested to be in different intracellular locations than AlPcS2 and AlPcS1.     

The Application of Suzuki Coupling Reaction on the Preparation of Carbosilane Dendrimers with 4-（Naphthalen-l-yl）phenyl Core

Carbosilane dendrimers with p-bromophenyl core were synthesized by alternating Grignard and hydrosilylation reaction. And the α-naphthalenyl was connected to the core by the Suzuki coupling reaction. A new carbosilane dendrimer with big π-conjugated structure [4-（naphthalen-l-yl）phenyl core] was given. It shows Suzuki coupling reaction is an effective and powerful core-functionalization method and the satisfactory result can be obtained through prolonging the reaction time with the increase of the generation of dendrimer.     

SENSIBILISIERTE PHOTOOXIDATION DURCH METHYLENBLAU, THIOPYRONIN UND PYRONIN-I MITTEILUNG: FLASH-PHOTOOXIDATION VON p-DIAMINOTOLUOL

The dye (F)*sensitized photooxidation of p-diaminotoluene (RH₂) was examined by flash-spectroscopy and the mechanism was elucidated. The first chemical reaction is the generation of two free radicals from the triplet dye and the hydrogen donor. These radicals may react in several ways without oxygen: or additionally with oxygen: The connection of this mechanism with photodynamic action is discussed.     

The Application of Suzuki Coupling Reaction on the Preparation of Carbosilane Dendrimers with 4-(Naphthalen-1-yl)phenyl Core

The functionalized carbosilane dendrimers can be divided into three categories: surface- functionalization, core-functionalization and focal-point functionalization1-5. The func- tionalized dendrimers can be used as catalyst supporters, medicine control-r…     

Molecular dynamics simulations of PVP kinetic inhibitor in liquid water and hydrate/liquid water systems

The possible effects of PVP (poly(N-vinylpyrrolidone)) on the properties of liquid and water in clathrate hydrate has been investigated using NVT molecular dynamics simulations. A model for a monomer of the PVP polymer is immersed in three systems, liquid water, a unit cell of a hydrate in liquid water with a hydrate former and a third system where some of the liquid water molecules of this last system are replaced by a PVP monomer. Both molecular dynamics simulation and integral equation theory predict hydrogen bonding between the double bonded oxygen in the PVP ring and hydrogens in water. For the composite system, the PVP monomer has a preference for hydrogen bonding to hydrogens from the water molecules at the surface of the hydrate lattice. The simulations indicate that the PVP monomer tends to orient perpendicular to the hydrate surface. For the model systems in this study PVP may form hydrogen bonds with liquid water through the double bonded oxygen in the ring. When a hydrate crystal is immersed in the liquid water phase this hydrogen bonding is shifted towards the hydrate due to a more favourable Coulomb interaction involving hydrogens from more than one water molecule at the hydrate surface. The PVP monomer has a preference for perpendicular orientation with respect to the hydrate surface. A scheme is suggested for the characterization of kinetic hydrate inhibitors based on molecular dynamics simulations and on three basic properties. In addition to the energy between the active groups of the inhibitor and hydrate water another point of focus is the free energy changes in the interactions between the inhibitor and water as the charges are changed from zero to the original model charges. In particular the difference between this integral for the (hydrate water)–(PVP monomer) interaction and the (liquid water)–(PVP inhibitor) interaction should reflect the driving forces in freezing the inhibitor out from the liquid water phase and onto the hydrate surface. The third property in the characterization scheme is the diffusivities of groups connecting to the hydrate crystal, relative to the diffusivities of the hydrate crystal. Results are presented from simulations where a small cavity with a methane model as a guest is immersed in liquid water with free methane molecules at a temperature of 150K. Changes in structure, diffusivities and energy indicate a tendency towards a more solid–like structurde around the cavity.     

Corroding the chromium cation

Two [Cr,O₂]⁺ isomers have been selectively produced and studied by FT-ICR mass spectrometry. The Cr(O₂)⁺ complex was formed by supersonically expanding a plasma produced by laser vaporization of chromium metal with the helium carrier gas, which was seeded with traces of oxygen, while the chromyl cation is formed in an expansion with N₂O. The complex is stable against thermal collisions, but in a bimolecular reaction with water it is rapidly converted to the chromyl cation, with ligand exchange being only a minor side reaction. Isotopic studies suggest a side-on geometry for Cr(O₂)⁺, in accordance with density functional (B3LYP) calculations. The present work indicates that an investigation of the selected isomers can indeed be carried out, if appropriate chemical methods for the ion generation are applied.     

Radiation from a Point Charge Moving through a Circular Aperture in a Screen

This paper deals with the problem of diffraction radiation froman electric point charge that moves, at a constant speed, througha circular aperture in a plane screen. The screen is assumedto be electrically perfectly conducting. The problem is reducedto the solution of an integral equation for an unknown fieldfunction in the aperture. Low-frequency solutions as well ashigh-frequency solutions are obtained. Results pertaining tothe far-field behaviour of the radiated field are given. Finally,numerical results pertaining to the radiation loss of the chargeare presented.     

SENSIBILISIERTE PHOTOOXIDATION DURCH METHYLENBLAU, THIOPYRONIN UND PYRONIN — II. PHYSIKOCHEMISCHE GRUNDLAGEN DER PHOTODYNAMISCHEN WIRKUNG VON THIOPYRONIN

Abstract— The physical-chemical properties of thiopyronine which result in its outstanding photodynamic effectiveness (in comparison to methylene blue and pyronine) are: (1) High velocity of free radical generation (kinetics followed by spectroscopy after flash photolysis). (2) High velocity of reoxidation of free radical (rate constant determined by kinetic spectroscopy under aerobic conditions). (3) Fairly positive reduction potential of oxidized free radical (from polarographic analysis of redox behavior). (4) Irreversible oxidation behavior of leuco-thiopyronin in contrast to leuco-methylene blue (the structure of leuco-thiopyronin was elucidated by NMR-analysis). (5) Fairly high equilibrium constant for complex formation with DN A (determination by high sensitive pulse-polarography).
From the sedimentation behavior and T-jump relaxation of in vitro photodynamically treated DNA it is shown that not only does guanine photooxidation take place but also single- and double-strand breaks can occur. The mechanism of this phenomenon is not yet elucidated.