PROFLAVINE MEDIATED PHOTOINACTIVATION OFBACTERIOPHAGE φX174 AND ITS ISOLATED DNA: EFFECTS OF AGENTS MODIFYING VARIOUS PHOTOCHEMICAL PATHWAYS

Abstract. Thiols and disulfides protect both φX174 phage and its isolated DNA from the lethal action of proflavine plus light. The protective ability of these compounds appears to be attributed to the -SH or the -S-S- group and the property to interact with the proflavine-phage DNA complex. The phage inactivation efficiency per proflavine bound to DNA is reduced by 50 to 30% upon addition of cysteine or cystamine. Substances that affect the lifetime of singlet oxygen modify the rate of phage photoinactivation in the presence of proflavine; the inactivation rate is decreased by N^-₃ and increased by D₂O. Irradiation under N₂ atmosphere markedly decreases the phage photosensitization by proflavine. Irradiation with monochromatic light of 440 nm is less efficient than irradiation with light of 440 nm plus 360 nm, and the difference is more pronounced in N₂ than in air. These results are discussed in relation to various possible photochemical pathways.     

The Reaction of Norbornene with Lead Tetraacetate and Thallium Trinitrate. Preliminary communication

The reaction of norbornene with lead tetraacetate is found to be much more complex than previously reported. In acetic acid and in benzene, the syn-7-norbornenyl, 3-nortricyclyl, and syn and anti-7-acetoxy-exo-2-norbornyl acetates were characterized. In methanol, the isolated products represented most of those expected from the competition of methanol and acetate in the neutralization of the intermediate carbocations. The reaction of norbornene with thallium trinitrate in the above solvents yielded very complex mixtures besides the above mentioned products which were formed in about 50% yield.     

An Analytical Study of Molecular Transport in a Zeolite Crystallite Bed

Analytical solutions of the diffusion equations to obtain the diffusant concentrations in the macro- and micropores which constitute the pore system of a zeolite bed are presented. The parameter which determines the influence of each pore type on the evolution of the adsorbate/adsorbant system towards the equilibrium state is described. Examples are given to illustrate a qualitative and quantitative study based on the curves obtained from these equations.     

Structure du radical cyano-vinyle CH2=Ċ-CN Etude expérimentale et théorique

Résumé Tout d'abord, on montre par RPE que le radical CH₂=-CN possède à basse température une structure instable pliée et à température plus élevée une structure stable linéaire. Un calcul théorique sur ce radical ainsi que sur le radical butatriényle est en bon accord avec les résultats expérimentaux.

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The structure of the Cyano-Vinyl Radical CH₂=-CN experimental and theoretical study

First, it is shown by ESR that the radical CH₂=-CN at low temperature presents an unstable bent structure and at higher temperature a stable linear structure. A theoretical calculation on this radical and on the butatrienyl one is in good agreement with the experimental results.

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Zusammenfassung Aus ESR Messungen wird gefolgert, daß das Radikal CH₂=-CN bei tiefer Temperatur in einer instabilen gebogenen Struktur und bei höherer Temperatur in einer stabilen linearen Struktur vorliegt. Theoretische Berechnungen stehen sowohl für dieses als auch für das Butatrienyl-Radikal in guter Übereinstimmung mit experimentellen Daten.

     

THE REACTION BETWEEN SUPEROXIDE ANION AND HYDROGEN PEROXIDE

Abstract— In order to obtain a better understanding of the kinetics of the Haber-Weiss reaction

often proposed as a source of OH radicals, we have measured the decomposition rate of H₂O₂ in aqueous solutions by y rays and for different pH values. This decomposition proceeds by a chain reaction involving the preceding one as the propagating step.
The rate constant found is to be
     

Solvent extraction of protactinium(v) with bis(2-ethylhexyl)phosphoric acid in toluene

The extraction of Pa(V) from 1M perchloric acid medium with HDEHP in toluene was carried out. The different factors affecting the metal distribution coefficient such as HDEHP concentration in the organic phase, pH of the aqueous phase and the equilibrium temperature were followed. From the data obtained the equilibrium constants of the extraction reaction were calculated. From the temperature variation, the corresponding thermodynamic parameters (G, H and S) were also derived. In the same way, the effect of addition of some N-and 0-containing solvents such as pyridine, 2,2-dipyridyl, n-amyl alcohol, n-decyl alcohol and n-butyl acetate, to the HDEHP organic phase was demonstrated. From the data obtained the suggested mechanisms for the synergistic extraction reactions were discussed together with the corresponding values of the thermodynamic parameters.     

Phénylhalogénohydrodigermanes

The symmetric and unsymmetric phenylchlorohydrodigermanes can be isolated or characterized via partial halogenation of the Ge? H bonds of the symmetrical phenylhydrodigermanes Ph₂(H)GeGe(H)₂Ph, Ph(H)₂GeGe(H)₂Ph by chloromethyl methyl ether and carbontetrachloride. Some of these phenylchlorohydrodigermanes are formed by insertion of phenylchlorogermylene (PhGeCl) on the Ge? H or Ge? Cl bonds of the phenylchlorohydrogermanes. The hydrolysis of the monochloro phenylhydrodigermanes Ph₂(Cl)GeGe(H)₂ and Ph(Cl)(H)GeGe(H)₂Ph leads to the phenyl phenylhydrogermyl digermoxanes [Ph₂(H)GeGePh₂]₂O and [Ph(H)₂GeGe(H)Ph]₂O. Treatment of these oxides with the concentrated aqueous solutions of hydracides leads to the monofluorinated, brominated and iodinated phenylhydrodigermanes Ph₂(H)GeGe(X)Ph₂ and Ph(H)₂GeGe(H)(X)Ph (X) = F, Br, I). Phenylchlorohydrodigermanes decompose thermally by α-elimination on one germanium atom with formation of germylene and phenylchlorohydrogermane. The physico-chemical IR. and NMR. study of these phenylhalogenohydrodigermanes indicates that, if the vGe? H frequency variations are mostly linked to the inductive effects of the substituents on the same germanium, the variations of the chemical shifts of the Ge? H protons seem to be due to many factors and especially to the inductive effect of the substituents on the germanium and the magnetic anisotropy of the Ge? X bonds.     

On the affinity of cytosine towards electrophiles

Ab initio SCF computations on the intrinsic preferences of the H⁺, CH ₃ ⁺ and C₂H ₅ ⁺ cations towards the two principal sites of protonation or alkylation on cytosine, N₃ or O₂, show that this preference undergoes a continuous modification with the increase in size and complexity of the cation. N₃ is the preferred site of fixation of H⁺, O₂ the preferred site of C₂H ₅ ⁺ , while CH ₃ ⁺ has no marked preference. The exchange repulsion term of the binding energy appears responsible for the preference of C₂H ₅ ⁺ for O₂.This work was supported by the Ligue Francaise contre le Cancer and the National Foundation for Cancer Research (USA)     

Stereochimie de l'action des organomagnesiens et des organolithiens sur les dimethyl-1,2 alcoxy-1 silacyclobutanes

The reaction of organomagnesium organolithium compounds (alkyl, aryl, allyl and benzyl derivatives) with 1,2-dimethyl-1-alkoxy-l-silacyclobutanes proceeds with retention of configuration at the silicon atom. Stereochemical results are discussed in terms of the S_N2Si mechanism. The proposed configurations are supported by ¹H and ¹³C NMR data.