Hole transfer in DNA: DNA as a scaffold for hole transfer between two organic molecules

Hole transfer process in ODNs conjugated with two organic molecules, pyrene (Py) and phenothiazine (Ptz) was investigated with the pulse radiolysis measurements. Monitoring the transient absorption of Py⁺ and Ptz⁺, it was shown that the hole transfer rate was dependent on the distance and sequence between Py and Ptz.     

Fluorescence and Laser photolysis studies on 1,2,4,5-tetracy anobenzene CT complexes in micellar solutions

CT complexes of 1,2,4,5-tetracyanobenzene were formed in the inner part of neutral micelles and in the surface region of ionic ones. The excitation of the CT absorption band of these complexes gives broad and structureless CT fluorescence spectra, their lifetimes being relatively short (≈10 ns). Micellar effect upon ionic photodissociation was observed, and their quantum yeild is smaller than that obtained in acetonitrile. These results are quite different from those on another typical excited CT system of pyrene and N,N-dimethylaniline.     

Thermal and mechanical properties of radiation crosslinked poly(tetrafluoroethylene-co-perfluoromethyl vinyl ether)

The effect of irradiation temperature on the polymer properties was investigated for the fluoroelastomer poly(tetrafluoroethylene-co-perfluoromethylvinyl ether) (TFE/PMVE). TFE/PMVE samples were γ-irradiated to 150 kGy at temperatures ranging from 77 K to 373 K. Analysis of the sol/gel behaviour, tensile properties, and glass transition temperatures indicated that crosslinking commenced in the temperature range 195 to 263 K, for a dose of 150 kGy. The latter temperature was 13 K below the glass transition temperature. Crosslinking remained relatively constant to higher temperatures. Chain scission reactions were found to occur well below the glass transition temperature and increased at higher temperatures. The optimum temperature for the radiation crosslinking of TFE/PMVE, for the temperatures investigated, was 263 K.     

Studies on reactions of the N-phosphonium salts of pyridines. XIII. Direct polycondensation reaction of carbon dioxide or disulfide with diamines under mild conditions

Polyureas of high molecular weight were obtained by the direct polycondensation reaction of carbon dioxide with diamines at 40°C for several hours under a pressure of carbon dioxide (below 30 atm) by use of diphenyl phosphite in pyridine. Optimal temperature and pressure were 40°C and 20 atm of carbon dioxide. The polycondensation reaction was also affected by solvents and type and amounts of tertiary amines. Pyridine was most effective as tertiary amine and solvent as well. Of the phosphorous compounds used, triaryl phosphites and diphenyl phosphite were most effective, but trialkyl phosphites failed to give polymer. The reaction was assumed to proceed via a carbamyl N-phosphonium salt of pyridine formed by dephenoxylation of phosphites. Similarly, polythioureas were prepared by heating a mixture of carbon disulfide, diamines, and diphenyl phosphite in pyridine at 40°C for 6 hr under nitrogen.     

A new method of constructing dearomatized compounds using triazene

We are reporting on a new method of constructing dearomatized compounds from α-substituted aryltriazenes. Deprotonation occurs at C atom α to N3. Nucleophilic attack of generated anion at the ortho-position of aryl group forms a new carbon-carbon bond. A stereoselective reaction was observed when the substituents on the C α to N3 are tied together in either a pyrrolidine or a piperidine. The product of this reaction possessed an interesting dearomatized tetrahydrobenzotriazine framework.     

Molecular structure of 3-methylthiophene studied by gas electron diffraction combined with microwave spectroscopic data

The molecular structure of 3-methylthiophene

has been determined by gas electron diffraction (GED) combined with microwave (MW) spectroscopic data. Ab initio calculations at the HF/3–21G* level were carried out and used as structural constraints in the data analysis. The torsional vibration of the methyl group was treated as a large-amplitude motion. The structural parameters were determined to be: r_g(S---C₂) = 1.719(2) Å, r_g(C₂=C₃) = 1.370(3) Å, r_g(C₃---C₆) = 1.497(6) Å, r_g(C₂---H) = 1.101(5) Å, CSC = 91.6(2)°, SC₂C₃ = 113.3(5)°, SC₅C₄ = 111.3(3)°, C₂C₃C₆ = 123.2(11)° and C₃C₆H = 112(2)°. The values of r(S---C₂) − r(S---C₅) and r(C₂=C₃) − r(C₄=C₅) were fixed at the 3–21G* value of 0.002Å. Parenthesized values are the estimated limits of error (3σ) referring to the last significant digit.     

Molecular structure of 3-methylthiophene studied by gas electron diffraction combined with microwave spectroscopic data

The molecular structure of 3-methylthiophene has been determined by gas electron diffraction (GED) combined with microwave (MW) spectroscopic data. Ab initio calculations at the HF/3–21G* level were carried out and used as structural constraints in the data analysis. The torsional vibration of the methyl group was treated as a large-amplitude motion. The structural parameters were determined to be: r_{g(S---C2) = 1.719(2) Å}, r_{g(C2=C3) = 1.370(3) Å}, r_{g(C3---C6) = 1.497(6) Å}, r_{g(C2---H) = 1.101(5) Å}, CSC = 91.6(2)°, SC₂C₃ = 113.3(5)°, SC₅C₄ = 111.3(3)°, C₂C₃C₆ = 123.2(11)° and C₃C₆H = 112(2)°. The values of r(S---C₂) - r(S=C₅) and r(C₂=C₃)-r(C₄ =C₅) were fixed at the 3–21G* value of 0.002 Å. Parenthesized values are the estimated limits of error (3σ) referring to the last significant digit.     

Conjugate-gradient method for computing the Moore-Penrose inverse and rank of a matrix

A conjugate-gradient method is developed for computing the Moore-Penrose generalized inverseA of a matrix and the associated projectors, by using the least-square characteristics of both the method and the inverseA . Two dual algorithms are introduced for computing the least-square and the minimum-norm generalized inverses, as well asA . It is shown that (i) these algorithms converge for any starting approximation; (ii) if they are started from the zero matrix, they converge toA ; and (iii) the trace of a sequence of approximations multiplied byA is a monotone increasing function converging to the rank ofA. A practical way of compensating the self-correcting feature in the computation ofA is devised by using the duality of the algorithms. Comparison with Ben-Israel's method is made through numerical examples. The conjugate-gradient method has an advantage over Ben-Israel's method.After having completed the present paper, the author received from Professor M. R. Hestenes his paper entitledPseudo Inverses and Conjugate Gradients. This paper treated the same subject and appeared in Communications of the ACM, Vol. 18, pp. 40–43, 1975.