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Topological implications of Y-conjugation for electronic transitions of cyanine dyes (1987)

Grajcar, Lydie ; Berthier, Gaston ; Faure, Jean ; [et al.]

Springer

Theoretical chemistry accounts 71 (1987), S. 299-304

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ISSN: 1432-2234

Keywords: Graph theory ; Conjugation ; Cyanine spectra

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology

Notes: Abstract To understand connections between electronic transitions of dyes having related conjugated systems, topological arguments from graph theory are often helpful. Using the Chebyshev expansion of the characteristic polynomials of cyanines, it is shown that the two possible structures of tribranched cyanines, i.e., a strongly out-of-plane orientation of one of the conjugated branches or a Y-conjugation of the entire unsaturated system, are both consistent with the similarities between visible absorption of these compounds and of simple chains. To choose between these two structures, evidence from other sources should be added.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00529101

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Force field for platinum binding to adenine (1993)

Kozelka, Jir̆í ; Savinelli, Roger ; Berthier, Gaston ; [et al.]

New York, NY [u.a.] : Wiley-Blackwell

Journal of Computational Chemistry 14 (1993), S. 45-53

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ISSN: 0192-8651

Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology , Computer Science

Notes: The antitumor drug cis-diamminedichloroplatinum(II) (cisplatin) binds preferentially to GpG and ApG sequences of DNA, forming N7,N7 intrastrand chelates. Molecular modeling of the intrastrand adducts have been handicapped, so far, by the lack of force-field data describing the Pt-guanine and Pt-adenine binding. We used ab initio calculations with relativistic pseudopotentials to evaluate three important parameters for the platinum-adenine model complex [Pt(NH3)3(Ade)]2+: (1) the force constant for the Pt—N7 bond bending out of the adenine plane; (2) the energy profile for the torsion about Pt—N7; (3) a set of fractional atomic charges that reproduce the ab initio potential for a number of space points placed around the adduct. A population analysis and comparative study on the tetrammine complex [Pt(NH3)4]2+ have shown that for platinum adenine is a better σ-donor than NH3, but its capacity as a π-acceptor is weak. © 1993 John Wiley & Sons, Inc.

Additional Material: 6 Ill.