An unexpected G-G base pairing caused by the coordination of platinum(II) at the N(7) position of 9-ethylguanine

Faggiani, R.; Lock, C. J. L.; Lippert, Bernhard

doi:10.1021/ja00536a062

Cited by 71 publications

(25 citation statements)

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“…The Pt atom lies on an inversion centre and the environment is planar and almost exactly square; both the chelate and nonchelate cis-N--Pt--N angles are close to 90 °. The Pt--N bond lengths [2.023 (3), 2.014 (3)•] do not differ significantly and agree well with those we have measured previously, where Pt was bound to the imidazole ring in purine derived molecules (BeyerlePfnur, Brown, Faggiani, Lippert & Lock, 1985;Faggiani, Lippert, Lock & Speranzini, 1982;Faggiani, Lock & Lippert, 1980;Lippert, Lock & Pilon, 1984;Lock, Speranzini, Turner & Powell, 1976). Bond lengths within the bound phosphinic acid agree well with those observed in the free phosphonic acid (Howard-Lock et al, 1989), particularly when compared to the unprotonated ring.…”

Section: Introductionsupporting

confidence: 88%

Bis[di(imidazol-2-yl)phosphinato-N3,N3']platinum(II) tetrahydrate

Britten¹,

Lock²,

Wang³

1993

Acta Crystallogr C

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Section: Introductionsupporting

confidence: 88%

Bis[di(imidazol-2-yl)phosphinato-N3,N3']platinum(II) tetrahydrate

Britten¹,

Lock²,

Wang³

1993

Acta Crystallogr C

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“…Thus, Scheme 2a is an example for the involvement of a second nucleobase (X ϭ guanine) in self-association (v in Scheme 4), as are compounds V (14) and VI (15) tion (vii in Scheme 4). This pair by far exceeds the normal G,C Watson-Crick pair in strength (47)(48)(49)(50).…”

Section: Discussionmentioning

confidence: 86%

Canonical and unconventional pairing schemes between bis(nucleobase) complexes oftrans-a₂Pt^II: Artificial nucleobase quartets and C—H…N bonds

Freisinger

Rother

Lüth

et al. 2003

Proc. Natl. Acad. Sci. U.S.A.

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If two nucleobases are crosslinked by trans-a2Pt II , self-association via H bonding may take place either through individual bases or jointly through both bases. Due to the blockage of an acceptor site by the metal, the number of feasible pairing patterns can be reduced, and the preferred ones altered. If the metalated base pair as a whole undergoes association, base quartets can form. Various scenarios resulting from the application of guanine, hypoxanthine, and cytosine model nucleobases are discussed. Unconventional COH. . .N hydrogen bonding has been observed in several instances.H bonding ͉ platinum T he existence of cyclic guanine (G) quartets and the association of poly(G) and poly(I) into four-stranded structures have been known for quite some time (1, 2). Proof of the formation of G quartets in telomere sequences (3) and their existence in human cells (4), new insights on the structure of human telomeric DNA (5, 6), and, above all, implications that G quartets are potential drug targets for the chemotherapy of cancer, on the one hand, and can play a dysfunctional role, on the other (7), have made the field of DNA quadruplex structures a booming area. From an inorganic chemistry point of view, the involvement of metal ions in the formation and stabilization of G 4 structural elements is of particular interest. That these cations, K ϩ and Na ϩ under physiological conditions and many other cations under nonphysiological conditions, are absolutely essential for maintaining the G 4 structure elements has been recognized at an early stage. Moreover, it is now clear that a stem of G 4 quartets stabilizes other quartet structures, including those between dimers of Watson-Crick pairs, e.g., [GC] 2 (C, cytosine) (8).Small molecules that bind specifically to quadruplex DNA, thereby interfering with the enzyme telomerase or inhibiting expression of a crucial gene, are believed to be useful for chemotherapeutic applications. Among these, cationic porphyrins such as tetra-(N-methyl-4-pyridyl)porphine are particularly promising (4, 9, 10). Our interest in this area stems from our experience with metal-nucleobase complexes representing artificial base quartets that are cationic and flat and that have dimensions compatible with the natural base quartets. Because of their shape and charge, these compounds can be expected to have a natural affinity for tetra-stranded DNA in general and telomere sequences in particular. The use of metal ions (M) displaying linear coordination geometries and the fact that purine nucleobases, on simultaneous metal binding to N1 and N7, provide 90°angles between their M-N vectors and hence represent angular building blocks of squares and rectangles have enabled the construction of a variety of artificial M-base quartets (11-16). Examples are given in Scheme 1. Depending on the metal ions applied and the degree of crosslinking, these quartets can be kinetically labile or robust, also occasionally assembled by remarkably strong H bonds, even in solution. It will be our ultimate goal to probe t...

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“…All the formation and acid dissociation constants were determined with the SPECFIT program. [20] The rate constants k obs1 and k obs2 for the consecutive reaction [reactions (3) and (4)] were determined simultaneously according to the equation: A t ϭ A e ϩ αexp(Ϫk obs1 t) ϩ βexp(Ϫk obs2 t), in which A t and A e are the absorbances at time t and ϱ, respectively, and α and β are composite parameters. [21] …”

Section: Resultsmentioning

confidence: 99%

Mechanisms of the Axial Ligand Substitution Reactions of Dinuclear, Head‐to‐Head α‐Pyrrolidonato‐ and Pivalamidato‐Bridged cis‐Diammineplatinum(III) Complexes with Halide Ions

et al. 2003

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The acid dissociation constant of the axial aqua ligand in the Head-to-Head (HH) dinuclear pivalamidato-bridged cis-di-) and the formation constants of the successive substitution reactions on the axial sites of the HH α-pyrrolidonato-bridged cis-diammineplatinum(III) dinuclear complex and the HH pivalamidato-bridged cis-diammineplatinum(III) dinuclear complex with halide ions X − (X − = Cl − and Br − ) to give monohalo and dihalo complexes were determined spectrophotometrically at 25°C and I = 2.0 M. A kinetic study was also performed for the monohalo and dihalo complex formations. The effect of the bridging ligand upon the axial site reactivity was compared and discussed. The ligand substitution behavior of the monohalo complex was af-

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An unexpected G-G base pairing caused by the coordination of platinum(II) at the N(7) position of 9-ethylguanine

Cited by 71 publications

References 1 publication

Bis[di(imidazol-2-yl)phosphinato-N3,N3']platinum(II) tetrahydrate

Bis[di(imidazol-2-yl)phosphinato-N3,N3']platinum(II) tetrahydrate

Canonical and unconventional pairing schemes between bis(nucleobase) complexes oftrans-a₂Pt^II: Artificial nucleobase quartets and C—H…N bonds

Mechanisms of the Axial Ligand Substitution Reactions of Dinuclear, Head‐to‐Head α‐Pyrrolidonato‐ and Pivalamidato‐Bridged cis‐Diammineplatinum(III) Complexes with Halide Ions

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An unexpected G-G base pairing caused by the coordination of platinum(II) at the N(7) position of 9-ethylguanine

Cited by 71 publications

References 1 publication

Bis[di(imidazol-2-yl)phosphinato-N3,N3']platinum(II) tetrahydrate

Bis[di(imidazol-2-yl)phosphinato-N3,N3']platinum(II) tetrahydrate

Canonical and unconventional pairing schemes between bis(nucleobase) complexes oftrans-a2PtII: Artificial nucleobase quartets and C—H…N bonds

Mechanisms of the Axial Ligand Substitution Reactions of Dinuclear, Head‐to‐Head α‐Pyrrolidonato‐ and Pivalamidato‐Bridged cis‐Diammineplatinum(III) Complexes with Halide Ions

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Canonical and unconventional pairing schemes between bis(nucleobase) complexes oftrans-a₂Pt^II: Artificial nucleobase quartets and C—H…N bonds