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  • 1
    Electronic Resource
    Electronic Resource
    The TpG chelate of cis(diammineplatinum) forms two head-to-head rotamers in H2O solution (1998)
    Springer
    JBIC 3 (1998), S. 30-43 
    Details
    ISSN: 1432-1327
    Keywords: Key words Cisplatin ; Antitumor drugs ; Nuclear magnetic resonance ; Molecular dynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract  d(TpG)– reacts with cis-[Pt(NH3)2(H2O)2]2+ in two steps to yield the platinum chelate cis-[Pt(NH3)2{d(TpG)-N3(1),N7(2)}]. In the latter, hindered rotation of the bases leads to an equilibrium between two rotamers interconverting slowly on the NMR time scale. The structure of the two rotameric chelates was studied by means of 1H NMR and molecular modeling techniques. The major and minor rotamers could be assigned unambiguously to the two head-to-head conformational domains which are characterized by syn/anti and anti/anti sugar-base orientations, respectively. Molecular models derived for both rotamers show that the orientations of the bases are mutually quasi-enantiomeric. The interconversion between the two rotamers (k ≈ 1 s–1 at 293 K) is approximately 104 times faster than the analogous rotamer interconversion observed in cis-[Pt(NH3)2{r(CpG)-N3(1),N7(2)}]+ [Girault J-P, Chottard G, Lallemand J-Y, Huguenin F, Chottard J-C (1984) J Am Chem Soc 106 : 7227–7232], suggesting that the steric clash of the exocyclic amino group of the platinum-bound cytosine with the ligands in cis position is more severe than that of the two thymine oxo groups.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s007750050205
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  • 2
    Electronic Resource
    Electronic Resource
    Circular dichroism spectra of the individual rotamers of [Pt(N,N-dmen)(GpG)]+ (N,N-dmen=N,N-dimethylethylenediamine) indicate that the base-base oscillator coupling is not the main source of ellipticity in cis-PtG2L2 head-to-head complexes (2000)
    Springer
    JBIC 5 (2000), S. 45-50 
    Details
    ISSN: 1432-1327
    Keywords: Key words Circular dichroism ; Molecular modeling ; Oligonucleotides ; Platinum complexes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract  The asymmetrical platinum complex [PtCl2(N,N-dmen)] (N,N-dmen=N,N-dimethylethylenediamine) reacts with the dinucleotide GpG to form two isomeric chelates of the formula [Pt(N,N-dmen)(GpG)]+ [9]. One of the isomers forms two stable rotamers separable by HPLC, whereas the other apparently prefers one single rotameric form. The favored conformations of these three forms were elucidated by means of molecular mechanics and dynamics techniques. In parallel, we have prepared the adduct, isolated the three rotamers, and recorded their solution circular dichroism (CD) spectra. For the first time we were thus able to correlate the CD features of individual rotamers of a cis-Pt(GpG) chelate with their structures. We show here that the two forms labeled in Inagaki's paper 1'e and 2e have the same right-handed helicoidal arrangement of the guanine bases but display different CD spectra in which the prominent bands have inverted signs. Thus, base-base interactions cannot be the principal cause of the CD of these compounds.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s007750050006
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