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  • Polymer and Materials Science  (5)
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  • 1
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The fixation of cis (NH3)2Cl2Pt(II) to poly(I)·poly(C) leads to the formation of two complexed species. One involves coordination to a single base (accounting for about 70% of the total platinum bound over the rb range 0.07-0.25) and the other to two bases which are not adjacent to each other but may be on the same strand and separated by a loop. Reaction of the platinum compound with poly(I) gives in addition to the above two species a minor one (about 15%, independent of rb over the range 0.05-0.30) in which the platinum is bound to two adjacent bases. The availability of such coordination reduces the dominance of the 1:1 species, which, however, remains the major one (ca. 55%).
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 1143-1143 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 973-983 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The fixation of dien-Pt on poly(I)·poly(C) leads to only minor changes in the uv and CD spectra at ambient temperature, showing that there is little perturbation of the secondary structure in the rb range studied (up to 0.30). However, the melting profiles show two steps. The Tm for strand separation increases linearly from 61°C (rb = 0) to 80°C (rb = 0.18), after which it declines on further increasing the rb. The second melting step is not complete at 100°C, and the magnitude of the absorbance change in this second step also appears to be at a maximum at rb = 0.18. Although dien-Pt can only coordinate to one base, the nmr spectra at 80°C also show a second type of interaction with the adjacent bases, which is only destroyed in the presence of a strong denaturing agent, 5M guanidinium hydrochloride. From these results and the spectrophotometric data, we observe that dien-Pt forms a triple sandwich by hydrogen bonding of the platinum amino groups to the adjacent hypoxanthine bases (N7). The presence of these hydrogen bonds accounts for the increased stability (maximal at one Pt to three hypoxanthine bases) and their rupture is seen in the second melting step. No interaction has been observed with poly(C) strand. Reaction of dien-Pt with poly(I) shows the formation of the same triple sandwich structure in the nmr spectra.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The fixation of trans-(NH3)2Cl2 Pt(II) to poly(I)·poly(C) at low rb (〈 0.05) leads to the formation of two complexed species. The major species (ca. 82% of bound platinum) involves coordination of platinum to a single hypoxanthine base, while the other species involves coordination of two hypoxanthine bases, which are either far apart on the same strand or on separate poly(I) strands, to the platinum. These same two species are found after reaction with poly(I), as are two other species throughout the entire rb range studied (rb = 0-0.30). The latter two species are assigned to trans-Pt bound to two bases on a poly(I) strand with (a) one or (b) two free bases between the two bound bases. These two species, (a) and (b), account for ca. 35% of the bound platinum, although the 1:1 species remains dominant (ca. 55%). These two additional species are observed at high rb (〉0.075) after reaction with poly(I)·poly(C) but as very minor species. They are formed by reaction with melted poly(I) loops. Also at high rb, we have observed a shifted cytidine H5 resonance arising from interaction of trans-Pt with a melted loop of poly(C). Most probably, this arises from an intramolecular poly(I) to poly(C) crosslink. Results from the reaction of trans-Pt with poly(C) are presented for comparison.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 945-960 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The covalent binding of trans-Pt (NH3)2Cl2 to the double-stranded poly(I)·poly(C) follows three types of reactions, depending on rb and the concentration of polynucleotide in the reaction mixture. At rb ≤ 0.1, the principal reaction is coordination to poly(I), giving rise to some destabilization of the double strand, as shown by uv and CD spectra, and a decrease in Tm values, giving rise to free loops of poly(C). At higher rb and low polynucleotide concentration, the free cytidine bases react with platinum bound on the complementary strand to form intramolecular (interstrand) crosslinks that restabilize the double-stranded structure. At high rb and high polynucleotide concentration, while the above reaction still occurs, the predominant one is the formation of intermolecular crosslinks. Under no conditions has strand separation been observed.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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