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  • 1
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 1549-1572 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The binding of the antitumor agent CC-1065 to a variety of poly- and oligonucleotides was studied by electronic absorption, CD, and resistance to removal by Sephadex column chromatography. Competitive binding experiments between CC-1065 and netropsin were carried out with calf-thymus DNA, poly(dI-dC) · poly(dI-dC), poly(dI) · poly(dC), poly(rA) · poly(dT), poly(dA- dC) · poly(dG-dT), and poly(dA) · 2poly(dT). CC-1065 binds to polynucleotides by three mechanisms. In the first, CC-1065 binds only weakly, as judged by the induction of zero or very weak CD spectra and low resistance to extraction of drug from the polynucleotide by Sephadex chromatography. In the second and third mechanisms, CC-1065 binds strongly, as judged by the induction of two distinct, intense CD spectra and high resistance to extraction of drug from the polynucleotide, by Sephadex chromatography in both cases. The species bound by the second mechanism converts to that bound by the third mechanism with varying kinetics, which depend both on the base-pair sequence and composition of the polynucleotide. Competitive binding experiments with netropsin show that CC-1065 binds strongly in the minor groove of DNA by the second and third mechanisms of binding. Netropsin can displace CC-1065 that is bound by the second mechanism but not that bound by the third mechanism. CC-1065 binds preferentially to B-form duplex DNA and weakly (by the first binding mechanism) or not at all to RNA, DNA, and RNA-DNA polynucleotides which adopt the A-form conformation or to single-strand DNA. This correlation of strong binding of CC-1065 to B-form duplex DNA is consistent with x-ray data, which suggest an anomalous structure for poly(dI) · poly(rC), as compared with poly(rI) · poly(dC) (A-form) and poly(dI) · poly(dC) (B-form). The binding data indicate that poly(rA) · poly(dU) takes the B-form secondary structure like poly(rA) · poly(dT). Triple-stranded poly(dA) · 2poly(dT) and poly(dA) · 2poly(dU), which are considered to adopt the A-form conformation, bind CC-1065 strongly. Netropsin, which also shows a binding preference for B-form polynucleotides, also binds to poly(dA) · 2poly(dT) and occupies the same binding site as CC-1065. These binding studies are consistent with results of x-ray studies, which suggest that A-form triplex DNA retains some structural features of B-form DNA that are not present in A-form duplex DNA; i.e., the axial rise per nucleotide and the base tilt. Triple-stranded poly(dA) · 2poly(rU) does not bind CC-1065 strongly but has nearly the same conformation as poly(dA) · 2poly(dT) based on x-ray analysis. This suggests that the 2′-OH group of the poly(rU) strands interferes with CC-1065 binding to this polynucleotide. The same type of interference may occur for other RNA and DNA-RNA polynucleotides that bind CC-1065 weakly.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: The generation of grafting radicals by electron irradiation is measured ESR spectroscopically in different celluloses. It is shown that the formation of radicals depends strongly on the moisture and that the radical decay led to the conclusions of two different radical structures. The mobility of the radicals in the amorphous region is strongly influenced by the moisture content of cellulose. This is used to explain the grafting reactions of ionic monomers onto cellulose. Grafting of a useful extent of ionic monomers was done at low energy doses without a remarkable degradation of the cellulose.
    Notes: Die Erzegung pfropffähiger Radikale mittels Elektronenbestrahlung wird für verschiedene Celluloseproblen ESR-spektroskopisch verfolgt. Es wird gezeigt. Es wird gezeigt, daß die Bildung der Radikale in starkem Maße. vom Feuchtegehalt der Proben abhängt und die Abreaktion auf zwei unterschiedliche Radikalstrukturen schlißen läßt. Die Beweglichkeit der Radikale wird vom Feuchtegehalt der Cellulose im amorphen Bereich stark beeinflußt. Daraus lassen sich die Pfropfreaktionen mit ionisch geladenen Monomeren an Cellulose erklären. Die Propfung konnte so geführt werden, daß bei einer geringen Bestrahlungsdosis eine ausreichende ionische Ausrüstung der Cellulose erfolgt, ohne einen merklichen Strahlenabbau der Cellulose in Kauf nehmen zu müssen.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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