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  • 1985-1989  (3)
  • 1980-1984  (10)
  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of medicinal chemistry 25 (1982), S. 220-227 
    ISSN: 1520-4804
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Macromolecules 17 (1984), S. 1709-1711 
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Macromolecules 19 (1986), S. 1271-1272 
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 105 (1983), S. 1705-1712 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Based on steric and electrostatic considerations, the prerequisites for binding to DNA via the intercalation mechanism are proposed. Steric contour energy curves are presented to demonstrate the region inaccessible to an intercalant. They are calculated with a 6-n (n = 14) potential. This method is a soft potential analog of an excluded-volume approach. Electrostatic contours on the steric surface illustrate the relatively positive and negative regions of the binding site. The principal intercalation sites, predicted to fit into B-DNA via a tetramer-duplex unit, and the unconstrained dimer-duplex units, obtained in crystal structures, are examined. These contours illustrate the requirements of size, conformation, and net atomic charges necessary for intercalation and optimum binding. Based on the limited space available for intercalation by the presence of the backbone and the maximum base-pair separation of 8.25 Å, an Essential Metabolite Exclusion Hypothesis is presented.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 633-652 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mode of action of many antitumor agents entails the inhibition of nucleic acid synthesis. Because many of the drugs can intercalate, it is assumed that intercalation is an important step in the mechanism of biological activity. As intercalants contain a planar chromophore as an ingredient essential for intercalation, chromophores that should fit into DNA are desired. This is the main theme of this investigation. Binding to DNA of fundamental moieties, protonated pyridine, aniline, phenol, quinone, and 4H-thiopyran-4-one, is studied to determine their optimum placement in DNA. The optimum orientations for each moiety are superimposed to form polyaromatic systems that can intercalate in a manner in which functional groups on these chromophores are oriented as in the moieties themselves. Ideal intercalants proposed contain three and four fused ring system, have protonated ring nitrogen atoms located to maximize the electrostatic interactions with DNA, hydroxy and amino groups that can hydrogen bond to the OII and O5′ phosphate backbone atoms, and carbonyl and sulfur groups in the central position of the ring system to provide variations in the chromophore and to interact with the relatively positive region in the intercalation site. The optimum orientation occurs when the chromophore and the base pairs overlap to the maximum extent. The ideal intercalants are fundamentally of the type:
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An intercalation model of a complex between DNA and a bleomycin fragment (BLMF), consisting of the bithiazole core and an amide and a protonated amino substituent, is presented. The model, which shows a preference for BLMF with the protonated amine in the minor groove and the acetyl terminal inserted into either the minor and major grooves, respectively, agrees with recently obtained nmr data. The selection of sites I and II, which have the smallest unwinding of the three theoretical intercalation sites, is consistent with the experimental unwinding angle of 12°. The bithiazole moiety stacks between two base pairs of the double helix, while the protonated substituent interacts ionically with the negatively charged regions of the backbone in the minor groove of the DNA. The protonated amine also forms an intramolecular hydrogen bond with the carbonyl oxygen of the amide group on the same substituent. Analysis of drug complexes with different base-pair sequences reveal four energetically defined groups. The relative energy of the dimer duplex complexes of BLMF correlates with bleomycin's observed base-sequence specificity upon cleavage. The most stable intercalation complexes form adjacent to the bases cleaved most readily. This correlation suggests a primary connection between intercalation and cleavage. A model cleavage site based on these preliminary theoretical calculations and the experimental observations is proposed. It consists of an intercalation site in a trimer duplex. Pyrimidine(p)purine sequences are the predominant sites for intercalation, and the base adjacent to the site at the (3′) end is cleaved.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 139-158 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Intercalation complexes of daunomicin(+1) with tetramer duplexes in DNA are studied with the theoretically determined intercalation sites (I, -0.4), (II, -0.4), and (III, -1.4). These sites occur with base pairs separated by 6.76 Å for helical angles of 26°, 22°, and 8° about the intercalation site. Site I is preferred, and this is in agreement with experimental unwinding angles. Optimum binding positions and conformations are established, and these are in agreement with experimental results from crystal structures. A systematic procedure is devised to study base-pair and base-sequence specificity, which results in the demonstration that the most stable sequences are mainly ↑BP1, T·A, DAUN, A·T, BP4↓ and ↑BP1, T·A, DAUN, G·C, BP4↓, i.e., with the TpA and CpG (pyrimidine)p(purine) sequences about the intercalation site. These 32 possible sequences are found among the 40 most stable complexes. These theoretical calculations of intercalation complexes with daunomicin(+1) provide the first example in which a drug specifically selects the base pair T·A and prefers it in a particular sequence about the intercalation site. This specificity is in agreement with some experimental results. Problems associated with the interpretation of specificity are discussed in terms of the base, base-pair, and base-sequence resulting from the DNA site and the DNA-drug interactions. T·A specificity is rationalized by noting that the 2′deoxyribo-5′-monophosphate backbone attached to A is slightly more negative than that on the other nucleotides. Hence, a preference exists for binding to the protonated daunosamine (+1) groups. Stereographic projections of daunomycinone and daunomycin(+1) in a bond model and in a space-filling model with steric contours illustrate the results.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The binding positions and relative minimum binding energies are calculated for complexes of 9-aminoacridine, proflavine, N-methylphenanthridinium, and ethidium in theoretically determined intercalation sites in B-DNA (sites I and II) and in unconstrained dimer-duplex sites. The selection of site I in B-DNA by these compounds agrees with the theoretical interpretation of studies of unwinding angles in closed circular DNA in all cases but ethidium, which is predicted to select site II. The most stable binding positions of the acridines and ethidium in unconstrained dimer-duplex units agree with experimental results of intercalation complexes of dinucleoside monophosphate units. Base-pair specificity for Watson-Crick pairing is examined. The energy of an intercalation complex is partitioned into ΔE23, the energy required to open base pairs BP2 and BP3 in B-DNA to a site, and ΔEIn, the energy change when a free molecular intercalates. ΔE23 depends strongly on the base-pair sequence, whereas ΔEIn for the four molecules studied does not. The three most stable sequences contain (pyrimidine)p(purine) units, and this provides a rationale for the exclusive formation of crystals of intercalation complexes with these units. In spite of this selectivity, the distribution of GṁC and AṁT base pairs is equal for these three units and persists as the more unstable sequences are included. Therefore, specificity arises from the interaction between the base pairs and the 2′-deoxyribose 5′-monophosphate backbone for the opening of B-DNA to an intercalation site and not from the interaction between the chromophore and the DNA.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A generalized procedure to generate nucleic acid structures is presented. In this procedure, the bases of a base pair are oriented first for characterization of particular DNA receptor sites. The resultant sites are then used in the study of specific molecule-DNA interactions. For example, intercalation sites, kinked DNA, and twisted and tilted bases are envisioned. Alterations of structures via anti → syn orientations of bases, as well as crankshaft motion about collinear bonds, provide additional conformations without disrupting the overall backbone structure. These approaches to the generation of nucleic acid structures are envisioned as required in studies of the intercalation phenomenon, minor adjustments of DNA to accommodate denaturation, binding of carcinogens to DNA, complex formation of transition metals with DNA, and antitumor agents as ligands. For these base-pair and base orientations, backbone orientations are calculated by the AGNAS technique to yield physically meaningful conformations, namely, those conformations for which nonbonded contacts are favourable. A procedure is presented to generate dimer duplex units that are physically meaningful and to assemble these units into a polynucleotide duplex. Double helices that begin with B-DNA, undergo a transition to one of the above-mentioned receptor sites, and return to B-DNA can be assembled from a catalog of dimer duplexes. Stereographic projections of the various receptor sites already being used to model binding to DNA are presented.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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