S Zanella

Osaka University, Suika, Ōsaka, Japan

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Publications (4)28.19 Total impact

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    ABSTRACT: In this work the lyotropic liquid crystal nematic state of poly(n-hexyl isocyanate) (PHIC)was converted to the cholesteric state by doping with a variety of chiral small molecules and with optically active polyisocyanates. Circular dichroism experiments in dilute isotropic PHIC solutions show that several of the small molecules used as dopants in the Liquid crystal work cause an excess of one helical sense in the otherwise helically dynamically racemic PHIC. Both the helical sense and excess of this sense in dilute solution correlate to the cholesteric sense and twisting power of the same dopants in the concentrated PHIC Liquid crystal solutions. The experimental results are consistent, with a mechanism of cholesteric formation in which the chiral dopants displace slightly the otherwise equal population of the dynamically interconvertable mirror helical senses of the PHIC, which is then further amplified by the Liquid crystal matrix. Direct evidence for the amplification of the intrinsic helical sense excess of the polyisocyanate by the Liquid crystal state could be demonstrated by comparing the cholesteric properties of systems doped with polyisocyanates in which the ratio of the mirror helical senses of the dopants in two compared experiments are identical but in one experiment the helical senses could interconvert and in a separate experiment could not interconvert. The amplification mechanism is driven by the reduction in population of the mobile kinked helical reversals which likely act as "bad neighbors" to the local liquid crystal organization.
    Journal of the American Chemical Society 09/1998; 120:9810-9817. DOI:10.1021/ja981393t · 12.11 Impact Factor
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    ABSTRACT: Conjugation of an anthracycline to a triplex-forming oligonucleotide (TFO) allows delivery of this drug to a specific DNA site, preserving the intercalation geometry of this class of anticancer agents. Conjugate 11, in which the TFO is linked via a hexamethylene bridge to the O-4 on the D ring of the anthraquinone moiety, affords the most stable triple helix, through intercalation of the planar chromophore between DNA bases and binding of both the TFO and the amino sugar to the major and the minor groove respectively.
    Nucleic Acids Research 07/1997; 25(11):2121-8. DOI:10.1093/nar/25.11.2121 · 9.11 Impact Factor
  • G. P. Spada · S. Bonazzi · A. Garbesi · S. Zanella · F. Ciuchi · P. Mariani ·
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    ABSTRACT: 2'-Deoxyguanosine 3':5'-cyclic monophosphate forms in water cholesteric and hexagonal columnar mesophases. The polymorphic behaviour and the structural building blocks of the liquid crystalline phases, as determined by optical microscopy, CD spectroscopy and X-ray diffraction, are comparable to those found with all the deoxyguanylates investigated so far (in particular with deoxuguanosine 5'- and 3'-monophosphate). The present results show that the formation of a stacked array of planar G-tetramers, a necessary condition for the existence of the columnar mesophases, occurs even in the absence of hydrogen bonding groups linking the molecules along the length of the columns.
    Liquid Crystals 03/1997; 22(3):341-348. · 2.49 Impact Factor
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    ABSTRACT: Among a series of unmodified phosphodiester (PO)-oligodeoxynucleotides (PO-ODNs) complementary to some of the human immunodeficiency virus type 1 (HIV-1) regulatory genes, several PO-ODN sequences complementary to the vpr gene (PO-ODNs-a-vpr, where a-vpr is the antisense vpr sequence) emerged as potent inhibitors (at concentrations of 0.8 to 3.3 microM) of HIV-1 multiplication in de novo infected MT-4 cells, while they showed no cytotoxicity for uninfected cells at concentrations up to 100 microM. Unlike phosphorothioate counterparts, PO-ODN-a-vpr sequences were not inhibitory to HIV-2 multiplication in de novo infected C8166 cells and neither prevented the fusion between chronically infected and bystander CD4+ cells nor inhibited the activity of the HIV-1 reverse transcriptase in enzyme assays. Moreover, they were not inhibitory to HIV-1 multiplication in chronically infected cells. Delayed addition experiments showed that PO-ODNs-a-vpr inhibit an event in the HIV-1 replication cycle following adsorption to the host cell, but preceding reverse transcription. Structure-activity relationship studies indicated that the antiviral activity of the test PO-ODN-a-vpr sequences is not related to an antisense mechanism but to the presence, within the active sequences, of contiguous guanine residues. Physical characterization of the test PO-ODNs suggested that the active structure is a tetramer stabilized by G quartets (i.e., four G residues connected by eight hydrogen bonds).
    Antimicrobial Agents and Chemotherapy 10/1996; 40(9):2034-8. · 4.48 Impact Factor