Four-stranded aggregates of oligodeoxyguanylates forming lyotropic liquid crystals: a study by circular dichroism, optical microscopy, and x-ray diffraction

Bonazzi, Stefania; Capobianco, Massimo L.; Morais, Monica Mirande De; Garbesi, Anna; Gottarelli, Giovanni; Mariani, Paolo; Bossi, M. G. Ponzi; Spada, Gian Piero; Tondelli, Luisa

doi:10.1021/ja00015a040

Cited by 92 publications

(81 citation statements)

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“…[104,112] Ein Calix [4] [108,114] In Wasser wird die hierarchische Selbstorganisation von Desoxyguanosin-Oligomeren durch die Bildung wasserstoffverbrückter cyclischer Tetramere ausgelöst, die sich zu einer kolumnaren Über-struktur stapeln. Oberhalb einer bestimmten Konzentration bilden sich lyotrope LC-Phasen, die sich bei noch höheren Konzentrationen in eine cholesterische Phase umwandeln.…”

Section: Chiralitätsverstärkung Bei Anderen Scheibenför-migen Verbindunclassified

“…Oberhalb einer bestimmten Konzentration bilden sich lyotrope LC-Phasen, die sich bei noch höheren Konzentrationen in eine cholesterische Phase umwandeln. [114] Bei einem ähnlichen Ansatz wurden lipophile Guanosinkomplexe in unpolaren Lösungsmitteln untersucht. In Gegenwart von Alkalimetallionen bildeten die Guanosinderivate polymere Röhrenstrukturen, [108] über eine mögliche Chiralitätsverstärkung für diese Aggregate ist aber nichts bekannt.…”

Section: Chiralitätsverstärkung Bei Anderen Scheibenför-migen Verbindunclassified

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Chiralitätsverstärkung in dynamischen supramolekularen Aggregaten

2007

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Die Frage nach dem Ursprung der Chiralität in biologischen Systemen löste die Suche nach nichtlinearen Effekten in der Katalyse aus, und man suchte nach Wegen, um ausgehend von minimalen Enantiomerenüberschüssen optisch reine Verbindungen zu erhalten. Intensiv erforscht wurde bereits die Chiralitätsverstärkung in Polymeren als Folge kooperativer Prozesse. Vor zehn Jahren wurde dieser Effekt erstmals auch für nichtkovalente, dynamische supramolekulare Systeme nachgewiesen. Seitdem hat sich gezeigt, dass auch für niedermolekulare Verbindungen eine Chiralitätsverstärkung möglich ist, wenn nichtkovalente Wechselwirkungen wie Wasserstoffbrücken, hydrophobe und π‐π‐Stapelwechselwirkungen aufeinander abgestimmt werden. Wir fassen die Resultate der letzten zehn Jahre zusammen und leiten daraus einige allgemeine Regeln ab. Eine Chiralitätsverstärkung kann zwar immer noch nicht sicher vorhergesagt werden, essenziell sind aber wohl ein ausgewogenes Verhältnis der beteiligten Wechselwirkungen und oftmals die Bildung eines intrinsisch chiralen Objekts sowie kooperative Aggregationsprozesse.

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Section: Chiralitätsverstärkung Bei Anderen Scheibenför-migen Verbindunclassified

Chiralitätsverstärkung in dynamischen supramolekularen Aggregaten

2007

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“…Experiments indicate that there is no simple rule connecting the handedness of the individual helices to that of the phase. There are examples of right-handed (RH) helices yielding RH chiral nematic (N Ã ) phases, as in the case of the four stranded guanosine columnar aggregates (G-wires) formed by homooligomeric chains with 3 or more guanosines (5); left-handed (LH) helices yielding LH N Ã phases, as in the case of G-wires formed by the aggregation of the single nucleotide guanosine-monophosphate (5); RH helices yielding LH N Ã phases, such as long DNA double strands (6, 7), filamentous viruses (810), and G-wires made of diguanosines (5).…”

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Right-handed double-helix ultrashort DNA yields chiral nematic phases with both right- and left-handed director twist

Zanchetta

Giavazzi

Nakata

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

103

118

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Concentrated solutions of duplex-forming DNA oligomers organize into various mesophases among which is the nematic (N Ã ), which exhibits a macroscopic chiral helical precession of molecular orientation because of the chirality of the DNA molecule. Using a quantitative analysis of the transmission spectra in polarized optical microscopy, we have determined the handedness and pitch of this chiral nematic helix for a large number of sequences ranging from 8 to 20 bases. The B-DNA molecule exhibits a right-handed molecular double-helix structure that, for long molecules, always yields N Ã phases with left-handed pitch in the μm range. We report here that ultrashort oligomeric duplexes show an extremely diverse behavior, with both left-and right-handed N Ã helices and pitches ranging from macroscopic down to 0.3 μm. The behavior depends on the length and the sequence of the oligomers, and on the nature of the end-to-end interactions between helices. In particular, the N Ã handedness strongly correlates with the oligomer length and concentration. Right-handed phases are found only for oligomers shorter than 14 base pairs, and for the sequences having the transition to the N Ã phase at concentration larger than 620 mg∕mL. Our findings indicate that in short DNA, the intermolecular doublehelical interactions switch the preferred liquid crystal handedness when the columns of stacked duplexes are forced at high concentrations to separations comparable to the DNA double-helix pitch, a regime still to be theoretically described.cholesteric | RNA U nderstanding how the physicochemical details of macromolecules affect their interactions and their self-ordering properties represents one of the major challenges in the physics of soft and biological matter. In particular, because most of the biologically relevant molecules are chiral-i.e., they lack mirror symmetry-the relevant biointeractions are typically highly sensitive to the molecular handedness. One important effect of chiral interactions is the propagation of chirality from the molecular structure to the supramolecular assemblies such as aggregates or ordered phases. Often, in this phenomenon, minor molecular modifications are amplified to produce remarkable changes in the macroscopic ordering, as for DNA supercoiling and its biological role (1). The propagation of chirality has been studied in various systems, including thermotropic liquid crystals (LCs) and lyotropic assemblies of viruses, DNA, polymers, and dye aggregates. Despite the generality of the phenomenon, its understanding is still poor. Predicting, only on the basis of the molecular structure, the most basic parity of chiral LC ordering, the rightvs. left-handedness, is still a challenge (2-4). One would expect the problem to become easier when restricted to molecular structures with a clean cylindrical shape decorated with regular helical structures and charges, such as DNA, G-quartets, and filamentous viruses. However, even in this limited frame, experimental and theoretical results appear difficult to fi...

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“…The cholesteric phase formed by B-DNA (a right-handed double helix) in water is left-handed at room temperature. Right-handed G-wires (a four-stranded right-handed helix as determined by CD spectroscopy 24,35 and single-crystal X-ray diffraction 44 ) give instead righthanded cholesterics at room temperature. 45 Inspection of X-ray data does not show substantial difference in the inclination of the sugar-phosphate thread in both cases (see Figure 7.11).…”

Section: 39mentioning

confidence: 99%