Right-handed double-helix ultrashort DNA yields chiral nematic phases with both right- and left-handed director twist
| Autor: | Fabio Giavazzi, Michi Nakata, Marco Buscaglia, Tommaso Bellini, Noel A. Clark, Roberto Cerbino, Giuliano Zanchetta |
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| Rok vydání: | 2010 |
| Předmět: |
Multidisciplinary
Base Sequence Chemistry Base pair Intermolecular force DNA Oligomer Crystallography chemistry.chemical_compound Oligodeoxyribonucleotides Liquid crystal Phase (matter) Physical Sciences Helix Nucleic Acid Conformation Molecule Spectrophotometry Ultraviolet Chirality (chemistry) Chromatography High Pressure Liquid |
| Zdroj: | Proceedings of the National Academy of Sciences. 107:17497-17502 |
| ISSN: | 1091-6490 0027-8424 |
| Popis: | Concentrated solutions of duplex-forming DNA oligomers organize into various mesophases among which is the nematic ( N ∗ ), 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 ∗ 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 ∗ 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 ∗ 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 ∗ phase at concentration larger than 620 mg/mL. Our findings indicate that in short DNA, the intermolecular double-helical 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. |
| Databáze: | OpenAIRE |
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