title: p-Stilbazole moieties as artificial base pairs for photo-cross-linking of DNA duplex.
abstract: In this study, we report a photo-cross-linking reaction between p-stilbazole moieties. p-Stilbazoles were introduced into base-paring positions of complementary DNA strands. The [2 + 2] photocycloaddition reaction occurred rapidly upon light irradiation at 340 nm. Consequently, duplex was cross-linked and highly stabilized after 3 min irradiation. The CD spectrum of the cross-linked duplex indicated that the B-form double-helical structure was not severely distorted. NMR analysis revealed only one conformation of the duplex prior to UV irradiation, whereas two diastereomers were detected after the photo-cross-linking reaction. Before UV irradiation, p-stilbazole can adopt two different stacking modes because of rotation around the single bond between the phenyl and vinyl groups; these conformations cannot be discriminated on the NMR time scale due to rapid interconversion. However, photo-cross-linking fixed the conformation and enabled discrimination both by NMR and HPLC. The artificial base pair of p-methylstilbazolium showed almost the same reactivity as p-stilbazole, indicating that positive charge does not affect the reactivity. When a natural nucleobase was present in the complementary strand opposite p-stilbazole, the duplex was significantly destabilized relative to the duplex with paired p-stilbazole moieties and no photoreaction occurred between p-stilbazole and the nucleobase. The p-stilbazole pair has potential as a "third base pair" for nanomaterials due to its high stability and superb orthogonality.
authors: Graduate School of Engineering, Nagoya University, Nagoya 464-8603, Japan. kashida@nubio.nagoya-u.ac.jp
authors: Hiromu
authors: H
authors: Kashida
authors: Tetsuya
authors: T
authors: Doi
authors: Takumi
authors: T
authors: Sakakibara
authors: Takamitsu
authors: T
authors: Hayashi
authors: Hiroyuki
authors: H
authors: Asanuma
mesh_terms: D020029:Base Pairing; D002851:Chromatography, High Pressure Liquid; D002942:Circular Dichroism; D003432:Cross-Linking Reagents / Q000737:chemistry; D004247:DNA / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D010777:Photochemistry; D011725:Pyridines / Q000737:chemistry*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013343:Styrenes / Q000737:chemistry*
chemical_list: D003432:Cross-Linking Reagents; D011725:Pyridines; D013343:Styrenes; C003347:4-stilbazole; D004247:DNA