title: Kinetics of end-to-end collision in short single-stranded nucleic acids.
abstract: A novel fluorescence-based method, which entails contact quenching of the long-lived fluorescent state of 2,3-diazabicyclo[2.2.2]-oct-2-ene (DBO), was employed to measure the kinetics of end-to-end collision in short single-stranded oligodeoxyribonucleotides of the type 5'-DBO-(X)n-dG with X = dA, dC, dT, or dU and n = 2 or 4. The fluorophore was covalently attached to the 5' end and dG was introduced as an efficient intrinsic quencher at the 3' terminus. The end-to-end collision rates, which can be directly related to the efficiency of intramolecular fluorescence quenching, ranged from 0.1 to 9.0 x 10(6) s(-1). They were strongly dependent on the strand length, the base sequence, as well as the temperature. Oligonucleotides containing dA in the backbone displayed much slower collision rates and significantly higher positive activation energies than strands composed of pyrimidine bases, suggesting a higher intrinsic rigidity of oligoadenylate. Comparison of the measured collision rates in short single-stranded oligodeoxyribonucleotides with the previously reported kinetics of hairpin formation indicates that the intramolecular collision is significantly faster than the nucleation step of hairpin closing. This is consistent with the configurational diffusion model suggested by Ansari et al. (Ansari, A.; Kuznetsov, S. V.; Shen, Y. Proc.Natl. Acad. Sci. USA 2001, 98, 7771-7776), in which the formation of misfolded loops is thought to slow hairpin formation.
authors.affiliation: Departement Chemie, Universität Basel, Klingelbergstrasse 80, CH-4056 Basel, Switzerland.
authors.forename: Xiaojuan
authors.initials: X
authors.lastname: Wang
authors.forename: Werner M
authors.initials: WM
authors.lastname: Nau
mesh_terms: D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000737:chemistry*; D005453:Fluorescence; D005456:Fluorescent Dyes / Q000138:chemical synthesis / Q000737:chemistry*; D007700:Kinetics; D009838:Oligodeoxyribonucleotides / Q000138:chemical synthesis / Q000737:chemistry*; D009943:Organophosphorus Compounds / Q000138:chemical synthesis / Q000737:chemistry
chemical_list: C484077:2,3-diazabicyclo(2.2.2)oct-2-ene; D019086:Bridged Bicyclo Compounds, Heterocyclic; D005456:Fluorescent Dyes; D009838:Oligodeoxyribonucleotides; D009943:Organophosphorus Compounds; C434331:phosphoramidite