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Anita C Jones

Publications and source records attributed to Anita C Jones.

3 recordsLinked to original sources
PubMed2006

Influence of base dynamics on the conformational properties of DNA: Observation of static conformational states in rigid duplexes at 77 K.

Time-resolved fluorescence of 2-aminopurine-labeled DNA duplexes at 77 K reveals the relationship between base dynamics and the conformational heterogeneity that results in the well-known multiexponential fluorescence decay at room temperature. The conformation that exhibits rapid interbase charge transfer at room temperature is not populated in the frozen duplex at 77 K; this geometry is accessed by thermal motion of the bases, it is not a minimum energy structure of the duplex. Three photophysically distinct conformational states persist in the frozen duplex; these are minimum energy structures and do not interconvert at room temperature on the time scale of the 2-aminopurine excited-state lifetime.

Base Sequence↗
PubMed2005

Time-resolved fluorescence of 2-aminopurine as a probe of base flipping in M.HhaI-DNA complexes.

DNA base flipping is an important mechanism in molecular enzymology, but its study is limited by the lack of an accessible and reliable diagnostic technique. A series of crystalline complexes of a DNA methyltransferase, M.HhaI, and its cognate DNA, in which a fluorescent nucleobase analogue, 2-aminopurine (AP), occupies defined positions with respect the target flipped base, have been prepared and their structures determined at higher than 2 A resolution. From time-resolved fluorescence measurements of these single crystals, we have established that the fluorescence decay function of AP shows a pronounced, characteristic response to base flipping: the loss of the very short (approximately 100 ps) decay component and the large increase in the amplitude of the long (approximately 10 ns) component. When AP is positioned at sites other than the target site, this response is not seen. Most significantly, we have shown that the same clear response is apparent when M.HhaI complexes with DNA in solution, giving an unambiguous signal of base flipping. Analysis of the AP fluorescence decay function reveals conformational heterogeneity in the DNA-enzyme complexes that cannot be discerned from the present X-ray structures.

2-Aminopurine↗