Plützer Christian, Hünig Isabel, Kleinermanns Karl, Nir Eyal, de Vries Mattanjah S
Institut für Physikalische Chemie und Elektrochemie I Heinrich Heine Universität Düsseldorf 40225 Düsseldaof, Germany.
Chemphyschem. 2003 Aug 18;4(8):838-42. doi: 10.1002/cphc.200300648.
The vibronic spectrum of the adenine-thymine (A-T) base pair was obtained by one-color resonant two-photon ionization (R2PI) spectroscopy in a free jet of thermally evaporated A and T under conditions favorable for formation of small clusters. The onset of the spectrum at 35,064 cm-1 exhibits a large red shift relative to the pi-pi* origin of 9H-adenine at 36,105 cm-1. The IR-UV spectrum was assigned to cluster structures with HNH...O=C/N...HN hydrogen bonding by comparison with the IR spectra of A and T monomers and with ab initio calculated vibrational spectra of the most stable A-T isomers. The Watson-Crick A-T base pair is not the most stable base-pair structure at different levels of ab initio theory, and its vibrational spectrum is not in agreement with the observed experimental spectrum. Experiments with methylated A and T were performed to further support the structural assignment.
在有利于形成小团簇的条件下，通过热蒸发腺嘌呤（A）和胸腺嘧啶（T）的自由射流中的单色共振双光子电离（R2PI）光谱，获得了腺嘌呤 - 胸腺嘧啶（A - T）碱基对的振动光谱。该光谱在35,064 cm-1处的起始位置相对于9H - 腺嘌呤在36,105 cm-1处的π - π*起始位置呈现出较大的红移。通过与A和T单体的红外光谱以及最稳定的A - T异构体的从头算振动光谱进行比较，将红外 - 紫外光谱归属于具有HNH...O = C/N...HN氢键的团簇结构。在不同水平的从头算理论中，沃森 - 克里克A - T碱基对并非最稳定的碱基对结构，并且其振动光谱与观察到的实验光谱不一致。进行了甲基化A和T的实验以进一步支持结构归属。
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