Department of Chemistry and Biochemistry, University of California Santa Barbara, CA 93106-9510, USA.
Phys Chem Chem Phys. 2010 Apr 14;12(14):3597-605. doi: 10.1039/b925340h. Epub 2010 Mar 8.
Double resonance spectroscopy of clusters of guanine with aspartic acid reveals geometries similar to patterns exhibited in DNA base pairs. In the spectral region of 32,800 cm(-1) to 35,500 cm(-1) we observe five isomers of guanine-aspartic acid clusters and assign their structures based on IR-UV hole-burning spectra and wave function theory calculations at the MP2/cc-pVDZ and MP2/cc-pVTZ levels. The calculations employed both harmonic and one-dimensional scan anharmonic approximations. Three of the isomers are similar, assigned to structures containing three hydrogen bonds and 9-enolguanine. We assign the fourth isomer to a structure containing a 9-keto tautomer of guanine and forming a triply bonded structure similar to a base pairing interaction. The fifth isomer dissociates with proton transfer upon excitation or ionization. This is the first set of experiments and high-level ab initio calculations of the isolated, microscopic interactions of an amino acid and a nucleobase, the building blocks of nucleic acids and proteins.
嘌呤与天冬氨酸簇的双重共振光谱揭示了与 DNA 碱基对中表现出的模式相似的几何形状。在 32800cm(-1)至 35500cm(-1)的光谱区域内，我们观察到五种嘌呤-天冬氨酸簇的异构体，并根据 IR-UV 光烧孔光谱和在 MP2/cc-pVDZ 和 MP2/cc-pVTZ 水平下的波函数理论计算来确定它们的结构。该计算同时采用了谐波和一维扫描非谐近似。其中三种异构体相似，被分配到含有三个氢键和 9-烯醇鸟嘌呤的结构中。我们将第四种异构体分配到一个含有鸟嘌呤的 9-酮互变异构体并形成类似于碱基配对相互作用的三重键结构的结构中。第五种异构体在激发或电离时通过质子转移而解离。这是一组氨基酸和核苷酸碱基（核酸和蛋白质的构建块）的孤立微观相互作用的第一批实验和高精度从头计算。
