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Interactions between isoalloxazine and o-aminobenzoate in o-aminobenzoate−d-amino acid oxidase complex. Molecular dynamics and molecular orbital studies
Journal of Photochemistry and Photobiology A: Chemistry ( IF 4.3 ) Pub Date : 2020-12-07 , DOI: 10.1016/j.jphotochem.2020.113090
Arthit Nueangaudom , Somsak Pianwanit , Haruhiko Tamaoki , Yasuzo Nishina , Fumio Tanaka , Seiji Taniguchi , Haik Chosrowjan

Molecular interactions between o-aminobenzoate (oAB) and isoallxazine (Iso) in o-aminobenzoate - d-amino acid oxidase complex (ODC) were studied by means of molecular dynamics simulation (MDS) and molecular orbital (MO) method. The distances between oAB and Iso were 0.60 in subunit A (Sub A) and 0.58 nm in Sub B. Four of six heteroatoms of Iso ring formed hydrogen bonding (HB) with nearby amino acids. The oxygen atom and nitrogen atom of oAB also formed HB with amino acids. The ODC displays a broad absorption band around 570 nm, which is considered to be charge transfer (CT) band between oAB and Iso in the complex. The ODC displayed fluorescence at around 520 nm, which is different from that of DAAO (emission peak at 535 nm) without oAB. The emission is from a local excited state (LE) without CT interaction. The CT interaction was studied by a semi-empirical molecular orbital (MO) method, using the structures of oAB and Iso obtained by MDS. The CT state did not form in the ground state of Iso, but formed in the excited state of Iso (Iso*), when the both cannot move appreciably from the MDS structures. The CT states formed both in the oAB – Iso and oAB – Iso* (excited state of Iso) systems when the both molecules can move so as to attain the minimum energy state. It is concluded that a part of oAB could move to form CT complex with Iso in the ground state, which displays the CT absorption band, but others could not move in the protein without CT interaction, which displays the fluorescence.



中文翻译:

异别恶嗪和氨基苯甲酸酯在氨基苯甲酸酯-d-氨基酸氧化酶复合物中的相互作用。分子动力学和分子轨道研究

邻氨基苯甲酸酯中邻氨基苯甲酸酯(oAB)和异恶嗪(Iso)之间的分子相互作用-d通过分子动力学模拟(MDS)和分子轨道(MO)方法研究了β-氨基酸氧化酶复合物(ODC)。oAB和Iso之间的距离在A亚基(Sub A)中为0.60,在Sub B中为0.58nm。Iso环的六个杂原子中的四个与附近的氨基酸形成氢键(HB)。oAB的氧原子和氮原子也与氨基酸形成HB。ODC在570 nm附近显示一个宽吸收带,这被认为是复合物中oAB和Iso之间的电荷转移(CT)带。ODC在520 nm附近显示荧光,这与没有oAB的DAAO(在535 nm处的发射峰)不同。发射来自没有CT相互作用的局部激发态(LE)。CT相互作用是通过半经验分子轨道(MO)方法研究的,使用了MDS获得的oAB和Iso的结构。CT态不是在Iso的基态中形成的,而是在Iso(Iso *)的激发态中形成的,这时两者都不能从MDS结构中明显地移动出来。当两个分子都可以移动以获得最小能量状态时,CT态在oAB – Iso和oAB – Iso *(Iso的激发态)系统中均形成。结论是,oAB的一部分可以与处于基态的Iso形成CT络合物,显示出CT吸收带,而其他分子在没有CT相互作用的情况下不能在蛋白质中移动,从而显示出荧光。当两个分子都可以移动以获得最小能量状态时,CT态在oAB – Iso和oAB – Iso *(Iso的激发态)系统中均形成。结论是,oAB的一部分可以与处于基态的Iso形成CT络合物,显示出CT吸收带,而其他分子在没有CT相互作用的情况下不能在蛋白质中移动,从而显示出荧光。当两个分子都可以移动以获得最小能量状态时,CT态在oAB – Iso和oAB – Iso *(Iso的激发态)系统中均形成。结论是,oAB的一部分可以与处于基态的Iso形成CT络合物,显示出CT吸收带,而其他分子在没有CT相互作用的情况下不能在蛋白质中移动,从而显示出荧光。

更新日期:2021-01-10
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