CAJ | 학술논문

采用混合密度泛涵理论中的B3LYP方法,结合4种基组6-31G(d),6-31G(df,p),6-31+G(d)和6-311+G(2d,2p),系统计算了光合反应中心叶绿素的配位体-组氨酸在空气、四碌化碳、四氧呋喃、水和蛋白质模拟环境中的几何结构、电离能、红外光谱及同位素标记谱.计算及分析结果表明:组氨酸分子的几何参数在不同计算基组和介质中略有不同,且C2-N3,N3-C4的键长在空气中最大;同一介质中,增大计算基组和采用扩散函数,均使计算的单点势能和振动频率降低,电离能增加,对应光谱强度增高;而同一计算方法下,介质的电介常数越高,分子的单点势能越低,电离能越小,对应的振动频率减小强度增加;另外,电离能和主要特征峰位及其15N和13C标记谱的计算结果与文献中的实验结果相吻合.所有计算均显示,高基组和施加扩散函数的计算结果与实验更接近.该研究为深入探索叶绿素与组氨酸配位后在光合反应中心的功能与振动光谱特性提供理论参考依据.
채용혼합밀도범함이론중적B3LYP방법,결합4충기조6-31G(d),6-31G(df,p),6-31+G(d)화6-311+G(2d,2p),계통계산료광합반응중심협록소적배위체-조안산재공기、사록화탄、사양부남、수화단백질모의배경중적궤하결구、전리능、홍외광보급동위소표기보.계산급분석결과표명:조안산분자적궤하삼수재불동계산기조화개질중략유불동,차C2-N3,N3-C4적건장재공기중최대;동일개질중,증대계산기조화채용확산함수,균사계산적단점세능화진동빈솔강저,전리능증가,대응광보강도증고;이동일계산방법하,개질적전개상수월고,분자적단점세능월저,전리능월소,대응적진동빈솔감소강도증가;령외,전리능화주요특정봉위급기15N화13C표기보적계산결과여문헌중적실험결과상문합.소유계산균현시,고기조화시가확산함수적계산결과여실험경접근.해연구위심입탐색협록소여조안산배위후재광합반응중심적공능여진동광보특성제공이론삼고의거.
Histidines provide axial ligands to the primary electron donors in photosynthetic reaction centers (RCs) and play an important role in the protein environments of these donors.In this paper the authors present a systematic study of ionization energies and vibrational properties of histidine using hybrid density functional theory (DFT).All calculations were undertaken by using B3LYP method in combination with four basis sets:6-31G(d),6-31G(df,p),6-31+G(d) and 6-311+G(2d,2p) with the aim to investigate how the basis sets influence the calculation results.To investigate solvent effects and gain a detailed understanding of marker bands of histidine,the ionization energies of histidine and the vibrational frequencies of histidine which are unlabeled and 13C,15N,and 2H labeled in the gas phase,CCl4,protein environment,THF and water solution,which span a wide range of dielectric constant,were also calculated.Our results showed that:(1) The main geometry parameters of histidine were impacted by basis sets and mediums,and Ca-N3 and N3-C4 bond of imidazole ring of histidine side chain display the maximum bond lengths in the gas phase;(2) single point energies and frequencies calculated were decreased while ionization energies increased with the increasing level of basis sets and diffuse function applied in the same solvent;(3) with the same computational method,the higher the dielectric constant of the solvent used,the lower the ionization energy and vibrational frequency and the higher the intensity obtained.In addition,calculated ionization energy in the gas phase and marker bands of histidine as well as frequency shift upon 13C and 15N labeling at the computationally more expensive 6-311+G(2d,2p) level are in good agreement with experimental observations available in literatures.All calculations indicated that the results calculated by using higher level basis set with diffuse function were more accurate and closer to the experimental value.In conclusion,the results provide useful information for the further studies of the functional and vibrational properties of ehlorophyll-a ligated to histidine residue in photnsynthetic reaction center.