核酸碱基自组装膜表面电子转移性质研究

Study on Electron Transfer Across Nucleobases Terminated Surface Assembly

巯基丙酸(MPA)、Mg2+以及含不同碱基的核苷酸(NTMP)(鸟苷酸GMP、腺苷酸AMP、尿苷酸UMP、胞苷酸CMP)逐步吸附到金电极上,制备末端为核酸碱基的组装膜,利用循环伏安(CV)、计时安培(CA)以及电化学交流阻抗技术(EIS)进行表征。结果表明,电子传递速率遵循以下顺序逐渐降低:GMP/Mg2+/MPA/Au>AMP/Mg2+/MPA/Au>UMP/Mg2+/MPA/Au>CMP/Mg2+/MPA/Au,量子化学计算多层膜组合体Mg-NTMP的能级差(ΔEgap=ELUMO-EHOMO)以一定的顺序增加:ΔEMg-GMP(0.89 eV)<ΔEMg-AMP(1.40 eV)<ΔEMg-UMP(1.57 eV)<ΔEMg-CMP(1.64 eV)。这说明末端为核酸碱基的多层组装膜表面的电子转移过程中,组合体Mg-NTMP的能级差ΔEgap决定电子穿越核酸碱基的速率。

3-Mercaptopropionic acid （MPA）, Mg2＋ and nucleotide monophosphate （NTMP） （including guanosine, adenosine, cytidine, uridine-5＇-monophosphate, and abbreviations were GMP, AMP, CMP, UMP respectively） were adsorbed onto Au substrates stepwise to form nucleobases terminated surface. Electron transfer （ET） process across the NTMP/Mg2＋/MPA/Au muhilayer assembly was studied and the ET kinetics were determined using electrochemical methods including cyclic vohammetry （CV）, chronoamperometry （CA） and electrochemical impedance spectroscopy （EIS）. The experimental results obtained from electro- chemistry showed that the rate of ET kinetics decreased in the order： GMP/MgE＋/MPA/Au〉AMP/Mg2＋/ MPA/Au 〉 UMP/MgE＋/MPA/Au 〉 CMP/Mg2＋/MPA/Au. And the calculated energy gaps （ ΔEgap = ELUMO -- EHOMO） of their corresponding Mg-NTMP complexes motif increased in the order：ΔEMg-GMP （0. 89 eV ） 〈 ΔEMg-AMP（ 1.40 eV） 〈ΔEMg-UUp（ 1.57 eV） 〈ΔEMg-cMp（ 1.64 eV）, which suggested that eomplexation of Mg with the NTMP, and their corresponding AEgap may play important role in their ET process across the nucleobases terminated muhilayer assembly.