Systematic study of the transfer of amino acids across the water/1,2-dichloroethane interface facilitated by dibenzo-18-crown-6  

作　　者：CHEN Yong, YUAN Yi, ZHANG Meiqin, LI Fei, SUN Peng, GAO Zhao & SHAO YuanhuaState Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China 

出　　处：《Science China Chemistry》2004年第1期24-33,共10页中国科学（化学英文版）

基　　金：This work was supported by the National Natural Science Foundation of China(Grant Nos.20235010,20173058 and 2985111);the Special 985 Project of Peking University.

摘　　要：Facilitated ion transfer reactions of 20 amino acids with dibenzo-18-crown-6 (DB18C6) at the water/1,2-dichloroethane (W/DCE) interfaces supported at the tips of micro- and nano-pipets were investigated systematically using cyclic voltammetry. It was found that there were only 10 amino acids, that is, Leu, Val, lie, Phe, Trp, Met, Ala, Gly, Cys, Gin (in brief), whose protonated forms as cations can give well-defined facilitated ion transfer voltammograms within the potential window, and the reaction pathway was proven to be consistent with the transfer by interfacial complexation/dissociation (TIC/TID) mechanisms. The association constants of DB 18C6 with different amino acids in the DCE (β0), and the kinetic parameters of reaction were evaluated based on the steady-state voltammetry of micro- or nano-pipets, respectively. The experimental results demonstrated that the selectivity of complexation of protonated amino acid by DB18C6 compared with that of alkali metal cations was low, which can be attributed to the vicinal effect arising from steric hindrance introduced by their side group and the steric bulk effect by lipophilic stabilization. Moreover, the association constants and the standard rate constants for different amino acids showed good correlations with their hydrophobicity (π), except Gly and Met, which inferred that the selectivity of such heterogeneous complex reaction for different amino acids with DB18C6, was not only affected by discrimination in binding these ions to the crown ether macro-cycle, but also significantly modified by the ion transfer Gibbs energy which was closely related to the structure of the transferred ions, protonated amino acids.Facilitated ion transfer reactions of 20 amino acids with dibenzo-18-crown-6 (DB18C6) at the water/1,2-dichloroethane (W/DCE) interfaces supported at the tips of micro- and nano-pipets were investigated systematically using cyclic voltammetry. It was found that there were only 10 amino acids, that is, Leu, Val, Ile, Phe, Trp, Met, Ala, Gly, Cys, Gln (in brief), whose protonated forms as cations can give well-defined facilitated ion transfer voltammograms within the potential window, and the reaction pathway was proven to be consistent with the transfer by interfacial complexation/dissociation (TIC/TID) mechanisms. The association constants of DB 18C6 with different amino acids in the DCE (β0), and the kinetic parameters of reaction were evaluated based on the steady-state voltammetry of micro- or nano-pipets, respectively. The experimental results demonstrated that the selectivity of complexation of protonated amino acid by DB18C6 compared with that of alkali metal cations was low, which can be attributed to the vicinal effect arising from steric hindrance introduced by their side group and the steric bulk effect by lipophilic stabilization. Moreover, the association constants and the standard rate constants for different amino acids showed good correlations with their hydrophobicity (π), except Gly and Met, which inferred that the selectivity of such heterogeneous complex reaction for different amino acids with DB18C6, was not only affected by discrimination in binding these ions to the crown ether macro-cycle, but also significantly modified by the ion transfer Gibbs energy which was closely related to the structure of the transferred ions, protonated amino acids.

关 键 词：micro-/nano-pipet  water/1 2-dichloroethane interface  FACILITATED ion transfer  cyclic voltammetry  amino acid. 

分 类 号：O621[理学—有机化学]