Reactivity in the confinement of self-assembled monolayers:: Chain length effects on the hydrolysis of N-hydroxysuccinimide ester disulfides on gold
Reactivity in the confinement of self-assembled monolayers:: Chain length effects on the hydrolysis of N-hydroxysuccinimide ester disulfides on gold
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DOI：
10.1021/la0343066
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发表时间：
2003-07-08
期刊：
影响因子：
3.9
通讯作者：
Vancso, GJ
中科院分区：
文献类型：
--
作者：
Dordi, B;Schönherr, H;Vancso, GJ
合成了两种N-羟基琥珀酰亚胺（NHS）酯二硫化物16，16 '-二硫代双（N-羟基琥珀酰亚胺基十六烷酸酯）（NHS-C-15）和11，11'-二硫代双（N-羟基琥珀酰亚胺基十一酸酯）（NHS-C-10），并将其作为自组装单分子膜吸附在金表面。这些自组装膜与3，3 '-二硫代双（N-羟基琥珀酰亚胺基丙酸酯）（NHS-C-2）的自组装膜一起被用作模型系统，用于检查影响界面反应动力学的因素。采用掠入射反射傅里叶变换红外（GIR-FTIR）光谱和接触角测量的自组装膜和合并的NHS酯基团的碱催化水解的速率进行了表征。GIR-FTIR光谱表明，NHS-C-2和NHS-C-10的自组装膜经历了伪一级水解，二级速率常数分别为（61 +/- 11）x 10（-2）M-1 s（-1）和（4.5 +/- 0.4）x 10（-2）M-1 s（-1）。NHS-C-15的SAM显示S形行为，在10 mM NaOH水溶液中的半反应时间为1700 +/-20 s。基于接触角数据和Cassie方程的应用确定的速率常数与GIR-FTIR光谱结果非常一致。随着链长的增加构象顺序的增加和随之而来的NHS酯端基包装的改善，如通过GIR-FTIR光谱所见，解释了所观察到的反应性差异。我们的研究结果意味着，在自组装膜的表面反应可以通过精心设计的吸附质结构进行控制。
Two N-hydroxysuccinimide (NHS) ester disulfides, 16,16'-dithiobis(N-hydroxysuccinimidylhexadecanoate) (NHS-C-15) and 11,11'-dithiobis(N-hydroxysuccinimidylundecanoate) (NHS-C-10), were synthesized and adsorbed as self-assembled monolayers (SAMs) on gold surfaces. These SAMs, together with SAMs of 3,3'-dithiobis(N-hydroxysuccinimidylpropionate) (NHS-C-2), were used as model systems for an examination of the factors that affect the kinetics of interfacial reactions. The SAMs and the rate of the base-catalyzed hydrolysis of the incorporated NHS ester groups were characterized by grazing incidence reflection Fourier transform infrared (GIR-FTIR) spectroscopy and contact angle measurements. GIR-FTIR spectroscopy shows that SAMs of NHS-C-2 and NHS-C-10 undergo a pseudo-first-order hydrolysis with second-order rate constants of (61 +/- 11) x 10(-2) M-1 s(-1) and (4.5 +/- 0.4) x 10(-2) M-1 s(-1), respectively. SAMs of NHS-C-15 show a sigmoid behavior with a half reaction time of 1700 +/- 20 s in 10 mM aqueous NaOH. The rate constants determined based on the contact angle data and application of the Cassie equation are in excellent agreement with the GIR-FTIR spectroscopy results. The increase in conformational order with increasing chain length and the concomitant improvement of packing of the NHS ester end groups, as seen by GIR-FTIR spectroscopy, account for the observed differences in reactivity. Our results imply that surface reactions in SAMs can be controlled via careful design of the adsorbate structure.