Liu Hongyun, Hu Naifei
Department of Chemistry, Beijing Normal University, Beijing 100875, China.
J Phys Chem B. 2005 May 26;109(20):10464-73. doi: 10.1021/jp0505227.
Negatively charged heme protein hemoglobin (Hb) or myoglobin (Mb) at pH 9.0 and positively charged poly(diallyldimethylammonium) (PDDA) were alternately adsorbed on the surface of CaCO(3) nanoparticles, forming core-shell CaCO(3)-[PDDA/(protein/PDDA)(m)] ([protein-m]) nanoclusters. Oppositely charged [protein-m] and poly(styrenesulfonate) (PSS) were then assembled layer by layer on various solid substrates, forming {[protein-m]/PSS}(n) films. In the meantime, ordinary layer-by-layer films of heme proteins with CaCO(3) nanoparticles ({protein/CaCO(3)}(n)) were also grown on solid surfaces. Transmission electron microscopy (TEM), ultraviolet-visible (UV-vis) spectroscopy, quartz crystal microbalance (QCM), and cyclic voltammetry (CV) were used to characterize the nanoclusters and monitor the growth of the two types of films. Both kinds of protein films assembled on pyrolytic graphite (PG) electrodes exhibited well-defined, nearly reversible CV reduction-oxidation peaks, characteristic of heme Fe(III)/Fe(II) redox couples, and were used to catalyze the electrochemical reduction of hydrogen peroxide. The {[protein-m]/PSS}(n) films demonstrate distinct advantages over the {protein/CaCO(3)}(n) films due to their larger fraction of electroactive proteins, higher catalytic efficiency, and better thermostability. The penetration experiments of the electroactive probe into these films indicate that the {[protein-m]/PSS}(n) nanocluster films possess more pores or channels than the simple {protein/CaCO(3)}(n) films, which may be beneficial to counterion transport in the charge-hopping mechanism and helpful for the diffusion of catalysis substrates into the films. In addition, the electrochemical and biocatalytic activity of protein nanocluster films can be tailored by controlling the number of bilayers assembled on the nanoparticle cores (m) as well as the film thickness or the number of nanocluster layers on the electrodes (n).
在pH为9.0时，带负电荷的血红素蛋白血红蛋白（Hb）或肌红蛋白（Mb）与带正电荷的聚二烯丙基二甲基氯化铵（PDDA）交替吸附在碳酸钙（CaCO₃）纳米颗粒表面，形成核壳结构的CaCO₃-PDDA/(蛋白质/PDDA)ₘ纳米簇。然后，将带相反电荷的[蛋白质-ₘ]和聚苯乙烯磺酸盐（PSS）在各种固体基质上逐层组装，形成{[蛋白质-ₘ]/PSS}ₙ膜。同时，具有碳酸钙纳米颗粒的血红素蛋白普通逐层膜（{蛋白质/CaCO₃}ₙ）也在固体表面生长。使用透射电子显微镜（TEM）、紫外可见（UV-vis）光谱、石英晶体微天平（QCM）和循环伏安法（CV）对纳米簇进行表征，并监测这两种膜的生长情况。在热解石墨（PG）电极上组装的两种蛋白质膜均表现出明确的、近乎可逆的CV还原-氧化峰，这是血红素Fe(III)/Fe(II)氧化还原对的特征，并用于催化过氧化氢的电化学还原。{[蛋白质-ₘ]/PSS}ₙ膜比{蛋白质/CaCO₃}ₙ膜具有明显优势，因为它们具有更大比例的电活性蛋白质、更高的催化效率和更好的热稳定性。电活性探针渗透到这些膜中的实验表明，{[蛋白质-ₘ]/PSS}ₙ纳米簇膜比简单的{蛋白质/CaCO₃}ₙ膜具有更多的孔或通道，这可能有利于电荷跳跃机制中的抗衡离子传输，并有助于催化底物扩散到膜中。此外，通过控制在纳米颗粒核心上组装的双层数（ₘ）以及膜厚度或电极上纳米簇层数（ₙ），可以调整蛋白质纳米簇膜的电化学和生物催化活性。
