Liu Ying-Xin, Wang Xiu-Juan, Lu Jie, Ching Chi-Bun
School of Chemical and Biomedical Engineering, Nanyang Technological University, 62 Nanyang Drive, Singapore 637459.
J Phys Chem B. 2007 Dec 20;111(50):13971-8. doi: 10.1021/jp0741612. Epub 2007 Nov 29.
In this study, the influence of some factors on the heterogeneous nucleation of hen egg-white lysozyme (E.C. 3.2.1.17) on a series of chemically modified surfaces has been investigated. Microbatch crystallization experiments were conducted on the microscope glass slides that were treated with poly-L-glutamic acid (PLG), poly(2-hydroxyethyl methacrylate) (P2HEMA), poly(methyl methacrylate) (PMMA), poly(4-vinyl pyridine) (P4VP), and (3-aminopropyl)triethoxysilane (APTES). An optical microscope with a heating/cooling stage was employed to measure the induction time of heterogeneous nucleation. The surface topography and roughness were characterized by atomic force microscopy. Contact angles for crystallization solution on the investigated surfaces were measured by a contact angle meter. From the theoretical analysis, the energetic barrier to heterogeneous nucleation was found to increase at higher contact angles and to decrease at higher roughness. Experimentally, a qualitative increase of the induction time of the heterogeneous nucleation on P2HEMA, APTES, and PMMA surfaces with the contact angle was observed. Such surfaces as P2HEMA, PLG, and APTES, which were of higher roughness, were shown to promote the heterogeneous nucleation. In addition, the surface with specific topography is expected to increase the possibility of the formation of a critical nucleus. Finally, the P4VP surface appeared to suppress the heterogeneous nucleation as a result of the electrostatic interaction between the lysozyme and P4VP molecules.
在本研究中，已对一些因素对蛋清溶菌酶（E.C. 3.2.1.17）在一系列化学修饰表面上的异质成核的影响进行了研究。在经聚-L-谷氨酸（PLG）、聚（甲基丙烯酸2-羟乙酯）（P2HEMA）、聚甲基丙烯酸甲酯（PMMA）、聚（4-乙烯基吡啶）（P4VP）和（3-氨丙基）三乙氧基硅烷（APTES）处理的显微镜载玻片上进行了微量分批结晶实验。使用带有加热/冷却台的光学显微镜来测量异质成核的诱导时间。通过原子力显微镜对表面形貌和粗糙度进行了表征。用接触角测量仪测量了所研究表面上结晶溶液的接触角。从理论分析可知，异质成核的能量势垒在较高接触角时增加，在较高粗糙度时降低。实验上，观察到在P2HEMA、APTES和PMMA表面上异质成核的诱导时间随接触角有定性增加。诸如P2HEMA、PLG和APTES等具有较高粗糙度的表面被证明能促进异质成核。此外，具有特定形貌的表面预计会增加形成临界核的可能性。最后，由于溶菌酶与P4VP分子之间的静电相互作用，P4VP表面似乎抑制了异质成核。
