Zane Ariel C, Michelet Christian, Roehrich Adrienne, Emani Prashant S, Drobny Gary P
Department of Chemistry, University of Washington , Box 351700, Seattle, Washington 98195, United States.
Langmuir. 2014 Jun 24;30(24):7152-61. doi: 10.1021/la501444t. Epub 2014 Jun 13.
The use of biomimetic approaches in the production of inorganic nanostructures is of great interest to the scientific and industrial community due to the relatively moderate physical conditions needed. In this vein, taking cues from silaffin proteins used by unicellular diatoms, several studies have identified peptide candidates for the production of silica nanostructures. In the current article, we study intensively one such silica-precipitating peptide, LKα14 (Ac-LKKLLKLLKKLLKL-c), an amphiphilic lysine/leucine repeat peptide that self-organizes into an α-helical secondary structure under appropriate concentration and buffer conditions. The suggested mechanism of precipitation is that the sequestration of hydrophilic lysines on one side of this helix allows interaction with the negatively charged surface of silica nanoparticles, which in turn can aggregate further into larger structures. To investigate the process, we carry out 1D and 2D solid-state NMR (ssNMR) studies on samples with one or two uniformly (13)C- and (15)N-labeled residues to determine the backbone and side-chain chemical shifts. We also further study the dynamics of two leucine residues in the sequence through (13)C spin-lattice relaxation times (T1) to determine the impact of silica coprecipitation on their mobility. Our results confirm the α-helical secondary structure in both the neat and silica-complexed states of the peptide, and the patterns of chemical shift and relaxation time changes between the two states suggest possible mechanisms of self-aggregation and silica precipitation.
由于所需的物理条件相对适中，仿生方法在无机纳米结构生产中的应用引起了科学界和工业界的极大兴趣。在这方面，借鉴单细胞硅藻使用的硅蛋白，多项研究已确定了用于生产二氧化硅纳米结构的候选肽。在本文中，我们深入研究了一种这样的二氧化硅沉淀肽，即LKα14（Ac-LKKLLKLLKKLLKL-c），一种两亲性赖氨酸/亮氨酸重复肽，在适当的浓度和缓冲条件下会自组装成α-螺旋二级结构。推测的沉淀机制是，该螺旋一侧亲水性赖氨酸的螯合允许与二氧化硅纳米颗粒带负电荷的表面相互作用，这反过来又可以进一步聚集形成更大的结构。为了研究这一过程，我们对含有一个或两个均匀（13）C和（15）N标记残基的样品进行了一维和二维固态核磁共振（ssNMR）研究，以确定主链和侧链化学位移。我们还通过（13）C自旋晶格弛豫时间（T1）进一步研究了序列中两个亮氨酸残基的动力学，以确定二氧化硅共沉淀对其流动性的影响。我们的结果证实了该肽在纯态和与二氧化硅复合态下均为α-螺旋二级结构，并且两种状态之间化学位移和弛豫时间变化的模式表明了可能的自聚集和二氧化硅沉淀机制。
