Microphase Separation Controlled β-Sheet Crystallization Kinetics in Fibrous Proteins
Microphase Separation Controlled β-Sheet Crystallization Kinetics in Fibrous Proteins
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DOI：
10.1021/ma802481p
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发表时间：
2009-03-24
期刊：
影响因子：
5.5
通讯作者：
Cebe, Peggy
中科院分区：
文献类型：
--
作者：
Hu, Xiao;Lu, Qiang;Cebe, Peggy
丝绸是一种具有多嵌段链结构的天然纤维状蛋白质。因此，它与合成嵌段共聚物有许多相似之处，包括β-折叠结晶可能局限在可结晶嵌段内。本研究报道了丝绸多嵌段纤维状蛋白质中β-折叠晶体的等温结晶动力学机制。诸如为研究合成聚合物晶体生长而建立的阿夫拉米分析等动力学理论，首次被扩展用于研究富含β-折叠的家蚕丝丝素蛋白样品中的蛋白质自组装，采用的方法是时间分辨傅里叶变换红外光谱（FTIR）、差示扫描量热法（DSC）和同步辐射实时广角X射线散射（WAXS）。对于所有方法和结晶温度，阿夫拉米指数n都接近2，这表明丝绸蛋白质中β-折叠晶体的形成不同于在合成聚合物中发现的三维球晶生长。扫描电子显微镜的观察结果支持这样的观点，即蛋白质结构在晶体生长的不同阶段会发生变化，并且在胰凝乳蛋白酶生物降解后呈现出微相分离模式。我们通过类比嵌段共聚物提出了一个模型来解释多嵌段丝素蛋白的结晶：β-折叠的结晶发生在可结晶和不可结晶嵌段相分离所导致的几何限制条件下。这个结晶模型可能广泛适用于具有多嵌段（即可结晶和不可结晶）结构域的其他蛋白质。
Silk is a naturally occurring fibrous protein with a multiblock chain architecture. As Such, it has many similarities with synthetic block copolymers, including the possibility for beta-sheet crystallization restricted within the crystallizable blocks. The mechanism of isothermal crystallization kinetics of beta-sheet crystals in silk multiblock fibrous protein, is reported in this study. Kinetics theories, such as Avrami analysis which was established for studies of synthetic polymer crystal growth, are for the first time extended to investigate protein self-assembly in beta-sheet rich Bombyx mori silk fibroin samples, using time-resolved Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and synchrotron real-time wide-angle X-ray scattering (WAXS). The Avrami exponent, it, was close to 2 for all methods and crystallization temperatures, indicating formation of beta-sheet crystals in silk proteins is different from the 3-D spherulitic crystal growth found in synthetic polymers. Observations by scanning electron microscopy Support the view that the protein structures vary during the different stages of crystal growth, and show a microphase separation pattern after chymotrypsin enzyme biodegradation. We present a model to explain the crystallization of the multiblock silk fibroin protein, by analogy to block copolymers: crystallization of beta-sheets occurs under conditions of geometrical restriction caused by phase separation of the crystallizable and uncrystallizable blocks. This crystallization model could be widely applicable in other proteins with multiblock (i.e., crystallizable and noncrystallizable) domains.