Holland Gregory P, Jenkins Janelle E, Creager Melinda S, Lewis Randolph V, Yarger Jeffery L
Magnetic Resonance Research Center, Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604, USA.
Biomacromolecules. 2008 Feb;9(2):651-7. doi: 10.1021/bm700950u. Epub 2008 Jan 3.
Silks spun from the major (Ma) and minor (Mi) ampullate glands by the spider Nephila clavipes respond to water differently. Specifically, Ma silk supercontracts (shrinks 40-50% in length) while Mi silk does not contract at all when hydrated with water. In the present study, 1H --> 13C cross polarization magic angle spinning (CP-MAS), 13C MAS NMR collected with dipolar decoupling, and two-dimensional wide-line separation spectra are presented on Mi silk in its native and hydrated state and comparisons are made to Ma silk. This combination of NMR data demonstrates that water plasticizes Mi and Ma silk similarly, with an increase in chain dynamics observed in regions containing Gly, Glu, Ser, Tyr, Leu, and a fraction of Ala when the Mi silk is hydrated. Resonances that correspond to the poly(Ala) and poly(Gly Ala) motifs of Ma and Mi silk are predominately rigid indicating that water does not penetrate these beta-sheet domains.
由蜘蛛金蛛（Nephila clavipes）的主壶腹腺（Ma）和次壶腹腺（Mi）纺出的丝对水的反应不同。具体而言，当用水水合时，Ma丝会发生超收缩（长度收缩40 - 50%），而Mi丝根本不会收缩。在本研究中，给出了处于天然状态和水合状态的Mi丝的1H→13C交叉极化魔角旋转（CP - MAS）、带有偶极去耦的13C MAS NMR以及二维宽线分离谱，并与Ma丝进行了比较。这些NMR数据的组合表明，水对Mi丝和Ma丝的增塑作用相似，当Mi丝水合时，在含有甘氨酸（Gly）、谷氨酸（Glu）、丝氨酸（Ser）、酪氨酸（Tyr）、亮氨酸（Leu）和一部分丙氨酸（Ala）的区域观察到链动力学增加。与Ma丝和Mi丝的聚丙氨酸（poly(Ala)）和聚（甘氨酸 - 丙氨酸）（poly(Gly Ala)）基序相对应的共振主要是刚性的，表明水不会渗透到这些β - 折叠结构域中。
