Molecular Arrangement in Two-Dimensional Streptavidin Crystals
Molecular Arrangement in Two-Dimensional Streptavidin Crystals
复制标题
二维链霉亲和素晶体中的分子排列
作者：
Szu‐Wen Wang;A. Robertson;A. Gast
我们研究了二维链霉亲和素晶体在一定pH值范围内空气-−-水界面的分子排列。我们定量了在pH 4.5−6.5时观察到的不同形貌中共存的不同数量的P1、P2和C222晶体。在pH为4.5的条件下，手性针状晶体由具有频繁线缺陷的P1晶体组成。在pH 5附近，较大的手性结构域基本上都是P1与少量P2共存，而在稍高的pH值(接近pH 5.5)时，H型结构域含有4倍于P2/C222混合物共存的P1。这些形状的中间形态显示出中间成分。在pH∼6−7之间，晶体均呈现树枝状X形态，但在分子水平上的排列与低pH值有很大不同。在pH为6时，晶体大部分为P2对称性，但在pH为7及以上时，晶体具有C222对称性。在中等pH值时，P2和C222晶体共存。我们确定了方向和..。
We studied the molecular arrangement of two-dimensional streptavidin crystals at the air−water interface over a range of pH values. We quantified the varying amounts of coexisting P1, P2, and C222 crystals in the different morphologies observed at pH 4.5−6.5. Chiral, needlelike crystals at pH 4.5 consist of P1 crystals with frequent line defects. Larger chiral domains near pH 5 are essentially all P1 coexisting with a small amount of P2, whereas at slightly higher pH values (near pH 5.5), H-shaped domains contain 4 times as much P1 coexisting with a P2/C222 mixture. Morphologies intermediate to these shapes exhibit intermediate compositions. Between pH ∼6−7, crystals all display a characteristic dendritic-X morphology, but arrangement at the molecular level is quite different compared with lower pH values. Crystals are mostly P2 in symmetry near pH 6, but at pH 7 and above, crystals have C222 symmetry. Coexistence of P2 and C222 crystals occurs at intermediate pH values. We determined the orientation and ...