Single crystals of poly‐L‐lysine
Single crystals of poly‐L‐lysine
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聚-L-赖氨酸单晶
DOI：
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发表时间：
1969
期刊：
影响因子：
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通讯作者：
G. GIANNON1
中科院分区：
文献类型：
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作者：
Jr F. J. PADDEN;H. D. Keith;G. GIANNON1
在二价阴离子存在下，从水溶液中生长出聚L -赖氨酸晶体。其中最稳定的含有HPO =4离子，并通过在聚L -赖氨酸HBr溶液中加入磷酸一氢钠沉淀。在室温或略高于室温的条件下析出α -聚L -赖氨酸HPO4单晶，形成厚度约为150 Å的六方片层。螺旋多肽分子的轴线垂直于片层平面，由于α‐螺旋构象的分子长度约为1100 Å，因此这些螺旋必须折叠。浸没在母液中的六方晶胞的a参数为19.55 Å，赖氨酸侧链几乎完全伸展。将相同的溶液加热到约75°C时产生的沉淀产生β -聚L -赖氨酸HPO4的微晶体。根据x射线粉末衍射图确定的片间间距，初步提出了阴离子在这些晶体中的堆积模式。干燥后，α晶体转变为β结构；讨论了可以预先阻止或扭转过渡的条件。
Crystals of poly‐L‐lysine have been grown from aqueous solution in the presence of divalent anions. The most stable of these incorporate the HPO =4 ion and are precipitated by the addition of sodium monohydrogen phosphate to solutions of poly‐L‐lysine HBr. Precipitation at or slightly above room temperature gives rise to single crystals of α‐poly‐L‐lysine HPO4 in the form of hexagonal lamellae about 150 Å thick. The axes of the helical polypeptide molecules are oriented normal to the planes of the lamellae, and since molecular length is about 1100 Å in the α‐helical conformation, these helices must be folded. The a parameter of the hexagonal unit cell is 19.55 Å for crystals immersed in mother liquor, and the lysine side chains are almost fully extended. Precipitation brought about by heating the same solutions to about 75°C produces micro‐crystals of β‐poly‐L‐lysine HPO4. A mode of packing of the anions in these crystals is proposed tentatively on the basis of an intersheet spacing determined from x‐ray powder diffraction patterns. In general, α crystals are transformed to β structures on drying; conditions under which the transition can either be forestalled or reversed are discussed.