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Single crystals of poly‐ L ‐lysine
Author(s) -
Padden F. J.,
Keith H. D.,
Giani G.
Publication year - 1969
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.1969.360070513
Subject(s) - chemistry , lysine , crystallography , hexagonal crystal system , divalent , precipitation , molecule , aqueous solution , ion , phosphate , liquid crystal , stereochemistry , amino acid , organic chemistry , materials science , biochemistry , physics , meteorology , optoelectronics
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 = 4ion 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 HPO 4 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 HPO 4 . 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.