A Metastable Prerequisite for the Growth of Lumazine Synthase Crystals

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• 作者：Olga Gliko ; Nikolaus Neumaier ; Weichun Pan ; Ilka Haase ; Markus Fischer ; Adelbert Bacher ; Sevil Weinkauf ; and Peter G. Vekilov
• 刊名：Journal of the American Chemical Society
• 出版年：2005
• 出版时间：March 16, 2005
• 年：2005
• 卷：127
• 期：10
• 页码：3433 - 3438
• 全文大小：267K
• 年卷期：v.127,no.10(March 16, 2005)
• ISSN：1520-5126

文摘

Dense liquid phases, metastable with respect to a solid phase, form in solutions of proteins andsmall-molecule materials. They have been shown to serve as a prerequisite for the nucleation of crystalsand other ordered solid phases. Here, using crystals of the protein lumazine synthase from Bacillus subtilis,which grow by the generation and spreading of layers, we demonstrate that within a range ofsupersaturations the only mechanism of generation of growth layers involves the association ofsubmicrometer-size droplets of the dense liquid to the crystal surface. The dense liquid is metastable notonly with respect to the crystals, but also with respect to the low-concentration solution: dynamic lightscattering reveals that the droplets' lifetime is limited to several seconds, after which they decay into thelow-concentration solution. The short lifetime does not allow growth to detectable dimensions so that liquid-liquid phase separation is not observed within a range of conditions broader than the one used forcrystallization. If during their lifetime the droplets encounter a crystal surface, they lower their free energynot by decay, but by transformation into crystalline matter, ensuring perfect registry with the substrate.These observations illustrate two novel features of phase transformations in solutions: the existence ofdoubly metastable, short-lifetime dense phases and their crucial role for the growth of an ordered solidphase.