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Microscope detection options for colorless protein crystals grown in lipidic cubic phases
Author(s) -
Nollert Peter
Publication year - 2003
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s0021889803013724
Subject(s) - nucleation , polarization microscopy , protein crystallization , crystallization , optical microscope , materials science , crystallography , phase (matter) , microscopy , crystal (programming language) , cubic crystal system , isotropy , microscope , polarized light microscopy , isotropic solid , membrane , optics , chemistry , scanning electron microscope , physics , organic chemistry , computer science , composite material , programming language , biochemistry
The use of lipidic cubic phases as crystal nucleation and growth matrices is becoming popular and has yielded crystals of soluble and membrane proteins. So far, all of the membrane proteins crystallized by this method have been colored. This feature has facilitated the detection of the often encountered microcrystals in initial screening rounds. Indeed, small colorless protein crystals have poor optical contrast as a result of the small differences in refractive index of the protein crystal and the surrounding lipidic cubic phase. While a perfect preparation of a lipidic cubic phase is transparent and optically isotropic, in a crystallization setup it frequently disguises crystals due to cracks, inclusions, surface distortions and phase boundaries. Here, several specialized microscopic techniques and illumination conditions are compared and it is found that sufficient contrast is generated by cross polarization microscopy and by Hoffman modulation contrast microscopy for the detection of colorless protein crystals.