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Reliably distinguishing protein nanocrystals from amorphous precipitate by means of depolarized dynamic light scattering
Author(s) -
Schubert Robin,
Meyer Arne,
Dierks Karsten,
Kapis Svetlana,
Reimer Rudolph,
Einspahr Howard,
Perbandt Markus,
Betzel Christian
Publication year - 2015
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/s1600576715014740
Subject(s) - crystallization , nanocrystal , chemical physics , macromolecule , materials science , amorphous solid , nanocrystalline material , protein crystallization , diffraction , crystallography , scattering , crystal (programming language) , nucleation , light scattering , excited state , nanotechnology , chemical engineering , chemistry , optics , atomic physics , physics , biochemistry , programming language , organic chemistry , computer science , engineering
Crystallization of biological macromolecules such as proteins implies several prerequisites, for example, the presence of one or more initial nuclei, sufficient amounts of the crystallizing substance and the chemical potential to provide the free energy needed to force the process. The initiation of a crystallization process itself is a stochastic event, forming symmetrically assembled nuclei over kinetically preferred protein‐dense liquid clusters. The presence of a spatial repetitive orientation of macromolecules in the early stages of the crystallization process has so far proved undetectable. However, early identification of the occurrences of unit cells is the key to nanocrystal detection. The optical properties of a crystal lattice offer a potential signal with which to detect whether a transition from disordered to ordered particles occurs, one that has so far not been tested in nanocrystalline applications. The ability of a lattice to depolarize laser light depends on the different refractive indices along different crystal axes. In this study a unique experimental setup is used to detect nanocrystal formation by application of depolarized scattered light. The results demonstrate the successful detection of nano‐sized protein crystals at early stages of crystal growth, allowing an effective differentiation between protein‐dense liquid cluster formation and ordered nanocrystals. The results are further verified by complementary methods like X‐ray powder diffraction, second harmonic generation, ultraviolet two‐photon excited fluorescence and scanning electron microscopy.