We present the proof of concept that a real space tomography approach can be used for the quantification of local ordering in tiny crystals of ferritin. This work is driven by the need for a fundamental understanding of crystal growth of weakly interacting proteins on a molecular level. At present, only tentative ideas exist about interactions in particular in solution and during crystallization. Offering simplicity and controllability the condensation of ferritin molecules from solution was chosen as an ideal system to get insight into the nucleation and crystallisation mechanism that leads to ordered crystals.
The approach involves cryo-fixation of aging stages of ferritin condensation from solution and subsequent three-dimensional scanning transmission electron miscoscopy (STEM) tomography (Fig. 1a). Cryo-STEM tomograms were recorded and analysed to yield the three-dimensional ferritin particle coordinates for the real-space refinement of the structure of ferritin agglomerates. 3D pair correlation functions for ordered nanocrystals of a few hundred ferritin particles reproduce well and up to higher coordination shells the crystal structure that was reported from synchrotron experiments on macrocrystals. The local order within ferritin agglomerates is further refined quantitatively by order parameter mapping with the resolution of a single lattice site based on a data-base correlation technique (Fig. 1b).
To cite this abstract:Lothar Houben, Haim Weissman, Sharon Wolf, Boris Rybtchinski; Direct visualization and quantification of three-dimensional ferritin crystallization on the nanoscale. The 16th European Microscopy Congress, Lyon, France. https://emc-proceedings.com/abstract/direct-visualization-and-quantification-of-three-dimensional-ferritin-crystallization-on-the-nanoscale/. Accessed: July 6, 2020
EMC Abstracts - https://emc-proceedings.com/abstract/direct-visualization-and-quantification-of-three-dimensional-ferritin-crystallization-on-the-nanoscale/