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Ultrastable gold substrates for electron cryomicroscopy

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Science  12 Dec 2014:
Vol. 346, Issue 6215, pp. 1377-1380
DOI: 10.1126/science.1259530

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Abstract

Despite recent advances, the structures of many proteins cannot be determined by electron cryomicroscopy because the individual proteins move during irradiation. This blurs the images so that they cannot be aligned with each other to calculate a three-dimensional density. Much of this movement stems from instabilities in the carbon substrates used to support frozen samples in the microscope. Here we demonstrate a gold specimen support that nearly eliminates substrate motion during irradiation. This increases the subnanometer image contrast such that α helices of individual proteins are resolved. With this improvement, we determine the structure of apoferritin, a smooth octahedral shell of α-helical subunits that is particularly difficult to solve by electron microscopy. This advance in substrate design will enable the solution of currently intractable protein structures.

A golden era for electron microscopy

Electron microscopy (EM) is an attractive method for determining structures of protein complexes that are difficult to crystallize. Exciting recent developments in electron detectors allow EM structure determination to near atomic resolution. A key impediment to further improvement is that single specimens move during irradiation. Russo and Passmore designed a gold support that moves much less during irradiation than the current support and as a result prevents movement of the protein sample. Using the support they determined the structure of apo-ferritin which, as a spherical shell of α-helices, is particularly challenging to solve by EM.

Science, this issue p. 1377

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