While single particle cryo-electron microscopy (cryo-EM) has enabled access to structures of proteins that were previously intractable and, most recently, has done much to inform our understanding of SARS-CoV-2 structure, the technique still has some weaknesses. One of these is loss of information related to sample movement. In a new study, researchers report a novel grid to better support specimens to be imaged, that improves both the quality of images and the efficiency of collection, they say. "[It] is exciting that [these researchers], with one accessible, inexpensive hardware development, will allow all practitioners to acquire better images much more rapidly as soon as the grids become commercially available," write Micah Rapp and Bridget Carragher in a related Perspective. In cryo-EM, each sample is a vitrified layer of protein suspended over a support film on an EM grid. Despite recent advances in the technique, major barriers persist, including loss of the highest resolution information about the specimen through electron beam damage and blurring from sample movement. Katerina Naydenova and colleagues performed an analysis showing that the primary cause of specimen movement during imaging is a buckling of the vitrified ice layer. On the basis of these insights, they created a support film with an optimal thickness that reduces the total movement of the sample. They dubbed their gold sample support "hexAuFoil." It features smaller, more densely packed holes than traditional sample holders. Use of this support system substantially increased data throughput, they say. The negligible particle displacement that results permits extrapolation to "zero exposure" structure factors, revealing features typically lost in cryo-EM structures. This will greatly accelerate structure determination, especially at high resolution, they note.
###
Journal
Science