@article {6326,
	title = {Maturation in action: CryoEM study of a viral capsid caught during expansion.},
	journal = {Structure},
	volume = {20},
	year = {2012},
	month = {2012 Aug 8},
	pages = {1384-90},
	abstract = {<p>Bacteriophage HK97 maturation involves discrete intermediate particle forms, comparable to transitional states in protein folding, before reaching its mature form. The process starts by formation of a metastable prohead, poised for exothermic expansion triggered by DNA packaging. During maturation, the capsid subunit transitions from a strained to a canonical tertiary conformation and this has been postulated to be the driving mechanism for initiating expansion via switching hexameric capsomer architecture from skewed to 6-fold symmetric. We report the subnanometer electron-cryomicroscopy reconstruction of the HK97 first expansion intermediate before any crosslink formation. This form displays 6-fold symmetric hexamers, but capsid subunit tertiary structures exhibit distortions comparable to the prohead forms. We propose that coat subunit strain release acts in synergy with the first crosslinks to drive forward maturation. Finally, we speculate that the energetic features of this transition may result from increased stability of intermediates during maturation via enhanced inter-subunit interactions.</p>
},
	keywords = {Amino Acid Substitution, Bacteriophages, Capsid, Capsid Proteins, Cryoelectron Microscopy, Protein Structure, Protein Subunits, Quaternary, Secondary, Tertiary, Virus Assembly},
	issn = {1878-4186},
	doi = {10.1016/j.str.2012.05.011},
	author = {Veesler, David and Quispe, Joel and Grigorieff, Nikolaus and Potter, Clinton S and Carragher, Bridget and Johnson, John E}
}
@article {6319,
	title = {Movies of ice-embedded particles enhance resolution in electron cryo-microscopy.},
	journal = {Structure},
	volume = {20},
	year = {2012},
	month = {2012 Nov 7},
	pages = {1823-8},
	abstract = {<p>Low-dose images obtained by electron cryo-microscopy (cryo-EM) are often affected by blurring caused by sample motion during electron beam exposure, degrading signal especially at high resolution. We show here that we can align frames of movies, recorded with a direct electron detector during beam exposure of rotavirus double-layered particles, thereby greatly reducing image blurring caused by beam-induced motion and sample stage instabilities. This procedure increases the efficiency of cryo-EM imaging and enhances the resolution obtained in three-dimensional reconstructions of the particle. Using movies in this way is generally applicable to all cryo-EM samples and should also improve the performance of midrange electron microscopes that may have limited mechanical stability and beam coherence.</p>
},
	keywords = {Cryoelectron Microscopy, Ice, Rotavirus},
	issn = {1878-4186},
	doi = {10.1016/j.str.2012.08.026},
	author = {Campbell, Melody G and Cheng, Anchi and Brilot, Axel F and Moeller, Arne and Lyumkis, Dmitry and Veesler, David and Pan, Junhua and Harrison, Stephen C and Potter, Clinton S and Carragher, Bridget and Grigorieff, Nikolaus}
}
