01443nas a2200205 4500008004100000022001400041245010400055210006900159260001200228300001100240490000800251520078400259653002801043653004001071100001701111700002501128700001701153700001901170856004801189 2009 eng d a1095-865700aDetermination of signal-to-noise ratios and spectral SNRs in cryo-EM low-dose imaging of molecules.0 aDetermination of signaltonoise ratios and spectral SNRs in cryoE c05/2009 a126-320 v1663 a

Attempts to develop efficient classification approaches to the problem of heterogeneity in single-particle reconstruction of macromolecules require phantom data with realistic noise models. We have estimated the signal-to-noise ratios and spectral signal-to-noise ratios for three steps in the electron microscopic image formation from data obtained experimentally. An important result is that structural noise, i.e., the irreproducible component of the object prior to image formation, is substantial, and of the same order of magnitude as the reproducible signal. Based on this result, the noise modeling for testing new classification techniques can be improved.

10aCryoelectron Microscopy10aImage Processing, Computer-Assisted1 aBaxter, Bill1 aGrassucci, Robert, A1 aGao, Haixiao1 aFrank, Joachim uhttp://www.ncbi.nlm.nih.gov/pubmed/1926933201670nas a2200289 4500008004100000022001400041245011900055210006900174260001200243300001200255490000600267520076600273653004001039653002501079653002201104653002401126653001301150653002801163100002201191700001701213700001701230700002701247700002101274700001801295700001901313856004801332 2008 eng d a1750-279900aSPIDER image processing for single-particle reconstruction of biological macromolecules from electron micrographs.0 aSPIDER image processing for singleparticle reconstruction of bio c10/2008 a1941-740 v33 a

This protocol describes the reconstruction of biological molecules from the electron micrographs of single particles. Computation here is performed using the image-processing software SPIDER and can be managed using a graphical user interface, termed the SPIDER Reconstruction Engine. Two approaches are described to obtain an initial reconstruction: random-conical tilt and common lines. Once an existing model is available, reference-based alignment can be used, a procedure that can be iterated. Also described is supervised classification, a method to look for homogeneous subsets when multiple known conformations of the molecule may coexist.

10aImage Processing, Computer-Assisted10aMicroscopy, Electron10aModels, Molecular10aMolecular Structure10aSoftware10aUser-Computer Interface1 aShaikh, Tanvir, R1 aGao, Haixiao1 aBaxter, Bill1 aAsturias, Francisco, J1 aBoisset, Nicolas1 aLeith, ArDean1 aFrank, Joachim uhttp://www.ncbi.nlm.nih.gov/pubmed/19180078