Biology subjects

Sorzano, C. O. S.

Publications and source records attributed to Sorzano, C. O. S..

3 recordsLinked to original sources

bioRxiv2018

Automatic local resolution-based sharpening of cryo-EM maps.

Recent technological advances and computational developments, have allowed the reconstruction of cryo-EM maps at near-atomic resolution structures. Cryo-EM maps benefit significantly of a \"postprocessing\" step, normally referred to as \"sharpening\", that tends to increase signal at medium/high resolution. Here, we propose a new method for local sharpening of volumes generated by cryo-EM. The algorithm (LocalDeblur) is based on a local resolution-guided Wiener restoration approach, does not need any prior atomic model and it avoids artificial structure 1 factor corrections. LocalDeblur is fully automatic and parameter free. We show that the new method significantly and quantitatively improving map quality and interpretability, especially in cases of broad local resolution changes (as is often the case of membrane proteins).

biophysics↗

bioRxiv2018

ENRICH: a fast method to improve the quality of flexible macromolecular reconstructions

Cryo-electron microscopy using single particle analysis requires the computational averaging of thousands of projection images captured from identical macromolecules. However, macromolecules usually present some degree of flexibility showing different conformations. Computational approaches are then required to classify heterogeneous single particle images into homogeneous sets corresponding to different structural states. Nonetheless, sometimes the attainable resolution of reconstructions obtained from these smaller homogeneous sets is compromised because of reduced number of particles or lack of images at certain macromolecular orientations. In these situations, the current solution to improve map resolution is returning to the electron microscope and collect more data. In this work, we present a fast approach to partially overcome this limitation for heterogeneous data sets. Our method is based on deforming and then moving particles between different conformations using an optical flow approach. Particles are then merged into a unique conformation obtaining reconstructions with improved resolution, contrast and signal-to-noise ratio, then, partially circumventing many issues that impact obtaining high quality reconstructions from small data sets. We present experimental results that show clear improvements in the quality of obtained 3D maps, however, there are also limits to this approach, which we discuss in the manuscript.

bioengineering↗

bioRxiv2016

Quantitative analysis of 3D alignment quality: itsimpact on soft-validation, particle pruning andhomogeneity analysis

Single Particle Analysis using cryo-electron microscopy is a structural biology technique to capture the three-dimensional conformation of biological macromolecules. The projection images used to construct the 3D density map are characterized by a very low signal-to-noise ratio to minimize radiation damage in the samples. As a consequence, the 3D alignment process is a challenging and error prone task and this job usually determines the success or failure of the macromolecule reconstruction. In this work, we present a soft-alignment validation approach, which can quantify the alignment precision and accuracy as well as the data homogeneity of the single particles when they are confronted with the resultant reconstructed 3DEM map. We have also applied this method to data homogeneity analysis and particle pruning, improving the data quality and as a consequence the final map resolution.

molecular biology↗