Accurate Assessment of Mass, Models and Resolution by Small-angle Scattering

Overview

Journal Nature

Specialty Science

Date 2013 Apr 27

PMID 23619693

Citations 429

Authors

Robert P Rambo

John A Tainer

Affiliations

Soon will be listed here.

Abstract

Modern small-angle scattering (SAS) experiments with X-rays or neutrons provide a comprehensive, resolution-limited observation of the thermodynamic state. However, methods for evaluating mass and validating SAS-based models and resolution have been inadequate. Here we define the volume of correlation, Vc, a SAS invariant derived from the scattered intensities that is specific to the structural state of the particle, but independent of concentration and the requirements of a compact, folded particle. We show that Vc defines a ratio, QR, that determines the molecular mass of proteins or RNA ranging from 10 to 1,000 kilodaltons. Furthermore, we propose a statistically robust method for assessing model-data agreements (χ(2)free) akin to cross-validation. Our approach prevents over-fitting of the SAS data and can be used with a newly defined metric, RSAS, for quantitative evaluation of resolution. Together, these metrics (Vc, QR, χ(2)free and RSAS) provide analytical tools for unbiased and accurate macromolecular structural characterizations in solution.

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