An encryption\u2013decryption framework to validating single-particle imaging

Zhou Shen,Kartik Ayyer,N Duane Loh,Colin Zhi Wei Teo

doi:10.1038/s41598-020-79589-0

Abstract

We propose an encryption–decryption framework for validating diffraction intensity volumes reconstructed using single-particle imaging (SPI) with X-ray free-electron lasers (XFELs) when the ground truth volume is absent. This conceptual framework exploits each reconstructed volumes’ ability to decipher latent variables (e.g. orientations) of unseen sentinel diffraction patterns. Using this framework, we quantify novel measures of orientation disconcurrence, inconsistency, and disagreement between the decryptions by two independently reconstructed volumes. We also study how these measures can be used to define data sufficiency and its relation to spatial resolution, and the practical consequences of focusing XFEL pulses to smaller foci. This conceptual framework overcomes critical ambiguities in using Fourier Shell Correlation (FSC) as a validation measure for SPI. Finally, we show how this encryption-decryption framework naturally leads to an information-theoretic reformulation of the resolving power of XFEL-SPI, which we hope will lead to principled frameworks for experiment and instrument design.

Highlights

We propose an encryption–decryption framework for validating diffraction intensity volumes reconstructed using single-particle imaging (SPI) with X-ray free-electron lasers (XFELs) when the ground truth volume is absent
Collected diffraction patterns are identified and analyzed in various ways including: determining the 3D structures that most likely produced the ensemble of SPI p atterns[13], or studying the range of 3D morphologies spanned by the XFEL scatterers[14,15,16]
To circumvent some of these issues with Fourier Shell Correlation (FSC), we propose examining the source of correlations between two independently reconstructed volumes: the ‘disconcurrence’, inconsistency, and agreement between how these volumes orient individual patterns

Summary

Introduction

We propose an encryption–decryption framework for validating diffraction intensity volumes reconstructed using single-particle imaging (SPI) with X-ray free-electron lasers (XFELs) when the ground truth volume is absent. This conceptual framework exploits each reconstructed volumes’ ability to decipher latent variables (e.g. orientations) of unseen sentinel diffraction patterns. We study how these measures can be used to define data sufficiency and its relation to spatial resolution, and the practical consequences of focusing XFEL pulses to smaller foci This conceptual framework overcomes critical ambiguities in using Fourier Shell Correlation (FSC) as a validation measure for SPI. Collected diffraction patterns are identified and analyzed in various ways including: determining the 3D structures that most likely produced the ensemble of SPI p atterns[13], or studying the range of 3D morphologies spanned by the XFEL scatterers[14,15,16]

Methods

Results

Conclusion