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Crystallography 2018
Structural Chemistry & Crystallography Communication
ISSN: 2470-9905
Page 67
June 04-05, 2018
London, UK
3
rd
Edition of International Conference on
Advanced Spectroscopy,
Crystallography and Applications
in Modern Chemistry
S
mall angle X-ray scattering measurements of dilute,
homogenous particles in solution are resolution limited
measurements of the thermodynamic ensemble. Similar to X-ray
crystallography and electron microscopy, SAXS observations
made at higher resolutions imply a greater detail in the structural
measurement. Here, I present a new approach to understanding
bioSAXS data using two fundamental properties of Information
Theory (namely, theShannonSamplingandNoisy-CodingChannel
theorems). These theorems allow for the error-free recovery of
the SAXS signal, in the form of a real-space, cross-validated pair-
distance, P(r), distribution function. The P(r)-distribution contains
the structural assessment of the thermodynamic ensemble. I
will show that the Information theory framework can be used to
develop structural modeling algorithms for shape determination
and docking. Specifically, I will demonstrate an adaptive
simulated-annealing, density modeling algorithm that targets
the P(r)-distribution using the Kullback-Liebler divergence, an
Information Theory difference metric. The algorithm scales
with resolution. Using a SAXS dataset of a 25 base-pair, double-
stranded DNA, the volumetric model illustrates features of the
major and minor groove as the resolution of the SAXS dataset
increases. Further tests on SAXS of the P4-P6 group I intron RNA
domain reveal the large solvent channels observed in the X-ray
crystal structure. Furthermore, I will show the Information Theory
approach can be used in antibody-antigen studies to uniquely
determine the structure of the complex in the solution state. Our
approach shows that modeling can be made more reliable by
exploiting theorems from Information Theory.
robert.rambo@diamond.ac.ukREAL SPACE MODELING OF SOLUTION-STATE SAXS USING INFORMATION
THEORY
Robert P Rambo
Diamond Light Source, Harwell Science and Innovation Campus, UK
Struct Chem Crystallogr Commun 2018, Volume 4
DOI: 10.21767/2470-9905-C1-006