title: Absolute Intramolecular Distance Measurements with Angstrom-Resolution Using Anomalous Small-Angle X-ray Scattering.
abstract: Accurate determination of molecular distances is fundamental to understanding the structure, dynamics, and conformational ensembles of biological macromolecules. Here we present a method to determine the full distance distribution between small (∼7 Å radius) gold labels attached to macromolecules with very high-precision (≤1 Å) and on an absolute distance scale. Our method uses anomalous small-angle X-ray scattering close to a gold absorption edge to separate the gold-gold interference pattern from other scattering contributions. Results for 10-30 bp DNA constructs achieve excellent signal-to-noise and are in good agreement with previous results obtained by single-energy SAXS measurements without requiring the preparation and measurement of single labeled and unlabeled samples. The use of small gold labels in combination with ASAXS read out provides an attractive approach to determining molecular distance distributions that will be applicable to a broad range of macromolecular systems.
authors.affiliation: Department of Physics, Nanosystems Initiative Munich, and Center for Nanoscience, LMU Munich , Amalienstrasse 54, 80799 Munich, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Zettl
authors.affiliation: Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, United States.
authors.forename: Rebecca S
authors.initials: RS
authors.lastname: Mathew
authors.affiliation: X-ray Science Division, Argonne National Laboratory , Argonne, Illinois 60439, United States.
authors.forename: Sönke
authors.initials: S
authors.lastname: Seifert
authors.forename: Sebastian
authors.initials: S
authors.lastname: Doniach
authors.forename: Pehr A B
authors.initials: PA
authors.lastname: Harbury
authors.affiliation: Department of Physics, Nanosystems Initiative Munich, and Center for Nanoscience, LMU Munich , Amalienstrasse 54, 80799 Munich, Germany.
authors.forename: Jan
authors.initials: J
authors.lastname: Lipfert
mesh_terms: D004247:DNA / Q000737:chemistry*; D006046:Gold; D008968:Molecular Conformation; D053838:Scattering, Small Angle; D014961:X-Ray Diffraction
chemical_list: D006046:Gold; D004247:DNA
keywords: DNA; Intramolecular distances; SAXS; anomalous small-angle X-ray scattering; gold nanocrystals; molecular ruler