Application of Neutron Reflectivity for Studies of Biomolecular Structures and Functions at Interfaces

Johs, Alexander; Liang, Liyuan; Gu, Baohua; Ankner, John F.; Wang, Wei

doi:10.1007/978-0-387-09416-8_16

Cited by 1 publication

(2 citation statements)

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“…The structures of buried interfaces can be uniquely probed by neutron reflectometry (NR) at subnanometer resolution. Hydrogen differs significantly from its stable isotope deuterium in its neutron scattering characteristics, which makes NR particularly useful for characterizing biologicalmineral interfaces (16). In this study, we determine for the first time (to our knowledge) the low-resolution structure of OmcA in solution by SAXS, and its arrangement at the hematite (a-Fe 2 O 3 )-water interface by NR.…”

Section: Introductionmentioning

confidence: 95%

“…NR yields a layered profile perpendicular to an interface at subnanometer resolution. In this study, NR was used to reveal the spatial orientation of OmcA bound to the surface to gain structural information about the association of the protein at the mineral interface (16). The specularly reflected intensities were collected over a Q Z range of 5.6 Â 10 À3 -0.3 Å À1 .…”

Section: Neutron Reflectivitymentioning

confidence: 99%

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Characterization of the Decaheme c-Type Cytochrome OmcA in Solution and on Hematite Surfaces by Small Angle X-Ray Scattering and Neutron Reflectometry

Johs¹,

Shi²,

Droubay³

et al. 2010

Biophysical Journal

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The outer membrane protein OmcA is an 85 kDa decaheme c-type cytochrome located on the surface of the dissimilatory metal-reducing bacterium Shewanella oneidensis MR-1. It is assumed to mediate shuttling of electrons to extracellular acceptors that include solid metal oxides such as hematite (alpha-Fe(2)O(3)). No information is yet available concerning OmcA structure in physiologically relevant conditions such as aqueous environments. We purified OmcA and characterized its solution structure by small angle x-ray scattering (SAXS), and its interaction at the hematite-water interface by neutron reflectometry. SAXS showed that OmcA is a monomer that adopts a flat ellipsoidal shape with an overall dimension of 34 x 90 x 65 A(3). To our knowledge, we obtained the first direct evidence that OmcA undergoes a redox state-dependent conformational change in solution whereby reduction decreases the overall length of OmcA by approximately 7 A (the maximum dimension was 96 A for oxidized OmcA, and 89 A for NADH and dithionite-reduced OmcA). OmcA was also found to physically interact with electron shuttle molecules such as flavin mononucleotide, resulting in the formation of high-molecular-weight assemblies. Neutron reflectometry showed that OmcA forms a well-defined monomolecular layer on hematite surfaces, where it assumes an orientation that maximizes its contact area with the mineral surface. These novel insights into the molecular structure of OmcA in solution, and its interaction with insoluble hematite and small organic ligands, demonstrate the fundamental structural bases underlying OmcA's role in mediating redox processes.

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Section: Introductionmentioning

confidence: 95%

Section: Neutron Reflectivitymentioning

confidence: 99%