Ion-Specific Control of the Self-Assembly Dynamics of a Nanostructured Protein Lattice

Journal Article · Wed Dec 17 00:00:00 EST 2014 · ACS Nano

DOI:https://doi.org/10.1021/nn502992x· OSTI ID:1168700

Rad, Behzad; Haxton, Thomas K.; Shon, Albert ^[1]; Shin, Seong-Ho ^[2]; Whitelam, Stephen; Ajo-Franklin, Caroline M.

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1. Department of Chemical and Biomolecular Engineering, UC Berkeley, Berkeley, California 94720-1462, United States
2. Department of Chemistry, UC Berkeley, Berkeley, California 94720-1460, United States

Self-assembling proteins offer a potential means of creating nanostructures with complex structure and function. However, using self-assembly to create nanostructures with long-range order whose size is tunable is challenging, because the kinetics and thermodynamics of protein interactions depend sensitively on solution conditions. Here we systematically investigate the impact of varying solution conditions on the self-assembly of SbpA, a surface-layer protein from Lysinibacillus sphaericus that forms two-dimensional nanosheets. Using high-throughput light scattering measurements, we mapped out diagrams that reveal the relative yield of self-assembly of nanosheets over a wide range of concentrations of SbpA and Ca²⁺. These diagrams revealed a localized region of optimum yield of nanosheets at intermediate Ca²⁺ concentration. Replacement of Mg²⁺ or Ba²⁺ for Ca²⁺ indicates that Ca²⁺ acts both as a specific ion that is required to induce self-assembly and as a general divalent cation. In addition, we use competitive titration experiments to find that 5 Ca²⁺ bind to SbpA with an affinity of 67.1 ± 0.3 μM. Finally, we show via modeling that nanosheet assembly occurs by growth from a negligibly small critical nucleus. We also chart the dynamics of nanosheet size over a variety of conditions. In conclusion, our results demonstrate control of the dynamics and size of the self-assembly of a nanostructured lattice, the constituents of which are one of a class of building blocks able to form novel hybrid nanomaterials.

• Research Organization: Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: AC02-05CH11231; R01GM105404
• OSTI ID: 1168700
• Alternate ID(s): OSTI ID: 1257359
• Journal Information: ACS Nano, Journal Name: ACS Nano Vol. 9 Journal Issue: 1; ISSN 1936-0851
• Publisher: American Chemical Society
• Country of Publication: United States
• Language: English

Related Subjects

77 NANOSCIENCE AND NANOTECHNOLOGY
protein interactions
biomaterials
nanostructures
self-assembly dynamics
Ca2+ binding