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Analysis and control of chain mobility in protein hydrogels

Rapp, Peter B. and Omar, Ahmad K. and Shen, Jeff J. and Buck, Maren E. and Wang, Zhen-Gang and Tirrell, David A. (2017) Analysis and control of chain mobility in protein hydrogels. Journal of the American Chemical Society, 139 (10). pp. 3796-3804. ISSN 0002-7863. doi:10.1021/jacs.6b13146.

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Coiled-coil domains can direct the assembly of protein block copolymers into physically crosslinked, viscoelastic hydrogels. Here we describe the use of fluorescence recovery after photobleaching (FRAP) to probe chain mobility in reversible hydrogels assembled from engineered proteins bearing terminal coiled-coil domains. We show that chain mobility can be related to the underlying dynamics of the coiled-coil domains by application of a 3-state “hopping” model of chain migration. We further show that genetic programming allows the effective mobility of network chains to be varied 500-fold through modest changes in protein sequence. Destabilization of the coiled-coil domains by site-directed mutagenesis increases the effective diffusivity of probe chains. Conversely, probe mobility is reduced by expanding the hydrophobic surface area of the coiled-coil domains through introduction of the bulky leucine surrogate homoisoleucine. Predictions from the 3-state model imply asymmetric sequential binding of the terminal domains. Brownian Dynamics simulations suggest that binding asymmetry is a general feature of reversible gels, arising from a loss in entropy as chains transition to a conformationally restricted bridged state.

Item Type:Article
Related URLs:
URLURL TypeDescription Information
Rapp, Peter B.0000-0002-9586-2126
Omar, Ahmad K.0000-0002-6404-7612
Wang, Zhen-Gang0000-0002-3361-6114
Tirrell, David A.0000-0003-3175-4596
Additional Information:© 2017 American Chemical Society. Received: December 30, 2016; Published: February 22, 2017. We thank Steven Olsen and the Division of Chemistry and Chemical Engineering Instrument Shop for machining sample holders for the FRAP experiments. We also thank David Koos, Andres Collazo and the Biological Imaging Facility of the Caltech Beckman Institute for training and assistance in operating the confocal microscope. We thank John Bagert, Lawrence Dooling, and Cole DeForest for helpful discussions during the preparation of the manuscript. This work was supported by grant number DMR-1506483 from the Biomaterials Program of the U. S. National Science Foundation. A.K.O. acknowledges support by the National Science Foundation Graduate Research Fellowship under Grant No. DGE-1144469 and an HHMI Gilliam Fellowship. The authors declare no competing financial interest.
Funding AgencyGrant Number
NSF Graduate Research FellowshipDGE-1144469
Howard Hughes Medical Institute (HHMI)UNSPECIFIED
Issue or Number:10
Record Number:CaltechAUTHORS:20170224-091637468
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Official Citation:Analysis and Control of Chain Mobility in Protein Hydrogels Peter B. Rapp, Ahmad K. Omar, Jeff J. Shen, Maren E. Buck, Zhen-Gang Wang, and David A. Tirrell Journal of the American Chemical Society 2017 139 (10), 3796-3804 DOI: 10.1021/jacs.6b13146
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:74522
Deposited By: Tony Diaz
Deposited On:24 Feb 2017 18:02
Last Modified:11 Nov 2021 05:27

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