Better explicating the strengths and shortcomings of these models will help refine projections and improve transparency in the years ahead.
Image credit: Witsawat.S.
Edited* by L. B. Freund, University of Illinois at Urbana–Champaign, Urbana, IL, and approved May 23, 2014 (received for review February 18, 2014)
Significance
Ferroelectricity has long been speculated to have important biological functions, although its very existence in biology has never been firmly established. Here, we present, to our knowledge, the first macroscopic observation of ferroelectric switching in a biological system, and we elucidate the origin and mechanism underpinning ferroelectric switching of elastin. It is discovered that the polarization in elastin is intrinsic at the monomer level, analogous to the unit cell level polarization in classical perovskite ferroelectrics. Our findings settle a long-standing question on ferroelectric switching in biology and establish ferroelectricity as an important biophysical property of proteins. We believe this is a critical first step toward resolving its physiological significance and pathological implications.
Abstract
Ferroelectricity has long been speculated to have important biological functions, although its very existence in biology has never been firmly established. Here, we present compelling evidence that elastin, the key ECM protein found in connective tissues, is ferroelectric, and we elucidate the molecular mechanism of its switching. Nanoscale piezoresponse force microscopy and macroscopic pyroelectric measurements both show that elastin retains ferroelectricity at 473 K, with polarization on the order of 1 μC/cm2, whereas coarse-grained molecular dynamics simulations predict similar polarization with a Curie temperature of 580 K, which is higher than most synthetic molecular ferroelectrics. The polarization of elastin is found to be intrinsic in tropoelastin at the monomer level, analogous to the unit cell level polarization in classical perovskite ferroelectrics, and it switches via thermally activated cooperative rotation of dipoles. Our study sheds light onto a long-standing question on ferroelectric switching in biology and establishes ferroelectricity as an important biophysical property of proteins. This is a critical first step toward resolving its physiological significance and pathological implications.
Footnotes
↵1Y.L., H.-L.C., and M.Z. contributed equally to this work.
- ↵2To whom correspondence should be addressed. E-mail: jjli{at}uw.edu.
Author contributions: J.S., H.Z., P.S., Y.Z., and J.L. designed research; Y.L., H.-L.C., M.Z., Y.W., J.S., F.Y., F.M., P.W., and Q.N.C. performed research; Y.L., H.-L.C., M.Z., J.S., H.Z., X.M., P.S., Y.Z., and J.L. analyzed data; and P.S., Y.Z., and J.L. wrote the paper.
The authors declare no conflict of interest.
↵*This Direct Submission article had a prearranged editor.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1402909111/-/DCSupplemental.
Ferroelectric switching of elastin
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- Physical Sciences
- Physics
- Biological Sciences
- Biophysics and Computational Biology
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