Thermal conductivity of water-insoluble solid proteins – Paper published in Journal of Physical Chemistry Letters (Congrats Brian Foley)!

We have reported the first measurements of the thermal conductivity of films of water-insoluble solid protein films.  These measurements allow us to evaluate the heat transfer mechanisms in proteins, and evaluate models and hypotheses based on how thermal vibrations transport energy in fractal geometries.  Our work was recently published in Journal of Physical Chemistry Letters (“Protein thermal conductivity measured in the solid state reveals anharmonic interactions of vibrations in a fractal structure,” Journal of Physical Chemistry Letters DOI: 10.1021/jz500174x).  Congratulations to Brian Foley who is the first author on this work!!! This work summarizes collaborations with Brian Kaehr at Sandia National Laboratories and University of New Mexico along with Prof. Costel Constantin at James Madison University.  We all appreciate the generous support from the Office of Naval Research (YIP), U.S. Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences (BES), Division of Materials Sciences and Engineering, the Commonwealth Research Commercialization Fund (CRCF) of Virginia and the 4-VA mini-grant for university collaboration in the Commonwealth of Virginia.

Abstract

Energy processes and vibrations in biological macromolecules such as proteins ultimately dictate biological, chemical, and physical functions in living materials. These energetic vibrations in the ribbon-like motifs of proteins interact on self-similar structures and fractal-like objects over a range of length scales of the protein (a few angstroms to the size of the protein itself, a few nanometers). In fact, the fractal geometries of protein molecules create a complex network of vibrations; therefore, proteins represent an ideal material system to study the underlying mechanisms driving vibrational thermal transport in a dense, fractal network. However, experimental studies of thermal energy transport in proteins have been limited to dispersive protein suspensions, which limits the knowledge that can be extracted about how vibrational energy is transferred in a pure protein solid. We overcome this by synthesizing solid, water-insoluble protein films for thermal conductivity measurements via time-domain thermoreflectance. We measure the thermal conductivity of bovine serum albumin and myoglobin solid films over a range of temperatures from 77 to 296 K. These temperature trends indicate that anharmonic coupling of vibrations in the protein is contributing to thermal conductivity. This first-ever observation of anharmonic-like trends in the thermal conductivity of a fully dense protein forms the basis of validation of seminal theories of vibrational energy-transfer processes in fractal objects.

P.E.H. appreciates financial support from the Office of Naval Research (N00014-13-4-0528). B.K. acknowledges support from the U.S. Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences (BES), Division of Materials Sciences and Engineering. This work was partially supported by the Commonwealth Research Commercialization Fund (CRCF) of Virginia and the 4-VA mini-grant for university collaboration in the Commonwealth of Virginia. Sandia National Laboratories is a multiprogram laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy National Nuclear Security Administration under contract no. DE-AC04-94AL85000.

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