The Pyroelectricity in M13 Bacteriophage

Pyroelectricity serves important biological functions to sense the temperature of living organisms. However, the molecular mechanisms of pyroelectricity in biomaterials are not fully understood. Here we exploit the M13 bacteriophage (phage) as a model system to investigate the structure-and-function relationship of biological pyroelectricity. M13 phage possesses intrinsically aligned dipole structures originating from α-helical structures of the major coat protein (pVIII) arranged in a five-fold helical symmetry without an inversion center. We genetically engineer the tail part of the phage with six-histidine to fabricate vertically standing unidirectionally polarized phage structures on gold substrates. Through additional major coat protein engineering with different numbers of negatively charged glutamate, we investigate the chemical structure-dependent pyroelectric properties of the phage. M13 phage exhibits a pyroelectric coefficient of 0.058 μC m^-2 K^-1 upon heating. We also genetically modify the phage to sense different chemical environments based on pyroelectric sensing modality. Computation modeling and circular dichroism spectroscopy analysis verify that the unfolding of the α-helices of pVIII proteins can induce the phage protein polarization changes upon heating. Our phage-based approach to investigating bio-pyroelectricity will enhance our understanding of the thermos-electric behaviors of biomaterials and develop novel biomaterials that can be used for biosensors and electric energy generators in the future.