EPSRC CDT in Metamaterials (PhD Studentship): Testing Fluctuation Relations of Conformal Changes of Biomolecules

University of Exeter - Departments of Physics and Engineering

Joint supervisors: Prof Frank Vollmer, Dr Janet Anders

The project aims to reveal the overall energy change associated with the structural fluctuations of proteins which compete with thermal fluctuations. By applying light of various intensities, the dipole force applied to the proteins can be varied while the random thermal forces are constant. The envisaged experiments are expected to provide a method to study to which extend the applied and the random forces play a role for biological function, such as enzyme activity [2], and allow us to test fundamental fluctuation relations [3] and perform free energy measurements [4] in an entirely new way.

Optoplasmonic sensors are made up of an optical cavity that is coupled to a plasmonic nanostructure, such as a gold nanorod, to which proteins and other biomolecules can be fixed. With the protein’s centre of mass being immobilised, the conformal changes of the protein can be revealed with the optoplasmonic sensor [1]. This is achieved by measuring in time the overlap of the protein with an externally applied light field concentrated at the nanoscale, which is observed as a shift of the resonant frequency/wavelength in time. The sensor reveals conformal motions of the protein with or against the local light field gradient. By changing the light intensity we can increase the field gradients. The proteins are then subject to larger dipole forces and will be pulled apart/squeezed together more. Resonance frequency shifts arising from these effects can be observed with optoplasmonic sensors due to their exceedingly high sensitivity, which can detect even single atom changes.

(i) The metamaterials aspect of this project is the unique combination of a biomaterial (eg proteins) with man-made photonic nanostructures.

(ii) The project fits well within several of the CDTs themes, including Bio-inspired Metamaterials, Photonics and Plasmonics, as well as Quantum Metamaterials.

(iii) The project is ground-breaking because it will establish optoplasmonic sensors as a technique to study fluctuations at the nanoscale in a quantitative manner. The aim of the PhD project is to develop these experiments and their analysis in several directions including a) testing the (quantum) limits of optoplasmonic sensors, b) testing fluctuation relations [3], and c) use fluctuation relations to read out energy landscapes [4] associated with conformal changes of proteins that respond to tiny forces (zepto-Newtons). The ambition is to show that nanoscale forces comparable to thermal forces can affect the function of biomolecules in a measurable way. Extending and testing humankind’s knowledge of the efficiency of biomolecular functions and turnover rates is needed to realise the optimal synthesis of biomolecules in the future.

iv) The student will be part of the vibrant Metamaterials CDT community, which has broad expertise in the physics and engineering of synthetic and natural materials. The student will also greatly benefit from interactions with researchers in the newly established Living Systems Institute (LSI).

[1] E. Kim, M. Baasked, F. Vollmer, Advanced Materials 28, 9941 (2016); E. Kim, M. Baaske, I. Schuldes, P. Wilsch, F. Vollmer, Scientific Advances 3, e1603044 (2017).
[2] S. Jevtic, J. Anders, Journal of Chemical Physics, to appear (2017).
[3] J. Liphardt, S. Dumont, S. Smith, I. Tinoco Jr., C. Bustamente, Science 296, 1832 (2002).
[4] A. Alemany, A. Mossa, I. Junier, F. Ritort, Nature 8, 688 (2012); News + Views: J. Liphardt Nature 8, 638 (2012).

This studentship is part of the Centre of Doctoral Training in Metamaterials. Please see all fully funded opportunities.

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