%0 Journal Article %J Optics Express %D 2019 %T Near-field THz micropolarimetry %A Niessen, K. %A Deng, Y. T. %A Markelz, A. G. %K binding %K conductivity %K dynamics %K modes %K Optics %K polarization modulation %K Terahertz %K time-domain spectroscopy %K wse2 %X

We introduce a method for rapid determination of anisotropic terahertz absorption with sub micron resolution and high spectral integrity in the terahertz range. The method is ideal for microscopic and environmentally sensitive materials such as 2-D materials and protein crystals where the anisotropic absorption is critical to understanding underlying physics. We introduce the idea of using an iso-response relationship between the THz polarization and electro optic probe polarization to enable stationary sample polarization measurements covering a full 2 pi polarization dependence measurement. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

%B Optics Express %V 27 %P 28036-28047 %8 Sep %@ 1094-4087 %G English %9 Article %M WOS:000488282800076 %! Opt. ExpressOpt. Express %R https://doi.org/10.1364/OE.27.028036 %0 Conference Paper %B APS 2018 %D 2018 %T Rapid Terahertz Dichroism Near Field Microscopy for Biomolecular Intramolecular Vibrational Spectroscopy %A Deng, Y. %A Niessen, K. %A Markelz, A. %B APS 2018 %V A50.008 %G eng %U http://meetings.aps.org/link/BAPS.2018.MAR.A50.8 %0 Conference Proceedings %B 2016 41st International Conference on Infrared, Millimeter, and Terahertz Waves %D 2016 %T Anisotropic Absorption Measurements Reveal Protein Dynamical Transition in Intramolecular Vibrations %A Xu, M. Y. %A Niessen, K. %A Michki, N. %A Deng, Y. T. %A Snell, E. %A Markelz, A. G. %X

Modeling has predicted that intramolecular structural vibrations enables proteins to access functionally important structural change. We show that the vibrational density of states and the isotropic absorption in the terahertz range are only weakly dependent on the protein functional state for several bench marking proteins. At the same time the direction of motions changes dramatically with functional state and with a resulting impact on the anisotropic absorption. Our anisotropic THz microscopy (ATM) measurements confirm this sensitivity. Here we apply the technique to the question of whether the protein dynamical transition (DT) is important to protein function. We find a strong anisotropic resonance at 70 cm(-1) rapidly increases in strength at temperatures above the DT. As these intramolecular vibrations enable protein structure to change conformation, the results suggest function will cease below DT for those proteins that require large scale conformational change.

%B 2016 41st International Conference on Infrared, Millimeter, and Terahertz Waves %S International Conference on Infrared Millimeter and Terahertz Waves %I Ieee %C New York %@ 978-1-4673-8485-8 %G English %M WOS:000391406200009 %R 10.1109/IRMMW-THz.2016.7758347