%0 Journal Article %J J. Phys. Chem. B %D 2021 %T Functional-State Dependence of Picosecond Protein Dynamics %A George, D. K. %A Chen, J. Y. %A He, Yunfen %A Knab, J. R. %A Markelz, A. G. %X

We examine temperature-dependent picosecond dynamics of two benchmarking proteins lysozyme and cytochrome c using temperature-dependent terahertz permittivity measurements. We find that a double Arrhenius temperature dependence with activation energies E1 ∼ 0.1 kJ/mol and E2 ∼ 10 kJ/mol fits the folded and ligand-free state response. The higher activation energy is consistent with the so-called protein dynamical transition associated with beta relaxations at the solvent–protein interface. The lower activation energy is consistent with correlated structural motions. When the structure is removed by denaturing, the lower-activation-energy process is no longer present. Additionally, the lower-activation-energy process is diminished with ligand binding but not for changes in the internal oxidation state. We suggest that the lower-energy activation process is associated with collective structural motions that are no longer accessible with denaturing or binding.

%B J. Phys. Chem. B %V 125 %P 11134-11140 %G eng %N 40 %& 11134 %R 10.1021/acs.jpcb.1c05018 %0 Journal Article %J J. Phys. Chem. C %D 2021 %T Phonon Kinetics of Fructose at the Melting Transition %A A. Davie %A F. Vandrevala %A S. Dampf %A Y. Deng %A D. K. George %A E. D. Sylvester %A T. Korter %A E. Einarsson %A J. B. Benedict %A A. G. Markelz %X

Terahertz time domain spectroscopy (THz TDS) is used to measure the melting kinetics of fructose molecular crystals. Combining single-crystal anisotropy measurements with density functional calculations, we assign the phonon frequencies and interrogate how specific phonons behave with melting. While nearly all the low-frequency phonons continuously red-shift with heating and melting, the lowest-energy phonon polarized along the c-axis blue-shifts at the melting temperature, suggesting an initial structural change immediately before melting. We find that the kinetics follow a 3D growth model with large activation energies, consistent with previous differential scanning calorimetry (DSC) measurements. The large activation energies indicate that multiple H-bonds must break collectively for the transition. The results suggest the generality of the kinetics for molecular crystals and that THz TDS with picosecond resolution could be used to measure ultrafast kinetics.

 

%B J. Phys. Chem. C %V 125 %P 12269-12276 %G eng %N 22 %& 12269 %R 10.1021/acs.jpcc.1c00610 %0 Journal Article %J Biophysical Journal %D 2020 %T Evidence of Intramolecular Structural Stabilization in Light Activated State of Orange Carotenoid Protein %A McKinney, J. A. %A Sharma, A. %A Crossen, K. %A Deng, Y. %A George, D. K. %A Lechno-Yossef, S. %A Kerfeld, C. %A Markelz, A. G. %K Biophysics %X

Orange carotenoid protein (OCP) controls efficiency of the light harvesting antenna, the phycobilisome (PBS), in diverse cyanobacteria and prevents oxidative damage. It is the only known photoactive protein that uses a carotenoid, canthaxanthin, as its chromophore. The structure of OCP consists of two globular domains, connected by an unstructured loop, that forms a hydrophobic pocket for the carotenoid. In low light, canthaxanthin bound OCP is inactive and appears orange. Illumination by strong light results in an active state that interacts with the PBS to induce fluorescence quenching, a red appearance and conformational changes that include a 12Å shift by canthaxanthin into the N-terminal domain. Terahertz (THz) dynamical transition measurements and anisotropic terahertz microscopy are used to measure the intramolecular structural dynamics in the inactive and active states, which can be induced by photoexcitation or chaotropic salts. The measurements indicate that the active state has a decrease in structural flexibility, which may be related to enhanced interactions with the PBS.

%B Biophysical Journal %V 118 %P 208A-208A %8 Feb %@ 0006-3495 %G English %N 3 %9 Meeting Abstract %M WOS:000513023201290 %R 10.1016/j.bpj.2019.11.1245 %0 Journal Article %J Physical Review B %D 2020 %T Linear dichroism infrared resonance in overdoped, underdoped, and optimally doped cuprate superconductors %A Mukherjee, A. %A Seo, J. %A Arik, M. M. %A Zhang, H. %A Zhang, C. C. %A Kirzhner, T. %A George, D. K. %A Markelz, A. G. %A Armitage, N. P. %A Koren, G. %A Wei, J. Y. T. %A Cerne, J. %K Materials Science %K Physics %X

By measuring the polarization changes in terahertz, infrared, and visible radiation over an extended energy range (3-2330 meV), we observe symmetry breaking in cuprate high-temperature superconductors over wide energy, doping, and temperature ranges. We measure the polarization rotation (Re[theta(F)]) and ellipticity (Im[theta(F)]) of transmitted radiation through thin films as the sample is rotated. We observe a twofold rotational symmetry in theta(F), which is associated with linear dichroism (LD) and occurs when electromagnetic radiation polarized along one direction is absorbed more strongly than radiation polarized in the perpendicular direction. Such polarization anisotropies can be generally associated with symmetry breakings. We measure the amplitude of the LD signal and study its temperature, energy, and doping dependence. The LD signal shows a resonant behavior with a peak in the few hundred meV range, which is coincident with the midinfrared optical feature that has been associated with the formation of the pseudogap state. The strongest LD signal is found in underdoped films, although it is also observed in optimally and overdoped samples. The LD signal is consistent with an electronic nematic order which is decoupled from the crystallographic axes as well as novel magnetoelectric effects.

%B Physical Review B %V 102 %P 6 %8 Aug %@ 2469-9950 %G English %9 Article %M WOS:000562627700004 %] 054520 %R 10.1103/PhysRevB.102.054520 %0 Journal Article %J Biophysical Journal %D 2020 %T Is the Protein Dynamical Transition useful? %A Sharma, A. %A George, D. K. %A Crossen, K. %A McKinney, J. %A Kerfeld, C. %A Markelz, A. %B Biophysical Journal %V 118 %G eng %N 3 %& 521a %R 10.1016/j.bpj.2019.11.2866 %0 Conference Proceedings %B 2020 45th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) %D 2020 %T Stabilization of Terahertz Vibrational Modes in Illuminated Orange Carotenoid Protein Crystals %A McKinney, J. %A Sharma, A. %A Deng, Y. %A George, D. %A Lechno-Yossef, S. %A Kerfeld, C. %A Markelz, A. %X

Orange carotenoid protein (OCP) controls efficiency of the phycobilisome (PBS), the light harvesting antenna in cyanobacteria, to prevent oxidative damage. The OCP switches from resting state to photo protective state with intense blue light illumination. Questions persist as to why OCPR interaction increases with the PBS over that with the OCPO. Here we examine the role of long-range intramolecular vibrations within OCP. Using Stationary Sample Anisotropic Terahertz Microscopy (SSATM) we measure changes in the intramolecular vibrations with photo switching. We report the first observation of switching in the intramolecular vibrations with photoexcitation. Results suggest that there is a stiffening of the molecule in the photo protective state. This increase in structural stability may enhance the interaction with the PBS change in OCP interaction with PBS. In low light, carotenoid bound OCP appears orange (OCP o ) and is inactive. Illumination by strong light converts OCP to the active, red (OCPR) state, which interacts with the PBS. A comparison of anisotropic THz microscopy measurements of dark adapted (OCP o ) and illuminated OCP crystals indicate differences in their vibrational modes that may be important for OCP-PBS interactions.

%B 2020 45th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) %C Buffalo, NY %G eng %R 10.1109/IRMMW-THz46771.2020.9370827 %0 Conference Proceedings %B IRMMW-THz %D 2020 %T THz Transmission through Submillimeter Apertures %A LaFave, T. %A Lee, A. %A Kao, T.-Y. %A Markelz, A. %X
Terahertz near-field microspectroscopy is emerging as an essential tool for characterization of novel materials and biomolecules. It is important to ensure the near field geometry used does not introduce spectral artifacts. For example, many scanning techniques can be strongly influenced by the interaction between the scattering tip and the sample. Here we examine the spectroscopic effects of a 200 μm diameter aperture for THz near-field measurements. We use HFSS to model free-space transmission through samples with resonant absorbance as a function of sample thickness, lateral sample width, and aperture diameter. We examine the transmitted power and spectral fidelity for coupling of transmitted THz light onto a detector. These studies inform corrective post-measurement analysis algorithms and design of near-field detection systems.
%B IRMMW-THz %C Buffalo NY %8 11/2020 %G eng %U https://ieeexplore.ieee.org/document/9370923 %R 10.1109/IRMMW-THz46771.2020.9370923 %0 Journal Article %J Bulletin of the American Physical Society %D 2019 %T Blue Shift of a Molecular Crystal Phonon at the Solid to Liquid Phase Transition %A Davie, Alex %A Vandrevala, Farah %A Deng, Yanting %A George, D. %A Sylvester, Eric D. %A Korter, T. %A Einarsson, E. %A Benedict, Jason B. %A Markelz, Andrea %B Bulletin of the American Physical Society %V 2019 %G eng %0 Conference Proceedings %B 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves %D 2019 %T Stationary Sample Anisotropic THz Spectroscopy using Discretely Tunable THz Sources %A LaFave, T., Jr. %A George, D. K. %A Markelz, A. G. %A McNee, Ian %A Kozlov, Vladimir %A Schunemann, Peter %X

We demonstrate anisotropic THz spectroscopy of sucrose using newly developed compact discretely tunable THz sources for turn-key spectroscopic systems.

%B 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves %S International Conference on Infrared Millimeter and Terahertz Waves %@ 978-1-5386-8285-2 %G eng %M WOS:000591783800538 %R https://doi.org/10.1109/IRMMW-THz.2019.8874234 %0 Conference Proceedings %B Conference on Next-Generation Spectroscopic Technologies XII %D 2019 %T Tunable Compact Narrow Band THz Sources for Frequency Domain THz Anisotropic Spectroscopy %A George, D. K. %A LaFave, T. J. %A Markelz, A. G. %A McNee, I. %A Tekavec, P. %A Kozlov, V. %A Schunemann, P. %? Spie, %? Univ Buffalo, Dept Phys Buffalo N. Y. U. S. A. %? Microtech Instruments, Eugene O. R. U. S. A. %? Bae Syst, P. O. B. Nashua N. H. U. S. A. %K anisotropy %K biomolecules %K femtosecond %K optical rectification %K orientation patterned gallium phosphide %K Terahertz %K THz generation %X

We demonstrate frequency domain THz anisotropy signature detection for protein crystal models using newly developed compact tunable narrow band THz sources based on Orientation Patterned Gallium Phosphide for turn-key spectroscopic systems.

%B Conference on Next-Generation Spectroscopic Technologies XII %S Proceedings of SPIE %I Spie-Int Soc Optical Engineering %C Baltimore, MD %V 10983 %8 Apr 15-17 %@ 978-1-5106-2632-4 %G English %M WOS:000484438200016 %1 BELLINGHAM %2 2019 %( Next-generation spectroscopic technologies xii %R https://doi.org/10.1117/12.2519878 %0 Conference Paper %B APS S23-002 %D 2019 %T Tunable narrow band sources for anisotropic THz spectroscopy %A George, D. K. %A McNee, I. %A Tekavec, P. %A Kozlov, V. %A Schunemann, P. %A Markelz, A. G. %B APS S23-002 %8 02/2019 %G eng %U https://meetings.aps.org/Meeting/MAR19/Session/S23.2 %0 Conference Proceedings %B Nonlinear Frequency Generation and Conversion: Materials and Devices Xviii %D 2019 %T Tunable narrowband THz generation in orientation patterned gallium phosphide for THz anisotropy identification %A McNee, I. %A Tekavec, P. %A Kozlov, V. %A Markelz, A. G. %A George, D. K. %A Schunemann, P. %E Schunemann, P. G. %E Schepler, K. L. %K anisotropy %K biomolecules %K femtosecond %K optical rectification %K orientation patterned gallium phosphide %K Terahertz %K THz generation %X

We demonstrate tunable narrowband THz generation by optical rectification of a femtosecond pulse in Orientation Patterned Gallium Phosphide. Center frequencies of 0.9 - 3.8 THz with average power up to 15 mu W were achieved using a 1.064 mu m fiber laser for the pump laser. Biomolecular characterization for an early application of this system is also shown in this work by anisotropic spectroscopic signature detection of molecular crystals in the THz region.

%B Nonlinear Frequency Generation and Conversion: Materials and Devices Xviii %S Proceedings of SPIE %I Spie-Int Soc Optical Engineering %C Bellingham %V 10902 %@ 978-1-5106-2447-4 %G English %M WOS:000471820400020 %R https://doi.org/10.1117/12.2510522 %0 Conference Proceedings %B 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves %D 2018 %T THz Anisotropy Identification using Tunable Compact Narrow Band THz Sources %A George, D. K. %A Markelz, A. G. %A McNee, I. %A Tekavec, P. %A Kozlov, V. %A Schunemann, P. %X

We demonstrate THz anisotropy signature determination of a protein crystal model using newly developed compact tunable narrow band THz sources for turn-key spectroscopic systems for the bio molecular community.

%B 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves %S International Conference on Infrared Millimeter and Terahertz Waves %I Ieee %C New York %@ 978-1-5386-3809-5 %G English %M WOS:000449683700444 %R https://doi.org/10.1109/IRMMW-THz.2018.8510291 %0 Journal Article %J Journal of Physics D-Applied Physics %D 2017 %T The 2017 terahertz science and technology roadmap %A Dhillon, S. S. %A Vitiello, M. S. %A Linfield, E. H. %A Davies, A. G. %A Hoffmann, M. C. %A Booske, J. %A Paoloni, C. %A Gensch, M. %A Weightman, P. %A Williams, G. P. %A Castro-Camus, E. %A Cumming, D. R. S. %A Simoens, F. %A Escorcia-Carranza, I. %A Grant, J. %A Lucyszyn, S. %A Kuwata-Gonokami, M. %A Konishi, K. %A Koch, M. %A Schmuttenmaer, C. A. %A Cocker, T. L. %A Huber, R. %A Markelz, A. G. %A Taylor, Z. D. %A Wallace, V. P. %A Zeitler, J. A. %A Sibik, J. %A Korter, T. M. %A Ellison, B. %A Rea, S. %A Goldsmith, P. %A Cooper, K. B. %A Appleby, R. %A Pardo, D. %A Huggard, P. G. %A Krozer, V. %A Shams, H. %A Fice, M. %A Renaud, C. %A Seeds, A. %A Stohr, A. %A Naftaly, M. %A Ridler, N. %A Clarke, R. %A Cunningham, J. E. %A Johnston, M. B. %K ex-vivo %K generation %K metal wave-guides %K near-field %K performance %K photoconductive emitters %K Physics %K quantum-cascade lasers %K radiation %K semiconductors %K Terahertz %K thz %K time-domain spectroscopy %X

Science and technologies based on terahertz frequency electromagnetic radiation (100 GHz-30 THz) have developed rapidly over the last 30 years. For most of the 20th Century, terahertz radiation, then referred to as sub-millimeter wave or far-infrared radiation, was mainly utilized by astronomers and some spectroscopists. Following the development of laser based terahertz time-domain spectroscopy in the 1980s and 1990s the field of THz science and technology expanded rapidly, to the extent that it now touches many areas from fundamental science to 'real world' applications. For example THz radiation is being used to optimize materials for new solar cells, and may also be a key technology for the next generation of airport security scanners. While the field was emerging it was possible to keep track of all new developments, however now the field has grown so much that it is increasingly difficult to follow the diverse range of new discoveries and applications that are appearing. At this point in time, when the field of THz science and technology is moving from an emerging to a more established and interdisciplinary field, it is apt to present a roadmap to help identify the breadth and future directions of the field. The aim of this roadmap is to present a snapshot of the present state of THz science and technology in 2017, and provide an opinion on the challenges and opportunities that the future holds. To be able to achieve this aim, we have invited a group of international experts to write 18 sections that cover most of the key areas of THz science and technology. We hope that The 2017 Roadmap on THz science and technology will prove to be a useful resource by providing a wide ranging introduction to the capabilities of THz radiation for those outside or just entering the field as well as providing perspective and breadth for those who are well established. We also feel that this review should serve as a useful guide for government and funding agencies.

%B Journal of Physics D-Applied Physics %V 50 %P 49 %8 Feb %@ 0022-3727 %G English %9 Review %M WOS:000392153700001 %] 043001 %R https://doi.org/10.1088/1361-6463/50/4/043001 %0 Journal Article %J IEEE Transactions on Terahertz Science and Technology %D 2013 %T Photoactive yellow protein terahertz response: hydration, heating and intermediate states %A George, Deepu K %A Knab, Joseph R %A He, Yunfen %A Kumauchi, Masato %A Birge, Robert R %A Hoff, Wouter D %A Markelz, Andrea G %B IEEE Transactions on Terahertz Science and Technology %V 3 %P 288-294 %@ 2156-342X %G eng %R https://doi.org/10.1109/TTHZ.2013.2256233 %0 Journal Article %J arXiv:1105.4425 %D 2012 %T Functional State Dependence of Picosecond Protein Dynamics %A Chen, J. Y. %A George, D. K. %A He, Y. %A Knab, J. R. %A Markelz, A.G. %B arXiv:1105.4425 %G eng %U http://arxiv.org/0054394 %0 Journal Article %J The Journal of Physical Chemistry A %D 2012 %T Improved mode assignment for molecular crystals through anisotropic terahertz spectroscopy %A Singh, Rohit %A George, Deepu Koshy %A Benedict, Jason B %A Korter, Timothy M %A Markelz, Andrea G %B The Journal of Physical Chemistry A %V 116 %P 10359-10364 %@ 1089-5639 %G eng %R https://doi.org/10.1021/jp307288r %0 Journal Article %J Biophysical Journal %D 2011 %T Evidence of protein collective motions on the picosecond timescale %A He, Yunfen %A Chen, J-Y %A Knab, Joseph R %A Zheng, Wenjun %A Markelz, Andrea G %B Biophysical Journal %V 100 %P 1058-1065 %@ 0006-3495 %G eng %R https://dx.doi.org/10.1016%2Fj.bpj.2010.12.3731 %0 Conference Proceedings %B 2011 36th International Conference on Infrared, Millimeter, and Terahertz Waves %D 2011 %T Magneto Optical Polarization Measurements using THz Polarization Modulation Spectroscopy %A Stier, A. V. %A George, D. %A Markelz, A. G. %A Cerne, J. %E Koch, M. %X

We report a new broad band technique for rapidly measuring the complex Faraday and Kerr rotations in materials such as topological insulators and graphene, combining the distinct advantages of THz time domain spectroscopy and polarization modulation techniques. The performance of the system is demonstrated using GaAs two dimensional electron gas in a magnetic field.

%B 2011 36th International Conference on Infrared, Millimeter, and Terahertz Waves %S International Conference on Infrared Millimeter and Terahertz Waves %I Ieee %C New York %@ 978-1-4577-0509-0 %G English %M WOS:000330296300202 %R 10.1364/JOSAB.29.001406 %0 Journal Article %J Terahertz Science and Technology %D 2010 %T Why is THz Sensitive to Protein Functional States? Oxidation State of Cytochrome C %A He,Y. %A Chen, J.-Y. %A Knab, J. R. %A Zheng, W. %A Markelz, A.G. %X

We investigate the presence of structural collective motions on a picosecond time scale for the heme protein, cytochrome c, as a function of oxidation and hydration, using terahertz (THz) time-domain spectroscopy and molecular dynamics simulations. Structural collective mode frequencies have been calculated to lie in this frequency range, and the density of states can be considered a measure of flexibility. A dramatic increase in the THz response occurs with oxidation, with the largest increase for lowest hydrations and highest frequencies. For both oxidation states the measured THz response rapidly increases with hydration saturating above ~25% (g H2O/g protein), in contrast to the rapid turn-on in dynamics observed at this hydration level for other proteins. Quasi-harmonic collective vibrational modes and dipole-dipole correlation functions are calculated from the molecular dynamics trajectories. The collective mode density of states alone reproduces the measured hydration dependence providing strong evidence of the existence of these collective motions. The large oxidation dependence is reproduced only by the dipole-dipole correlation function, indicating the contrast arises from diffusive motions consistent with structural changes occurring in the vicinity of a buried internal water molecule.

%B Terahertz Science and Technology %V 3 %G eng %U http://www.tstnetwork.org/10.11906/TST.149-162.2010.12.15/ %N 4 %& 149-162 %R 10.11906/TST.149-162.2010.12.15 %0 Journal Article %J Applied Physics LettersApplied Physics LettersApplied Physics Letters %D 2008 %T Terahertz response of quantum point contacts %A Song, J. W. %A Kabir, N. A. %A Kawano, Y. %A Ishibashi, K. %A Aizin, G. R. %A Mourokh, L. %A Reno, J. L. %A Markelz, A. G. %A Bird, J. P. %K detector %K devices %K field-effect transistors %K Physics %K plasma-waves %K radiation %K resonant detection %K subterahertz %K transport %X

We measure a clear terahertz response in the low-temperature conductance of a quantum point contact at 1.4 and 2.5 THz. We show that this photoresponse does not arise from a heating effect, but that it is instead excellently described by a classical model of terahertz-induced gate-voltage rectification. This effect is distinct from the rectification mechanisms that have been studied previously, being determined by the phase-dependent interference of the source drain and gate voltage modulations induced by the terahertz field. (C) 2008 American Institute of Physics.

%B Applied Physics LettersApplied Physics LettersApplied Physics Letters %V 92 %P 3 %8 Jun %@ 0003-6951 %G English %9 Article %M WOS:000256527900083 %] 223115 %! Appl. Phys. Lett.Appl. Phys. Lett. %R https://doi.org/10.1063/1.2938416 %0 Book Section %B Terahertz Frequency Detection and Identification of Materials and Objects %D 2007 %T Development of Tagless Biosensors for Detecting the Presence of Pathogens %A Markelz, A. G. %A Chen, J.-Y. %A Knab, J. R. %A He, Y. %A Ye, S. %B Terahertz Frequency Detection and Identification of Materials and Objects %I Springer %C Dordrecht, The Netherlands %V ed X.-C. Zhang, R. E. Miles, H. Eisele and A. Krotkus %P 123-134 %G eng %& 9 %0 Journal Article %J Chemical Physics Letters %D 2007 %T Protein dynamical transition in terahertz dielectric response %A Markelz, Andrea G. %A Knab, Joseph R. %A Chen, Jing Yin %A He, Yunfen %X

The 200K protein dynamical transition is observed for the first time in the terahertz dielectric response. The complex dielectric permittivity ε=ε′+iε″ is determined in the 0.2–2.0THz and 80–294K ranges. ε″ has a linear temperature dependence up to 200K then sharply increases. The low temperature linear dependence in ε″ suggests anharmonicity for temperatures 80K<t<180k, challenging="" the="" assumed="" harmonicity="" below="" 200k.="" temperature="" dependence="" is="" consistent="" with="" thermally="" activated="" sidechain="" motions="" and="" shows="" involved="" in="" dynamical="" transition="" extend="" to="" subpicosecond="" time="" scales.<="" div="">

%B Chemical Physics Letters %V 442 %P 413 - 417 %@ 0009-2614 %G eng %U https://www.sciencedirect.com/science/article/pii/S000926140700680X %N 4 %! Chemical Physics Letters %R 10.1016/j.cplett.2007.05.080 %0 Journal Article %J Applied Physics Letters %D 2007 %T Terahertz dielectric assay of solution phase protein binding %A Chen, J. Y. %A Knab, J. R. %A Ye, S. J. %A He, Y. F. %A Markelz, A. G. %K dynamics %K lysozyme %K Physics %K spectroscopy %K water %X

The authors demonstrate a method for rapid determination of protein-ligand binding on solution phase samples using terahertz dielectric spectroscopy. Measurements were performed using terahertz time domain spectroscopy on aqueous solutions below the liquid-solid transition for water. Small ligand binding sensitivity was demonstrated using triacetylglucosamine and hen egg white lysozyme with a decrease in dielectric response with binding. The magnitude of the change increases with frequency. (c) 2007 American Institute of Physics.

%B Applied Physics Letters %V 90 %P 3 %8 Jun %@ 0003-6951 %G English %9 Article %M WOS:000247305400108 %] 243901 %! Appl. Phys. Lett.Appl. Phys. Lett. %R 10.1063/1.2748852 %0 Journal Article %J Proceedings of the IEEE %D 2007 %T Terahertz measurements of protein relaxational dynamics %A Knab, Joseph R %A Chen, Jing-Yin %A He, Yunfen %A Markelz, Andrea G %B Proceedings of the IEEE %V 95 %P 1605-1610 %@ 0018-9219 %G eng %R 10.1109/JPROC.2007.898906 %0 Journal Article %J Biophysical Journal %D 2006 %T Hydration dependence of conformational dielectric relaxation of lysozyme %A Knab, Joseph %A Chen, Jing-Yin %A Markelz, Andrea %B Biophysical Journal %V 90 %P 2576-2581 %@ 0006-3495 %G eng %R 10.1529/biophysj.105.069088 %0 Conference Proceedings %B 2006 Joint 31st International Conference on Infrared Millimeter Waves and 14th International Conference on Teraherz Electronics %D 2006 %T Protein conformational dynamics measured with terahertz time domain spectroscopy %A Knab, Joseph R %A Chen, Jing-Yin %A Ye, Shuji %A He, Yunfen %A Markelz, Andrea G %B 2006 Joint 31st International Conference on Infrared Millimeter Waves and 14th International Conference on Teraherz Electronics %I IEEE %P 183-183 %@ 1424403995 %G eng %R https://doi.org/10.1088/0031-9155/47/21/318 %0 Journal Article %J Applied Physics Letters %D 2006 %T Terahertz transmission characteristics of high-mobility GaAs and InAs two-dimensional-electron-gas systems %A Kabir, N. A. %A Yoon, Y. %A Knab, J. R. %A Chen, J. Y. %A Markelz, A. G. %A Reno, J. L. %A Sadofyev, Y. %A Johnson, S. %A Zhang, Y. H. %A Bird, J. P. %K field-effect transistors %K photoconductivity %K Physics %K plasma-waves %K radiation %K resonant detection %K subterahertz %X

Frequency-dependent complex conductivity of high-mobility GaAs and InAs two-dimensional-electron-gas (2DEG) systems is studied by terahertz time domain spectroscopy. Determining the momentum relaxation time from a Drude model, the authors find a lower value than that from dc measurements, particularly at high frequencies/low temperatures. These deviations are consistent with the ratio tau(t)/tau(q,) where tau(q) is the full scattering time. This suggests that small-angle scattering leads to weaker heating of 2DEGs at low temperatures than expected from dc mobilit9y. (c) 2006 American Institute of Physics.

%B Applied Physics Letters %V 89 %P 3 %8 Sep %@ 0003-6951 %G English %9 Article %M WOS:000240875800066 %] 132109 %! Appl. Phys. Lett.Appl. Phys. Lett. %R 10.1063/1.2357605 %0 Conference Proceedings %B Proceedings of the 28th International Conference on the Physics of Semiconductors %D 2006 %T Ultrafast Carriers Dynamics in GaSb/Mn Random Alloys %A Ye, S. %A Knab, J. %A Chen, J.-Y. %A Wang, S. %A Cheon, M. %A Luo, H. %A Markelz, A. G. %B Proceedings of the 28th International Conference on the Physics of Semiconductors %C Vienna Austria %G eng %R 10.1063/1.2730382 %0 Conference Proceedings %B Advanced Biomedical and Clinical Diagnostic Systems IV; %D 2006 %T Using terahertz spectroscopy as a protein binding assay %A Chen, J.-Y. %A Knab, J. R. %A Ye, S. %A He, Y. %A Markelz, A. G. %X

The vibrational modes corresponding to protein tertiary structural motion lay in the far infrared or terahertz frequency range. These collective large scale motions depend on global structure and thus will necessarily be perturbed by ligand binding events. We discuss the use of terahertz dielectric spectroscopy to measure these vibrational modes and the sensitivity of the technique to changes in protein conformation, oxidation state and environment. A challenge of applying this sensitivity as a spectroscopic assay for ligand binding is the sensitivity of the technique to both bulk water and water bound to the protein. This sensitivity can entirely obscure the signal from the protein or protein-ligand complex itself, thus necessitating sophisticated sample preparation making the technique impractical for industrial applications. We discuss methods to overcome this background and demonstrate how terahertz spectroscopy can be used to quickly assay protein binding for proteomics and pharmaceutical research.

%B Advanced Biomedical and Clinical Diagnostic Systems IV; %C San Jose, California, United States %V Proc SPIE 6080, %P 35-42 %8 02/2006 %G eng %R 10.1117/12.664098 %0 Conference Proceedings %B Chemical and Biological Standoff Detection III %D 2005 %T Critical hydration and temperature effects on terahertz biomolecular sensing %A Knab, Joseph %A Shah, Binni %A Chen, Jing-Yin %A Markelz, Andrea %B Chemical and Biological Standoff Detection III %I International Society for Optics and Photonics %V 5995 %P 59950P %G eng %R 10.1117/12.630854 %0 Journal Article %J Physical Review E %D 2005 %T Large oxidation dependence observed in terahertz dielectric response for cytochrome c %A Chen, J. Y. %A Knab, J. R. %A Cerne, J. %A Markelz, A. G. %K absorption %K binding %K conformation %K dna %K dynamics %K heart ferricytochrome-c %K modes %K Physics %K protein flexibility %K spectroscopy %K state %X

Far infrared dielectric response is used to characterize the collective mode density of states for cytochrome c as a function of oxidation state and hydration using terahertz time domain spectroscopy. A strong absorbance and refractive index increase was observed with the oxidation. A simple phenomenological fitting using a continuous distribution of oscillators reproduces the frequency dependence of the complex dielectric response as well as demonstrates quantitative agreement with a uniform increase in either mode density or polarizability with oxidation in the 5-80 cm(-1) frequency range. Hydration dependence measurements find that a difference in the equilibrium water content for ferri and ferro cytochrome c is not sufficient to account for the large change in terahertz response. The large dielectric increase at terahertz frequencies with oxidation suggests either a significant global softening of the potential and/or a significant increase in polarizability with oxidation.

%B Physical Review E %V 72 %P 4 %8 Oct %@ 1539-3755 %G English %9 Article %M WOS:000232930600005 %] 040901 %R 10.1103/PhysRevE.72.040901 %0 Journal Article %J Abstracts of Papers of the American Chemical Society %D 2005 %T Protein dynamics studies using terahertz dielectric response %A Markelz, A. G. %A Knab, J. R. %A Chen, J. Y. %K Chemistry %B Abstracts of Papers of the American Chemical Society %V 230 %P U347-U348 %8 Aug %@ 0065-7727 %G English %9 Meeting Abstract %M WOS:000236797300675 %! Abstr. Pap. Am. Chem. Soc.Abstr. Pap. Am. Chem. Soc. %R 10.1016/j.cplett.2007.05.080 %0 Conference Proceedings %B Proceedings of the IEEE LEOS Summer Topical Meeting %D 2004 %T Measuring Protein Flexibility with Terahertz Spectroscopy: Basic Research and Applications %A Markelz, A. G. %A Chen, J.-Y. %A Knab, J. R. %A Maeder, M. %B Proceedings of the IEEE LEOS Summer Topical Meeting %C San Diego, CA %8 06/2004 %G eng %R 10.1109/LEOSST.2004.1338649 %0 Conference Proceedings %B Terahertz for military and security applications Ii %D 2004 %T Tagless and universal biosensor for point detection of pathogens %A Markelz, Andrea G %A Knab, Joseph R %A Chen, Jing-Yin %A Černe, John %A Cox, William A %B Terahertz for military and security applications Ii %I International Society for Optics and Photonics %V 5411 %P 182-186 %G eng %R https://doi.org/10.1117/12.563613 %0 Conference Proceedings %B Mater. Res. Soc. Symp. %D 2004 %T Terahertz measurements of the Photoactive Protein Bacteriorhodopsin mutant D96N: M and P states %A Chen, C.-Y. %A Knab, J. R. %A Cerne, J. %A Hillebrecht, J. R. %A Birge, R. R. %A Markelz, A. G. %X

We use terahertz (THz) spectroscopy as a biomaterials characterization tool. Previously we have shown a strong contrast between the THz dielectric response for wild type (WT) and D96N mutant of bacteriorhodopsin. In those studies we observed a large increase in the THz absorbance of WT with excitation to thermally captured photo-intermediates whereas no such increase in absorbance was observed for the mutant D96N. These results suggest that the THz response is sensitive to structural changes and relative flexibility of biomolecules. However the photo-intermediate populations of the WT and D96N samples were not equivalent in those measurements. While the WT samples had relaxed (bR), M and P state intermediates present, the D96N samples had only bR and M states. Here we present terahertz absorbance measurements of D96N as a function of M and P state populations at room temperature. The THz response is constant for intermediate states populations up to 23% M state and up to 30% P state. These results verify that there is a fundamental difference in the conformational dynamics as measured by THz dielectric response for a single residue mutation.

%B Mater. Res. Soc. Symp. %S in Proteins as Materials (ed. V. P. Conteicello, et al) %C Warrendale, PA %V 826 %P pages261–267 %G eng %R 10.1557/PROC-826-V2.6 %0 Conference Proceedings %B Proceedings of SPIE Optics East %D 2004 %T Thz Dielectric Response As A Function Of Protein Hydration: Intramolecular Coupling Contribution %A Markelz, A. G. %A Chen, J.-Y. %A Knab, J. R. %A Maeder, M. %B Proceedings of SPIE Optics East %C Philadelphia, PA %8 10/2004 %G eng %0 Journal Article %J Physica E: Low-dimensional Systems and Nanostructures %D 2003 %T Direct measurements of optical phonons in SrTiO3 nanosystems %A Wolpert, D %A Korolev, K %A Sachs, S %A Knab, J %A Cox, W %A Cerne, J %A Markelz, A.G %A Zhao, T %A Ramesh, R %A Moeckly, B.H %K Ferroelectrics %K Finite size %K Mode softening %K phonons %K Strontium titanate %K Terahertz %X

We use terahertz time domain spectroscopy to examine finite size effects on the optical phonon modes in SrTiO3 thin films. In temperature-dependent measurements we find a near absence of mode softening in the TO1 phonon frequency. Furthermore we see an increase in the soft mode frequency with reduced thickness. Both of these results correlate well with the reduced dielectric response observed for nanoscale ferroelectric systems.

%B Physica E: Low-dimensional Systems and Nanostructures %V 19 %P 236 - 239 %8 2003/07/01/ %@ 1386-9477 %G eng %U https://www.sciencedirect.com/science/article/pii/S1386947703003059 %N 1 %! Physica E: Low-dimensional Systems and Nanostructures %R 10.1016/S1386-9477(03)00305-9 %0 Conference Proceedings %B SPIE Proceedings %D 1994 %T Far-infrared harmonic generation from semiconductor heterostructures %A Markelz, A.G. %A Gwinn, E. G. %A Sherwin, M. S. %A Heyman, J. N. %A Nguyen, C. %A Kroemer, H. %B SPIE Proceedings %V 1854 %P 48-55 %G eng %0 Conference Proceedings %B Proceedings of the International Conference on the Physics of Semiconductors %D 1994 %T Frequency Dependence of the Third Order Susceptibility of InAs Quantum Wells at Terahertz Frequencies %A Markelz, A.G. %A Cerne, J. %A Gwinn, E. G. %A Brar, B. %A Kroemer, H. %B Proceedings of the International Conference on the Physics of Semiconductors %P 1193-1196 %8 08/1994 %G eng %0 Journal Article %J Solid-State Electronics %D 1994 %T GIANT 3RD-ORDER NONLINEAR SUSCEPTIBILITIES FOR INPLANE FAR-INFRARED EXCITATION OF SINGLE INAS QUANTUM-WELLS %A Markelz, A. G. %A Gwinn, E. G. %A Sherwin, M. S. %A Nguyen, C. %A Kroemer, H. %X

Third-order, free-carrier nonlinear susceptibilities, chi(3), have been measured between 19 and 23 cm-1 for three InAs/AlSb quantum wells with sheet densities between 2.5 x 10(12) cm-2 and 8 x 10(12) cm-2. We find that these wells are strongly nonlinear at far-infrared frequencies: odd harmonics ninth order have been observed at high incident intensities, and the peak value of chi(3) reaches approximately 1 esu. This is several orders of magnitude larger than previously reported values for chi(3) in bulk n-GaAs (10(-4) esu)[1] and in polyacetylene (10(-7) esu)[2]. The large magnitude of chi(3) is attributed to the high carrier density in the InAs wells, and to the strong non-parabolicity of the conduction band in InAs. However, the free-carrier chi(3) for bulk InAs predicts a density-dependence different from that observed, and the measured decrease in chi(3) with increasing intensity indicates non-perturbative response. We find that the anisotropy of chi(3) displays the expected 4-fold symmetry.

%B Solid-State Electronics %V 37 %P 1243-1245 %8 Apr-Jun %@ 0038-1101 %G eng %M WOS:A1994NE79600163 %R 10.1016/0038-1101(94)90399-9 %0 Journal Article %J Journal of Luminescence %D 1994 %T PROBING TERAHERTZ DYNAMICS IN SEMICONDUCTOR NANOSTRUCTURES WITH UCSB FREE-ELECTRON LASERS %A Allen, S. J. %A Craig, K. %A Felix, C. L. %A Guimaraes, P. %A Heyman, J. N. %A Kaminski, J. P. %A Keay, B. J. %A Markelz, A. G. %A Ramian, G. %A Scott, J. S. %A Sherwin, M. S. %A Campman, K. L. %A Hopkins, P. F. %A Gossard, A. C. %A Chow, D. %A Lui, M. %A Liu, T. Y. %X

The UCSB free-electron lasers provide kilowatts of continuously tunable radiation from 120 GHz to 4.8 THz. They have the most impact on terahertz science and technology that require a tunable, high power source to explore non-linear dynamics or that sacrifice incident power to recover the linear response of systems with very small cross-section. We describe three experiments that demonstrate the utility of these lasers in experiments on the terahertz dynamics of semiconductor nanostructures: (i) terahertz dynamics of resonant tunneling diodes, (ii) saturation spectroscopy of quantum wells and (iii) photon-assisted tunneling in superlattices.

%B Journal of Luminescence %V 60-1 %P 250-255 %8 Apr %@ 0022-2313 %G eng %M WOS:A1994NR36100065 %R 10.1016/0022-2313(94)90142-2 %0 Journal Article %J Semiconductor Science and Technology %D 1994 %T SUBCUBIC POWER DEPENDENCE OF 3RD-HARMONIC GENERATION FOR INPLANE, FAR-INFRARED EXCITATION OF INAS QUANTUM-WELLS %A Markelz, A. G. %A Asmar, N. G. %A Gwinn, E. G. %A Sherwin, M. S. %A Nguyen, C. %A Kroemer, H. %X

Large third-order, free-carrier nonlinear susceptibilities, chi(3) (to approximately 0.2 esu), and subcubic dependence of the third-harmonic power on the incident intensity, have been observed between 19 cm-1 and 23 cm-1 for InAs/AlSb quantum wells with electron sheet densities between 2.5 x 10(12) cm-2 and 8 X 10(12) cm-2. We find that the transmission of the fundamental, and the samples' DC conductivity, decrease with increasing incident intensity, indicating a large rise in the scattering rate. Using the intensity-dependent transmission to account for absorption in the sample is not sufficient to recover a cubic power law for the third-harmonic intensity. In addition, given the increased scattering rate indicated by the conductivity data, the bulk free-carrier chi(3) due to non-parabolicity should decrease dramatically with increasing fundamental intensity, contrary to our results. Thus, non-parabolicity alone cannot account for the observed third-harmonic response.

%B Semiconductor Science and Technology %V 9 %P 634-637 %8 May %@ 0268-1242 %G eng %M WOS:A1994NM75300063 %! Semicond. Sci. Technol. %R https://doi.org/10.1088/0268-1242/9/5S/063 %0 Journal Article %J Physical Review B %D 1988 %T SMALL OXYGEN ISOTOPE SHIFT IN YBA2CU3O7 %A Morris, D. E. %A Kuroda, R. M. %A Markelz, A. G. %A Nickel, J. H. %A Wei, J. Y. T. %B Physical Review B %V 37 %P 5936-5939 %8 Apr 1 %@ 0163-1829 %G eng %M WOS:A1988M824000089 %R 10.1103/physrevb.37.5936 %0 Journal Article %J Physical Review B %D 1988 %T SPECIFIC-HEAT MEASUREMENTS ON SUPERCONDUCTING BI-CA-SR-CU AND TL-CA-BA-CU OXIDES - ABSENCE OF A LINEAR TERM IN THE SPECIFIC-HEAT OF BI-CA-SR-CU OXIDES %A Fisher, R. A. %A Kim, S. %A Lacy, S. E. %A Phillips, N. E. %A Morris, D. E. %A Markelz, A. G. %A Wei, J. Y. T. %A Ginley, D. S. %B Physical Review B %V 38 %P 11942-11945 %8 Dec 1 %@ 0163-1829 %G eng %M WOS:A1988R274300075 %R 10.1103/PhysRevB.38.11942