@article {545, title = {Functional-State Dependence of Picosecond Protein Dynamics}, journal = {J. Phys. Chem. B}, volume = {125}, year = {2021}, pages = {11134-11140}, chapter = {11134}, abstract = {

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{\textendash}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.

}, doi = {10.1021/acs.jpcb.1c05018}, author = {George, D. K. and Chen, J. Y. and He, Yunfen and Knab, J. R. and Markelz, A. G.} } @article {291, title = {Functional State Dependence of Picosecond Protein Dynamics}, journal = {arXiv:1105.4425}, year = {2012}, url = {http://arxiv.org/0054394}, author = {Chen, J. Y. and George, D. K. and He, Y. and Knab, J. R. and Markelz, A.G.} } @proceedings {275, title = {Finite size effects in ferroelectric nanosystems: Absence of mode softening}, volume = {2}, year = {2003}, note = {cited By 0}, month = {02/2003}, pages = {76-81}, address = {San Francisco, CA}, abstract = {

We present measurements of the mode softening behavior for PbZr 0.5Ti0.5O3 (PZT(50)) thin films using terahertz time domain spectroscopy (TTDS). The films were grown using pulsed laser deposition (PLD) techniques on silicon substrates to study how reduced size affects the mode softening behavior. At room temperature two modes are observed at 1.1 THz (37 cm-1) and at 2.3 THz (77 cm-1). As the temperature is increased toward Tc we do not see strong mode softening, but rather a spectral weight transfer from the high frequency mode to the low frequency mode. This absence of mode softening is more dramatic than that reported by other investigators[1]. We will discuss the possible sources for this discrepancy. These results suggest a change in lattice dynamics for nanoscale ferroelectric films that may be highly dependent on the sample preparation technique.

}, keywords = {Ferroelectric materials, Fourier Transform Infrared Spectroscopy, Frequency ranges, Lead compounds, Mode softening, nanostructured materials, Natural frequencies, Optical modes, Permittivity, phase transitions, phonons, Routers, Thermal effects}, isbn = {0972842209}, author = {D. Wolpert and W. Cox and J. Cerne and A. Markelz and T. Zhao and R. Ramesh}, editor = {Romanowicz M.} } @proceedings {319, title = {Far-infrared harmonic generation from semiconductor heterostructures}, volume = {1854}, year = {1994}, pages = {48-55}, author = {Markelz, A.G. and Gwinn, E. G. and Sherwin, M. S. and Heyman, J. N. and Nguyen, C. and Kroemer, H.} } @article {264, title = {FAR-INFRARED SATURATION SPECTROSCOPY OF A SINGLE SQUARE-WELL}, journal = {Semiconductor Science and Technology}, volume = {9}, number = {5}, year = {1994}, note = {Sherwin, Mark S/Q-4762-2017
Sherwin, Mark S/0000-0002-3869-1893; Markelz, Andrea/0000-0003-0443-4319
S
8th International Conference on Hot Carriers in Semiconductors
Aug 16-20, 1993
Oxford univ, oxford, england
Sci \& engn res council; royal soc; brit council; oxford univ
31}, month = {May}, pages = {627-629}, abstract = {

We have performed saturation spectroscopy measurements of the lowest intersubband transition in a single 400 angstrom GaAs/Al0.3Ga0.7As modulation-doped square quantum well. We couple intense tunable far-infrared radiation from the Santa Barbara free electron laser into our sample using an edge-coupling technique and measure absorption as a function of frequency and intensity. Saturation and frequency shifts in the absorption line are clearly observed. We attribute the frequency shifts to reductions in the many-body depolarization shift. From our preliminary measurements, we estimate the intersubband relaxation time to be 600 ps to within a factor of three.

}, isbn = {0268-1242}, doi = {10.1088/0268-1242/9/5S/061}, author = {Craig, K. and Felix, C. L. and Heyman, J. N. and Markelz, A. G. and Sherwin, M. S. and Campman, K. L. and Hopkins, P. F. and Gossard, A. C.} } @proceedings {318, title = {Frequency Dependence of the Third Order Susceptibility of InAs Quantum Wells at Terahertz Frequencies}, year = {1994}, month = {08/1994}, pages = {1193-1196}, author = {Markelz, A.G. and Cerne, J. and Gwinn, E. G. and Brar, B. and Kroemer, H.} } @proceedings {320, title = {Far-infrared nonlinear response of electrons in semiconductor nanostructures}, volume = {1854}, year = {1993}, pages = {36-47}, author = {Sherwin, M. S. and Asmar, N. G. and Bewley, W. W. and Craig, K. and Felix, C. L. and Galdrikian, B. and Gwinn, E. G. and Markelz, A.G. and Gossard, A. C. and Hopkins, P. F. and Sundaram, M. and Birnir, B.} }