02336nas a2200145   4500008004100000245005400041210005300095490000600148520193500154100001102089700001502100700001602115700001602131856004302147       2021                        eng d00aPhoto-Switching of Protein Dynamical Collectivity0 aPhotoSwitching of Protein Dynamical Collectivity0 v83 a<p class="rtejustify">We examine changes in the picosecond structural dynamics with irreversible photobleaching of red fluorescent proteins (RFP) mCherry, mOrange2 and TagRFP-T. Measurements of the protein dynamical transition using terahertz time-domain spectroscopy show in all cases an increase in the turn-on temperature in the bleached state. The result is surprising given that there is little change in the protein surface, and thus, the solvent dynamics held responsible for the transition should not change. A spectral analysis of the measurements guided by quasiharmonic calculations of the protein absorbance reveals that indeed the solvent dynamical turn-on temperature is independent of the thermal stability/photostate however the protein dynamical turn-on temperature shifts to higher temperatures. This is the first demonstration of switching the protein dynamical turn-on temperature with protein functional state. The observed shift in protein dynamical turn-on temperature relative to the solvent indicates an increase in the required mobile waters necessary for the protein picosecond motions, that is, these motions are more collective. Melting-point measurements reveal that the photobleached state is more thermally stable, and structural analysis of related RFP’s shows that there is an increase in internal water channels as well as a more uniform atomic root mean squared displacement. These observations are consistent with previous suggestions that water channels form with extended light excitation providing O<sub>2 </sub>access to the chromophore and subsequent fluorescence loss. We report that these same channels increase internal coupling enhancing thermal stability and collectivity of the picosecond protein motions. The terahertz spectroscopic characterization of the protein and solvent dynamical onsets can be applied generally to measure changes in collectivity of protein motions.</p>
1 aXu, M.1 aGeorge, D.1 aJimenez, R.1 aMarkelz, A.  uhttps://www.mdpi.com/2304-6732/8/8/30201834nas a2200385   4500008004100000020001400041245007100055210006900126260002400195300001000219520062400229653001500853653003100868653002700899653003400926653003400960653004300994653001501037653002301052653003001075653001501105653001301120653004501133653002701178653001701205653002201222653002701244653002701271653004101298653001501339100001301354700001601367700001601383856004901399       2019                        eng d  a2162-203500aAngular Distortion Removal of THz Anisotropic Dichroism Microscope0 aAngular Distortion Removal of THz Anisotropic Dichroism Microsco  aParis, Francec2019  a1 - 23 a<p>We have developed a stationary sample THz anisotropic dichroism microscope as a powerful tool for material characterization. The key innovation is the use of an iso-response curve defined by the terahertz and detection light polarizations. Here we show that following a continuous iso-response curve introduces angular distortion in the spectrum, and this distortion can be eliminated by using a discontinuous iso-response angle pairs avoiding large gradient regions. Employing this additional constraint on the relative polarizations provides a convenient technique for rapid anisotropic terahertz spectroscopy.</p>10aabsorption10aangular distortion removal10aBiomedical measurement10acontinuous iso-response curve10adetection light polarizations10adiscontinuous iso-response angle pairs10aDistortion10alight polarisation10amaterial characterization10aMicroscopy10aproteins10arapid anisotropic terahertz spectroscopy10arelative polarizations10aspectroscopy10astationary sample10aterahertz spectroscopy10aterahertz wave spectra10aTHz anisotropic dichroism microscope10avibrations1 aDeng, Y.1 aNiessen, K.1 aMarkelz, A.  uhttps://ieeexplore.ieee.org/document/887379301941nas a2200373   4500008004100000020001500041245008000056210006900136260003100205300001000236490000600246520087600252653002801128653004401156653002101200653001901221653001901240653002901259653002401288653001801312653001701330653002201347653001201369653001201381653002001393100001601413700001201429700001401441700001601455700001301471700001501484700001901499856004901518       2003                        eng d  a097284220900aFinite size effects in ferroelectric nanosystems: Absence of mode softening0 aFinite size effects in ferroelectric nanosystems Absence of mode  aSan Francisco, CAc02/2003  a76-810 v23 a<p>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.</p>10aFerroelectric materials10aFourier Transform Infrared Spectroscopy10aFrequency ranges10aLead compounds10aMode softening10ananostructured materials10aNatural frequencies10aOptical modes10aPermittivity10aphase transitions10aphonons10aRouters10aThermal effects1 aWolpert, D.1 aCox, W.1 aCerne, J.1 aMarkelz, A.1 aZhao, T.1 aRamesh, R.1 aM., Romanowicz  uhttps://markelz.physics.buffalo.edu/node/275