02182nas a2200301 4500008004500000020001400045245011000059210006900169260000800238300000600246490000800252520133400260653002201594653001201616100001801628700001201646700001701658700001401675700001801689700001701707700001901724700002001743700002101763700001401784700001901798700001401817856004901831 2020 Engldsh a2469-995000aLinear dichroism infrared resonance in overdoped, underdoped, and optimally doped cuprate superconductors0 aLinear dichroism infrared resonance in overdoped underdoped and cAug a60 v1023 a
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.
10aMaterials Science10aPhysics1 aMukherjee, A.1 aSeo, J.1 aArik, M., M.1 aZhang, H.1 aZhang, C., C.1 aKirzhner, T.1 aGeorge, D., K.1 aMarkelz, A., G.1 aArmitage, N., P.1 aKoren, G.1 aWei, J., Y. T.1 aCerne, J. uhttps://markelz.physics.buffalo.edu/node/23801739nas a2200205 4500008004500000020001400045245008900059210006900148260000800217300001400225490000800239520112900247653001501376100002101391700001701412700001901429700001601448700002001464856004901484 2020 Engldsh a0006-349500aLong Range Correlated Motions of TIM and their Possible Influence on Enzyme Function0 aLong Range Correlated Motions of TIM and their Possible Influenc cFeb a207A-207A0 v1183 aThe alpha-beta barrel structure of triosephosphate isomerase (TIM) is possibly the most common among enzymes. In the case of TIM, structural dynamics are known to be essential to function. In particular the stabilization of the binding pocket by a phosphodianion “handle” of the substrate and the closing of catalytic site loops 6 and 7 over the substrate. Loop 6 moves by as much as 7 Angstroms with binding. Recently a mutant survey for human TIM (hsTIM) found kcat can change significantly for a single mutation distant from the catalytic site. Crystallographic measurements find no structural change with the mutation, suggesting a dynamical mechanism for the allosteric effect. Here we use Stationary Sample Anisotropic Terahertz Microscopy (SSATM) to measure the long-range intramolecular vibrations and determine if specific vibrations couple the allosteric and catalytic sites. SSATM isolated protein long-range structural vibrations based on the dominant displacement direction [1-4]. We examine if specific vibrational bands are associate with loop 6 and loop 7 flexibility.
10aBiophysics1 aMcKinney, J., A.1 aDeng, Y., T.1 aGeorge, D., K.1 aRichard, J.1 aMarkelz, A., G. uhttps://markelz.physics.buffalo.edu/node/25201840nas a2200313 4500008004500000020001400045245009000059210006900149260000800218300000600226490000700232520100400239653001501243653001201258653001701270653000801287653001301295653002801308653001001336653001201346653002401358653001701382653001001399100001701409700001701426700001401443700002001457856004901477 2005 Engldsh a1539-375500aLarge oxidation dependence observed in terahertz dielectric response for cytochrome c0 aLarge oxidation dependence observed in terahertz dielectric resp cOct a40 v723 aFar 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.
10aabsorption10abinding10aconformation10adna10adynamics10aheart ferricytochrome-c10amodes10aPhysics10aprotein flexibility10aspectroscopy10astate1 aChen, J., Y.1 aKnab, J., R.1 aCerne, J.1 aMarkelz, A., G. uhttps://markelz.physics.buffalo.edu/node/263