Protontranszfer fehérjében. = Protein controlled proton transfer.

A protonok vezetése kulcsfontosságú számos membrán-csatorna és energiaátalakító fehérje működésében. A fotoszintetizáló baktériumok reakciócentrumával elvégzett vizsgálatainkból kiindulva próbáltuk megérteni azokat az alapelveket, amelyeket a Természet alkotott, és használ a nagy hatótávolságú protontranszfer során. Megértettük, hogy a protonokat a hidrogen-hídakkal hálózatba szerveződött aminosavak és protonált vízmolekulák (Eigen- és Zünder-ionok) veszik fel, vezetik és adják le a fehérje jól meghatározott részein. Az ilyen hálózatok képesek a protonokat időlegesen tárolni is, és szükség esetén innen felhasználni ("proton-szivacs" koncepció). A proton-klaszter elemei között nagy (60 meV) a kölcsönhatási energia , és ezek együttesen, nem-kooperatív módon veszik fel (adják le) a protonokat. Kimutattuk, hogy ez a proton-hálózat az egész citoplazmikus térrészre kiterjed. Ez a szerveződés és működési elv általános lehet az élőlényekben, mert hasonló protonvezetés figyelhető meg más energia-átalakító fehérjében is (bakteriorodopszin, citokróm c oxidáz, emberi szén anhidráz stb.). A protonok a fehérje jól meghatározott proton-kapuin keresztül vétetnek fel, ill. adódnak le, amely kapukat és protonvezetési utakat a fehérje elektrosztatikája és mozgása (dinamikája) irányítja. A munkánk eredményeivel közelebb jutottunk annak megértéséhez, milyen elvek alapján működik élő rendszerben a protonvezetés, és esélyt látunk arra, hogy ennek felhasználásával mesterségesen protonvezetési molekuláris rendszereket tervezzünk. | Transfer and transport of protons are key processes in several membrane channels and bioenergetic proteins. Based on studies of light-induced proton uptake and release in reaction center (RC) protein of photosynthetic bacteria, an attempt is made to draw some conclusions about how Nature designs long distance, proton transport functionality. The proton is conducted through hydrogen bonded chains of amino acids and protonated water (Zündel and Eigen ions) and can be even stored in this network (?proton sponge?) for later use. The interaction energy among the constituents of the cluster is larger (in the range of 60 meV) than supposed earlier by electrostatic calculations and FTIR measurements. The uptake and conduction of protons in the cluster are collective and non-cooperative process. The network extends through the whole cytoplasmic side of the RC protein. We prefer the prevalence of protonated water rather than amino acid hydrogen bonded chains in the proton conduction as revealed by investigations of numerous site directed mutants of the RC and other proton (water) translocating biomolecules like (aquaporin), bacteriorhopsin, cytochrome c oxidase and human carbonic anhydrase. We could demonstrate that the uptake and release of protons occurred through well defined gates and could be controlled (facilitated or blocked) by electrostatics and dynamics of the protein. We came closer to understand the design of the natural system and got the chance to start to construct artificial proton translocating molecular systems

Lézerek az optikában, spektroszkópiában és az anyagtudományokban = Lasers in optics, spectroscopy and material sciences

Ezen pályázat eredményei az SzTE Fizika Doktori Iskola négy tudományos részterületén (femtoszekundumos optika, lézerek anyagtudományi alkalmazása, valamint csillagászati- és fotoakusztikus spektroszkópia) dolgozó kollektíva egymással összefüggő, azt kiegészítő tudományos munkája révén jöttek létre, melyek főbb eredményei a következőek: Egy új, csak lineáris optikai eljárást fejlesztettünk ki lézerimpulzusok hordozó-burkoló fázis csúszásának mérésére, mely független a hullámhossztól és a sávszélességtől. Immerziós, két-nyalábos interferenciás lézerindukált hátsóoldali nedves maratási eljárást alkalmazva 104 nm periódusú kvarc rácsot készítettünk. A lézerrel generált fém-dielektrikum rácsok periódikus adhézió- és plazmon-mező modulációján alapuló új SPR bio-szenzorizációs eljárást dolgoztunk ki. Folyadékok ultrarövid impulzusokkal történő ablálásával kontrollált méreteloszlású és összetételű nanorészecskék előállításának új módszerét dolgozták ki. AFM fejlesztés során egy új amplitúdó és fázismérési algoritmust dolgoztunk ki, amely egyetlen rezgésből is képes az amplitúdó és fázis meghatározására. Kifejlesztettünk egy lézeres ammóniamérő műszert, amely alkalmas koncentráció és fluxus nagyérzékenységű, automatikus mérésére, terepi körülmények között. Nagyfelbontású spektroszkópiával kimutattuk, hogy két módusban rezgő csillagokban a nagyobb fémtartalmúaknál a rezgési periódusok aránya kisebb. | The results of this project have been achieved by the co-operative work of colleagues from four scientific fields of the Physics PhD Program of the University of Szeged, as femtosecond optics, laser-matter (surface) interactions, photoacoustical and astronomical spectroscopy. The major findings of these basic researches are as follows: A new linear optical method was developed for the measurement of the carrier envelope phase drift of laser pulses, which is independent of the wavelength and bandwidth. Immersion two-beam interferometric laser induced backside wet etching method was applied to prepare fused silica gratings with a 104 nm period. Novel SPR bio-sensing method was developed based on the periodic adhesion and plasmon-field enhancement on the laser-induced metal-dielectric gratings. It has been demonstrated that ultrashort pulse ablation of liquids is a novel approach to the production of nanoparticles of controlled composition and size distribution. A new amplitude and phase measurement algorithm for AFM was developed, which allows the determination of phase and amplitude from one vibration of the tip. We have developed a laser based instrument for accurate and automatic ammonia concentration and flux monitoring under field conditions. From high-resolution spectroscopy we pointed out that in double-mode pulsating stars the ones with higher metallicities have lower period ratios

All-Optical Experimental Control of High-Harmonic Photon Energy

We generate high-order harmonics in gaseous medium with tunable photon energy using time domain interferometry of double pulses in a non-collinear generation geometry. The method is based on the fact that the generated harmonics inherit certain spectral properties of the driving laser. The two temporally delayed ultrashort laser pulses, identical in all parameters, are produced by a custom-made split-and-delay unit utilizing wave front splitting without a significant energy loss. The arrangement is easy to implement in any attosecond pulse generation beamline, and is suitable for the production of an extreme ultraviolet source with simply and quickly variable central photon energy, useful for a broad range of applications.Comment: 6 pages, 5 figures, after peer-revie

Laser-induced inner-shell excitations through direct electron re-collision versus indirect collision

The dynamics and the decay processes of inner-shell excited atoms are of great interest in physics, chemistry, biology, and technology. The highly excited state decays very quickly through different channels, both radiative and non-radiative. It is therefore a long-standing goal to study such dynamics directly in the time domain. Using few-cycle infrared laser pulses, we investigated the excitation and ionization of inner-shell electrons through laser-induced electron re-collision with the original parent ions and measured the dependence of the emitted x-ray spectra on the intensity and ellipticity of the driving laser. These directly re-colliding electrons can be used as the initiating pump step in pump/probe experiments for studying core-hole dynamics at their natural temporal scale. In our experiment we found that the dependence of the x-ray emission spectrum on the laser intensity and polarization state varies distinctly for the two kinds of atomic systems. Relying on our data and numerical simulations, we explain this behavior by the presence of different excitation mechanisms that are contributing in different ratios to the respective overall x-ray emission yields. Direct re-collision excitation competes with indirect collisions with neighboring atoms by electrons having "drifted away" from the original parent ion. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreemen

Spectrally tunable ultrashort monochromatized extreme ultraviolet pulses at 100 kHz

We present the experimental realization of spectrally tunable, ultrashort, quasimonochromatic extreme ultraviolet (XUV) pulses generated at 100 kHz repetition rate in a user-oriented gas high harmonic generation (GHHG) beamline of the Extreme Light Infrastructure - Attosecond Light Pulse Source (ELI ALPS) facility. Versatile spectral and temporal shaping of the XUV pulses are accomplished with a double-grating, time-delay compensated monochromator accommodating the two composing stages in a novel, asymmetrical geometry. This configuration supports the achievement of high monochromatic XUV flux (2.8e10+/-0.9e10 photons/s) combined with ultrashort pulse duration (4.0+/-0.2 fs using 12.1+/-0.6 fs driving pulses) and small spot size (sub-100 um). Focusability, spectral bandwidth, and overall photon flux of the produced radiation were investigated covering a wide range of instrumental configurations. Moreover, complete temporal (intensity and phase) characterization of the few-femtosecond monochromatic XUV pulses - a goal that is difficult to achieve by conventional reconstruction techniques - has been realized using ptychographic algorithm on experimentally recorded XUV-IR pump-probe traces. The presented results contribute to in-situ, time-resolved experiments accessing direct information on the electronic structure dynamics of novel target materials.Comment: 20 pages, 8 figure

High-Flux 100 kHz Attosecond Pulse Source Driven by a High-Average Power Annular Laser Beam

High-repetition rate attosecond pulse sources are indispensable tools for time-resolved studies of electron dynamics, such as coincidence spectroscopy and experiments with high demands on statistics or signal-to-noise ratio, especially in the case of solid and big molecule samples in chemistry and biology. Although with the high-repetition rate lasers, such attosecond pulses in a pump-probe configuration are possible to achieve, until now, only a few such light sources have been demonstrated. Here, by shaping the driving laser to an annular beam, a 100 kHz attosecond pulse train (APT) is reported with the highest energy so far (51 pJ/shot) on target (269 pJ at generation) among the high-repetition rate systems (>10 kHz) in which the attosecond pulses were temporally characterized. The on-target pulse energy is maximized by reducing the losses from the reflections and filtering of the high harmonics, and an unprecedented 19% transmission rate from the generation point to the target position is achieved. At the same time, the probe beam is also annular and low loss of this beam is reached by using another holey mirror to combine with the APT. The advantages of using an annular beam to generate attosecond pulses with a high-average power laser are demonstrated experimentally and theoretically. The effect of nonlinear propagation in the generation medium on the annular-beam generation concept is also analyzed in detail