Analytic Representations of Bath Correlation Functions for Ohmic and Superohmic Spectral Densities Using Simple Poles

We present a scheme to express a bath correlation function (BCF) corresponding to a given spectral density (SD) as a sum of damped harmonic oscillations. Such a representation is needed, for example, in many open quantum system approaches. To this end we introduce a class of fit functions that enables us to model ohmic as well as superohmic behavior. We show that these functions allow for an analytic calculation of the BCF using pole expansions of the temperature dependent hyperbolic cotangent. We demonstrate how to use these functions to fit spectral densities exemplarily for cases encountered in the description of photosynthetic light harvesting complexes. Finally, we compare absorption spectra obtained for different fits with exact spectra and show that it is crucial to take properly into account the behavior at small frequencies when fitting a given SD.Comment: 16 pages, 9 figure

Non-Markovian Quantum State Diffusion for Temperature-Dependent Linear Spectra of Light Harvesting Aggregates

Non-Markovian Quantum State Diffusion (NMQSD) has turned out to be an efficient method to calculate excitonic properties of aggregates composed of organic chromophores, taking into account the coupling of electronic transitions to vibrational modes of the chromophores. NMQSD is an open quantum system approach that incorporates environmental degrees of freedom (the vibrations in our case) in a stochastic way. We show in this paper that for linear optical spectra (absorption, circular dichroism) no stochastics is needed, even for finite temperatures. Thus, the spectra can be obtained by propagating a single trajectory. To this end we map a finite temperature environment to the zero temperature case using the so-called thermofield method. The resulting equations can then be solved efficiently by standard integrators.Comment: 14 pages, 4 figure

Absence of Quantum Oscillations and Dependence on Site Energies in Electronic Excitation Transfer in the Fenna–Matthews–Olson Trimer

Energy transfer in the photosynthetic Fenna–Matthews–Olson (FMO) complex of green sulfur bacteria is studied numerically taking all three subunits (monomers) of the FMO trimer and the recently found eighth bacteriochlorophyll (BChl) molecule into account. The coupling to the non-Markovian environment is treated with a master equation derived from non-Markovian quantum state diffusion. When the excited-state dynamics is initialized at site eight, which is believed to play an important role in receiving excitation from the main light harvesting antenna, we see a slow exponential-like decay of the excitation. This is in contrast to the oscillations and a relatively fast transfer that usually occurs when initialization at sites 1 or 6 is considered. We show that different sets of electronic transition energies can lead to large differences in the transfer dynamics and may cause additional suppression or enhancement of oscillations.Chemistry and Chemical Biolog

Suppression of quantum oscillations and the dependence on site energies in electronic excitation transfer in the Fenna-Matthews-Olson trimer

Energy transfer in the photosynthetic complex of the Green Sulfur Bacteria known as the Fenna-Matthews-Olson (FMO) complex is studied theoretically taking all three subunits (monomers) of the FMO trimer and the recently found eighth bacteriochlorophyll (BChl) molecule into account. We find that in all considered cases there is very little transfer between the monomers. Since it is believed that the eighth BChl is located near the main light harvesting antenna we look at the differences in transfer between the situation when BChl 8 is initially excited and the usually considered case when BChl 1 or 6 is initially excited. We find strong differences in the transfer dynamics, both qualitatively and quantitatively. When the excited state dynamics is initialized at site eight of the FMO complex, we see a slow exponential-like decay of the excitation. This is in contrast to the oscillations and a relatively fast transfer that occurs when only seven sites or initialization at sites 1 and 6 is considered. Additionally we show that differences in the values of the electronic transition energies found in the literature lead to a large difference in the transfer dynamics

An efficient method to calculate excitation energy transfer in light harvesting systems. Application to the FMO complex

A master equation, derived from the non-Markovian quantum state diffusion (NMQSD), is used to calculate excitation energy transfer in the photosynthetic Fenna-Matthews-Olson (FMO) pigment-protein complex at various temperatures. This approach allows us to treat spectral densities that contain explicitly the coupling to internal vibrational modes of the chromophores. Moreover, the method is very efficient, with the result that the transfer dynamics can be calculated within about one minute on a standard PC, making systematic investigations w.r.t. parameter variations tractable. After demonstrating that our approach is able to reproduce the results of the numerically exact hierarchical equations of motion (HEOM) approach, we show how the inclusion of vibrational modes influences the transfer

TGT a Drug Target to Study pKa Shifts, Residual Solvation & Protein-Protein Interface Formation

In this thesis multiple computer aided methods of structure based drug design along with X-ray crystallography and kinetic measurements were used to investigate inhibitors of tRNA-guanine transglycosylase (TGT) a putative target for a new specific antibiotic against Shigella bacteria. Within a year about 160 million infections are reported leading to approximately 1 million deaths, predominantly in developing. The crystallization of Z. mobilis TGT, which offers a nearly identical active site as TGT from S. flexneri, was successfully performed in previous studies. Several scaffolds based on pyridazinones, pteridines, and quinazolinones were discovered with binding affinities in the micro molar range. In addition, a “stretched” guanine with an inserted central six-membered ring, leading to lin-benzoguanine (3 µM), was discovered and further evaluated in this thesis. During the optimization process of the lin-benzoguanine skeleton two often neglected aspects of ligand binding to a protein are highlighted: (i) pKa shifts are studied once the inhibitor is transferred from aqueous solution to a protein environment and (ii) the influence of residual solvation of amino acids in the active site are investigated during the site chain design of the parent skeleton. The decoration of the lin-benzoguanine with new side chains delivered binding affinities in the low nano molar range (best 2 nM). In addition, the constitution of the catalytic active complex of TGT and its substrate-tRNA was studied, applying site directed mutagenesis, kinetic measurements and nanoESI-MS experiments. Based on a crystal structure of TGT with a tRNA-stem loop we suggested that TGT is active as a homo dimer and can bind one tRNA molecule for catalysis. The obtained results confirmed that TGT is a homo dimer and binds one tRNA molecule

C-Tactile Mediated Erotic Touch Perception Relates to Sexual Desire and Performance in a Gender-Specific Way

Background: Unmyelinated low-threshold mechanoreceptors-the so-called C-tactile (CT) afferents-play a crucial role in the perception and conduction of caressing and pleasant touch sensations and significantly contribute to the concept of erotic touch perception. Aim: To investigate the relations between sexual desire and sexual performance and the perception of touch mediated by CT afferents. Methods: Seventy healthy participants (28 men, 42 women; mean age+/-SD = 24.84+/-4.08 years, range = 18-36 years) underwent standardized and highly controlled stroking stimulation that varied in the amount of CT fiber stimulation by changing stroking velocity (CT optimal = 1, 3 and 10 cm/s; CT suboptimal = 0.1, 0.3, and 30 cm/s). Participants rated the perceived pleasantness, eroticism, and intensity of the applied tactile stimulation on a visual analog scale, completed the Sexual Desire Inventory, and answered questions about sexual performance. Outcomes: Ratings of perceived eroticism of touch were related to self-report levels of sexual desire and sexual performance. Results: Pleasantness and eroticism ratings showed similar dependence on stroking velocity that aligned with the activity of CT afferents. Erotic touch perception was related to sexual desire and sexual performance in a gender-specific way. In women, differences in eroticism ratings between CT optimal and suboptimal velocities correlated positively with desire for sexual interaction. In contrast, in men, this difference correlated to a decreased frequency and longer duration of partnered sexual activities. Clinical Implications: The present results lay the foundation for future research assessing these relations in patients with specific impairments of sexual functioning (eg, hypoactive sexual desire disorder). Strengths and Limitations: The strength of the study is the combination of standardized neurophysiologic methods and behavioral data. A clear limitation of the study design is the exclusion of exact data on the female menstrual cycle and the recruitment of an inhomogeneous sample concerning sexual orientation. Conclusion: The present results provide further evidence that unmyelinated CT afferents play a role in the complex mechanism of erotic touch perception. The ability to differentiate between CT optimal and suboptimal stimuli relates to sexual desire and performance in a gender-specific way. Copyright (C) 2017, International Society for Sexual Medicine. Published by Elsevier Inc. All rights reserved

Intensive Expositionsbehandlung bei Angststörungen in einem spezialisierten tagesklinischen Versorgungssetting

Hintergrund: Angststörungen sind häufig, oft chronifizierend, jedoch auch gut behandelbar. Leitlinienbehandlung ist die auf Exposition fokussierende Verhaltenstherapie. In der ambulanten Versorgungspraxis finden Expositionen jedoch selten statt. Die Angst-Tagesklinik am Universitätsklinikum Dresden realisiert die evidenzbasierte Behandlung von Angststörungen. In einer 5-wöchigen Kurzzeitbehandlung werden wöchentlich 4 begleitete und zeitoffene Expositionssitzungen durchgeführt. Untersucht wurden die Symptomverläufe und die Responder-Raten. Methoden: Zu Therapieaufnahme und -ende sowie zur Katamnese nach 3 Monaten und 1 Jahr wurde die Entwicklung der Symptombelastung bei n = 332 PatientInnen untersucht, die von 2009 bis 2015 behandelt wurden. Etwa zwei Drittel waren psychotherapeutisch vorbehandelt. Eingesetzt wurden spezifische etablierte Fragebögen. Berechnet wurden Mixed Models, Effektstärken und Responder-Raten. Ergebnisse: 90% der PatientInnen schlossen die Behandlung regulär ab. Es zeigten sich signifikante Linderungen bei Belastungen durch Angst- und depressive Symptome. Die höchsten Effektstärken um 0,9 ergaben sich bei verhaltensbezogenen Skalen und besonders bei den Agoraphobien und Panikstörungen, die die größte Störungsgruppe ausmachen. Die Responseraten lagen bei 60%. Zu den Katamnesezeitpunkten waren die Symptomverbesserungen stabil und bei den kognitiven Symptomen weiter steigend. Schlussfolgerungen: Die Behandlung in spezialisierten (teil)stationären Versorgungssettings mit Fokus auf hochfrequente Exposition, wie hier beispielhaft vorgestellt, zeigt eine gute Akzeptanz und gute bis sehr gute und längerfristig stabile Veränderungen der Symptombelastung. Diese Settings erfordern eine besondere strukturelle Ausstattung und Ressourcen.Intensive Exposure-Based Treatment of Anxiety Disorders in a Specialized Patient-Centered Day Hospital Background: Anxiety disorders are highly prevalent, often chronic, but effectively treatable by cognitive-behavioral therapy, especially by exposure therapy. However, exposure treatments rarely occur in outpatient healthcare. The day hospital for anxiety disorders at the University Hospital Dresden implemented an evidence-based treatment. Every week, 4 guided time-open exposure sessions, not timelimited, are conducted during the 5-week treatment period. Improvements in symptomatology and response rates were examined. Methods: The symptomatology of n = 332 patients, treated from 2009 till 2015, was assessed at pretreatment and posttreatment, and at the follow-ups after 3 months and 1 year. Two-thirds had previously had other psycho therapy treatments. Established questionnaires were used. Data was analyzed by calculating mixed models, effect sizes, and response rates. Results: 90% of the patients finished the treatment regularly. Significant improvements occurred in anxiety and depressive symptoms. The strongest effect sizes of about 0.9 were achieved for behavioral scales, especially for symptoms of agoraphobia and panic disorder, the most frequent disorders in the sample. The response rates were 60%. Improvements remained stable at the follow-ups and even increased further for cognitive symptoms. Conclusions: Specialized day hospital healthcare settings, like the one presented here, are associated with good to very good and stable improvements and also with good acceptance. These therapeutic settings require specific structural equipment and resources