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Structure-function analysis of the small heat shock protein sequestrase Hsp42 from Saccharomyces cerevisiae
No full textCells have evolved a complex network of mechanisms to maintain protein homeostasis.
Among these, protein sequestration executed by small heat shock proteins (sHsps) serves as a
strategy to prevent deleterious aggregation by capturing misfolded proteins into complexes
that remain amenable to disaggregation by ATP-dependent chaperones. The size and
morphology of these complexes are determined by the sHsp involved, the substrate, and the
aggregation conditions. Some sHsps form only small, soluble assemblies (holdase activity),
while others additionally generate large, microscopically visible inclusions (aggregase
activity). The precise mechanisms governing the architecture of these complexes remain
incompletely understood.
In this study, I investigated the structure and function of the Saccharomyces cerevisiae sHsp
Hsp42, which exhibits both holdase and aggregase activities. Hsp42 is distinguished from
other sHsps by an extended intrinsically disordered N-terminal region, which comprises a
prion-like domain (PrLD) and a classical intrinsically disordered domain (IDD), defined by
their amino acid composition. To dissect the structural organization of Hsp42, I employed a
combination of biophysical, microscopic, and computational approaches. My data reveal that
Hsp42 assembles into a range of oligomeric states, from dimers to decamers, with octamers
being the predominant species. This oligomerization is dynamic and responsive to
environmental triggers such as temperature and pH. Additionally, Hsp42 undergoes extremely
rapid subunit exchange, a feature critical for its chaperone function.
Structural modeling predicts that Hsp42 forms planar ring-like octamers made of folded
domains, flanked by disordered regions extending outward. This novel arrangement of ACDs
in sHsp was never reported in other sHsps. This model was partially validated by cross-linking
mass spectrometry, which identified proximity regions within the oligomer, and by limited
proteolysis coupled to mass spectrometry, which identified exposed and protected regions.
I further demonstrate that Hsp42 forms substrate-dependent complexes of varying size. Cross�linking mass spectrometry identified multiple substrate-binding regions within Hsp42.
Importantly, my findings confirm that Hsp42 and bound substrate are not passively released
from these complexes and that complex dissolution requires the coordinated action of the
Hsp70/Hsp40/Hsp100 disaggregation machinery.
Finally, I dissected the contributions of PrLD, IDD, and other domains and conserved motifs
of Hsp42 to substrate sequestration and recovery. Using a series of deletion and point mutants,
I show that distinct domains of Hsp42 mediate substrate interaction and complex formation,
with the PrLD playing a central role – its deletion markedly reduced chaperone activity. In
contrast, other domains are required for efficient substrate handover to the disaggregase
system. The IDD was found to be essential for forming large Hsp42-substrate complexes and
to confer temperature-dependent aggregase activity. Moreover, the IDD appears to influence
complex architecture in a manner that facilitates access by Hsp70, while blocking access by
standalone Hsp100 disaggregase
Investigating the Specificity of Mindfulness and Self-Compassion:Effects, Mechanisms, and Implications for Mental Health Promotion
No full textMindfulness and self-compassion have played a central role in recent mental health promotion efforts, with interventions demonstrating beneficial effects, both by reducing psychological ill-being and enhancing psychological well-being, across diverse populations and settings. However, these constructs face conceptual ambiguities, and fundamental questions about outcome specificity and underlying change mechanisms remain. This dissertation will address important research gaps pertaining to the examination of mindfulness and self-compassion across different conceptualizations—as practices, interventions, predictors, and mechanisms of change—through three empirical studies with diverse samples and methodologies. This work aims to contribute to a clearer understanding of when these approaches yield specific versus broad effects and through which processes change occurs in non-clinical populations.
To this end, in Chapters 2 and 3 of this dissertation, I present findings of two complementary randomized controlled trials that examine specific and broad effects of two mental health promotion interventions designed for healthy adults of different durations and delivery modes. More specifically, Chapter 2 evaluates a brief online, self-guided self-compassion training compared to an active control in a German convenience sample (N = 200; 85.5% female; Mage = 30 years; range 18-69 years) with a 4-week follow-up. Findings indicate similar improvements in self-compassion, self-criticism, perfectionism, and psychological well-being across both conditions, with self-compassion-specific training effects emerging only for highly self-critical individuals.
Chapter 3 examines an 8-week in-person, trainer-led socioemotional competence training targeting stress management and social competences in younger and older German adults (N = 166; 75.2% female; Mage = 46.26 years; range 19-39 and 50-78 years). Compared to a waitlist control group, specific effects only emerged on directly trained outcomes (i.e., mindfulness, perceived stress). They did, however, not spill over to broader domains, such as self-compassion and other indicators of emotional and social functioning. Still, most training effects persisted across 3- and 12-month follow-up.
Chapters 4 and 5 focus on potential mechanisms of mindfulness and self-compassion, examining state-trait relationships and self-referential processes more closely. Building on the same dataset as the study presented in Chapter 3, results of Chapter 4 revealed that despite significant improvements in state and trait indicators, state mindfulness changes did not predict trait-level changes in mindfulness, self-compassion, and perceived stress.
Chapter 5 presents data from a binational longitudinal study (NT1 = 615; NT2 = 310; 51.5% female; age range 18–84 years) on the relationship of mindfulness and self-compassion with self-evaluative processes. Results demonstrate that both mindfulness and self-compassion predicted reduced comparison frequency and more favorable comparison outcomes but not perceived comparison utility. These findings point to potential differences in self-referential processes, that is, differences in how more mindful and self-compassionate people perceive and relate to self-relevant information.
This systematic investigation underlines that mindfulness and self-compassion interventions yield both specific and broad effects and that intervention framing and design may affect the outcome specificity. Furthermore, the dissertation highlights the importance of distinguishing between actual state or trait change and changes in self-referential processes. Collectively, these findings underscore the need for precision-oriented approaches that consider individual characteristics, intervention framing, and the complex interplay between behavioral change and self-perception in future mental health promotion efforts
„Nukleares Naturschutzgebiet“ im Süd-Ural: Atommüllkatastrophen und Strahlenschutz in der Sowjetunion
No full textDie Arbeit untersucht die Entstehung und Entwicklung des Strahlenschutzes sowie den Umgang mit radioaktiver Kontamination im Süd-Ural während der frühen Phase der Anwendung des Atoms (1940er–1960er Jahre) in der Sowjetunion. Am Beispiel der Katastrophen rund um das Atomprojekt Majak werden die politischen, institutionellen und wissenskulturellen Dynamiken analysiert, die das sowjetische Katastrophenmanagement, die Regulierung radioaktiver Gefahren und die Wissensproduktion über Strahlenrisiken prägten. Im Fokus stehen dabei die Wechselwirkungen zwischen militärischer und ziviler Sphäre, der Aufbau regionaler und zentraler Infrastrukturen, die Rolle von Erfahrungs- und Alltagswissen sowie die soziale Dimension des Strahlenschutzes. Die Untersuchung zeigt, wie wissenschaftliches Erfahrungswissen, institutionelle Interessen und Geheimhaltung die Wahrnehmung, Bewertung und Bewältigung atomarer Risiken beeinflussten. Die Arbeit leistet einen Beitrag zur Wissenschafts- und Technikgeschichte der sowjetischen Anwendung des Atoms, beleuchtet die Folgen für betroffene Bevölkerungsgruppen und diskutiert die sowjetische Inszenierung des Strahlenschutzes im internationalen Kontext
Behavioral and Molecular Mechanisms of Cocaine Addiction Vulnerability: Functional Evidence from Rodent Models
No full textCocaine addiction is a complex, chronically relapsing disorder shaped by individual vulnerability, neuroadaptive changes, and limited treatment options. Although substantial progress has been made in understanding the reinforcing properties of psychostimulants, the neurobehavioral mechanisms distinguishing recreational use from compulsive, addiction-like behavior remain incompletely understood. This thesis aimed to (i) identify behavioral phenotypes predictive of addiction vulnerability, (ii) examine molecular adaptations underlying compulsive drug use, and (iii) evaluate the therapeutic potential of pharmacological interventions using translationally-relevant rodent models.
The first objective focused on phenotypic predictors of addiction-like behavior. In Study 1A, the role of incentive salience attribution, measured through Pavlovian Conditioned Approach behavior, was evaluated within the 3-CRIT model of cocaine addiction. Contrary to the expectations of incentive sensitization theory, sign- and goal-tracking phenotypes failed to predict the development of addiction-like behavior. However, sign-trackers exhibited greater resistance to punishment. Study 1B examined sex differences in the 3-CRIT model. Although fewer females met the addiction-like criteria, those that did (i.e., “3crit” rats) exhibited more severe behavioral profiles despite lower overall drug intake. These findings highlight the importance of both sex and individual phenotype in modeling addiction vulnerability.
The second aim addressed the molecular mechanisms of addiction. In Study 2A, cocaine self-administration dynamically regulated the expression of metabotropic glutamate receptor 2 (mGluR2 , gene: Grm2) across cortico-striatal pathways. Extinction training, but not abstinence, robustly upregulated Grm2 expression, and pharmacological activation of mGluR2/3 with LY379268 suppressed cue-induced cocaine seeking. Changes in mGluR2 expression followed a region- and experience-specific pattern: initial downregulation was observed in the prelimbic cortex after short-term exposure, shifting to the infralimbic cortex with prolonged cocaine use. Interestingly, addiction-vulnerable animals (3crit), despite comparable drug intake to 0crit animals, showed elevated Grm2 levels in the infralimbic
cortex and dorsal striatum, likely reflecting compensatory responses. In Study 2B, a genetic dopamine transporter (DAT) impairment (Slc6a3_N157K) prevented the acquisition
and maintenance of cocaine self-administration, emphasizing the necessity of intact DAT function for cocaine reinforcement.
The final part evaluated novel pharmacological interventions and methodological refinements. In Study 3A, the effects of psilocybin on extinction learning and cue-induced rein-
statement in cocaine-experienced rats and mice were examined. Although behavioral outcomes were not significantly altered, the study provided important insight into the feasibility and limitations of applying psychedelic-based interventions in preclinical addiction models. In Study 3B, a rat adaptation of a mouse-based paradigm intended to assess reality testing was developed. While mediated aversion failed to emerge, direct aversion was consistently observed, underscoring both the challenges of cross-species translation and the importance of refining behavioral tools to probe drug-induced changes in cognition.
In summary, this thesis advances understanding of the behavioral, molecular, pharmacological, and methodological factors underlying cocaine addiction. By integrating phenotypic variability, sex differences, and molecular adaptations in glutamatergic and dopaminergic systems, together with exploratory evaluations of serotonergic psychedelics and refined behavioral paradigms, the work underscores the multifaceted nature of addiction vulnerability and the limitations of oversimplified models. Region- and experience-specific regulation of Grm2 expression highlights dynamic glutamatergic plasticity associated with different stages of cocaine exposure and withdrawal. Additionally, the demonstration that impaired
DAT function disrupts the acquisition and maintenance of cocaine self-administration emphasizes the necessity of intact dopaminergic signaling for cocaine reinforcement. Finally, the evaluation of psilocybin, together with efforts to refine cognitive assays, illustrates both therapeutic opportunities and methodological challenges. Together, these findings reinforce the need for refined preclinical approaches in addiction research
Quantum-Chemical Investigations In Homogeneous Catalysis
No full textThis thesis describes examples of the use of quantum-chemical calculations to investigate reaction mechanisms in homogeneous catalysis. Four projects are examined: two illustrate catalysis by main group elements and two focus on transition metal catalysis.
In the first project, an organocatalytic isomerization of exo- to endo-vinylene carbonates was investigated. The catalyst system is a mixture of an organic base and phenol. Density functional theory (DFT) calculations revealed a ring-opening mechanism with a ring-opened ketone intermediate, which is experimentally isolable. For substrates bearing an aryl substituent, a ring-retaining pathway is accessible as well, which proceeds without the involvement of phenol. Based on this knowledge, a control experiment was designed, yielding further evidence for the ring-opening mechanism.
The second project focused on the mechanistic investigation of a Cu(II)-catalyzed aniline synthesis from aryl chlorides in aqueous ammonia. DFT investigations showed that deprotonation of an initial Cu(II)-ammine complex yields the active form of the catalyst, a Cu(II)-amido complex. The aniline formation proceeds via a nucleophilic aromatic substitution mechanism. Product liberation proceeds by subsequent ligand exchanges. These results led to the design of spectroscopic control experiments, giving indications for the deprotonated Cu(II)-amido complex.
In the third project, the reaction of acetylene with formaldehyde was investigated, selectively yielding propargyl alcohol while suppressing the second reaction to butynediol. Optimization studies established a Cu(I) catalyst with a cheap and air-stable phenanthroline ligand. Quantum-chemical investigations on phenylacetylene conducted in this work suggest that the reaction mechanism is preferably mediated by a mononuclear active species. The mechanism was transferred to the acetylene system. Kinetic modeling indicated that the selectivity to propargyl alcohol primarily results from concentration effects.
The fourth project describes computational studies for a bismuth-catalyzed C−N coupling. Experimentally, a mixture of a C−N and a C−O coupled product was observed, where the selectivity depends on the catalyst. Detailed DFT studies showed that the reductive elimination is the selectivity-determining step. Multiple pathways were found for the reductive elimination, with the energetic order depending on the catalyst.
Statistical modeling was performed to achieve an interpretable multivariate linear regression model. The model enabled the analysis of how ligand electronic and steric properties affect reductive elimination by stabilizing a cationic substructure
Functionalized and Conformationally Stable Monkey Saddles as Building Blocks for Organic Cages
No full textOrganic cages are well-defined molecular entities with internal cavities that facilitate a variety of applications, including the separation and storage of chemicals, in particular of gases. In this dissertation, triptycene and so-called monkey saddles – truxene-based, negatively curved polycyclic aromatic hydrocarbons in which three pentagons are fused with three octagons – were explored as building blocks for the construction of shape-persistent organic cages by alkyne metathesis. For triptycene, the previously prepared alkyne metathesis catalyst was initially tested on the generation of the respective hexadehydro[12]annulene cage subunit, and the reversibility of this reaction was scrutinized through scrambling experiments. For the monkey saddle, an alkyne metathesis catalyst screening was performed in collaboration with the Fürstner group at the Max-Planck-Institut für Kohlenforschung. Nevertheless, the racemic nature of the substrate likely impeded successful cage formation, while its configurational instability under alkyne metathesis reaction conditions simultaneously precluded the use of enantiopure material.
This challenge motivated the second major goal of this thesis: the development of conformationally stable, functionalized monkey saddles. Building on the inversion stability observed for the so-called chromene monkey saddle, both post- and pre-functionalization strategies were pursued. Moreover, the results of different computational methods were benchmarked against experimental data to reliably predict the barrier heights of monkey saddles. This computational study further revealed that substitution at either the cyclooctatetraene or benzene units could significantly increase the inversion barrier. Consequently, diverse synthetic approaches were explored, whereby functionalization of the benzene rings was ultimately achieved, and the target compound’s racemization behavior was experimentally analyzed.
The introduction of this specific substitution pattern also led to the isolation of a compound, in which the intramolecular construction of a dibenzofuran moiety forced the adjacent cyclooctatetraene ring into planarity. The structure was unambiguously confirmed by single-crystal X-ray diffraction. To gain deeper insight into the formation mechanism, deuterium labeling experiments and quantum-chemical calculations were carried out. Finally, the antiaromatic character of the planar cyclooctatetraene was investigated through a combination of 1H NMR spectroscopy and DFT studies.
Overall, this dissertation explores avenues for the formation of alkyne-based cages and establishes essential synthetic and conceptual fundamentals for the design of conformationally stable, functionalized monkey saddles. These systems represent promising building blocks for the preparation of chiral three dimensional architectures reminiscent of carbon schwarzites
The Role of the Transcription Factor REVERBα in Immunotherapy of Macrophages in Colorectal Cancer
No full textColorectal cancer (CRC) is the second leading cause of cancer-related death, and responses to immune checkpoint therapies remain limited due to the immuno-suppressive tumor microenvironment. Tumor-associated macrophages (TAMs) are playing a crucial role in shaping this environment, with the poliovirus receptor (PVR/CD155)-TIGIT axis representing an immune checkpoint system which suppresses T/NK cell activities. However, the transcriptional mechanisms regulating PVR expression in macrophages still remains poorly understood.
This thesis investigates the role of the circadian nuclear receptor REVERBa (NR1D1) and its regulatory function in macrophage-mediated anti-tumor responses in CRC. Using human CRISPR/Cas9-modified THP1-derived macrophages, PBMC-derived primary macrophages with HT29 cells or patient-derived tumor organoids (PDOs) from patients with CRC in co-culture, we characterized REVERBa expression and its functional impact on macrophage-tumor interactions. Chromatin-immunoprecipitation revealed that REVERBa directly binds to the human PVR gene promoter. Furthermore, pharmacological modulation showed that REVERB SR9009 agonist reduced PVR expression and promoter binding, whereas SR8278 antagonist increased both, highlighting REVERBa as a fine-tunable repressor of immune checkpoint regulation. Notably, CRISPR/Cas9-modification of the human REVERB gene disrupted ligand responsiveness, suggesting an altered or misfolded protein conformation and loss of function. Functional assays further demonstrated that REVERB modulation by gene editing or ligands altered macrophage efferocytosis, phagocytosis as well as cytokine expression. Importantly, combining PVR blocking with macrophages enhanced tumor cell killing in both HT29 and PDO co-cultures, underscoring the translational relevance of these findings.
Altogether, these findings identify REVERBa as a novel regulator of PVR expression and macrophage function in CRC. By linking circadian biology, transcriptional repression and immune checkpoint regulation, this work highlights REVERB as a potential target, supporting future investigations of its modulation in combination with immune checkpoint blockade as a macrophage-focused immunotherapeutic strategy against CRC
Französische Revolutionshelden im deutschsprachigen Erinnerungsraum – Sakralisierung, Emotionalisierung und Ästhetisierung
No full textDer Beitrag untersucht die erinnerungskulturelle Konstruktion französischer Revolutionshelden und -antihelden im deutschsprachigen Raum vom 19. bis zum 21. Jahrhundert. Im Zentrum stehen Prozesse der Sakralisierung, Emotionalisierung und Ästhetisierung, durch die revolutionäre (Anti-)Heldenfiguren politisch funktionalisiert und symbolisch stabilisiert wurden. Anhand der kontrastiven Fallstudien Maximilien Robespierre und Lazare Hoche analysiert der Artikel materielle und immaterielle lieux de mémoire im Sinne Pierre Noras. Unter Rückgriff auf Memory Studies, Public History und Akteur-Netzwerk-Theorie werden heroische Körperbilder, affektive Codierungen und geschlechtsspezifische Zuschreibungen als relationale, historisch wandelbare Bedeutungsnetzwerke rekonstruiert. Der Beitrag zeigt, wie hegemoniale Heroisierungsmodelle transnational adaptiert, transformiert oder unterlaufen werden und welche Rolle subalterne, neuro-queere und postheroische Aneignungen im Umgang mit Gewalt, Männlichkeit und politischem Gedächtnis spielen
Erinnerungspraktiken an Kriegsgräberstätten in der Republik Österreich: Die Gruppe 97 des Wiener Zentralfriedhof im Fokus
No full textDieser Text stellt ein Dissertationsprojekt zu individuellen und kollektiven Gedenkpraktiken auf der größten österreichischen Kriegsgräberstätte des Zweiten Weltkriegs vor, der Gruppe 97 auf dem Wiener Zentralfriedhof. Der Raum wird als materielle Manifestation der österreichischen Erinnerungsnarrative der Nachkriegszeit analysiert, wo individuelle persönliche Trauer mit kollektivem politischem Gedenken zusammentrifft. Auf der theoretischen Grundlage von Public History und Memory Studies untersucht das Projekt die Rollen, Rituale, Medien und Regeln des Gedenkens. Methodisch kombiniert das Projekt Archivforschung, Interviews, ethnografische Feldforschung und Ansätze der Digital Humanities. Es beleuchtet die Spannungen zwischen Uniformität und Heterogenität sowie Fragen nach Täterschaft, Opferbegriffen und nationaler Erinnerungskultur vom Nachkriegsösterreich bis heute
Syntalos: A solution for precise simultaneous multi-modal data acquisition and closed-loop interventions in neuroscience
No full textReliable and reproducible acquisition of multimodal behavioral and neurophysiological data is essential for modern systems neuroscience, but remains technically challenging. Common obstacles include experimenter variability, error-prone device control, consistent (meta)data management, and lack of precise temporal synchronization across heterogeneous hardware that lacks a hardware-based synchronization method.
To address these issues, I developed Syntalos, an open-source, Linux-based, modular software framework for integrated data acquisition and control. Written in C++ with built-in Python extensibility, Syntalos provides a unified interface for diverse data acquisition devices, a standardized layout to store recorded data and metadata for reproducible data management, multiple ways to control hardware for live interactions, and a statistical algorithm for continuous time synchronization across multiple data streams. Validation experiments demonstrated robust long-term time synchronization stability of the statistical algorithm: Electrophysiological recordings, Miniscope calcium imaging, and multi-camera video streams remained synchronized within device sampling tolerances for over 24 h.
To extend calcium imaging capabilities, driver and software improvements for the UCLA Miniscope were implemented, including structural imaging support and a 3D acquisition option, simplifying integration into behavioral experiments.
Modern neuroscience often relies on closed-loop experiments with live interventions during a data acquisition run. Syntalos' roundtrip latencies were sufficient for most closed-loop behavioral experiments. For lower latency needs in the sub-millisecond range, dedicated hardware modules were developed for deterministic responses. In behavior experiments with awake, freely moving mice, Syntalos successfully coordinated calcium imaging, behavioral tracking, and automated reward delivery, enabling precise alignment of neuronal and behavioral data. Additional use cases by independent groups - including multi-camera/Miniscope setups, thalamocortical tactile discrimination tasks, and respiratory rhythm recordings - demonstrated the utility and performance of the software across laboratories and paradigms.
Compared with existing proprietary and open-source solutions, Syntalos is distinguished by its built-in algorithmic synchronization, reproducible storage format, and vendor-independent extensibility. These features establish Syntalos as a robust, scalable platform for complex behavioral neuroscience experiments requiring synchronized multimodal acquisition and closed-loop interventions