Mathematisch-Naturwissenschaftliche Fakultät

Role of the tetraspanin CD151 in the early human papillomavirus type 16 infection cascade

2026-04-10T00:00:00Z

Role of the tetraspanin CD151 in the early human papillomavirus type 16 infection cascade Massenberg, Annika Human papillomaviruses (HPV) are a diverse group of non-enveloped, double-stranded DNA viruses with profound significance in human health. An estimated 5% of all human cancer cases are attributed to HPVs. For infection to occur, virions must reach dividing basal cells of the lower epithelium through a break in the epithelial barrier. On the basement membrane, viral particles bind to their primary attachment site, heparan sulfate (HS) within the extracellular matrix (ECM). This binding triggers a series of conformational changes which promote viral cell entry, with virions migrating along actin-rich protrusions to engage a yet uncharacterized secondary receptor complex on keratinocytes. Current evidence suggests that this secondary receptor is likely a multimeric complex rather than a single molecular entity. Several proteins have been implicated as essential for cell entry, including the tetraspanin CD151, integrin-α6 and growth factor receptors. Among these, CD151 plays a crucial role in facilitating viral access and organizing the cellular components necessary for successful infection. However, this multistep entry process is slow and asynchronous, and involvement of CD151 in HPV entry prior to endocytosis remains unclear.
In this study, HPV16 pseudovirions (PsVs) were used to investigate early infection stages and their association with CD151. PsV/CD151 assemblies were analyzed, revealing that PsVs preferentially bind to regions with increased CD151 density. Overexpression of CD151-GFP induced the formation of large CD151 aggregates, although these aggregates also form independently of PsV binding, indicating that aggregate formation depends on CD151 expression levels.
Furthermore, the actin inhibitor cytochalasin D was employed to synchronize PsV uptake, revealing that actin dynamics within filopodia are crucial for releasing virions from the ECM and transferring them to the cell body. The human keratinocyte cell line HaCaT was validated as an ideal model system for studying early HPV infection events. Inhibition of actin-dependent processes resulted in entrapment of PsVs in the ECM. Upon removal of this blockade, HS-coated PsVs rapidly translocated to the cell body and to CD151 assemblies. After reaching the cell body, the viral capsid sheds its HS coat, followed by PsV/CD151 endocytosis. These findings demonstrate an early involvement of CD151 in HPV16 cell entry.
Moreover, the HSPG-binding peptide 19-2.5 was evaluated for its potential to inhibit PsV infection. While peptide 19-2.5 did not affect PsV/CD151 association, it caused the formation of large viral aggregates several micrometers away from the plasma membrane, indicating a block in the translocation from the primary HSPG attachment site to the secondary receptor complex. This suggests that peptide 19-2.5 may serve as a promising alternative or complement to current HPV prevention strategies.

Experimental setup for a Rydberg atom-mechanical oscillator hybrid system

2026-04-10T00:00:00Z

Experimental setup for a Rydberg atom-mechanical oscillator hybrid system Wind, Cedric Wolff Heinrich Hybrid quantum systems provide a promising route toward combining the complementary strengths of distinct physical platforms for quantum information processing. In this context, highly excited Rydberg atoms are particularly attractive due to their strong electric dipole moments, long lifetimes, and compatibility with both optical and microwave frequency regimes. Mechanical resonators, on the other hand, offer long coherence times and the ability to store quantum information in macroscopic degrees of freedom.
In this thesis, the development of a novel hybrid platform interfacing ultracold Rydberg atoms with high-overtone bulk acoustic wave resonators (HBARs) in a cryogenic environment is presented. The core components of the experimental apparatus have been designed, assembled, and characterized, including a room-temperature realization featuring the complete cold-atom preparation chain. A first-generation superconducting atom chip for trapping ultracold atoms in a cryogenic environment has been designed and fabricated, establishing the foundation for future experiments under cryogenic conditions.
The full experimental realization of the hybrid system, including the integration of the mechanical resonator, was delayed by the delivery of a custom-built cryostat. Nevertheless, the preparation of the cryogenic experiment has been completed, enabling rapid progress toward first experiments once cryogenic operation becomes available. At an operating temperature of 4 K, thermal phonon occupation of HBAR modes is significantly reduced compared to room temperature but remains above the quantum ground state, motivating the development of active cooling strategies.
Complementing the experimental work, the feasibility of cooling a mechanical mode toward its quantum mechanical ground state using a cloud of Rydberg atoms is investigated theoretically. In this approach, Rydberg atoms act as a dissipative resource that extracts phononic excitations from the mechanical resonator and removes them via radiative decay. Furthermore, the potential of Rydberg atom-mediated interactions to generate entanglement between spatially separated mechanical oscillators is analyzed. Together, these results establish a foundation for future experimental investigations of Rydberg atom–mechanical oscillator hybrid systems.

Characterization of Irradiated Depleted Monolithic Active Pixel Sensors in 150 nm and 180 nm CMOS Technology for High-Rate and High-Radiation Environments

2026-04-08T00:00:00Z

Characterization of Irradiated Depleted Monolithic Active Pixel Sensors in 150 nm and 180 nm CMOS Technology for High-Rate and High-Radiation Environments Schall, Lars Philip Modern tracking detectors in high-energy physics experiments target a minimum material budget and precise spatial and time resolution for optimized vertexing capabilities. Monolithic active pixel sensors (MAPS) combine sensitive volume and active readout electronics within a single entity of silicon. This eliminates the complex interconnection step and additional material required for the hybrid pixel detector approach. Recent advances in commercial CMOS technologies and increased availability of high-resistivity silicon substrates facilitate developments of MAPS with large depleted volume and, thus, fast charge collection primarily via drift. These so-called depleted monolithic active pixel sensors (DMAPS) form a viable alternative to hybrid pixel detectors, even in high-rate and high-radiation environments. The Monopix2 chips characterized in this thesis constitute two DMAPS with different design approaches for application in such environments.
For LF-Monopix2, all in-pixel electronics are implemented within a large charge-collection electrode relative to the pixel pitch that yields a homogeneous electric field across the sensor. Combined with the resulting short drift distances within a pixel cell, this design approach facilitates high radiation tolerance. Within the scope of this thesis, the radiation tolerance of LF-Monopix2 is examined up to levels of 5 x 10¹⁵ n_eq cm⁻² NIEL fluence and 400 Mrad total ionizing dose (TID). Due to the high bias voltage capabilities, 100 µm thin samples can be fully depleted up to NIEL fluences of 3 x 10¹⁵ n_eq cm⁻². A performance degradation between 1 and 10 Mrad TID and a subsequent recovery characteristic for this technology feature size is observed during X-ray irradiation. Beam tests of LF-Monopix2 verify hit-detection efficiencies above 99 % after irradiation.
In the case of TJ-Monopix2, the in-pixel electronics are separated from the small charge-collection electrode, which facilitates minimizing the pixel pitch. The resulting small detector capacitance reduces the sensor noise and, thus, requires less power consumption of the electronics. Due to the complex electric field configuration of this design approach, additional process modifications are required to improve fast charge collection via drift, especially after irradiation. As part of this thesis, the origin and extent of a periodic threshold fluctuation relative to the hit arrival time is investigated. The functionality of TJ-Monopix2 after irradiation to 1 x 10¹⁵ n_eq cm⁻² NIEL fluence and 100 Mrad TID is verified and beam tests confirm hit-detection efficiencies above 99 %.

Laser-cooled mercury to search for physics beyond the standard model

2026-04-07T00:00:00Z

Laser-cooled mercury to search for physics beyond the standard model Groh, Thorsten Georg This thesis explores the development and application of laser-cooled mercury atoms for precision measurements relevant to fundamental physics. A primary motivation is the search for a permanent electric dipole moment in mercury, that could shed light on the baryon asymmetry of the universe. We present the design and construction of a custom experimental apparatus for producing and trapping cold mercury atoms, detailing challenges associated with working with mercury in an ultra-high vacuum environment and considering deep-ultraviolet optics. A magneto-optical trap operating on the ¹S₀-³P₁ intercombination line at 254 nm is realized for all seven stable isotopes, achieving atom numbers up to 5x10⁷ and phase-space densities up to 1x10^-6 suitable for optical dipole trap loading. Cooling efficiency for all bosonic and fermionic isotopes are characterized over a wide parameter space, and we show sub-Doppler cooling in ¹⁹⁹Hg and ²⁰¹Hg. The successful loading of mercury into a high-power optical dipole trap is demonstrated, forming the basis for future electric dipole moment experiments of laser cooled mercury atoms. Prospects of evaporatively cooling mercury down to quantum degeneracy could allow for a quantum-enhanced metrology tool kit for the planned measurements. Apart from this, we are exploring the use of ultracold fermionic gases made of mercury as a quantum simulator for impurity physics. As a promising versatile and tunable platform for studying impurity-bath interactions, we are assessing the feasibility of observing Friedel oscillations in ultracold quantum gases.Further, we perform precision isotope shift spectroscopy on several dipole-allowed atomic transitions in mercury. Via King plot analysis this allows investigations of the mercury nuclear structure – also relevant for electric dipole moment bounds – and lays the foundation for probing a potential fifth force carrier coupling electrons to neutrons. We also propose upgrades to the machine for improvements in laser cooling, extensions of the spectroscopy search and a proposed experimental setup for probing the atomic electric dipole moment in an optical dipole trap of cold mercury atoms.