A: Synthesis and Biofunctionalization of Probes and Nanomaterials
Chemical route for modifying nanoparticles by means of soft macromolecules.
A1: Macromolecular "soft interfaces" between cells and synthetic nanoparticles
Uwe Beginn, Chemistry
The aim of the project is to synthesize macromolecular surface modification agents that irreversibly bind to hard inorganic surfaces and generate a „soft“ hydrophilic and chemically functional, i.e. reactive surface. Inorganic nanoparticles can be coated (= „primered“) with these macromolecules and can subsequently be functionalized with respect to the required needs. Because of the presence of chemically reactive groups on the primer-surface, a once „primered“ nanomaterial can be modified with biological signals, markers, or tracer functions. By means of problem-adapted surface functionalization it is aimed for optimum interactions between nanoparticle and cell surface, as well as between nanoparticle and environment to create active interfaces.
Visible luminescence of different upconversion nanoparticles excited at 980 nm (left) and electron micrograph (right) (Haase lab, unpublished).
A2: Synthesis of anorganic nanocrystals
Markus Haase, Chemistry
The project aims at the synthesis of core-shell nanoparticles with tailored photophysical properties for applications in cell biology via doping and optimization of the core-shell structure. In particular, we intend to synthesize particles for photomanipulation in the UV and blue spectral range in order to manipulate fluorescent proteins locally by light and to track the dynamic properties of protein-protein-interactions with high spatial and temporal resolution. For this purpose, small (approx 10 nm) upconversion nanoparticles will be synthesized.
Hunt for novel ceramide binding proteins. (a) Photoactivatable and clickable ceramide probe, pacCer. (b) Application of pacCer to capture mitochondrial ceramide binding proteins (CBPs) (Bockelmann et al., J. Lipid Res., 2018; Holthuis lab, unpublished)
A3: Dissecting lipid-protein crosstalk in life-death signaling with photo-actuated lipid probes
Joost Holthuis, Biology
Ceramides draw wide attention as tumor suppressor lipids, yet the mechanisms by which they exert their anti-neoplastic activities are largely unknown. The application of photo-crosslinkable ceramide analogues previously enabled us to capture novel effector proteins of ceramide-mediated cell death. In this project, we expand our collection of functionalized sphingolipids with photo-switchable analogues as novel tools to: i) obtain mechanistic insights into how the newly identified ceramide effectors operate; ii) gain optical control over ceramide-mediated life-death signaling and other sphingolipid-mediated processes in physiologically relevant cell models.
Tunable generation of light using nonlinear niobate nanocrystals (unpublished results)
A4: Femtosecond photo-physics of nonlinear optical nanomaterials
Mirco Imlau, Physics
The Imlau research group focuses on the photo-physical, nonlinear optical properties of nanophotonic probes with respect to high-resolution imaging and photomanipulation in cells. We study energy transfer mechanisms within luminescent or harmonic nanoparticles, but also to biomolecules at the interface and to the direct physiological environment with femtosecond temporal resolution. This allows for a precise, stepwise modeling and understanding of the processes involved. The results are particularly important for the further, targeted design of nonlinear optical nanoprobes.
Specific binding of nanoparticles (red) to target proteins (green) on mitochondria and single particle trajectories (Liße et al., Angew. Chem. 2011)
A5: Biofunctionalization of nanoparticles for site-specific labeling
Jacob Piehler, Biology
The Piehler group develops strategies for the biofunctionalization of nanoparticles for a site-specific, stoichiometrically defined conjugation with target proteins in living cells. Next to luminescent inorganic nanoparticles (quantum dots, upconversion nanoparticles), we use protein cages such as ferritin as scaffolds for nanoparticles. These can be efficiently doped with fluorescent dyes, but also loaded with a magnetic core for noninvasive manipulation by magnetic field gradients. By functionalization with highly selective biochemical recognition units, efficient targeting to proteins in the cellular context is achieved.
Schematic architecture and conformational organization of nucleic acid duplex structures anchored within an artificial lipid bilayer (Werz & Rosemeyer, Beilstein J Org Chem 2014)
A6: Synthesis of lipo-oligonucleotides and their interaction with artificial lipid membranes
Helmut Rosemeyer, Chemistry
The group develops nucleic acids (DNA and RNA) which are 5’-hydrophobized by incorporation of lipophilic phosphoramidite building blocks. Duplex formation between such lipophilized probe nucleic acids and complementary DNA- or siRNA sequences is studied in artificial lipid bilayer membranes. Here, both their immobilization rates and stability within the bilayer as well as their transfection across artificial membranes or the human Stratum corneum are of interest. The goal is the optimization of their pharmacological applicability as tnRNS's.
Normalized EPR spectra of different Gd-doped nanoparticles (Komban et al., Angew. Chem. 2013)
A7: EPR spectroscopy of nanomaterials
Heinz-Jürgen Steinhoff, Physics
Johann Klare, Physics
The Steinhoff group uses ferromagnetic resonance and electron paramagnetic resonance (EPR) spectroscopy to characterize the magnetic properties of nanomaterials and thin films. Distance distributions between paramagnetic centers are utilized to determine long-range order and growth mechanisms. Studied subjects are, e.g., lanthanide-doped nanocrystals and spin labeled proteins tethered to nanostructured surfaces.
Inhomogeneous fluorescence of ~10 nm diameter nanodiamonds and chemical control of the surface spin bath (Wieczorek et al., unpublished).
A8: Development of nano-diamonds for spin-based biofunctional analysis
Wolfgang Harneit, Physics
Nanodiamonds (size 5-100 nm) containing nitrogen-vacancy (NV) color centers constitute a novel class of bio-sensors. The electron spin of individual NV centers can be interrogated optically with or without additional microwave irradiation to provide detailed information on their magnetic environment, including the presence and density of radical states. At present, commercially available nanodiamonds are either too large for low-damage incorporation in cells or they show a variety of undesirable surface states limiting their application. The Harneit group develops (a) surface functionalization protocols for small (\(\leq\) 40 nm) nanodiamonds to enhance their spectroscopic properties and, ultimately, their sensitivity in biological settings; (b) interrogation protocols suitable for in-cell probing. Essential collaborations exist with the research groups Klare (Physics), Steinhart (Chemistry) and Piehler/You (Biology).
Combined nanoparticle-features for unbiased magnetogenetic manipulation of proteins inside living cells.
A9: Design, production and cellular application of semi-synthetic magnetic nanoparticles
Domenik Liße, Biology
The remote control of cellular functions by external stimuli is of tremendous interest not only in academic research, but also for biomedical applications. Towards this goal, our team aims to develop generic methods based on semi-synthetic magnetic nanoparticles that enable magnetogenetic manipulation of proteins inside living cells. These bottom-up approaches are tailored to meet the key criteria for unbiased biological applications – complete biocompatibility with negligible toxic effects.