Structural information of individual functional molecules and complexes can be investigated by in-situ atomic force microscopy (AFM) by immobilising the biomolecules of interest (nucleic acids, proteins, carbohydrates, …) via physical, chemical or biological interaction on a flat surface or directly embedded in the cellular membrane environment. The interesting structural information includes sub-nm-conformation, molecular symmetry, binding location and molecular temporal dynamics. The following typical examples are typical results of actual research projects where biological processes of higher complexity (transcription regulation,molecular motors, self-assembly of 2D-protein s-layers) are investigated.
We currently run several commercial AFM for experiments under ambient and liquid conditions, self-built combined TIRF/AFM and SNOM microscopes, as very recently a novel STM/AFM-microscope for ultra-high-vacuum applications.
The physical mechanisms of specific, non-covalent intermolecular binding is quantitatively investigated by single-molecule (dynamic) force spectroscopy with atomic force microscopy (AFM), optical tweezers (OT) and magnetic tweezers (MT). Here, specific molecular forces, elasticities, kinetic reaction rate constants (lifetimes) and the energy landscape of the molecular binding potential is measured by AFM at the single-molecule level in vitro on isolated but functional complexes. Nowadays, these specific interactions can be scrutinized in a quantitative manner at the sensitivity level on single-point mutations (nucleic acids, amino acids) allowing single-molecule affinity ranking in a broad affinity range of 0,1 mM-1 fM revealing distinct differences in the binding properties and mechanisms. Over the last years, special emphasis has been put on so-called molecular catch-bond systems that were observed when investigating the interplay of human sulfatates (Sulf1, Sulf2) with glycosaminoglycans (heparan sulfate, heparin, dermatan sulfate, ...) in cell signaling cascades. In addition, we recently explored the homophilic interaction mechanisms between desmosomal desmoglein-2 (DSG2) and mutations thereof that play an important role for the integrity of mechanically active cells like cardiomyocytes.
Tip and sample surface are both functionalized. In close proximity, individual molecular bonds are formed. When pulled apart, ruptures can be seen as a jumps in the force curve. The corresponding binding forces and lifetimes can be measured with high precision, giving insight in biological relevant binding and sensing processes and even protein folding.
Single molecules can nowadays be investigated by means of optical, mechanical and electrical methods. Single molecule fluorescence imaging and spectroscopy yield valuable and quantitative information about optical properties, spatial distribution and temporal dynamics of single molecules.
We have developped 1) scanning near-field optical microscopy (SNOM) for single molecule imaging and spectroscopy and 2) a small-cantilever based AFM combined with total internal reflection fluorescence (TIRF) microscopy for ultrasensitive LIF detection of individual fluorophores and simultaneous AFM control and manipulation at the molecular level.
Individual fluorescent markers can be localized in the AFM topography with super resolution precision - here shown in tobacco mosaic viruses.
The translocation dynamics of individual macromolecules like DNA or DNA-protein complexes (EcoRI, RecA, peroxiredoxines) through solid-state nanopores (SiNx, graphene, MoS2, BN, ...) is quantitativly investigated by optical tweezers force control. Beyond looking into the physical mechanisms involved we explore the possibility of future sequencing and diagnostic applications thereof.
Micron-sized objects like beads, colloids or cells can be trapped, steered and manipulated by light and allow force experiments at the single molecule level with a force sensitivity level of 0.1 pN. We set up two high stability single-beam optical tweezers (OT) system on an inverted light microscope which allows analytical force spectroscopy, adhesion and elasticity experiments with single molecules or cells in an experimental force range of 0.1-900 pN.
Magnetic microbeads can be manipulated and steered by external magnetic fields and allow stretching and overwinding experiments with single (DNA) molecules at a sensitivity level downto 0,001 pN. With our magnetic tweezers (MT) apparatus (PicoTwist, Lyon - France) we investigate and quantify the binding of proteins, fluorescent dyes and chemotherapeutic agents to DNA.
In this research project we investigate and develop novel micro- and nanofluidical chip device applications that can be used for separation, sorting and harvesting of macromolecules and colloids. We use structured micro- and nanofluidic environments and drive the molecular objects far from thermoddynamic equilibrium to explore non-linear migration mechanisms like absolute negative mobility, dielectrophoretic trapping, molecular ratcheting or chiral separation.
In addition, we design and develop lab-on-a-chip devices where individual cells like E. coli can be trapped and analyzed according their active metabolism by UV-laser-induced fluorescence.
In this research and development project we investigate and develop new methods and products for use in industrial applications. Together with our industrial partners we analyze, develop and optimize nanotechnological products and processes ranging from e.g. nanoparticle based lubricating performance systems, nanomembrane-based biosensor surfaces as well as effective microchip processes for separating large genomic mixtures.
Thema | Ansprechpartener | Infos | |
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Bachelorarbeiten / Abschlussarbeiten fürs Lehramt | ... nach Absprache | Prof. Dario Anselmetti (D1-270) | Kurzbeschreibung (.pdf) |
Masterarbeiten |
... nach Absprache | Prof. Dario Anselmetti (D1-270) | Kurzbeschreibung (.pdf) |
Doktorarbeiten / Ph.D. Thesis |
... nach Absprache | Prof. Dario Anselmetti (D1-270) | Kurzbeschreibung (.pdf) |