Self-diffusion and Cooperative Diffusion in Semidilute Polymer Solutions as measured by Fluorescence Correlation Spectroscopy

We present a comprehensive investigation of polymer diffusion in the semidilute regime by fluorescence correlation spectroscopy (FCS) and dynamic light scattering (DLS). Using single-labeled polystyrene chains, FCS leads to the self-diffusion coefficient while DLS gives the cooperative diffusion coefficient for exactly the same molecular weights and concentrations. Using FCS we observe a new fast mode in the semidilute entangled concentration regime beyond the slower mode which is due to self-diffusion. Comparison of FCS data with data obtained by DLS on the same polymers shows that the second mode observed in FCS is identical to the cooperative diffusion coefficient measured with DLS. An in-depth analysis and a comparison with current theoretical models demonstrates that the new cooperative mode observed in FCS is due to the effective long-range interaction of the chains through the transient entanglement network

MapperMania: A Framework for Native Multi-Tenancy Business Object Mapping to a Persistent Data Source

The Software-as-a-Service delivery model bears new challenges for application developers. Especially in the context of enterprise resource planning software targeting the SME market, new problems arise. Most of them agglomerate around the occurrence of multi-tenancy. This paper describes the framework MapperMania which aims to establish an abstraction layer between the persistence layer and the domain model. Leveraging MapperMania, the domain model is able to abstract from multi-tenancy and changes in the underlying infrastructure

EU-Gipfel: Kann eine Fiskalunion den Euro retten?

Ende Januar einigten sich 25 EU-Staaten in einem Fiskalpakt auf Schuldenbremsen, die sie auf eine Politik des ausgeglichenen Haushalts festlegen. Für den Fall von Abweichungen soll ein automatischer Korrekturmechanismus in die Regelungen integriert werden. Die Einfügung von Schuldenbremsen in die nationalen Gesetzgebungen soll durch den Europäischen Gerichtshof überprüft werden. Ist der Euro so zu retten?

Service Objects: Adaptable, Metadata-Based Services for Multi-Tenant On-Demand Enterprise Applications

An adaptive, standardized service layer is a key feature of a multi-tenant on-demand enterprise application. Custom business logic and data need to be exposed via services that are tailored to the respective customer organization. Ideally, this layer of web services can be automatically derived from the underlying domain model. This paper aims to describe means to design and implement such a service layer by following a lean, model-driven approach based on the runtime interpretation of metadata. Finally, the implementation will be validated against a real-world show case

Nanobody Detection of Standard Fluorescent Proteins Enables Multi-Target DNA-PAINT with High Resolution and Minimal Displacement Errors

DNA point accumulation for imaging in nanoscale topography (PAINT) is a rapidly developing fluorescence super-resolution technique, which allows for reaching spatial resolutions below 10 nm. It also enables the imaging of multiple targets in the same sample. However, using DNA-PAINT to observe cellular structures at such resolution remains challenging. Antibodies, which are commonly used for this purpose, lead to a displacement between the target protein and the reporting fluorophore of 20–25 nm, thus limiting the resolving power. Here, we used nanobodies to minimize this linkage error to ~4 nm. We demonstrate multiplexed imaging by using three nanobodies, each able to bind to a different family of fluorescent proteins. We couple the nanobodies with single DNA strands via a straight forward and stoichiometric chemical conjugation. Additionally, we built a versatile computer-controlled microfluidic setup to enable multiplexed DNA-PAINT in an efficient manner. As a proof of principle, we labeled and imaged proteins on mitochondria, the Golgi apparatus, and chromatin. We obtained super-resolved images of the three targets with 20 nm resolution, and within only 35 minutes acquisition time

Quantifying Microsecond Transition Times Using Fluorescence Lifetime Correlation Spectroscopy

Many complex luminescent emitters such as fluorescent proteins exhibit multiple emitting states that result in rapid fluctuations of their excited-state lifetime. Here, we apply fluorescence lifetime correlation spectroscopy (FLCS) to resolve the photophysical state dynamics of the prototypical fluorescence protein enhanced green fluorescent protein (EGFP). We quantify the microsecond transition rates between its two fluorescent states, which have otherwise highly overlapping emission spectra. We relate these transitions to a room-temperature angstrom-scale rotational isomerism of an amino acid next to its fluorescent center. With this study, we demonstrate the power of FLCS for studying the rapid transition dynamics of a broad range of light-emitting systems with complex multistate photophysics, which cannot be easily done by other methods

Exfoliation and Optical Properties of Near-Infrared Fluorescent Silicate Nanosheets

The silicates Egyptian Blue (CaCuSi4O10, EB), Han Blue (BaCuSi4O10, HB) and Han Purple (BaCuSi2O6, HP) emit in bulk bright and stable fluorescence in the near-infrared (NIR), which is of high interest for (bio)photonics due to minimal scattering, absorption and phototoxicity in this spectral range. So far the optical properties of nanosheets (NS) of these silicates are poorly understood. Here, we exfoliate them into nanosheets and report their physicochemical properties. The approach uses ball milling followed by tip sonication and centrifugation steps to exfoliate the silicates into NS with a lateral size ≈ 16-27 nm and thickness ≈ 1-4 nm. They emit at ≈ 927 nm (EB-NS), 953 nm (HB-NS) and 924 nm (HP-NS) and single NS can be resolved in the NIR. Fluorescence lifetimes decrease from ≈ 30-100 μs (bulk) to 17 μs (EB- NS), 8 μs (HB-NS) and 7 μs (HP-NS). NS of different composition/size can be imaged by fluorescence lifetime imaging, which enables lifetime-encoded multicolor imaging both on the microscopic and the macroscopic scale. Finally, remote imaging through tissue phantoms reveals the potential for bioimaging. In summary, we report a procedure to gain NIR fluorescent silicate nanosheets, characterize their photophysical properties and show their potential for NIR photonics.</div

Axial Colocalization of Single Molecules with Nanometer Accuracy Using Metal-Induced Energy Transfer

Single-molecule localization based super-resolution microscopy has revolutionized optical microscopy and routinely allows for resolving structural details down to a few nanometers. However, there exists a rather large discrepancy between lateral and axial localization accuracy, the latter typically three to five times worse than the former. Here, we use single-molecule metal-induced energy transfer (smMIET) to localize single molecules along the optical axis, and to measure their axial distance with an accuracy of 5 nm. smMIET relies only on fluorescence lifetime measurements and does not require additional complex optical setups

Cell–Substrate Dynamics of the Epithelial-to-Mesenchymal Transition

The biological process of the epithelial-to-mesenchymal transition (EMT) allows epithelial cells to enhance their migratory and invasive behavior and plays a key role in embryogenesis, fibrosis, wound healing, and metastasis. Among the multiple biochemical changes from an epithelial to a mesenchymal phenotype, the alteration of cellular dynamics in cell–cell as well as cell–substrate contacts is crucial. To determine these variations over the whole time scale of the EMT, we measure the cell–substrate distance of epithelial NMuMG cells during EMT using our newly established metal-induced energy transfer (MIET) microscopy, which allows one to achieve nanometer axial resolution. We show that, in the very first hours of the transition, the cell–substrate distance increases substantially, but later in the process after reaching the mesenchymal state, this distance is reduced again to the level of untreated cells. These findings relate to a change in the number of adhesion points and will help to better understand remodeling processes associated with wound healing, embryonic development, cancer progression, or tissue regeneration