Frustrated flexibility in metal-organic frameworks

Stimuli-responsive flexible metal-organic frameworks (MOFs) remain at the forefront of porous materials research due to their enormous potential for various technological applications. Here, we introduce the concept of frustrated flexibility in MOFs, which arises from an incompatibility of intra-framework dispersion forces with the geometrical constraints of the inorganic building units. Controlled by appropriate linker functionalization with dispersion energy donating alkoxy groups, this approach results in a series of MOFs exhibiting a new type of guest- and temperature-responsive structural flexibility characterized by reversible loss and recovery of crystalline order under full retention of framework connectivity and topology. The stimuli-dependent phase change of the frustrated MOFs involves non-correlated deformations of their inorganic building unit, as probed by a combination of global and local structure techniques together with computer simulations. Frustrated flexibility may be a common phenomenon in MOF structures, which are commonly regarded as rigid, and thus may be of crucial importance for the performance of these materials in various applications

Parallel use of shake flask and microtiter plate online measuring devices (RAMOS and BioLector) reduces the number of experiments in laboratory-scale stirred tank bioreactors

Background Conventional experiments in small scale are often performed in a Black Box fashion, analyzing only the product concentration in the final sample. Online monitoring of relevant process characteristics and parameters such as substrate limitation, product inhibition and oxygen supply is lacking. Therefore, fully equipped laboratory-scale stirred tank bioreactors are hitherto required for detailed studies of new microbial systems. However, they are too spacious, laborious and expensive to be operated in larger number in parallel. Thus, the aim of this study is to present a new experimental approach to obtain dense quantitative process information by parallel use of two small-scale culture systems with online monitoring capabilities: Respiration Activity MOnitoring System (RAMOS) and the BioLector device. Results The same mastermix (medium plus microorganisms) was distributed to the different small-scale culture systems: 1) RAMOS device; 2) 48-well microtiter plate for BioLector device; and 3) separate shake flasks or microtiter plates for offline sampling. By adjusting the same maximum oxygen transfer capacity (OTRmax), the results from the RAMOS and BioLector online monitoring systems supplemented each other very well for all studied microbial systems (E. coli, G. oxydans, K. lactis) and culture conditions (oxygen limitation, diauxic growth, auto-induction, buffer effects). Conclusions The parallel use of RAMOS and BioLector devices is a suitable and fast approach to gain comprehensive quantitative data about growth and production behavior of the evaluated microorganisms. These acquired data largely reduce the necessary number of experiments in laboratory-scale stirred tank bioreactors for basic process development. Thus, much more quantitative information is obtained in parallel in shorter time.Cluster of Excellence “Tailor-Made Fuels from Biomass”, which is funded by the Excellence Initiative by the German federal and state governments to promote science and research at German universities

Induced Tauopathy in a Novel 3D-Culture Model Mediates Neurodegenerative Processes: A Real-Time Study on Biochips

<div><p>Tauopathies including Alzheimer’s disease represent one of the major health problems of aging population worldwide. Therefore, a better understanding of tau-dependent pathologies and consequently, tau-related intervention strategies is highly demanded. In recent years, several tau-focused therapies have been proposed with the aim to stop disease progression. However, to develop efficient active pharmaceutical ingredients for the broad treatment of Alzheimer’s disease patients, further improvements are necessary for understanding the detailed neurodegenerative processes as well as the mechanism and side effects of potential active pharmaceutical ingredients (API) in the neuronal system. In this context, there is a lack of suitable complex <em>in vitro</em> cell culture models recapitulating major aspects of taupathological degenerative processes in sufficient time and reproducible manner.</p> <p>Herewith, we describe a novel 3D SH-SY5Y cell-based, tauopathy model that shows advanced characteristics of matured neurons in comparison to monolayer cultures without the need of artificial differentiation promoting agents. Moreover, the recombinant expression of a novel highly pathologic fourfold mutated human tau variant lead to a fast and emphasized degeneration of neuritic processes. The neurodegenerative effects could be analyzed in real time and with high sensitivity using our unique microcavity array-based impedance spectroscopy measurement system. We were able to quantify a time- and concentration-dependent relative impedance decrease when Alzheimer’s disease-like tau pathology was induced in the neuronal 3D cell culture model. In combination with the collected optical information, the degenerative processes within each 3D-culture could be monitored and analyzed. More strikingly, tau-specific regenerative effects caused by tau-focused active pharmaceutical ingredients could be quantitatively monitored by impedance spectroscopy.</p> <p>Bringing together our novel complex 3D cell culture taupathology model and our microcavity array-based impedimetric measurement system, we provide a powerful tool for the label-free investigation of tau-related pathology processes as well as the high content analysis of potential active pharmaceutical ingredient candidates.</p> </div

Analysis of cellular alterations after okadaic acid induced hyperphosphorylation in wildtype and mutated tau expressing SH-SY5Y spheroids.

<p><b>A.</b> Western blot analysis of five days cultivated WT, P301L and K280q tau expressing SH-SY5Y spheroids after incubation with okadaic acid (OA) for 24 hours. Hyperphosphorylation was proven by determination of the pathological relevant tau epitopes T212 (p-tau_T212), S262 (p-tau_S262) and S422 (p-tau_S422). Cellular degradation was analyzed by the caspase-3 cleavage products tau_D421 (cl-tau) and cleaved-PARP (cl-PARP) as well as neurofilament-L degradation (NF-L). <b>B.</b> The phosphorylation of the three tau epitopes was quantified relative to total tau, NF-L expression and cleaved protein amounts were quantified relative to β-tubulin (β-tub) <b>C.</b> Significant changes between the tau variants were analyzed to proof the tau pathology state in the tau mutants. (n = 3, *p<0.05, **p<0.01, ***p<0.001). <b>D.</b> For analysis of tauopathy-related alterations in cellular localization and aggregation state of the pathological tau conformation MC-1 (red) and <b>E.</b> tau phosphorylated at S262 (red), five days cultivated WT and K280q spheroids were incubated with 10 nM OA for 24 hours. Immunocytochemical staining of untreated WT, P301L and K280q tau expressing spheroids showed the sporadic accumulation (arrows) and aggregation (arrowheads) of pathological microtubule-associated tau protein. Incubation with OA led to a spread accumulation of aggregated MC-1 and p-tau_S262 tau (arrowheads). Fibrous structures indicate the existence of tau fibrils. (bar = 10 µm, nuclear stain DAPI blue).</p