1,400 research outputs found
HPLC Quantification of 4-Nitrophenol and its Conjugated Metabolites from Bile
An isocratic ion pair RP-HPLC method with UV-Vis detection has been developed and validated for simultaneous analysis of 4-nitrophenol (PNP), 4-nitrophenyl β-glucuronide (PNP-G), and 4-nitrophenyl sulfate (PNP-S) in rat bile samples using 4-ethylphenol (ETP) as internal standard. Chromatographic separation was achieved on a C18 column by isocratic elution with a mobile phase consisted of methanol-0.01 M citrate buffer pH 6.2 (47:53 v/v) containing 0.03 M TBAB. The flow rate was 1.0 ml min−1, the detection was affected at 290 nm. Calibration plots were generated over the concentration range 1–100 μM PNP, PNP-G, PNP-S with a common lower limit of quantification of 2.5 μM. Intra- and inter-day precision and repeatability were determined at six different concentrations. Results obtained by application of the method for determination of PNP, PNP-G and PNP-S in bile fractions collected during intestinal perfusion of PNP in hyperglycemic rats are presented
First Steps Towards a Runtime Analysis of Neuroevolution
We consider a simple setting in neuroevolution where an evolutionary
algorithm optimizes the weights and activation functions of a simple artificial
neural network. We then define simple example functions to be learned by the
network and conduct rigorous runtime analyses for networks with a single neuron
and for a more advanced structure with several neurons and two layers. Our
results show that the proposed algorithm is generally efficient on two example
problems designed for one neuron and efficient with at least constant
probability on the example problem for a two-layer network. In particular, the
so-called harmonic mutation operator choosing steps of size with
probability proportional to turns out as a good choice for the underlying
search space. However, for the case of one neuron, we also identify situations
with hard-to-overcome local optima. Experimental investigations of our
neuroevolutionary algorithm and a state-of-the-art CMA-ES support the
theoretical findings.Comment: 27 pages; full version of paper published at FOGA 2023 and available
at AC
In memoriam von Prof.Dr. János Somogyi (1929-2019) = In memoriam of Prof.Dr. János Somogyi (1929-2019)
Am 11. Juni 2018 haben wir mit Prof. Dr. Emil Fischer gemeinsam die traurige Nachricht über den plötzlichen Tod von Prof. Dr. János Somogyi erhalten. Er ist in seiem 90. Lebensjahr am 24.Mai plötzlich verstorben, am 7. Juni wurde er im engsten Familienkreis bestattet
A nanobody:GFP bacterial platform that enables functional enzyme display and easy quantification of display capacity
Background: Bacterial surface display is an attractive technique for the production of cell-anchored, functional proteins and engineering of whole-cell catalysts. Although various outer membrane proteins have been used for surface display, an easy and versatile high-throughput-compatible assay for evaluating and developing surface display systems is missing.Results: Using a single domain antibody (also called nanobody) with high affinity for green fluorescent protein (GFP), we constructed a system that allows for fast, fluorescence-based detection of displayed proteins. The outer membrane hybrid protein LppOmpA and the autotransporter C-IgAP exposed the nanobody on the surface of Escherichia coli with very different efficiency. Both anchors were capable of functionally displaying the enzyme Chitinase A as a fusion with the nanobody, and this considerably increased expression levels compared to displaying the nanobody alone. We used flow cytometry to analyse display capability on single-cell versus population level and found that the signal peptide of the anchor has great effect on display efficiency.Conclusions: We have developed an inexpensive and easy read-out assay for surface display using nanobody:GFP interactions. The assay is compatible with the most common fluorescence detection methods, including multi-well plate whole-cell fluorescence detection, SDS-PAGE in-gel fluorescence, microscopy and flow cytometry. We anticipate that the platform will facilitate future in-depth studies on the mechanism of protein transport to the surface of living cells, as well as the optimisation of applications in industrial biotech
Nova Geminorum 1912 and the Origin of the Idea of Gravitational Lensing
Einstein's early calculations of gravitational lensing, contained in a
scratch notebook and dated to the spring of 1912, are reexamined. A hitherto
unknown letter by Einstein suggests that he entertained the idea of explaining
the phenomenon of new stars by gravitational lensing in the fall of 1915 much
more seriously than was previously assumed. A reexamination of the relevant
calculations by Einstein shows that, indeed, at least some of them most likely
date from early October 1915. But in support of earlier historical
interpretation of Einstein's notes, it is argued that the appearance of Nova
Geminorum 1912 (DN Gem) in March 1912 may, in fact, provide a relevant context
and motivation for Einstein's lensing calculations on the occasion of his first
meeting with Erwin Freundlich during a visit in Berlin in April 1912. We also
comment on the significance of Einstein's consideration of gravitational
lensing in the fall of 1915 for the reconstruction of Einstein's final steps in
his path towards general relativity.Comment: 31 p
Generation of mutation hotspots in ageing bacterial colonies
How do ageing bacterial colonies generate adaptive mutants? Over a period of two months, we isolated on ageing colonies outgrowing mutants able to use a new carbon source, and sequenced their genomes. This allowed us to uncover exquisite details on the molecular mechanism behind their adaptation: most mutations were located in just a few hotspots in the genome and over time, mutations increasingly originated from 8-oxo-guanosine, formed exclusively on the transcribed strand.</jats:p
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