A robust sheath‐flow CE‐MS interface for hyphenation with Orbitrap MS

The hyphenation of capillary electrophoresis with high‐resolution mass spectrometry, such as Orbitrap MS, is of broad interest for the unambiguous and exceptionally sensitive identification of compounds. However, the coupling of these techniques requires a robust ionization interface that does not influence the stability of the separation voltage while coping with oxidation of the emitter tip at large ionization voltages. Herein, we present the design of a sheath‐flow CE‐ESI‐MS interface which combines a robust and easy to operate set‐up with high‐resolution Orbitrap MS detection. The sheath liquid interface is equipped with a gold coated electrospray emitter which increases the stability and overall lifetime of the system. For the characterization of the interface, the spray stability and durability were investigated in dependence of the sheath‐flow rate, electrospray voltage, and additional gold coating. The optimized conditions were applied to a separation of angiotensin II and neurotensin resulting in LODs of 2.4 and 3.5 ng/mL

Iron-Mediated Peptide Formation in Water and Liquid Sulfur Dioxide under Prebiotically Plausible Conditions

Peptides have essential structural and catalytic functions in living organisms. The formation of peptides requires the overcoming of thermodynamic and kinetic barriers. In recent years, various formation scenarios that may have occurred during the origin of life have been investigated, including iron(III)-catalyzed condensations. However, iron(III)-catalysts require elevated temperatures and the catalytic activity in peptide bond forming reactions is often low. It is likely that in an anoxic environment such as that of the early Earth, reduced iron compounds were abundant, both on the Earth's surface itself and as a major component of iron meteorites. In this work, we show that reduced iron activated by acetic acid mediates efficiently peptide formation. We recently demonstrated that, compared to water, liquid sulfur dioxide (SO2) is a superior reaction medium for peptide formations. We thus investigated both and observed up to four amino acid/peptide coupling steps in each solvent. Reaction with diglycine (G(2)) formed 2.0 % triglycine (G(3)) and 7.6 % tetraglycine (G(4)) in 21 d. Addition of G(3) and dialanine (A(2)) yielded 8.7 % G(4). Therefore, this is an efficient and plausible route for the formation of the first peptides as simple catalysts for further transformations in such environments

Application Of The Dynamic Tolerancing Approach To The Assembly Of Fuel Cell Stacks

The proton exchange membrane fuel cell (PEM-FC) makes it possible to provide electrical energy for a wide range of applications without polluting emissions as a by-product. However, various challenges need to be overcome before widespread use of this technology is possible. In addition to optimizing its performance and lifetime, a key challenge is to reduce production costs. Production processes significantly affect these three objectives. Tighter manufacturing tolerances on the main components, membrane exchange assembly and bipolar plate, for example, can improve the functions above. However, manufacturing to tighter tolerances usually leads to higher production costs. To resolve the contradiction between 'tight tolerances' and 'low costs', the principle of dynamic tolerancing was developed. So far, this principle has only been implemented for a shaft-hub connection. The approach presented here applies the principle to the assembly process of a stack for a PEM-FC and shows how the channel offset within a stack can be reduced without increasing the requirements for individual part tolerances

Thermal Transients to Accelerate Cyclic Aging of Lithium‐Ion Batteries

Cyclic aging tests of lithium-ion batteries are very time-consuming. Therefore, it is necessary to reduce the testing time by tightening the testing conditions. However, the acceleration with this approach is limited without altering the aging mechanisms. In this paper, we investigate whether and how thermal transients accelerate the aging. The tests are performed on NMC/graphite pouch cells by applying temperatures in a range of 5 °C to 45 °C to the cell surface. The results show, that an accelerated capacity loss can be achieved in comparison to the reference cell at a steady-state temperature of 25 °C. However, capacity difference analysis (CDA) prognoses a covering layer for the transient cells, which is confirmed upon post-mortem analysis. We suspect the origin to lie in the dynamics of temperature fields and current distribution during temperature changes when charging. More specifically, areas of higher temperature in the cell lead to high local current densities and plating. Subsequently, high temperatures promote the reaction of the plated lithium with electrolyte. The results show that thermal transients are a critical condition for lifetime and safety and should be treated with caution as they can occur during real life operation

Влияние пластификации на тепловое расширение полимеров

В статье рассмотрено влияние пластификации и модификации некоторых полимеров на температуру стеклования и параметры теплового расширения. В термопластичных полимерах, с достаточно гибкими макромолекулярными цепями, введение пластификатора или модификатора не влияет на величину свободного объема при Т=ТС и поведение таких систем подчиняется эмпирическому правилу Симха и Бойера. Отклонения от него наблюдаются лишь при больших концентрациях пластификатора, ограниченно совмещающегося с полимером

From amino acid mixtures to peptides in liquid sulphur dioxide on early Earth

The formation of peptide bonds is one of the most important biochemical reaction steps. Without the development of structurally and catalytically active polymers, there would be no life on our planet. However, the formation of large, complex oligomer systems is prevented by the high thermodynamic barrier of peptide condensation in aqueous solution. Liquid sulphur dioxide proves to be a superior alternative for copper-catalyzed peptide condensations. Compared to water, amino acids are activated in sulphur dioxide, leading to the incorporation of all 20 proteinogenic amino acids into proteins. Strikingly, even extremely low initial reactant concentrations of only 50 mM are sufficient for extensive peptide formation, yielding up to 2.9% of dialanine in 7 days. The reactions carried out at room temperature and the successful use of the Hadean mineral covellite (CuS) as a catalyst, suggest a volcanic environment for the formation of the peptide world on early Earth

Identification of single-point mutations in mycobacterial 16S rRNA sequences by confocal single-molecule fluorescence spectroscopy

We demonstrate the specific identification of single nucleotide polymorphism (SNP) responsible for rifampicin resistance of Mycobacterium tuberculosis applying fluorescently labeled DNA-hairpin structures (smart probes) in combination with single-molecule fluorescence spectroscopy. Smart probes are singly labeled hairpin-shaped oligonucleotides bearing a fluorescent dye at the 5′ end that is quenched by guanosine residues in the complementary stem. Upon hybridization to target sequences, a conformational change occurs, reflected in a strong increase in fluorescence intensity. An excess of unlabeled (‘cold’) oligonucleotides was used to prevent the formation of secondary structures in the target sequence and thus facilitates hybridization of smart probes. Applying standard ensemble fluorescence spectroscopy we demonstrate the identification of SNPs in PCR amplicons of mycobacterial rpoB gene fragments with a detection sensitivity of 10(−8) M. To increase the detection sensitivity, confocal fluorescence microscopy was used to observe fluorescence bursts of individual smart probes freely diffusing through the detection volume. By measuring burst size, burst duration and fluorescence lifetime for each fluorescence burst the discrimination accuracy between closed and open (hybridized) smart probes could be substantially increased. The developed technique enables the identification of SNPs in 10(−11) M solutions of PCR amplicons from M.tuberculosis in only 100 s

IR Spectrum of the O-H......O Hydrogen Bond of Phthalic Acid Monomethylester in Gas Phase and in CCl4_4 Solution

The absorption spectrum of the title compound in the spectral range of the Hydrogen-bonded OH-stretching vibration has been investigated using a five-dimensional gas phase model as well as a QM/MM classical molecular dynamics simulation in solution. The gas phase model predicts a Fermi-resonance between the OH-stretching fundamental and the first OH-bending overtone transition with considerable oscillator strength redistribution. The anharmonic coupling to a low-frequency vibration of the Hydrogen bond leading to a vibrational progression is studied within a diabatic potential energy curve model. The condensed phase simulation of the dipole-dipole correlation function results in a broad band in the 3000 \cm region in good agreement with experimental data. Further, weaker absorption features around 2600 \cm have been identified as being due to motion of the Hydrogen within the Hydrogen bond.Comment: Contribution to Horizons in Hydrogen Bond Research Conference, Paris 200