A new method for the automated selection of the number of components for deconvolving overlapping chromatographic peaks

Mathematical deconvolution methods can separate co-eluting peaks in samples for which (chromatographic) separation fail. However, these methods often heavily rely on manual user-input and interpretation. This is not only time-consuming but also error-prone and automation is needed if such methods are to be applied in a routine manner.     

Exchange Phenomena in Radical-Anions of Cyclopentadithiophenones and Dithienothiophene-Dioxides

During electron spin resonance studies of radical-anions¹ of the thiophene analogues of fluorenone (cyclopentadithiophenones, I_A-VI_A) and dibenzothiophene-dioxide (dithienothiophene-dioxides, I_B-VI_B) deuteriumhydrogen exchange phenomena were observed.     

üBER DIE INSERTION VON RPS2 IN DIE PN-BINDUNG VON AMINOPHOSPHINEN

Abstract

Aminophosphine des Typs R_n P(NR′₂)_3-n (n= 2, 1, 0; R = Ph, c-Hex, (-)Men, t-Bu; R′= Me, Et, n-Bu) reagieren mit 2, 4-Bis(aryl)-1, 3, 2, 4-dithiadiphosphetan-2, 4-disulfiden (ArPS₂)₂(Ar: Ph, 4-Methoxyphenyl = An, Naphthyl, Thienyl) unter formaler Insertion monomerer {ArPS₂)-Einheiten in eine oder in zwei der λ³-P—N-Bindung zu chiralen Organophosphorverbindungen Ar(R′₂N)P(S)—S—PR_n (NR′₂)_2-n(n = 2, 1, 0) und [Ar(R′₂N)P(S)—]₂PR₂(NR′₂)_1-n (n = 1.0). In diesen werden bei Raumtemperatur bevorzugt die λ³—P—N—und λ³—P—S-Bindungen durch H₂O oder Methanol unter Bildung von Produktgemischen solvolysiert. Mit Chlorwasserstoff bildet sich aus An(Et₂N)P(S)—S—PPh(NEt₂) das An(Et₂ N)P(S)—S—PPh(C1). Addition von Schwefel führt zu Ar(R′₂N)P(S)—S—P(S)R_n (NR′)_2-n (n=2, 1). Die Stereoisomerenbildung der neuen Verbindungen wird besprochen und ihre Struktur sowie die Zusammensetzung der Reaktionsmischungen aus den ³¹P-Spektren hergeleitet.

Aminophosphines R_n P(NR′₂)_3-n (n = 2, 1, 0; R = Ph. c-Hex, (-)Men, t-Bu; R′= Me, Et, n-Bu) react with 2, 4-Bis(aryl)-1, 3, 2, 4-dithiadiphosphetane-2, 4-disulfides (ArPS₂)₂ (Ar: Ph, 4-Methoxyphenyl = An, Naphthyl, Thienyl) under formal insertion of monomeric {ArPS₂)-units in one or in two of the λ³-P—N-bonds to yield chiral organophosphorus compounds Ar(R′₂N)P(S)—S—]₂PR_n (NR′₂)₂ (n = 2, 1, 0) and [Ar(R′₂N)P(S)—S—]₂ PR₂ (NR′₂)_2-n (n = 1, 0). At room temperature chiefly the A—P—N and A³—P—S-bonds in these products are solvolyzed by H, O or methanol with formation of mixtures of compounds. With hydrogen chloride An(Et₂N)P(S)—S—PPh(NEt₂) is converted into An(Et₂N)P(S)—S—PPh(Cl). Addition of sulfur yields Ar(R′₂N)P(S)—S P(S)R_n (NR′₂)_2-n (n = 2, 1). Stereoisomerism of the new compounds is discussed and their structures as well as the composition of reaction mixtures are deduced from “P-NMR-spectra”.     

U6 is unsuitable for normalization of serum miRNA levels in patients with sepsis or liver fibrosis

MicroRNA (miRNA) levels in serum have recently emerged as potential novel biomarkers for various diseases. miRNAs are routinely measured by standard quantitative real-time PCR (qPCR); however, the high sensitivity of qPCR demands appropriate normalization to correct for nonbiological variation. Presently, RNU6B (U6) is used for data normalization of circulating miRNAs in many studies. However, it was suggested that serum levels of U6 themselves might differ between individuals. Therefore, no consensus has been reached on the best normalization strategy in ‘circulating miRNA''. We analyzed U6 levels as well as levels of spiked-in SV40-RNA in sera of 44 healthy volunteers, 203 intensive care unit patients and 64 patients with liver fibrosis. Levels of U6 demonstrated a high variability in sera of healthy donors, patients with critical illness and liver fibrosis. This high variability could also be confirmed in sera of mice after the cecal ligation and puncture procedure. Most importantly, levels of circulating U6 were significantly upregulated in sera of patients with critical illness and sepsis compared with controls and correlated with established markers of inflammation. In patients with liver fibrosis, U6 levels were significantly downregulated. In contrast, levels of spiked-in SV40 displayed a significantly higher stability both in human cohorts (healthy, critical illness, liver fibrosis) and in mice. Thus, we conclude that U6 levels in the serum are dysregulated in a disease-specific manner. Therefore, U6 should not be used for data normalization of circulating miRNAs in inflammatory diseases and previous studies using this approach should be interpreted with caution. Further studies are warranted to identify specific regulatory processes of U6 levels in sepsis and liver fibrosis.     

A Novel Mechanism for the Extraction of Metals from Water to Ionic Liquids

We present a novel mechanism for the extraction of metals from aqueous phases to room-temperature ionic liquids (ILs) by use of a high-temperature salt as an extraction agent. The mechanism capitalizes on the fact that charged metal complexes are soluble in ILs; this allows for extraction of charged complexes rather than the neutral species, which are formed by conventional approaches. The use of a well-chosen extraction agent also suppresses the competing ion-exchange mechanism, thus preventing degradation of the ionic liquid. The approach permits the use of excess extractant to drive the recovery of metals in high yield. This work presents both a thermodynamic framework for understanding the approach and experimental verification of the process in a range of different ILs. The method has great potential value in the recovery of metals, water purification and nuclear materials processing.     

Laser ionization of H2S and ion-molecule reactions of H3S+ in laser-based ion mobility spectrometry and drift cell time-of-flight mass spectrometry

The detection of hydrogen sulfide (H₂S) by 2?+?1 resonance-enhanced multi-photon ionization (REMPI) and the application of H₂S as a laser dopant for the detection of polar compounds in laser ion mobility (IM) spectrometry at atmospheric pressure were investigated. Underlying ionization mechanisms were elucidated by additional studies employing a drift cell interfaced to a time-of-flight mass spectrometer. Depending on the pressure, the primary ions H₂S⁺, HS⁺, S⁺, and secondary ions, such as H₃S⁺, were observed. The 2?+?1 REMPI spectrum of H₂S near λ?=?302.5 nm was recorded at atmospheric pressure. Furthermore, the limit of detection and the linear range were established. In the second part of the work, H₂S was investigated as an H₂O analogous laser dopant for the ionization of polar substances by proton transfer. H₂S exhibits a proton affinity (PA) similar to that of H₂O, but a significantly lower ionization energy facilitating laser ionization. Ion-molecule reactions (IMR) of H₃S⁺ with a variety of polar substances with PA between 754.6 and 841.6 kJ/mol were investigated. Representatives of different compound classes, including alcohols, ketones, esters, and nitroaromatics were analyzed. The IM spectra resulting from IMR of H₃S⁺ and H₃O⁺ with these substances are similar in structure, i.e., protonated monomer and dimer ion peaks are found depending on the analyte concentration.     

Hard X-ray nanoprobe investigations of the subtissue metal distributions within Daphnia magna

The unique potential of nanoscale elemental imaging of major/minor and trace-level elemental distributions within thin biological tissue sections of the ecotoxicological model organism Daphnia magna is demonstrated by synchrotron radiation nano-X-ray fluorescence (nano-XRF). The applied highly specialized sample preparation method, coupled with the high spatial resolution (～180 nm) and high X-ray photon flux (6?×?10¹¹ photons/s) available at the European Synchrotron Radiation Facility (ESRF) ID22NI beamline proved to be critical for the high-quality visualization of (trace-)metal distributions on the submicron level within the target structures of interest. These include the branchial sacs on the thoracic appendages (epipodites) of D. magna, which are osmoregulatory regions where ion exchange occurs. For the main element of interest (Zn), detection limits of 0.7 ppm (3 ag) was reached in fast-scanning mode using an acquisition time of 0.3 s/pixel. As demonstrated, synchrotron radiation nano-XRF revealed the elemental distributions of Ca, Fe, and Zn within this osmoregulatory region on the submicron scale, aiding the exploration of possible detoxification mechanisms of Zn within D. magna at the subtissue level.