The Origin of Solar Activity in the Tachocline

Solar active regions, produced by the emergence of tubes of strong magnetic field in the photosphere, are restricted to within 35 degrees of the solar equator. The nature of the dynamo processes that create and renew these fields, and are therefore responsible for solar magnetic phenomena, are not well understood. We analyze the magneto-rotational stability of the solar tachocline for general field geometry. This thin region of strong radial and latitudinal differential rotation, between the radiative and convective zones, is unstable at latitudes above 37 degrees, yet is stable closer to the equator. We propose that small-scale magneto-rotational turbulence prevents coherent magnetic dynamo action in the tachocline except in the vicinity of the equator, thus explaining the latitudinal restriction of active regions. Tying the magnetic dynamo to the tachocline elucidates the physical conditions and processes relevant to solar magnetism.Comment: 10 pages, 1 figure, accepted for publication in ApJ

Large-scale assessment of Extractables and Leachables in single-use bags for biomanufacturing using ultra high performance liquid chromatography coupled to quadrupole-orbitrap mass spectrometry

Single-use technologies (SUTs) are increasingly used in biopharmaceutical manufacturing processes. Despite their advantages, these plastic assemblies draw concern because they are a potential source of contamination due to extractable and leachable compounds (E&Ls) that result from residual polymeric fragments and different additives used in their manufacture1. Characterizing E&Ls from such materials is a necessary step in establishing their suitability for use. There is evidence of some cytotoxic compounds that leach out of single-use bags into cell culture media in concentrations are deleterious to CHO cell growth, even at trace levels2. Given the potential for these substances to adversely affect biopharmaceutical production, this discovery clearly shows an urgent need for analytical techniques to identify and quantitatively assess compounds resulting from the extraction of SUS components. This study was focused specifically in single-use bags (SUBs), one important application of the disposable technologies, used for the production of therapeutic antibodies, proteins and vaccines. 34 single-use bags from different suppliers were extracted under conditions that are relevant for the characterisation of E&Ls. Extraction with different model solvents was intended to establish a comprehensive extractables profile: water for injection, isopropanol:H2O (1:1), 0.1 M H3PO4 and 50mM NH4CH3COO pH 9.5, while extraction with chemically defined cell culture media was used for leachable assessment. This analysis is challenging as leachables usually exist at trace levels within a very complex matrix. For this reason, a simple and fast analytical method based on a sample treatment by dispersive liquid-liquid microextraction (DLLME) was also developed and applied for analyte preconcentration and matrix elimination. Then, the extracts were analysed by LC-Orbitrap-MS, with high mass resolution performance and exceptional mass accuracy for the detection and identification of non-volatile E&Ls in SUBs. 130 E&Ls were identified, with many of these compounds being polymer additives or their degradation products. Interestingly, some leachables were not found during extractables analysis, suggesting that they might be produced by the interaction of components of the media with compounds from bags. Multivariate analysis performed on the analytical data established significant correlations between the type and concentration of compounds and bags features as brand, manufacturing date and type of polymer. New production techniques have allowed to develop new types of polymers and the advent of regulatory issues that limit/ban the use of certain raw materials and additives has produced a change in the nature of E&Ls. Consequently, it is necessary to provide practical and versatile guidelines for confident determination of these substances that would enable early identification of non-satisfactory films for control and improvement of SUBs. The analytical workflow that is presented has all the necessary features to be used as part of the quality control in bags manufacturing. 1 Gao, Y.; Allison, N. Extractables and leachables issues with the application of single use technology in the biopharmaceutical industry. J Chem Technol Biotechnol. 2016, 91, 289–295. 2 Hammond, M.; Nunn, H.; Rogers, G.; Lee, H.; Marghitoiu, A.-L.; Perez, L.; Nashed-Samuel, Y.; Anderson, C.; Vandiver, M.; Kline, S. Identification of a Leachable Compound Detrimental to Cell Growth in Single-Use Bioprocess Containers. PDA J. Pharm. Sci. Technol. 2013, 67, 123–134

Large-Scale Assessment of Extractables and Leachables in Single-Use Bags for Biomanufacturing

Single-use technologies (SUTs) are widely used during biopharmaceutical manufacture as disposable bioreactors or media and buffer storage bags. Despite their advantages, the risk of release of extractable and leachable (E&Ls) substances is considered an important drawback in adopting disposables in the biomanufacturing process. E&Ls may detrimentally affect cell viability or productivity or may persist during purification and present a risk to the patient if remaining in the final drug product. In this study, 34 plastic films from single-use bags (SUBs) for cell cultivation were extracted with selected solvents that represent reasonable worst-case conditions for most typical biomanufacturing applications. SUBs were incubated at small-scale under accelerated-aging conditions that represented standard operational conditions of use. Leachables analysis was performed following dispersive liquid–liquid microextraction (DLLME) for analyte preconcentration and removal of matrix interference. Resulting extracts were characterized by GC-headspace for volatiles, high resolution GC-Orbitrap-MS/MS for semivolatiles, high resolution LC-Orbitrap-MS/MS for nonvolatiles, and ICP-MS for trace elemental analysis. Multivariate statistical analysis of the analytical data revealed significant correlations between the type and concentration of compounds and bags features including brand, manufacturing date and polymer type. The analytical data demonstrates that, over recent years, the nature of E&Ls has been altered due to the implementation of manufacturing changes and new types of polymers and may change further with the future advent of regulations that will limit or ban the use of certain raw materials and additives. The broad E&L database generated herein facilitates toxicological assessments from a biomanufacturing standpoint and provides practical guidelines for confident determination of E&Ls to enable screening and elimination of nonsatisfactory films for single use bioprocessing

High-resolution mass spectrometry provides novel insights into products of human metabolism of organophosphate and brominated flame retardants

The high resolution, accurate mass, and fast scanning features of the Orbitrap™ mass spectrometer, combined with the separation power of ultrahigh-performance liquid chromatography were applied for the first time to study the metabolic profiles of several organic flame retardants (FRs) present in indoor dust. To mimic real-life exposure, in vitro cultured HepG2 human hepatocyte cell lines were exposed simultaneously to various FRs in an indoor dust extract for 24 h. Target parent FRs, hexabromocyclododecanes (α-, β-, and γ-HBCDs), tris-2-chloroethyl phosphate (TCEP), tris(1-chloro-2-propyl) phosphate (TCIPP), and tris(1,3-dichloro-2-propyl) phosphate (TDCIPP), were separated in a single run for the first time using alternating positive and negative heated ESI source. Further metabolite separation and identification was achieved using full scan (70,000 full width at half maximum (FWHM)), accurate mass (up to 1 ppm) spectrometry. Structural confirmation was performed via all ion fragmentation (AIF) spectra using the optional higher collisional dissociation (HCD) cell and MS/MS analysis. First insights into human metabolism of HBCDs revealed several hydroxylated and debrominated phase I metabolites, in addition to conjugated phase II glucuronides. Furthermore, various hydroxylated, oxidized, and conjugated metabolites of chlorinated phosphorous FRs were identified, leading to the suggestion of α-oxidation as a significant metabolic pathway for these compounds.</p