A Broadly Accessible Liquid Chromatography Method for Quantification of Six Nitrosamine Compounds and N,N-Dimethylformamide in Metformin Drug Products Using High Resolution Mass Spectrometry

N-nitrosodimethylamine (NDMA) and the industrial solvent, N,N-dimethylformamide (DMF), are both probable human carcinogens that have been detected in pharmaceutical drug products like metformin, which is used to treat type II diabetes. Some lots of metformin drug products have exceeded the United States Food and Drug Administration (FDA) daily allowable intake limit for NDMA, while the presence of DMF has been detected at several orders of magnitude higher than NDMA. A recent study found that a low abundance isotope of DMF interferes with NDMA quantification by using a unique subset of LC-MS instruments capable of high mass resolution. In this study, an LC-HRMS method is developed that chromatographically separates NDMA from DMF in metformin drug products to eliminate interference. The method can detect nitrosamines and DMF under the current regulatory guidance for industry and provides a solution for simultaneously quantifying nitrosamines and DMF for a broad range of LC-MS instruments

Crystal Structure of Dengue Virus Type 1 Envelope Protein in the Postfusion Conformation and Its Implications for Membrane Fusion ▿

Dengue virus relies on a conformational change in its envelope protein, E, to fuse the viral lipid membrane with the endosomal membrane and thereby deliver the viral genome into the cytosol. We have determined the crystal structure of a soluble fragment E (sE) of dengue virus type 1 (DEN-1). The protein is in the postfusion conformation even though it was not exposed to a lipid membrane or detergent. At the domain I-domain III interface, 4 polar residues form a tight cluster that is absent in other flaviviral postfusion structures. Two of these residues, His-282 and His-317, are conserved in flaviviruses and are part of the “pH sensor” that triggers the fusogenic conformational change in E, at the reduced pH of the endosome. In the fusion loop, Phe-108 adopts a distinct conformation, forming additional trimer contacts and filling the bowl-shaped concavity observed at the tip of the DEN-2 sE trimer

Identification and Characterization of JAK2 Pseudokinase Domain Small Molecule Binders

Janus kinases (JAKs) regulate hematopoiesis via the cytokine-mediated JAK-STAT signaling pathway. JAKs contain tandem C-terminal pseudokinase (JH2) and tyrosine kinase (JH1) domains. The JAK2 pseudokinase domain adopts a protein kinase fold and, despite its pseudokinase designation, binds ATP with micromolar affinity. Recent evidence shows that displacing ATP from the JAK2 JH2 domain alters the hyperactivation state of the oncogenic JAK2 V617F protein while sparing the wild type JAK2 protein. In this study, small molecule binders of JAK2 JH2 were identified via an <i>in vitro</i> screen. Top hits were characterized using biophysical and structural approaches. Development of pseudokinase-selective compounds may offer novel pharmacological opportunities for treating cancers driven by JAK2 V617F and other oncogenic JAK mutants