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Targeting tryptophan is a promising strategy to achieve high levels of selectivity for peptide or protein modification. A chemoselective peptide modification method via photocatalytic tryptophan β-position conjugation has been discovered. This transformation has good substrate scope for both peptide and Michael acceptor, and has good chemoselectivity versus other amino acid residues. The endogenous peptides, glucagon and GLP-1 amide, were both successfully conjugated at the tryptophan β-position. Insulin was studied as a nontryptophan control molecule, resulting in exclusive B-chain C-terminal-selective decarboxylative conjugation. This transformation provides a novel approach toward peptide modification to support the discovery of new therapeutic peptides, protein labeling and bioconjugation. [ABSTRACT FROM AUTHOR]

Rationale During the development of a novel synthetic route to doravirine ( 1), a human immunodeficiency type 1 virus (HIV-1) nonnucleoside reverse transcriptase inhibitor (NNRTI), an unanticipated reaction intermediate, methyl ( Z)-2-(3-chloro-5-cyanophenoxy)-5-(3-(3-chloro-5-cyanophenoxy)-2-oxo-4-(trifluoromethyl)pyridin-1(2 H)-yl)-5-ethoxy-3-(trifluoromethyl)pent-2-enoate ( 2), was isolated. Moreover, an unusual electrospray ionization (ESI)-induced fragmentation was observed for 2. Hence, efforts were made towards the understanding of the structure of 2, which was crucial for the understanding of the reaction mechanism. Methods The isolated impurity was fully characterized by liquid chromatography coupled with high-resolution tandem mass spectrometry (LC/HRMS/MS), hydrogen/deuterium (H/D) exchange, and an ensemble of two-dimensional nuclear magnetic resonance (2D-NMR) techniques. Density functional theory (DFT) calculations were also conducted. Results An unusual ESI-induced fragmentation was observed for intermediate 2, giving an ion for half of the molecule in the positive ion mode, with the other half of the molecule affording an ion in the negative ion mode. Conclusions To the best of our knowledge, this unique ESI-induced fragmentation has not been previously reported in the literature. The underlying mechanism was explored and is supported by DFT calculations, which could greatly help the structural characterization of unknown impurities with similar structural features using ESI-MS in the future. Copyright © 2017 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Objective To demonstrate the effect of the screw-home motion on the stability of the patellofemoral joint, and investigate its mechanism of regulation of patellar tracking. Methods Twenty volunteers who met the criteria were examined. All subjects had axial computed tomography ( CT) scanning performed on bilateral knees at 0° and 30° of flexion. Scanning began above the femorotibial articulation and femoral trochlear groove, and moved sequentially down to the level of the anterior tibial tubercle. The following measurements were obtained: tibial rotation relative to the femur ( TRRF), tibial tuberosity-trochlear groove ( TT- TG) distance, lateral patellar displacement ( LPD), patellar tilt angle ( PTA), and congruence angle ( CA). We assessed the change (Δ) in each variable at both flexion angles, and analyzed this to investigate the corresponding relationship between the patella, the femur, and the screw-home mechanism. The differences between the values measured at 0° and those measured at 30° flexion were analyzed using the paired sample t-test. The differences between men and women were analyzed using the t-test. Pearson's correlations were performed to determine the relationship between Δ TT- TG distance and Δ LPD, Δ PTA and Δ TRRF, and Δ CA and Δ TRRF. Results There were 10 women and 10 men enrolled in the present study, with an average age of 25 years and an average body mass index of 21.8 kg/m2, and all volunteers had no history of knee injuries. Compared with measurements taken at 0° flexion, TRRF at 30° flexion was significantly increased, and the PTA, CA, LPD, and TT- TG distance were significantly decreased (all P < 0.01). There was no difference between men and women at 0° and 30° flexion, respectively ( P < 0.01). In this respect, there was no sex difference, but the change was greater for men than for women. Both Δ PTA and Δ CA demonstrated significant correlation with the Δ TRRF (both P < 0.01); a significant correlation between Δ LPD and Δ TT-TG distance was also demonstrated ( P < 0.01). Conclusions As the tibiofemoral joint rotated, the patellofemoral joint became more stable and aligned, which indicates that the screw-home mechanism plays an important role in regulating patellofemoral joint alignment. [ABSTRACT FROM AUTHOR]

World Health Organization estimates that 34 million individuals globally are living with Human Immunodeficiency Virus (HIV). Doravirine is a non-nucleoside reverse transcriptase inhibitors (NNRTI) being evaluated by Merck for the treatment of HIV-1 infection. Drug regulation authorities require the purity of a pharmaceutical to be fully defined. This is important to ensure that the pharmacological and toxicological effects are truly those of the drug substances and not because of the impurities. Thus, understanding the drug impurity profiles is critical to the safety and potency assessment of the drug candidate for clinical trials. The impurity characterization can also provide useful information for critical assessment of pharmaceutical processes. Advances in mass spectrometry instrumentation and methods allow the identification of impurities in pharmaceuticals with a minimum of sample material and increased sensitivity. In this study, a rapid and sensitive method was developed for the structural determination of the major impurities of doravirine. The study utilizes ultra performance liquid chromatography-high-resolution-tandem mass spectrometry (UHPLC-HRMS/MS) techniques to perform structure elucidation of the unknown structures. This approach has significant impact on impurity structural elucidation, and a total of five trace-level impurities of doravirine were characterized using the developed method. [ABSTRACT FROM AUTHOR]

The KCNN4 potassium-ion channel has been reported to play an important role in regulating antigen-induced T cell effector functions in vitro. This study presents the first evidence that a selective KCNN4 blocker, TRAM-34, confers protection against experimental autoimmune encephalomyelitis (EAE) in the mouse model. Treatment with the KCNN4 blocker did not prevent infiltration of T cells in the spinal cord, but resulted in the reduction of both the protein and the message levels of TNF-α and IFN-γ as well as the message levels of several other pro-inflammatory molecules in the spinal cord. Plasma concentrations of TRAM-34 within a 24-h period were between the in vitro IC and IC values for the KCNN4 channel. The effect of TRAM-34 was reversible, as indicated by the development of clinical EAE symptoms within 48 h after withdrawal of treatment. In summary, our data support the idea that KCNN4 channels play a critical role in the immune response during the development of MOG-induced EAE in C57BL/6 mice. See accompanying Commentary: [ABSTRACT FROM AUTHOR]

• A highly efficient decontamination method was developed for ceftolozane as well as other cephalosporin antibiotics. • UHPLC-HRMS/MS method is sensitive and efficient for the detection, identification and characterization of beta-lactam-ring destruction. • The presence of an intact beta-lactam-ring structure was characterized by the detection of CO loss in LC/HRMS/MS. The β-lactam core is a key structure responsible for inducing both IgE-mediated acute-onset hypersensitivity and T-cell-mediated delayed-onset hypersensitivity with penicillins in humans. There is essentially no clinically significant immunologic cross-reactivity noted between the β-lactam cores of penicillins and cephalosporins based on challenge studies in humans. The side-chains appear to be more important in inducing IgE-mediated acute-onset hypersensitivity and T-cell delayed-onset hypersensitivity with cephalosporins in humans. Despite these clinical findings, the U. S. Food and Drug Administration (FDA) still requires the level of β-lactam-related antibiotic residues to be controlled at very low levels in manufacturing facilities. Ceftolozane is Merck & Co., Inc., Kenilworth, NJ, USA's (MSD's) 5th generation broad spectrum cephalosporin antibiotic against gram-negative bacteria. In searching for the optimal decontamination method of ceftolozane, most methods were found to be very slow in opening the β-lactam ring in ceftolozane. Moreover, most of the previously reported decontamination methods applied analytical methods that only monitored the disappearance of the parent molecule as the endpoint of degradation. In this way, many of the β-lactam-containing degradation products could be overlooked. In order to develop an efficient decontamination solution for ceftolozane, a sensitive ultra high performance liquid chromatography-high resolution-electrospray ionization-tandem mass spectrometry (UHPLC-HRMS/MS) method was first developed to ensure the detection of the β-lactam ring in all degradation products. Through online UHPLC-UV-HRMS monitoring, 2.5 N KOH in 50% aqueous MeOH or 50% aqueous EtOH was identified as the best condition to fully degrade the β-lactam ring in ceftolozane. This decontamination could be done within 15 min, even at 100 mg/mL concentration, and thus enable a quick turnaround time for equipment cleaning in the β-lactam manufacturing facility. This method was also successfully applied to 12 other commercially available β-lactam antibiotics. [ABSTRACT FROM AUTHOR]

New synthetic methods were developed for the preparation of 2,3,6-trisubstituted 1-oxo-1,2-dihydroisoquinolines as CRTh 2 antagonists. The isoquinolinone core could be constructed before the introduction of substitution groups or synthesized through a catalytic intramolecular cyclization reaction with desired substitution groups properly installed. These synthetic strategies have helped to accelerate the SAR development of this series, and potent lead compounds were identified in both the CRTh 2 receptor binding assay and the CD11b biomarker assay. [ABSTRACT FROM AUTHOR]

The application of microwave assisted modification of the Akabori hydrazinolysis reaction has been found to cleave cyclic oligopeptides in a selective fashion to produce mainly the hydrazide of a specific linear peptide. This ring cleavage requires a few minutes of reaction in a domestic microwave oven. The linear peptide hydrazide can be analyzed by ESI-MS/MS, FAB-MS, and FAB-MS/MS methods for the determination of the amino acid sequence. [Copyright &y& Elsevier]