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71.
Dr. David Wifling Dr. Christopher Pfleger Jonas Kaindl Passainte Ibrahim Dr. Ralf C. Kling Prof. Dr. Armin Buschauer Prof. Dr. Holger Gohlke Prof. Dr. Timothy Clark 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(64):14613-14624
Histamine H4 receptor (H4R) orthologues are G-protein-coupled receptors (GPCRs) that exhibit species-dependent basal activity. In contrast to the basally inactive mouse H4R (mH4R), human H4R (hH4R) shows a high degree of basal activity. We have performed long-timescale molecular dynamics simulations and rigidity analyses on wild-type hH4R, the experimentally characterized hH4R variants S179M, F169V, F169V+S179M, F168A, and on mH4R to investigate the molecular nature of the differential basal activity. H4R variant-dependent differences between essential motifs of GPCR activation and structural stabilities correlate with experimentally determined basal activities and provide a molecular explanation for the differences in basal activation. Strikingly, during the MD simulations, F16945.55 dips into the orthosteric binding pocket only in the case of hH4R, thus adopting the role of an agonist and contributing to the stabilization of the active state. The results shed new light on the molecular mechanism of basal H4R activation that are of importance for other GPCRs. 相似文献
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[reaction: see text] Enantioselective total syntheses of belactosin A, belactosin C, and its homoanalogue have been accomplished in high overall yields (32% for belactosin A from the amino acid 10, and 35 and 36% for belactosin C and its homoanalogue, respectively). This concise approach comprises a novel sequential acylation/beta-lactonization reaction and allows a facile alteration of the substituents, thus providing a flexible route to a new family of highly active belactosin-based proteasome inhibitors. 相似文献
73.
Kratzsch C Tenberken O Peters FT Weber AA Kraemer T Maurer HH 《Journal of mass spectrometry : JMS》2004,39(8):856-872
A liquid chromatographic/mass spectrometric assay with atmospheric pressure chemical ionization (LC/APCI-MS) is presented for fast and reliable screening and identification and also for precise and sensitive quantification in plasma of the 23 benzodiazepines alprazolam, bromazepam, brotizolam, camazepam, chlordiazepoxide, clobazam, clonazepam, diazepam, flunitrazepam, flurazepam, desalkylflurazepam, lorazepam, lormetazepam, medazepam, metaclazepam, midazolam, nitrazepam, nordazepam, oxazepam, prazepam, temazepam and tetrazepam, triazolam, their antagonist flumazenil and the benzodiazepine BZ1 (omega 1) receptor agonists zaleplone, zolpidem and zopiclone. It allows confirmation of the diagnosis of an overdose situation and monitoring of psychiatric patients' compliance. The analytes were isolated from plasma using liquid-liquid extraction and were separated on a Merck LiChroCART column with Superspher 60 RP Select B as the stationary phase. Gradient elution was performed using aqueous ammonium formate and acetonitrile. After screening and identification in the scan mode using the authors' LC/MS library, the analytes were quantified in the selected-ion monitoring mode. The quantification assay was fully validated. It was found to be selective proved to be linear from sub-therapeutic to over therapeutic concentrations for all analytes, except bromazepam. The corresponding reference levels the assay's accuracy and precision data for all studied substances are listed. The accuracy and precision data were within the required limits with the exception of those for bromazepam. The analytes were stable in frozen plasma for at least 1 month. The validated assay was successfully applied to several authentic plasma samples from patients treated or intoxicated with various benzodiazepines or with zaleplone, zolpidem or zopiclone. It has proven to be appropriate for the isolation, separation, screening, identification and quantification of the drugs mentioned above in plasma for clinical toxicology, e.g. in cases of poisoning, and forensic toxicology, e.g. in cases of driving under the influence of drugs. 相似文献
74.
Werzer O Boucher N de Silva JP Gbabode G Geerts YH Konovalov O Moser A Novak J Resel R Sferrazza M 《Langmuir : the ACS journal of surfaces and colloids》2012,28(22):8530-8536
Temperature dependent structural and morphological investigations on semiconducting dioctyl-terthiophene (DOTT) thin films prepared on silica surfaces reveals the coexistence of surface induce order and distinct crystalline/liquid crystalline bulk polymorphs. X-ray diffraction and scanning force microscopy measurements indicate that at room temperature two polymorphs are present: the surface induced phase grows directly on the silica interface and the bulk phase on top. At elevated temperatures the long-range order gradually decreases, and the crystal G (340 K), smectic F (348 K), and smectic C (360 K) phases are observed. Indexation of diffraction peaks reveals that an up-right standing conformation of DOTT molecules is present within all phases. A temperature stable interfacial layer close to the silica-DOTT interface acts as template for the formation of the different phases. Rapid cooling of the DOTT sample from the smectic C phase to room temperature results in freezing into a metastable crystalline state with an intermediated unit cell between the room temperature crystalline phase and the smectic C phase. The understanding of such interfacial induced phases in thin semiconducting liquid crystal films allows tuning of crystallographic and therefore physical properties within organic thin films. 相似文献
75.
Grundmann M Rothenhöfer M Bernhardt G Buschauer A Matysik FM 《Analytical and bioanalytical chemistry》2012,402(8):2617-2623
Fast capillary electrophoresis–mass spectrometry measurements under counter-electroosmotic analyte migration conditions are
presented. Efficient separations of a homologous series of six hyaluronan oligosaccharides (comprising 1–6 hyalobiuronic acid
moieties) could be completed in 65 s. Separations were achieved in short-length fused silica capillaries under high electric
field strengths of up to 1.25 kV·cm−1. Capillary inner diameters ranging from 5 to 50 μm were investigated, resulting in an optimal value of 15 μm. The influence
of capillary dimensions and buffer composition on separation efficiency and sensitivity are discussed. Optimal separations
were achieved using a 28 cm × 15 μm capillary, a separation high voltage of 35 kV, a background electrolyte of 25 mM ammonium
acetate adjusted to pH 8.5, and negative ionization mode. The optimized method was successfully applied to a bovine testicular
hyaluronidase digest of hyaluronan. Only minimal sample pretreatment for protein-containing samples is required. The simple
manual injection procedure and fast separations allow for a sample throughput of 35 samples per hour. 相似文献
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Ali A. Mohammadi Armin Hadadzahmatkesh Mohammad R. Asghariganjeh 《Monatshefte für Chemie / Chemical Monthly》2012,124(5):931-933