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31.
Using full atomistic classical molecular dynamics simulations, the interfacial properties of free-standing poly(3-hexylthiophene) (P3HT) films have been investigated. The orientations of different parts of the P3HT chain and the surface tensions of the films were calculated in a temperature range of 540 K-600 K. At the liquid/vacuum interface, the P3HT chain shows ordering by exposing hexyl groups at the interface, while the chain backbone lays flat with the thiophene ring preferentially tilt toward the surface. At the interface, the terminal methyl groups of hexyl side chains are in excess compared to the methylene groups or thiophene rings. The surface tension of P3HT in its melt state shows similar temperature dependence to that of polymers that have long alkyl side chains. The surface tension values are comparable to those polymers that expose methyl or methylene groups on the surface. The surface tension values determined for the melt state are lower than the experimental reported values for crystalline P3HT films, as expected. 相似文献
32.
Wang SJ Wu ST Gokemeijer J Fura A Krishna M Morin P Chen G Price K Wang-Iverson D Olah T Weiner R Tymiak A Jemal M 《Analytical and bioanalytical chemistry》2012,402(3):1229-1239
High-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) and enzyme-linked immunosorbent assay (ELISA) methods were developed for the quantification of a PEGylated scaffold protein drug in monkey plasma samples. The LC-MS/MS method was based on the extraction of the therapeutic protein with a water-miscible organic solvent and the subsequent trypsin digestion of the extract followed by the detection of a surrogate peptide. The assay was linear over a range of 10-3,000 ng/mL. The ELISA method utilized a therapeutic target-binding format in which the recombinant target antigen was used to capture the drug in the sample, followed by detection with an anti-PEG monoclonal antibody. The assay range was 30-2,000 ng/mL. A correlation study between the two methods was performed by measuring the drug concentrations in plasma samples from a single-dose pharmacokinetic (PK) study in cynomolgus monkeys following a 5-mg/kg subcutaneous administration (n = 4). In the early time points of the PK profile, the drug concentrations obtained by the LC-MS/MS method agreed very well with those obtained by the ELISA method. However, at later time points, the drug concentrations measured by the LC-MS/MS method were consistently higher than those measured by the ELISA method. The PK parameters calculated based on the concentration data showed that the two methods gave equivalent peak exposure (C(max)) at 24-48 h. However, the LC-MS/MS results exhibited about 1.53-fold higher total exposure (AUC(tot)) than the ELISA results. The discrepancy between the LC-MS/MS and ELISA results was investigated by conducting immunogenicity testing, anti-drug antibody (ADA) epitope mapping, and Western blot analysis of the drug concentrations coupled with Protein G separation. The results demonstrated the presence of ADA specific to the engineered antigen-binding region of the scaffold protein drug that interfered with the ability of the drug to bind to the target antigen used in the ELISA method. In the presence of the ADAs, the ELISA method measured only the active circulating drug (target-binding), while the LC-MS/MS method measured the total circulating drug. The work presented here indicates that the bioanalysis of protein drugs may be complicated owing to the presence of drug-binding endogenous components or ADAs in the post-dose (incurred) samples. The clear understanding of the behavior of different bioanalytical techniques vis-à-vis the potentially interfering components found in incurred samples is critical in selecting bioanalytical strategies for measuring protein drugs. 相似文献
33.
Wienkers M Ramos J Jemal H Cardenas C Wiget P Nelson A Free S Wu J Roach R Vulcan M Waynant K Fort K Vladimirova A Sun J Hunt SE Rudkevich DM Starnes SD 《Organic letters》2012,14(6):1370-1373
We present a fortuitous discovery of enhanced shape-selective recognition of anion guests that stems from a complexation-induced conformational change in porphyrin hosts upon anion binding. Porphyrin hosts reported here exist in a conformation that is not favorable to guest binding. Anions that bind strongly are those that can induce a conformational change in the host to allow guest binding. Furthermore, guests that mimic the shape of the newly formed pocket bind the strongest. 相似文献
34.
Yuan L Zhang D Jemal M Aubry AF 《Rapid communications in mass spectrometry : RCM》2012,26(12):1465-1474
35.
Alebachew D. Yimer Kudret Demirli 《International Journal of Approximate Reasoning》2009,50(1):117-137
In this paper, we present a mixed-integer fuzzy programming model and a genetic algorithm (GA) based solution approach to a scheduling problem of customer orders in a mass customizing furniture industry. Independent job orders are grouped into multiple classes based on similarity in style so that the required number of setups is minimized. The family of jobs can be partitioned into batches, where each batch consists of a set of consecutively processed jobs from the same class. If a batch is assigned to one of available parallel machines, a setup is required at the beginning of the first job in that batch. A schedule defines the way how the batches are created from the independent jobs and specifies the processing order of the batches and that of the jobs within the batches. A machine can only process one job at a time, and cannot perform any processing while undergoing a setup. The proposed formulation minimizes the total weighted flowtime while fulfilling due date requirements. The imprecision associated with estimation of setup and processing times are represented by fuzzy sets. 相似文献
36.
D Wang-Iverson E Ivashkiv M Jemal A I Cohen 《Rapid communications in mass spectrometry : RCM》1989,3(5):132-134
The acid form of lovastatin, an HMG-CoA reductase inhibitor, was analyzed by gas chromatography/negative-ion chemical ionization mass spectrometry after derivatization with pentafluorobenzyl bromide and bis-(trimethylsilyl)trifluoroacetamide (BSTFA). Mass spectrometry of this derivative produced a dominant [M-181]- ion under chemical ionization conditions using ammonia as the reagent gas. The limit of detection was approximately 2 pg injected on column. 相似文献
37.
(K?Na)NO3 and (K?Cs)NO3 phase diagrams were drawn using a simultaneous thermal analysis technique in the range 373 to 623 K. The first phase diagram shows a minimum freezing equimolar mixture at 494 K, a continuous solid solution in equilibrum with liquid phase and an eutectic mixture (88 molar % of KNO3) at 380 K. The second one exhibits an invariant at 400 K corresponding to the KNO3 solid-solid transition, an eutectoid mixture at 10 molar % of KNO3 and 418 K involving the CsNO3 solid-solid transition and an eutectic mixture at 60 molar % of KNO3 and 495 K. 相似文献
38.
Ben Abdelkader S. Ben Cherifa A. Coulet M. V. Khattech I. Rogez J. Jemal M. 《Journal of Thermal Analysis and Calorimetry》2004,77(3):863-871
Pure and well crystallised whitlockite Ca18Mg2H2(PO4)14 has been synthesized by precipitation from the magnesium and calcium nitrates and the diammonic phosphate. The product of
the reaction has been characterized by X-ray diffraction, IR spectroscopy and chemical analysis. Using differential conduction
calorimeters the enthalpies of solution of the whitlockite and of a mixture of the solid reactants - the tricalcium, the trimagnesium
and the dicalcium phosphates - have been measured at 25°C for various concentrations of solid in a 46 wt% nitric acid solution.
A combination of the enthalpies of solution with the enthalpies of formation of the reactants allows us to determine the standard
enthalpy of formation of the whitlockite. The value deduced, -27,93·103kJ mol-1, is compared to the standard enthalpies of formation of the trimagnesium and the tricalcium phosphates.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
39.
The GC method developed for the stereoisomeric purity determination of captopril is based on the combined information derived from the analyses of the captopril sample on two GC systems, one with a chiral and the other with an achiral column. The limit of detection has been determined to be 0.02% (w/w) for (R,S) or (S,R) and 0.03% for (R,R), with corresponding minimum quantifiable levels of 0.08% and 0.09%. 相似文献
40.
Validated liquid chromatography/tandem mass spectrometric (LC/MS/MS) methods are now widely used for quantitation of drugs in post-dose (incurred) biological samples for the assessment of pharmacokinetic parameters, bioavailability and bioequivalence. In accordance with the practice currently accepted within the pharmaceutical industry and the regulatory bodies, validation of a bioanalytical LC/MS/MS method is performed using standards and quality control (QC) samples prepared by spiking the drug (the analyte) into the appropriate blank biological matrix (e.g. human plasma). The method is then declared to be adequately validated for analyzing incurred biological samples. However, unlike QC samples, incurred samples may contain an epimer or another type of isomer of the drug, such as a Z or E isomer. Such a metabolite will obviously interfere with the selected reaction monitoring (SRM) transition used for the quantitation of the drug. The incurred sample may also contain a non-isomeric metabolite having a molecular mass different from that of the drug (such an acylglucuronide metabolite) that can still contribute to (and hence interfere with) the SRM transition used for the quantitation of the drug. The potential for the SRM interference increases with the use of LC/MS/MS bioanalytical methods with very short run times (e.g. 0.5 min). In addition, a metabolite can potentially undergo degradation or conversion to revert back to the drug during the multiple steps of sample preparation that precede the introduction of the processed sample into the LC/MS/MS system. In this paper, we recommend a set of procedures to undertake with incurred samples, as soon as such samples are available, in order to establish the validity of an LC/MS/MS method for analyzing real-life samples. First, it is recommended that the stability of incurred samples be investigated 'as is' and after sample preparation. Second, it is recommended that potential SRM interference be investigated by analyzing the incurred samples using the same LC/MS/MS method but with the additional incorporation of the SRM transitions attributable to putative metabolites (multi-SRM method). The metabolites monitored will depend on the expected metabolic products of the drug, which are predictable based on the functional groups present in the chemical structure of the drug. Third, it is recommended that potential SRM interference be further investigated by analyzing the incurred samples using the multi-SRM LC/MS/MS method following the modification of chromatographic conditions to enhance chromatographic separation of the drug from any putative metabolites. We will demonstrate the application of the proposed strategy by using a carboxylic acid containing drug candidate and its acylglucuronide as a putative metabolite. Plasma samples from the first-in-man (FIM) study of the drug candidate were used as the incurred samples. 相似文献