The Experts below are selected from a list of 306 Experts worldwide ranked by ideXlab platform
Nicholas J White - One of the best experts on this subject based on the ideXlab platform.
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alpha 1 acid glycoProtein orosomucoid and plasma Protein Binding of quinine in falciparum malaria
British Journal of Clinical Pharmacology, 1991Co-Authors: Kamolrat Silamut, P Molunto, May Ho, Timothy M E Davis, Nicholas J WhiteAbstract:1. Plasma concentrations of alpha 1-acid glycoProtein (AAG) and plasma Protein Binding of quinine were measured in 97 Thai adults with acute falciparum malaria. There was a linear relationship between log AAG and percentage quinine Binding (r = 0.71, P less than 0.001) in vivo, which was similar to that observed in vitro; the slopes and intercepts of the regression lines at AAG concentrations of 1 g l-1 were -8.94 and -8.41, and 7.2% and 10.9%, respectively. 2. Hill plots from these data suggest a single high affinity quinine Binding site on each molecule of AAG. 3. Plasma AAG concentrations were consistently raised in acute malaria, and were higher in patients with cerebral malaria [2.03 (0.51) g l-1, mean (s.d.)], and conscious patients with severe malaria [1.93 (0.53) g l-1] than in patients with uncomplicated infections [1.55 (0.58) g l-1], P = 0.008. Plasma Protein Binding of quinine was correspondingly higher and thus the proportion of free drug was lower in the severe groups; 5.5 (2.4)% compared with 7.2 (1.9)%, P = 0.03. 4. Following recovery from malaria, plasma AAG concentrations fell by an estimated 0.05 g l-1 day-1 to levels that were approximately half (median 45%) the admission value at 28 days. 5. AAG is the principal Binding Protein for quinine in plasma. Changes in plasma concentrations of this acute phase reactant account for the increased plasma Protein Binding of quinine in acute malaria.
Mikael Rehngren - One of the best experts on this subject based on the ideXlab platform.
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high throughput screening of Protein Binding by equilibrium dialysis combined with liquid chromatography and mass spectrometry
Journal of Chromatography A, 2006Co-Authors: Hong Wan, Mikael RehngrenAbstract:A new approach for screening plasma Protein Binding is presented. The method is based on equilibrium dialysis combined with rapid generic LC-MS bioanalysis by using a sample pooling approach enabling high-throughput screening of Protein Binding in the drug discovery phase. The method is evaluated by a comparison of measured unbound free fractions f(u) (%) between single and pooled compounds for a test set of structurally diverse compounds with a wide range of unbound fractions. Test compounds include 1 acidic and 10 basic drug standards along with 36 new chemical entities. A good correlation (R2>0.95) of f(u) (%) between the single and pooled compounds is found, suggesting that at least 10 compounds can be simultaneously measured with acceptable accuracy. A simplified drug-Protein Binding model is applied to calculate the f(u) (%) of drugs at various drug and Protein concentrations and this is applied to elucidate the applicability of the sample pooling approach from a theoretical standpoint. Moreover, pH shifts in the plasma were observed after dialysis when using different types of buffers and the impact of that on the f(u) is illustrated in association with their physicochemical properties, in particular the ionization state of compounds by the profile of effective mobility as a function of pH. A new buffer is proposed being able to minimize the pH shift of plasma during the dialysis. In addition, the application of the proposed buffer does not necessarily require adjusting plasma pH before the dialysis and utilizing a CO2 incubator during the dialysis. The effect of the ionic strengths of different buffers on MS signals is investigated with regard to ion suppression. The sample pooling method not only significantly reduces the plasma volume required but also the number of bioanalysis samples as compared to the single compound measurements by a conventional approach. The new proposed approach is especially beneficial for measuring in vitro Protein Binding in matrices such as mouse plasma where plasma is available only in limited amounts. The current new development will facilitate the drug discovery process by more rapidly assessing the Protein Binding potential of drug candidates.
Kenneth R Korzekwa - One of the best experts on this subject based on the ideXlab platform.
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impact of ph on plasma Protein Binding in equilibrium dialysis
Molecular Pharmaceutics, 2008Co-Authors: Christopher J Kochansky, Daniel R Mcmasters, Kenneth A Koeplinger, Haley H Kerr, Magang Shou, Kenneth R KorzekwaAbstract:Many pharmacokinetic analyses require unbound plasma concentrations, including prediction of clearance, volume of distribution, drug-drug interactions, brain uptake analysis, etc. It is most often more convenient to measure the total drug concentration in plasma rather than the unbound drug concentration. To arrive at unbound plasma concentrations, separate in vitro determinations of the plasma Protein Binding of a drug are usually carried out in serum or in plasma, and the plasma pharmacokinetic results are then mathematically adjusted by this fraction unbound ( f u,p). Plasma Protein Binding or the drug fraction unbound in plasma ( f u,p) is known to be affected by Protein, drug, free fatty acid concentrations, lipoProtein partitioning, temperature, pH, and the presence or absence of other drugs/displacing agents within plasma samples. Errors in f u,p determination caused by lack of adequate pH control in newer assay formats for plasma Protein Binding (e.g., 96-well equilibrium thin walled polypropylene dialysis plates) will have significant drug-specific impact on these pharmacokinetic calculations. Using a diverse set of 55 drugs and a 96-well equilibrium dialysis plate format, the effect of variable pH during equilibrium dialysis experiments on measured values of f u,p was examined. Equilibrium dialysis of human plasma against Dulbecco's phosphate buffered saline at 37 degrees C under an air or 10% CO 2 atmosphere for 22 h resulted in a final pH of approximately 8.7 and 7.4, respectively. The ratio of f u,p at pH 7.4 (10% CO 2) vs pH 8.7 (air) was >or=2.0 for 40% of the 55 compounds tested. Only one of the 55 compounds tested had a ratio <0.9. Select compounds were further examined in rat and dog plasma. In addition, physicochemical properties were calculated for all compounds using ACD/Labs software or Merck in-house software and compared to plasma Protein Binding results. Changes in plasma Protein Binding due to pH increases which occurred during the equilibrium dialysis experiment were not species specific but were drug-specific, though nonpolar, cationic compounds had a higher likely hood of displaying pH-dependent Binding. These studies underscore the importance of effectively controlling pH in plasma Protein Binding studies.
Hong Gao - One of the best experts on this subject based on the ideXlab platform.
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automation of plasma Protein Binding assay using rapid equilibrium dialysis device and tecan workstation
Journal of Pharmaceutical and Biomedical Analysis, 2017Co-Authors: Craig Zetterberg, Hong GaoAbstract:Binding of drug molecules to plasma Proteins is an important parameter in assessing drug ADME properties. Plasma Protein Binding (PPB) assays are routinely performed during drug discovery and development. A fully automated PPB assay was developed using rapid equilibrium dialysis (RED) device and Tecan workstation coupled to an automated incubator. The PPB assay was carried out in unsealed RED plates which allowed the assay to be fully automated. The plasma pH was maintained at 7.4 during the 6-h dialysis under 2% CO2 condition. The samples were extracted with acetonitrile and analyzed by liquid chromatography tandem mass spectrometry. The percent bound results of 10 commercial drugs in plasma Protein Binding were very similar between the automated and manual assays, and were comparable to literature values. The automated assay increases laboratory productivity and is applicable to high-throughput screening of drug Protein Binding in drug discovery.
Tony Velkov - One of the best experts on this subject based on the ideXlab platform.
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plasma Protein Binding structure activity relationships related to the n terminus of daptomycin
ACS Infectious Diseases, 2017Co-Authors: Elena K. Schneider, Johnny X. Huang, Mark E. Cooper, Vincenzo Carbone, Meiling Han, Yan Zhu, Sue C Nang, Keith K Khoo, Johnson Mak, Tony VelkovAbstract:Daptomycin is a lipopeptide antibiotic that is highly bound to plasma Proteins. To date, the plasma components and structure–activity relationships responsible for the plasma Protein Binding profile of daptomycin remain uncharacterized. In the present study we have employed a surface plasmon resonance assay together with molecular docking techniques to investigate the plasma Protein Binding structure–activity relationships related to the N-terminal fatty acyl of daptomycin. Three compounds were investigated: (1) native daptomycin, which displays an N-terminal n-decanoyl fatty acid side chain, and two analogues with modifications to the N-terminal fatty acyl chain; (2) des-acyl daptomycin; and (3) acetyl-daptomycin. The surface plasmon resonance (SPR) data showed that the Binding profile of native daptomycin was in the rank order human serum albumin (HSA) ≫ α-1-antitrypsin > low-density lipoProtein ≥ hemoglobin > sex hormone Binding globulin > α-1-acid-glycoProtein (AGP) > hemopexin > fibrinogen > α-2-macr...
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the plasma Protein Binding proteome of ertapenem a novel compound centric proteomic approach for elucidating drug plasma Protein Binding interactions
ACS Chemical Biology, 2016Co-Authors: Mark Baker, Elena K. Schneider, Johnny X. Huang, Mark E. Cooper, Tony VelkovAbstract:Ertapenem is an important first-line carbapenem antibiotic used for the treatment of aerobic Gram-negative bacterial infections. It is the only marketed carbapenem that is highly bound to plasma Proteins and displays a concentration-dependent and saturable plasma Protein Binding profile. To date, the plasma components responsible for sequestering ertapenems antibacterial activity remain uncharacterized. In the present study, we have employed an orthogonal, multiplatform approach, including novel compound-centric displacement proteomics and surface plasmon resonance to characterize the plasma Protein Binding proteome of ertapenem. In proof-of-concept, the capacity of physiological cocktails of the identified plasma Proteins to inhibit the antibacterial activity of ertapenem was assessed with in vitro microbiological assays. We show that fibrinogen, complement C4, haptoglobulin, α-1-antitrypsin, fibronectin, transferrin, immunoglobulin G, hemopexin, and humans serum albumin are responsible for the majority ...
