Improving the accuracy of unbound fraction measurement of drug-protein binding by preconditioning the RED membrane inserts

Aim: The objective of this study was to evaluate the rapid equilibrium dialysis (RED) device in protein binding assays in diluted protein matrices and to improve the accuracy of the unbound fraction ( fu) measurement. Methodology: Protein binding assays of drug compounds in bovine serum albumin solutions and human plasma with different folds of dilution were performed using the RED device with and without preconditioning of the dialysis membrane inserts, and the results were compared with those using other approaches in this study. Results & conclusion: Preconditioning of the RED membrane inserts improved the fu data accuracy of drug-protein binding assay in matrices with relatively low protein contents and such impact could be compound dependent.

Recurrent Hypoglycemia in a Case of Congenital Analbuminemia

In congenital analbuminemia (CAA), mutations in the albumin gene result in a severe deficiency or absence of plasma albumin. Only about 90 cases have been reported to date, but the specific features of glucose and lipid metabolism in congenital analbuminemia have only been studied in a rat model of analbuminemia. We report the case of a female patient hospitalized for a streptococcal skin infection who showed recurrent hypoglycemia. A diagnosis of CAA was confirmed by mutation analysis and by the detection of a single base variation in the ALB gene. Hypoglycemia was first documented after a fasting period during acute illness. Recurrent hypoglycemia persisted despite good general condition and normal nutrition during antimicrobial therapy with moxifloxacin. Several contributing factors causing this hypoglycemia can be discussed. Individuals with CAA are prone to adverse drug effects caused by changes in drug-protein binding properties. It is unclear if specific changes of glucose and lipid metabolism in CAA constitute a risk factor for hypoglycemia.

Spotting Differences in Molecular Dynamic Simulations of Influenza A M2 Protein-Ligand Complexes by Varying M2 construct, Lipid Bilayer and Force Field

<p>We studied by molecular dynamic (MD) simulations systems including the inward_closed state of influenza A M2 protein in complex with aminoadamantane drugs in membrane bilayers. We varied the M2 construct and performed MD simulations in M2TM or M2TM with amphipathic helices (M2AH). We also varied the lipid bilayer by changing either the lipid, DMPC or POPC, POPE or POPC/cholesterol (chol), or the lipids buffer size, 10x10 Ųor 20x20 Ų. We aimed to suggest optimal system conditions for the computational description of this ion channel and related systems. Measures performed include quantities that are available experimentally and include: (a) the position of ligand, waters and chlorine anion inside the M2 pore, (b) the passage of waters from the outward Val27 gate of M2 S31N in complex with an aminoadamantane-aryl head blocker, (c) M2 orientation, (d) the AHs conformation and structure which is affected from interactions with lipids and chol and is important for membrane curvature and virus budding. In several cases we tested OPLS2005, which is routinely applied to describe drug-protein binding, and CHARMM36 which describes reliably protein conformation. We found that for the description of the ligands position inside the M2 pore, a 10x10 Ų lipids buffer in DMPC is needed when M2TM is used but 20x20 Ų lipids buffer of the softer POPC; when M2AH is used all 10x10 Ų lipid buffers with any of the tested lipids can be used. For the passage of waters at least M2AH with a 10x10 Ų lipid buffer is needed. The folding conformation of AHs which is defined from hydrogen bonding interactions with the bilayer and the complex with chol is described well with a 10x10 Ų lipids buffer and CHARMM36. </p>

Spotting Differences in Molecular Dynamic Simulations of Influenza A M2 Protein-Ligand Complexes by Varying M2 construct, Lipid Bilayer and Force Field

<p>We studied by molecular dynamic (MD) simulations systems including the inward_closed state of influenza A M2 protein in complex with aminoadamantane drugs in membrane bilayers. We varied the M2 construct and performed MD simulations in M2TM or M2TM with amphipathic helices (M2AH). We also varied the lipid bilayer by changing either the lipid, DMPC or POPC, POPE or POPC/cholesterol (chol), or the lipids buffer size, 10x10 Ųor 20x20 Ų. We aimed to suggest optimal system conditions for the computational description of this ion channel and related systems. Measures performed include quantities that are available experimentally and include: (a) the position of ligand, waters and chlorine anion inside the M2 pore, (b) the passage of waters from the outward Val27 gate of M2 S31N in complex with an aminoadamantane-aryl head blocker, (c) M2 orientation, (d) the AHs conformation and structure which is affected from interactions with lipids and chol and is important for membrane curvature and virus budding. In several cases we tested OPLS2005, which is routinely applied to describe drug-protein binding, and CHARMM36 which describes reliably protein conformation. We found that for the description of the ligands position inside the M2 pore, a 10x10 Ų lipids buffer in DMPC is needed when M2TM is used but 20x20 Ų lipids buffer of the softer POPC; when M2AH is used all 10x10 Ų lipid buffers with any of the tested lipids can be used. For the passage of waters at least M2AH with a 10x10 Ų lipid buffer is needed. The folding conformation of AHs which is defined from hydrogen bonding interactions with the bilayer and the complex with chol is described well with a 10x10 Ų lipids buffer and CHARMM36. </p>