Hydrogen Bond Synthons in the Interplay of Solubility and Membrane Permeability/Diffusion in Variable Stoichiometry Drug Cocrystals

2015 ◽  
Vol 15 (11) ◽  
pp. 5593-5603 ◽  
Author(s):  
Basanta Saikia ◽  
Pranita Bora ◽  
Rajiv Khatioda ◽  
Bipul Sarma
Keyword(s):  
Hydrogen Bond ◽  
Membrane Permeability ◽  
Variable Stoichiometry

Na+-K+ pump stoichiometry and basolateral membrane permeability of frog corneal epithelium

1986 ◽  
Vol 250 (5) ◽  
pp. F850-F859 ◽  
Author(s):  
O. A. Candia ◽  
P. Cook
Keyword(s):  
Membrane Permeability ◽  
Amphotericin B ◽  
Corneal Epithelium ◽  
Flow Condition ◽  
Basolateral Membrane ◽  
Flux Ratio ◽  
Na Currents ◽  
Static Head ◽  
K Permeability ◽  
Variable Stoichiometry

The Na+-K+ pump flux ratio and the Na+ and K+ permeability of the basolateral membrane of the isolated frog corneal epithelium were studied with the aid of microelectrodes by analyzing the effects of ouabain, Ba2+, and amphotericin B. The experiments were done in Cl(-)-free solutions, a situation that approximates that of static head. Ouabain produced a quick depolarization of the potential difference across the basolateral membrane (PDb) from -72 to -62 mV without a change in resistance. Ba2+ (3 mM) rapidly lowered PDb from -74 to -57 mV and decreased the apical-to-basolateral resistance ratio. The effects of ouabain and Ba2+ were additive. The Na+-K+ flux ratio at the pump was calculated to be 1.78, substantially less than when the tissue is in a level flow condition, suggesting a variable stoichiometry. The K+ and Na+ resistances of the basolateral membrane were 15.7 and 5.5 k omega X cm2, respectively, allowing K+ and Na+ currents that approximately matched those produced by the Na+-K+ pump. The resistance of the basolateral membrane (4.0 k omega X cm2) was double that reported in Cl(-)-rich solutions, suggesting that Cl- contributes to the conductance of this membrane.

scholarly journals A new amino acid for improving permeability and solubility in macrocyclic peptides through side chain-to-backbone hydrogen bonding.

2022 ◽  
Author(s):  
Jaru Taechalertpaisarn ◽  
Satoshi Ono ◽  
Okimasa Okada ◽  
Timothy C. Johnstone ◽  
R. Scott Lokey
Keyword(s):  
Hydrogen Bond ◽  
Membrane Permeability ◽  
Cyclic Peptides ◽  
Cyclic Peptide ◽  
Aqueous Solubility ◽  
Side Chain ◽  
Dependent Manner ◽  
Peptide Backbone ◽  
Cyclic Hexapeptide ◽  
Intramolecular Hydrogen

Despite the notoriously poor membrane permeability of peptides in general, many cyclic peptide natural products show high passive membrane permeability and potently inhibit a variety of “undruggable” intracellular targets. A major impediment to designing cyclic peptides with good permeability is the high desolvation energy associated with the peptide backbone amide NH groups. Strategies for mitigating the deleterious effect of the backbone NH group on permeability include N-methylation, steric occlusion, and the formation of intramolecular hydrogen bonds with backbone carbonyl oxygens, while there have been relatively few studies on the use of polar side chains to sequester backbone NH groups. We investigated the ability of N,N-pyrrolidinyl glutamine (Pye), whose side chain contains a powerful hydrogen bond accepting C=O amide group but no hydrogen bond donors, to sequester exposed backbone NH groups in a series of cyclic hexapeptide diastereomers. Analyses of partition coefficients, lipophilic permeability efficiencies (LPE), artificial and cell-based permeability assays revealed that specific Leu-to-Pye substitutions conferred dramatic improvements in aqueous solubility and permeability in a scaffold- and position-dependent manner. Introduction of the Pye residue thus offers a complementary tool, alongside traditional approaches, for improving membrane permeability and solubility in cyclic peptides.

Initial Polymerization Sites Indicated During Mitochondrial Oxidation of Diaminobenzidine after Toluene Treatment

1977 ◽  
Vol 35 ◽  
pp. 408-409
Author(s):  
W. A. Shannon ◽  
M. A. Matlib
Keyword(s):  
Membrane Permeability ◽  
Cytochrome Oxidase ◽  
Rat Liver ◽  
Precise Definition ◽  
Cytochemical Localization ◽  
Oxidative Reaction ◽  
Mitochondrial Oxidation ◽  
Definition Of ◽  
Exogenous Substrates

Numerous studies have dealt with the cytochemical localization of cytochrome oxidase via cytochrome c. More recent studies have dealt with indicating initial foci of this reaction by altering incubation pH (1) or postosmication procedure (2,3). The following study is an attempt to locate such foci by altering membrane permeability. It is thought that such alterations within the limits of maintaining morphological integrity of the membranes will ease the entry of exogenous substrates resulting in a much quicker oxidation and subsequently a more precise definition of the oxidative reaction.The diaminobenzidine (DAB) method of Seligman et al. (4) was used. Minced pieces of rat liver were incubated for 1 hr following toluene treatment (5,6). Experimental variations consisted of incubating fixed or unfixed tissues treated with toluene and unfixed tissues treated with toluene and subsequently fixed.

Sarcolemmal permeability changes during early myocardial anoxia

1978 ◽  
Vol 36 (2) ◽  
pp. 642-643
Author(s):  
M. Ashraf ◽  
L. Landa ◽  
L. Nimmo ◽  
C. M. Bloor
Keyword(s):  
Cell Membrane ◽  
Membrane Permeability ◽  
Coronary Artery Occlusion ◽  
Artery Occlusion ◽  
Cell Membrane Permeability ◽  
Enzyme Release ◽  
Sprague Dawley ◽  
Sprague Dawley Rats ◽  
Sarcolemmal Permeability ◽  
Membrane Changes

Following coronary artery occlusion, the myocardial cells lose intracellular enzymes that appear in the serum 3 hrs later. By this time the cells in the ischemic zone have already undergone irreversible changes, and the cell membrane permeability is variably altered in the ischemic cells. At certain stages or intervals the cell membrane changes, allowing release of cytoplasmic enzymes. To correlate the changes in cell membrane permeability with the enzyme release, we used colloidal lanthanum (La+++) as a histological permeability marker in the isolated perfused hearts. The hearts removed from sprague-Dawley rats were perfused with standard Krebs-Henseleit medium gassed with 95% O2 + 5% CO2. The hypoxic medium contained mannitol instead of dextrose and was bubbled with 95% N2 + 5% CO2. The final osmolarity of the medium was 295 M osmol, pH 7. 4.

Synthetic marine guanidines are effective antileishmanial compounds by altering the plasma membrane permeability

Planta Medica ◽  
2014 ◽  
Vol 80 (16) ◽  
Author(s):  
AG Tempone ◽  
LF Martins ◽  
EG Pinto ◽  
JT Mesquita ◽  
EL Bennett ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Membrane Permeability ◽  
Plasma Membrane Permeability
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