Spontaneous and enzyme-induced dimer formation and its role in membrane permeability I. The permeability of non-electrolytes at high concentration

1962 ◽  
Vol 59 (1) ◽  
pp. 35-46 ◽  
Author(s):  
W.D. Stein
Keyword(s):  
Membrane Permeability ◽  
High Concentration ◽  
Dimer Formation

scholarly journals Combined Effect of Nitrofurantoin and Plant Surfactant on Bacteria Phospholipid Membrane

Molecules ◽  
2020 ◽  
Vol 25 (11) ◽  
pp. 2527
Author(s):  
Monika Rojewska ◽  
Wojciech Smułek ◽  
Krystyna Prochaska ◽  
Ewa Kaczorek
Keyword(s):  
Membrane Permeability ◽  
Adsorption Properties ◽  
Bacterial Cells ◽  
Phospholipid Membrane ◽  
High Concentration ◽  
Natural Surfactants ◽  
Wide Perspective ◽  
Environmental Bacteria ◽  
Achromobacter Sp ◽  
Saponaria Officinalis

Due to the increasing use of antibiotics, measures are being taken to improve their removal from the natural environment. The support of biodegradation with natural surfactants that increase the bioavailability of impurities for microorganisms that degrade them, raises questions about their effect on bacterial cells. In this paper we present analysis of the interaction of nitrofurantoin (NFT) and saponins from the Saponaria officinalis on the environmental bacteria membrane and the model phospholipid membrane mimicking it. A wide perspective of the process is provided with the Langmuir monolayer technique and membrane permeability test with bacteria. The obtained results showed that above critical micelle concentration (CMC), saponin molecules are incorporated into the POPE monolayer, but the NFT impact was ambiguous. What is more, differences in membrane permeability between the cells exposed to NFT in comparison to that of the non-exposed cells were observed above 1.0 CMC for Achromobacter sp. KW1 or above 0.5 CMC for Pseudomonas sp. MChB. In both cases, NFT presence lowered the membrane permeability. Moreover, the Congo red adhesion to the cell membrane also decreased in the presence of a high concentration of surfactants and NFT. The results suggest that saponins are incorporated into the bacteria membrane, but their sugar hydrophilic part remains outside, which modifies the adsorption properties of the cell surface as well as the membrane permeability.

scholarly journals A D-dimer laboratóriumi eredményeinek és klinikai értékelésének elemzése

2017 ◽  
Vol 158 (50) ◽  
pp. 1971-1976
Author(s):  
János Jákó
Keyword(s):  
Kidney Disease ◽  
Enzymatic Degradation ◽  
Normal Values ◽  
Degradation Process ◽  
Diagnostic Value ◽  
High Concentration ◽  
Dimer Formation ◽  
Protein Molecules ◽  
D Dimer

Abstract: D-dimer is a product of the enzymatic degradation of the fibrinogen-fibrin molecule, and its existence is demonstrable in circulation. The test based limits may be considered as normal values. It was first thought to be a product of coagulation, then a product of lysis. High-concentration D-dimer in blood detected in thromboembolic diseases is considered to be of diagnostic value. In cases where thromboembolism was ruled out despite elevated titres but heparin (LMWH) or CLOPIDOGREL was given as a cautionary measure, we found that D-dimer values remained elevated. This finding means that in vivo coagulation is not a precondition to D-dimer formation. Analysis of such cases uncovers liver or kidney disease in the background, but old age may also be a factor. Often elevated ferritin levels were observed ‘in parallel’ with elevated D-dimer values. These findings lead us to presume an enzymatic degradation process of ‘elderly’ protein molecules, which is universally applicable. Orv Hetil. 2017; 158(50): 1971–1976.

Performance of a hybrid MF membrane system combining activated carbon adsorption and biological oxidation

2001 ◽  
Vol 1 (5-6) ◽  
pp. 253-259 ◽  
Author(s):  
T. Suzuki ◽  
Y. Watanabe ◽  
G. Ozawa
Keyword(s):  
Organic Matter ◽  
Activated Carbon ◽  
Membrane Permeability ◽  
Pilot Plant ◽  
Membrane System ◽  
Biological Oxidation ◽  
High Concentration ◽  
Activated Carbon Adsorption ◽  
Carbon Adsorption ◽  
Chemical Washing

The authors studied the performance of a hybrid MF membrane system combining activated carbon adsorption and biological oxidation for the removal of turbidity, natural organic matter, ammonia and manganese from river water in pilot-plant experiments. In this system, part of the soluble organic matter was adsorbed by the activated carbon. Ammonia and soluble manganese were oxidized by microorganisms that were concentrated in a submerged tank. In preliminary experiments, it became clear that powdered activated carbon (PAC) addition improved membrane permeability, because PAC has a large volume of macro-pores, which can adsorb larger molecular-weight organic matter. In the pilot-plant experiment, however, it was difficult to slow the rate of membrane permeability loss by PAC addition only. This may be due to biological fouling, caused by operating the system at a high recovery rate in order to maintain a high concentration of microorganisms in the submerged tank. Therefore, backwashing using hypochlorite solution (50-200 mg/l of Cl2) was carried out every few hours. This simple chemical washing was effective in preventing bio-fouling of the membrane.

scholarly journals Nature of virally mediated changes in membrane permeability to small molecules

1980 ◽  
Vol 186 (3) ◽  
pp. 847-860 ◽  
Author(s):  
C C Impraim ◽  
K A Foster ◽  
K J Micklem ◽  
C A Pasternak
Keyword(s):  
Amino Acids ◽  
Small Molecules ◽  
Membrane Permeability ◽  
Cell Biology ◽  
Sendai Virus ◽  
Cell Types ◽  
Cell Swelling ◽  
High Concentration ◽  
Permeability Changes ◽  
Rate Limiting

1. The changes in membrane permeability to small molecules caused by Sendai virus [Pasternak & Micklem (1973) J. Membr. Biol. 14, 293-303] have been further characterized. The uptake of substances that are concentrated within cells is inhibited. Choline and 2-deoxyglucose, which become phosphorylated, and aminoisobutyrate and glycine, which are driven by a Na+-linked mechanism, are examples. The uptake of each compound under conditons where its diffusion across the plasma membrane is rate-limiting is stimulated by virus. Choline, 2-deoxyglucose and amino acids at high concentration, amino acids in Na+-free medium, and most substances at low temperature, are examples. It is concluded that virally mediated decrease of uptake is due to one of two causes. Substances that are accumulated by phosphorylation are not retained because of leakage of the phosphorylated metabolites out of cells. Substances that are accumulated by linkage to a Na+ gradient are no longer accumulated because of collapse of the gradient resulting from an increased permeability to Nat 2. Increased permeability to K+ and Na+ results in (a) membrane depolarization and (b) cell swelling. The latter event leads to haemolysis (for erythrocytes) and can lead to giant-cell (polykaryon) formation (for several cell types). 3. Recovery of cells can be temporarily achieved by the addition of Ca2+; permanent recovery requires incubation for some hours at 37 degrees C. 4. The possible significance of virally mediated permeability changes, with regard to clinical situations and to cell biology, is discussed.

Nematode Antocoagulant Protein c2 (NAPc2) Interferes with Factor Xa Dimerization: Structural Alteration of Factor Xa Upon Dimerization.

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 1128-1128
Author(s):  
Rima Chattopadhyay ◽  
Tilen Koklic ◽  
Rinku Majumder ◽  
Barry R. Lentz
Keyword(s):  
Potent Inhibitor ◽  
Conflicts Of Interest ◽  
Substrate Binding ◽  
Factor Xa ◽  
Binding Region ◽  
High Concentration ◽  
Dimer Formation ◽  
Dimer Interface ◽  
Factor Va ◽  
Membrane Bound

Abstract Abstract 1128 Nematode Anticoagulant protein c2 (NAPc2) from the hematophagous hookworm, Ancyclostoma canimum, is a potent inhibitor of factor × activation to Xa by the Xase complex composed of VIIa and tissue factor. Factor Xa (FXa) plays a crucial role in blood coagulation; including formation of a prothrombin activating complex with its co-factor Va. NAPc2 also inhibits activation of prothrombin by this complex. FXa forms a functionally inactive dimer upon binding to either membrane bound or solution phosphatidylserine (PS) in the presence of calcium, and that the structure of FXa in the dimer is altered (Chattopadhyay et al, 2009; Koklic et al., 2009). The dimer interface predicted from mass spectroscopy involves a residue in the hirudin-binding site. NAPc2 interacts with two regions in FXa, one overlapping with the hirudin site and another in the substrate binding exosite (Murakami et al., 2007; Yegneswaran et al., 2003; Wilkens et al., 2002). We show that NAPc2 at low concentration does not interfere with dimerization, but at high concentration it destabilizes the dimer as documented with homoFRET studies with FEGRXa (Fluorescein-GLU-GLY-ARG-chloromethylketone-Xa). Proteolytic activity (prothrombin as substrate) suggested that the species Xa · NAPc2 (NAPc2 binding to FXa monomer) and FXa2 · NAPc2 (NAPc2 binding to FXa dimer) have activity comparable to FXa dimer. A model is suggested in which initial NAPc2 binding to the substrate-binding region in FXa alters interactions in the hirudin-binding region and thus alters dimer formation. Supported by USPHS grant HL072827 to BRL. Disclosures: No relevant conflicts of interest to declare.

scholarly journals A high concentration of DMSO activates caspase-1 by increasing the cell membrane permeability of potassium

2017 ◽  
Vol 70 (1) ◽  
pp. 313-320 ◽  
Author(s):  
Yang Xiang ◽  
Ming-ming Zhao ◽  
Sujiao Sun ◽  
Xiao-Long Guo ◽  
Qiquan Wang ◽  
...  
Keyword(s):  
Cell Membrane ◽  
Membrane Permeability ◽  
Cell Membrane Permeability ◽  
High Concentration ◽  
Caspase 1

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.

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