Determination of critical micelle concentration of bile acid salts by micro-calorimetric titration

Simonović, Branislav; Momirović, Mirjana

doi:10.1007/bf01243172

Cited by 62 publications

(32 citation statements)

References 21 publications

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“…ABCG2 has been documented to be located in cholesterol rich microdomains, the so-called rafts, and its direct interaction with caveolin-1, a marker of lipid rafts, has also been demonstrated (Storch et al, 2007). In accordance with this finding, high membrane cholesterol levels were found to significantly improve the function of ABCG2.…”

Section: Introductionsupporting

confidence: 77%

“…We and others found that the enrichment of insect membranes with cholesterol greatly increases the ATPase and transport function of ABCG2 (Pal et al, 2007;Telbisz et al, 2007). A dramatic but reversible inhibition of ABCG2 function in mammalian cells upon depletion of cholesterol has also been shown (Storch et al, 2007;Telbisz et al, 2007). It is not known whether cholesterol is only a modulator of ABCG2 function or it is directly transported by the protein.…”

Section: Introductionmentioning

confidence: 99%

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Regulation of the Function of the Human ABCG2 Multidrug Transporter by Cholesterol and Bile Acids: Effects of Mutations in Potential Substrate and Steroid Binding Sites

et al. 2014

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ABCG2 (ATP-binding cassette, subfamily G, member 2) is a plasma membrane glycoprotein that actively extrudes xenobiotics and endobiotics from the cells and causes multidrug resistance in cancer. In the liver, ABCG2 is expressed in the canalicular membrane of hepatocytes and excretes its substrates into the bile. ABCG2 is known to require high membrane cholesterol content for maximal activity, and by examining purified ABCG2 reconstituted in proteoliposomes we have recently shown that cholesterol is an essential activator, while bile acids significantly modify the activity of this protein. In the present work, by using isolated insect cell membrane preparations expressing human ABCG2 and its mutant variants, we have analyzed whether certain regions in this protein are involved in sterol recognition. We found that replacing ABCG2-R482 with large amino acids does not affect cholesterol dependence, but changes to small amino acids cause altered cholesterol sensitivity. When leucines in the potential steroid-binding element (SBE, aa 555-558) of ABCG2 were replaced by alanines, cholesterol dependence of ABCG2 activity was strongly reduced, although the L558A mutant variant when purified and reconstituted still required cholesterol for full activity. Regarding the effect of bile acids in isolated membranes, we found that these compounds decreased ABCG2-ATPase in the absence of drug substrates, which did not significantly affect substrate-stimulated ATPase activity. These ABCG2 mutant variants also altered bile acid sensitivity, although cholic acid and glycocholate were not transported by the protein. We suggest that the aforementioned two regions in ABCG2 are important for sterol sensing and may represent potential targets for pharmacologic modulation of ABCG2 function.

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Section: Introductionsupporting

confidence: 77%

Section: Introductionmentioning

confidence: 99%

Regulation of the Function of the Human ABCG2 Multidrug Transporter by Cholesterol and Bile Acids: Effects of Mutations in Potential Substrate and Steroid Binding Sites

et al. 2014

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“…Bile salts, however, due to the more or less "planar" hydrophobic and planar hydrophilic structure of the molecules (see Figure 1C), form much smaller micelles than the classical head-tail-detergents [20,23,28]. For sodium cholate (NaC) and sodium deoxycholate (NaDC) the aggregation number at room temperature is between 4 -6 molecules for NaC and higher for NaDC, with 7 -12 molecules (these micelles are denoted as primary micelles) [29,30]. This property is not surprising, because the peculiar molecular structure of bile salts ( Figure 1) does not really allow the formation of larger aggregate structures in order to isolate the hydrophobic part of the molecule from the aqueous phase.…”

Section: Compartment Concentrationmentioning

confidence: 99%

Membranolytic Activity of Bile Salts: Influence of Biological Membrane Properties and Composition

et al. 2007

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Abstract:The two main steps of the membranolytic activity of detergents: 1) the partitioning of detergent molecules in the membrane and 2) the solubilisation of the membrane are systematically investigated. The interactions of two bile salt molecules, sodium cholate (NaC) and sodium deoxycholate (NaDC) with biological phospholipid model membranes are considered. The membranolytic activity is analysed as a function of the hydrophobicity of the bile salt, ionic strength, temperature, membrane phase properties, membrane surface charge and composition of the acyl chains of the lipids. The results are derived from calorimetric measurements (ITC, isothermal titration calorimetry). A thermodynamic model is described, taking into consideration electrostatic interactions, which is used for the calculation of the partition coefficient as well as to derive the complete thermodynamic parameters describing the interaction of detergents with biological membranes (change in enthalpy, change in free energy, change in entropy etc). The solubilisation properties are described in a so-called vesicle-to-micelle phase transition diagram. The obtained results are supplemented and confirmed by data obtained from other biophysical techniques (DSC differential scanning calorimetry, DLS dynamic light scattering, SANS small angle neutron scattering).

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“…For this work, an I:S ratio of 3:1 was used with the intent to limit overloading and subsequent inhibition typically associated with FOG digestion. As 4:1 was the highest ratio investigated by Li et al [31], I:S ratios greater than 4:1 may further optimise FOG digestion, increasing SMP and/or reducing inhibition.…”

Section: Pw Harris Et Al Journal Of Environmental Chemical Engineementioning

confidence: 99%

“…Surfactant compounds within bile, sodium deoxycholate, sodium chenodeoxycholate and sodium cholate, have CMCs of 5.3, 7.0 and 18.4 mM respectively [31]. Of the bile doses trialled, 5 g/L and 6 g/L have potential bile salt concentrations above 5.3 mM, with 5.6 and 6.7 mM respectively.…”

Section: Comparison Of Bile Pre-treatment At Low (02-1 G/l) and Highmentioning

confidence: 99%

Bovine bile as a bio-surfactant pre-treatment option for anaerobic digestion of high-fat cattle slaughterhouse waste

Harris

Schmidt

McCabe

2018

Journal of Environmental Chemical Engineering

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A B S T R A C TBovine bile was assessed as a novel bio-surfactant pre-treatment to enhance anaerobic digestion of lipid-rich dissolved air flotation (DAF) sludge using biochemical methane potential (BMP) tests. Bile was dosed at arbitrary concentrations from 0.2-6 g/L. At 0.6 g bile/L, methane yield increased by 7.08%. Doses above 2 g bile/L produced negative impacts on SMP, kinetics and digestion profile. At 6 g/L bile produced a 6% decrease in specific methane production and up to 79% additional inhibitory duration, delayed time of peak methane production by up to 74%, and slowed total digestion time by up to 65%. Reaction kinetics declined linearly with respect to bile addition, reaching half the control value at 6 g/L bile concentration. Subsequent anaerobic toxicity assays between 1 and 6 g bile/L revealed that bile has an inhibitory effect under BMP testing at these higher doses. The economic viability of using bile as a bio-surfactant was assessed. In comparison to the current use of bile as a sale product to pharmaceutical companies, the addition of 0.2 g bile/L to existing slaughterhouse waste streams could increase the value of bile to 220% of its current sale value. The promising results of bile dosed at 0.6 g/L under BMP testing warrant further investigation into long-term impact of bile pre-treatments of high-fat slaughterhouse wastewater in semi-continuous digestion experiments.

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Determination of critical micelle concentration of bile acid salts by micro-calorimetric titration

Cited by 62 publications

References 21 publications

Regulation of the Function of the Human ABCG2 Multidrug Transporter by Cholesterol and Bile Acids: Effects of Mutations in Potential Substrate and Steroid Binding Sites

Regulation of the Function of the Human ABCG2 Multidrug Transporter by Cholesterol and Bile Acids: Effects of Mutations in Potential Substrate and Steroid Binding Sites

Membranolytic Activity of Bile Salts: Influence of Biological Membrane Properties and Composition

Bovine bile as a bio-surfactant pre-treatment option for anaerobic digestion of high-fat cattle slaughterhouse waste

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