Characterization of the hydrophobic interaction of steroids with endoplasmic reticulum membranes by quenching of 6,8(14)-bisdehydro-17α-hydroxyprogesterone fluorescence

Kühn‐Velten, W. Nikolaus; Kempfle, M.

doi:10.1016/0005-2736(93)90287-a

Cited by 9 publications

(3 citation statements)

References 27 publications

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Section: Resultsmentioning

confidence: 91%

“…Statistically, a population of UDCA molecules could be accommodated between the DPPC acyl chains through nonspecific hydrophobic interaction, as observed for steroids intercalated within endoplasmic reticulum membranes. 46 Whether UDCA interacts either peripherally or intrinsically with the DPPC bilayers, the packing arrangements of the DPPC hydrocarbon chains would be perturbed, which, in turn, would alter the order-disorder transitions of mixed component bilayer dispersions. Additionally, defects probably arising at the boundaries between microdomains formed within UDCA:DPPC bilayers could provide loci for increased UDCA adsorption and/ or penetration into the bilayer.…”

Section: Methodsmentioning

confidence: 99%

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Thermodynamic Study of the Effects of Ursodeoxycholic Acid and Ursodeoxycholate on Aqueous Dipalmitoyl Phosphatidylcholine Bilayer Dispersions

and

Levin

1997

J. Phys. Chem. B

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The effects of ursodeoxycholic acid (UDCAH) and ursodeoxycholate (UDCA-) on the thermotropic phase behavior of aqueous bilayer dispersions of 1,2-dipalmitoyl-3-sn-phosphatidylcholine (DPPC), buffered at pH 7.0, were examined by differential scanning calorimetry (DSC) for concentrations of UDCAH and UDCA- (represented by UDCA) from 0 to approximately 76 mol %. The calorimetric data show that progressively increasing UDCA concentrations decreases the DPPC bilayer main transition temperatures (T m), while increasing the widths of the gel to liquid crystalline phase transition endotherms. The DPPC bilayer pretransition is suppressed in the presence of UDCA at the lowest concentrations employed. The calorimetric data, which are interpreted in terms of the partition equilibria of UDCAH and UDCA- and of the DPPC bilayer phase transition enthalpies and Gibbs free energies, allow the development of a thermodynamic approach for determining the phase boundaries in mixed DPPC:UDCA dispersions. In particular, for concentrations of UDCA up to approximately 25 mol %, the gel to liquid crystalline phase transition enthalpies of the mixed DPPC:UDCA bilayers remain essentially constant. The increase that occurs in the DPPC gel to liquid crystalline phase transition enthalpies for UDCA concentrations between approximately 25−60 mol % is interpreted in terms of an induced interdigitated gel (LgI) phase stabilized by specific DPPC:UDCA molecular interactions. The data suggest that the interdigitated gel phase exists in equilibrium with micelles, whose structures remain to be elucidated, of various UDCA:DPPC mole ratios. Finally, concentrations of UDCA in amounts greater than 60 mol % result in constant DPPC phase transition temperatures and enthalpies.

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Section: Resultsmentioning

confidence: 91%

Section: Methodsmentioning

confidence: 99%

Thermodynamic Study of the Effects of Ursodeoxycholic Acid and Ursodeoxycholate on Aqueous Dipalmitoyl Phosphatidylcholine Bilayer Dispersions

and

Levin

1997

J. Phys. Chem. B

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“…For these reasons, passive exogenous insertion of chemically defined structures into cellular membranes is an attractive alternative approach to cell surface engineering . The approach entails conjugating the epitope of interest to a suitable hydrophobic anchor, such as a fatty acid, , steroid, lipophilic peptide, – or pyrene moiety, and incubating the synthetic construct with cultured cells. Glycolipids, glycosylphosphatidylinositol (GPI)-anchored proteins and their analogues, , and lipid-based imaging dyes have all been displayed on cell membranes in this fashion.…”

Section: Introductionmentioning

confidence: 99%

Noncovalent Cell Surface Engineering: Incorporation of Bioactive Synthetic Glycopolymers into Cellular Membranes

et al. 2008

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The controlled addition of structurally defined components to live cell membranes can facilitate the molecular level analysis of cell surface phenomena. Here we demonstrate that cell surfaces can be engineered to display synthetic bioactive polymers at defined densities by exogenous membrane insertion. The polymers were designed to mimic native cell-surface mucin glycoproteins, which are defined by their dense glycosylation patterns and rod-like structures. End-functionalization with a hydrophobic anchor permitted incorporation into the membranes of live cultured cells. We probed the dynamic behavior of cell-bound glycopolymers bearing various hydrophobic anchors and glycan structures using fluorescence correlation spectroscopy (FCS). Their diffusion properties mirrored those of many natural membrane-associated biomolecules. Furthermore, the membrane-bound glycopolymers were internalized into early endosomes similarly to endogenous membrane components and were capable of specific interactions with protein receptors. This system provides a platform to study cell-surface phenomena with a degree of chemical control that cannot be achieved using conventional biological tools.

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Dendrophanes: Water‐soluble dendritic receptors as models for buried recognition sites in globular proteins

Mattei¹,

Wallimann²,

Kenda³

et al. 1997

Helvetica Chimica Acta

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Water-soluble dendritic cyclophanes (dendrophanes) of first (1, 4), second (2, 5), and third generation (3, 6) with poly(ether amide) branching and 12, 36, and 108 terminal carboxylate groups, respectively, were prepared by divergent synthesis, and their molecular recognition properties in aqueous solutions were investigated. Dendrophanes 1-3 incorporate as the initiator core a tetraoxa[6.1.6.l]paracyclophane 7 with a suitably sized cavity for inclusion compiexation of benzene or naphthalene derivatives. The initiator core in 4-6 is the [6.1.6.l]cyclophane 8 shaped by two naphthyl(pheny1)methane units with a cavity suitable for steroid incorporation. The syntheses of 1-6 involved sequential peptide coupling to monomer 9, followed by ester hydrolysis (Schemes 1 and 4).Purification by gel-permeation chromatography (GPC; Fig. 3) and full spectral characterization were accomplished at the stage of the intermediate poly(methy1 carboxylates) 10-12 and 23-25, respectively. The third-generation 108-ester 25 was also independently prepared by a semi-convergent synthetic strategy, starting from 4 (Scheme 5). All dendrophanes with terminal ester groups were obtained in pure form according to the I3C-NMR spectral criterion (Figs. 1 and 5). The MALDI-TOF mass spectra of the third-generation derivative 25 (mol. wt. 19328 D) displayed the molecular ion as base peak, accompanied by a series of ions [M -n(1041 7)]+, tentatively assigned as characteristic fragment ions of the poly(ether amide) cascade. A similar fragmentation pattern was also observed in the spectra of other higher-generation poly(ether amide) dendrimers. Attempts to prepare monodisperse fourth-generation dendrophanes by divergent synthesis failed. 'H-NMR and fluorescence binding titrations in basic aqueous buffer solutions showed that dendrophanes 1-3 complexed benzene and naphthalene derivatives, whereas 4-6 bound the steroid testosterone. Complexation occurred exclusively at the cavity-binding site of the central cyclophane core rather than in fluctuating voids in the dendritic branches, and the association strength was similar to that of the complexes formed by the initiator cores 7 and 8, respectively (Tables f and 3). Fluorescence titrations with 6-(p-tolnidino)naphthalene-2-sulfonate as fluorescent probe in aqueous buffer showed that the micropolarity at the cyclophane core in dendrophanes 1-3 becomes increasingly reduced with increasing size and density of the dendritic superstructure; the polarity at the core of the third-generation compound 3 is similar to that of EtOH (Table 2). Host-guest exchange kinetics were remarkably fast and, except for receptor 3, the stabilities of all dendrophane complexes could be evaluated by 'H-NMR titrations. The rapid complexation-decomplexation kinetics are explained by the specific attachment of the dendritic wedges to large, nanometer-sized cyclophane initiator cores, which generates apertures in the surrounding dendritic superstructure.

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Characterization of the hydrophobic interaction of steroids with endoplasmic reticulum membranes by quenching of 6,8(14)-bisdehydro-17α-hydroxyprogesterone fluorescence

Cited by 9 publications

References 27 publications

Thermodynamic Study of the Effects of Ursodeoxycholic Acid and Ursodeoxycholate on Aqueous Dipalmitoyl Phosphatidylcholine Bilayer Dispersions

Thermodynamic Study of the Effects of Ursodeoxycholic Acid and Ursodeoxycholate on Aqueous Dipalmitoyl Phosphatidylcholine Bilayer Dispersions

Noncovalent Cell Surface Engineering: Incorporation of Bioactive Synthetic Glycopolymers into Cellular Membranes

Dendrophanes: Water‐soluble dendritic receptors as models for buried recognition sites in globular proteins

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