Thermodynamic and structural study of DMPC-alkanol systems.

The thermodynamic and structural behaviors of lamellar dimyristoylphosphatidylcholine-alkanol (abbreviation DMPC-CnOH, n = 8-18 is the even number of carbons in the alkyl chain) systems were studied by using DSC and SAXD/WAXD methods at a 0-0.8 CnOH : DMPC molar ratio range. Up to n≤ 10 a significant biphasic effect depending on the main transition temperature t on the CnOH concentration was observed.

Phase behavior of the DOPE + DOPC + alkanol system.

Small- and wide-angle X-ray diffraction was used to study the effect of 1-alkanols, as simple models of general anesthetics, (abbreviation CnOH, n = 8-18 is the even number of carbons in the aliphatic chain) on the lamellar to hexagonal Lα→ H(II) phase transition in the dioleoylphosphatidylethanolamine-dioleoylphosphatidylcholine = 3 : 1 mol/mol (DOPE + DOPC) system. All studied CnOHs were found to decrease the phase transition temperature of the DOPE + DOPC system in a CnOH chain length and concentration dependent manner and thus promote the formation of the HII phase. Anesthetically active C8OH and C10OH were found to decrease the lattice parameter d of the Lα phase, however longer non-anesthetic CnOHs increased the parameter d; this effect being more pronounced with increasing CnOH concentration.

Effects of N,N-dimethyl-N-alkylamine-N-oxides on DOPC bilayers in unilamellar vesicles: small-angle neutron scattering study.

Small-angle neutron scattering data were collected from aqueous dispersions of unilamellar vesicles (ULVs) consisting of mixtures of 1,2-dioleoyl-sn-glycero-3-phosphatidylcholine and a homologous series of N,N-dimethyl-N-alkylamine-N-oxides (CnNO, n = 12, 14, 16, and 18, where n is the number of carbon atoms in the alkyl chain). A modeling approach was applied to the neutron scattering curves to obtain the bilayer structural parameters. Particularly, the external (2)H2O/H2O contrast variation technique was carried out on pure dioleoylphosphatidylcholine (DOPC) ULVs to determine the hydrophilic region thickness [Formula: see text] = 9.

Molecular and component volumes of N,N-dimethyl-N-alkylamine N-oxides in DOPC bilayers.

The volumetric properties of fluid bilayers formed of dioleoylphosphatidylcholine (DOPC) with incorporated N,N-dimethyl-N-alkylamine N-oxides (CnNO, n=6, 10-18 is the even number of carbons in alkyl chain) were studied by vibrating tube densitometry in the temperature interval from 20°C to 50°C. It was found that the DOPC and CnNO mixed ideally in the investigated composition range and hence the molecular volumes of DOPC (VDOPC) and incorporated CnNO (VCnNO) were constant and additive within error limits. From the temperature dependencies of the molecular volumes of DOPC and CnNO their coefficients of isobaric thermal expansivities in the investigated temperature interval were obtained.

Study of interaction of long-chain n-alcohols with fluid DOPC bilayers by a lateral pressure sensitive fluorescence probe.

The excimer 1,2-dipyrenedecanoyl-sn-glycero-3-phosphatidylcholine (dipy10PC) fluorescence probe was used to determine effects of aliphatic alcohols (CnH2n+1OH, n = 12-18 is the even number of carbons in alkyl chain) on fluid dioleoylphosphatidylcholine (DOPC) +dioleoylphosphatidylserine (DOPS) bilayers in multilamellar vesicles at molar ratio DOPC/DOPS = 24.7. The excimer to monomer fluorescence intensity ratio increases with the increase of CnH2n+1OH/DOPC molar ratio and decreases with the CnH2n+1OH alkyl chain length n at a constant CnH2n+1OH/DOPC = 0.

Influence of cholesterol and β-sitosterol on the structure of EYPC bilayers.

The influence of cholesterol and β-sitosterol on egg yolk phosphatidylcholine (EYPC) bilayers is compared. Different interactions of these sterols with EYPC bilayers were observed using X-ray diffraction. Cholesterol was miscible with EYPC in the studied concentration range (0-50 mol%), but crystallization of β-sitosterol in EYPC bilayers was observed at X ≥ 41 mol% as detected by X-ray diffraction.

DNA condensation and its thermal stability influenced by phospholipid bilayer and divalent cations.

We studied the effect of divalent alkaline earth metal cations Ca²⁺, Mg²⁺ and transition metals Co²⁺, Ni²⁺, Cu²⁺ and Zn²⁺ on DNA condensation and its protection against thermal denaturation in presence of dioleoylphosphatidylcholine liposomes (DOPC). Experimental results have shown that Ca²⁺ and Mg²⁺ as well as Zn²⁺ mediate DNA condensation. Cu²⁺ causes DNA double helix destabilization, and does not mediate binding between DNA and DOPC liposomes.

Interaction of long-chain n-alcohols with fluid DOPC bilayers: a neutron diffraction study.

Lamellar phases composed of fluid dioleoylphosphatidylcholine (DOPC) bilayers containing alkan-1-ols (CnOH, n = 8, 10, 14, 16, 18 is the number of carbon atoms) at CnOH : DOPC = 0.3 molar ratio and hydrated with heavy water at 20.2 ≥ D2O : DOPC ≥ 14.

The effects of cholesterol and β-sitosterol on the structure of saturated diacylphosphatidylcholine bilayers.

The structures of DMPC and DPPC bilayers in unilamellar liposomes, in the presence of 33.3 mol% cholesterol or the plant sterol β-sitosterol, have been studied by small-angle neutron scattering. The bilayer thickness d(L) increases in a similar way for both sterols.

Molecular and component volumes of saturated n-alkanols in DOPC+DOPS bilayers.

The volumetric properties of fluid bilayers consisting of dioleoylphosphatidylcholine (DOPC, 96wt%) and dioleoylphosphatidylserine (DOPS, 4wt%) with incorporated saturated n-alkanols (CnOH, n=10-16 is the even number of carbons in alkyl chain) were studied by vibrating tube densitometry. The mixing of DOPC and DOPS was found to be ideal and the molecular volumes of pure lipids V(DOPC) and V(DOPS) are additive in mixed bilayers. The increase of V(DOPS) with temperature was steeper than that of V(DOPC) as quantified by significantly higher coefficient of isobaric thermal expansivity gamma.

Areas of monounsaturated diacylphosphatidylcholines.

We have studied the structural properties of monounsaturated diacylphosphatidylcholine lipid bilayers (i.e., diCn:1PC, where n = 14, 16, 18, 20, 22, and 24 is the number of acyl chain carbons).

Structural changes in dipalmitoylphosphatidylcholine bilayer promoted by Ca2+ ions: a small-angle neutron scattering study.

Small-angle neutron scattering (SANS) curves of unilamellar dipalmitoylphosphatidylcholine (DPPC) vesicles in 1-60mM CaCl2 were analyzed using a strip-function model of the phospholipid bilayer. The fraction of Ca2+ ions bound in the DPPC polar head group region was determined using Langmuir adsorption isotherm. In the gel phase, at 20 degrees C, the lipid bilayer thickness, dL, goes through a maximum as a function of CaCl2 concentration (dL=54.

Component volumes of unsaturated phosphatidylcholines in fluid bilayers: a densitometric study.

The specific volumes of six 1,2-diacylphosphatidylcholines with monounsaturated acyl chains (diCn:1PC, n=14-24 is the even number of acyl chain carbons) in fluid bilayers in multilamellar vesicles dispersed in H(2)O were determined by the vibrating tube densitometry as a function of temperature. From the data obtained with diCn:1PC (n=14-22) vesicles in combination with the densitometric data from Tristram-Nagle et al. [Tristram-Nagle, S.

Synchrotron SAX and WAX diffraction study of a hydrated very long-chain, dendritic amphiphile + DPPC mixture.

The tri-headed anionic dendritic amphiphile, 4-(2-carboxyethyl)-4-[(icosyloxycarbonyl)amino]heptanedioic acid (3CCb20), forms mixed aggregates with dipalmitoylphosphatidylcholine (DPPC) in excess water at 3CCb20:DPPC = 0.91:1 molar ratio. On heating, these mixed aggregates transform into fluid bilayers stacked in the liquid crystalline lamellar L(alpha) phase at about 40 degrees C.

The structural diversity of DNA-neutral phospholipids-divalent metal cations aggregates: a small-angle synchrotron X-ray diffraction study.

We investigate the structure of aggregates formed due to DNA interaction with saturated neutral phosphatidylcholines [dipalmitoylphosphatidylcholine (DPPC) and dimyristoylphosphatidylcholine] in presence of Ca(2+) and Mg(2+) cations using simultaneous synchrotron small- and wide-angle X-ray diffractions. For DPPC:DNA = 3:1 mol/base and in the range of 1-50 mM Ca(2+), the diffractograms show structural heterogeneity of aggregates. We observe the coexistence of two lamellar phases in aggregates prepared at 1 mM Ca(2+): L(x) phase with the DNA strands (of unknown organization) intercalated in water layers between adjacent lipid bilayers and L(DPPC) phase of DPPC bilayers without any divalent cations and DNA strands.

The structure of DNA-DOPC aggregates formed in presence of calcium and magnesium ions: a small-angle synchrotron X-ray diffraction study.

The structure of aggregates formed due to DNA interaction with dioleoylphosphatidylcholine (DOPC) vesicles in presence of Ca(2+) and Mg(2+) cations was investigated using synchrotron small-angle X-ray diffraction. For DOPC/DNA=1:1 mol/base and in the range of concentration of the cation(2+) 0-76.5 mM, the diffractograms show the coexistence of two lamellar phases: L(x) phase with repeat distance d(Lx) approximately 8.

Interaction of gemini surfactants butane-1,4-diyl-bis(alkyldimethylammonium bromide) with DNA.

The size and structure of aggregates formed by interaction of DNA with homologous series of cationic gemini surfactants butane-1,4-diyl-bis(alkyldimethylammonium bromide) (CnGS, n=10-16 is the number of alkyl carbons) were investigated using UV-vis turbidity, dynamic light scattering and small-angle synchrotron X-ray (SAX) diffraction. The detailed analysis of turbidity in the range of lambda=450-600 nm indicates an anomaly in the growth of CnGS+DNA aggregates with increasing concentration of CnGS, possibly involving changes of structure and size of aggregates. Using dynamic light scattering, changes of the effective diameter of CnGS+DNA (n=12 and 16) aggregates formed in the CnGS concentration range 0.

The structure of DNA-DLPC-cationic gemini surfactant aggregates: a small angle synchrotron X-ray diffraction study.

The structure of aggregates formed by interaction of DNA with unilamellar dilauroylphosphatidylcholine (DLPC) vesicles (DNA:DLPC=1:1 base/mol) in the presence of gemini surfactant butane-1,4-diyl-bis(dodecyldimethylammonium bromide) (C12GS) was investigated using synchrotron small angle X-ray diffraction. In the concentration range C12GS+:DLPC< or =1 mol/mol, a condensed lamellar Lalphac phase was found with a repeat period of lipid bilayer stacking in the range d approximately 5.70-6.

Bilayer thickness in unilamellar extruded 1,2-dimyristoleoyl and 1,2-dierucoyl phosphatidylcholine vesicles: SANS contrast variation study of cholesterol effect.

Small-angle neutron scattering on extruded unilamellar vesicles in water was used to study bilayer thickness when cholesterol (CHOL) was added at 44.4 mol% to 1,2-dimyristoleoylphosphatidylcholine (diC14:1PC) and 1,2-dierucoylphosphatidylcholine (diC22:1PC) bilayers. Using the (1)H(2)O/(2)H(2)O contrast variation and the small-angle form of Kratky-Porod approximation, the bilayer gyration radii at infinite contrast R(g,infinity) and the bilayer thickness parameters d(g,infinity) = 12(0.

Effects of gemini surfactants on egg phosphatidylcholine bilayers in the fluid lamellar phase.

The influence of 1,4-butanediamonium-N,N'-dialkyl-N,N,N',N'-tetramethyl dibromides (CmA, m = 7-16 is the number of alkyl carbons) on the egg yolk phosphatidylcholine (EYPC) bilayer thickness and lipid surface area at the bilayer-aqueous phase interface is studied using X-ray diffraction on fluid lamellar CmA + EYPC + H2O phases as a function of CmA:EYPC and H2O:EYPC molar ratios and the alkyl chain length m. At the constant CmA:EYPC = 0.4 and H2O:EYPC = 18 molar ratios, the CmA induced bilayer thickness decrease shows a minimum and the lipid surface area increase a maximum at the alkyl chain length m = 9.

Models to analyze small-angle neutron scattering from unilamellar lipid vesicles.

Small-angle scattering has been employed to study the structure of lipid bilayers in unilamellar vesicles. This paper evaluates the use of a model approach for the analysis of such data. A long molecular dynamics simulation of a dipalmitoylphosphatidylcholine bilayer in the L(alpha) phase provides detailed structural information from which scattering length density profiles and scattering intensity are obtained.

Influence of local anesthetics on the phosphatidylcholine model membrane: small-angle synchrotron X-ray diffraction and neutron scattering study.

The phase preferences of egg yolk phosphatidylcholine (EYPC) have been examined in the presence of tertiary amine anesthetics [2-(propyloxy)phenyl]-2-(1-piperidinyl)ethyl ester of carbamic acid (C3A) and [2-(heptyloxy)phenyl]-2-(1-piperidinyl)ethyl ester of carbamic acid (C7A, heptacaine). Using the synchrotron small-angle X-ray diffraction (SAXD), it is shown that the C3A anesthetic induces the cubic and hexagonal (H(I)) phases at 2 > or = C3A:EYPC > 0.5 and H2O:EYPC < or = 40 molar ratios.

Effects of non-ionic surfactants N-alkyl-N,N-dimethylamine-N-oxides on the structure of a phospholipid bilayer: small-angle X-ray diffraction study.

Effects of non-ionic surfactants N-alkyl-N,N-dimethylamine-N-oxides (C(n)NO, n is the number of alkyl carbons) on the structure of egg yolk phosphatidylcholine (EYPC) bilayers in the lamellar fluid phase was studied by small-angle X-ray diffraction as a function of H(2)O:EYPC and C(n)NO:EYPC molar ratios. The bilayer thickness d(L) and the lipid surface area at the bilayer-aqueous interface S(L) were calculated from the repeat period, d of the lamellar phase, based on the model that water and EYPC + CnNO molecules form separated layers and that their molecular volumes are additive. In the studied range of m=CnNO:EYPC molar ratios up to 1:1, d(L) and S(L) change linearly.

Determination of bilayer thickness and lipid surface area in unilamellar dimyristoylphosphatidylcholine vesicles from small-angle neutron scattering curves: a comparison of evaluation methods.

Small-angle neutron scattering (SANS) experiments were performed on unilamellar 1,2-dimyristoylphosphatidylcholine (DMPC) vesicles prepared in heavy water by extrusion through polycarbonate filters with 500 A pores. The data obtained at 30+/-0.1 degrees C were evaluated using a five-strip function model of the bilayer coherent neutron scattering length density, three different approximate form factors describing scattering from vesicles, and different methods of evaluation of the experimental data.

Small-angle neutron scattering study of the lipid bilayer thickness in unilamellar dioleoylphosphatidylcholine vesicles prepared by the cholate dilution method: n-decane effect.

Previous X-ray diffraction studies on fully hydrated fluid lamellar egg phosphatidylcholine phases indicated a approximately 10 A increase of bilayer thickness in the presence of excess n-decane [Biochim. Biophys. Acta 597 (1980) 455], while the small-angle neutron scattering (SANS) on unilamellar extruded dioleoylphosphatidylcholine (DOPC) vesicles detected substantially smaller 2.