Structures of uranyl-decorated lecithin and lecithin–cholesterol bilayers

K, Furuya; Yamaguchi, Tetsuji; Inoko, Yōji; Mitsui, T.

doi:10.1107/s0567740876006444

Cited by 11 publications

(5 citation statements)

References 9 publications

(13 reference statements)

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“…Uranyl acetate has been shown to interact with membrane lipids (Furuya et al, 1976, Stamatoff et al, 1979Parsegian et al, 1981;Huang et al, 1983), and its effect on the phase properties of egg PA was examined. It proved to be quite effective in inducing gel phase formation (Figure 2D4) presumably reflecting tight binding of the uranyl (U022+) ion to the phosphate head group of egg PA.…”

Section: Resultsmentioning

confidence: 99%

Influence of metal ions on the phase properties of phosphatidic acid in combination with natural and synthetic phosphatidylcholines: an x-ray diffraction study using synchrotron radiation

Caffrey¹,

Feigenson²

1984

Biochemistry

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Synchrotron radiation was used as an X-ray source of extreme brilliance to investigate by X-ray diffraction the phase behavior of fully hydrated unoriented samples of egg phosphatidic acid (egg PA) in combination with egg phosphatidylcholine (egg PC), dimyristoylphosphatidylcholine (DMPC), or dipalmitoylphosphatidylcholine (DPPC). The diffraction method was sensitive to greater than or equal to 2 mol % gel and greater than or equal to 30 mol % liquid-crystal phase lipid. Accordingly, the liquidus boundary was determined more exactly than the solidus boundary in these phase diagrams. A more precise location of the solidus line was obtained by monitoring the electron paramagnetic resonance signal from TEMPO partitioned between fluid lipid and aqueous phases. Phase diagrams for (i) egg PA/egg PC, (ii) egg PA/DMPC, and (iii) egg PA/DPPC with and without Cd2+ were determined in the temperature range 0-55 degrees C. In system i, the addition of Cd2+ raises the midpoint of the egg PA transition temperature range from 14 to 26 degrees C and results in a wide region of gel-liquid-crystal phase coexistence. With as little as 5 mol % egg PA in egg PC, Cd2+ induces phase separation up to about 25 degrees C. The phase behavior of egg PA/spin-labeled PC in the presence of Cd2+ was very similar to that of egg PA/egg PC in the 10-35 degrees C temperature range. In systems ii and iii Cd2+ extends the temperature range over which the gel and liquid-crystal phases coexist.(ABSTRACT TRUNCATED AT 250 WORDS)

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Section: Resultsmentioning

confidence: 99%

Influence of metal ions on the phase properties of phosphatidic acid in combination with natural and synthetic phosphatidylcholines: an x-ray diffraction study using synchrotron radiation

Caffrey¹,

Feigenson²

1984

Biochemistry

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“…In a second approach, we interpreted the intensities of lamellar reflection using a strip model. Strip models have been used to analyze the structure of lipid bilayers (Worthington, 1969;Furuya et al, 1976;Wiener et al, 1989). The strip model represents the electron density of bilayer structures as a sequence of constant electron density.…”

Section: Appendixmentioning

confidence: 99%

Characterization of complexes formed in fully hydrated dispersions of dipalmitoyl derivatives of phosphatidylcholine and diacylglycerol

Quinn¹,

Takahashi²,

Hatta³

1995

Biophysical Journal

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The phase diagram of fully hydrated binary mixtures of dipalmitoylphosphatidylcholine (DPPC) with 1,2-dipalmitoylglycerol (DPG) published recently by López-García et al. identifies regions where stoichiometric complexes of 1:1 and 1:2 DPPC:DPG, respectively, are formed. In this study, the structural parameters of the 1:1 complex in the presence of pure DPPC was characterized by synchrotron low angle and static x-ray diffraction methods. Structural changes upon transitions through phase boundaries were correlated with enthalpy changes observed by differential scanning calorimetry in mixtures of DPPC with 5, 7.5, 10, and 20 mol% DPG dispersed in excess water. Phase separation of a complex in gel phase could be detected by calorimetry in the mixture containing 5 mol% DPG but was not detectable by synchrotron low angle x-ray diffraction. Static x-ray measurements show evidence of phase separation, particularly in the reflections indexing chain packing. In the mixture containing 7.5 mol% DPG, two distinct lamellar repeat spacings could be seen in the temperature range from 25 to 34 degrees C. The lamellar spacing of about 6.6 nm was assigned to pure gel phase DPPC because the change in the spacing corresponds with thermal transition of the pure phospholipid, and a longer repeat spacing of about 7.2 nm was assigned to domains of the 1:1 complex of DPPC-DPG. In the temperature range from 34 to 420C, i.e., in the region of coexistence of the ripple phase of DPPC and the gel phase of the complex, a single, rather broad lamellar reflection appears because of superposition of two reflections of DPPC and the complex; the lamellar spacing of DPPC in the ripple phase is similar to that of the gel phase of complex. In the coexistence region of the liquid-crystalline phase of DPPC and the gel phase of complex (-42-480C), the lamellar reflections of the both phases are present. The fluidus boundary lies between the coexistence region and the fluid region.In the fluid region (-48-550C), the gel state of complex persists up to the fluidus boundary, whereupon the liquid-crystalline state of complex replaces the gel state of the complex. This indicates that the complex is also immiscible with DPPC even above the fluidus boundary at least in the temperature range close to the phase boundary. For mixtures comprising 10 and 20 mol%DPG in DPPC, complex formation is clearly detectable in both the gel region and the coexistence region by x-ray diffraction.Synchrotron x-ray measurements indicate phase separation between pure DPPC and liquid-crystalline complex just above thefluidus boundary. Static, wide angle x-ray measurements also suggest phase separations of the 1:1 complex not only from the gel phase but also the liquid-crystalline phase of pure DPPC. Two distinct diffraction peaks were detected for the mixture of DPPC with 5, 10, and 20 mol% DPG. One is due to the chain spacing of the complex, and the other is due to that of the pure DPPC. In the coexistence region of the liquid-crystalline phase of DPPC and the gel phase of complex, ...

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“…In gel phase bilayers the binding of U022+ leads to a decrease of the molecular area to -44 A2 (Furuya et al, 1976) with a concomitant decrease in hydrocarbon chain tilt (Parsegian et al, 1981). In monolayers (see Fig.…”

Section: Discussionmentioning

confidence: 94%

Nuclear magnetic resonance and calorimetric study of the structure, dynamics, and phase behavior of uranyl ion/dipalmitoylphosphatidylcholine complexes

Huang¹,

Blume²,

Gupta³

et al. 1988

Biophysical Journal

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The interaction of UO2(2+) with dipalmitoylphosphatidylcholine (DPPC) has been studied as a function of temperature and composition using nuclear magnetic resonance (NMR) spectroscopy, differential scanning calorimetry (DSC), and monolayer studies. Computer simulations of the 31P-NMR powder spectra of DPPC dispersions in the presence of various concentrations of UO2(2+) are consistent with the binding stoichiometry of [UO2(2+)]/[DPPC] = 1:4 at [UO2(2+)]/[DPPC] less than 0.3. This complex undergoes a phase transition to the liquid crystalline phase at T'm = 50 +/- 3 degrees C with a breadth delta T'm = 7 +/- 3 degrees C. This broad transition gradually disappears at higher UO2(2+) concentrations, suggesting the presence of yet another UO2(2+)/DPPC complex (or complexes) whose NMR spectra are indistinguishable from those of the 1:4 UO2(2+)/DPPC species. The temperature-dependent 13C powder spectra of 2(1-13C) DPPC dispersions in the presence of 1.2 mol ratio of UO2(2+) show that this higher order complex (complexes) also undergoes a phase transition to the liquid crystalline state at T'm +/- = 58 +/- 3 degrees C with a breadth delta T"m = 15 +/- 5 degrees C. The NMR spectra indicate that exchange among these various UO2(2+)/DPPC complexes is slow. In addition, computer simulations of the 31P-, 13C-, and 2H-NMR powder spectra show that axial diffusion of the DPPC molecules about their long axes is quenched by addition of UO2(2+) and acyl chain isomerization is the dominant motional mode. The isomerization is best described as two-site hopping of the greater than C-D bond at a rate of approximately 10(6) s-1, a motional mode which is expected for a kink diffusion.

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Structures of uranyl-decorated lecithin and lecithin–cholesterol bilayers

Cited by 11 publications

References 9 publications

Influence of metal ions on the phase properties of phosphatidic acid in combination with natural and synthetic phosphatidylcholines: an x-ray diffraction study using synchrotron radiation

Influence of metal ions on the phase properties of phosphatidic acid in combination with natural and synthetic phosphatidylcholines: an x-ray diffraction study using synchrotron radiation

Characterization of complexes formed in fully hydrated dispersions of dipalmitoyl derivatives of phosphatidylcholine and diacylglycerol

Nuclear magnetic resonance and calorimetric study of the structure, dynamics, and phase behavior of uranyl ion/dipalmitoylphosphatidylcholine complexes

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