X-ray structure study of thermotropic phases in isoacylphosphatidylcholine multibilayers

Church, Sally; Griffiths, David; Lewis, Richard L.; McElhaney, Ronald N.; Wickman, H. H.

doi:10.1016/s0006-3495(86)83687-6

Cited by 39 publications

(12 citation statements)

References 18 publications

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“…27 The discrepancy is mainly the effect of reduced hydration resulting in a reduced area per lipid, A L . We measure A L ≈ 41 Å 2 to be in good agreement with previous reports for dehydrated gel phases, 42,43 28 Atoms from the DMPC molecules were distributed between five component groups representing distinct portions of the bilayer. These regions are (1) the terminal CH 3 groups at the end of the lipid chains, for both lipids in the bilayer, found in the center of the bilayer (CH 3 ); (2) the CH 2 groups composing the hydrocarbon core of the lipid molecule (CH 2 ); (3) the glycerol moiety in the headgroup (GC); and (4) the phosphate group in the headgroup (P).…”

Section: Preparation Of the Highly Oriented Multilamellarsupporting

confidence: 88%

Curcumin Protects Membranes through a Carpet or Insertion Model Depending on Hydration

2017

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Curcumin is the main ingredient in turmeric, a common Indian spice. Curcumin shows a broad spectrum of effects, including anti-Alzheimer's and antioxidant properties. An interaction between curcumin and lipid membranes has been speculated as the root cause of this activity, and the molecule is often proposed to protect the bilayer. However, the detailed molecular mechanism of this protection is disputed. There is evidence that curcumin either (a) lies flat on the bilayer and provides a "carpet" for protection by forming a steric barrier, or (b) inserts into the membrane and stiffens tails, thereby protecting against peptide insertion. We studied the interaction between curcumin and 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) bilayers at different concentrations using high-resolution X-ray diffraction and molecular dynamics (MD) computer simulations. We observed curcumin molecules forming a carpet in dehydrated bilayers, whereas in hydrated membranes the curcumin molecules were found to insert into the bilayers. From calculations of the potential of mean force (PMF), we find two minima, a metastable state in the headgroup region, at |z| ≈ 22 Å, and a global minimum in the hydrophobic membrane core, at |z| ≈ 9 Å. The population of the two states depends on membrane hydration. Experiments may thus observe curcumin in a carpet or inserted position, depending on the osmotic pressure conditions created, for instance, by salts, buffer solutions, substrates, or macromolecular solutes. In the carpet model, curcumin dehydrates lipid bilayers and decreases fluidity. When inserted, curcumin leads to a further fluidification of the membranes and an increase in tail fluctuations, contrary to cholesterol's condensing effect.

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Section: Preparation Of the Highly Oriented Multilamellarsupporting

confidence: 88%

Curcumin Protects Membranes through a Carpet or Insertion Model Depending on Hydration

2017

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“…hibit a distinct odd/even structural dimorphism (see Table 2 for a summary of the structural features of the meta-stable quasicrystalline phases). Odd/even structural dimorphism has also been observed in studies of PCs with branched and c-cyclohexyl fatty acyl chains (Lewis and McElhaney, 1985a,b;Lewis et al, 1987bLewis et al, , 1989Mantsch et al, 1985Mantsch et al, , 1987Mantsch et al, , 1989Church et al, 1986) and appears to be a general property of long-chain paraffinic compounds whose acyl chains are tilted (Malkin, 1952;Broadhurst, 1962). We therefore suggest that in the meta-stable quasicrystalline phases of these PGs, the hydrocarbon chains of at least one of the two groups of homologs (i.e., the odd-numbered, even-numbered, or both) must be tilted to the bilayer normal.…”

Section: Discussionmentioning

confidence: 77%

Calorimetric and Spectroscopic Studies of the Thermotropic Phase Behavior of the n-Saturated 1,2-Diacylphosphatidylglycerols

Yuanpeng¹,

Lewis²,

McElhaney³

1997

Biophysical Journal

166

123

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The polymorphic phase behavior of a homologous series of n-saturated 1,2-diacyl phosphatidylglycerols (PGs) was studied by differential scanning calorimetry and Fourier transform infrared and 31P-nuclear magnetic resonance spectroscopy. When dispersed in aqueous media under physiologically relevant conditions, these compounds exhibit two thermotropic phase transitions that are structurally equivalent to the well-characterized pretransitons and gel/liquid-crystalline phase transitions exhibited by bilayers of the corresponding 1,2-diacyl phosphatidylcholines. Furthermore, when incubated at low temperatures, their gel phases spontaneously transform into one or more solid-like phases that appear to be highly ordered, quasicrystalline bilayers that are probably partially dehydrated. The quasicrystalline structures, which form upon short-term, low-temperature annealing of these lipids, are meta-stable with respect to more stable structures, to which they eventually transform upon prolonged low-temperature incubation. The rates of formation of the quasicrystalline phases of the PGs generally tend to decrease as hydrocarbon chain length increases, and PGs whose hydrocarbon chains contain an odd number of carbon atoms tend to be slower than those of neighboring even-numbered homologs. The calorimetric data also indicate that the quasicrystalline phases of these compounds become progressively less stable relative to both their gel and liquid-crystalline phases as the length of the hydrocarbon chain increases and that they decompose either to the liquid-crystalline phase (short- and medium-chain compounds) or to the normal gel phase (long-chain compounds) upon heating. The spectroscopic data indicate that although there is odd-even alternation in the structures of the quasicrystalline phases formed upon short-term low-temperature incubation of these compounds, the structural features of the stable quasicrystalline phases eventually formed are all similar. Furthermore, the degree of hydration and the nature of hydrogen bonding interactions in the headgroup and interfacial regions of these PG bilayers differ significantly from that observed in all other phospholipid bilayers studied so far. We suggest that many of the properties of PG bilayers can be rationalized by postulating that the glycerol moiety of the polar headgroup is directly involved in shielding the negative charges at the surface of the bilayer by means of hydration-like hydrogen bonding interactions with the phosphate moiety.

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“…This is in marked contrast to many of the PCs that have been studied so far. With the PCs it is often the case that the gel-phase polymorphism exhibited by the homologues with odd-numbered fatty acyl chains is structurally and phenomenologically different from that exhibited by the homologues with even-numbered chains (27,29,63,(67)(68)(69). Interestingly, with the n-saturated diacyl PCs, there was no indication for any structural odd-even alternation in the types of Lc phases formed, but the structure of the various stable Lc phases varied markedly with acyl chain length (47,48).…”

Section: Discussionmentioning

confidence: 99%

Calorimetric and spectroscopic studies of the polymorphic phase behavior of a homologous series of n-saturated 1,2-diacyl phosphatidylethanolamines

Lewis

McElhaney

1993

Biophysical Journal

Self Cite

149

134

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The polymorphic phase behavior of a homologous series of n-saturated 1,2-diacyl phosphatidylethanolamines was investigated by differential scanning calorimetry, 31P-nuclear magnetic resonance, and Fourier transform infrared spectroscopy. Upon heating, aqueous dispersions of dried samples of the short- and medium-chain homologues (n < or = 17) exhibit single, highly energetic transitions from a dry, crystalline form to the fully hydrated, liquid-crystalline bilayer at temperatures higher than the lamellar gel-liquid-crystalline phase transition exhibited by fully hydrated samples. In contrast, the longer chain homologues (n > or = 18) first exhibit a transition from a dehydrated solid form to the hydrated L beta gel phase followed by the gel-liquid-crystalline phase transition normally observed with fully hydrated samples. The fully hydrated, aqueous dispersions of these lipids all exhibit reversible, fairly energetic gel-liquid-crystalline transitions at temperatures that are significantly higher than those of the corresponding phosphatidylcholines. In addition, at still higher temperatures, the longer chain members of this series (n > or = 16) exhibit weakly energetic transitions from the lamellar phase to an inverted nonlamellar phase. Upon appropriate incubation at low temperatures, aqueous dispersions of the shorter chain members of this homologous series (n < or = 16) form a highly ordered crystal-like phase that, upon heating, converts directly to the liquid-crystalline phase at the same temperature as do the aqueous dispersions of the dried lipid. The spectroscopic data indicate that unlike the n-saturated diacyl phosphatidylcholines, the stable crystal-like phases of this series of phosphatidylethanolamines describe an isostructural series in which the hydrocarbon chains are packed in an orthorhombic subcell and the headgroup and polar/apolar interfacial regions of the bilayer are effectively immobilized and substantially dehydrated. Our results suggest that many of the differences between the properties of these phosphatidylethanolamine bilayers and their phosphatidylcholine counterparts can be rationalized on the basis of stronger intermolecular interactions in the headgroup and interfacial regions of the phosphatidylethanolamine bilayers. These are probably the result of differences in the hydration and hydrogen bonding interactions involving the phosphorylethanolamine headgroup and moieties in the polar/apolar interfacial regions of phosphatidylethanolamine bilayers.

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X-ray structure study of thermotropic phases in isoacylphosphatidylcholine multibilayers

Cited by 39 publications

References 18 publications

Curcumin Protects Membranes through a Carpet or Insertion Model Depending on Hydration

Curcumin Protects Membranes through a Carpet or Insertion Model Depending on Hydration

Calorimetric and Spectroscopic Studies of the Thermotropic Phase Behavior of the n-Saturated 1,2-Diacylphosphatidylglycerols

Calorimetric and spectroscopic studies of the polymorphic phase behavior of a homologous series of n-saturated 1,2-diacyl phosphatidylethanolamines

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