scholarly journals Structural studies of the lamellar to bicontinuous gyroid cubic (QGII) phase transitions under limited hydration conditions

Soft Matter ◽  
2015 ◽  
Vol 11 (10) ◽  
pp. 1991-1997 ◽  
Author(s):  
T.-Y. Dora Tang ◽  
Nicholas J. Brooks ◽  
Oscar Ces ◽  
John M. Seddon ◽  
Richard H. Templer
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Elastic Energy ◽  
Cubic Phase ◽  
Structural Studies ◽  
Present Evidence ◽  
Bicontinuous Cubic

We present evidence for a non-diffracting structural intermediate during the lamellar to inverse bicontinuous cubic phase transition and show that elastic energy drives the cubic phase to equilibrium.

scholarly journals Phase Transition in Di-oleoylphosphatidylglycerol/Monoolein Membranes due to Interactions of Positively Charged Peptides at their Lipid Membrane-Interface

1970 ◽  
Vol 45 (3) ◽  
pp. 219-224
Author(s):  
Shah Md Masum ◽  
Masahito Yamazaki
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Small Angle ◽  
Lipid Membrane ◽  
Cubic Phase ◽  
Membrane Interface ◽  
X Ray ◽  
X Ray Scattering ◽  
Charged Peptides ◽  
Positively Charged

To elucidate the factors that induce phase transitions in biomembranes due to interactions of proteins/peptides at the lipid membrane-interface, the effects of positively charged peptides on the cubic phase (Q229) of Dioleoylphosphatidylglycerol (DOPG)/Monoolein (MO) membranes were investigated. Small angle X-ray Scattering (SAXS) results revealed that 12 mol% DOPG/88 mol % MO membranes in excess water at 25°C is body centered cubic phase of crystallographic space group Im3m (Q229). In presence of peptide LLKKK, the lattices constant of Q229 phase was gradually decreased with an increase of peptide concentration and a phase transition from cubic (Q229) to cubic (Q224) phase occurred at R=0.080; (R= molar ratio of peptide to lipid). On the other hand the designed peptide WLFLLKKK and antimicrobial peptide Magainin-2 induced lamellar phase (Lα) in the same mixture membranes. These results indicate that the interactions of the these peptides with this mixture membrane are different: LLKKK induces electrostatic attractive interactions and that of WLFLLKKKK and Magainin-2 bound with the lipid membranes induce electrostatic repulsive interaction at the membrane-interface, might be the major factor inducing different phase transitions in 12 mol% DOPG/88mol% MO mixture membranes. Key words: Antimicrobial peptide Magain-2; Dioleoylphosphatidylglycerol; Monoolein; Cubic phases; Small angle X-ray Scattering DOI: 10.3329/bjsir.v45i3.6530Bangladesh J. Sci. Ind. Res. 45(3), 219-224, 2010

Kinetics and Mechanism of the Lamellar to Gyroid Inverse Bicontinuous Cubic Phase Transition

Langmuir ◽  
2002 ◽  
Vol 18 (20) ◽  
pp. 7384-7392 ◽  
Author(s):  
Adam M. Squires ◽  
R. H. Templer ◽  
J. M. Seddon ◽  
J. Woenckhaus ◽  
R. Winter ◽  
...  
Keyword(s):  
Phase Transition ◽  
Kinetics And Mechanism ◽  
Cubic Phase ◽  
Bicontinuous Cubic

Salt Induced Lamellar to Bicontinuous Cubic Phase Transitions in Cationic Nanoparticles

2012 ◽  
Vol 116 (11) ◽  
pp. 3551-3556 ◽  
Author(s):  
Benjamin W. Muir ◽  
Guoliang Zhen ◽  
Pathiraja Gunatillake ◽  
Patrick G. Hartley
Keyword(s):  
Phase Transitions ◽  
Cubic Phase ◽  
Bicontinuous Cubic ◽  
Cationic Nanoparticles

Reconstructive phase transition in (NH4)3TiF7accompanied by the ordering of TiF6octahedra

2014 ◽  
Vol 70 (6) ◽  
pp. 924-931 ◽  
Author(s):  
Maxim Molokeev ◽  
S. V. Misjul ◽  
I. N. Flerov ◽  
N. M. Laptash
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
High Temperature ◽  
Room Temperature ◽  
Parent Phase ◽  
High Temperature Phase ◽  
Cubic Phase ◽  
Temperature Phase ◽  
Large Rotations ◽  
Fourfold Axis

An unusual phase transitionP4/mnc→ Pa\bar 3 has been detected after cooling the (NH4)3TiF7compound. Some TiF6octahedra, which are disordered in the room-temperature tetragonal structure, become ordered in the low-temperature cubic phase due to the disappearance of the fourfold axis. Other TiF6octahedra undergo large rotations resulting in huge displacements of the F atoms by 1.5–1.8 Å that implies a reconstructive phase transition. It was supposed that phasesP4/mbmand Pm\bar 3m could be a high-temperature phase and a parent phase, respectively, in (NH4)3TiF7. Therefore, the sequence of phase transitions can be written as Pm\bar 3m →P4/mbm→P4/mnc→ Pa\bar 3. The interrelation between (NH4)3TiF7, (NH4)3GeF7and (NH4)3PbF7is found, which allows us to suppose phase transitions in relative compounds.

scholarly journals Novel Insights into the Mechanistic Routes of Lyotropic Phase Transitions

2014 ◽  
Vol 70 (a1) ◽  
pp. C1187-C1187
Author(s):  
Oscar Ces ◽  
John Seddon ◽  
Robert Law ◽  
Nicholas Brooks ◽  
Richard Templer
Keyword(s):  
Phase Transitions ◽  
High Speed ◽  
Liquid Crystalline ◽  
Equilibrium Phase ◽  
Model Membrane ◽  
Phase Behaviour ◽  
Cubic Phase ◽  
Pressure Jump ◽  
Bicontinuous Cubic

When mixed with water, biological amphiphiles such as phospholipids can self-assemble to form a variety of lyotropic liquid crystalline structures including 1-D flat lamellar bilayers, 2-D hexagonal phases and 3-D bicontinuous cubic structures1. The role of the lamellar phase in nature is well understood – flat bilayers maintain the fundamental integrity of all living cells. However, non-lamellar phases also play a vital role in vivo. Extended cubic phases have been directly observed in cells and in addition, the repeating pores which form the continuously accessible structure of these bicontinuous phases are very closely structurally related to membrane pores formed during membrane fusion and fission. The equilibrium phase behaviour of pure phospholipids in water and simple model membrane mixtures has been widely studied but their out of equilibrium behaviour remains poorly understood. We have addressed this knowledge gap through pioneering work looking at the kinetics of phase transitions in phospholipid/water systems and phospholipid/protein/water mixtures using the pressure jump relaxation technique in conjunction with high speed, time resolved small angle X-ray diffraction. This presentation will provide an overview of how our bottom-up approach using model membrane systems has enabled us to establish the mechanistic routes and intermediates in a number of phase transition schemes including bicontinuous cubic to lamellar, hexagonal to lamellar and inter-cubic phase transitions.

scholarly journals Влияние дейтерирования на фазовые переходы в (NH-=SUB=-4-=/SUB=-)-=SUB=-3-=/SUB=-VOF-=SUB=-5-=/SUB=-

2022 ◽  
Vol 64 (3) ◽  
pp. 388
Author(s):  
Е.В. Богданов ◽  
В.С. Бондарев ◽  
М.В. Горев ◽  
М.С. Молокеев ◽  
И.Н. Флёров
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Monoclinic Phase ◽  
Unit Cell Volume ◽  
Temperature Stability ◽  
Ammonium Cation ◽  
Cubic Phase ◽  
Chemical Pressure ◽  
Phase Transition Temperatures ◽  
High Degree

The (ND4)3VOF5 crystal was grown with a high degree of deuteration (D ~ 92%). Structural and thermophysical studies have been carried out, the parameters of phase transitions have been determined. It was found that the deuteration of the ammonium cation in (NH4)3VOF5 led to a change in the chemical pressure, which was accompanied by an increase in the unit cell volume and an increase in the phase transition temperatures. The baric coefficients dTi / dp were determined and the phase T-p diagram (ND4)3VOF5 was constructed. A decrease in the temperature stability of the initial cubic phase Fm 3m in (ND4)3VOF5, as well as a wedging out of the intermediate monoclinic phase at a lower pressure as compared to (NH4)3VOF5, was found.

scholarly journals Initial Step of pH-Jump-Induced Lamellar to Bicontinuous Cubic Phase Transition in Dioleoylphosphatidylserine/Monoolein

Langmuir ◽  
2014 ◽  
Vol 30 (27) ◽  
pp. 8131-8140 ◽  
Author(s):  
Toshihiko Oka ◽  
Taka-aki Tsuboi ◽  
Takahiro Saiki ◽  
Tomoki Takahashi ◽  
Jahangir Md. Alam ◽  
...  
Keyword(s):  
Phase Transition ◽  
Initial Step ◽  
Cubic Phase ◽  
Ph Jump ◽  
Bicontinuous Cubic

scholarly journals Activation Energy of the Low-pH-Induced Lamellar to Bicontinuous Cubic Phase Transition in Dioleoylphosphatidylserine/Monoolein

Langmuir ◽  
2016 ◽  
Vol 32 (5) ◽  
pp. 1327-1337 ◽  
Author(s):  
Toshihiko Oka ◽  
Takahiro Saiki ◽  
Jahangir Md. Alam ◽  
Masahito Yamazaki
Keyword(s):  
Phase Transition ◽  
Activation Energy ◽  
Low Ph ◽  
Cubic Phase ◽  
Bicontinuous Cubic
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