Change in Micelle Form Induced by Cosurfactant Addition in Nematic Lyotropic Phases

Amáral, L. Q.; Filho, Ourides Santin; Taddei, and G.; Vila-Romeu, Nuria

doi:10.1021/la9700073

Cited by 24 publications

(34 citation statements)

References 38 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…On the other hand, the aggregate may have molecules of more than one species, and the case of mixed aggregates has been less studied. The case of micelles made up of amphiphile and decanol, which may form nematic lyotropic liquid crystals, has been studied within the context of the elastic bending energy, expressed as a function of the surfactant parameters of the amphiphile and of decanol . A change in the micelle form, from spherocylinders to square tablets, is predicted with the addition of decanol because decanol prefers less curved polar/apolar interfaces.…”

Section: Discussionmentioning

confidence: 99%

“…The theory arrives to different equations for the shape transformation depending on the amphiphile and decanol behaving independently or forming a complex of N amphiphiles per decanol molecule. Such complexes can be seen as a different entity, with its own surfactant parameter . An analogy with the case of bilayers made up of different species is proposed here to discuss the relationships between the surfactant parameter and the SAXS model used here.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Pore Model in the Melting Regime of a Lyotropic Biomembrane with an Anionic Phospholipid

Spinozzi

Amáral

2016

Langmuir

View full text Add to dashboard Cite

Aqueous dispersions of the anionic phospholipid dimyristoyl phosphatidyl glycerol (DMPG) exhibit an unusual "melting regime", at the phase transition between the ordered (gel) and the disordered (fluid liquid crystal) state of hydrocarbon chains, depending on the ionic strength and DMPG concentration, previously attributed to the pore formation. Dispersions with 150 mM DMPG present a lamellar phase above 23 °C, within the melting regime. In this study, we present a detailed pore model for the analysis of small-angle X-ray scattering (SAXS) results and their variation with temperature, focused on the surface fractions of pores in the bilayers. Large and small toroidal pores are necessary to explain the SAXS results. Pores have DMPG in the fluid conformation, whereas the flat region of the bilayer has DMPG molecules in fluid and in gel conformations. A particular strategy was developed to estimate the charges due to the localization of mobile ions in the system, which is based on the calculation of electron densities by duly considering all molecular and ionic species that characterize the system, and the temperature dependency of their volumes. The best fit to the model of SAXS curves defines that the gel phase transforms initially, at 19.4 °C, in uncoupled bilayers with large pores (radius 93.2 ± 0.5 Å, with water channel diameter 137 ± 1 Å), which transform into small pores along the lamellar phase. The minimum intensity of the SAXS bilayer peak at 30 °C corresponds to a maximum number of small pores, and above 35 °C, the system enters into the normal lamellar fluid phase, without pores. The charge is estimated and shows that the regions with pores contains less Na ions per polar head; hence, when they are forming, there is a release of Na ions toward the bulk.

show abstract

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Pore Model in the Melting Regime of a Lyotropic Biomembrane with an Anionic Phospholipid

Spinozzi

Amáral

2016

Langmuir

View full text Add to dashboard Cite

show abstract

“…In the case of the binary SLS / water system only spherocylinder and prolate ellipsoids provide possible models with only slightly differencies in dimensions and polydispersity. This information can be very useful for further investigations of changes in shape and dimensions of micelles, particularly as predicted to occur in mixed micelles (Amaral et al, 1997) and other systems of biochemical interest.…”

Section: Figurementioning

confidence: 99%

SAS from inhomogeneous particles with more than one domain of scattering density and arbitrary shape

Spinozzi¹,

Carsughi²,

Mariani³

et al. 2000

J Appl Crystallogr

Self Cite

View full text Add to dashboard Cite

The Small Angle Scattering from inhomogeneous particles is very important in the investigation of biological systems, where the scattering objects might be formed by many domains. For these systems, the scattering intensity, as well as its Fourier transform, are written as a sum of different contributions. In this work, for the simple case of two domains, the form factors of different scattering particle shapes, such as the oblate, prolate and biaxial ellipsoids, spherocylinder and disks were calculated by using a Monte Carlo method. Finally, SAS data of sodium lauryl sulfate micelles in water were analysed by using a model that accounts for polydispersity and micelles of different shape.

show abstract

“…A first attempt to model the symmetry transition, in collaboration with a theoretical Italian chemist continuing a work on the I–H α transition [ 45 ], was an adaptation of the bending elastic theory of bilayers in vesicles to the micellar case, in terms of the surfactant parameter (already mentioned in item 4.3). The nematic cylindrical (Nc)-nematic discotic (Nd) phase transitions are correlated with a change of micellar form from spherocylinder (SC) to square tablet (ST) [ 53 ], which occurs geometrically in a continuous way, with an intermediate biaxial object. Good agreement was obtained for three amphiphile/decanol/water systems, where the transition occurs as a function of the decanol/amphiphile molecular ratio.…”

Section: Self-assembly and Lyotropic Liquid Crystalsmentioning

confidence: 99%

Supramolecular Aggregates: Hardness Plus Softness

Amáral

2021

Molecules

View full text Add to dashboard Cite

The properties of supramolecular aggregates cross several disciplines, embracing the sciences of nature and joining theory, experiment, and application. There are few articles centering on the problems of interdisciplinarity, and this paper gives an alternative approach, starting with scientific divulgation, bringing concepts from their origin, to facilitate the access of young scientists to the scientific content. Didactic examples are taken from the experience of the author in changing directions of research due to several circumstances of life (including maternity), starting from the view of a rigorous student of physics and evolving to several subjects in chemistry. The scientific part starts with concepts related to nuclear interactions, using the technique of neutron scattering in reactors, and evolves to research in molecular physics. Finally, it arrives at the academic context, with research in condensed matter physics, with X-ray and other techniques, starting with detergents forming nematic lyotropic liquid crystals and the phase transition sequence of isotropic to nematics to hexagonal. The scientific subjects evolved to biological and bio-inspired liquid crystals, including DNA and also specific lipids and phospholipids in biomimetic membranes. Special attention is given to the question of distribution of matter in these complex systems and the non-trivial connections between biochemistry, structures, auto-aggregation, and biology.

show abstract

Change in Micelle Form Induced by Cosurfactant Addition in Nematic Lyotropic Phases

Cited by 24 publications

References 38 publications

Pore Model in the Melting Regime of a Lyotropic Biomembrane with an Anionic Phospholipid

Pore Model in the Melting Regime of a Lyotropic Biomembrane with an Anionic Phospholipid

SAS from inhomogeneous particles with more than one domain of scattering density and arbitrary shape

Supramolecular Aggregates: Hardness Plus Softness

Contact Info

Product

Resources

About