35 research outputs found
Structural insight into self assembly of sophorolipids: a molecular dynamics simulation study
Sophorolipids contain hydrophilic head groups at the ends of a long hydrophobic tail. As a result, sophorolipids can self assemble into variety of structures in water. Atomistic self assembly simulations of sophorolipids are performed in water. Two sophorolipids, oleic acid sophorolipid and linolenic acid sophorolipid, differing in number of double bonds in the hydrophobic tail are considered for this study. Long time self assembly simulations are performed considering 1:3 lipid to water ratio by weight for both oleic and linolenic acid sophorolipids. In addition to 1:3 ratio, long time self assembly simulations are also performed with 1:1 and 1:2 ratios for linolenic acid sophorolipids. Distinctions in structural arrangements of sophorolipid molecules in the self assembled configuration for all the systems are investigated. The present study aims to provide structural insight into the different self assembled configurations of sophorolipids in water
Access to harmonine, a chemical weapon of ladybird beetles
The synthesis of harmonine, a defense alkaloid from the harlequin ladybird is reported by three different routes. The preparation of several new analogs with the same molecular weight and the decoration of gold nanoparticles with harmonines are also part of the present communication
Vesicle structures from bolaamphiphilic biosurfactants: experimental and molecular dynamics simulation studies on the effect of unsaturation on sophorolipid self-assemblies
The formation of giant-vesicle-like structures by self-assembling linolenic acid sophorolipid (LNSL) molecules is revealed. Sophorolipids belong to the class of bolaamphiphilic glycolipid biosurfactants. Interestingly, the number of double bonds present in the hydrophobic core of sophorolipids is seen to have a great influence on the type of self-assembled structures formed. Dye encapsulation results establish the presence of an aqueous compartment inside the LNSL vesicles. Molecular dynamics simulation (MD) studies suggest the existence of two possible conformations of LNSLs inside the self-assembled structures and that LNSL molecules arrange in layered structures
Synthesis of Uniform, Monodisperse, Sophorolipid Twisted Ribbons
International audienceControl over size monodispersity in chiral self-assembled systems is important for potential applications like templating, tissue engineering or enantioselective chromatography, just to cite a few examples. In this context, it was reported that the saturated form of sophorolipids (SL), a bioderived glycolipid, are able to form self-assembled twisted ribbons in water at neutral pH. Here, we show the possibility to control their size dispersion, generally between 10 and 40nm after synthesis to a value of 13.5 +/- 1.5nm, by a simple dialysis step eliminating the excess of NaCl. We use transmission electron microscopy under cryogenic conditions (cryo-TEM) combined with small angle neutron scattering (SANS) to characterize the ribbon dispersion both visually and statistically. Two negative controls show the importance of salt in the aggregation process of the ribbons
pH- and Time-Resolved <i>in Situ</i> SAXS Study of Self-Assembled Twisted Ribbons Formed by Elaidic Acid Sophorolipids
Conditions
that favor the helical structure formation in structurally
similar sophorolipids (SLs), that is, elaidic acid SLs (having a <i>trans</i> double bond between the C9 and C10 positions of the
alkyl chain) and stearic acid SLs (no double bond), are presented
here. The helical self-assembled structures formed by elaidic acid
SLs were independent of pH and also were mediated by a micellar intermediate.
On the other hand, the stearic acid SLs formed helical structures
under low pH condition only. Astonishingly, the formation routes were
found to be different, albeit the molecular geometry of both SLs is
similar. Even if a conclusive mechanistic understanding must await
further work, our studies strongly point out that the noncovalent
weak interactions in elaidic acid SLs are able to overcome the electrostatic
repulsions of the sophorolipid carboxylate groups at basic pH and
facilitating the formation of helical structures. On the other hand,
the hydrophobic interactions in stearic acid SLs endow the helical
structures with extra stability, making them less vulnerable to dissolution
upon heating
Micelles versus ribbons : how congeners drive the self-assembly of acidic sophorolipid biosurfactants
Sophorolipids (SLs), a class of microbially derived biosurfactants, are reported by different research groups to have different self-assembled structures (either micelles or giant ribbons) under the same conditions. Here we explore the reasons behind these contradictory results and attribute these differences to the role of specific congeners that are present in minute quantities. We show that a sample composed of a majority of oleic acid (C18:1) sophorolipid in the presence of only 0.5% (or more) of congeners with stearic acid (C18:0) or linoleic acid (C18:2) results in the formation of micelles that are stable over long periods of time. Conversely, the presence of only 10 to 15% of congeners with a stearic acid chain gives fibrillar structures instead of micelles. To study the mechanisms responsible, oleic acid SLs devoid of any other congeners were prepared. Very interestingly, this sample can self-assemble into either micelles or fibers depending on minute modifications to the self-assembly conditions. The findings are supported by light scattering, small-angle X-ray scattering, transmission electron microscopy under cryogenic conditions, high-pressure liquid chromatography, and NMR spectroscopy
Audible sound-controlled spatiotemporal patterns in out-of-equilibrium systems
© 2020, The Author(s), under exclusive licence to Springer Nature Limited. Naturally occurring spatiotemporal patterns typically have a predictable pattern design and are reproducible over several cycles. However, the patterns obtained from artificially designed out-of-equilibrium chemical oscillating networks (such as the Belousov–Zhabotinsky reaction for example) are unpredictable and difficult to control spatiotemporally, albeit reproducible over subsequent cycles. Here, we show that it is possible to generate reproducible spatiotemporal patterns in out-of-equilibrium chemical reactions and self-assembling systems in water in the presence of sound waves, which act as a guiding physical stimulus. Audible sound-induced liquid vibrations control the dissolution of atmospheric gases (such as O2 and CO2) in water to generate spatiotemporal chemical patterns in the bulk of the fluid, segregating the solution into spatiotemporal domains having different redox properties or pH values. It further helps us in the organization of transiently formed supramolecular aggregates in a predictable spatiotemporal manner. [Figure not available: see fulltext.11sciescopu