Vesicular catalysis of the decarboxylation of 6‐nitrobenzisoxazole‐3‐carboxylate. The effects of sugars, long‐tailed sugars, cholesterol and alcohol additives

Abstract

Vesicular catalysis of the decarboxylation of 6-nitrobenzisoxazole-3-carboxylate. The effects of sugars, long-tailed sugars, cholesterol and alcohol additives Jongejan, Mahthild G. M.; Klijn, Jaap E.; Engberts, Jan. B. F. N.; Kiijn, J.E. Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. ABSTRACT: The effects of the addition of sugars, long-tailed n-alkyl pyranosides, n-alkyl glycerol ethers and nalcohols on the properties of di-n-hexadecyldimethylammonium bromide (DHAB) vesicles have been studied. Properties that were examined include the stability, morphology, phase of the tails, and catalytic rate acceleration of the unimolecular decarboxylation of the 6-nitrobenzisoxazole-3-carboxylate anion (6-NBIC). The kinetic data were analyzed on the basis of the pseudophase model and show a rate acceleration of a factor of about 1000 relative to the reaction in water. Upon addition of most additives an inhibiting effect on the decarboxylation reaction of 6-NBIC is observed relative to the reaction in vesicles without any additive. The largest inhibition was observed in the case of cholesterol. Contrastingly, n-dodecyl-b-maltoside (in the spherical vesicle region) and trehalose accelerate the reaction. The activation parameters show that the most significant contribution to the Gibbs energy of activation is the enthalpic factor, with a partly compensating entropic contribution.

Synthesis, self-assembly, and catalytic activity of histidine-based structured lipopeptides for hydrolysis reactions in water

“…11 Another type of catalysis can also be observed in aqueous medium: an interfacial catalysis can be brought thanks to the ability of selfassembled aggregates (mostly micelles, but also vesicles formed by amphiphiles) to increase reactions rates. [12][13][14][15][16][17][18][19] In this context, we have chosen to combine organocatalysis and interfacial catalysis by considering the use of selfassembled amphiphilic lipopeptides as catalysts in water (supramolecular enzyme mimics). 20 Thanks to the combination of various weak interactions (electrostatics, H-bonding, hydrophobic effect, etc.…”

Emergent properties arising from the assembly of amphiphiles. Artificial vesicle membranes as reaction promoters and regulators

“…154 Furthermore, it was shown that the presence of additives, either localized within the membranes of cationic amphiphiles (e.g. cholesterol) or on the membrane surface (trehalose) may have an influence of the rate of decarboxylation of 6-nitrobenzisoxazole-3-carboxylate, 155 the reaction being inhibited in presence of cholesterol and accelerated in presence of trehalose, if analyzed under the particular conditions used. 155 Experiments also indicate that the surface dynamics of the vesicle membranes is an important factor for efficiently catalyzing the reaction (possibly through an influence of the solvation of the substrate and reaction intermediates).…”

Encapsulation Processes by Bilayer Vesicles

“…91 Dehydration of the carboxylate group at the binding sites is most likely the main factor behind the catalysis. Different isokinetic temperatures (obtained from linear plots of enthalpies vs .…”