Ultrathin monolayer lipid membranes from a new family of crown ether-based bola-amphiphiles

Abstract

1705 timum values of the parameters of this equation to fit the conductance kinetic data, Le., the values of [HX],. and ti. Because of interdependencies, all five parameters k , , k2, k3, to, and [HX], could not be accurately determined simultaneously; therefore, calculations were done with fixed values assigned for either one or both of k2 and k3. The program can also be used to calculate first-order rate coefficients where the parameters are k3, to, and [HX], with k , and k2 set to 0.It was determined from calculations on synthetic data generated with probable values of k l , k2, k3, to, and [HX], that, when k3 is small but kinetically significant, setting k2 to its true value and k3 to 0 will result in a small systematic wave in the plot of the resistance residuals. Error plots with such systematic trends were observed for 2b in 80E and 90E, see Figure 4 in the supplementary material. The fit of the data from 2b in 95E as described above produced a wave in the opposite sense which was shown to be due to the presence of a fraction of 1% pemsyl chloride impurity. These data were analyzed using a Simplex algorithm, which had been developed previously in our l a b o r a t~r y .~~ It was applied in this case to fit conductance data from the solvolysis of a mixture of two components: the ester 2b reacting according to the kinetic scheme described above and the chloride reacting by a simple first-order process. The number of variables derived from the least-squares treatment was reduced to four by fixing k2 and the solvolysis rate constant for pemsyl chloride at the independently observed values and constraining k3 by fixingf,,, at 0.968, the value found to give optimum fits to all kinetic runs. Available: Figures 3,4, and 5, showing the trends in the errors in the calculated resistances ("resistance residuals") over the time span of the solvolysis of 2a and 3b in 90E and 2b in 80E using the simple first-order rate law and the rate law given in the Appendix for Scheme I (4 pages). Ordering information is given on any current masthead page. Supplementary MaterialAbstract: Twelve novel a$-bis(N-azacrown ether) compounds have been prepared, characterized, and converted into a previously unknown type of niosome. Four are bis( 15-crown-5) derivatives having the following spacer chains: (CH2)12 (l), (CH2)16 (2), CO(CH2)20C0 (3), and (CH2)22 (4). The eight bis(aza-18-crown-6) derivatives have the following spacers: (CH2)lo H2)11S(CH2)12S(CH2)11C0 (12). Aggregation studies of 1 and 7, employing transmission electron microscopy as well as dynamic and static light scattering, demonstrate that these compounds form a novel class of spherical monolayer lipid membrane vesicles when dispersed in water. Debye light-scattering profiles obtained from a suspension of large (=200 nm diameter) vesicles indicate a relative refractive index near 1. Dynamic turbidimetry in acidic media on a suspension of bola-amphisomes formed from 1, suggested that the contribution of micelle-vesicle equilibria to the bolyte aggregation state is negligible...

Coordination and transport of alkali metal cations through phospholipid bilayer membranes by hydraphile channels

“…Azacrown-based lariat ethers [49,19] proved versatile and flexible. In separate studies, it was found that crown ethers function well as amphiphilic headgroups [50,51]. Crown ethers are, of course, cation selective and it was thought that some selectivity would be imposed on the system if cations used the crown as an entry portal.…”

Synthesis and aggregation behaviour of symmetric glycosylated bolaamphiphiles in water

“…Munoz et al 14 and Brisset et al 15 reported a significant impact of the length of the hydrophobic linkage on the aggregation properties of bolaamphiphiles with crown ether or sugar heads. These authors suggested a bending of chains consisting of 12 methylene groups or more.…”

“…21 Such results are in very good agreement with the hypothesis that the hydrophobic segment folds up when bolaform surfactants bear a long hydrocarbon spacer arm. 14,15 However, it is noteworthy that the rigidity of the linker in compounds B2 and B4, afforded by a biphenyl or fluorocarbon chain, did not prevent micelle formation and thus, probably, the folding up of the spacer group.…”

Microfluidic Fabrication of Vesicles

“…Examples of these include liposomes [1], polymersomes [2,3] and niosomes [4,5]. Other vesicle-like structures include colloidosomes, whose membranes are not necessarily made up of bilayers of amphiphiles [6,7].…”