Benzylic and pyridinium head groups controlled surfactant-polymer aggregates of mixed cationic micelles and anionic polyelectrolytes

The anionic σ-complex from cyanide ion and 1,3,5-trinitrobenzene in water was stabilized by cationic micelles. The binding of counter ions to the micellar head groups in hexadecyl-trimethylammonium cyanidefollowed a distribution model with the counter ion binding constant KCN = 1400 mol-1 dm3. The bromide-cyanide ion exchange constant, KCNBr, was equal to 1.28. These results rendered further support to the general applicability of the distribution model.

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Reaction of hydroxide ion with 1,3,5-trinitrobenzene in cationic micelles: evidence of variable counterion binding to micellar head groups

Canadian Journal of Chemistry ◽

10.1139/v85-098 ◽

1985 ◽

Vol 63 (3) ◽

pp. 598-601 ◽

Cited By ~ 12

Author(s):

Leong-Huat Gan

Keyword(s):

Rate Constant ◽

Hexadecyltrimethylammonium Bromide ◽

Ion Distribution ◽

Counterion Binding ◽

Hydroxide Ion ◽

Micellar Systems ◽

Cationic Micelles ◽

Head Groups ◽

Distribution Constants ◽

The Stability

Cationic micelles of hexadecyltrimethylammonium bromide, chloride, and hydroxide (CTABr, CTACl, and CTAOH) greatly enhance the stability of anionic σ-complex formed by hydroxide ion and 1,3,5-trinitrobenzene (TNB). The counterion binding to the micellar head groups is assumed to vary but is governed by a distribution constant. Different distribution constants are used for different types of counterion. Using this treatment, the rate constant – surfactant concentration profiles for the reactions of TNB with hydroxide ion in CTAOH, CTABr, and CTACl can all be satisfactorily accounted for, yielding consistent results in various conditions. The ion distribution constants, KOH = 55 mol−1 dm3, KBr = 1800 mol−1 dm3, and KCl = 420 mol−1 dm3 and the rate constant KM = 3600 s−1 are obtained. In view of the success of this treatment, the assumption of a constant β value associated with the pseudophase model at best could only be viewed as an approximation, valid only for micellar systems with tightly bound counterions such as those in the micelles of CTABr.

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Microstructural morphology of sphingolipid dispersions as investigated by freeze-fracture EM

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100141093 ◽

1995 ◽

Vol 53 ◽

pp. 944-945

Author(s):

Vitthal S. Kulkarni ◽

Wayne H. Anderson ◽

Rhoderick E. Brown

Keyword(s):

Acyl Chain ◽

Biological Significance ◽

Freeze Fracture ◽

Fatty Acyl ◽

Fatty Acyl Moiety ◽

Aqueous Dispersions ◽

Head Groups ◽

Lipid Species ◽

Microstructural Morphology ◽

Layer Chromatography

The biological significance of the sphingomyelins (SM) and monoglycosylated sphingolipids like galactosylceramides (GalCer) are well documented Our recent investigation showed tubular bilayers in the aqueous dispersions of N-nervonoyl GalCer [N-(24:lΔ15,cls) GalCer] (a major fatty acyl moiety of natural GalCer). To determine the influence of lipid head groups on the resulting mesophasic morphology, we investigated microstructural self-assemblies of N-nervonoyl-SM [N-(24:1 Δ15,cls) SM; the second most abundant sphingomyelin in mammalian cell membranes], 1- palmitoyl-2-nervonoyl phosphatidylcholine [PNPC] (the lipid species with the same acyl chain configuration as in N-(24: 1) GalCer) and also compared it with egg-SM by freeze-fracture EM.Procedures for synthesizing and purifying N-(24:1) GalCer, N-(24:1) SM, and PNPC have been reported . Egg-SM was purchased from Avanti Polar Lipids, Alabaster AL. All lipids were >99% pure as checked by thin layer chromatography. Lipid dispersions were prepared by hydrating dry lipid with phosphate buffer (pH 6.6) at 80-90°C (3-5 min), vigorously vortexing (1 min) and repeating this procedure for three times prior to three freeze-thaw cycles.

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Influence of Brain Gangliosides on the Formation and Properties of Supported Lipid Bilayers for Binding Kinetics Studies

10.26434/chemrxiv.7505330 ◽

2018 ◽

Author(s):

Luke Jordan ◽

Nathan Wittenberg

Keyword(s):

Lipid Bilayers ◽

Binding Kinetics ◽

Supported Lipid Bilayers ◽

Dependent Manner ◽

Concentration Dependent Manner ◽

Supported Lipid Bilayer ◽

Head Groups ◽

Lipid Diffusion ◽

Kinetics Of ◽

Brain Gangliosides

This is a comprehensive study of the effects of the four major brain gangliosides (GM1, GD1b, GD1a, and GT1b) on the adsorption and rupture of phospholipid vesicles on SiO2 surfaces for the formation of supported lipid bilayer (SLB) membranes. Using quartz crystal microbalance with dissipation monitoring (QCM-D) we show that gangliosides GD1a and GT1b significantly slow the SLB formation process, whereas GM1 and GD1b have smaller effects. This is likely due to the net ganglioside charge as well as the positions of acidic sugar groups on ganglioside glycan head groups. Data is included that shows calcium can accelerate the formation of ganglioside-rich SLBs. Using fluorescence recovery after photobleaching (FRAP) we also show that the presence of gangliosides significantly reduces lipid diffusion coefficients in SLBs in a concentration-dependent manner. Finally, using QCM-D and GD1a-rich SLB membranes we measure the binding kinetics of an anti-GD1a antibody that has similarities to a monoclonal antibody that is a hallmark of a variant of Guillain-Barre syndrome.

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Picosecond time-resolved photon antibunching measures nanoscale exciton motion and the true number of chromophores

Nature Communications ◽

10.1038/s41467-021-21474-z ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Gordon J. Hedley ◽

Tim Schröder ◽

Florian Steiner ◽

Theresa Eder ◽

Felix J. Hofmann ◽

...

Keyword(s):

Rational Design ◽

Three Dimensional ◽

Dna Origami ◽

Fluorescent Nanoparticles ◽

Time Resolved ◽

Exciton Diffusion ◽

Polymer Aggregates ◽

True Number ◽

Particle Level ◽

Photon Antibunching

AbstractThe particle-like nature of light becomes evident in the photon statistics of fluorescence from single quantum systems as photon antibunching. In multichromophoric systems, exciton diffusion and subsequent annihilation occurs. These processes also yield photon antibunching but cannot be interpreted reliably. Here we develop picosecond time-resolved antibunching to identify and decode such processes. We use this method to measure the true number of chromophores on well-defined multichromophoric DNA-origami structures, and precisely determine the distance-dependent rates of annihilation between excitons. Further, this allows us to measure exciton diffusion in mesoscopic H- and J-type conjugated-polymer aggregates. We distinguish between one-dimensional intra-chain and three-dimensional inter-chain exciton diffusion at different times after excitation and determine the disorder-dependent diffusion lengths. Our method provides a powerful lens through which excitons can be studied at the single-particle level, enabling the rational design of improved excitonic probes such as ultra-bright fluorescent nanoparticles and materials for optoelectronic devices.

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Exchange Speed of Four-Component Nanorotors Correlates with Hammett Substituent Constants

Chemistry ◽

10.3390/chemistry3010009 ◽

2021 ◽

Vol 3 (1) ◽

pp. 116-125

Author(s):

Yi-Fan Li ◽

Amit Ghosh ◽

Pronay Kumar Biswas ◽

Suchismita Saha ◽

Michael Schmittel

Keyword(s):

Linear Correlation ◽

Bond Cleavage ◽

Head Group ◽

Ligand Interaction ◽

Exchange Frequency ◽

Rate Determining Step ◽

Head Groups ◽

Substituent Constants ◽

First Time ◽

Determining Factor

Three distinct four-component supramolecular nanorotors were prepared, using, for the first time, bipyridine instead of phenanthroline stations in the stator. Following our established self-sorting protocol to multicomponent nanodevices, the nanorotors were self-assembled by mixing the stator, rotators with various pyridine head groups, copper(I) ions and 1,4-diazabicyclo[2.2.2]octane (DABCO). Whereas the exchange of a phenanthroline vs. a bipyridine station did not entail significant changes in the rotational exchange frequency, the para-substituents at the pyridine head group of the rotator had drastic consequences on the speed: 4-OMe (k298 = 35 kHz), 4-H (k298 = 77 kHz) and 4-NO2 (k298 = 843 kHz). The exchange frequency (log k) showed an excellent linear correlation with both the Hammett substituent constants and log K of the copper(I)–ligand interaction, proving that rotator–copper(I) bond cleavage is the key determining factor in the rate-determining step.

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