2083-68-3Relevant articles and documents
Photoprocesses on Colloidal Clay Systems. 2. Quenching Studies and the Effect of Surfactants on the Luminescent Properties of Pyrene and Pyrene Derivatives Adsorbed on Clay Colloids
DellaGuardia, R. A.,Thomas, J. K.
, p. 3550 - 3557 (1983)
The cationic fluorescent probe trimethylammonium bromide (PN+) is adsorbed by the colloidal particles of the clay minerals montmorillonite and kaolin.The emission spectrum, polarization of fluorescence measurements, and transient fluorescence decay characteristics of PN+ are used to study the nature of its adsorbed state.Quaternary ammonium surfactants of varying hydrocarbon chain length cause a rearrangement of the PN+ molecules on the surface and decrease its interaction with the mineral surface.Quenching studies with nonionic andcationic molecules indicate that diffusion on the surface of montmorillonite is reduced below that observed in aqueous solution while the apparent rates obtained with kaolin particles are increased.Montmorillonite particles with a surfactant bilayer surrounding their surfaces are formed by the addition of an excess amount of surfactant to the colloid.The emission spectrum and the steady-state quenching studies yield information on the location of pyrene on these particles, as well as on the nature of the colloidal particles.
Striking improvement in peroxidase activity of cytochrome c by modulating hydrophobicity of surface-functionalized gold nanoparticles within cationic reverse micelles
Maiti, Subhabrata,Das, Krishnendu,Dutta, Sounak,Das, Prasanta Kumar
, p. 15021 - 15030 (2013/01/15)
This work demonstrates a remarkable enhancement in the peroxidase activity of mitochondrial membrane protein cytochrome c (cyt c) by perturbing its tertiary structure in the presence of surface-functionalised gold nanoparticles (GNPs) within cetyltrimethylammonium bromide (CTAB) reverse micelles. The loss in the tertiary structure of cyt c exposes its heme moiety (which is buried inside in the native globular form), which provides greater substrate (pyrogallol and H2O2) accessibility to the reactive heme residue. The surfactant shell of the CTAB reverse micelle in the presence of co-surfactant (n-hexanol) exerted higher crowding effects on the interfacially bound cyt c than similar anionic systems. The congested interface led to protein unfolding, which resulted in a 56-fold higher peroxidase activity of cyt c than that in water. Further perturbation in the protein's structure was achieved by doping amphiphile-capped GNPs with varying hydrophobicities in the water pool of the reverse micelles. The hydrophobic moiety on the surface of the GNPs was directed towards the interfacial region, which induced major steric strain at the interface. Consequently, interaction of the protein with the hydrophobic domain of the amphiphile further disrupted its tertiary structure, which led to better opening up of the heme residue and, thereby, superior activity of the cyt c. The cyt c activity in the reverse micelles proportionately enhanced with an increase in the hydrophobicity of the GNP-capping amphiphiles. A rigid cholesterol moiety as the hydrophobic end group of the GNP strikingly improved the cyt c activity by up to 200-fold relative to that found in aqueous buffer. Fluorescence studies with both a tryptophan residue (Trp59) of the native protein and the sodium salt of fluorescein delineated the crucial role of the hydrophobicity of the GNP-capping amphiphiles in improving the peroxidase activity of cyt c by unfolding its tertiary structure within the reverse micelles.
Odd-even effect and unusual behavior of dodecyl-substituted analogue observed in the crystal structure of alkyltrimethylammonium-[Ni(dmit) 2]- salts
Dai, Kotaro,Nomoto, Kuniharu,Ueno, Shinji,Tomono, Kazuaki,Miyamura, Kazuo
experimental part, p. 312 - 319 (2011/05/13)
A series of [Ni(dmit)2]- (dmit: 1,3-dithiole-2- thione-4,5-dithiolato) salts of alkyltrimethylammonium (Cn: n represents the alkyl chain length; n = 3 and 518) have been prepared and analyzed by X-ray structural analysis. All complex salts have been found to be composed of alternate sheets of [Ni(dmit)2]- anions and sheets of cations with a pronounced interdigitation of the alkyl chains. However, molecular arrangement differed between (C3)[Ni(dmit)2] and other (Cn)[Ni(dmit)2] (n = 518). Adjacent cations were aligned along the long axis of [Ni(dmit)2]- anion in C3 complex salt, while in others (C5-C18 complex salts), they were aligned toward the short axis. Such a difference in arrangement arose from correlativity between the lengths of the long axis of cation and anion, namely CLCA. Furthermore, relative orientation between the alkyl chain of cation and [Ni(dmit)2]- anion differed between the odd- and even-numbered cations for C10-C18. Whereas the plane of alkyl chain for odd-numbered cation was normal to the plane of [Ni(dmit)2]- anion, that of even-numbered cation was parallel. It was also found that C12 analog behaved like odd-numbered cations. However, in C12 salt, the end methyl group of the dodecyl group adopted unusual end-gauche conformation.
