Search results for "cationic polymerization"
showing 10 items of 441 documents
Kinetic studies of the interaction between DNA and polycations based on polyasparthylhydrazide
2008
Abstract In the present paper, a systematic kinetic study on the interaction between interpolyelectrolytes such as positive-charged polymers and DNA was carried out. In particular, a qualitative–quantitative kinetic investigation on the interaction between copolymers of the α,β-poly(aspartylhydrazide) and DNA calf thymus filaments was performed. This study gives a new model starting from a well known “pseudo-phase model”, and permits to give a qualitative explanation about the trends of experimentally observed kinetic constants by varying the concentration of one of the two poly-electrolytes. Moreover, this study permits to verify the dependence of the binding constants KPAHy–CPTA and KDNA …
Atomistic Simulations of Functional Au_{144}(SR)_{60} Gold Nanoparticles in Aqueous Environment
2012
Charged monolayer-protected gold nanoparticles (AuNPs) have been studied in aqueous solution by performing atomistic molecular dynamics simulations at physiological temperature (310 K). Particular attention has been paid to electrostatic properties that modulate the formation of a complex comprised of the nanoparticle together with surrounding ions and water. We focus on Au-144 nanoparticles that comprise a nearly spherical Au core (diameter similar to 2 nm), a passivating Au-S interface, and functionalized alkanethiol chains. Cationic and anionic AuNPs have been modeled with amine and carboxyl terminal groups and Cl-/Na+ counterions, respectively. The radial distribution functions show tha…
Membrane Transport of l-Arginine and Cationic Amino Acid Analogs
2000
Publisher Summary This chapter reviews the current knowledge of the mechanisms and regulation of cationic amino acids (CAA) carrier proteins and discusses the potential involvement of each transporter in supplying L-arginine for nitric oxide biosynthesis. The CAA L-arginine, the substrate for nitric oxide synthases (NOSs), is considered a semi-essential amino acid in most mammals. Consequently, mammalian cells must be capable of exchanging CAA with the environment. The bilayer of the plasma membrane is impermeable to polar molecules, and thus, specialized carrier proteins with distinct substrate specificity transport hydrophilic solutes such as amino acids. L-arginine shares the same transp…
Weak interactions between resorcinarenes and diquaternary alkyl ammonium cations
2005
The interactions of resorcin[4]arenes 1 with alkyl ammonium cations bearing a 1,4-diazabicyclo[2.2.2]octane (DABCO) scaffold (32+, 42+ and 52+) were analyzed in the solid state by X-ray crystallography, in solution by 1H NMR spectroscopy, and in the gas phase by ESI-TOF mass spectrometry. The results are complemented with AM1 calculations and compared to previous reports on complexation studies of resorcinarenes with quaternary alkyl ammonium cations. The NMR titration results indicate that there are hardly any differences in the binding of the quaternary tetramethyl ammonium cation 2+ and the diquaternary N,N’-dimethyl DABCO dication 42+. The large N,N’-dibenzyl DABCO dication 52+ has two …
Antidiabetic Behavior of Biguanides
1983
The existence of active electron pairs on some nitrogen atoms in phenformin hydrochloride is inferred from the presence of a hydrogen catalytic polarographic wave. This finding emphasizes the ability of biguanides to form hydrogen bridges with other molecular species such as amino acids and proteins, as well as to form coordination complexes with zinc and other metallic cations by means of these electron pairs. The antidiabetic action of phenformin and other related biguanides can be explained in terms of competition between these molecules and insulin to coordinate cationic oligoelements together with their ability to form hydrogen bonds between the biguanide moiety and insulin itself.
Cationic and Zwitterionic Polymerizable SurfactantsQuaternary Ammonium Dialkyl Maleates. 2. Emulsion Polymerization of Styrene and Butyl Acrylate
1998
Polymerizable cationic and zwitterionic dialkyl maleates with different hydrophobic chain lengths (R = C10H21, C12H25, C16H33, C18H37) and different counterions (I, Br, HSO4) for the cationic hydrophilic part, as well as some similar surfactants, dialkyl succinates, were used in batch and seeded emulsion polymerization of styrene and butyl acrylate. All surfactants, when used in emulsion polymerization, provide good stability to the styrene/butyl acrylate latices. A styrene/butyl acrylate latex prepared with sodium dodecyl sulfate (SDS) was used as a reference. Some stability tests for latices were performed, and the glass transition temperatures, as well as the molecular weights of the pol…
Hydrophobically Modified Halloysite Nanotubes as Reverse Micelles for Water-in-Oil Emulsion.
2015
An easy strategy to obtain inorganic reverse micelles based on halloysite nanotubes (HNTs) and alkyltrimethylammonium bromides has been developed. The selective modification of the HNTs external surface with cationic surfactants endows to generate tubular nanostructures with a hydrophobic shell and a hydrophilic cavity. The influence of the surfactants alkyl chain on the HNTs functionalization degree has been investigated. The dynamic behavior of the surfactant/HNT hybrids in solvents with variable polarity has been correlated to their affinity toward hydrophobic media explored through partition experiments. The water-in-oil emulsion is able to solubilize copper sulfate, proving the incorpo…
Buildup of ultrathin multilayer films by a self-assembly process: III. Consecutively alternating adsorption of anionic and cationic polyelectrolytes …
1992
A solid substrate with a positively charged planar surface is immersed in a solution containing an anionic polyelectrolyte and a monolayer of the polyanion is adsorbed. Since the adsorption is carried out at relatively high concentrations of polyelectrolyte, a large number of ionic residues remain exposed to the interface with the solution and thus the surface charge is effectively reversed. After rinsing in pure water the substrate is immersed in the solution containing a cationic polyelectrolyte. Again a monolayer is adsorbed but now the original surface charge is restored. By repeating both steps in a cyclic fashion, alternating multilayer assemblies of both polymers are obtained. The bu…
Controlling the dimensionality of oxalate-based bimetallic complexes: The ferromagnetic chain {[K(18-crown-6)][Mn(bpy)Cr(ox)3]}∞(18-crown-6=C12H24O6,…
2007
Abstract The bimetallic ferromagnetic chain {[K(18-crown-6)][Mn(bpy)Cr(ox)3]}∞ (1) has been synthesized and characterized. It crystallizes in the orthorhombic chiral space group P212121 [a = 9.0510(2) A, b = 14.4710(3) A, c = 26.8660(8) A, V = 3510.97(1) A3, Z = 2]. Compound 1 is made up by anionic [Mn(bpy)Cr(ox)3]− 1D chains and cationic [K(18-crown-6)]+ complexes. The magnetic exchange within the chain is ferromagnetic [J = +7.8(7) cm−1]. In the solid state, the ferromagnetic chains are well isolated magnetically and no long range magnetic ordering has been observed above 2 K.
Isolation of enantiomerically pure organometallic palladium compounds: synthesis of the triangles prepared from enantiopure [cis-Pd2(C6H4PPh2)2(NCCH3…
2009
Reaction of the racemic [Pd(C(6)H(4)PPh(2))Br](4) () with the silver salt of 1R-(1alpha,2beta,3alpha)]-3-methyl-2-(nitromethyl)-5-oxocyclopentaneacetate, (R)-AgO(2)CR*, results in the formation of a mixture of diastereoisomers (RRR)- and (SRR)- of the formula Pd(2)(C(6)H(4)PPh(2))(2)(O(2)CR*)(2) that were separated by standard chromatographic methods. Each diastereoisomer was readily converted into the tetrametallic stereoisomers (SS)- and (RR)-, of the formula [Pd(C(6)H(4)PPh(2))Br](4) that were isolated and characterized by X-ray crystallography. The R enantiomer of the solvated cationic species [cis-Pd(2)(C(6)H(4)PPh(2))(2)(NCCH(3))(4)](2+), obtained from (RR)-, was reacted with ammonium…