Search results for "Colloid"

Design, synthesis and stimuli responsive gelation of novel stigmasterol-amino acid conjugates.

2020

Abstract An efficient synthesis of three novel stigmasterol-amino acid (glycine, l -leucine and l -phenylalanine) conjugates as stimuli responsive gelators is reported. The gelation properties of the prepared compounds were investigated in a variety of organic as well as aqueous solvents. The most striking finding of our investigation was that the hydrochloride salts of the prepared conjugates acted as gelators, whereas the neutral conjugates were either non-gelators or formed only a weak gel in anisole. The hydrochloride salts of stigmasteryl glycinate and l -leucinate form gels in n-alcohols (n = 4–10) and in ethane-1,2-diol, and that of stigmasteryl l -phenylalaninate forms gels in aroma…

Enantiospecific Response in Cross-Polarization Solid-State Nuclear Magnetic Resonance of Optically Active Metal Organic Frameworks.

2020

We report herein on a NMR-based enantiospecific response for a family of optically active metal-organic frameworks. Cross-polarization of the 1H-13C couple was performed, and the intensities of the 13C nuclei NMR signals were measured to be different for the two enantiomers. In a direct-pulse experiment, which prevents cross-polarization, the intensity difference of the 13C NMR signals of the two nanostructured enantiomers vanished. This result is due to changes of the nuclear spin relaxation times due to the electron spin spatial asymmetry induced by chemical bond polarization involving a chiral center. These experiments put forward on firm ground that the chiral-induced spin selectivity e…

In vivo NMR at 800 MHz to monitor alkaloid metabolism in plant cell cultures without tracer labeling.

2001

How Low Can You Go? Low Densities of Poly(ethylene glycol) Surfactants Attract Stealth Proteins.

2018

It is now well-established that the surface chemistry and “stealth” surface functionalities such as poly(ethylene glycol) (PEG) chains of nanocarriers play an important role to decrease unspecific protein adsorption of opsonizing proteins, to increase the enrichment of specific stealth proteins, and to prolong the circulation times of the nanocarriers. At the same time, PEG chains are used to provide colloidal stability for the nanoparticles. However, it is not clear how the chain length and density influence the unspecific and specific protein adsorption keeping at the same time the stability of the nanoparticles in a biological environment. Therefore, this study aims at characterizing the…

End Capping Ring-Opening Olefin Metathesis Polymerization Polymers with Vinyl Lactones

2008

The selective placement of a functional group at the chain end of a ring-opening metathesis polymer using ruthenium carbene initiators has been a significant limitation. Here we demonstrate a highly effective and facile end-capping technique for ROMP with living ruthenium carbene chain ends using single-turnover olefin metathesis substrates. Vinylene carbonate and 3H-furanone are introduced as functionalization and termination agents for the ruthenium-initiated ring-opening metathesis polymerization. This leads directly to the formation of functional polymer end groups without further chemical transformation steps. Aldehyde and carboxylic acid end groups can be introduced by this new method…

Rotational Correlation Functions of Single Molecules

2004

Single molecule rotational correlation functions are analyzed for several reorientation geometries. Even for the simplest model of isotropic rotational diffusion our findings predict non-exponential correlation functions to be observed by polarization sensitive single molecule fluorescence microscopy. This may have a deep impact on interpreting the results of molecular reorientation measurements in heterogeneous environments.

Stimuli responsive hybrid magnets : tuning the photoinduced spin-crossover in Fe(III) complexes inserted into layered magnets

2013

The insertion of a [Fe(sal_2 trien)]^+ complex cation into a 2D oxalate network in the presence of different solvents results in a family of hybrid magnets with coexistence of magnetic ordering and photoinduced spin crossover (LIESST effect) in compounds [Fe^{III}(sal_2 trien)][Mn^{II}Cr^{III}(ox)_3]·CHCl_3 (1·CHCl_{3}) [Fe^{III}(sal_{2} trien)][Mn^{II}Cr^{III}(ox)_{3}]·CHBr_{3} (1·CHBr_{3}) and [Fe^{III}(sal_{2} trien)][Mn^{II}Cr^{III}(ox)_{3}]·CH_{2}Br_{2} (1·CH_{2}Br_{2}). The three compounds crystallize in a 2D honeycomb anionic layer formed by Mn^{II} and Cr^{III} ions linked through oxalate ligands and a layer of [Fe(sal_{2} trien)]^{+} complexes and solvent molecules (CHCl_{3} CHBr_{…

Metal-Controlled Magnetoresistance at Room Temperature in Single-Molecule Devices

2017

The appropriate choice of the transition metal complex and metal surface electronic structure opens the possibility to control the spin of the charge carriers through the resulting hybrid molecule/metal spinterface in a single-molecule electrical contact at room temperature. The single-molecule conductance of a Au/molecule/Ni junction can be switched by flipping the magnetization direction of the ferromagnetic electrode. The requirements of the molecule include not just the presence of unpaired electrons: the electronic configuration of the metal center has to provide occupied or empty orbitals that strongly interact with the junction metal electrodes and that are close in energy to their F…

Fluorinated and pegylated polyaspartamide derivatives to increase solubility and efficacy of Flutamide

2012

New fluorinated amphiphilic copolymers based on a biocompatible polyaspartamide have been prepared in order to obtain polymeric micelles useful for delivering anticancer drugs. In particular, α,β-poly(N-2-hydroxyethyl)-d,l-aspartamide (PHEA) has been derivatized with polyethylene glycol (PEG(2000)) and ethylendiamine (EDA). Both these portions form the hydrophilic part of the copolymer, while the hydrophobic moiety is given by 1,2,4-oxadiazoles: 5-pentafluorophenyl-3-perfluoroheptyl-1,2,4-oxadiazole (PPOX) or 3-carboxyethyl-5-pentadecafluoroheptyl-1,2,4-oxadiazole (CPOX). Copolymers named PHEA-PEG(2000)-EDA-PPOX and PHEA-PEG(2000)-EDA-CPOX have been prepared with various degrees of derivati…

Poly(hydroxyethylaspartamide) derivatives as colloidal drug carrier systems

2003

Abstract Poly(hydroxyethylaspartamide) (PHEA) derivatives bearing at the polyaminoacidic backbone poly(ethyleneglycol) (2000 or 5000 Da) or both poly(ethyleneglycol) and hexadecylalkylamine as pendant moieties were investigated as polymeric colloidal drug carriers. The ability of the PHEA derivatives to solubilize hydrophobic drugs was investigated using paclitaxel, amphotericin B and methotrexate. The results demonstrated that the drug solubility depends on both macromolecule composition and drug physicochemical properties. In particular, PEG/hexadecylalkylamine co-grafting increased significantly the solubilization properties of PHEA for the considered drugs while the conjugation of PEG o…