Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.3.1.177 (BIS)
 957 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effect of feed molar ratio of N-isopropylacrylamide (NIPAM) to poly(ethylene oxide) (PEO) on the particle formation of poly(N-isopropylacrylamide) (PNIPAM) and PEO block copolymers (PNIPAM-b-PEO) and their aggregation-collapse behavior have been studied in aqueous solutions. It is found that in the presence of cross-linking agent N,N'-methylenebisacryla-mide (BIS), different morphologies of PNIPAM-b-PEO copolymers can be obtained, including a grafting-like structure, a hemispherical core-shell structure and a well-defined core-shell nanoparticle, as the feed molar amount of NIPAM in the copolymerization is increased. The increase in temperature causes the self-aggregation of grafting-like copolymers and hemispherical particles due to the hydrophobic interaction between locally unshielded PNIPAM blocks prior to the conformational transition of PNIPAM. When the feed molar ratio of NIPAM to PEO exceeds a certain value, a well-defined core-shell nanoparticle can be produced during the copolymerization. At low concentrations, PNIPAM cores of single core-shell nanoparticles can undergo the conformational transition without aggregation. The increase in the concentration of the well-defined core-shell nanoparticles, however, results in a week aggregation at temperatures lower than the theta-temperature of pure PNIPAM due to the association of methyl groups at the periphery of PEO shells.
 ...
PMID:Particle formation and aggregation-collapse behavior of poly(N-isopropylacrylamide) and poly(ethylene glycol) block copolymers in the presence of cross-linking agent. 1538 64

We report on the fabrication of Cu2+-sensing thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) microgels labeled with metal-chelating acceptor and fluorescent reporter moieties. Cu2+ detection sensitivity can be considerably enhanced via thermo-induced collapse of the sensing matrix, which can easily optimize the relative spatial distribution of Cu2+-binding sites and fluorescence readout functionalities. A novel picolinamine-containing monomer with Cu2+-binding capability, N-(2-(2-oxo-2-(pyridine 2-yl-methylamino)ethylamino)ethyl)acrylamide (PyAM, 3), was synthesized at first. Nearly monodisperse Cu2+-sensing microgels were prepared via emulsion polymerization of N-isopropylacrylamide (NIPAM) in the presence of a nonionic surfactant, N,N'-Methylene-bis(acrylamide) (BIS), PyAM (3), and fluorescent dansylaminoethyl- acrylamide (DAEAM, 5) monomers at around neutral pH and 70 degrees C. At 20 degrees C, as-synthesized microgels in their swollen state can selectively bind Cu2+ over other metal ions (Hg2+, Mg2+, Zn2+, Pb2+, Ag+, and Al3+), leading to prominent quenching of fluorescence emission intensity. Above the volume phase transition temperature, P(NIPAM-co-PyAM-co-DAEAM) microgels exhibit increased fluorescence intensity. It was observed that Cu2+ detection sensitivity can be dramatically enhanced via thermo-induced microgel collapse at elevated temperatures. At a microgel concentration of 3.0x10(-6) g/mL, the detection limit drastically improved from approximately 46 nM at 20 degrees C to approximately 8 nM at 45 degrees C. The underlying mechanism for this novel type of sensor with thermotunable detection sensitivity was tentatively proposed.
 ...
PMID:Metal-chelating and dansyl-labeled poly(N-isopropylacrylamide) microgels as fluorescent Cu2+ sensors with thermo-enhanced detection sensitivity. 1970 45