Aqueous Polymerization of Methyl Methacrylate Initiated by Potassium Peroxydisulfate-Ascorbic Acid Redox System

The aqueous polymerization of methyl methacrylate initiated by the redox system K₂S₂O₈-ascorbic acid has been studied at 35°C under the influence of oxygen. The rate of polymerization increases with increasing ascorbic acid concentration at low activator concentration, remains constant within the range 4.375 × 10^?3 to 11.25 × 10^?3 mole/liter, and at higher ascorbic acid concentration again decreases. The rate varies linearly with monomer concentration. The initial rate and the limiting conversion increase with increasing polymerization temperature. Organic solvents (water-miscible only) and small amounts of neutral salts like KC1 and Na₂SO₄ depress the initial rate and the maximum conversion. The addition of small amounts of salts like Cu²⁺ and Mn²⁺ increases the initial rate, but no appreciable increase in the limiting conversion is observed.     

Vinyl Polymerization Initiated by Peroxydiphosphate. IV. Polymerization of Acrylonitrile Initiated by Peroxydiphosphate-Thioacetamide Redox System

Abstract

The kinetics of the aqueous polymerization of acrylonitrile initiated by the peroxydiphosphate-thioacetamide redox system was investigated at 35, 40, and 50°C. The rates of polymerization were measured at different concentrations of oxidant, activator, and monomer. Peroxydiphosphate alone did not initiate polymerization under deaerated and undeaerated conditions. Addition of certain water-miscible organic solvents and neutral salts depress the rate and conversion. On the basis of experimental observations of the dependence of the rate of polymerization on various variables, a suitable kinetic scheme has been proposed.     

Vinyl Polymerization Initiated by Metal Chelates. III. Polymerization of Methyl Methacrylate Initiated by Vanadium(IV) Acetylacetonate Chelates

The polymerization of methyl methacrylate initiated by the vanadium acetylacetonate complex was investigated under a nitrogen atmosphere at 50°C. The effect of concentration of monomer, complex, acid, dioxane, inhibitor, and the effect of temperature on the rate of polymerization were studied. The rate of polymerization was found to increase upon increasing the concentrations of the monomer, the initiator, and the acid. The overall activation energy has been computed from the Arrhenius plot and a suitable kinetic scheme has been proposed.     

A Convenient Synthesis of Vinyl Epoxides from Glycidic Esters via α-Hydroxy-β,γ-unsaturated Esters

Glycidic esters, upon isomerisation with BF₃.Et₂O yield α-hydroxy-β,γ-unsaturated esters. These are then reduced with LiAlH₄ to vicinal diols which are converted to vinyl epoxides in two steps.     

Surface-anchored poly(2-vinyl-4,4-dimethyl azlactone) brushes as templates for enzyme immobilization

We explored surface-anchored poly(2-vinyl-4,4-dimethyl azlactone) (PVDMA) brushes as potential templates for protein immobilization. The brushes were grown using atom transfer radical polymerization from surface-anchored initiators and characterized by a combination of ellipsometry, atomic force microscopy, and X-ray photoelectron spectroscopy. RNase A was immobilized as a model enzyme through the nucleophilic attack of azlactone by the amine groups in the lysines located in the protein. The surface density of RNase A increased linearly from 5 to 50 nm. For 50 nm thick poly(2-vinyl-4,4-dimethyl azlactone) brushes, 7.5 microg/cm2 of RNase A was bound. The kinetics and thermodynamics of RNase A immobilization, the activity relative to surface density, and the pH and temperature dependence were examined. A Langmuir-like model for binding kinetics indicates that the kinetics are controlled by the rate of adsorption of RNase A and has an adsorption rate constant, k(ads), of 2.8 x 10(-8) microg(-1) s(-1) cm3. A maximum relative activity of approximately 0.95, which is near the activity of free RNase A, was reached at 1.2 microg/cm2 (approximately 3.0 monolayers) of immobilized RNase A. The immobilized RNase A had a similar temperature and pH dependence as free RNase A, indicating no significant change in conformation. The PVDMA template was extended to other biotechnologically relevant enzymes, such as deoxyribonuclease I, glucose oxidase, glucoamylase, and trypsin, with relative activities higher than or comparable to those of enzymes immobilized by other means. PVDMA brushes offer an efficient route to immobilize proteins via the ring opening of azlactone without the need for activation or pretreatment while retaining high relative activities of the bound enzymes.     

Influence of terminal substitution on structural, DNA, protein binding, anticancer and antibacterial activities of palladium(II) complexes containing 3-methoxy salicylaldehyde-4(N) substituted thiosemicarbazones

The variable chelating behavior of 3-methoxysalicylaldehyde-4(N)-substituted thiosemicarbazones was observed in equimolar reactions with [PdCl(2)(PPh(3))(2)]. The new complexes were characterized by various analytical, spectroscopic techniques (mass, (1)H-NMR, absorption, IR). All the new complexes were structurally characterized by single crystal X-ray diffraction. Crystallographic results showed that the ligands H(2)L(1) and H(2)L(4) are coordinated as binegative tridentate ONS donor ligands in the complexes 1 and 4 by forming six and five member rings. However, the ligands H(2)L(2) and H(2)L(3) bound to palladium in 2 and 3 as uninegative bidentate NS donors by forming a five member chelate ring. From this study, it was found that the substitution on terminal 4(N)-nitrogen may have an influence on the chelating ability of thiosemicarbazone. The presence of hydrogen bonding in 2 and 3 might be responsible for preventing the coordination of phenolic oxygen to the metal ion. The interaction of the complexes with calf-thymus DNA (CT-DNA) has been explored by absorption and emission titration methods. Based on the observations, an electrostatic binding mode of DNA has been proposed. The protein binding studies were monitored by quenching of tryptophan and tyrosine residues in the presence of complexes using Lysozyme as model protein. Antibacterial activity studies of the complexes have been screened against pathogenic bacteria such as Enterococcus faecalis, Staphylococcus aureus, Escherichia coli, Klebsiella pneumonia and Pseudomonas aeruginosa. MIC50 values of the complexes showed that they exhibited significant activity against the pathogens and among them, 3 exhibited higher activity. Further, anticancer activity of the complexes on the lung cancer cell line A549 has also been studied.     

Charging of a dust particle in a plasma with a nonextensive ion distribution function

The dust charge neutralization in a plasma with nonextensive ions is considered. The condition that the total current to a grain be zero is expressed in terms of the Lambert function. The fall-off of the net negative dust charge is then considered and a parameter study conducted, assuming hydrogen as well as argon plasma. Owing to ion nonextensivity, the dust charge reduction becomes much faster. Moreover, stronger is the ions correlation, more important is the involved electron depletion for a complete dust “decharging”.     

Quantum dot bio-conjugate: as a western blot probe for highly sensitive detection of cellular proteins

In the present study, we report a quantum dot (QD)-tailored western blot analysis for a sensitive, rapid and flexible detection of the nuclear and cytoplasmic proteins. Highly luminescent CdTe and (CdTe)ZnS QDs are synthesized by aqueous method. High resolution transmission electron microscopy, Raman spectroscopy, fourier transform infrared spectroscopy, fluorescence spectroscopy and X-ray diffraction are used to characterize the properties of the quantum dots. The QDs are functionalized with antibodies of prostate apoptosis response-4 (Par-4), poly(ADP-ribose) polymerases and β actin to specifically bind with the proteins localized in the nucleus and cytoplasm of the cells, respectively. The QD-conjugated antibodies are used to overcome the limitations of conventional western blot technique. The sensitivity and rapidity of protein detection in QD-based approach is very high, with detection limits up to 10 pg of protein. In addition, these labels provide the capability of enhanced identification and localization of marker proteins in intact cells by confocal laser scanning microscopy.