Derivatization of fatty alcohol ethoxylate non-ionic surfactants using 2-sulfobenzoic anhydride for characterization by liquid chromatography/mass spectrometry.

A derivatization procedure has been developed for the improved characterization of fatty alcohol ethoxylate non-ionic surfactants by liquid chromatography/mass spectrometry. The end hydroxyl group of each surfactant species was converted into an oxycarbonylbenzene-2-sulfonic acid group with 2-sulfobenzoic anhydride under mild conditions. The produced sulfonic acid group allows all species, including fatty alcohols and those with less than three ethoxylates, to be uniformly ionized by electrospray ionization (ESI) mass spectrometry.

Colloidal encapsulation of hydrolytically and oxidatively unstable organoborane catalysts and their use in waterborne acrylic polymerization.

Trialkylborane catalysts and their amine complexes are hydrolytically and oxidatively unstable, decomposing in water very rapidly to trialkylboroxin, borate esters, and boric acid. However, trialkylborane-amine complexes will rapidly partition to a colloidal phase and remain surprisingly stable for long periods of time (>3 months) until such time as the catalyst is brought into an environment convenient for phase transfer. We show that tributylborane-amine complexes can be stored in aqueous solutions of several water-miscible polymers.

Error analysis for NMR polymer microstructure measurement without calibration standards.

We report an error analysis method for primary analytical methods in the absence of calibration standards. Quantitative (13)C NMR analysis of ethylene/1-octene (E/O) copolymers is given as an example. Because the method is based on a self-calibration scheme established by counting, it is a measure of accuracy rather than precision.

Penultimate effect in ethylene-styrene copolymerization and the discovery of highly active ethylene-styrene catalysts with increased styrene reactivity.

For the first time commercially relevant catalysts for the copolymerization of ethylene and styrene have been identified. The catalysts maintain very high copolymer efficiencies at relatively high reactor temperatures without sacrificing styrene comonomer reactivity. The observations which led to this discovery are based upon the kinetic analysis of ethylene-styrene copolymerization using constrained geometry catalyst (eta5-C5Me4)(SiMe2-N-t-Bu)TiMe2 (1).

1H nuclear-magnetic-resonance studies of the three-dimensional structure of the cardiotoxin CTXIIb from Naja mossambica mossambica in aqueous solution and comparison with the crystal structures of homologous toxins.

Using the previously reported sequence-specific 1H-NMR assignments, structural constraints for the cardiotoxin CTXIIb from Naja mossambica mossambica were collected. These include distance constraints from nuclear Overhauser enhancement measurements both in the laboratory and in the rotating frame, dihedral angle constraints derived from spin-spin coupling constants, and constraints from hydrogen bonds and disulfide bridges. Structure calculations with the distance geometry program DISMAN confirmed the presence of the previously identified antiparallel beta-sheets formed by residues 1-5 and 10-14, and by 20-27, 35-39 and 49-55, and established the nature of the connections between the individual beta-strands.