Use of chemometric methodology in optimizing conditions for competitive binding partial filling affinity capillary electrophoresis

This work expands the knowledge of the use of chemometric response surface methodology (RSM) in optimizing conditions for competitive binding partial filling ACE (PFACE). Specifically, RSM in the form of a Box-Behnken design was implemented in flow-through PFACE (FTPFACE) to effectively predict the significance of injection time, voltage, and neutral ligand (neutral arylsulfonamide) concentration, [L(o)], on protein-neutral ligand binding. Statistical analysis results were used to create a model for response surface prediction via contour and surface plots at a given maximum response (DeltaRMTR) to reach a targeted K(b) = 2.50 x 10(6) M(-1). The adequacy of the model was then validated by experimental runs at the optimal predicted solution (injection time = 2.3 min, voltage = 11.6 kV, [L(o)] = 1.4 microM). The achieved results greatly extend the usefulness of chemometrics in ACE and provide a valuable statistical tool for the study of other receptor-ligand combinations.     

Stabilization of zwitterions in solution: phosphinic and phosphonic acid GABA analogues

The influence of treatment of electron correlation, size of basis set and choice of solvation model on the predicted stabilization of zwitterionic phosphinic and phosphonic acid gamma-aminobutyric acid (GABA) analogues is investigated using ab initio molecular orbital methods and density functional theory. Density functional theory with the B3LYP functional and a composite basis set composed of the 6-31+G(2df) basis for phosphorus atoms and the 6-31+G(d,p) basis set for all other atoms is found to give an acceptable tradeoff between accuracy and computational expense. Either directly optimizing zwitterionic conformers within the conductor-like screening solvation model (COSMO) or pre-optimizing as dihydrates and then applying the COSMO solvation model give an acceptable treatment of solvation in terms of determining stable solvated structures, although directly optimizing within COSMO is simpler and less computationally expensive. With this protocol, cis-constrained phosphinic and phosphonic acid GABA analogues, which exhibit lower affinities for GABAC receptors, are found to possess only folded, intramolecularly hydrogen bonded low energy conformers. Trans-constrained analogues, on the other hand, exhibit higher affinities for GABAC receptors and are found to exist only as partially folded stable conformers. Conformationally flexible analogues can attain folded, partially folded or fully extended conformations and also have high biological activity. These results imply that the partially folded conformation is likely to be the most biologically active.     

Organometallic Polymers. XXVII. Radical-Initiated Polymerization and Copolymerization of π-(2, 4-Hexadien-1-yl Acrylate) tricarbonyliron

The novel monomer, π-(2, 4-hexadiene- l-yl acrylate) tricarbonyliron (HATI), has been prepared by two routes. It was homopolymerized and copolymerized with acrylonitrile, vinyl acetate, styrene, and methyl acrylate in benzene solutions. In all cases azobisisobutyronitrile was the initiator. The relative reactivity ratios, where HATI is defined as M₁, were determined: r₁ = 0.34, r₂ = 0.74, M₂ = acrylonitrile; r₁ = 2.0, r₂ = 0.05, M₂ = 0.74, M₂ = acrylonitrile; r₁ = 2.0, r₂ = 0.05, M₂ = vinyl acetate; r₁ = 0.26, r₂ = 1.81, M₂ = styrene; and r₁ = 0.30, r₂ = 0.74, M₂ = methyl acrylate. The homo-and copolymers had high values of T_g. When polymerizations are carried out at high concentrations, a very high molecular weight tail is observed in HATI hompolymerizations and in HATI-methyl acrylate copolymerizations. The polymers were characterized by IR, gel permeation chromatography, viscosity, and differential scanning calorimetry studies. Finally, thermal decompositions carried out in air resulted in decomposition of the Fe(CO)₃ group, producing Fe₂O₃ as a fine powder. Thermal decomposition under nitrogen (in solution and on solids ground into KBr pellets) resulted in slow destruction of the Fe(CO)₃ groups but the resulting polymer mass was insoluble, and the question of what form the iron exists in (Fe metal, oxides, carbides, etc.) has not been answered.     

Recent Developments in Solid-Propellant Binders

Abstract

The complex and important role of the propellant binder in solid-propellant rockets is described. The severe weight problems of space exploratrion cause high propellant performance to be of major concern in a highly competitive field. Binders contribute to performance, not only in terms of fuel value, but by being compatible with energetic components and by providing good mechanical properties. Both sterilization required for planetary landings and compatibility problems of new energetic oxidizers generate new requirements too stringent for existing binders; only binders composed essentially of saturated aliphatic hydrocarbon are predicted to be suitable. Several saturated-binder developments are in progress. The achievements of one of these programs, based on free-radical synthesis, are evaluated against the goals of the new binder.     

Review of Chemometrics Applied to Spectroscopy: 1985-95, Part 3 — Multi-way Analysis

INTRODUCTION

In this third part of a review on chemometrics in spectroscopy we will describe a recent methodology that has attracted increasing interest in spectroscopy. namely multi-way analysis. The application of multi-way analysis in spectroscopy is still relatively new. hence many methodological improvements are being investigated currently. Part of thls review will also be used to describe the algorithmic improvements gained the last decade.     

Facile sequencing of oligosaccharides by matrix-assisted laser desorption/ionisation on a hybrid quadrupole orthogonal acceleration time-of-flight mass spectrometer.

N-Linked oligosaccharide mixtures released from a number of standard glycoproteins were derivatised with 3-acetylamino-6-acetylaminoacridine (AA-Ac) using reductive amination. Analysis of these mixtures using an experimental matrix-assisted laser desorption/ionisation (MALDI) hybrid quadrupole orthogonal acceleration time-of-flight (Q-TOF) mass spectrometer provided detailed information about the mass distribution of the glycan derivatives. Collision-induced dissociation of the singly protonated [M + H](+) ions also gave rise to a number of product ions produced by the sequential cleavage of the glycosidic linkages. As fragmentation of the positively charged species occurred predominantly in one direction, i.e., from the non-reducing end of the glycan to the AA-Ac moiety, a considerable amount of information could be obtained with ease about the sequence in which the sugar residues were attached to one another. This derivatisation procedure and mass spectrometric methodology were applied successfully to neutral and acidic glycans released from proteins separated by gel electrophoresis.     

Polymerization of Methane and Olefin Mixtures over Fluosulfonic Acid and Antimony Pentafluoride

Mixtures of methane and olefins (ethylene, propylene, butenes, butadiene, and styrene) have been polymerized over HSO₃ F-SbF₃ to yield an oily oligomer with a molecular weight ranging from 100 to 700. The NMR spectra of each polymer showed a sharp peak at or near 1.25 &, suggesting the presence of block methylene in the polymer. The formation of block methylene is surprising considering the fact that the polymerization reaction is carbonium ion in nature. A primary cation has been invoked to explain the results. The formation of this primary cation must involve some extraordinary stabilization by some component in the acid.     

Graft Copolymerizations of Polysaccharides. II. Acrylamide Grafting to Yellow Dextrin

Graft copolymers of acrylamide and yellow dextrin were prepared using cerium(IV) as initiator. The yellow dextrin had a very broad molecular weight distribution but was fractionated utilizing dialysis and ultrafiltration membranes. Initiator efficiencies were determined using size exclusion chromatography and were found to be between 2.4 and 34%. Initiator efficiency increased with acrylamide concentration at constant cerium (IV) and yellow dextrin concentrations, and decreased with increasing cerium(IV) concentration at constant acrylamide and yellow dextrin concentrations. Plots of acrylamide conversion and intrinsic viscosity vs initial acrylamide concentration at constant yellow dextrin and ceric ion concentrations showed a maximum at about 2.0 M.