Molar mass distributions of linear homopolymers by size exclusion chromatography with light scattering detection: A method for automatic band broadening correction.

Size exclusion chromatography (SEC) equipped with a differential refractometer (DR) and a light scattering (LS) detector is a well-known technique for determining the molar mass distribution (MMD) of many polymers. In the case of narrow polymers, correction of the band broadening (BB) effect is necessary; but unfortunately, the available BB correction methods are rather impractical for most SEC users. This work proposes an automatic BB correction method for determining the MMD of narrow linear homopolymers (or multimodal homopolymers that include narrow modes) on the basis of SEC/(DR + LS) measurements.

Information-weighted constrained regularization for particle size distribution recovery in multiangle dynamic light scattering.

In particle size measurement with dynamic light scattering (DLS), it is difficult to get an accurate recovery of a bimodal particle size distribution (PSD) with a peak position ratio less than ~2:1, especially when large particles (>350nm) are present. This is due to the inherent noise in the autocorrelation function (ACF) data and the scarce utilization of PSD information during the inversion process. In this paper, the PSD information distribution in the ACF data is investigated.

Physicochemical characterization of water-soluble chitosan derivatives with singlet oxygen quenching and antibacterial capabilities.

New water-soluble chitosan derivatives (WSCh) were obtained by Maillard reaction (MR) between glucosamine (GA) with both low and medium molecular weight chitosans (Ch). The WSCh showed larger solubility than the respective Ch, while their deacetylation degree (DD) decreased by approximately 12%. Infrared spectroscopy experiments of WSCh confirmed the formation of imine bonds after MR with intensified pyranose structure, and sugar molecules as polymer branches.

Tracking control of concentration profiles in a fed-batch bioreactor using a linear algebra methodology.

Based on a linear algebra approach, this paper aims at developing a novel control law able to track reference profiles that were previously-determined in the literature. A main advantage of the proposed strategy is that the control actions are obtained by solving a system of linear equations. The optimal controller parameters are selected through Monte Carlo Randomized Algorithm in order to minimize a proposed cost index.

Optimisation and standardisation of an immunoagglutination assay for the diagnosis of Trypanosoma cruzi infection based on latex-(recombinant antigen) complexes.

Objective: To determine the conditions under which the immunoagglutination assay to detect Chagas disease, obtained from a novel latex-(chimeric recombinant antigen) complex, shows greater discrimination between the responses of a positive control serum and a negative control serum.

Methods: The following variables were determined: (i) the sensitisation mechanism, (ii) the emulsifier employed for protein desorption, (iii) the reaction time, (iv) the ionic strength of the reaction medium, (v) the particle concentration, (vi) the presence of blocking agents, (vii) the presence of polyethyleneglycol as potentiator of reaction and (viii) the antigen and antibody concentrations. The search of optimal conditions was investigated by varying one variable at a time.

Scleroglucan compatibility with thickeners, alcohols and polyalcohols and downstream processing implications.

Thickening capacity and compatibility of scleroglucan with commercial thickeners (corn starch, gum arabic, carboxymethylcellulose, gelatin, xanthan and pectin), glycols (ethylene glycol and polyethylene glycol), alcohols (methanol, ethanol, 1-propanol and isopropanol) and polyalcohols (sorbitol, xylitol and mannitol) was explored. Exopolysaccharides (EPSs) from Sclerotium rolfsii ATCC 201126 and a commercial scleroglucan were compared. Compatibility and synergism were evaluated taking into account rheology, pH and sensory properties of different thickener/scleroglucan mixtures in comparison with pure solutions.

Synthesis of latex-antigen complexes from single and multiepitope recombinant proteins. Application in immunoagglutination assays for the diagnosis of Trypanosoma cruzi infection.

The physical adsorption and the chemical coupling of recombinant proteins of Trypanosoma cruzi onto polystyrene and core-shell carboxylated particles were respectively investigated with the ultimate aim of producing latex-protein complexes to be used in an immunoagglutination assay able to detect the Chagas disease. To this effect, two single proteins (RP1 and RP5) and a multiepitope protein derived from three antigenic peptides (CP2) were evaluated, and sensitizations were carried out at different pHs. The maximum physical adsorption was produced at pHs close to the protein isoelectric point (i.

Immunodiagnosis of Chagas disease: Synthesis of three latex-protein complexes containing different antigens of Trypanosoma cruzi.

This article describes the physical adsorption and the chemical coupling of 3 antigenic proteins of Trypanosoma cruzi onto polystyrene (PS) based latexes to be used as novel immunodiagnosis reagents for detecting the Chagas disease. The coupled proteins were a homogenate of T. cruzi, or a recombinant protein (either Ag36 or CP1).

Arthroscopic fixation of displaced tibial eminence fractures: a new growth plate-sparing method.

Purpose: Fractures of the tibial eminence can be treated arthroscopically. Numerous ways to attach an anterior cruciate ligament avulsion from the tibial eminence have been designed. This report describes a new physis-sparing reduction and fixation technique using an anchor passing nonabsorbable braided sutures through the substance of the anterior cruciate ligament, holding the avulsed bone fragment by tying a locking knot.

Estimation of band broadening in size-exclusion chromatography. I. A method based on analyzing narrow standards with a molar mass-sensitive detector.

A method is proposed for estimating the (asymmetrical and non-uniform) band broadening function (BBF) in size-exclusion chromatography (SEC). The following data are required: the molar mass calibration and the concentration- and molar mass chromatograms of a set of narrow standards. In the narrow range of each standard, the BBF is uniform but skewed.

Alternative approaches for the estimation of the band broadening parameters in single-detection size exclusion chromatography.

New approaches for the determination of the extent of symmetric and asymmetric band broadening (BB) in size exclusion chromatography (SEC) are presented. For this purpose raw data was simulated by starting with either a theoretical Poisson number chain length distribution (NCLD), or a log-normal weight chain length distribution (WCLD). Each distribution was first converted to a BB-free mass chromatogram, as typically obtained from a standard differential refractive index detector.

Contamination by larger particles of two almost-uniform latices: analysis by combined dynamic light scattering and turbidimetry.

Multiangle dynamic light scattering (MDLS) and turbidimetry (T) were applied (both individually and combined) for determining the contamination by larger particles of two almost-uniform polystyrene (PS) latices. Latex 1 was synthesized in our laboratories, and it contained a main population diameter of 340 nm together with a small fraction of larger particles. This latex was used as the base material for producing an immunoassay kit.

Latex particle size distribution by dynamic light scattering: novel data processing for multiangle measurements.

Multiangle dynamic light scattering (DLS) provides a better estimate of particle size distributions (PSD) than single-angle DLS. However, multiangle data treatment requires appropriate weighting of each autocorrelation measurement prior to calculation of the PSD. The weighting coefficients may be directly obtained from (i).