Nanoparticles from a Gold Complex with Sulfite Ion as Ligand: Preparation and Characterization

ABSTRACT

Gold colloidal nanoparticles (GNPs) were prepared by reducing a complex of Au⁺. Na₃Au(SO₃)₂ with sodium citrate. The procedure provides control of the dimension of nanoparticles produced, which is a function of reaction time and concentration of reactants. The nanoparticles were separated by centrifugation and their characteristics and dimensions were studied using UV-Vis and IR spectroscopy and transmission electronic microscopy (TEM).     

POSTMORTEM CHANGES IN CYTOSKELETAL ELEMENTS OF FISH MUSCLE1

Transmission electron microscopic examination of samples from fresh and 7 days-cold-stored white croaker skeletal muscle did not reveal apparent changes in overall structure of contractile elements of muscle. However, when purified myofibrils obtained from fresh and stored muscles were extracted with 0.6 M KI and the residues were examined in the scanning electron microscope, a progressive disappearance of exosarcomeric longitudinal filaments connecting successive Z structures was observed. Electrophoretic analysis of myofibrillar proteins obtained from fresh and stored muscles showed a marked degradation of nebulin, a major component of the endosarcomeric cytoskeletal network, whereas the other protein constituents of myofibrils remained practically unchanged. These alterations in elements of both cytoskeletal lattices of muscle may have important effects on physical properties of fish meat.     

Effect of Adjusting the Water Activity to 0.95 with Different Solutes on the Kinetics of Thiamin Loss in a Model System

The kinetics of thiamin degradation in a model system of pH 6.0 and water activity (a_w) 0.95 controlled with NaCl, KC1, glycerol or Na₂SO₄, was studied. The type of solute used to adjust a_w, had a dramatic influence on the rate of degradation of thiamin. The loss of vitamin increased in the following order: NaCl > KCl > glycerol > Na₂SO₄. Activation energies, however, were independent of the type of solute and ranged between24–28 kcallmole.     

A 66-kDa protein of bovine hypophyseal <i>Pars tuberalis</i> induces luteinizing hormone release from rat <i>Pars distalis</i>

In this study, evidence for a factor secreted by bovine hypophyseal pars tuberalis that stimulates luteinizing hormone (LH) release from rat pars distalis cells is shown. The secretion products of bovine pars tuberalis cells into the culture medium were assayed on dispersed rat pars distalis cells in 30 min incubations and superfusion experiments. The culture medium from pars tuberalis total cell populations, added at a dose of 6 μg per tube, induced the greater LH release from pars distalis cells, without effect on follicle stimulating hormone (FSH) release. After pars tuberalis cells separation on a discontinuos Percoll gradient, only the culture medium of cells from 50 and 60% strength Percoll were able to release LH from rat pars distalis cells. Therefore, cell fractions from 50 and 60% strenght Percoll were cultured together. To elicit maximal LH release (6 times the basal output), with the addition of 2 μg of pars tuberalis protein was required, suggesting that these cells produce the factor or factors which affect pars distalis gonadotrope cells. After applying the pars tuberalis culture medium on 12% SDS-PAGE, the band with biological activity was that of 66-kDal. Fifty ng protein of its eluate released almost 9 times the basal output of LH from pars distalis cells. Results suggest a modulating effect of a protein from the bovine pars tuberalis on rat cultured gonadotrope cells from the pars distalis.     

Review: Kinetic parameters for thiamine degradation in foods and model solutions of high water activity

Literature data for the rates of thiamine destruction in a wide variety of model systems, buffer solutions and foods have been used to determine the kinetics of thiamine destruction during processing. A range of conditions, including temperature, pH, oxygen and catalysts indicate that, in most cases, the destruction of thiamine follows first order reaction kinetics. When information is limited, these calculations may be used to extrapolate data and predict modifications of processing to minimize losses of thiamine.     

A Simplified Myosin Preparation from Marine Fish Species

A simple and rapid method for the purification of fish myosin with high yield was developed. The method consisted of washing chopped fish muscle with a 0.1M KCl solution, an extraction of myosin with a 0.45M KCl solution containing ATP, and steps of reprecipitation and redissolution by changes in ionic strength. Actin can easily be obtained as a component of the myosin preparation.     

Extraction of Mutagens from Chlorinated Poultry Chiller Water

Poultry chiller water (PCW) was used as a model to study the formation of mutagens that can result from chlorinating waters of high organic content. The Ames Salmonella mutagenicity test was used to evaluate solvent extracts of PCW. Pentane gave satisfactory extraction of mutagens without the emulsion problem encountered with dichloromethane, permitting the use of pentane in continuous extractors. Use of thiosulfate to remove residual chlorine in samples resulted in low mutagenicity. Mutagens were formed within minutes of chlorination and continued to change in amount during the next 1-2 hr. Mutagen formation was affected by pH and was proportional to chlorine dosage.