Sabina Bancila

In order to emphasize modifications on living organisms resulted from interaction with heavy metals, we applied a simple, sensitive, quick, inexpensive and reproducible method. It evaluates modifications through determining released amino acids. This method comprises three stages: treating plants with the investigated heavy metals, extracting resulted amino acids and dosing them with a ninhydrin reagent. The colored solution resulted from ninhydrin dosing is spectrophotometrically measured at 516 nm. The Lambert-Beer law is valid within the concentration field of 0-20 μg mL–1. .

We report the mass spectrometric analysis of zeins extracted from degreased maize flour with either an aqueous 70% ethanol solution or 60% acetonitrile containing 10 mM dithiothreitol. The analysis was performed on a MALDI-TOF mass spectrometer using α-cyano-4-hydroxycinnamic acid as matrix. The method allowed the detection of α-, β- and γ-zeins, but not δ-zeins and was used for the analysis of zein content in the maize inbred KWS 3381 and in commercial flour at different flour particles sizes: between 710 μm and 1.0 mm, between 250 μm and 355 μm and smaller than 100 μm.

The need for a simple and accurate method for protein estimation in alcoholic extracts led to the reexamination of the optimum conditions of a colorimetric assay based on the biuret reaction. Sonication time and the other experimental parameters were optimized after kinetics study on the extraction of either zein or total proteins. Zein extraction and purity were investigated by (1)H and (13)C NMR spectroscopy, SDS-PAGE electrophoresis, and UV-visible spectrophotometry (UV-vis). A zein assay was proposed, which involves the reaction of copper ions in copper phosphate powder with zein extracted in ethanolic solutions under strong alkaline environment. Furthermore, we extended this procedure to determine total proteins in maize samples simultaneously with their ultrasonic-assisted (US) extraction with an alkaline-alcoholic solution. Proteins in both types of extracts were well characterized by UV-vis spectroscopy. However, the 545nm absorbance of the violet-colored supernatants which is proportional to the protein content was found to be the key parameter of the improved biuret-based protein assay. Comparison of values obtained by this procedure and by Micro-Kjeldahl method was in excellent agreement. A scaled-down procedure agreed well with the standard procedure. Enhanced accuracy and repeatability was found in protein determination in maize using the modified biuret method. The optimization of reagent concentrations and incubation times were studied as well.

The need for a simple and accurate method for protein estimation in alcoholic extracts led to the reexamination of the optimum conditions of a colorimetric assay based on the biuret reaction. Sonication time and the other experimental parameters were optimized after kinetics study on the extraction of either zein or total proteins. Zein extraction and purity were investigated by (1)H and (13)C NMR spectroscopy, SDS-PAGE electrophoresis, and UV-visible spectrophotometry (UV-vis). A zein assay was proposed, which involves the reaction of copper ions in copper phosphate powder with zein extracted in ethanolic solutions under strong alkaline environment. Furthermore, we extended this procedure to determine total proteins in maize samples simultaneously with their ultrasonic-assisted (US) extraction with an alkaline-alcoholic solution. Proteins in both types of extracts were well characterized by UV-vis spectroscopy. However, the 545nm absorbance of the violet-colored supernatants which is proportional to the protein content was found to be the key parameter of the improved biuret-based protein assay. Comparison of values obtained by this procedure and by Micro-Kjeldahl method was in excellent agreement. A scaled-down procedure agreed well with the standard procedure. Enhanced accuracy and repeatability was found in protein determination in maize using the modified biuret method. The optimization of reagent concentrations and incubation times were studied as well.