Improving sodium dodecyl sulfate polyacrylamide gel electrophoresis detection of low-abundance protein samples by rapid freeze centrifugation

This work presents a rapid and simple freeze centrifugation method to concentrate dilute protein solutions for detection by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS–PAGE) Coomassie blue staining. Moreover, a simple way to assemble a cryoconcentration device is presented, and its use is discussed. Commercial purified protein standard and an enzyme with high fructosyltransferase (FTase) activity, coming from target fractions obtained by chromatographic separation, were used as an example. FTase, coming directly from the chromatographic fractions, was difficult to view through SDS–PAGE analysis; however, it was easily visualized, and its activity was enhanced, after the application of the freeze centrifugation protocol presented here.     

Molecular and Morphological characterization of multiple nucleopolyhedrovirus from Mexico and their insecticidal activity against Spodoptera frugiperda (Lepidoptera: Noctuidae)

The fall armyworm (FAW), Spodoptera frugiperda (Lepidoptera: Noctuidae), is the most important pest of maize in many countries. Entomopathogenic viruses mainly Baculoviruses family are excellent biological control agents and therefore a viable alternative for managing this pest. The aim of this study was to determine the biological activity of eight native nucleopolyhedrovirus (NPVs) against FAW larvae. Additionally, two of the most virulent isolates (SfCH32 and SfCH15) were characterized biologically by bioassays to estimate their median lethal dose (LD₅₀) and median lethal time (LT₅₀), morphologically by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) and molecularly by restriction enzymes. Three (SfCH15, SfCH18 and SfCH32) of the eight tested native nucleopolyhedrovirus isolates caused mortalities ˃98% at 168-hr post-inoculation (hpi) with a dose of 9.2 × 10⁴ OBs/larva. SfCH15 and SfCH32 isolates showed occlusion bodies (OBs) of irregular shape and size (1.02–2.24 μm). The SfCH15 and SfCH32 isolates showed similar median lethal dose (5.6 × 10²–6.4 × 10² OBs/larva). The lowest median lethal time (114.5 hpi) was observed with the SfCH15 isolate at the highest concentration (2.5 × 10⁶ OBs/larva). The DNA restriction profiles for SfCH15 and SfCH32 were different, with their genome size being ~128,000 bp and 132,000 bp, respectively. SfCH15 and SfCH32 isolates showed similar morphological characteristics and the highest virulence against fall armyworm. This study showed that native isolates were highly virulent against S. frugiperda larvae, being similar to other reported strains; however, field studies are required to confirm their insecticidal effect.     

Method to concentrate protein solutions based on dialysis-freezing-centrifugation: enzyme applications

One of the recurrent methodological problems in preparative biochemical work is the concentration of dilute protein solutions, including culture supernatants resulting from biotechnological processes. A procedure was developed to concentrate enzymes by a novel cryoconcentration system. This approach includes a new device that facilitates the sample freezing and the subsequent solute elution from the frozen matrix by centrifugation. The optimal centrifugation conditions for this cryoconcentration system were obtained using whey protein solution as a model. The procedure was applied to concentrate dilute solutions of commercial pectinase, measuring the endopolygalacturonase (EPG) activity of this enzyme in the concentrate by a method based on the on-line torque measurement, and of recombinant fructan:fructan 1-fructosyltransferase (1-FFT) protein of Pichia pastoris from a culture in a bioreactor, as an expression system. The optimal centrifugation speed, time, and temperature were 6150 g, 20 min, and 4 °C, respectively. The concentration factors for the dilute protein solutions were 9.2-, 11.2-, and 17.1-fold for 1-FFT, whey, and commercial pectinase, respectively. Recoveries ranged from 87% to 93%. The procedure allowed concentrating proteins efficiently without affecting their enzymatic activity.     

Physicochemical,Thermal and Rheological Properties of Native and Oxidized Starch from Corn Landraces and Hybrids

Food Biophysics - Native starch was isolated from three corn landraces and a hybrid variety. The starches were oxidized with several concentrations of NaOCl (0.8, 2 and 5% w/w active chlorine). The...