Rapid separation of seed gliadins by reversed-phase ultra performance liquid chromatography (RP-UPLC) and its application in wheat cultivar and germplasm identification

To separate gliadin from wheat flour, a novel and stability-indicating reversed-phase ultra performance liquid chromatography (RP-UPLC) method is established and optimized. A comparative analysis of routine capillary electrophoresis (CE), reversed-phase high-performance liquid chromatography (RP-HPLC), and RP-UPLC was performed and the results showed that the resolution and efficiency of RP-UPLC were significantly higher than those of CE and RP-HPLC. Characteristic RP-UPLC patterns of different bread wheat variety and related species were readily identified. These results demonstrated that our RP-UPLC procedure resulted in significant improvements in sensitivity, speed, and resolution, and thus is highly useful in wheat cultivar and germplasm identification.

Quantitative assessment of moniliformin in cereals via alternative precipitation pathways, aided by LC-LIT-MS and LC-Q-TOF-MS

The availability of a simple chemical precipitation workflow aided by targeted and untargeted mass spectrometry would provide an accurate diagnostic platform for the direct determination of moniliformin in cereals for food safety control. In-house method validation was performed at six concentration levels of 8, 40, 80, 200, 400, and 600 ng g(-1) in cereal flours of wheat, corn, rye, oats and barley. Spiking experiments were made at three concentration levels of 20, 40 and 100 ng g(-1). Protein precipitation and "PHREE" column cleanup strategy provided recoveries of 81-108% for all cereals matrices using external calibrants. "PHREE" purification provided significant (p < 0.05) ion signal enhancement reduction advantage for all matrices except corn flour. Moniliformin underwent significant (p < 0.05) degradation over 2 weeks when prepared in acidified water. A simple, low-cost and fit-for-purpose procedure for the identification and quantitation of moniliformin in cereals becomes available to support prospective regulatory function.

Grain sorghum proteomics: integrated approach toward characterization of endosperm storage proteins in kafirin allelic variants

Grain protein composition determines quality traits, such as value for food, feedstock, and biomaterials uses. The major storage proteins in sorghum are the prolamins, known as kafirins. Located primarily on the periphery of the protein bodies surrounding starch, cysteine-rich β- and γ-kafirins may limit enzymatic access to internally positioned α-kafirins and starch. An integrated approach was used to characterize sorghum with allelic variation at the kafirin loci to determine the effects of this genetic diversity on protein expression. Reversed-phase high performance liquid chromatography and lab-on-a-chip analysis showed reductions in alcohol-soluble protein in β-kafirin null lines. Gel-based separation and liquid chromatography-tandem mass spectrometry identified a range of redox active proteins affecting storage protein biochemistry. Thioredoxin, involved in the processing of proteins at germination, has reported impacts on grain digestibility and was differentially expressed across genotypes. Thus, redox states of endosperm proteins, of which kafirins are a subset, could affect quality traits in addition to the expression of proteins.

Rapid characterization of wheat low molecular weight glutenin subunits by ultraperformance liquid chromatography (UPLC)

Low molecular weight glutenin subunits (LMW-GS), as important seed storage proteins, together with HMW-GS significantly define unique dough viscoelastic properties. In this study, a rapid ultraperformance liquid chromatography (UPLC) method for the separation and characterization of LMW-GS in wheat was optimized and established. The fast, reproducible, and high-resolution UPLC separation of LMW-GS could be obtained by gradually increasing eluting gradient from 21 to 47% in 30 min at flow rate of 0.55 mL/min and 60 °C for separation temperature. By this method, analysis of one sample could be completed in <20 min, significantly less time than the traditional reversed-phase high-performance liquid chromatography (RP-HPLC) method. Under the optimized conditions, the genetic features of LMW-GS and genotype × environmental interaction were successfully analyzed, leading to a fast identification of 17 main LMW-GS alleles that were related to different quality properties in wheat. The results demonstrated that UPLC could be a powerful and alternative tool for genetic and proteomic studies of wheat grain proteins and fast identification or screening of desirable LMW-GS alleles in wheat quality improvement.

Joule heating effects on separation efficiency in capillary zone electrophoresis with an initial voltage ramp

An analytical model is developed to quantify the Joule heating effects on the separation efficiency in CZE with an initial voltage ramp. This model considers the temporal variations of nonuniform temperature and flow fields in the course of voltage ramping. The temperature dependence of electrical conductivity, dynamic viscosity, and mass density of the fluid is also taken into account. We demonstrate that the application of an initial voltage ramp delays the development of pressure-driven flows induced passively by the axial temperature gradients. The thermal dispersion is thus significantly reduced, resulting in a higher theoretical plate number in CZE. Such improvement in the separation efficiency is apparent in noncoated capillaries at high electric fields with an appropriate voltage ramp-up time. These predictions are consistent with previous observations in both aqueous and nonaqueous CZE that took place in uncoated capillaries. In coated capillaries where the EOF is suppressed, however, our model predicts a lower plate number in the presence of an initial voltage ramp.

Capillary electrophoresis of proteins 2003-2005

This review article with 304 references describes recent developments in CE of proteins, and covers the two years since the previous review (Hutterer, K., Dolník, V., Electrophoresis 2003, 24, 3998-4012) through Spring 2005. It covers topics related to CE of proteins, including modeling of the electrophoretic migration of proteins, sample pretreatment, wall coatings, improving separation, various forms of detection, special electrophoretic techniques such as affinity CE, CIEF, and applications of CE to the analysis of proteins in real-world samples including human body fluids, food and agricultural samples, protein pharmaceuticals, and recombinant protein preparations.

Development of a capillary electrophoresis method for the determination of soybean proteins in soybean-rice gluten-free dietary products

CE has been applied for the first time to the simultaneous separation of soybean and rice proteins. Treated and untreated capillaries with different effective lengths as well as separation media at different pHs were tested. For that purpose, samples and standard solutions were prepared in 25:75 ACN-water media containing 0.3% v/v acetic acid. The use of an untreated capillary of 50 cm effective length together with an 80 mM borate buffer (pH 8.5) modified with 20% v/v ACN and UV detection at 254 nm were the conditions working the best. These conditions enabled the determination of soybean proteins in gluten-free dietary commercial products elaborated with soybean protein and/or soybean flour and rice flour using the standard additions calibration method. The method was linear up to 26 mg/mL of soybean proteins, the precision (expressed as RSD) was always better than 6%, and recoveries obtained for soybean proteins when spiking commercial products were very close to 100%.

Recent advances in the application of capillary electromigration methods for food analysis

This article reviews the latest developments in the application of capillary electromigration methods for the analysis of foods and food components. Nowadays, methods based on CE techniques are becoming widely used in food analytical and research laboratories. This review covers the application of CE to analyze amino acids, biogenic amines, peptides, proteins, DNAs, carbohydrates, phenols, polyphenols, pigments, toxins, pesticides, vitamins, additives, small organic and inorganic ions, chiral compounds, and other compounds in foods, as well as to investigate food interactions and food processing. The use of microchips as well as other foreseen trends in CE analysis of foods is discussed. Papers that were published during the period June 2002-June 2005 are included following the previous review by Frazier and Papadopoulou (Electrophoresis 2003, 24, 4095-4105).