Bradford protein assay

About: Bradford protein assay is a research topic. Over the lifetime, 635 publications have been published within this topic receiving 239107 citations.

Augmented COlorimetric NANoplasmonic (CONAN) Method for Grading Purity and Determine Concentration of EV Microliter Volume Solutions.

Abstract: This protocol paper describes how to assign a purity grade and to subsequently titrate extracellular vesicle (EV) solutions of a few microliters in volume by microplate COlorimetric NANoplasmonic (CONAN) assay. The CONAN assay consists of a solution of gold nanoparticles (AuNPs) into which the EV preparation is added. The solution turns blue if the EV preparation is pure, whereas it stays red if soluble exogenous single and aggregated proteins (SAPs; often referred to as protein contaminants) are present. The color change is visible by the naked eye or can be quantified by UV-Vis spectroscopy, providing an index of purity (a unique peculiarity to date). The assay specifically targets SAPs, and not the EV-related proteins, with a detection limit <50 ng/μl (an order of magnitude higher resolution than that of the Bradford protein assay). For pure solutions, the assay also allows for determining the EV number, as the color shift is linearly dependent on the AuNP/EV molar ratio. Instead, it automatically reports if the solution bears SAP contaminants, thus avoiding counting artifacts. The CONAN assay proves to be robust and reliable and displays very interesting performances in terms of cost (inexpensive reagents, run by standard microplate readers), working volumes (1-2 μl of sample required), and time (full procedure takes <1 h). The assay is applicable to all classes of natural and artificial lipid microvesicles and nanovesicles.

Determination of Proteins Based on Their Resonance Light Scattering Enhancement Effect on Alcian Blue 8GX

Abstract: A protein assay with the determination sensitivity at nanogram levels has been developed based on measurement of enhanced resonance light scattering (RLS). In a neutral aqueous medium, the interactions of ABGX with different proteins were found to result in strongly enhanced RLS signals. With the enhanced RLS signals at 398.0 nm, proteins, including bovine serum albumin (BSA), human serum albumin (HAS), pepsin (Pep) and cellulase (Cel), can be determined with the limit of detection below 30 ng/ml. The results of determinations for artificial samples were in agreement with the desired values, and those for human serum samples were identical with those obtained according to the Bradford method using CBB G-250.

Results and reliability of protein quantification for two-dimensional gel electrophoresis strongly depend on the type of protein sample and the method employed.

Abstract: We investigated the effects of tissue samples taken from rat brain on the reliability of three protein quantification kits: the Bradford assay, the 2-D Quant Kit, and the EZQ Protein Quantitation Kit. All three assays measured significantly smaller amounts of protein after extraction than the reference values before extraction. Only small effects were seen in homogenates, but very pronounced differences in membrane-enriched and highly lipophilic subcellular fractions. Researchers should evaluate which method of protein quantification is best qualified for their specific experimental design.