If yes, what preparations (or method) that we need to make for preparing food sample before using UV spectrophotometry methods? For my case, the purification of protein sample is not required as i just need to estimate total protein (%) from food sample for initial food quality evaluation. And the food sample I received is usually in powder form (Not liquid).
Hi Patrick,
in general the answer is yes, however there are many assays available and the impact of detergents or pH on the assays vary. I am not sure what conditions you need to use to dissolve the product. You can check out sites that help guide assay selection such as; https://www.thermofisher.com/us/en/home/life-science/protein-biology/protein-assays-analysis/protein-assays/protein-assay-selection-guide.html?ef_id=EAIaIQobChMIw-
vcyICv6wIVAWKGCh2aEAtYEAAYASABEgLPv_D_BwE:G:s&s_kwcid=AL!3652!3!436793335085!p!!g!!bradford%20assay&cid=bid_pca_sbu_r01_co_cp1359_pjt0000_bid00000_0se_gaw_nt_pur_con&gclid=EAIaIQobChMIw-vcyICv6wIVAWKGCh2aEAtYEAAYASABEgLPv_D_BwE
Frank
Yes they can. Bradford Assay - Protein Quantitation. Measure protein concentration in 5 min at RT. Order now. Ready-to-use Bradford reagents available in multiple sizes for faster & convenient ease. Reliable Results. Easy-to-Use Reagents. Complete Workflows.
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The Bradford assay, a colorimetric protein assay, is based on an absorbance shift of the dye Coomassie Brilliant Blue G-250. The Coomassie Brilliant Blue G-250 dye exists in three forms: anionic (blue), neutral (green), and cationic (red). Under acidic conditions, the red form of the dye is converted into its blue form, binding to the protein being assayed. If there's no protein to bind, then the solution will remain brown. The dye forms a strong, noncovalent complex with the protein's carboxyl group by van der Waals force and amino group through electrostatic interactions.[1] During the formation of this complex, the red form of Coomassie dye first donates its free electron to the ionizable groups on the protein, which causes a disruption of the protein's native state, consequently exposing its hydrophobic pockets. These pockets in the protein's tertiary structure bind non-covalently to the non-polar region of the dye via the first bond interaction (van der Waals forces) which position the positive amine groups in proximity with the negative charge of the dye. The bond is further strengthened by the second bond interaction between the two, the ionic interaction. The binding of the protein stabilizes the blue form of the Coomassie dye; thus the amount of the complex present in solution is a measure for the protein concentration, and can be estimated by use of an absorbance reading.
https://en.m.wikipedia.org/wiki/Bradford_protein_assay
The Lowry protein assay is a biochemical assay for determining the total level of protein in a solution. The total protein concentration is exhibited by a color change of the sample solution in proportion to protein concentration, which can then be measured using colorimetric techniques.
https://en.m.wikipedia.org/wiki/Lowry_protein_assay
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