Ionic Detergent Compatibility Reagent for Pierce™ 660nm Protein Assay Reagent - FAQs

The Thermo Scientific 660 nm Protein Assay can quantify peptides that are at least 2,500 Da if their compositions include amino acid residues that react with the dye-metal reagent (i.e., histidine, arginine, tyrosine, tryptophan and phenylalanine). For peptides smaller than 2,500 Da, use the Fluoraldehyde Reagent Solution (Cat. No. 26025), which detects amino groups.

Other peptide quantitation assays we offer are Thermo Scientific Pierce Quantitative Colorimetric Peptide Assay (Cat. No. 23275) and Thermo Scientific Pierce Quantitative Fluorometric Peptide Assay (Cat. No. 23290).

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The assay's linear range is 25-2,000 µg/mL using the test tube procedure and 50-2,000 µg/mL using the microplate procedure.

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If a 660nm filter is not available, the assay can be measured at wavelengths from 645 to 670nm; however, the assay linear range is 25-2,000 µg/mL and occurs only when the absorbance of the dye-protein complex is measured at 660 nm. Measuring the absorbance at wavelengths other than 660nm will result in a decrease of the assay's linear range and might increase the minimum detection level (i.e., decrease sensitivity).

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The Thermo Scientific 660 nm Protein Assay has the following advantages: • Room temperature stability of the assay reagent • A greater linear range than the coomassie-based Bradford assays • Compatibility with commonly used detergents and reducing agents • Compatibility with samples lysed in Laemmli sample buffer • Rapid mix-and-read protocol

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We offer two formats: The complete kit (Cat. No. 22662) contains sufficient reagents for 300 test tube or 3,000 microplate assays and a set of pre-diluted BSA standards with concentrations from 125 to 2,000 µg/mL. The assay reagent (750 ml, Cat. No. 22660) is sufficient for 500 test tube or 5,000 microplate assays.

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The assay is based on a dye-metal complex that binds to proteins in an acidic solution. Upon binding, the reddish dye-metal complex changes to green, resulting in an absorbance shift measurable at 660 nm. The dye interacts mainly with basic residues, such as histidine, arginine and lysine and to a lesser extent, tyrosine, tryptophan and phenylalanine.

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We do not recommend storing the solution frozen.
Note: We also do not recommend storing it at 4 degrees C.

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Once IDCR is dissolved in the Pierce 660nm Protein Assay Reagent, it can only be stored for one day at room temperature. Since you may not need to use the entire amount of IDCR within one day, you can calculate how much you need that day and store the remaining amount longer than 24 hours. IDCR is stable at room temperature if the pouch is closed very well and stored away from moisture. It can even be stored in a box with desiccant.

Find additional tips, troubleshooting help, and resources within our Protein Assays and Analysis Support Center.