Thermo Scientific™

Pierce™ 660nm Protein Assay Reagent

Catalog number:  22660

 Related applications:

Protein Assays and Analysis

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The Thermo Scientific Pierce 660 nm Protein Assay is a ready-to-use, detergent- and reducing agent-compatible assay reagent to quickly measure (A660 nm) total protein concentration compared to a protein standard.

The Pierce 660 nm Assay is more linear than coomassie-based Bradford assays and compatible with higher concentrations of most detergents, reducing agents and other commonly used reagents. The accessory Ionic Detergent Compatibility Reagent (IDCR) provides for even broader detergent compatibility, making this one of the only protein assays that is suitable for samples containing Laemmli SDS sample buffer with bromophenol blue. Although the Pierce 660 nm Protein Assay produces a higher level of protein-to-protein variation (37%) than other assays, such as the BCA Protein Assay, the simpler single-reagent format and broader substance compatibility make the Pierce 660 nm Assay more convenient for many routine applications. The Pierce 660 nm Protein Assay can be performed in either a test tube or microplate format.

Features of the 660 nm Protein Assay Reagent:

Versatile—works with a greater range of detergents and reducing agents than other dye-based assays
Fast—single reagent with a simple mix-and-read protocol; no working reagent to prepare
Accurate—produces standard curves that are more linear than with the Bradford assay method
Flexible—assay may be performed in test tubes or microplates
Conserve samples—requires only 10 µL for microplate or 100 µL for the test tube procedures
Convenient—room temperature storage means no waiting for reagent equilibration before use

How the Pierce 660nm Assay Detects Protein:
The Pierce 660nm Protein Assay is based on the binding of a proprietary dye-metal complex to protein in acidic conditions that causes a shift in the dye's absorption maximum, which is measured at 660nm. The dye-metal complex is reddish-brown and changes to green upon protein binding. The color change is produced by deprotonation of the dye at low pH facilitated by interactions with positively charged amino acid groups in proteins. Therefore, the dye interacts mainly with basic residues in proteins, such as histidine, arginine and lysine and to a lesser extent tyrosine, tryptophan and phenylalanine.

The color produced in the assay is stable and increases in proportion to a broad range of increasing protein concentrations, even in the presence of detergents and reducing agents that would be incompatible with Bradford and BCA Protein Assays. The optional IDCR may be added to the assay reagent to increase compatibility with high amounts of ionic detergents, allowing samples containing Laemmli SDS sample buffer with bromophenol blue to be measured. The IDCR completely dissolves by thorough mixing and does not have any effect on the assay.

For more information, see the article "Chemistry of Protein Assays" in the Protein Methods Library.

Related Products
Pierce™ 660nm Protein Assay Kit
Ionic Detergent Compatibility Reagent for Pierce™ 660nm Protein Assay Reagent
WARNING: Reproductive Harm -
For Research Use Only. Not for use in diagnostic procedures.


Assay Type: Protein Quantitation Assay
Detection Method: Colorimetric
For Use With (Equipment): Microplate Reader, Spectrophotometer
Product Line: Pierce™
Product Size: 750 mL
Technique: Absorbance, Solution-based Detection

Contents & storage

Store the assay reagent at room temperature.


Manuals & protocols