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Silver Bullit™, Silver Stain Kit
Control Type
/
Quantification Method
/
Sample Type
/
Scientific Score
7.08
Brand
AMRESCO
Sizes
1 (50 Gels)
Available From
3 Vendors
Price Range
$ 189.70 - $ 216.43
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In Vitro Bacterial Split GFP Fold ′n′ Glow™ Solubility Assay Kit (green) SKU : appa001
Control Type
/
Quantification Method
/
Sample Type
/
Scientific Score
4.58
Brand
Sigma-Aldrich
Sizes
1 (1 Kit)
Available From
2 Vendors
Price Range
$ 515.00 - $ 648.66
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In Vitro Bacterial Split GFP Fold ′n′ Glow™ Solubility Assay Kit (cyan) SKU : appa008
Control Type
/
Quantification Method
/
Sample Type
/
Scientific Score
6.07
Brand
Sigma-Aldrich
Sizes
1 (1 Kit)
Available From
2 Vendors
Price Range
$ 642.00 - $ 806.88
Catalog IDs
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Bradford Reagent SKU : b6916
Scientific Score
6.19
Brand
Sigma-Aldrich
Sizes
1 (500 ml)
Available From
2 Vendors
Price Range
$ 72.90 - $ 107.32
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QuickTiter™ AAV Quantitation Kit
Scientific Score
0.39
Brand
Cell Biolabs
Sizes
1 (20 Reactions)
Available From
1 Vendor
Price
$ 701.54
Catalog IDs
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Total Protein Kit, Micro
Scientific Score
3.04
Brand
Sigma-Aldrich
Sizes
1 (1 kU)
Available From
2 Vendors
Price Range
$ 207.00 - $ 300.70
Catalog IDs
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Brand
Sigma-Aldrich
Sizes
1 (1 kU)
Available From
1 Vendor
Price
$ 91.10
Catalog IDs
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Brand
Sigma-Aldrich
Sizes
1 (1 kU)
Available From
2 Vendors
Price Range
$ 182.00 - $ 266.77
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Picrylsulfonic acid solution SKU : P2297
Control Type
/
Quantification Method
/
Sample Type
/
Scientific Score
6.01
Brand
Sigma-Aldrich
Sizes
2 (10 - 50 ml)
Available From
2 Vendors
Price Range
$ 76.50 - $ 460.34
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LabChip® HT Protein Express Chip
Scientific Score
4.17
Brand
Perkin Elmer
Sizes
1 (1 Chip)
Available From
1 Vendor
Price
$ 687.00
Catalog IDs
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Brand
Perkin Elmer
Sizes
1 (25 ml)
Available From
1 Vendor
Price
$ 58.00
Catalog IDs
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Brand
Perkin Elmer
Sizes
1 (1 Unit)
Available From
1 Vendor
Price
$ 994.00
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Quantifying Protein in a Sample

Quantification of protein concentration is a necessary first step during any protein analysis. There are various detection methods to achieve this, ranging from simple UV absorbance measurements (as amino acids exhibit strong UV-light absorption), to HPLC. However, the more cost effective technique is through the use of simple colorimetric assays.

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The Bradford method

One technique to determine protein concentration and the amount of sample is the Bradford method. Its principle: negatively charged Coomassie® Blue dye binds to positively charged proteins. When no proteins are present in the sample, the dye absorbs at 465 nm and has a red color. However, when proteins are introduced, the color changes to blue and absorbs at 595 nm. This absorption can then be cross-referenced to a standard curve. However, Bradford assays are often inhibited by detergents and can be difficult to read at certain concentrations. Thus, the method for protein quantification used will have to be curtailed to your experimental needs.

Our Bradford Assay Troubleshoot will help solve any issues you encounter.

BCA Protein Assay

The BCA Protein Assay uses bicinchoninic acid (BCA) to colorimetrically detect the color change produced by the cuprous cation (Cu1+), which results from the reduction of Cu2+ to Cu1+ by protein in an alkaline medium.

In the biuret reaction, copper chelates with protein in an alkaline solution to form a light blue complex; peptides with three or more amino acid residues form a chelate complex with cupric ions in the presence of sodium potassium tartrate.

Two molecules of BCA then chelate with one reduced cuprous cation to form an intense purple-colored product. The BCA/copper complex is water-soluble; producing a strong absorbance at 562 nm, proportional to protein concentration. The BCA reagent is 100 times more sensitive than the original pale blue color.

The reaction that leads to BCA color formation is strongly influenced by four amino acid residues (cysteine, tyrosine, and tryptophan). However, the peptide backbone also contributes to color formation, minimizing variability caused by differences in protein composition.

Lowry Assay

The Lowry protein assay uses cupric sulfate and tartrate in an alkaline solution, which forms tetradentate copper protein complexes when protein is added. Folin-Ciocalteu Reagent is reduced proportionally to these chelated copper complexes, producing a blue water-soluble product which can be measured at 750nm.

Compare Bradford Assay Products!

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The ZAGENO comparison engine does not show the best kit, but instead helps you, the researcher, choose the most sutiable kit for your experiment.

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