Protein assay sensitive at nanogram levels.

Area of Science:

• Biochemistry
• Analytical Chemistry

Background:

• Accurate protein quantification is essential for various biological and chemical applications.
• Existing protein assays may suffer from interference or require complex procedures.

Purpose of the Study:

• To describe a simple, rapid, and sensitive protein assay utilizing colloidal gold's affinity for proteins.
• To evaluate the assay's sensitivity and identify potential interfering substances.

Main Methods:

• Development of a protein assay based on the interaction between proteins and colloidal gold.
• Quantification of protein concentration using a visible light spectrophotometer to measure absorbance.
• Testing the effect of various chemical reagents on assay performance.

Main Results:

• The assay demonstrates sensitivity at the 20-nanogram (ng) level.
• Strongly alkaline solutions, high salt concentrations, and sodium dodecyl sulfate (SDS) were identified as interfering agents.
• Alkaline interference can be mitigated by acidifying the protein solution prior to the assay.
• Variability in protein interaction with colloidal gold is comparable to the Bradford protein assay.

Conclusions:

• The described colloidal gold protein assay is a simple, fast, and sensitive method for protein quantification.
• The assay is robust, with manageable interference from common laboratory reagents.
• This method provides a viable alternative to existing protein assays, particularly when speed and simplicity are prioritized.