Protein Content Determination by Lowry Method Standard Curve

The Lowry method, also known as the Lowry method, is a commonly used biochemical analytical method for determining total protein content. The method was proposed by Oliver H. Lowry et al. in 1951. It is based on the absorbance of the complex produced by the reaction of protein with phenol and copper ions at a specific wavelength, thereby calculating the concentration of the protein.

 

The Lowry method is based on the principle that the aromatic ketone peptide bond of protein forms a colored complex with phenolic oxygen and copper ions. This complex has an absorbance at 750 nm proportional to protein concentration. This is an analytical method based on the Beer-Lambert law.

 

Standard Curve Preparation

In the laboratory, we usually use a protein solution of known concentration (such as bovine serum albumin BSA) as a standard to prepare a series of standard solutions with different concentrations, and then measure their absorbance to make a standard curve.

 

1. Dilute the BSA solution of known concentration proportionately to prepare a series of standard solutions. The concentration is usually selected within the experimental measurement range, such as 0.1, 0.2, 0.4, 0.6, 0.8, 1.0 mg/ml, etc.

2. Mix each standard solution with Folin phenol reagent, and let it sit for a while to react evenly.

3. Measure the absorbance of each standard solution at 750 nm.

4. Make a standard curve with absorbance as the ordinate and concentration as the abscissa.

 

In the experiment, we generally assume that the relationship between absorbance and concentration is linear. However, this relationship may deviate from linearity in cases of excessively high or low concentration. Therefore, it is necessary to select an appropriate concentration range to ensure the accuracy of the measurement. The Lowry method is a common and important method for determining total protein content. By making a standard curve, we can accurately and quickly determine the protein solution of unknown concentration. The Lowry method has a wide range of applications in biochemistry, molecular biology, immunology, and other fields.