How to Measure Protein Purity: Minimum Protein Required from Sample to Result

Proteins are one of the most fundamental molecules in life forms, playing vital biological functions within cells. Therefore, studying the purity and structure of proteins is crucial to understanding the basic principles of life systems. In the field of biological drugs, determining the purity of proteins is critical as it directly impacts the quality and efficacy of the drug.

 

Definition of Protein Purity

Protein purity refers to the proportion of proteins in a sample. The higher the protein purity, the better the quality and efficacy of the drug. Therefore, determining protein purity is a significant step in the research and production process of drugs.

 

Methods for Determining Protein Purity

There are many methods to determine protein purity, including colorimetry, gel electrophoresis, and high-performance liquid chromatography. The following will introduce colorimetry and gel electrophoresis.

 

1. Colorimetry

Colorimetry is a simple, fast, and sensitive method for determining protein purity. It uses the color change caused by the reaction of proteins with certain chemical reagents to measure the protein content. Commonly used reagents include Bradford reagents, colorimetric reagent kits, etc. The steps of colorimetry are as follows:

 

(1) Prepare a Standard Curve: Add different concentrations of protein standards to the test tube, add the colorimetric reagent, mix and measure the absorbance to obtain a standard curve.

(2) Take the Sample to be Tested: Add the sample to be tested into the test tube, add the colorimetric reagent, mix and measure the absorbance.

(3) Calculate Protein Content: Calculate the protein content based on the standard curve and the absorbance of the sample to be tested.

 

2. Gel Electrophoresis

Gel electrophoresis is a common method for separating proteins. It can separate proteins by size and charge. Gel electrophoresis can be used to determine the molecular weight and purity of proteins. The steps of gel electrophoresis are as follows:

 

(1) Prepare the Gel: Mix polyacrylamide and crosslinker to make a gel.

(2) Load the Sample: Add the sample to be tested to the gel wells.

(3) Electrophoresis: Put the gel into the electrophoresis tank, add electrolyte, and separate proteins by electrifying.

(4) Staining: Stain the gel using silver staining or Coomassie staining.

(5) Analysis: Determine the molecular weight and purity of proteins by analyzing the size and color of the gel bands.

 

Minimum Protein Amount Needed from Sample to Result

In determining protein purity, the minimum protein amount needed from the sample to the result is crucial. If the protein content in the sample is too low, it may lead to inaccuracies in the determination result. Therefore, it is necessary to determine the minimum protein amount to ensure the accuracy of the determination results. Determining the minimum protein amount needs to consider the following factors:

 

(1) Determination Method: Different determination methods have different requirements for protein content.

(2) Instrument Sensitivity: Different instruments have different sensitivities and thus require different protein contents.

(3) Sample Type: Different types of samples contain different amounts of proteins, and the minimum protein amount should be determined based on the sample type.

Generally, the minimum protein amount should be around 10% of the protein content in the sample. For example, if the protein content in the sample is 1mg/ml, then the minimum protein amount should be 0.1mg/ml.

 

Determining protein purity is a vital step in the research and production process of biological drugs. Colorimetry and gel electrophoresis are commonly used methods for determining protein purity. In determining protein purity, it is necessary to determine the minimum protein amount from the sample to the result to ensure the accuracy of the determination results.