Protein quantification is divided into "total quantification method" of whole protein and "individual quantification method" of specific protein according to its purpose. It is an indispensable part of biological experiments.

1. Your Guide to Protein
Quantitation
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2. Protein quantification is divided into "total quantification method" of whole protein
and "individual quantification method" of specific protein according to its purpose. It is
an indispensable part of biological experiments. In order to verify the success of cell
lysis, or to compare or standardize multiple samples for parallel experiments, protein
cytolysis should be performed for protein quantification; in order to determine protein
yield, the purified protein should be quantified; In order to label the purified protein
with biotin or reporter enzyme, the protein sample should also be quantified to ensure
that the labeling reaction is carried out at the appropriate chemical concentration.
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3. Quantitative analysis of proteins is an area of analysis often involved in biochemistry
and other life sciences. Accurate and reliable quantitative analysis of proteins in
samples is a very important task in biochemical experiments. Protein is a very
important biological macromolecule. It has many kinds of structures, heterogeneous
structure, large molecular weight and different functions. This brings a lot of concrete
difficulties for the establishment of an ideal and versatile method for quantitative
protein analysis.
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4. There are many methods for
determining protein content.
• According to physical properties: UV spectrophotometry
• According to chemical properties: Kjeldahl method, biuret
method, Folin-phenol reagent method (Lowry method), BCA
method, colloidal gold method.
• According to the nature of dyeing: Coomassie blue staining,
silver staining.
• According to other properties: fluorescence method.
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5. Protein quantitative analysis is also involved in many fields and industries of production
research, and is the most common method in biology, food testing and adulteration,
clinical testing, diagnosis of diseases and quality testing.
There are many methods for protein quantification, five of which are more common,
namely Bradford method, Bradford spot test, Coomassie spot test, ultraviolet
spectrophotometry and BCA method. Of course, the conditions for each method are
different.
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6. Bradford method
This method is quite accurate for most protein quantification, especially for
small molecule polypeptide quantification. Such as ribonuclease or lysozyme.
However, a concentration of the detergent exceeding 0.2% affects the
quantitative results. Such as TritonX-100, SDS, NP-40 and so on.
Bradford spot test
This method is particularly useful for detecting elution components to
localize protein eluates. For example, the strength of the adsorption force of
the eluate is detected.
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7. Coomassie spot test
This method is particularly useful for detecting elution components to
localize protein eluates. For example, the strength of the adsorption force of
the eluate is detected.
Ultraviolet spectrophotometry
Protein UV absorbance is the fastest of all protein quantification methods.
Readings are typically taken at 280 nm light wavelength. Its maximum
absorbance at 280 nm light wavelength is mainly determined by the
presence of tyrosine and tryptophan. Absorption at the wavelength of 205
nm light is also commonly used. Its maximum absorbance at 205 nm light
wavelength is mainly determined by the peptide chain, although amino
acids also have an effect. In addition, one major advantage is that the
sample is not damaged when the protein concentration is determined.
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8. BCA method
Characteristics of BCA method: 1. High sensitivity, the lower limit of
detection concentration reaches 25μg/ml, the minimum detection protein
amount reaches 0.5μg, and the sample volume to be tested is 1-20μl. 2.
Determination of protein concentration is not affected by chemicals such as
detergents in most samples, and can be compatible with up to 5% SDS in
samples, 5% Triton X-100, 5% Tween 20, 60, 80. 3. There is a good linear
relationship in the concentration range of 20-2000 μg/ml. 4. The coefficient
of variation of different protein molecules is much smaller than that of
Coomassie Brilliant Blue. 5. Effect of chelating agent and slightly higher
concentration of reducing agent: EDTA is less than 10 mM. DTT is less than 1
mM, and mercaptoethanol below 1 mm.
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9. Collected by Creative BioMart.
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