Protein quantification

The most widely used method for protein quantification is by spectrophotometry. The concentration of the protein in the samples is measured at an absorbance of 280 nm. The absorbance of the sample protein is then plotted against a standard curve. This method allows for total protein quantification in a sample (cell and tissue extracts). Before analysing the concentration of protein in the sample, it is important to choose the right test method.  For high protein concentration samples (above 5 - 160 mg/ml) the best method is to use the Biuret test. For low concentrations samples (between 1 - 2000µg/ml) the best methods are Lowry assay, BCA assay, Bradford assay and coomassie blue (for exact sensitivity of the test kits you use, refer to manufacturer's protocol). If the samples contain detergents like Triton X-100 then BCA assay is the best choice. For samples that have proteins larger than 3 KDa in size Bradford assay is the best choice. Each method has advantages and disadvantages, plan your analysis considering your sample characteristics.

The most widely used method for protein quantification is by spectrophotometry. The concentration of the protein in the samples is measured at an absorbance of 280 nm. The absorbance of the sample protein is then plotted against a standard curve. This method allows for total protein quantification in a sample (cell and tissue extracts). Before analysing the concentration of protein in the sample, it is important to choose the right test method.  For high protein concentration samples (above 5 - 160 mg/ml) the best method is to use the Biuret test. For low concentrations samples (between 1 - 2000µg/ml) the best methods are Lowry assay, BCA assay, Bradford assay and coomassie blue (for exact sensitivity of the test kits you use, refer to manufacturer's protocol). If the samples contain detergents like Triton X-100 then BCA assay is the best choice. For samples that have proteins larger than 3 KDa in size Bradford assay is the best choice. Each method has advantages and disadvantages, plan your analysis considering your sample characteristics.

Though DNA quantification is but one small step in the multifaceted DNA sample preparation workflow, it can have large implications on the performance and validity of conclusions drawn from downstream assays. Major challenges include accuracy, precision, reproducibility, and detection of present contamination. Among UV spectrophotometry, fluorescence and real-time PCR based methods, the quantification method should be chosen based on the requirement of the downstream assay.

Though DNA quantification is but one small step in the multifaceted DNA sample preparation workflow, it can have large implications on the performance and validity of conclusions drawn from downstream assays. Major challenges include accuracy, precision, reproducibility, and detection of present contamination. Among UV spectrophotometry, fluorescence and real-time PCR based methods, the quantification method should be chosen based on the requirement of the downstream assay.

Though DNA quantification is but one small step in the multifaceted DNA sample preparation workflow, it can have large implications on the performance and validity of conclusions drawn from downstream assays. Major challenges include accuracy, precision, reproducibility, and detection of present contamination. Among UV spectrophotometry, fluorescence and real-time PCR based methods, the quantification method should be chosen based on the requirement of the downstream assay.

Though DNA quantification is but one small step in the multifaceted DNA sample preparation workflow, it can have large implications on the performance and validity of conclusions drawn from downstream assays. Major challenges include accuracy, precision, reproducibility, and detection of present contamination. Among UV spectrophotometry, fluorescence and real-time PCR based methods, the quantification method should be chosen based on the requirement of the downstream assay.

Though DNA quantification is but one small step in the multifaceted DNA sample preparation workflow, it can have large implications on the performance and validity of conclusions drawn from downstream assays. Major challenges include accuracy, precision, reproducibility, and detection of present contamination. Among UV spectrophotometry, fluorescence and real-time PCR based methods, the quantification method should be chosen based on the requirement of the downstream assay.

Though DNA quantification is but one small step in the multifaceted DNA sample preparation workflow, it can have large implications on the performance and validity of conclusions drawn from downstream assays. Major challenges include accuracy, precision, reproducibility, and detection of present contamination. Among UV spectrophotometry, fluorescence and real-time PCR based methods, the quantification method should be chosen based on the requirement of the downstream assay.

RNA quantification for appropriate concentration and quality (260/280 ratio) is an important step before downstream analysis (including sequencing, RT-qPCR, etc.). Having insufficient RNA quantities or a high salt or phenol in the RNA product can lead to variable or irreproducible downstream results. The various methods used for RNA quantification include: 1. UV spectrophotometric (challenges include: low sensitivity, cannot distinguish between nucleic acid species), 2. Fluorescence-based (challenges include: requires standards, cannot measure amplifiability, not sequence-specific), and 3. RT-PCR (challenges include: requires standards, time-intensive, costly). In order to overcome these challenges, and also to ensure the proper quantification and quality control for RNA product, it is important to use at least two or more methods in order to discard any inconsistencies. Using standards for calibrations increases the sensitivity range for RNA detention (fluorescence- and RT-PCR-based methods). When using RT- PCR, it is important to choose correct primers, aligning to the desired site on the template and of appropriate product length, along with positive, negative and loading controls. It is also important to have at least two primer pairs in order to confirm results.

RNA quantification for appropriate concentration and quality (260/280 ratio) is an important step before downstream analysis (including sequencing, RT-qPCR, etc.). Having insufficient RNA quantities or a high salt or phenol in the RNA product can lead to variable or irreproducible downstream results. The various methods used for RNA quantification include: 1. UV spectrophotometric (challenges include: low sensitivity, cannot distinguish between nucleic acid species), 2. Fluorescence-based (challenges include: requires standards, cannot measure amplifiability, not sequence-specific), and 3. RT-PCR (challenges include: requires standards, time-intensive, costly). In order to overcome these challenges, and also to ensure the proper quantification and quality control for RNA product, it is important to use at least two or more methods in order to discard any inconsistencies. Using standards for calibrations increases the sensitivity range for RNA detention (fluorescence- and RT-PCR-based methods). When using RT- PCR, it is important to choose correct primers, aligning to the desired site on the template and of appropriate product length, along with positive, negative and loading controls. It is also important to have at least two primer pairs in order to confirm results.