No

You can try a nanodrop, if available. You can make BCA assay or other in your lab, no need to buy commercially available reagents.

There are many protein assay methods, but other than A280, they all require the use of reagents. In the past, people have suggested using UV fluorescence of some proteins, but quenching seems to have been a problem. (See attached paper).

Thank you all for your sincere contributions. Nanodrop is not available. Maybe i will keep trying the use of A280 and finally resolve to the use of Kjedahl method if the results obtained are still unsatisfactory.

A nanodrop is a spectrophotometer, thus it is not different from what you are doing.

Before using the Kjeldahl method, which is tedious, you might consider one of the colorimetric methods. (See attachments)

Thank you Omar Gonzalez-Ortega. Dear Greg Cote, am very grateful for your contribution. I will check through those methods.

.....but all these methods involve the use of some reagent, just like the Bradford assay also.....

The Lowry and Bradford protein assay techniques work pretty good for low protein concentrations, downside is that you require reagents for them.

Thank you dear Barbara Ferrari and Tome Nestorovski for your contributions.

Hallo,

Please find the attach file about Protein Concentration Determination by Spectrophotometer

Thank you Dear Mohamed Gadallah for your contribution.

The most straightforward psectrophotometric method for quantitating protein content in biological samples is the Bradford method (Article A rapid and sensitive method for quantitation of microgram q...

Thank you Dr Marios Kyriacou for your response.

Please see this Article:

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Quantifying protein using absorbance at 280 nm

Considerations for use

Quantifying protein by directly measuring absorbance is fast and convenient, since no additional reagents or incubations are required. No protein standard need be prepared and the procedure does not consume the protein. The relationship of absorbance to protein concentration is linear. Because different proteins and nucleic acids have widely varying absorption characteristics there may be considerable error, especially for unknowns or protein mixtures. Any non-protein component of the solution that absorbs ultraviolet light will intefere with the measurements. Cell and tissue fractionation samples often contain insoluble or colored components that interfere. The most common use for this method is to monitor fractions from chromatography columns, or any time a quick estimation is needed and error in protein concentration is not a concern. This method is recommended for calibrating bovine serum albumin or other pure protein solutions for use as standards in other methods.

Principle

Proteins in solution absorb ultraviolet light with absorbance maxima at 280 and 200 nm. Amino acids with aromatic rings are the primary reason for the absorbance peak at 280 nm. Peptide bonds are primarily responsible for the peak at 200 nm. Secondary, tertiary, and quaternary structure all affect absorbance, therefore factors such as pH, ionic strength, etc. can alter the absorbance spectrum.

Equipment

In addition to standard liquid handling supplies a spectrophotometer with UV lamp and quartz cuvette are required.

Procedure

Carry out steps 1-4 (280 nm only) for a very rough estimate. Carry out all steps if nucleic acid contamination is likely.

Analysis

Unknown proteins or protein mixtures. Use the following formula to roughly estimate protein concentration. Path length for most spectrometers is 1 cm.

Concentration (mg/ml) = Absorbance at 280 nm divided by path length (cm.)

Pure protein of known absorbance coefficient. Use the following formula for a path length of 1 cm. Concentration is in mg/ml, %, or molarity depending on which type coefficient is used.

concentration = Absorbance at 280 nm divided by absorbance coefficient

To convert units, use these relationships:

Mg protein/ml = % protein divided by 10 = molarity divided by protein molecular weight

Unknowns with possible nucleic acid contamination. Use the following formula to estimate protein concentration:

Concentration (mg/ml) = (1.55 x A280) - 0.76 x A260)