Hi there,

I don't think BSA exhibits any specific absorption properties at 540nm...

Dear Jackson,

. Sensitivity of the assay

when measurements are made at 540 nm can be described as 1.67 absorbance units per mg/mL. For more details please see attached file.

Hoping this will be helpful,

Rafik

Hello,

Answer is zerro. BSA solution do not exhibit light absorption at visible diapason (540 nm=blue-green solution).

Dear Dominique Liger,

You read at 540 nm after complexation to give color which absorbs at 540nm.

Please see attached file.

Rafik

Dears,

Please read the following text:

Results and Discussion

The 280 nm absorbance versus protein

concentration curve for bovine plasma albumin is

shown in Figure 1. Sensitivity of the assay can be

described in terms of absorbance per mg/mL protein

in the sample from which the protein aliquot has been

taken. The sensitivity at 280 nm for this albumin

preparation is 0.64 absorbance units per mg/mL.

Other proteins which contain more tryptophan may

have sensitivity factors at 280 nm in the range of 2.0

or more absorbance units per mg/mL.

The standard curve obtained from the biuret

procedure is shown in Figure 2. A sensitivity of 0.93

absorbance units at 280 nm was observed for this

mixture of plasma albumin and globulins. For the

biuret assay, the sensitivity at 540 nm is 0.56

absorbance units per mg/mL protein calculated for

the protein sample from which the aliquot was

removed for biuret assav.

The standard curve obtained, using the "Lowry"

assay with bovine plasma albumin as described

above, is shown in Figure 3. Sensitivity of the assay

when measurements are made at 540 nm can be

described as 1.67 absorbance units per mg/mL. lf the

absorbance at 280 nm of the same sample is

measured, a sensitivity of 0.64 absorbance units per

mg/ml is observed, making the "Lowry" protein

assay approximately three times more sensitive than

the absorbance at 280 nm. lf the absorbance

measurements are made at 750 nm, the "Lowry"

procedure is approximately two times more sensitive

than when the chromophore is measured at 540 nm

file:///C:/Users/Rafik%20Karaman/Desktop/Bov.pdf

Rafik

Dear Rafik Karaman,

where are Lowry (or Bradford, or biuret) assay were mentioned in this question? Pure BSA do not absorb light at 540 nm.

Because the preparation of protein assay reagents can vary from batch to batch, it is a good practice to prepare a standard curve based on a series of known concentrations of the standard protein, in this case BSA, rather than rely on an extinction coefficient. The stock solution of BSA from which the standards are diluted should be made by weighing solid BSA and dissolving it in water, or using a commercially prepared stock solution.

Thanks alot for your contributions.

Dear Jackson,

Would you please write your question in detailed manner?

Did you mean Lowry assay at 540 nm?

Thanks,

Rafik

No Rafik, foremost thanks for your sound contributions. Am simply requesting to know what is the coefficient extinction of BSA when it complexes with Biuret's reagent to yield an absorbance?

To "Mister thumb down", Biuret (or whatever coloration) was not mentioned in the question when I first replied...