Hi all,
I was recently trying to calculate the concentration of amyloid beta concentration from the UV-Vis result. I found that it can be calculated based on absorbance at ~280nm with an extinction coefficient of 1490 M-1 cm-1. However, I did not observe such a peak in my sample at 280nm. Instead, there is a peak at 230nm (which should be the absorbance of the peptide?) I am wondering if I still could do the calculation based on this figure.
Any reply would be appreciated. Many thanks.
If your matrix is complex (you have more things other than beta-amyloid in water, as it seems from the spectra) you would need to do a proper calibration first. You can not assume that the only thing that is absorbing at 280 nm is beta-amyloid even if the extinction coefficient is correct. So the short answer is no. Otherwise, if you have available the matrix without the beta-amyloid (this is, all the things in your sample before having the beta-amyloid) you could do a blank spectrum with that and assume you can use the coefficient. As a hard-work answer: you could measure several samples by UV-Vis and by a reference method in order to build a univariate (or multivariate) regression model and use it for then on.
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