I purified a small protein using HPLC on an acetonitrile (+0.1% TFA) gradient. I then lyophilized the HPLC fraction and resuspended the freeze-dried sample in sodium acetate, potassium nitrate, and a little bit of acetonitrile. I wanted to measure the concentration of my protein in this solution so I used Nanodrop photospectrometry. I noticed a shift in the maximum absorbance. Normally with nanodrop, we would measure absorbance at 280nm (absorbance of aromatic side-chains Y and W), but the peak absorbance was actually at around 305 nm... What might cause this bathochromic shift?
Please look at the following below links which may help you in your analysis:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3489099/pdf/d-68-01088.pdf
https://www.sciencedirect.com/topics/chemistry/bathochromic-effect
Thanks
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