I am doing fluorescence experiment of protein solution, but the problem is that the same solution gives different maximum emission value a day after the previous one.
Is it possible that the protein undergo some sort of denaturation/structural or conformational change during the course of time? As you know tryptophan emission is quite sensitive to local environment a change in local environment by any process could lead to spectral changes.
(Please give more information when you request a suggestion so that a specific answer may be provided. What is your fluorophore, how much is the change is spectra (show the spectra), how many times you have repeated the experiment, etc)
I am using HSA solution in phosphate buffer of 7.4 pH. Day 1 it gives a maximum emission of 103 (a.u) at 343 nm and on third day it gives maximum emission of 114 (a.u) at 343 nm. I am just curious if that is possible or there is some kind of error in the experiment.
Those two numbers are pretty similar. It could just be due to random variation. Try measuring the same sample several times to see the variation.
There is no problem with your sample or experiment. unlike absorbance which is a ratiometric parameter and remains constant, fluorescence intensity depends on lot of factors, one of which is lamp condition. So a slight variation of fluorescence intensity is ok. See your emission maximum (343 nm) is not changing that is what is important and says that your sample is ok.
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