[evidenso]

Hello
How can a protein be damaged when interacting with light. Can anyone explain what happens in the UV, visible and especially in the Near Infrared? Does it trigger reactions? can it disintegrate when warmed up and so on.... anyone who knows anything of protein stability and light? 

I am physician who is doing NIR Raman spectroscopies of proteins. Anyone who has any excperience?

[Procyan]

UV can break peptide bonds.  Also 3 amino acids absorb UV and they may also be damaged depending on the intensity.  I am not aware of Visible or NIR causing damage.  Depends partly on how long and how intense as well as wavelength, right?

Other possible levels of damage are possible.  Loss of higher orders of structure may result from heating.  Enzymes may denature leaving intact amino acid sequence (primary structure) but loss of quaternary or tertiary structure (unfolding) with consequent loss of activity. 

Moreover, non-covalently bound cofactors may be displaced by vibrational modes etc. 

Finally, I would consider other molecules like transition metals that can catalyze crosslinking between sulfhydryl groups.  These reactions could be accelerated by NIR, but I'm not sure about that.

Is there a change in spectra with time?

Interesting question.

[evidenso]

Ok thanks.... I will study those subject at write what I finds out.

just another question concerning fluorenscence:
First i used 532 excitation (the protein was fluorescent)
Now I am using 785 excitation and exsperience some fluorescence (not much). How can this be? The absorbtion spectrum shows no visible electronic transitions either at 532nm or 785nm. It's not impurities as it is sterile sample! Is it due to flourephores that I'm not aware of which cant be seen in absorbtion spectra?
I know that its typical that biological sample emit flourescence at 785nm excitation. Is it typical to have electronic states at these energies?