Greetings and Regards
I calculated the bacteriorhodopsin concentration in Halobacterium salinarum as described by Shand and Betlach.
But I have a question: why does bacteriorhodopsin lose its color in the presence of light?
What happens to it?
Thanks for your reply
Hi Sahar,
It really depends on conditions. Normally, it should not lose color (if in membrane). In some detergents, it may. In some cases it simply loses retinal and becomes colorless (bleaches). Under some other conditions it can become yellow temporarily, as the retinal Schiff base deprotonates, and can slowly recover in the dark and/or under lower pH. Can't answer for your specific case without knowing the conditions.
Leonid S Brown thank you very much
The process was as follows:
The cells were first separated from the culture medium by centrifugation, then NH2OH and NaOH were added to the pellets and mixed well.
The optical density of the suspension was recorded at 568 nm to measure the bacteriorhodopsin concentration.
Then it was exposed to light and after 24 hours of bleaching, its optical density was recorded.
So the reason for bleaching is retinal release or its deprotonation?
In this case, is the retinal destroyed or just released?
And does it have the ability to protonate and return its color in this case?
Thank You
Ok, Sahar, now I understand what you did. You used hydroxylamine bleaching, the classical procedure. In this case, you destroy the Schiff base linkage and form retinaloxime. And the latter is colorless. BUT, it stays in the pocket, and in a few days can slowly start reforming retinal Schiff base. If you want to prevent it, you may need to wash with BSA. Good luck
The following research papers may be helpful to find detail:
1.Mechanism of colour discrimination by a bacterial sensory rhodopsin https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4996264/
2.Bleaching of bacteriorhodopsin by continuous light https://febs.onlinelibrary.wiley.com/doi/full/10.1016/s0014-5793(99)00487-1
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