Can retinal emit as well as absorb photons?

  • Thread starter Thread starter Yamayama
  • Start date Start date
  • Tags Tags
    Photons
Click For Summary

Discussion Overview

The discussion centers on whether retinal can emit photons as well as absorb them, particularly in the context of rhodopsin regeneration. Participants explore the biochemical processes involved and the implications of light emission related to retinal's conformational changes.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant suggests that the isomerization of retinal from 11-cis-retinal to all-trans-retinal corresponds to photon absorption, while the reverse process may correspond to photon emission, questioning why this emission isn't observed.
  • Another participant speculates that non-emitting relaxation processes may dominate, implying that while light absorption and emission are theoretically possible, emission may not be significant.
  • A later reply acknowledges the complexity of rhodopsin regeneration and suggests that the emitted photon’s energy might not be in the visible range, potentially being infrared instead.
  • References to scientific papers are provided, discussing light emission from rhodopsin and the biochemical coupling of conformational changes to signaling cascades, indicating that the timing of energy transfer could affect photon emission.
  • One participant expresses difficulty accessing the referenced articles, indicating a need for alternative methods to obtain them.

Areas of Agreement / Disagreement

Participants do not reach a consensus on whether retinal emits photons during regeneration, with multiple competing views and uncertainties remaining about the processes involved.

Contextual Notes

The discussion highlights limitations in understanding the full biochemical mechanisms of rhodopsin regeneration and the conditions under which photon emission might occur.

Who May Find This Useful

This discussion may be of interest to those studying biochemistry, photobiology, or vision science, particularly in the context of retinal and rhodopsin functions.

Yamayama
Messages
3
Reaction score
0
Retinal: the molecules which absorb photons of light in the photoreceptors at the back of our eyes; they combine with an opsin molecule to form photopigments.

It seems to me that: just as isomerization of retinal from 11-cis-retinal to all-trans-retinal corresponds to the absorption of a photon, changing back from all-trans-retinol to 11-cis-retinol - which is a necessary step for rhodopsin regeneration - surely corresponds to the emission of a photon.

If my suspicion is correct, I guess the reason this isn't observed is because rhodopsin regeneration occurs in the RPE (retinal pigmented epithelium, which is high in melanin - fantastic for absorbing light).

Can anyone affirm/disaffirm my suspicions?
 
Biology news on Phys.org
Subjectively speaking, yes. Looking closely into one woman's eyes I once felt that way. It was the most intimate communication I had ever experienced in public. Her eyes were dilated, and I could see the heartbeat in her irises. But photons? More like epiphany.
 
While there are generally 2 ways any reaction can go, implying that anything that absorbs light can emit it, I bet the non-emitting relaxation processes are dominant.

Also, everything emits blackbody radiation, but that is trivial.

Njorl
 
Subjectively speaking, yes. Looking closely into one woman's eyes I once felt that way. It was the most intimate communication I had ever experienced in public. Her eyes were dilated, and I could see the heartbeat in her irises. But photons? More like epiphany.

hmmmm...nice anecdote...well, I was hoping more for an objective response, but hey...lucky you!

Njorl:
You're quite possibly right.

The events involved in rhodopsin regeneration are quite complex I expect, and I'm not sure they're even fully understood yet.

Also, it's just been pointed out to me that if a photon is emitted, its energy is not necessarily in the visible range, i.e. it could be infrared.
 
You might be interested in the following papers :approve:

Nature. 1976 Apr 22;260(5553):675-8.
Observation of light emission from a rhodopsin.
Lewis A, Spoonhower JP, Perreault GJ.
PMID: 1264238 [PubMed]

Photochem Photobiol. 1982 Mar;35(3):385-90.
Light-induced change in rhodopsin emission: phosphorescence and fluorescence.
Andley UP, Chakrabarti B.
PMID: 7063554 [PubMed]

I'm not sure how common light emission from rhodopsin is, since the conformational change from cis to trans is biochemically coupled to downstream signalling cascades. It would depend how soon the energy transfer to an electrical signal can happen when it it goes into trans, and how readily it is able to go back into cis with the emission of a photon.

You are right, the color absorped most by rhodopsin is purple, so it is to be expected that the emitted photon would be in the infrared (longer wavelength).
 
Thanks very much Monique,

I should have thought of searching PubMed myself of course. Anyway, unfortunately I can't seem to get those articles online, as issues that old aren't available in their online catalogs, but maybe I can figure out another way to get them.
Appreciate the help
 
Ask a librarian to fetch a copy for you, those issues are probably still standing in some library and they'll know where :)
 

Similar threads

Future Human: Making human's invisible without a suit
  • · Replies 16 ·
Replies
16
Views
22K
Graduate How a solid body emits a lower frequency photon than absorbed
  • · Replies 4 ·
Replies
4
Views
2K
What colors and attributes could alien flora & fauna have?
  • · Replies 15 ·
Replies
15
Views
7K