LOL Mike
But Luke skywalker only existed in a Galaxy far far away and long ago
even if he did have lots of possibilities in his mitochlorians -or so
we are told...
Cheers
Ignatius, Mike wrote:
> Boy, now I am really glad I didn't share my Luke Skywalker, avoid the
> Dark Side/State analogy, that I use with students. When Luke/Fluors are
> activated, riled with hate, they are most vulnerable to going to the
> dark side/state.
>
> Yoda: "But beware of the dark side. Anger, fear, aggression,
> PHOTOTOXICITY, SIGNAL LOSS, the dark side of the Force are they."
> Luke: "Is the dark side stronger?"
> Yoda: "No, no, no. Quicker, easier, more seductive, HARDER TO PREVENT IN
> LIVE CELLS."
>
> Anakin
>
> -----Original Message-----
> From: Confocal Microscopy List [mailto:[log in to unmask]]
> On Behalf Of Mark Cannell
> Sent: Monday, February 16, 2009 1:03 PM
> To: [log in to unmask]
> Subject: Re: Photobleaching mechanism question
>
> While I am all for analogies to convey the basis of complicated
> processes to the ignorant, the analogy must be accurate. But in this
> case, if a _scientist_ asks about bleaching from the triplet state why
> does the explanation have to be dumbed down to such an (inaccurate)
> level? Surely the basis of chemical reactions in terms of electrons and
>
> electron pairing should not be so unfamiliar after undergraduate physics
>
> and chemistry?
>
> A good explanation is given in Encyclopeda Britannica and should be
> within the grasp of most I think.
>
> http://www.britannica.com/EBchecked/topic/457736/photochemical-reaction/
> 277509/Consequences-of-photoexcitation#ref=ref499215
>
> Even if you can't remember the simple reason for more rapid oxidation
> from the excited state (due to singlet oxygen production, I think, but
> probably other possibilities also exist in complex molecular systems),
> you point your undergraduates there rather than use horribly inaccurate
> analogies. If nothing else, a reason to learn this explanation is that
> it is the basis of life on earth as it explains how light can be
> harnessed to chemical reactions!
>
> Cheers Mark
> P.S. Tobias, if you wonder why I object to your analogy it is because a
> power surge does not involve switching off the computer!!!!
>
>
>
>> John,
>> From the non physicist's point of view the answer could go
>> something like this. If you have a power surge it can fry your
>> computer. But if your computer is not plugged into the mains then it
>> would take a very big power surge indeed to do the damage. A molecule
>> in the ground state can of course be damaged by free radical attack
>> but no more or less than other molecules. But once a molecule has
>> absorbed a photon then it is not in the ground state any more. To
>> continue my hoaky analogy, a chromophore in light is like your
>> computer plugged in to the mains.
>>
>> Hope this helps. The physicists (and musicians) can go for the
>> triplets.
>>
>> Tobias
>>
>>
>>
>>> Hi Everyone, this question follows on from a helpful discussion that
>>>
>
>
>>> we had about photobleaching back in November. I have recently tried
>>> to explain to a group of colleagues about the mechanism of
>>> photobleaching. The answer is based on the transition of molecules
>>> from the excited singlet state (S1) to the triplet state (T1) which
>>> is long-lived and therefore more susceptible to bleaching by free
>>> radicals (my entire discussion of this is below).
>>>
>>> My question that arises from my attempted answer is: why are excited
>>> molecules more susceptible to oxidative attack than ground state
>>> molecules. I hope I'm not completely mucking up the mechanism here.
>>> Would the physicists out there please help.
>>>
>>> Thanks, John.
>>>
>>> The original answer: When excited, fluorophores generally transition
>>> from singlet ground state (S0) to singlet excited state (S1).
>>> Relaxation from S1 to S0 results in emission of heat and light
>>> (fluorescence). Lifetime in S1 is in the nano to pico second range
>>> and allows very little time for the excited molecule to interact with
>>>
>
>
>>> free radicals. Periodically, however, an excited molecule will do a
>>> transition from S1 to the triplet excited state (T1 - the physics of
>>> this is a bit difficult to understand). T1 is a very long-lived state
>>>
>
>
>>> - molecules can remain in T1 for up to the microsecond range - i.e. a
>>>
>
>
>>> thousand to a million times longer than for normal S1 state. It is
>>> during this long T1 state that molecules are attacked by free
>>> radicals and destroyed.
>>>
>>> --
>>> Runions signature
>>>
>>> (Sent from my cra%#y non-Blackberry electronic device that still has
>>> wires)
>>>
>>>
>>>
>>> *********************************
>>> John Runions, Ph.D.
>>> School of Life Sciences
>>> Oxford Brookes University
>>> Oxford, UK
>>> OX3 0BP
>>>
>>> email: <mailto:[log in to unmask]>[log in to unmask]
>>> phone: +44 (0) 1865 483 964
>>>
>>>
>>>
> <http://www.brookes.ac.uk/lifesci/runions/HTMLpages/index.html%21>Runion
> s'
>
>>> lab web site
>>>
>>>
>>>
>>> Visit <http://www.illuminatedcell.com/ER.html>The Illuminated Plant
>>> Cell dot com
>>> Oxford Brookes Master's in
>>>
>>>
> <http://www.brookes.ac.uk/studying/courses/postgraduate/2007/bmt>Bioimag
> ing
>
>>> with Molecular Technology
>>>
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