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My understanding is that it is critical that all UV light be
removed/blocked as Hg bulbs produce lots of UV.  Diodes don't have this
concern. 

Not all scopes can claim 100% UV block produced by Hg or xenon bulbs.
But when it is done (for example AP/Delta Vision Scopes), cell viability
along with dye stability is greatly enhanced.

Mike Ignatius


-----Original Message-----
From: Confocal Microscopy List [mailto:[log in to unmask]] On
Behalf Of Mark Cannell
Sent: Tuesday, March 11, 2008 2:02 PM
To: [log in to unmask]
Subject: Re: Fluorophore bleaching by excitation light sources

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I don't understand this. The only explanation I can think of is that 
that the excitation wavelengths are _not_ the same in the two cases.(if 
they were and the power is the same the photon flux is the same).  Any 
other comments/views?

Regards.

Gerard Whoriskey wrote:
> Commercial interest.
>
> We have recently had preliminary feedback from a number of independent

> sources that show much reduced bleaching when a sample is excited
using an 
> LED source rather than a Hg bulb. These tests, carried out with
identical 
> powers in the excitation bandpass region, showed that imaging could be

> carried out for up to three times longer.
> On live tests cells were seen to be still living happily after being 
> exposed for twice the time it took to kill the cells under Hg
excitation. 
> We are still gathering information on this and intend to publish in
due 
> course. 
>