[Histonet] Re: mercury vs led lights **Commercial Response**

Mark Rand mark.rand <@t> amgmicro.com
Fri Sep 11 12:49:52 CDT 2009

Full disclosure: My company manufactures an LED fluorescence microscope :-) 

Merced's information from the Zeiss rep is partially correct and needs some clarification. There is a "gap" in the spectrum of available LED's from 530 to 590 nm that would be powerful enough for fluorescence excitation. However, there aren't many fluorophores in that range that can't be covered by either 530 or 590 nm excitation. In fact, the examples cited (Alexa Fluor 555, Cy3, and TRITC) work very nicely with the 530 nm LED used in our microscope's "RFP" light cube. And to provide a balanced reply, I should note that Zeiss offers a 530 nm LED fluorescence module, as do other companies (e.g., Leica, CoolLED, Fraen).  

There are some notable exceptions to 530 or 590 nm coverage -- for example, DsRed2 would greatly benefit from excitation in the 550-560 nm range. Manufacturers of LED-based fluorescence instrumentation keep a sharp eye out for new LED's that can fill in these gaps. In the meantime, having 7 dedicated LED modules does cover a very wide range of fluorescence applications, as noted by Eric in his message below.


-- Mark Rand

Mark Rand, Ph.D.
Product Manager and Senior Applications Scientist
Advanced Microscopy Group
Office: (425) 368-0413

> Regarding the LED light sources for fluorescent microscopy, we have been
> using one of these for the past six months, and it is wonderful.  The
> lighting is bright, even, and it doesn't quench (photobleach) FITC as fast
> as mercury lamps do.  It is easy to align, and the expected life of the LEDs
> is at least 10,000 hours.
> I used mercury lamps for many years, and they were fun for those of us who
> like to tinker with instruments, but overall, they are a pain in the neck to
> use every day.  About two years ago, we bought a new Nikon 50i microscope,
> which is one of the best clinical microscopes I have ever used.
> Unfortunately, the Nikon rep talked us into the EXFO metal halide light
> source.  This looked good in the demo, but it has spent more time being
> repaired than working in our lab.  Right now it is back at Nikon while they
> try to figure out what is wrong with it.
> The LED light source that we are currently using is from a company called
> Fraen.  They are an Italian company, but they have an office in the US.  The
> unit is small, easy to install, easy to align, and gives illumination
> equivalent to a 100 watt mercury lamp.
> Merced said that there are no LEDs available for red wavelengths, but this
> must just be true for Zeiss.  Fraen has LED modules that cover virtually all
> of the fluorochromes that I have ever heard of.  They have one for red
> wavelengths that will work with TRITC, Cy3, Texas Red, Alexa Fluor 633,
> Alexa Fluor 647, and even Cy5, which has maximum excitation at about 650 nm,
> well into the red range.
> You do need to have different LEDs for various fluorochromes, but Fraen has
> 7 modules available, and for practical terms, about 4 of them would cover
> everything from DAPI to Cy5.  They are easy to interchange on the Fraen
> unit.
> I don't work for any of the companies mentioned here, nor do I receive any
> compensation for saying nice things about their products.  I just like their
> products.
> Eric Hoy
> ===============================================
> Eric S. Hoy, Ph.D., SI(ASCP)
> Clinical Associate Professor
> Department of Medical Laboratory Sciences
> The University of Texas Southwestern Medical Center
> Dallas, Texas
> Email: Eric.Hoy <@t> UTSouthwestern.edu
> ===============================================
> Message: 1
> Date: Wed, 09 Sep 2009 13:43:45 -0400
> From: Merced M Leiker <leiker <@t> buffalo.edu>
> Subject: Re: [Histonet] mercury vs led lights
> To: Nejat Yilmaz <nyilmaz <@t> mersin.edu.tr>,
> histonet <@t> lists.utsouthwestern.edu
> Message-ID: <6276F2A000238523BC2681F5 <@t> CDYwxp1931.ad.med.buffalo.edu>
> Content-Type: text/plain; charset=us-ascii; format=flowed
> I forgot to mention. An LED can be made to excite FITC, DAPI, and Cy5
> (far-red) fluorophores, but they cannot make them in the red (Alexa Fluor
> 555, Cy3, TRITC, etc.) This is per our Zeiss rep. So on our inverted
> microscope we have LEDs and we also have a mercury lamp to cover the red
> range. The Zeiss switches nicely and very smoothly between the light
> sources during viewing and image acquisition.
> Sorry for the highly untechnical description, but that is all I know about
> it.  :-)

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