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Hi all,
 
One of our researchers has been attempting to use a GFP-based reporter
gene microtitre plate assay to test the efficacy of a variety of
bioactive test compounds.  They've had no problem with the assay itself
(controls and other compounds provide anticipated readouts).  They did
however notice that one of these test compounds, an 80% pure beta-glucan
suspension extracted from an undisclosed yeast source, displayed
significant concentration-dependent fluorescence that overlapped the
emission range of GFP even when measured in the absence of cells.   So
far we haven't been able to find any reference in the literature to
suggest that fungal beta-glucans typically exhibit significant
fluorescence in this range.  On the contrary, beta-glucans more commonly
seem to require fluorescent labeling to be seen (e.g., Toyotome et al,
Microbial Pathogenesis (2008); 44(2) 141-150).  The closest that I've
come to an answer is a reference suggesting that polyphenolics, chitin,
or plasmalemma components from the cell walls of mycorrhizal fungi could
be a potential source of green/yellow fluorescence (Dreyer et al,
mycological  research 110 (2006) 887- 897).  Has anyone run into this
situation and/or have any additional references to suggest why this
yeast extract could be fluorescing?  
 
Thanks
 
Aleks Spurmanis
Fluorescence Core Facility Manager
National Research Council of Canada
Institute for Nutrisciences and Health
550 University Avenue INH Building
Room 324
Charlottetown PE
C1A 4P3
tel:  (902)- 566-7557
fax: (902) - 367-7539
e-mail:  [log in to unmask]