The most common COVID-19 testing protocols utilize fluorescence quenching assays and polymerase chain reaction (PCR). For example, in the TAQman assays (from Roche Diagnostics), there is fluorescence quenching (dark green circle) within the DNA-binding probe specific to a particular DNA sequence (dark blue). This probe can be specific to viral, bacterial or any other specific DNA sequence in a sample. As TAQ-polymerase (purple oval) replicates the single-stranded DNA (light blue), it encounters the labeled probe and cleaves the nucleotides off, releasing the fluorescent moiety (bright green circle).  When excited with blue light, this compound glows green. The fluorescence is proportional to the number of DNA sequences the probe finds in the sample. If the signal is too low after a single polymerization step, the sample can be heated to separate the two strands of DNA and the process is repeated. These machines are often also called thermocyclers because the heating system cycles on with each round of replication. As with all fluorescence methods, filters are required to specifically excite the fluorophores and separate the fluorescence signals from scattered light.

A list of stock filter sets for the common PCR dyes are listed below.

These are 25 mm round for excitation and emission filters and 25.7x36 mm for dichroics designed to work at 45 degrees. We also have extensive plate stock and components available, so contact us if you have special configuration requests or  you don’t see what you’re looking for here.

Fluorophore	Ex Max (nm)	Em Max (nm)	Suggested Filter Set
SYBR green	497	520	XF404
Cy-5	651	670	XF416
FAM	494	520	XF404
JOE	520	548	XF405, XF402
VIC	538	554	XF405, XF402
HEX	535	556	XF405, XF402
NED	546	575	XF405, XF402
PET	556	595	XF402
ROX	575	602	XF424
TAMRA	555	580	XF402
TET	521	536	XF405, XF402
Texas Red	595	615	XF424