PhycoPro™ R-Phycoerythrin (red algae)
PhycoPro™ R-Phycoerythrin (RPE) is a phycobiliprotein isolated from a species of red algae chosen specifically because it yields one of the most highly fluorescent of the RPEs. Like other phycobiliproteins, ProZyme® RPE is fluorescent, with an extremely high absorptivity, a high quantum efficiency, a large Stokes shift and excitation and emission bands at visible wavelengths. It is a stable protein which can be easily linked to antibodies and other proteins by conventional protein cross-linking techniques without altering its spectral characteristics.
Size: 5mg, 10mg, 100mg, 500mg
Bulk pricing is available, please contact us for details.
Product Code: PB32
Q. What is the difference between PB31 that you used to have on your website, and PB32 RPE?
A. PB32 is produced from the same Porphyra-like algal strain as PB31, but undergoes an additional purification step to remove free RPE subunits.
We believe PB32 is a suitable replacement for PB31, and may provide better results in conjugation applications. However, if you would prefer to use PB31, please contact us.
Q. How do I measure RPE concentration?
A. We measure RPE concentration at 566 nm. Multiply the absorbance at λmax (566 nm) by 10 and divide by the extinction coefficient (82) to yield the concentration of the RPE (mg/ml).
RPE concentration (mg/ml) = (A566 measurement x 10) / 82
We give our extinction coefficients as E1% at λmax, which is the absorbance of a 1% solution (10 mg/ml) in a cuvette with a 1 cm path length. However, many scientists are used to seeing extinction coefficients for proteins at 1 mg/ml (0.1%). For RPE this works out as an A566 absorbance value of 8.2 for a 1 mg/ml solution, and makes for a simpler calculation:
RPE concentration (mg/ml) = A566 measurement / 8.2
We measure concentration spectrophotometrically rather than fluorometrically. Further information on calculating phycobiliprotein concentration & molarity is available in our Conjugate Evaluation tech note.
Q. I want to desalt the 60% ammonium sulfate suspension of PB32 RPE prior to e.g. activation, or sterile filtration. Can I dilute the suspension then use a spin column to desalt?
We would not suggest using spin desalting columns, as they don’t have the resolution to completely remove the ammonium ions.
We would suggest using one of the following options for desalting:
1. Dialyze the RPE in the buffer of your choice (be sure to perform several buffer changes over at least a day to ensure complete exchange of the ammonium ions). Standard dialysis tubing or commercial dialysis cassettes or cartridges can be used, intact RPE is around 240 kDa.
2. Desalt using a column such as a PD-10 column from GE. In this case the RPE should be pelleted by centrifugation (and the colorless supernatant discarded) and the pellet completely redissolved in buffer prior to loading on the column. This can also be used to jump-start the dialysis option above if time is a factor. We suggest a sample volume that is no more than 10% of the column bed volume, to be safe.
Product Safety Documentation for PB32:
|PB32||R-Phycoerythrin (red algae)|