SCYM Fluorochrome Selection 3

Question 1

Which fluorochrome combination is contraindicated in the same panel due to direct spectral overlap on the 488 nm laser?

Accepted Answer

FITC and PE

Answer

FITC and PE cannot easily coexist on the 488 nm laser in the same panel without very high compensation due to overlapping emission spectra.

Question 2

What is the primary limitation of tandem dyes such as PE-Cy7 compared to pure fluorochromes?

Accepted Answer

Incomplete energy transfer can produce anomalous emission peaks

Answer

Tandem dyes can suffer from incomplete FRET energy transfer, resulting in donor (e.g., PE) emission appearing in unexpected channels.

Question 3

For a marker present on only 0.1% of lymphocytes, which fluorochrome brightness tier is most appropriate?

Accepted Answer

Bright (e.g., PE or BV421)

Answer

Rare or dim populations require bright fluorochromes to generate sufficient signal above background noise.

Question 4

Which of the following fluorochromes is classified as a 'large Stokes shift' dye, useful for simplifying panel design?

Accepted Answer

Pacific Orange

Answer

Pacific Orange has a large Stokes shift, absorbing around 400 nm and emitting around 551 nm, allowing flexible panel design.

Question 5

APC has its excitation maximum at approximately which wavelength?

Accepted Answer

633–638 nm

Answer

APC (Allophycocyanin) has its excitation maximum near 650 nm, making it ideal for the 633 or 638 nm red laser.

(SCYM) Specialist in Cytometry Practice Test