Ethidium homodimer is responsible for the red color observed

Ethidium homodimer is responsible for the red color observed. How is it able to cross an intact plasma membrane?

a. binds to calcein

b. it can\'t

c. esterase

d. binds to flippase

Solution

1. Calcein, is a green membrane permeable flourescent dye that is hydrolyzed by esterase, causing it to become negatively charged and be retained in the cytoplasm, along with ethidium homodimer, a positively charged flourecent nucleic acid stain that cannot cross intact cell membranes.