Table 1. Enrichment of Active Wild-Type Arylsulfatase (PAS) versus Low Activity Mutant H211A^a.

percentage active cells in starting population	cells per droplet	enrichment (n-fold)
0.1%	0.1	800
0.01%	0.1	2500
0.0001%	1	100 000

^aThe left column refers to the mixture of active versus low activity clones that was compared with the clones recovered after flow cytometric sorting that showed a positive plate screening assay (right column). Cells per droplet gives the average droplet occupancy for each sample. Note that droplet shrinking (see section below on osmotic droplet volume changes) was employed to maintain the throughput at the higher occupancy used in the third experiment. Enrichment was determined by dividing the percentage of positives after sorting by that before sorting.