A question related to the DNA hairpin reannealing when helicase binds on this hairpin

[Zhi Qi]

Dear all,

I have a question related to the DNA hairpin reannealing when helicase 
binds on this hairpin:

I have a DNA hairpin construct (89-bp on the stem), and then I load 
helicase to monitor hairpin unwound. The helicase I studied can bind 
around 20-nt ssDNA. So my question is that if only one helicase unwound 
the hairpin completely, does the DNA reanneal behind the helicase as the 
helicase only use 20-nt position and the hairpin is 89-bp? I read some 
paper, and it seems like if the helicase binds on the hairpin, even only 
one helicase, then no matter how long the hairpin is, the hairpin can 
not reanneal until the helicase unbind the hairpin. Is that true?

If anyone knows some conclusion or reference, please let me know.

Thank you so much!

Best Regards,
Zhi Qi
Biophysics, UIUC