Herschhorn A, Ma X, Gu C, Ventura JD, Castillo-Menendez L, Melillo B, Terry DS, Smith AB, Blanchard SC, Munro JB, Mothes W, Finzi A, Sodroski J. Release of gp120 Restraints Leads to an Entry-Competent Intermediate State of the HIV-1 Envelope Glycoproteins. mBio. 2016 10 25; 7(5).