Product Specifications HIV-1 envelope 131 antigen recombinant: Description: Produced in genetically engineered yeast cells as a fusion with human superoxide dismutase (SOD). It covers from Val 473 to Leu 668 (D Ala 518 to Val 546) of the HIV-1 (SF-2 isolate) envelope protein. It has been purified by differential extraction followed by gel filtration.Molecular Weight: 35.6 kDa.Purity: Over 90