Diagrammatic representation of various plasmids encoding LC, Fd, and Fd fusion proteins. All the plasmids carry insert between Nhe I (GCTAGC) and Mlu I (ACGCGT) restriction sites and are under the control of T7 promoter. ATG of Nde I site (CATATG) is the initiation codon. Only relevant genes and restriction sites are shown. The map is not to the scale. T7, T7 promoter; env1C, 31 amino acids (590–620) of HIV-1 envelope gp41 containing native cysteine residues; env1S, 31 amino acids (590–620) of HIV-1 envelope gp41 with cysteine 605 and 611 replaced by serine residues; env2C, 31 amino acids (581–611) of HIV-2 envelope gp36 containing native cysteine residues; env2S, 31 amino acids (581–611) of HIV-2 envelope gp36 with cysteine 597 and 603 replaced by serine residues; cmyc, decapeptide recognized by monoclonal antibody, 9E10; T, T7 transcription terminator; F+, phage M13 origin of replication; Ampr, β-lactamase gene; Ori, ColE1 origin of replication; VH, variable domain of the heavy chain of MAb B6; CH1, the first constant domain of heavy chain of B6; VL, variable domain of the light chain of B6; CL, constant domain of light chain of B6. A. Expression vector for B6Fd. B. Expression vector for B6LC. C. Segment of expression vector pVCB6Fdenv showing the cassette between B6Fd and cmyc. The cysteine residues in env1/env2, which make intra-molecular disulfide bond, are shown. The serine residues that replace the cysteine residues in env are shown. D. Segment of expression vector pVCB6Fdenv12 showing the cassette of chimeric env1 and env2 sequence between B6Fd and cmyc. The serine and cysteine residues in env sequences are shown. L, linker.