Immunoglobulin frameworks which demonstrate enhanced stability in the intracellular environment and methods of identifying same

A single-chain antibody comprising a human variable light chain framework (VL) and a human variable heavy chain framework (VH having the general structure:

• NH2-VL-linker-VH—COOH;
• or
• NH2—VH-linker-VL-COOH
• wherein the single-chain antibody has the VH framework and the VL framework of
• AK, BK, CK, DK, EK, FK, and GK;
• wherein A is the amino acid sequence
• (Seq. Id. No. 1)
• EIVMTQSPSTLSASVGDRVIITCRASQSISSWLAWYQQKPGKAPKLLIYK
• ASSLESGVPSRFSGSGSGAEFTLTISSLQPDDFATYYCQQYKSYWTFGQG
• TKLTVLG;
• B is the amino acid sequence
• (Seq. Id. No. 2)
• EIVLTQSPSSLSASVGDRVTLTCRASQGIRNELAWYQQRPGKAPKRLIYA
• GSILQSGVPSRFSGSGSGTEFTLTISSLQPEDVAVYYCQQYYSLPYMFGQ
• GTKVDIKR;
• C is the amino acid sequence
• (Seq. Id. No. 3)
• EIVMTQSPATLSVSPGESAALSCRASQGVSTNVAWYQQKPGQAPR
• LLIYGATTRASGVPARFSGSGSGTEFTLTINSLQSEDFAAYYCQQYKHWP
• PWTFGQGTKVEIKR;
• D is the amino acid sequence
• (Seq. Id. No. 4)
• QSVLTQPPSVSAAPGQKVTISCSGSTSNIGDNYVSWYQQLPGTAPQLLIY
• DNTKRPSGIPDRFSGSKSGTSATLGITGLQTGDEADYYCGTWDSSLSGVV
• FGGGTKLTVLG;
• E is the amino acid sequence
• (Seq. Id. No. 5)
• EIVLTQSPATLSLSPGERATLSCRASQTLTHYLAWYQQKPGQAPR
• LLIYDTSKRATGVPARFSGSGSGTDFTLTISSLEPEDSALYYCQQRNSWP
• HTFGGGTKLEIKR;
• F is the amino acid sequence
• (Seq. Id. No. 6)
• SYVLTQPPSVSVAPGQTATVTCGGNNIGSKSVHWYQQKPGQAPVL
• VVYDDSDRPSGIPERFSGSNSGNTATLTIRRVEAGDEADYYCQVWDSSSD
• HNVFGSGTKVEIKR;
• G is the amino acid sequence
• (Seq. Id. No. 7)
• LPVLTQPPSVSVAPGQTARISCGGNNIETISVHWYQQKPGQAPVL
• VVSDDSVRPSGIPERFSGSNSGNTATLTISRVEAGDEADYYCQVWDSSSD
• YVVFGGGTKLTVLG;
• and
• K is the amino acid sequence
• (Seq. Id. No. 11)
• EVQLVESGGGLVQPGGSLRLSCAASGFTFSSYAMSWVRQAPGKGL
• EWVSAISGSGGSTYYADSVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYY
• CAKDAGIAVAGTGFDYWGQGTLVTVSS.