Patent ID: 7258985

Claim:
A method for the identification of intrabody frameworks or intrabodies which are soluble and stable in reducing conditions comprising the following steps: transformation of suitable host cells a nucleic acid library, said library encoding a fusion product comprising an intrabody and a transcriptional activation domain wherein said transcriptional activation domain is only active as part of a fusion protein comprising an intrabody moiety which is soluble and stable and culturing said cells under conditions allowing the identification and selection of cells expressing an intrabody moiety which is soluble and stable in reducing conditions by detection of a reporter gene that is expressed by the interaction of the transcriptional activation domain with a DNA binding domain in the host cell wherein the interaction of the transcriptional activation domain with the DNA binding domain results in the growth or identification of cells indicating that the intrabody frameworks or intrabodies are stable and soluble under reducing conditions and is not dependent upon the presence of the antigen for which the intrabody is specific.