The invention provides methods of using sequence based analysis and rational strategies to modify and improve the structural and biophysical properties of single chain antibodies (scFvs), including stability, solubility, and antigen binding affinity. These methods and strategies can be used individually or in combination. The methods of the present invention also include the use of a database comprising scFv sequences from an experimentally screened scFv library of antibodies that have been selected to have superior solubility and stability. The invention also provides methods of using the properties found for these selected antibodies in a general approach for reshaping scFv antibodies to improve stability and solubility properties of a single chain antibody fragment.