A method of producing one of the conformational isomers of sc (Fv) 2 antibody comprising a substitution at an amino acid residue of the contact surface antibody sc (Fv) 2, which is formed by the variable heavy chain region and the variable light chain region of the antibody, so that the association of the polypeptide in the sc antibody (Fv) 2 is regulated for effectively one of the conformational isomers of sc (Fv) 2 antibody the method comprising steps of: (a) modifying a nucleic acid encoding an amino acid residue which forms the contact surface of the original nucleic acid polypeptide, so that the association of the polypeptide which is one of the conformational isomers in an antibody inhibited sc (Fv) 2 can form two types of conformational isomers (B) culturing host cells so that a nucleic acid sequence modified by step (a) is expressed and (c) recovering the host cell culture said conformational isomer of said antibody sc (Fv) 2, wherein the modification of step (a) is to modify the original nucleic acid so that replace one or more residues of amino acids in the contact surface so that two or more amino acid residues, including / the other / s mutated / s, which form the contact surface, carry the same type of positive or negative charge.Un método de producción de uno de los isómeros conformacionales de un anticuerpo sc(Fv)2 que comprende una sustitución en un resto de aminoácido de la superficie de contacto del anticuerpo sc(Fv)2, que está formado por la región variable de cadena pesada y la región variable de cadena ligera del anticuerpo, de modo que la asociación del polipéptido en el anticuerpo sc(Fv)2 se regulará para obtener de manera eficaz uno de los isómeros conformacionales de un anticuerpo sc(Fv)2, comprendiendo el método las etapas de: (a) modificar un ácido nucleico, que codifica un resto de aminoácido que forma la superficie de contacto del polipéptido del ácido nucleico original, de modo que se inhiba la asociación del polipéptido que forma uno d
