A method for obtaining a variant of a starting OB-fold protein binding to a target, and presenting a nanomolar or better affinity with said target, wherein said target is a protein or a peptide and wherein said affinity is measured by competition Surface Plasmon Resonance, comprising the steps of a) Providing a combinatorial library of variants of said starting OB-fold protein in which 5 to 32 residues involved in the binding of said starting OB-fold protein with its native ligand have been randomized, and optionally wherein said variants further comprise an insertion of 1 to 15 random amino acid residues in loop 3 and/or an insertion of 1 to 15 random amino acid residues in loop 4, and/or an insertion of 1 to 20 random amino acid residues in loop 1, and optionally wherein 1 to 4 residues of said starting OB-fold protein have been deleted, b) Expressing said variants of said library by ribosome display c) Exposing said expressed variants obtained in step b. to said immobilized target, wherein said target is a protein or a peptide d) Selecting said variants which bind to said immobilized target e) Eluting and recovering the mRNA from said variants selected in step d. f) Reverse-translating and amplifying said recovered mRNA in order to obtain a sub-library of selected variants of said starting OB-fold protein g) Performing again said steps b. to f. from zero to three further rounds h) Expressing said variants of said sub-library obtained after step g. by ribosome display i) Exposing said expressed variants obtained in step h. to said target which is biotinylated j) Incubating this composition comprising said expressed variants and said target of interest of step i. k) Capturing ternary complexes (mRNA-ribosome-binder) bound to biotinylated target with magnetic streptavidin coated beads l) Washing said beads and isolating mRNA m) Reverse-translating and amplifying said recovered mRNA in order to obtain a sub-library of selected variants of said starting OB-fold protein n) Selecting one element of said sub-library of step m., wherein said element codes for a variant of said starting OB-fold protein which comprises 5 to 32 residues mutated in the binding interface with the native ligand of said starting OB-fold protein, and which binds to said target, and wherein the affinity of said variant to said target is a nanomolar or better affinity. a) Providing a combinatorial library of variants of said starting OB-fold protein in which 5 to 32 residues involved in the binding of said starting OB-fold protein with its native ligand have been randomized, and optionally wherein said variants further comprise an insertion of 1 to 15 random amino acid residues in loop 3 and/or an insertion of 1 to 15 random amino acid residues in loop 4, and/or an insertion of 1 to 20 random amino acid residues in loop 1, and optionally wherein 1 to 4 residues of said starting OB-fold protein have been deleted, b) Expressing said variants of said library by ribosome display c) Exposing said expressed variants obtained in step b. to said immobilized target, wherein said target is a protein or a peptide d) Selecting said variants which bind to said immobilized target e) Eluting and recovering the mRNA from said variants selected in step d. f) Reverse-translating and amplifying said recovered mRNA in order to obtain a sub-library of selected variants of said starting OB-fold protein g) Performing again said steps b. to f. from zero to three further rounds h) Expressing said variants of said sub-library obtained after step g. by ribosome display i) Exposing said expressed variants obtained in step h. to said target which is biotinylated j) Incubating this composition comprising said expressed variants and said target of interest of step i. k) Capturing ternary complexes (mRNA-ribosome-binder) bound to biotinylated target with magnetic streptavidin coated beads l) Washing said beads and isolating mRNA m) Reverse-translating and amplifying said recovered mRNA in order to obtain a sub-library of selected variants of said starting OB-fold protein n) Selecting one element of said sub-library of step m., wherein said element codes for a variant of said starting OB-fold protein which comprises 5 to 32 residues mutated in the binding interface with the native ligand of said starting OB-fold protein, and which binds to said target, and wherein the affinity of said variant to said target is a nanomolar or better affinity.