Abstract: An object of the present invention is to provide novel polypeptides that are capable of binding to an immunoglobulin and have high stability against alkali. The present invention relates to proteins having the amino acid sequence of SEQ ID No:1 or 2.

Abstract: The low-molecular-weight compound represented by the general formula (1): ArX-(Linker)-ArYHB (1), wherein ArX is a structure containing an optionally substituted aromatic six-membered ring, ArYHB is a structure containing an optionally substituted aromatic six-membered ring having a proton donor, the atom group “Linker” has not less than 4 and not more than 30 atoms and binds ArX with ArYHB, is used for binding a proteinaceous substance.

Abstract: An object of the present invention is to provide a technique to create novel engineered protein ligands that, when immobilized through a lysine residue (its side chain ?-amino group) which allows for efficient immobilization to a carrier, show the optimum binding capacity and binding efficiency to a target molecule. The present invention provides an engineered protein having a sequence obtained by replacing all the lysine residues in Protein A, which is the most typical protein ligand, with other amino acids, and adding lysine at a terminal; and an affinity separation matrix in which such an engineered protein is immobilized on a water-insoluble carrier by reductive amination or the like. This affinity separation matrix is characterized by its high binding capacity to a target molecule even when the immobilized amount of the ligand is small.

Abstract: An object of the present invention is to provide novel polypeptides that are capable of binding to an immunoglobulin and have high stability against alkali. The present invention relates to proteins having the amino acid sequence of SEQ ID No:1 or 2.

Abstract: An object of the present invention is to create a novel engineered Protein A ligand having better antibody dissociation properties in the acidic condition compared with known engineered Protein A ligands. The present invention provides a protein having an affinity for an immunoglobulin, including an amino acid sequence obtained by introducing, into an amino acid sequence derived from any of E, D, A, B and C domains of Protein A, at least one amino acid substitution at any one or more of amino acid residues corresponding to positions 31 to 37 of the A, B and C domains (positions 29 to 35 of the E domain, positions 34 to 40 of the D domain), which are conserved in all the domains, the protein having a lower affinity for an Fab region of an immunoglobulin than a protein having the amino acid sequence before introduction of the substitution.

Abstract: An object of the present invention is to create a novel engineered Protein A ligand having better antibody dissociation properties in the presence of an acid than conventional engineered Protein A ligands and a further object of the present invention is to create a novel engineered Protein A ligand having higher alkali resistance. The present invention is to provide a protein having an affinity for an immunoglobulin, including an amino acid sequence derived from any of E, D, A, B and C domains of Protein A, wherein at least one Gly residue in the amino acid sequence is replaced with an amino acid other than Ala, and the protein has a lower affinity for an Fab region of an immunoglobulin than a protein including an amino acid sequence in which the Gly residue is replaced with Ala. Also, the present invention is to provide the protein having an affinity for an immunoglobulin, which has improved chemical stability in an alkaline condition compared to the corresponding domain.