Abstract: Disclosed are a fused DNA sequence which comprises a DNA sequence of a heat-resistant protein, fused directly or indirectly to a DNA sequence coding a selected protein or peptide, a fused protein expressed from the fused DNA sequence, and a method for expressing the fused protein.

Abstract: Disclosed are an immunoassay device which comprises a labeled substance dotting portion and a specimen dotting portion provided thereon, and an immunoassay method using the device.

Abstract: There are disclosed a magnetic particle for an immunoassay method, which comprises a core and a coating layer formed on the surface of the core wherein said core comprises an organic polymer matrix and said coating layer comprises a mixed crystal ferrite represented by the formula:M.sub.x Fe.sub.(3-x) O.sub.4wherein M represents at least one metal selected from the group consisting of Mn, Ni, Zn, Co, Cu, Mg, Sn, Ca and Cd, and x is a number satisfying the relation: 0<x<3,and an antigen or an antibody is bound onto the surface of the coating layer and wherein said particle has a particle size of 0.03 to 10 .mu.m, and an immunoassay method using the same.