Abstract: A magnetic powder treated with a coating agent, wherein the surface of the magnetic powder is coated with an alternating copolymer comprising a polyoxyethylene allyl methyl diether and maleic anhydride. An aqueous coating material containing the magnetic powder and a magnetic recording medium prepared by use of the magnetic powder. The magnetic powder of the present invention has a good dispersibility. The aqueous coating material containing the magnetic powder allows for coating under a simple and safe environment. Also the magnetic recording medium prepared by the use of magnetic powder exhibits excellent magnetic characteristics.

Abstract: The invention provides a modified haem which is chemically coupled with a polyalkylene glycol methyl ether or an .omega.-amino derivative thereof through at least one of the two carboxyl groups in said haem molecule. The modified haem has a peroxidase activity and is soluble in water or various organic solvents.

Abstract: Disclosed is a conjugate comprising a magnetic material and a physiologically active substance bound to each other through a polyethylene glycol derivative, and a conjugate comprising a magnetic material and a polyethylene glycol derivative bound to each other. According to the present invention, a bioreactor enabling application to or recovery of physiologically active substances under liquid state by utilizing the magnetic properties is provided.