Magnetic fine particles having lower critical solution temperature

A method for converting an objective substance into a converted material and recovering the converted material, comprising

• providing magnetic fine particles having immobilized thereto a copolymer that has a lower critical solution temperature, wherein the copolymer comprises a unit derived from a comonomer containing biotin as a constituent,
• immobilizing a substance having a mutual specific action with an objective substance to the magnetic fine particles to which biotin is bound,
• mixing the resulting magnetic fine particles and the objective substance to create a solution, in which the substance and the objective substance react,
• precipitating the magnetic fine particles by raising the temperature of the solution to a temperature not lower than the lower critical solution temperature of the magnetic fine particles, and
• recovering the converted material,
• wherein the biotin-containing comonomer is represented by general formula (2):
• wherein R2 represents a hydrogen atom or an alkyl group;
• R3 and R4 each independently represents a hydrogen atom, an alkyl group or an aryl group;
• T represents an oxygen atom or ═NH group;
• W represents a single bond or a carbonyl group, a thiocarbonyl group, or an alkylene group having 1 to 5 carbon atoms;
• U represents a single bond or —NH— group;
• X represents a single bond or a hydrocarbon group having 1 to 8 carbon atoms, an oxygen atom, or —NH— group;
• Y represents a single bond or a carbonyl group, a thiocarbonyl group, —NH— group, a 1,2-dioxyethylene group, or a 1,2-diaminoethylene group;
• Z represents a single bond or a carbonyl group, a thiocarbonyl group, an alkylene group having 1 to 5 carbon atoms, an oxygen atom, or —NH— group;
• and V represents a single bond or an alkylene group having 1 to 5 carbon atoms;
• or one of general formulae (3) to (5):
• wherein R1 represents a single bond or an alkylene group having 1 to 4 carbon atoms and R5 represents an alkylene group having 2 or 3 carbon atoms;
• X1 represents an oxygen atom or a sulfur atom;
• x2 to X5 each independently represents an oxygen atom or —NH— group;
• and T, R2, R3, and R4 each has the same definition as in the above general formula (2);
• or general formula (11):
• wherein T has the same definition as in the above general formula 2, or general formula (12):
• or general formula 13: