Abstract: Methods of chemical and biochemical functionalization of yarn and textile products are described. A yarn or textile product is contacted with a linker molecule comprising two or more photochemically activatable chemical groups and a non-linker molecule having a desired property. Photochemical activation of the chemical groups causes covalent attachment of the non-linker molecule to the yarn or textile product by means of the linker molecule in a single step. The methods are particularly useful for immobilization to yarn or textile of biomolecules that are susceptible to denaturation. Use of linker molecules derived from proteins or polysaccharides further minimizes denaturation of the biomolecule.