Microwave (MW) radiation is known to heat carbon nanotubes (CNTs) very efficiently. The maximum allowable MW irradiance to avoid proteins from denaturing was determined. The MW irradiance of 100-300 J was sufficient to denature a recognizable amount of hemoglobin with CNTs, but the same irradiance had no effect without CNTs. Additionally, CNT under MW radiation was found to accelerate reduction of ferric cytochrome c.