Shanghai;
Research;
Center;
of;
Biotechnology,;
Chinese;
Academy;
of;
Sciences,;
Shanghai;
200233,;
China;
Shanghai;
Research;
Center;
of;
Biotechnology,;
Chinese;
Academy;
of;
Sciences,;
Shanghai;
200233,;
China;
Shanghai;
Research;
Center;
of;
Biotechnology,;
Chinese;
Academy;
of;
Sciences,;
Shanghai;
200233,;
China;
Shanghai;
Research;
Center;
of;
Biotechnology,;
Chinese;
Academy;
of;
Sciences,;
Shanghai;
200233,;
China;
Shanghai;
Research;
Center;
of;
Biotechnology,;
Chinese;
Academy;
of;
Sciences,;
Shanghai;
200233,;
China;
human; tumor; necrosis; factor,; site-directed; mutation,; cytotoxicity,; LD50,; Western; blot.;