Abstract: The CO difference spectra of cytochrome P450 (P450) in midgut and fat body of cotton bollworm, Helicoverpa armigera (Hübner), were investigated. The experiment indicated with traditional methods for quantifying cytochrome P450, the result was not easy to repeat even to the same sample. The interval between CO addition and measurement greatly influenced the value of A_450nm-490nm There was one to sixteenfold differences in optical density. In repetitive analysis on CO difference spectra of P450 in midgut and fat body, it was found that the optical density difference between 450 nm and 490 nm increased within a period of time and then decreased gradually. It was concluded that the parameter of the maximum optical density difference between 450nm and 490 nm was most accurate in determining the content of P450.
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Key words: Helicoverpa armigera, cytochrome P450, CO difference spectra