16717
Fifty - one of these 68 chemicals induced stronger Type I binding spectra ( iron low - to high - spin state shift ) with P450 2A13 than those seen with P450 2A6 , i . e . , the spectral binding intensities ( Delta Amax / Ks ratio ) determined with these chemicals were always higher for P450 2A13 .
 Chemical: iron
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: iron