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To explore the prevalence of these sites , we compared 37 known crystal structures from 13 different ALDH families and evaluated the possible existence of a cation on the basis of the number , distance and geometry of its potential interactions , as well as of B - factor values of modeled cations obtained in new refinements of some reported crystal structures .
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Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
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