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We examined the conformational preferences of the 2 - O - sulfated - 3 , 6 - alpha - D - anhydrogalactose ( compound I ) and two 1 , 3 linked disaccharides constituting - kappa or iota - carrageenans using density functional and ab initio methods in gas phase and aqueous solution .
 Chemical: 2 - O - sulfated - 3 , 6 - alpha - D - anhydrogalactose; Chemical: disaccharides
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
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Answer:
 Chemical: 2 - O - sulfated - 3 , 6 - alpha - D - anhydrogalactose; Chemical: disaccharides