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The integration of a tripeptide derivative , which is a versatile self - assembly motif , with a ruthenium ( II ) tris ( bipyridine ) complex affords the first supramolecular metallo - hydrogelator that not only self assembles in water to form a hydrogel but also exhibits gel - sol transition upon oxidation of the metal center .
 Chemical: tripeptide; Chemical: ruthenium ( II ) tris ( bipyridine )
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: tripeptide; Chemical: ruthenium ( II ) tris ( bipyridine )