15097
On the basis of the specific noncentrosymmetry requirements for second - order nonlinear optical effects , we had hypothesized that the surprisingly low first hyperpolarizability ( beta ) of the enhanced yellow fluorescent protein ( eYFP ) could be explained by centrosymmetric stacking of the chromophoric Tyr66 and the neighboring Tyr203 residue .
 Chemical: Tyr66; Chemical: Tyr203
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: Tyr66; Chemical: Tyr203