17140
For this reason , modified oligonucleotides and fluorescent base analogues that serve as " internal " fluorescent probes are presented as an orthogonal means for detecting conformational changes , without necessarily perturbing the equilibria between G - quadruplex , single - stranded , and duplex DNA .
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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:
 None