Peptide Nucleic Acid Containing a Meta-Substituted Phenylpyrrolocytosine Exhibits a Fluorescence Response and Increased Binding Affinity toward RNA

Peptide nucleic acids (PNA) containing meta-substituted 6-phenylpyrrolocytosine (PhpC), [mono-m)-(aminoethoxy)phenyl]pyrrolocytosine (mmePhpC), [mono-m-(aminopropoxy)phenyl]pyrrolocytosine (mmpPhpC), and [mono-m-(guanidinoethoxy)phenyl]pyrrolocytosine (mmguaPhpC), have been synthesized. Meta-substituted PhpCs have been hybridized with overall higher binding affinity toward DNA and RNA than previously synthesized moePhpC or newly synthesized mopPhpC. The guanidinium-containing nucleobase, mmguaPhpC, exhibited the highest increase in binding affinity toward RNA while fluorometrically responding on the state of hybridization.