Ultrafast time-resolved fluorescence study on formation and excitation dynamics of human telomeric and homo-oligomeric i-motifs at neutral pH

Abstract

Asides from the common double stranded structure, nucleic acids depending on the base content and environmental condition may take many non-canonical secondary structures, including the fourstranded intercalated i-motif structure formed from cytosine-rich sequences that are abundant throughout the human genome.[1,2] The structures of i-motifs are known to be stable at slightly acidic condition, whether they can also be formed at the physiologically relevant neutral pH condition remains elusive and currently one of the frontier issues in the study of non-canonical nucleic acid structures.[3,4] Herein we present a comparative steady-state and ultrafast time-resolved fluorescence investigation of a homo-oligomeric and human telomeric cytosine-rich sequence at both the acidic and neutral pH.