Abstract: The present disclosure relates to tagged nucleoside-5?-oligophosphates having a positively charged polymer tag structure and components thereof. Such nucleoside-5?-oligophosphates are useful, for example, in nanopore-based sequencing-by-synthesis applications. Also disclosed herein are nanopore constructs engineered to have additional negatively-charged moieties in the channel of the nanopore. Such nanopores can be useful, for example, for providing a repellant force against template and/or primer nucleic acids inserting into the pore during a nucleic sequence-by-synthesis process. The tagged nucleoside-5?-oligophosphates and nanopores disclosed herein can be used together to provide nanopore-based nucleic acid sequencing-by-synthesis systems and processes having reduced background tag levels and improved throughput.