The advent of parallelized automated methods for rapid whole-genome analysis has led to an exponential drop in costs, thus greatly accelerating biomedical research and discovery. Third-generation sequencing techniques, which would utilize the characteristic electrical conductance of the four different nucleotides, could facilitate longer base read lengths and an even lower price per genome. In this work, we propose and apply a quantum-classical hybrid methodology to quantitatively determine the influence of the solvent on the dynamics of DNA and the resulting electron transport properties of a prototypic sequencing device utilizing a graphene nanopore through which the nucleic-acid chain is threaded. Our results show that charge fluctuations in the nucleotides are responsible for characteristic conductance modulations in this system, which can be regarded as a field-effect transistor tuned by the dynamic aqueous environment. ; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) ; Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) ; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)