Nanoscale pores, nanopores, offer single molecule analytical capability that is achieved by electrophoretically driving the analytes in solution through them. The translocation of biological polymers through the nanopores has been investigated over three decades with particular focus on nucleic acids and, later on, peptides and proteins. Chapter 1 presents the principles and technical aspects of nanopore stochastic sensing with an emphasis on a biological pore, α-hemolysin. It serves as a versatile model for sensing the translocation of nucleic acid polymers and discriminating stationary oligonucleotides at single-base resolution. With the development of the enzymatic ratcheting of polynucleotides through the pore, base-by-base, nanopore-based DNA strand-sequencing has proven achievable. Protein information can also be read upon the protein analyte unfolding and translocating through the pore. This was achieved by either using a molecular motor or an electric potential acting on an oligonucleotide attached to the protein terminus. Taking advantage of the ability of nanopores to discriminate stationary oligonucleotides, the potential-driven method for protein translocation can be advanced to determine the directionality of entry (N or C terminus-first). To achieve the discrimination, the protein is expected to attach a different oligonucleotide to each terminus. In Chapter 2, we used a site-specific N-terminal cysteine condensation reaction, followed by a disulfide bond forming reaction, to conjugate two different oligonucleotides to a model protein (thioredoxin), one to the N terminus and the other to the C terminus. Chapter 3 presents the nanopore analysis of protein translocation direction. The oligonucleotide-attached protein bearing a single streptavidin bound at one of the two biotinylated oligonucleotide ends became unfolded as the unoccupied end was pulled through the pore under an applied potential. The different extent to which N- and C-terminal oligonucleotides block the pore indicated the direction of protein translocation through the pore. Interrogation of the reversal process, protein refolding, is described in Chapter 4. Upon binding the two biotinylated oligonucleotides to streptavidin at both ends, a single molecule of thioredoxin was captured within the pore. The protein could be subjected to repeated cycles of translocation and retro-translocation. After each unfolding and retro-translocation back, it was allowed to refold for various delay times before translocation again. Therefore, this system allows the characterization of protein folding at the single-molecule level. Thioredoxin collapses to a stable native-like structure rapidly, but the full refolding to its native state is approximately four orders of magnitude slower, possibly due to a rate-limiting step of cis prolyl peptide bond formation. The full details of methods are listed in Chapter 5.