cellular processes at a single-molecule level by taking advantage of the electrochemical nanoconfinement of a nanopore. Thus nanopore is a powerful sensor for investigation of fundamental physical, chemical or biological issues, such as molecule gating [5] and cation-induced current changing, [6] at single-molecule resolution [8] compared to other traditional technologies. To date, nanopores have been exploited for expanded applications, including detection of nanoparticles, [9][10][11] biopolymers, [1,12] proteins, [13][14][15] DNA-origami, [16] DNA-protein complexes, [17][18][19][20] and so on. One of the most potential applications of nanopore technology is nucleic acid sequencing, which is characterized as low cost and high throughput. Most recently, a lot of works have shown that each type of DNA nucleotide can induce correlated modulation of ionic current as they translocate through a nanopore. [12,[21][22][23] With the help of enzyme [24] or polymerase, [25] some biological nanopores [26,27] have shown the ability to determine the nucleotide sequence of a singlestranded DNA at single-base resolution.Different from DNA molecules, proteins consist of more than 20 amino acids (AAs) and are irregularly and slightly charged. Besides, proteins usually keep in folded state in natural environment. Thus, investigation of proteins is much more challenging than DNA. Unraveling the mechanisms of protein folding and unfolding and even realizing protein sequencing are essential for cellular behaviors and diseases. [28] Measurement of tunneling current [29,30] was reported to recognize single amino acids, however to make the tunneling device be a protein sequencing tool it should be coupled with a means that can thread the peptide chain through the gap in a controllable way, which could be possibly realized if the tunneling device is coupled to a nanopore. In the past two decades, most interests in nanopores have focused on DNA sequencing. Only in recent years, nanopore technology has been extended to protein sequencing as nanopores could sequence full-length proteins with high temporal and spatial resolution while traditional sequencing methods such as mass spectrometry [31] and Edman degradation [32] only rely on digestion of proteins into short peptides. Many experiments have shown that protein molecules can be electrophoretically driven through nanopores. [33,34] Some experiments showed that proteins can be unfolded using nanopores by adjusting pH values of the solution, [35] The function of a protein is determined by the composition of amino acids and is essential to proteomics. However, protein sequencing remains challenging due to the protein's irregular charge state and its high-order structure. Here, a proof of principle study on the capability of protein sequencing by graphene nanopores integrated with atomic force microscopy is performed using molecular dynamics simulations. It is found that nanopores can discriminate a protein sequence and even its protonation state at single-residue resolution. Both the pull...