With the potential wide uses of nanoparticles such as carbon nanotubes in biomedical applications, and the growing concerns of nanotoxicity of these engineered nanoparticles, the importance of nanoparticle-protein interactions cannot be stressed enough. In this study, we use both experimental and theoretical approaches, including atomic force microscope images, fluorescence spectroscopy, CD, SDS-PAGE, and molecular dynamics simulations, to investigate the interactions of single-wall carbon nanotubes (SWCNTs) with human serum proteins, and find a competitive binding of these proteins with different adsorption capacity and packing modes. The π-π stacking interactions between SWCNTs and aromatic residues (Trp, Phe, Tyr) are found to play a critical role in determining their adsorption capacity. Additional cellular cytotoxicity assays, with human acute monocytic leukemia cell line and human umbilical vein endothelial cells, reveal that the competitive bindings of blood proteins on the SWCNT surface can greatly alter their cellular interaction pathways and result in much reduced cytotoxicity for these protein-coated SWCNTs, according to their respective adsorption capacity. These findings have shed light toward the design of safe carbon nanotube nanomaterials by comprehensive preconsideration of their interactions with human serum proteins.competitive adsorption | nanoparticle-protein corona | hydrophobic interactions | conformational flexibility C arbon nanotubes (CNTs) have a broad range of potential applications, including nanoelectronics (1), biosensors (2), biomolecular recognition devices and molecular transporters (3, 4), and cancer therapy and diagnoses (5-7), because of their extraordinary mechanical, electronic, optical, geometric, and biological properties. Both the pharmacological (8, 9) and toxicological (10-15) profiles of CNTs have attracted much attention in recent years. Nanomedicine provides a great potential in fighting many diseases but a global effort is much needed to safely translate laboratory innovations into clinic trials. Seven grand challenges have been proposed for this endeavor (16). CNTbased multimodality imaging and therapy have been proposed for a variety of medical applications, such as carriers for chemotherapeutic drugs (17, 18), Raman detection and imaging (19,20), photoacoustic imaging, and photothermal therapy of cancers (6, 21). Meanwhile, of equal importance there is the emerging field of nanotoxicology, which aims to address the biosafety of these engineered nanoparticles, in particular, how these nanoparticles interact with human proteins in vivo (22)(23)(24)(25).Many studies have been performed on the biological effects of carbon nanotubes, and the interactions between proteins and CNTs (nanoparticle-protein corona) are believed to play an important role in the biological effects of CNTs (26-28). For example, CNTs could bind with pulmonary surfactant proteins A and D and then lead to susceptibility of lung infection and emphysema in mice (29). When the functionalized CNTs w...

The idea of the out-of-time-order correlator (OTOC) has recently emerged in the study of both condensed matter systems and gravitational systems. It not only plays a key role in investigating the holographic duality between a strongly interacting quantum system and a gravitational system, but also diagnoses the chaotic behavior of many-body quantum systems and characterizes the information scrambling. Based on the OTOCs, three different concepts -quantum chaos, holographic duality, and information scrambling -are found to be intimately related to each other. Despite of its theoretical importance, the experimental measurement of the OTOC is quite challenging and so far there is no experimental measurement of the OTOC for local operators. Here we report the measurement of OTOCs of local operators for an Ising spin chain on a nuclear magnetic resonance quantum simulator. We observe that the OTOC behaves differently in the integrable and non-integrable cases. Based on the recent discovered relationship between OTOCs and the growth of entanglement entropy in the many-body system, we extract the entanglement entropy from the measured OTOCs, which clearly shows that the information entropy oscillates in time for integrable models and scrambles for non-intgrable models. With the measured OTOCs, we also obtain the experimental result of the butterfly velocity, which measures the speed of correlation propagation. Our experiment paves a way for experimentally studying quantum chaos, holographic duality, and information scrambling in many-body quantum systems with quantum simulators.Recent studies also reveal that the OTOC can be applied to study physical properties beyond chaotic systems. The decay of the OTOC is closely related to the delocalization of information and implies the informationtheoretic definition of scrambling. In the high tem-arXiv:1609.01246v3 [cond-mat.str-el]