The interaction between nanomaterial and biomolecules is essential to nanoparticle-based biotechnology and biomedical applications, such as gene delivery, 1 cellular imaging, 2 tumor therapy, 3 and biological experimental technology. 4 It is also critical for the understanding of the growing concerns about the biosafety of these nanomaterials. 5À11 There have been extensive studies recently on the adsorption of proteins onto nanomaterial, particularly graphitic nanomaterials such as carbon nanotubes and fullerenes, both experimentally and theoretically, and it is shown that these adsorptions can affect both protein structures and functions. For example, Wu and co-workers have found that there are local structural distortions after protein streptavidin is bound onto a single-wall carbon nanotube (SWCNT). 12 Karajanagi et al. have also observed changes in both conformation and activity of two enzymes, α-chymotrypsin and soybean peroxidase, upon adsorption onto SWCNTs. 13 We have recently found that SWCNTs can plug into the hydrophobic cores of signaling and pathway regulatory proteins, WW domains, to form stable complexes 14 and can also win the competitive binding over the native binding ligand (proline-rich motifs) on the SH3 domain, 15 which are two possible routes of nanoparticles affecting protein functions.ProteinÀgraphene interactions, on the other hand, are relatively less studied. Graphene is a flat monolayer of carbon atoms

Protein misfolding in the form of fibrils or spherulites is involved in a spectrum of pathological abnormalities. Our current understanding of protein aggregation mechanisms has primarily relied on the use of spectrometric methods to determine the average growth rates and diffraction-limited microscopes with low temporal resolution to observe the large-scale morphologies of intermediates. We developed a REal-time kinetics via binding and Photobleaching LOcalization Microscopy (REPLOM) super-resolution method to directly observe and quantify the existence and abundance of diverse aggregate morphologies of human insulin, below the diffraction limit and extract their heterogeneous growth kinetics. Our results revealed that even the growth of microscopically identical aggregates, e.g., amyloid spherulites, may follow distinct pathways. Specifically, spherulites do not exclusively grow isotropically but, surprisingly, may also grow anisotropically, following similar pathways as reported for minerals and polymers. Combining our technique with machine learning approaches, we associated growth rates to specific morphological transitions and provided energy barriers and the energy landscape at the level of single aggregate morphology. Our unifying framework for the detection and analysis of spherulite growth can be extended to other self-assembled systems characterized by a high degree of heterogeneity, disentangling the broad spectrum of diverse morphologies at the single-molecule level.

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Hydrolysis is an important component of the aging of cellulose, and it severely affects the insulating performance of cellulosic materials. The diffusion behavior of water molecules in amorphous cellulose and their destructive effect on the hydrogen bonding structure of cellulose were investigated by molecular dynamics. The change in the hydrogen bonding structure indicates that water molecules have a considerable effect on the hydrogen bonding structure within cellulose: both intermolecular and intramolecular hydrogen bonds decreased with an increase in ingressive water molecules. Moreover, the stabilities of the cellulose molecules were disrupted when the number of intermolecular hydrogen bonds declined to a certain degree. Both the free volumes of amorphous cells and water molecule-cellulose interaction affect the diffusion of water molecules. The latter, especially the hydrogen bonding interaction between water molecules and cellulose, plays a predominant role in the diffusion behavior of water molecules in the models of which the free volume rarely varies. The diffusion coefficient of water molecules has an excellent correlation with water molecule-cellulose interaction and the average hydrogen bonds between each water molecule and cellulose; however, this relationship was not apparent between the diffusion coefficient and free volume.

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