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• It demonstrates water can be spontaneously drawn into the multi-walled carbon nanotube (MWCNT) capillaries and can be transformed into ice nanotubes (INTs) through first-order liquid–solid phase transition based on molecular dynamics simulations. • The INT structures formed in the gaps of MWCNT can be controlled by tuning the inter-wall spacings of the MWCNT, Flat-square-walled INTs and puckered-rhombic-walled INTs will separately be formed with the inter-wall spacings of 6.66 and 8.61 Å, respectively. • The freezing zones of water confined in MWCNTs are tunable, e.g. water confined in MWCNTs with the inter-wall spacings of 6.66 Å, the freezing will occur zone by zone and can be controlled by the temperature. One-dimensional nanoconfined water exhibits rich structure phases. The freezing behavior of water confined in single-walled carbon nanotubes has been studied by both experimental measurements and theoretical simulations, however, it lacks of studying the freezing behavior of water confined in multi-walled carbon nanotubes (MWCNTs). Herein, we investigated the freezing behavior of water confined in MWCNTs using molecular dynamics simulations. Flat-square-walled ice nanotubes (FSW-INTs) were formed in the gaps with the inter-wall spacing of 6.66 Å, while, puckered-rhombic-walled ice nanotubes (PRW-INTs) were observed in the gaps with the inter-wall spacing of 8.61 Å. Then, the INT structures formed among the inter-wall gaps of MWCNTs can be controlled by tuning the inter-wall spacings of MWCNTs. Specifically, various groups of FSW-INTs and/or PRW-INTs were designed to form by using MWCNTs with the inter-wall spacing of 6.66 and/or 8.61 Å. In addition, it was found that water could be frozen in a simultaneous way or be frozen in a zone-by-zone form by tuning the inter-wall spacings of the MWCNTs due to the freezing temperatures of INTs are related with their diameters. The study will provide deep insights into the freezing behavior of water in MWCNTs. [ABSTRACT FROM AUTHOR]

Pathological aggregation of amyloid polypeptides is associated with numerous degenerative diseases. Preventing aggregation and clearing amyloid deposits are considered as promising strategies against amyloidosis. With the capacity of crossing the blood-brain barrier and good biocompatibility, the hydroxylated single-walled carbon nanotube (SWCNT-OH) has been shown with excellent anti-amyloid properties. Here, we systematically studied the SWCNT-OH effects on the fibrillization of the β2m 21 – 31 peptides utilizing all-atom discrete molecular dynamics (DMD) simulation. Our results demonstrated the isolated β2m 21 – 31 peptides first nucleated into unstructured oligomers followed by coil-to-sheet conformational conversions in oligomers with at least six peptides. The elongation and lateral surfaces of the preformed β-sheet could catalyze the other unstructured monomers and small oligomers converted into β-sheet formations via dock-lock fibril growth and secondary nucleation processes. Eventually, the β2m 21 – 31 peptides would self-assemble into well-ordered cross-β structures. Regardless of isolated monomers or well-defined cross-β assemblies, the β2m 21 – 31 would attach on the surfaces of SWCNT-OH adopting unstructured formations indicating the SWCNT-OH not only inhibited the fibrillization of β2m 21 – 31 but also destroyed pre-formed proto-fibrils. Overall, our study displays a complete picture of the fibrillization mechanism of β2m 21 – 31 and the amyloid inhibitory mechanism of SWCNT-OH, offering new insight into the de-novo design of anti-amyloid inhibitors. [Display omitted] • The fibrillization of β2m 21-31 involves the primary and secondary nucleations of β-sheet aggregates and β-sheet growth. • The conformational conversion of β2m 21-31 from unstructured to β-sheet starts from hexamers. • The SWCNT-OH not only inhibits the aggregation of β2m 21-31 but also destroys the pre-formed cross-β aggregates of β2m 21-31. [ABSTRACT FROM AUTHOR]