Cancer cells secrete extracellular vesicles (EVs) covered with a carbohydrate polymer, hyaluronan (HA), linked to tumor malignancy. Herein, we have unravelled the contour lengths of HA on a single cancer cell-derived EV surface using single-molecule force spectroscopy (SMFS), which divulges the presence of low molecular weight HA (LMW-HA < 200 kDa). We also discovered that these LMW-HA-EVs are significantly more elastic than the normal cell-derived EVs. This intrinsic elasticity of cancer EVs could be directly allied to the LMW-HA abundance and associated labile water network on EV surface as revealed by correlative SMFS, hydration dynamics with fluorescence spectroscopy, and molecular dynamics simulations. This method emerges as a molecular biosensor of the cancer microenvironment.

Aggregation of intrinsically disordered as well as the ordered proteins under certain premises or physiological conditions leads to pathological disorder.

We report the growth of nano-ripple on, initially, smooth Si surface due to chemically guided additional instability generation during 10 keV C+ bombardment at grazing (700) ion incidence. Also, the transformation of the ripple structure to triangular nano-pyramidal structure at higher ion fluence is investigated in details. It is shown that the chemical nature of the surface changes due to silicon carbide formation at the ion impact sites, and the surface becomes a mixture of Si and SiC. The differential sputtering of Si from pure Si and SiC, generates an additional instability which leads to trigger the ripple pattern on the surface. The variation of height amplitude, lateral correlation length and slope angles of the developed structures are investigated and explained in terms of existing continuum theory. At very high ion fluence the transformation of the structure into three dimensional triangle (octahedron) is revealed and the mechanism is explained in the light of variation of local ion impact angel and its consequent effects.

The ionization state of amino acids on the outer surface of a virus regulates its physicochemical properties toward the sorbent surface. Serologically different strain of dengue virus (DENV) shows different extents of infectivity depending upon their interactions with a receptor on the host cell. To understand the structural dependence of E-protein protonation over its sequence dependence, we have followed E-protein titration kinetics both experimentally and theoretically for two differentially infected dengue serotypes, namely DENV-2 and DENV-4. We have performed an E-protein protonation titration-induced single particle chemical force spectroscopy using an atomic force microscope (AFM) to measure the surface chemistry of DENV in physiological aqueous solutions not only to understand the charge distribution dynamics on virus surface but also to estimate the isoelectric point (pI) accurately for infectious dengue viruses. Cryo-EM structure-based theoretical pI calculations of DENV-2 surface protein were shown to be consistent with the evaluated pI value from force spectroscopy measurements. This is a comprehensive study to understand how the cumulative charge distribution on the outer surface of a specific serotype of DENV regulates a prominent role of infectivity over minute changes at the genetic level.