Size and surface chemistry of nanoparticles lead to a variant behavior in the unfolding dynamics of human carbonic anhydrase

Abstract

The adsorption induced conformational changes of human carbonic anhydrase I (HCAi) and pseudo wild type human carbonic anhydrase II truncated at the 17th residue at the N-terminus (trHCAii) were studied in presence of nanoparticles of different sizes and polarities. Isothermal titration calorimetry (ITC) studies showed that the binding to apolar surfaces is affected by the nanoparticle size in combination with the inherent protein stability. 8-Anilino-1-naphthalenesulfonic acid (ANS) fluorescence revealed that HCAs adsorb to both hydrophilic and hydrophobic surfaces, however the dynamics of the unfolding at the nanoparticle surfaces drastically vary with the polarity. The size of the nanoparticles has opposite effects depending on the polarity of the nanoparticle surface. The apolar nanoparticles induce seconds timescale structural rearrangements whereas polar nanoparticles induce hours timescale structural rearrangements on the same charged HCA variant. Here, a simple model is proposed where the difference in the timescales of adsorption is correlated with the energy barriers for initial docking and structural rearrangements which are firmly regulated by the surface polarity. Near-UV circular dichorism (CD) further supports that both protein variants undergo structural rearrangements at the nanoparticle surfaces regardless of being "hard" or "soft". However, the conformational changes induced by the apolar surfaces differ for each HCA isoform and diverge from the previously reported effect of silica nanoparticles.

Interaction of single and multi wall carbon nanotubes with the biological systems: tau protein and PC12 cells as targets

“…We noted that SWCNT displays value of K SV higher than MWCNT assigning further evidence for static quenching (protein-CNT complex formation) of SWCNT relative to MWCNT 37 . The obtained data strongly indicates that SWCNT bind to tau protein stronger than MWCNT to form protein-CNT system 40 .…”

“…The main reason for this is the increase in interaction between hydrophilic surfaces and hydrophilic moiety of proteins and nanoparticle that are exposed during interaction. Interfacial water is then strongly bound to the contacting hydrophilic surfaces compared to same process on hydrophobic surfaces with weaker water binding 36 37 .…”

“…Far UV-CD (190–250 nm) and the near UV-CD (240–320 nm) spectra can sensitively monitor secondary and tertiary conformation changes of proteins upon interaction with the nanoparticles, respectively 37 . The far UV-CD of tau exhibits a minimum close to 195 nm corresponding to a mostly random coil structure of tau soluble protein 38 .…”

Kinetic and thermodynamic study of the interactions between human carbonic anhydrase variants and polystyrene nanoparticles of different size

“…In a previous work we have proposed a model to explain the effect of PSCOOH on the dynamics of adsorption of trHCAII and HCAI. 26 According to that, lateral repulsive interactions between adsorbed proteins are geometrically minimized due to the increase of particle curvature. This reduction of repulsive forces helps the protein to pack more densely and therefore increase the coverage as shown in the case of HCAI and trHCAII.…”

Charge-transfer interactions induce surface dependent conformational changes in apolipoprotein biocorona

“…Proteins with a stronger affinity to the ENM core can quickly displace the initially present functional groups and be irreversibly immobilized on the ENM surface by partial or complete denaturation [13,15,22]. A combination of many factors including van der Waals forces, hydrogen bridges, charge transfer and other hydrophobic interactions are known to drive protein denaturation [23][24][25][26]. Such factors naturally depend upon ENM physicochemical properties.…”