BRCA1 (Breast Cancer-Associated Protein 1) is a human tumor suppressor that functions as an ubiquitin (Ub) ligase enzyme (E3) and plays a key role in genomic stability and DNA repair....

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Water condensation plays a major role in a wide range of industrial applications. Over the past few years, many studies have shown interest in designing surfaces with enhanced water condensation and removal properties. It is well known that heterogeneous nucleation outperforms homogeneous nucleation in the condensation process. Because heterogeneous nucleation initiates on a surface at a small scale, it is highly desirable to characterize water-surface interactions at the molecular level. Molecular dynamics (MD) simulations can provide direct insight into heterogeneous nucleation and advance surface designs. Existing MD simulations of water condensation on surfaces were conducted by tuning the solid-water van der Waals interaction energy as a substitute for modeling surfaces with different wettabilities. However, this approach cannot reflect the real intermolecular interactions between the surface and water molecules. Here, we report MD simulations of water condensation on realistic surfaces of alkanethiol self-assembled monolayers with different head group chemistries. We show that decreasing surface hydrophobicity significantly increases the electrostatic forces between water molecules and the surface, thus increasing the water condensation rate. We observe a strong correlation between our rate of condensation results and the results from other surface characterization metrics, such as the interfacial thermal conductance, contact angle, and the molecular-scale wettability metric of Garde and co-workers. This work provides insight into the water condensation process at the molecular scale on surfaces with tunable wettability.

Due to its excellent chemical and mechanical properties, titanium has become the material of choice for orthopedic and dental implants to promote rehabilitation via bone anchorage and osseointegration. Titanium osseointegration is partially related to its capability to form a TiO 2 surface layer and its ability to interact with key endogenous proteins immediately upon implantation, establishing the first bone−biomaterial interface. Surgical trauma caused by implantation results in the release of high-mobility group box 1 (HMGB1) protein, which is a prototypic DAMP (damage-associated molecular pattern) with multiple roles in inflammation and tissue healing. To develop different surface strategies that improve the clinical outcome of titanium-based implants by controlling their biological activity, a molecular-scale understanding of HMGB1−surface interactions is desired. Here, we use molecular dynamics (MD) computer simulations to provide direct insight into the HMGB1 interactions and the possible molecular arrangements of HMGB1 on fully hydroxylated and nonhydroxylated rutile (110) TiO 2 surfaces. The results establish that HMGB1 is most likely to be adsorbed directly onto the surface regardless of surface hydroxylation, which is undesirable because it could affect its biological activity by causing structural changes to the protein. The hydroxylated TiO 2 surface shows a greater affinity for HMGB1 than the nonhydroxylated surface. The water layer on the nonhydroxylated TiO 2 surface prevents ions and the protein from directly contacting the surface. However, it was observed that if the ionic strength increases, the total number of ions adsorbed on the two surfaces increases and the protein's direct adsorption ability decreases. These findings will help to understand the HMGB1− TiO 2 interactions upon implantation as well as the development of different surface strategies by introducing ions or ionic materials to the titanium implant surface to modulate its interactions with HMGB1 to preserve biological function.

<div><div><div><p>Due to its excellent chemical and mechanical properties, titanium has become the material of choice for orthopedic and dental implants to promote rehabilitation via bone anchorage and osseointegration. Titanium osseointegration is partially related to its capability to form a TiO₂ surface layer and its ability to interact with key endogenous proteins immediately upon implantation, establishing the first bone-biomaterial interface. Surgical trauma caused by implantation results in the release of High Mobility Group Box 1 (HMGB1) protein, which is a prototypic DAMP (Damage Associated Molecular Pattern) with multiple roles in inflammation and tissue healing. To develop different surface strategies that improve the clinical outcome of titanium-based implants by controlling their biological activity, a molecular-scale understanding of HMGB1-surface interactions is desired. Here, we use molecular dynamics (MD) computer simulations to provide direct insight into the HMGB1 interactions and the possible molecular arrangements of HMGB1 on fully hydroxylated and non-hydroxylated rutile (110) TiO₂ surfaces. The results establish that HMGB1 is most likely to be adsorbed directly onto the surface regardless of surface hydroxylation, which is undesirable because it could affect its biological activity by causing structural changes to the protein. The hydroxylated TiO₂ surface shows a greater affinity for HMGB1 than the non-hydroxylated surface. The water layer on the non-hydroxylated TiO₂ surface prevents ions and the protein from directly contacting the surface. However, it was observed that if the ionic strength increases, the total number of ions adsorbed on the two surfaces increases, and the protein’s direct adsorption ability decreases. These findings will help to understand the HMGB1-TiO₂ interactions upon implantation, as well as the development of different surface strategies by introducing ions or ionic materials to the titanium implant surface to modulate its interactions with HMGB1 to preserve biological function.</p></div></div></div>