Density Functional Theory Study on the Cross-Linking of Mussel Adhesive Proteins

Optimizing selectivity via membrane molecular packing manipulation for simultaneous cation and anion screening

Advancing membranes with enhanced solute-solute selectivity is essential for expanding membrane technology applications, yet it presents a notable challenge. Drawing inspiration from the unparalleled selectivity of biological systems, which benefit from the sophisticated spatial organization of functionalities, we posit that manipulating the arrangement of the membrane's building blocks, an aspect previously given limited attention, can address this challenge. We demonstrate that optimizing the face-to-face orientation of building blocks during the assembly of covalent-organic-framework (COF) membranes improves ion-π interactions with multivalent ions. This optimization leads to extraordinary selectivity in differentiating between monovalent cations and anions from their multivalent counterparts, achieving selectivity factors of 214 for K+/Al3+ and 451 for NO3-/PO43-. Leveraging this attribute, the COF membrane facilitates the direct extraction of NaCl from seawater with a purity of 99.57%. These findings offer an alternative approach for designing highly selective membrane materials, offering promising prospects for advancing membrane-based technologies.

Tyrosinase-Modified UHMW SELP Polymers as Wet and Underwater Adhesives to Achieve Multi-interface Adhesion

The presence of a hydration layer in humid and underwater environments challenges adhesive-substrate interactions and prevents effective bonding, which has become a significant obstacle to the development of adhesives in the industrial and biomedical fields. In this study, ultrahigh-molecular-weight (UHMW) silk-elastin-like proteins (SELP) with 3,4-dihydroxyphenylalanine (DOPA) converted from tyrosine residues by tyrosinase exhibited excellent adhesive properties on different interfaces, such as glass, aluminum, wood, polypropylene sheets, and pigskin, under both dry and wet conditions. Additionally, by incorporating trace amounts of cross-linking agents like Fe3+, NaIO4, and tris(hydroxymethyl) phosphine (THP), the mussel-inspired adhesives maintained a stable and excellent adhesion, broadening the conditions of application. Notably, the UHMW SELP adhesive exhibited remarkable underwater adhesion properties with a shear strength of 0.83 ± 0.17 MPa on glass. It also demonstrated good adhesion to biological tissues including the kidney, liver, heart, and lungs. In vitro cytocompatibility testing using L929 cells showed minimal toxicity, highlighting its potential application in the biomedical field. The sustainable, cytocompatible, cost-effective, and highly efficient adhesive provides valuable insights for the design and development of a new protein-based underwater adhesive for medical application.

Machine Learning-Assisted Computational Screening of Adhesive Molecules Derived from Dihydroxyphenyl Alanine

Marine mussels adhere to virtually any surface via 3,4-dihydroxyphenyl-L-alanines (L-DOPA), an amino acid largely contained in their foot proteins. The biofriendly, water-repellent, and strong adhesion of L-DOPA are unparalleled by any synthetic adhesive. Inspired by this, we computationally designed diverse derivatives of DOPA and studied their potential as adhesives or coating materials. We used first-principles calculations to investigate the adsorption of the DOPA derivatives on graphite. The presence of an electron-withdrawing group, such as nitrogen dioxide, strengthens the adsorption by increasing the π-π interaction between DOPA and graphite. To quantify the distribution of electron charge and to gain insights into the charge distribution at interfaces, we performed Bader charge analysis and examined charge density difference plots. We developed a quantitative structure-property relationship (QSPR) model using an artificial neural network (ANN) to predict the adsorption energy. Using the three-dimensional and quantum mechanical electrostatic potential of a molecule as a descriptor, the present quantum NN model shows promising performance as a predictive QSPR model.

Mussel adhesion: A fundamental perspective on factors governing strong underwater adhesion

Protein-based underwater adhesives of marine organisms exhibit extraordinary binding strength in high salinity based on utilizing a variety of molecular interaction mechanisms. These include acid-base interactions, bidentate bindings or complex hydrogen bonding interactions, and electrochemical manipulation of interfacial bonding. In this Perspective, we briefly review recent progress in the field, and we discuss how interfacial electrochemistry can vary interfacial forces by concerted tuning of surface charging, hydration forces, and tuning of the interfacial ion concentration. We further discuss open questions, controversial findings, and new paths into understanding and utilizing redox-proteins and derived polymers for enhancing underwater adhesion in a complex salt environment.

Tunicate-Inspired Photoactivatable Proteinic Nanobombs for Tumor-Adhesive Multimodal Therapy

Near-IR (NIR) light-responsive multimodal nanotherapeutics have been proposed to achieve improved therapeutic efficacy and high specificity in cancer therapy. However, their clinical application is still elusive due to poor biometabolization and short retention at the target site. Here, innovative photoactivatable vanadium-doped adhesive proteinic nanoparticles (NPs) capable of allowing biological photoabsorption and NIR-responsive anticancer therapeutic effects to realize trimodal photothermal-gas-chemo-therapy treatments in a highly biocompatible, site-specific manner are proposed. The photoactivatable tumor-adhesive proteinic NPs can enable efficient photothermal conversion via tunicate-inspired catechol-vanadium complexes as well as prolonged tumor retention by virtue of mussel protein-driven distinctive adhesiveness. The incorporation of a thermo-sensitive nitric oxide donor and doxorubicin into the photoactivatable adhesive proteinic NPs leads to synergistic anticancer therapeutic effects as a result of photothermal-triggered "bomb-like" multimodal actions. Thus, this protein-based phototherapeutic tumor-adhesive NPs have great potential as a spatiotemporally controllable therapeutic system to accomplish effective therapeutic implications for the complete ablation of cancer.

A density functional theory study on the underwater adhesion of catechol onto a graphite surface

Mussel foot proteins (MFPs) strongly adhere to both hydrophilic and hydrophobic surfaces under wet conditions. This water-resistant adhesion of MFP is ascribed to catechol (1,2-dihydroxybenzene) which is highly contained in the MFP. Currently, little is known about the molecular details of the underwater adhesion of catechol onto a nonpolar hydrophobic surface. By using the density functional theory, we investigate the adhesion of catechol onto a wet graphite surface. We unveil the molecular geometry and energy in the course of the wet adhesion of catechol. Catechol adheres through π-π stacking with the underlying graphite. The surrounding water molecules further strengthen the adhesion by forming hydrogen bonds with catechol. In addition, a significant charge transfer has been observed from wet graphite to the catechol. Consequently, catechol adheres onto the present hydrophobic surface as strongly as onto a hydrophilic silica surface.

First principles modeling of polymer encapsulant degradation in Si photovoltaic modules

An outstanding issue in the longevity of photovoltaic (PV) modules is the accelerated degradation caused by the presence of moisture. Moisture leads to interfacial instability, de-adhesion, encapsulant decomposition, and contact corrosion. However, experimental characterization of moisture in PV modules is not trivial and its impacts can take years or decades to establish in the field, presenting a major obstacle to designing high-reliability modules. First principles calculations provide an alternative way to study the ingress of water and its detrimental effect on the structure and decomposition of the polymer encapsulant and interfaces between the encapsulant and the semiconductor, the metal contacts, or the dielectric layer. In this work, we use density functional theory (DFT) computations to model single chain, crystalline and cross-linked structures, infrared (IR) signatures, and degradation mechanisms of ethylene vinyl acetate (EVA), the most common polymer encapsulant used in Si PV modules. IR-active modes computed for low energy EVA structures and possible decomposition products match well with reported experiments. The EVA decomposition energy barriers computed using the Nudged Elastic Band (NEB) method show a preference for acetic acid formation as compared to acetaldehyde, are lowered in the presence of a water solvent or hydroxyl ion catalyst, and match well with reported experimental activation energies. This systematic study leads to a clear picture of the hydrolysis-driven decomposition of EVA in terms of energetically favorable mechanisms, possible intermediate structures, and IR signatures of reactants and products.

A DFT study on the metal ion selectivity of deferiprone complexes

In this work, systematic density functional theory (DFT) calculations were performed to study the interactions of various metal ions (Al³⁺, Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, and Zn²⁺) and the clinically useful chelating agent called deferiprone (DFP) at the M05-2X/6-31G(d) level of theory. The thermodynamic parameters of metal-deferiprone complexes were determined in water. Based on the obtained data, the theoretical binding energy trend is as follows: Al³⁺ > Fe³⁺ > Cu²⁺ > Ni²⁺ > Co²⁺ > Zn²⁺, confirming that [Al(DFP)₃] has the most interaction energy. Moreover, Natural bond orbital analysis was employed to determine and analyze the natural charges on different atoms and charge transfer between the metal ions and ligands (oxygen atoms) as well as the interaction energy (E(2)) values. The calculated value of ƩE(2) (donor-acceptor interaction energy) for [Al(DFP)₃] complex is higher than other complexes, which is according to energy analysis. To confirm the type of effective interactions and bonding properties in the water, the quantum theory of atoms in molecules (QTAIM) analysis was applied. QTAIM analysis confirmed that the strongest M - O bond is found in the [Al(DFP)₃] complex. The calculated topological properties at the bond critical points, such as the ratio of the kinetic energy density to the potential energy density, -G(r)/V(r), electronic energy density, H(r), confirm that M - O bonds in the Al-deferiprone complex are non-covalent, while in other complexes, they are electrostatic and partially covalent.

Ironing out pyoverdine's chromophore structure: serendipity or design?

Pyoverdines are Pseudomonas aeruginosa's primary siderophores. These molecules, composed of a fluorescent chromophore attached to a peptide chain of 6-14 amino acids, are synthesized by the bacterium to scavenge iron (essential to its survival and growth) from its environment. Hijacking the siderophore pathway to use pyoverdine-antibiotic compounds in a Trojan horse approach has shown promise but remains very challenging because of the synthetic efforts involved. Indeed, both possible approaches (grafting an antibiotic on pyoverdine harvested from Pseudomonas or designing a total synthesis route) are costly, time-consuming and low-yield tasks. Designing comparatively simple analogs featuring the salient properties of the original siderophore is thus crucial for the conception of novel antibiotics to fight bacterial resistance. In this work, we focus on the replacement of the pyoverdine chromophore, a major roadblock on the synthetic pathway. We propose three simpler analogs and evaluate their ability to complex iron and interact with the FpvA transporter using molecular modeling techniques. Based on these results, we discuss the role of the native chromophore's main features (polycyclicity, positive charge, flexibility) on pyoverdine's ability to bind iron and be recognized by membrane transporter FpvA and propose guidelines for the design of effective synthetic siderophores.

Fabrication of silica nanoparticle based polymer nanocomposites via a combination of mussel inspired chemistry and SET-LRP

A facile and efficient strategy combination of mussel inspired chemistry and SET-LRP has been developed for the surface modification of silica nanoparticles.

Density functional theory and experimental studies of caffeic acid adsorption on zinc oxide and titanium dioxide nanoparticles

The outstanding adsorption properties of proteins, containing catecholic amino acid, 1,3,4-dihydroxyphenylalanine, and recent advances in nanoparticle functionalization using catecholates have generated interest in catecholate adsorption.