Mussel Adhesion Research Articles

Solvent‐Free Mussel‐Inspired Adhesive with Rapid Underwater Curing Capability

AbstractHow to realize fast and strong underwater adhesion has gained much attention recently. Although some mussel‐inspired adhesives that can be cured underwater have been reported, reports on underwater adhesion with both high bonding strength and rapid curing capability are still rare. Furthermore, organic solvents are generally utilized in these adhesives, which are eco‐unfriendly. Here, by taking advantages of the strong underwater adhesion capability of catecholic groups in mussel adhesion proteins (MAPs) and the fast curing capability of polyurethane (PU) prepolymer, a facile yet powerful strategy towards a fast‐curing mussel‐inspired underwater adhesive is reported. The biomimetic adhesive, PUP‐PPG‐DBHP, is a liquid composed of isocyanate‐terminated polypropylene glycol (PPG) and isocyanate‐terminated dopamine bis(hydroxymethyl)propionate (DBHP), which can be directly applied underwater without solvent dilution and reach an average bonding strength around 1.2 MPa at a curing time of only around 30 s on glass substrates. Meanwhile, underwater curing process of PUP‐PPG‐DBHP shows good tolerance toward pH value, ionic strength, and temperature change. Such an engineering adhesive opens an innovative and facile route to a feasible solution for underwater engineering field.

Oriented in situ immobilization of a functional tyrosinase on microcrystalline cellulose effectively incorporates DOPA residues in bioengineered mussel adhesive protein.

Catechol-containing polymers such as mussel adhesive proteins (MAPs) are attractive as biocompatible adhesive biomaterials, and the catecholic amino acid 3,4-dihydroxyphenyl-L-alanine (DOPA) is considered a key molecule in underwater mussel adhesion. Tyrosinases can specifically convert tyrosine to DOPA without any cofactors. However, their catalytic properties still need to be adjusted to minimize unwanted DOPA oxidation via their diphenolase activity and catechol instability at neutral and basic pH values in the reaction products. In this work, we constructed a novel functional tyrosinase, mTyr-CNK_CBM, by fusion of mTyr-CNK with a cellulose-binding motif (CBM) for oriented in situ immobilization on microcrystalline cellulose via the C-terminal CBM without any additional purification steps. mTyr-CNK_CBM showed optimal catalytic activity at pH 4.5-6.5 and room temperature and had a high monophenolase/diphenolase activity ratio (Vmax mono/Vmax di = 2.08 at pH 6 and 25°C). mTyr-CNK_CBM exhibited 2.17-fold higher (as a unimmobilized free enzyme) and similarly high (upon immobilization) in vitro DOPA modification of a bioengineered MAP compared to a commercially available mushroom tyrosinase. Moreover, the immobilized mTyr-CNK_CBM showed long-term storability and improved reusability. These results clearly demonstrate a strong potential for practical use of immobilized mTyr-CNK_CBM as a monophenol monooxygenase in preparing biocompatible DOPA-tethered biomaterials and other catechol-containing polymers.

Segregated Protein-Cucurbit[7]uril Crystalline Architectures via Modulatory Peptide Tectons.

One approach to protein assembly involves water‐soluble supramolecular receptors that act like glues. Bionanoarchitectures directed by these scaffolds are often system‐specific, with few studies investigating their customization. Herein, the modulation of cucurbituril‐mediated protein assemblies through the inclusion of peptide tectons is described. Three peptides of varying length and structural order were N‐terminally appended to RSL, a β‐propeller building block. Each fusion protein was incorporated into crystalline architectures mediated by cucurbit[7]uril (Q7). A trimeric coiled‐coil served as a spacer within a Q7‐directed sheet assembly of RSL, giving rise to a layered material of varying porosity. Within the spacer layers, the coiled‐coils were dynamic. This result prompted consideration of intrinsically disordered peptides (IDPs) as modulatory tectons. Similar to the coiled‐coil, a mussel adhesion peptide (Mefp) also acted as a spacer between protein–Q7 sheets. In contrast, the fusion of a nucleoporin peptide (Nup) to RSL did not recapitulate the sheet assembly. Instead, a Q7‐directed cage was adopted, within which disordered Nup peptides were partially “captured” by Q7 receptors. IDP capture occurred by macrocycle recognition of an intrapeptide Phe‐Gly motif in which the benzyl group was encapsulated by Q7. The modularity of these protein–cucurbituril architectures adds a new dimension to macrocycle‐mediated protein assembly. Segregated protein crystals, with alternating layers of high and low porosity, could provide a basis for new types of materials.

A Universal and Reversible Wet Adhesive via Straightforward Aqueous Self-Assembly of Polyethylenimine and Polyoxometalate.

The excellent adhesion of mussels under wet conditions has inspired the development of numerous catechol-based wet adhesives. Nevertheless, the performance of catechol-based wet adhesive suffers from the sensitivity toward temperature, pH, or oxidation stimuli. Therefore, it is of great significance to develop non-catechol-based wet adhesives to fully recapitulate nature's dynamic function. Herein, a novel type of non-catechol-based wet adhesive is reported, which is readily formed by self-assembly of commercially available branched polyethylenimine and phosphotungstic acid in aqueous solution through the combination of electrostatic interaction and hydrogen bonding. This wet adhesive shows reversible, tunable, and strong adhesion on diverse substrates and further exhibits high efficacy in promoting biological wound healing. During the healing of the wound, the as-prepared wet adhesive also possesses inherent antimicrobial properties, thus avoiding inflammations and infections due to microorganism accumulation.

Molecular Context of Dopa Influences Adhesion of Mussel-Inspired Peptides.

Improving adhesives for wet surfaces is an ongoing challenge. While the adhesive proteins of marine mussels have inspired many synthetic wet adhesives, the mechanisms of mussel adhesion are still not fully understood. Using surface forces apparatus (SFA) measurements and replica-exchange and umbrella-sampling molecular dynamics simulations, we probed the relationships between the sequence, structure, and adhesion of mussel-inspired peptides. Experimental and computational results reveal that peptides derived from mussel foot protein 3 slow (mfp-3s) containing 3,4-dihydroxyphenylalanine (Dopa), a post-translationally modified variant of tyrosine commonly found in mussel foot proteins, form adhesive monolayers on mica. In contrast, peptides with tyrosine adsorb as weakly adhesive clusters. We further considered simulations of mfp-3s derivatives on a range of hydrophobic and hydrophilic organic and inorganic surfaces (including silica, self-assembled monolayers, and a lipid bilayer) and demonstrated that the chemical character of the target surface and proximity of cationic and hydrophobic residues to Dopa affect peptide adsorption and adhesion. Collectively, our results suggest that conversion of tyrosine to Dopa in hydrophobic, sparsely charged peptides influences peptide self-association and ultimately dictates their adhesive performance.

Liquid-Liquid Phase Separation of the Green Mussel Adhesive Protein Pvfp-5 is Regulated by the Post-Translated Dopa Amino Acid.

The underwater adhesive prowess of aquatic mussels has been largely attributed to the abundant post-translationally modified amino acid l-3,4-dihydroxyphenylalanine (Dopa) in mussel foot proteins (MFPs) that make up their adhesive threads. More recently, it has been suggested that during thread fabrication, MFPs form intermediate fluidic phases such as liquid crystals or coacervates regulated by a liquid-liquid phase separation (LLPS) process. Here, it is shown that Dopa plays another central role during mussel fiber formation, by enabling LLPS of Pvfp-5β, a main MFP of the green mussel Perna viridis. Using residue-specific substitution of Tyrosine (Tyr) for Dopa during recombinant expression, Dopa-substituted Pvfp-5β is shown to exhibit LLPS under seawater-like conditions, whereas the Tyr-only version forms insoluble aggregates. Combining quantum chemistry calculations and solution NMR, a transient H-bonding network requiring the two hydroxyl groups of Dopa is found to be critical to enable LLPS in Dopa-mutated Pvfp-5β. Overall, the study suggests that Dopa plays an important role in regulating LLPS of MFPs, which may be critical to concentrate the adhesive proteins at the plaque/substrate interface and therefore produce a more robust adhesive. The findings also provide molecular-level lessons to guide biomanufacturing of protein-based materials such as bioadhesives and load-bearing fibers.

Antibacterial Gel Coatings Inspired by the Cryptic Function of a Mussel Byssal Peptide

Although the adhesive and cohesive nature of mussel byssal proteins have long served to inspire the design of materials embodying these properties, their characteristic amino acid compositions suggest that they might also serve to inspire an unrelated material function not yet associated with this class of protein. Herein, it is demonstrated that a peptide derived from mussel foot protein-5, a key protein in mussel adhesion, displays antibacterial properties, a yet unreported activity. This cryptic function serves as inspiration for the design of a new class of peptide-based antibacterial adhesive hydrogels prepared via self-assembly, which are active against drug-resistant Gram-positive bacteria. The gels exert two mechanisms of action, surface-contact membrane disruption and oxidative killing affected by material-produced H2 O2 . Detailed studies relating amino acid composition and sequence to material mechanical adhesion/cohesion and antibacterial activity affords the MIKA2 adhesive gel, a material with a superior activity that is shown to inhibit colonization of titanium implants in mice.

Rational integration of defense and repair synergy on PEEK osteoimplants via biomimetic peptide clicking strategy

Polyetheretherketone (PEEK) has been widely used as orthopedic and dental materials due to excellent mechanical and physicochemical tolerance. However, its biological inertness, poor osteoinduction, and weak antibacterial activity make the clinical applications in a dilemma. Inspired by the mussel adhesion mechanism, here we reported a biomimetic surface strategy for rational integration and optimization of anti-infectivity and osteo-inductivity onto PEEK surfaces using a mussel foot proteins (Mfps)-mimic peptide with clickable azido terminal. The peptide enables mussel-like adhesion on PEEK biomaterial surfaces, leaving azido groups for the further steps of biofunctionalizations. In this study, antimicrobial peptide (AMP) and osteogenic growth peptide (OGP) were bioorthogonally clicked on the azido-modified PEEK biomaterials to obtain a dual-effect of host defense and tissue repair. Since bioorthogonal clicking allows precise collocation between AMP and OGP through changing their feeding molar ratios, an optimal PEEK surface was finally obtained in this research, which could long-term inhibit bacterial growth, stabilize bone homeostasis and facilitate interfacial bone regeneration. In a word, this upgraded mussel surface strategy proposed in this study is promising for the surface bioengineering of inert medical implants, in particular, achieving rational integration of multiple biofunctions to match clinical requirements.

Mussel Adhesive Mimetic Silk Sericin Prepared by Enzymatic Oxidation for the Construction of Antibacterial Coatings.

With the rapid development and advancement in orthodontic and orthopedic technologies, the demand for biomedical-grade titanium (Ti) alloys is growing. The Ti-based implants are susceptible to bacterial infections, leading to poor healing and osteointegration, resulting in implant failure or repeated surgical intervention. Silk sericin (SS) is hydrophilic, biocompatible, and biodegradable and could induce a low immunological response in vivo. As a result, it would be intriguing to investigate the use of hydrophilic SS in surface modification. In this work, the tyrosine moiety in SS was oxidized by tyrosinase (or polyphenol oxidase) to the 3,4-dihydroxyphenylalanine (DOPA) form, generating the catechol moiety-containing SS (SSC). Inspired by the adhesion of mussel foot proteins, the SSC coatings could be directly deposited onto multiple surfaces in SS and tyrosinase mixed stock solutions to create active surfaces with catechol groups. Further, the SSC-coated Ti surfaces were hybridized with silver nanoparticles (Ag NPs) via in situ silver ion (Ag+) reduction. The antibacterial properties of the Ag NPs/SS-coated Ti surfaces are demonstrated, and they can prevent bacterial cell adhesion as well as early-stage biofilm formation. In addition, the developed Ag NPs/SSC-coated Ti surfaces exhibited a negligible level of cytotoxicity in L929 mouse fibroblast cells.

The mussel-inspired micro-nano structure for antifouling:A flowering tree

Mussels are typical marine fouling organisms that attach to surfaces though secretions, which is generally the focus of research on mussel-related fouling. This study reveals “a flowering tree” structure on mussel shells with antifouling performance. Based on the antifouling mechanism of surface microstructure, we prepared mussel-like shells (P) using the biomimetic replication method. Mussel adhesion experiments were conducted to examine the anti-mussel performances of the mussel shells and P. The anti-diatom performances of the mussel-like shells were also evaluated using three types of diatoms. The mussels responded differently to different locations on the shells, and the flowering tree microstructure exhibited excellent antifouling performance. In addition, VP (P immersed in vinyl silicon oil) and HP (P immersed in hydroxyl silicone oil) were prepared. The anti-diatom performance of VP was better than those of P and HP, indicating that hydrophobicity has a greater influence on anti-diatom performance than electronegativity. The newly discovered antifouling micro-nano structure was parameterized, revealing that a branch of the flowering tree has an inclination of 13.3° to the surface with a height of 210.1 nm. The results of this study provide insights for further investigations of bionic micro-nano structures in the field of antifouling.

Mussel-Inspired Underwater Adhesives- from Adhesion Mechanisms to Engineering Applications: A Critical Review

Recent progress in the adhesion mechanism of mussels has led to great excitement in the field of adhesive materials. Although great progress has been made in the mussel adhesion mechanism and underwater adhesives, there are still many unknowns and challenges in this area. Thus, it is highly important to review the recent progress in mechanisms of mussel adhesion and mussel-inspired adhesives and predict trends for the future. In this review, we (1) summarize the research progress in fundamental interaction mechanisms in natural mussels; (2) discuss the application of the mussel interaction mechanism in the biomimetic mussel adhesive materials, from permanent/high-strength adhesives to temporary/smart adhesives; (3) briefly state the potential applications of the mussel-inspired adhesives in multiple fields, such as engineering applications, smart robotics and biomedicine; (4) summarize the future perspectives and unsolved challenges of mussel adhesion mechanisms and mussel-inspired adhesive materials. We envision that this review will provide an insightful perspective in understanding the mussel adhesion mechanism and directions to further explore, and promote the development of novel biomimetic mussel adhesive materials.

The Use of Living Mussels as a Substratum for Growing Seedlings of Two Sargassum Species from the Perspective of Coastal Seaweed Bed Restoration in the East China Sea

Sargassum vachellianum and Sargassum horneri are the main dominant species and primary producers of seaweed beds in Chinese coastal ecosystems that play an important role in marine blue carbon sinks. However, due to the influence of frequent human activities and global climate change, the seaweed beds formed by Sargassum vachellianum and Sargassum horneri in Chinese coastal waters are gradually declining. In this study, Sargassum zygotes were cultured onto the surface of mussels and then used to repair the declining seaweed bed resources through seaweed transplantation, which was indirectly achieved based on the fast attachment of mussel byssus. The results show that zygotes of Sargassum vachellianum and Sargassum horneri could grow on the surface of mussels and, over time, the force and rate of mussel adhesion gradually increased. The adhesion of Mytilus coruscus was greater than that of Septifer virgatus mussels. After four hours, the rate of adhesion for Mytilus coruscus with a shell length of 30 mm was 100%, and the adhesion force was the highest, at 0.511 ± 0.099 N. Hence, Mytilus coruscus showed better adhesion than Septifer virgatus. After 41 days, the mean length of Sargassum horneri germlings on the surface of Mytilus coruscus grew to 5.554 ± 0.724 mm, the daily growth rate was about 0.154 mm/d, and the mean density declined by 50.59%. After 31 days, the mean length of Sargassum vachellianum germlings increased to 5.510 ± 0.763 mm, the daily growth rate was about 0.191 mm/d, and the mean density declined by 21.21%. After 2 months of development of the mussel–seaweed combinations in coastal waters, the survival rate of Sargassum horneri was 7.6 ± 0.9% and that of Sargassum vachellianum was 25.9 ± 10.5%. Hence, compared with Sargassum horneri, Sargassum vachellianum attached to Mytilus coruscus showed better development, and this system can be used to combat the decline in seaweed bed resources. In this method, mussels were used as an intermediate attachment medium to indirectly achieve the settlement of zygotes for seaweed transplantation, and, therefore, their use as a substratum serves as the basis for a novel technique for seaweed beds restoration.

Tunicate-inspired polyallylamine-based hydrogels for wet adhesion: A comparative study of catechol- and gallol-functionalities

HypothesisFunctional adhesives with excellent adhesive strength in wet as well as dry environments are actively studied for various applications. In particular, the adhesion mechanism of marine organisms has been imitated to achieve strong adhesion in wet environments. ExperimentsPolyallylamine (PAA) was modified with catechol groups (CA), which mimic the mussel adhesion proteins, and gallol groups (GA) found in tunicates to compare the gelation, self-healing, and adhesive properties of the modified polymers according to pH change. The effect of the Schiff base formation and antioxidant capacity exerted by polyphenolic groups were investigated by comparing the self-healing behaviors of the two hydrogels. Furthermore, the wet adhesion and antibacterial properties of the PAA-CA and PAA-GA hydrogels were evaluated in terms of the synergistic effects of the amino groups and catechol or gallol groups. FindingsThe self-crosslinkable PAA-CA and PAA-GA hydrogels showed high self-healing ability owing to these dynamic imine bonds. Furthermore, the PAA-based hydrogels showed higher adhesive strength in wet environments than in dry environments owing to the synergism between the catechol or gallol groups and amino groups. Overall, the PAA-GA hydrogels are superior to the PAA-CA ones, indicating that gallol-functionalized hydrogels have great potential as multifunctional adhesives.

Tunable interfacial interaction intensity: Construction of a bio-inspired interface between polydopamine and energetic crystals

Polymer bonded explosives (PBXs) have weak strength and toughness, as well as they are prone to fracture under stress. To overcome these disadvantages, inspired by the strong adhesion of mussels and the hierarchical structure of nacre, we designed and fabricated novel PBX composites by coating three explosive crystals (2,6-diamino-3,5-dinitropyrazine-1-oxide, LLM-105; 1,3,5-triamino-2,4,6-trinitrobenzene, TATB; and 1,3,5,7-tetranitro-1,3,5,7-tetrazocane, HMX) with polydopamine (PDA), respectively. The results of mechanical analysis and in situ small angle neutron scattering measurements showed that these novel PBX composites exhibited higher strength, stronger toughness, and higher creep resistance, and higher microstructural thermal stability simultaneously, compared to PBXs without multiple bio-inspired designs. Contact angles measurements indicated that the interfacial interaction intensities between energetic crystals and polymer binder could be largely enhanced by PDA coating on energetic crystals. Theoretical calculations revealed that PDA-modified PBX-LLM-105 achieved the most increment in mechanical strength, which were well consistent with the experiments. An enhancement mechanism combining the van der Waals forces, π–π interaction, and hydrogen bonds, as well as surface roughness was proposed to account for the variety of mechanical properties and microstructural thermal stability of PDA-modified PBXs. The results revealed in this study are commonly significant to interfacial modification and performance enhancement of materials.

Two Faces of Amine–Catechol Pair Synergy in Underwater Cation−π Interactions

Cation−π interactions play important roles in various biological systems. Recently, cation−π interactions have been suggested to have considerable roles in mussel adhesion, which is the most well-k...

Identification of novel adhesive proteins in pearl oyster by proteomic and bioinformatic analysis

Byssuses, which are proteinaceous fibers secreted by mollusks, are remarkable underwater adhesives. Although mussel adhesives are well known, much less is known about the byssal proteins of pearl oysters especially in the adhesive regions. In this study, adhesive proteins from the pearl oyster Pinctada fucata were studied in depth by transcriptomics and proteomics approaches. In total, 16 novel proteins were identified including a von Willebrand factor type A domain-containing protein, a thrombospondin-1-like protein, tyrosinase, mucin-like proteins, protease inhibitors, and Pinctada unannotated foot protein 3 (PUF3) to PUF6. Interestingly, PUF3-6 are enriched with glycine, serine, and PXG (X = F/Y/W/K/L) motifs and are highly expressed in the foot. The identification of byssal proteins of the pearl oyster is a key step for understanding byssus formation and may inspire the synthesis of novel adhesives for underwater use and the development of anti-biofouling strategies.

Thermo-sensitive hydrogel with mussel-inspired adhesion enhanced the non-fibrotic repair effect of EGF on colonic mucosa barrier of TNBS-induced ulcerative colitis rats through macrophage polarizing

Thermo-sensitive hydrogel is preferable to liquid enema for topical treatments of ulcerative colitis (UC). Poly (ethylene oxide)-poly (propylene oxide)-poly-(ethylene oxide) copolymer branded as Poloxamer was commonly used as thermo-sensitive hydrogel material. However, the rapid erosion and poor mucosal adhesion compromised its practical application after rectal infusion. Herein, inspiring the mussel adhesion, dihydrocaffeic acid-modified poloxamer (P-DA) was designed to overcome these drawbacks. Series of P-DA polymers were synthesized by adjusting the feeding amounts of dihydrocaffeic acid (DA). P-DA polymers with suitable DA graft degree still showed the good thermo-sensitive properties. Moreover, P-DA hydrogels displayed the tougher mechanical strength than Poloxamer 407 hydrogel at the equivalent polymer concentration. Accordingly, in vitro erosion of P-DA hydrogel was significantly delayed in pH7.4 PBS (10 mM). Moreover, the stronger tissue adhesion for P-DA hydrogels was also reached. Epidermal growth factor (EGF) as model protein was delivered by P-DA hydrogels (P-DA-EGF). The stability of EGF was obviously improved by P-DA hydrogels. Moreover, the colonic retention of P-DA hydrogels was significantly prolonged in comparison with Poloxamer 407 hydrogel, leading to a higher mucosal absorption of EGF after their rectal infusion. In vivo animal studies showed that P-DA hydrogels also significantly improved the therapeutic effect of EGF on TNBS-induced ulcerative colitis rats. The colonic morphology and function of goblet cells were obviously restored by P-DA-EGF hydrogels. Moreover, the colonic mucosal healing was not orchestrated with the colonic fibrosis. The mechanism of the colonic mucosal barrier repairing for P-DA-EGF hydrogels was highly associated with polarizing macrophages from an inflammatory (M1) to anti-inflammatory (M2) phenotype. Collectively, the designed mussel-inspired P-DA hydrogel may be a promising system for the rectal delivery of therapeutic proteins.

Surface bioengineering of diverse orthopaedic implants with optional functions via bioinspired molecular adhesion and bioorthogonal conjugations

In this work, we reported an upgraded mussel-inspired strategy for surface bioengineering of osteoimplants by combination of mussel adhesion and bioorthogonal click chemistry. The main idea of this strategy is a mussel-inspired synthetic peptide containing multiple 3,4-dihydroxy-L-phenylalanine (DOPA) units and a dibenzocyclooctyne (DBCO) terminal (DOPA-DBCO). According to the mussel adhesion mechanism, the DOPA-DBCO peptide could stably adhere onto a variety of material surface, leaving the residual DBCO groups on the surface. Then, the DBCO residues could be employed for a second-step bioorthogonal conjugation with azide-capping biomolecules through bioorthogonal click chemistry, finally leading to the biomodified surfaces. To demonstrate the generality of our strategy for surface biomodification of diversified orthopaedic materials including metallic and polymeric substrates, we here conceptually conjugated some typical azide-capping biomolecules on both metal and polymeric surfaces. The results definitely verified the feasibility for engineering of functional surfaces with some essential requirements of osteoimplants, for example, the ability to facilitate cell adhesion, suppress bacterial infection, and promote osteogenesis. In a word, this study indicated that our novel surface strategy would show broad applicability for diverse osteoimplants and in different biological scenarios. We can also image that the molecular specificity of bioorthogonal conjugation and the universality of mussel adhesion mechanism may jointly provide a versatile surface bioengineering method for a wider range of biomedical implants.

Exploring the Mesoscopic Morphology in Mussel Adhesive Proteins by Soft X-ray Spectromicroscopy.

Marine mussels efficiently adhere under wet conditions by precisely controlling the hierarchical structure of the adhesive plaque through sequential mussel foot protein secretion in the foot-tip cavity. Chemical analysis of the non-uniform mussel plaque morphology has been performed using spectromicroscopy; however, the mesoscopic morphology has not been elucidated yet because of the limited spatial resolution of conventional chemical imaging techniques. We investigated the chemical speciation in the non-uniform mussel plaque morphology employing scanning transmission soft X-ray spectromicroscopy (STXM). The high-spatial-resolution STXM chemical imaging with C 1s near-edge X-ray absorption fine structure yields the distribution of the hydroxy-substituted aromatic residues in the sub-micron scale non-uniform mussel plaque morphology. The matrix consists of a high-protein-density cured product containing a large number of hydroxy-substituted aromatic carbons, including tyrosine and 3,4-dihydroxyphenylalanine (Dopa), whereas the microdomains are poor-protein-density regions with a low aromatic residue relative content. The adhesive interface was covered with the matrix phase to ensure adhesion. The cuticle layer involves a moderate Dopa content, which appears to be optimized for the mechanical performance of the skin.

An Individual Amino Acid as a Possible Prebiotic Catalyst

AbstractBetter understanding how reactions have been catalyzed in the prebiotic world is important for better realizing how enzymes have evolved. The dominant hypothesis is that the first catalyst was an RNA molecule. It was also assumed that amyloid fibrils, self‐assembled by peptides or proteins, served as the first catalysts. However, debate still exists regarding which process occurred first: the polymerization of RNA or the synthesis of proteins. Here, we show that an individual amino acid, L‐3,4‐dihydroxyphenylalanine (DOPA), can act as a catalyst. This amino acid is the main constituent of mussel adhesion proteins that function in harsh conditions very similar to plausible prebiotic conditions. By tracing the hydrolysis of two compounds, p‐nitrophenylacetate and acetylcholine, we showed that DOPA catalyzes a reaction; we suggest its role as a prebiotic catalyst.