Three-dimensional structure of Megabalanus rosa Cement Protein 20 revealed by multi-dimensional NMR and molecular dynamics simulations

Strong Bioadhesives from Helical Polypeptides

Bioadhesives have emerged as versatile and powerful tools for tissue repair and integration with biomedical devices, offering a wide range of applications that have captured significant clinical and scientific interest. Synthetic polypeptide adhesives are particularly promising candidates for bioadhesives, but often face limitations in adhesive strength. In this study, inspired by marine adhesive proteins, the secondary structure and hydrophobic-hydrophilic balance of polypeptides were precisely regulated to transform the polyelectrolyte to a strong adhesive. The resulting polypeptide adhesive demonstrated an adhesive strength exceeding 1.0 MPa, more than 10× higher than that of the previously reported synthetic polypeptide adhesive. The cohesion and adhesion of polypeptide adhesive can be optimized by adjusting the content of the secondary structure and hydrophobic residue ratios. More helices in polypeptides enhance the interactions between the polypeptide backbone and side chains as well as the interactions between polypeptides and substrates. In addition, these polypeptide adhesives exhibit excellent tolerance to strong acids or alkalis, remarkable adhesion to variable materials and tissues, and an impressive sealing performance.

How to drug a cloud? Targeting intrinsically disordered proteins

Biologically active proteins/regions without stable structure (i.e., intrinsically disordered proteins and regions (IDPs and IDRs)) are commonly found in all proteomes. They have a unique functional repertoire that complements the functionalities of ordered proteins and domains. IDPs/IDRs are multifunctional promiscuous binders capable of folding at interaction with specific binding partners on a template- or context-dependent manner, many of which undergo liquid-liquid phase separation, leading to the formation of membrane-less organelles and biomolecular condensates. Many of them are frequently related to the pathogenesis of various human diseases. All this defines IDPs/IDRs as attractive targets for the development of novel drugs. However, their lack of unique structures, multifunctionality, binding promiscuity, and involvement in unusual modes of action preclude direct use of traditional structure-based drug design approaches for targeting IDPs/IDRs, and make disorder-based drug discovery for these "protein clouds" challenging. Despite all these complexities there is continuing progress in the design of small molecules affecting IDPs/IDRs. This article describes the major structural features of IDPs/IDRs and the peculiarities of the disorder-based functionality. It also discusses the roles of IDPs/IDRs in various pathologies, and shows why the approaches elaborated for finding drugs targeting ordered proteins cannot be directly used for the intrinsic disorder-based drug design, and introduces some novel methodologies suitable for these purposes. Finally, it emphasizes that regardless of their multifunctionality, binding promiscuity, lack of unique structures, and highly dynamic nature, "protein clouds" are principally druggable. Significance Statement Intrinsically disordered proteins and regions are highly abundant in nature, have multiple important biological functions, are commonly involved in the pathogenesis of a multitude of human diseases, and are therefore considered as very attractive drug targets. Although dealing with these unstructured multifunctional protein/regions is a challenging task, multiple innovative approaches have been designed to target them by small molecules.

Computer-aided discovery of novel SmDHODH inhibitors for schistosomiasis therapy: Ligand-based drug design, molecular docking, molecular dynamic simulations, drug-likeness, and ADMET studies

Schistosomiasis, also known as bilharzia or snail fever, is a tropical parasitic disease resulting from flatworms of the Schistosoma genus. This often overlooked disease has significant impacts in affected regions, causing enduring morbidity, hindering child development, reducing productivity, and creating economic burdens. Praziquantel (PZQ) is currently the only treatment option for schistosomiasis. Given the potential rise of drug resistance and the limited treatment choices available, there is a need to develop more effective inhibitors for this neglected tropical disease (NTD). In view of this, quantitative structure-activity relationship studies (QSAR), molecular docking, molecular dynamics simulations, drug-likeness, and ADMET predictions were applied to 31 inhibitors of Schistosoma mansoni Dihydroorotate dehydrogenase (SmDHODH). The designed QSAR model demonstrated robust statistical parameters including an R2 of 0.911, R2adj of 0.890, Q2cv of 0.686, R2pred of 0.807, and cR2p of 0.825, confirming its robustness. Compound 26, identified as the most active derivative, emerged as a lead candidate for new potential inhibitors through ligand-based drug design. Subsequently, 12 novel compounds (26A-26L) were designed with enhanced inhibition activity and binding affinity. Molecular docking studies revealed strong and stable interactions, including hydrogen bonding and hydrophobic interactions, between the designed compounds and the target receptor. Molecular dynamics simulations over 100 nanoseconds and MM-PBSA free binding energy (ΔGbind) calculations validated the stability of the two best-designed molecules (26A and 26L). Furthermore, drug-likeness and ADMET prediction analyses affirmed the potential of these designed compounds, suggesting their promise as innovative agents for treating schistosomiasis.

Non-fibril amyloid aggregation at the air/water interface: self-adaptive pathway resulting in a 2D Janus nanofilm

The amyloid states of proteins are implicated in several neurodegenerative diseases and bioadhesion processes. However, the classical amyloid fibrillization mechanism fails to adequately explain the formation of polymorphic aggregates and their adhesion to various surfaces. Herein, we report a non-fibril amyloid aggregation pathway, with disulfide-bond-reduced lysozyme (R-Lyz) as a model protein under quasi-physiological conditions. Very different from classical fibrillization, this pathway begins with the air-water interface (AWI) accelerated oligomerization of unfolded full-length protein, resulting in unique plate-like oligomers with self-adaptive ability, which can adjust their conformations to match various interfaces such as the asymmetric AWI and amyloid-protein film surface. The pathway enables a stepwise packing of the plate-like oligomers into a 2D Janus nanofilm, exhibiting a divergent distribution of hydrophilic/hydrophobic residues on opposite sides of the nanofilm. The resulting Janus nanofilm possesses a top-level Young's modulus (8.3 ± 0.6 GPa) among amyloid-based materials and exhibits adhesive strength two times higher (145 ± 81 kPa) than that of barnacle cement. Furthermore, we found that such an interface-directed pathway exists in several amyloidogenic proteins with a similar self-adaptive 2D-aggregation process, including bovine serum albumin, insulin, fibrinogen, hemoglobin, lactoferrin, and ovalbumin. Thus, our findings on the non-fibril self-adaptive mechanism for amyloid aggregation may shed light on polymorphic amyloid assembly and their adhesions through an alternative pathway.

Adaptive Adhesions of Barnacle-Inspired Adhesive Peptides

The strategy of robust adhesion employed by barnacles renders them fascinating biomimetic candidates for developing novel wet adhesives. Particularly, barnacle cement protein 19k (cp19k) has been speculated to be the key adhesive protein establishing the priming layer in the initial barnacle cement construction. In this work, we systematically studied the sequence design rationale of cp19k by designing adhesive peptides inspired by the low-complexity STGA-rich and the charged segments of cp19k. Combining structure analysis and the adhesion performance test, we found that cp19k-inspired adhesive peptides possess excellent disparate adhesion strategies for both hydrophilic mica and hydrophobic self-assembled monolayer surfaces. Specifically, the low-complexity STGA-rich segment offers great structure flexibility for surface adhesion, while the hydrophobic and charged residues can contribute to the adhesion of the peptides on hydrophobic and charged surfaces. The adaptive adhesion strategy identified in this work broadens our understanding of barnacle adhesion mechanisms and offers valuable insights for designing advanced wet adhesives with exceptional performance on various types of surfaces.

Biomineralization in Barnacle Base Plate in Association with Adhesive Cement Protein

Barnacles strongly attach to various underwater substrates by depositing and curing a proteinaceous cement that forms a permanent adhesive layer. The protein MrCP20 present within the calcareous base plate of the acorn barnacle Megabalanus rosa (M. rosa) was investigated for its role in regulating biomineralization and growth of the barnacle base plate, as well as the influence of the mineral on the protein structure and corresponding functional role. Calcium carbonate (CaCO3) growth on gold surfaces modified by 11-mercaptoundecanoic acid (MUA/Au) with or without the protein was followed using quartz crystal microbalance with dissipation monitoring (QCM-D), and the grown crystal polymorph was identified by Raman spectroscopy. It is found that MrCP20 either in solution or on the surface affects the kinetics of nucleation and growth of crystals and stabilizes the metastable vaterite polymorph of CaCO3. A comparative study of mass uptake calculated by applying the Sauerbrey equation to the QCM-D data and quantitative X-ray photoelectron spectroscopy determined that the final surface density of the crystals as well as the crystallization kinetics are influenced by MrCP20. In addition, polarization modulation infrared reflection-absorption spectroscopy of MrCP20 established that, during crystal growth, the content of β-sheet structures in MrCP20 increases, in line with the formation of amyloid-like fibrils. The results provide insights into the molecular mechanisms by which MrCP20 regulates the biomineralization of the barnacle base plate, while favoring fibril formation, which is advantageous for other functional roles such as adhesion and cohesion.

Anti-fouling potential and in-silico analysis of carotenoid and fatty acids from Rauvolfia tetraphylla L

Study investigated the antifouling potential ofRauvolfia tetraphyllaL. fruit, leaf and stem extracts against the marine fouling organisms throughin-vitroand in-silicoapproach. Methanolic crude extract of R. tetraphylla L.leaf exhibited maximum antibacterial potential against six fouling organisms isolated from Parangipettai coast and was further taken up for column fractionation. Twenty-four fractions were obtained, among which five fractions showed inhibitory efficiency against microfoulers of Bacillus megaterium. The active compounds present in the bioactive fraction were identified by FTIR, GC-MS and NMR (13C; 1H). The bioactive compounds that exhibited maximum antifouling activity were identified as Lycopersene (80%), Hexadecanoic acid; 1, 2-Benzenedicarboxylic acid, dioctyl ester; Heptadecene - (8) - carbonic acid - (1) and Oleic acid. Molecular docking studies of the potent anti-fouling compounds Lycopersene, Hexadecanoic acid, 1, 2-Benzenedicarboxylic acid, dioctyl ester and Oleic acid showed the binding energy of 6.6, - 3.8, -5.3 and -5.9 (Kcal/mol) and hence these compounds will act as a potential biocide to control the aquatic foulers. Moreover, further studies need to carry out in terms of toxicity, field assessment and clinical trial in order to take these biocides for a patent.

α-Helix-Mediated Protein Adhesion

Proteins have been adopted by natural living organisms to create robust bioadhesive materials, such as biofilms and amyloid plaques formed in microbes and barnacles. In these cases, β-sheet stacking is recognized as a key feature that is closely related to the interfacial adhesion of proteins. Herein, we challenge this well-known recognition by proposing an α-helix-mediated interfacial adhesion model for proteins. By using bovine serum albumin (BSA) as a model protein, it was discovered that the reduction of disulfide bonds in BSA results in random coils from unfolded BSA dragging α-helices to gather at the solid/liquid interface (SLI). The hydrophobic residues in the α-helix then expose and break through the hydration layer of the SLI, followed by the random deposition of hydrophilic and hydrophobic residues to achieve interfacial adhesion. As a result, the first assembled layer is enriched in the α-helix secondary structure, which is then strengthened by intermolecular disulfide bonds and further initiates stepwise layering protein assembly. In this process, β-sheet stacking is transformed from the α-helix in a gradually evolving manner. This finding thus indicates a valuable clue that β-sheet-featuring amyloid may form after the interfacial adhesion of proteins. Furthermore, the finding of the α-helix-mediated interfacial adhesion model of proteins affords a unique strategy to prepare protein nanofilms with a well-defined layer number, presenting robust and modulable adhesion on various substrates and exhibiting good resistance to acid, alkali, organic solvent, ultrasonic, and adhesive tape peeling.

Recent advances in biomimetic hemostatic materials

Although the past decade has witnessed unprecedented medical advances, achieving rapid and effective hemostasis remains challenging. Uncontrolled bleeding and wound infections continue to plague healthcare providers, increasing the risk of death. Various types of hemostatic materials are nowadays used during clinical practice but have many limitations, including poor biocompatibility, toxicity and biodegradability. Recently, there has been a burgeoning interest in organisms that stick to objects or produce sticky substances. Indeed, applying biological adhesion properties to hemostatic materials remains an interesting approach. This paper reviews the biological behavior, bionics, and mechanisms related to hemostasis. Furthermore, this paper covers the benefits, challenges and prospects of biomimetic hemostatic materials.

Protein-Based Biological Materials: Molecular Design and Artificial Production

Polymeric materials produced from fossil fuels have been intimately linked to the development of industrial activities in the 20th century and, consequently, to the transformation of our way of living. While this has brought many benefits, the fabrication and disposal of these materials is bringing enormous sustainable challenges. Thus, materials that are produced in a more sustainable fashion and whose degradation products are harmless to the environment are urgently needed. Natural biopolymers─which can compete with and sometimes surpass the performance of synthetic polymers─provide a great source of inspiration. They are made of natural chemicals, under benign environmental conditions, and their degradation products are harmless. Before these materials can be synthetically replicated, it is essential to elucidate their chemical design and biofabrication. For protein-based materials, this means obtaining the complete sequences of the proteinaceous building blocks, a task that historically took decades of research. Thus, we start this review with a historical perspective on early efforts to obtain the primary sequences of load-bearing proteins, followed by the latest developments in sequencing and proteomic technologies that have greatly accelerated sequencing of extracellular proteins. Next, four main classes of protein materials are presented, namely fibrous materials, bioelastomers exhibiting high reversible deformability, hard bulk materials, and biological adhesives. In each class, we focus on the design at the primary and secondary structure levels and discuss their interplays with the mechanical response. We finally discuss earlier and the latest research to artificially produce protein-based materials using biotechnology and synthetic biology, including current developments by start-up companies to scale-up the production of proteinaceous materials in an economically viable manner.

An essential role of disulfide bonds for the hierarchical self-assembly and underwater affinity of CP20-derived peptides

Barnacles are typical fouling organisms strongly adhere to immersed solid substrates by secreting proteinaceous adhesives called cement proteins (CPs). The self-assembly of the CPs forms a permanently bonded layer that binds barnacles to foreign surfaces. However, it is difficult to determine their natural structure and describe their self-assembly properties due to the abundance of cysteines in whole-length CP20. A putative functional motif of Balanus albicostatus CP20 (BalCP20) was identified to present distinctive self-assembly and wet-binding characteristics. Atomic-force microscopy (AFM) and transmission electron microscope (TEM) investigations showed that wildtype BalCP20-P3 formed grain-like spindles, which assembled into fractal-like structures like ears of wheat. SDS-PAGE, AFM, and LSCM showed that DTT treatment opened up disulfide bonds between cysteines and disrupted fractal-like structures. Additionally, these morphologies were abolished when one of the BalCP20-P3 four cysteines was mutated by alanine. Circular dichroism (CD) results suggested that the morphological diversity among BalCP20-P3 and its mutations was related to the proportion of α-helices. Finally, quartz crystal microbalance with dissipation (QCM-D) detected that BalCP20-P3 and its mutations with diverse self-assemblies occupied different affinities. The above results demonstrated that cysteines and disulfide bonds played a crucial role in the self-assembly and wet binding of BalCP20-P3. The work provides new ideas for the underwater bonding of BalCP20 and developing new bionic underwater adhesives.

Short Peptides Derived from a Block Copolymer-like Barnacle Cement Protein Self-Assembled into Diverse Supramolecular Structures

Peptides capable of self-assembling into different supramolecular structures have potential applications in a variety of areas. The biomimetic molecular design offers an important avenue to discover novel self-assembling peptides. Despite this, a lot of biomimetic self-assembling peptides have been reported so far; to continually expand the scope of peptide self-assembly, it is necessary to find out more novel self-assembling peptides. Barnacle cp19k, a key underwater adhesive protein, shows special block copolymer-like characteristics and diversified self-assembly properties, providing an ideal template for biomimetic peptide design. In this study, inspired by Balanus albicostatus cp19k (Balcp19k), we rationally designed nine biomimetic peptides (P1-P9) and systematically studied their self-assembly behaviors for the first time. Combining microscale morphology observations and secondary structure analyses, we found that multiple biomimetic peptides derived from the central region and the C-terminus of Balcp19k form distinct supramolecular structures via different self-assembly mechanisms under acidic conditions. Specifically, P9 self-assembles into typical amyloid fibers. P7, which resembles ionic self-complementary peptides by containing nonstrictly alternating hydrophobic and charged amino acids, self-assembles into uniform, discrete nanofibers. P6 with amphipathic features forms twisted nanoribbons. Most interestingly, P4 self-assembles to form helical nanofibers and novel ring-shaped microstructures, showing unique self-assembly behaviors. Apart from their self-assembly properties, these peptides showed good cytocompatibility and demonstrated promising applications in biomedical areas. Our results expanded the repertoire of self-assembling peptides and provided new insights into the structure-function relationship of barnacle cp19k.

Adhesive Materials Inspired by Barnacle Underwater Adhesion: Biological Principles and Biomimetic Designs

Wet adhesion technology has potential applications in various fields, especially in the biomedical field, yet it has not been completely mastered by humans. Many aquatic organisms (e.g., mussels, sandcastle worms, and barnacles) have evolved into wet adhesion specialists with excellent underwater adhesion abilities, and mimicking their adhesion principles to engineer artificial adhesive materials offers an important avenue to address the wet adhesion issue. The crustacean barnacle secretes a proteinaceous adhesive called barnacle cement, with which they firmly attach their bodies to almost any substrate underwater. Owing to the unique chemical composition, structural property, and adhesion mechanism, barnacle cement has attracted widespread research interest as a novel model for designing biomimetic adhesive materials, with significant progress being made. To further boost the development of barnacle cement-inspired adhesive materials (BCIAMs), it is necessary to systematically summarize their design strategies and research advances. However, no relevant reviews have been published yet. In this context, we presented a systematic review for the first time. First, we introduced the underwater adhesion principles of natural barnacle cement, which lay the basis for the design of BCIAMs. Subsequently, we classified the BCIAMs into three major categories according to the different design strategies and summarized their research advances in great detail. Finally, we discussed the research challenge and future trends of this field. We believe that this review can not only improve our understanding of the molecular mechanism of barnacle underwater adhesion but also accelerate the development of barnacle-inspired wet adhesion technology.

Transthyretin: From Structural Stability to Osteoarticular and Cardiovascular Diseases

Transthyretin (TTR) is a tetrameric protein transporting hormones in the plasma and brain, which has many other activities that have not been fully acknowledged. TTR is a positive indicator of nutrition status and is negatively correlated with inflammation. TTR is a neuroprotective and oxidative-stress-suppressing factor. The TTR structure is destabilized by mutations, oxidative modifications, aging, proteolysis, and metal cations, including Ca2+. Destabilized TTR molecules form amyloid deposits, resulting in senile and familial amyloidopathies. This review links structural stability of TTR with the environmental factors, particularly oxidative stress and Ca2+, and the processes involved in the pathogenesis of TTR-related diseases. The roles of TTR in biomineralization, calcification, and osteoarticular and cardiovascular diseases are broadly discussed. The association of TTR-related diseases and vascular and ligament tissue calcification with TTR levels and TTR structure is presented. It is indicated that unaggregated TTR and TTR amyloid are bound by vicious cycles, and that TTR may have an as yet undetermined role(s) at the crossroads of calcification, blood coagulation, and immune response.

Omics-based molecular analyses of adhesion by aquatic invertebrates

Many aquatic invertebrates are associated with surfaces, using adhesives to attach to the substratum for locomotion, prey capture, reproduction, building or defence. Their intriguing and sophisticated biological glues have been the focus of study for decades. In all but a couple of specific taxa, however, the precise mechanisms by which the bioadhesives stick to surfaces underwater and (in many cases) harden have proved to be elusive. Since the bulk components are known to be based on proteins in most organisms, the opportunities provided by advancing 'omics technologies have revolutionised bioadhesion research. Time-consuming isolation and analysis of single molecules has been either replaced or augmented by the generation of massive data sets that describe the organism's translated genes and proteins. While these new approaches have provided resources and opportunities that have enabled physiological insights and taxonomic comparisons that were not previously possible, they do not provide the complete picture and continued multi-disciplinarity is essential. This review covers the various ways in which 'omics have contributed to our understanding of adhesion by aquatic invertebrates, with new data to illustrate key points. The associated challenges are highlighted and priorities are suggested for future research.