Regiocontrol of the Bulk Polymerization of Lysine Ethyl Ester by the Selection of Suitable Immobilized Enzyme Catalysts.

The development of a green and facile method for the controlled synthesis of functional polypeptides is desired for sustainable material applications. In this study, the regioselective synthesis of poly(l-lysine) (polyLys) via enzyme-catalyzed aminolysis was achieved by bulk polymerization of l-lysine ethyl ester (Lys-OEt) using immobilized Candida antarctica lipase Novozym 435 (IM-lipase) or trypsin (IM-trypsin). Structural characterization of the obtained polyLys revealed that IM-lipase resulted solely in ε-linked amide bond formation, whereas IM-trypsin predominantly provided α-linked polyLys. Optimization of the conditions for the bulk polymerization using immobilized enzymes resulted in high monomer conversion and a high degree of polymerization, with excellent regioselectivity. Molecular docking simulations revealed different binding conformations of Lys-OEt to the catalytic pockets of lipase and trypsin, which putatively resulted in different amino moieties being used for amide bond formation. The immobilized enzymes were recovered and recycled for bulk polymerization, and the initial activity was maintained in the case of IM-trypsin. The obtained α- and ε-linked polyLys products exhibited different degradability against proteolysis, demonstrating the possibility of versatile applications as sustainable materials. This enzymatic regioregular control enabled the synthesis of well-defined polypeptide-based materials with a diverging structural variety.

Synthesis of All-Peptide-Based Rotaxane from a Proline-Containing Cyclic Peptide.

Rotaxane cross-linkers enhance the toughness of the resulting rotaxane cross-linked polymers through a stress dispersion effect, which is attributed to the mobility of the interlocked structure. To date, the compositional diversity of rotaxane cross-linkers has been limited, and the poor compatibility of these cross-linkers with peptides and proteins has made their use in such materials challenging. The synthesis of a rotaxane composed of peptides may result in a biodegradable cross-linker that is compatible with peptides and proteins, allowing the fortification of polypeptides and proteins and ultimately leading to the development of innovative materials that possess excellent mechanical properties and biodegradability. However, the chemical synthesis of all-peptide-based rotaxanes has remained elusive because of the absence of strong binding motifs in peptides, which prevents an axial peptide from penetrating a cyclic peptide. Here, we synthesized all-peptide-based rotaxanes using an active template method for proline-containing cyclic peptides. The results of molecular dynamics simulations suggested that cyclic peptides with an expansive inner cavity and carbonyl oxygens oriented toward the center are favorable for rotaxane synthesis. This rotaxane synthesis method is expected to accelerate the synthesis of peptides and proteins with mechanically interlocked structures, potentially leading to the development of peptide- and protein-based materials with unprecedented functionalities.

Multicomponent nature underlies the extraordinary mechanical properties of spider dragline silk.

Dragline silk of golden orb-weaver spiders (Nephilinae) is noted for its unsurpassed toughness, combining extraordinary extensibility and tensile strength, suggesting industrial application as a sustainable biopolymer material. To pinpoint the molecular composition of dragline silk and the roles of its constituents in achieving its mechanical properties, we report a multiomics approach, combining high-quality genome sequencing and assembly, silk gland transcriptomics, and dragline silk proteomics of four Nephilinae spiders. We observed the consistent presence of the MaSp3B spidroin unique to this subfamily as well as several nonspidroin SpiCE proteins. Artificial synthesis and the combination of these components in vitro showed that the multicomponent nature of dragline silk, including MaSp3B and SpiCE, along with MaSp1 and MaSp2, is essential to realize the mechanical properties of spider dragline silk.

Cell Wall-Denaturing Molecules for Plant Gene Modification.

Zwitterionic molecules, such as zwitterionic liquids (ZILs) and polypeptides (ZIPs), are attracting attention for application in new methods that can be used to loosen tight cell wall networks in a biocompatible manner. These novel methods can enhance the cell wall permeability of nanocarriers and increase their transfection efficiency into targeted subcellular organelles in plants. Herein, we provide an overview of the recent progress and future perspectives of such molecules that function as boosters for cell wall-penetrating nanocarriers.

Plant Mitochondrial-Targeted Gene Delivery by Peptide/DNA Micelles Quantitatively Surface-Modified with Mitochondrial Targeting and Membrane-Penetrating Peptides.

Plant mitochondria play essential roles in metabolism and respiration. Recently, there has been growing interest in mitochondrial transformation for developing crops with commercially valuable traits, such as resistance to environmental stress and shorter fallow periods. Mitochondrial targeting and cell membrane penetration functions are crucial for improving the gene delivery efficiency of mitochondrial transformation. Here, we developed a peptide-based carrier, referred to as Cytcox/KAibA-Mic, that contains multifunctional peptides for efficient transfection into plant mitochondria. We quantified the mitochondrial targeting and cell membrane-penetrating peptide modification rates to control their functions. The modification rates were easily determined from high-performance liquid chromatography chromatograms. Additionally, the gene carrier size remained constant even when the mitochondrial targeting peptide modification rate was altered. Using this gene carrier, we can quantitatively investigate the relationships between various peptide modifications and transfection efficiency and optimize the gene carrier conditions for mitochondrial transfection.

Composition of Minor Ampullate Silk Makes Its Properties Different from Those of Major Ampullate Silk.

Spider's minor ampullate silk, or MI-silk, exhibits distinct mechanical properties and water resistance compared to its major ampullate counterpart (MA-silk). The principal protein constituent of MI-silk is known as minor ampullate spidroin, or MiSp, and while its sequence has been deciphered and is thought to underlie the differences in properties with MA-silk, the composition of MI-silk and the relationship between its composition and properties remain elusive. In this study, we set out to investigate the mechanical properties, water resistance, and proteome of MA-silk and MI-silk from Araneus ventricosus and Trichonephila clavata. We also synthesized artificial fibers from major ampullate spidroin, MaSp1 and 2, and MiSp to compare their properties. Our proteomic analysis reveals that the MI-silk of both araneids is composed of MiSp, MaSp1, and spidroin constituting elements (SpiCEs). The absence of MaSp2 in the MI-silk proteome and the comparison of the water resistance of artificial fibers suggest that the presence of MaSp2 is the reason for the disparity in water resistance between MI-silk and MA-silk.

Unusual pKa Values Mediate the Self-Assembly of Spider Dragline Silk Proteins.

Spider dragline silk is a remarkably tough biomaterial and composed primarily of spidroins MaSp1 and MaSp2. During fiber self-assembly, the spidroin N-terminal domains (NTDs) undergo rapid dimerization in response to a pH gradient. However, obtaining a detailed understanding of this mechanism has been hampered by a lack of direct evidence regarding the protonation states of key ionic residues. Here, we elucidated the solution structures of MaSp1 and MaSp2 NTDs from Trichonephila clavipes and determined the experimental pKa values of conserved residues involved in dimerization using NMR. Surprisingly, we found that the Asp40 located on an acidic cluster protonates at an unusually high pH (∼6.5-7.1), suggesting the first step in the pH response. Then, protonation of Glu119 and Glu79 follows, with pKas above their intrinsic values, contributing toward stable dimer formation. We propose that exploiting the atypical pKa values is a strategy to achieve tight spatiotemporal control of spider silk self-assembly.

Effect of Oligomers Derived from Biodegradable Polyesters on Eco- and Neurotoxicity.

Biodegradable polymers are eco-friendly materials and have attracted attention for use in a sustainable society because they are not accumulated in the environment. Although the characteristics of biodegradable polymers have been assessed well, the effects of their degradation products have not. Herein, we comprehensively evaluated the chemical toxicities of biodegradable polyester, polycaprolactone (PCL), and synthetic oligocaprolactones (OCLs) with different degrees of polymerization. While the PCL did not show any adverse effects on various organisms, high levels of shorter OCLs and the monomer (1 µg/mL for freshwater microorganisms and 1 mg/mL for marine algae and mammalian cells) damaged the tested organisms, including freshwater microorganisms, marine algae, and mammalian cells, which indicated the toxicities of the degradation products under unnaturally high concentrations. These results highlight the need for a further understanding of the effects of the degradation products resulting from biodegradable polyesters to ensure a genuinely sustainable society.

Restructuring the Interface of Silk-Polycaprolactone Biocomposites Using Rigid-Flexible Agents.

Natural fiber-reinforced biocomposites with excellent mechanical and biological properties have attractive prospects for internal medical devices. However, poor interfacial adhesion between natural silk fiber and the polymer matrix has been a disturbing issue for such applications. Herein, rigid-flexible agents, such as polydopamine (PDA) and epoxy soybean oil (ESO), were introduced to enhance the interfacial adhesion between Antheraea pernyi (Ap) silk and a common medical polymer, polycaprolactone (PCL). We compared two strategies of depositing PDA first (Ap-PDA-ESO) and grafting ESO first (Ap-ESO-PDA). The rigid-flexible interfacial agents introduced multiple molecular interactions at the silk-PCL interface. The "Ap-PDA-ESO" strategy exhibited a greater enhancement in interfacial adhesion, and interfacial toughening mechanisms were proposed. This work sheds light on engineering strong and tough silk fiber-based biocomposites for biomedical applications.

Using the organelle glue technique to engineer the plant cell metabolome.

KEY MESSAGE: By using the organelle glue technique, we artificially manipulated organelle interactions and controlled the plant metabolome at the pathway level. Plant cell metabolic activity changes with fluctuating environmental conditions, in part via adjustments in the arrangement and interaction of organelles. This hints at the potential for designing plants with desirable metabolic activities for food and pharmaceutical industries by artificially controlling the interaction of organelles through genetic modification. We previously developed a method called the organelle glue technique, in which chloroplast-chloroplast adhesion is induced in plant cells using the multimerization properties of split fluorescent proteins. Here, we generated transgenic Arabidopsis (Arabidopsis thaliana) plants in which chloroplasts adhere to each other and performed metabolome analysis to examine the metabolic changes in these lines. In plant cells expressing a construct encoding the red fluorescent protein mCherry targeted to the chloroplast outer envelope by fusion with a signal sequence (cTP-mCherry), chloroplasts adhered to each other and formed chloroplast aggregations. Mitochondria and peroxisomes were embedded in the aggregates, suggesting that normal interactions between chloroplasts and these organelles were also affected. Metabolome analysis of the cTP-mCherry-expressing Arabidopsis shoots revealed significantly higher levels of glycine, serine, and glycerate compared to control plants. Notably, these are photorespiratory metabolites that are normally transported between chloroplasts, mitochondria, and peroxisomes. Together, our data indicate that chloroplast-chloroplast adhesion alters organellar interactions with mitochondria and peroxisomes and disrupts photorespiratory metabolite transport. These results highlight the possibility of controlling plant metabolism at the pathway level by manipulating organelle interactions.

Effects of polycaprolactone degradation products on the water flea, Daphnia magna: Carbodiimide additives have acute and chronic toxicity.

Plastics have benefited our lives in many ways, but their long persistence in the environment causes serious problems. Rapid decomposition and detoxification of plastics after use are significant challenges. As a possible solution, biodegradable plastics have attracted attention, and for environmental risk assessment research on polymer toxicity, use of indicator organisms, like water fleas and fish, has increased globally. However, such research often focuses on standardized substances without considering changes in toxicity due to plastic degradation products. Additionally, tests generally focus on acute toxicity, while long-term effects on organismal reproduction and lifespan are largely unknown. Understanding the impact of degraded polymers on biological activities is crucial for accurate risk assessment. In this study, we investigated the biological toxicity of substances generated during degradation of polycaprolactone (PCL), a common biodegradable plastic, using the indicator organism, Daphnia magna. We examined PCL, oligocaprolactones (OCLs), and monomers resulting from polymer cleavage, as well as carbodiimides, added during polyester synthesis. As a result, PCL, which is insoluble in water, reduced individual survival and total number of offspring at an exposure concentration of 100 mg/L, while no toxicity was observed for water-soluble degradation products, OCLs, and monomers. Furthermore, carbodiimides, which are expected to be released during PCL degradation, showed strong toxicity, significantly reducing individual survival and total number of offspring at 0.1-10 mg/L. These findings suggest that changes in physical properties due to polymer degradation and release of additives can significantly alter their toxicity.

Chemoenzymatic Synthesis of Sialyl Sulfo-Oligosaccharides as Potent Siglec-8 Ligands via Transglycosylation Catalyzed by Keratanase II.

Sialyl type-II sulfo-oligosaccharides are gaining much attention as bioactive ligands for Siglecs. In this study, we have achieved the first synthesis of sialyl type-II sulfo-oligosaccharides chemoenzymatically by utilizing the transglycosylation activity of keratanase II. The oxazoline derivative of α(2→3)-sialylated 6,6'-di-sulfo-LacNAc (3) was newly designed as the glycosyl donor for enzymatic transglycosylation. Keratanase II efficiently catalyzed the transglycosylation of 3 with two kinds of glycosyl acceptors, 6-sulfo-Lewis X and 6,6'-di-sulfo-LacNAc derivatives, providing sialyl sulfo-hexasaccharide (1) and sialyl sulfo-pentasaccharide (2) with 86 and 95% yields, respectively. The products 1 and 2 showed higher affinity to Siglec-8 with KD 70 and 25 µmol·L-1, respectively, compared to the known ligand of the α(2→3)-sialylated 6,6'-di-sulfo-Lewis X with KD 185 µmol·L-1. Thus, this study will advance not only the study of Siglec-8 biology but also the exploration of functions of sialyl sulfo-oligosaccharides having various microstructures.

Complexity of Spider Dragline Silk.

The tiny spider makes dragline silk fibers with unbeatable toughness, all under the most innocuous conditions. Scientists have persistently tried to emulate its natural silk spinning process using recombinant proteins with a view toward creating a new wave of smart materials, yet most efforts have fallen short of attaining the native fiber's excellent mechanical properties. One reason for these shortcomings may be that artificial spider silk systems tend to be overly simplified and may not sufficiently take into account the true complexity of the underlying protein sequences and of the multidimensional aspects of the natural self-assembly process that give rise to the hierarchically structured fibers. Here, we discuss recent findings regarding the material constituents of spider dragline silk, including novel spidroin subtypes, nonspidroin proteins, and possible involvement of post-translational modifications, which together suggest a complexity that transcends the two-component MaSp1/MaSp2 system. We subsequently consider insights into the spidroin domain functions, structures, and overall mechanisms for the rapid transition from disordered soluble protein into a highly organized fiber, including the possibility of viewing spider silk self-assembly through a framework relevant to biomolecular condensates. Finally, we consider the concept of "biomimetics" as it applies to artificial spider silk production with a focus on key practical aspects of design and evaluation that may hopefully inform efforts to more closely reproduce the remarkable structure and function of the native silk fiber using artificial methods.

Relaxation of the Plant Cell Wall Barrier via Zwitterionic Liquid Pretreatment for Micelle-Complex-Mediated DNA Delivery to Specific Plant Organelles.

Targeted delivery of genes to specific plant organelles is a key challenge for fundamental plant science, plant bioengineering, and agronomic applications. Nanoscale carriers have attracted interest as a promising tool for organelle-targeted DNA delivery in plants. However, nanocarrier-mediated DNA delivery in plants is severely hampered by the barrier of the plant cell wall, resulting in insufficient delivery efficiency. Herein, we propose a unique strategy that synergistically combines a cell wall-loosening zwitterionic liquid (ZIL) with a peptide-displaying micelle complex for organelle-specific DNA delivery in plants. We demonstrated that ZIL pretreatment can enhance cell wall permeability without cytotoxicity, allowing micelle complexes to translocate across the cell wall and carry DNA cargo into specific plant organelles, such as nuclei and chloroplasts, with significantly augmented efficiency. Our work offers a novel concept to overcome the plant cell wall barrier for nanocarrier-mediated cargo delivery to specific organelles in living plants.

Carotenoids in the eyespot apparatus are required for triggering phototaxis in Euglena gracilis.

Carotenoids are the most universal and most widespread pigments in nature. They have played pivotal roles in the evolution of photosensing mechanisms in microbes and of vision in animals. Several groups of phytoflagellates developed a photoreceptive organelle called the eyespot apparatus (EA) consisting of two separable components: the eyespot, a cluster of carotenoid-rich globules that acts as a reflector device, and actual photoreceptors for photobehaviors. Unlike other algal eyespots, the eyespot of Euglenophyta lacks reflective properties and is generally considered to act as a shading device for the photoreceptor (paraflagellar body, PFB) for major photomovements. However, the function of the eyespot of Euglenophyta has not yet been fully proven. Here, we report that the blocking carotenoid biosynthesis in Euglena gracilis by suppressing the phytoene synthase gene (crtB) caused a defect in eyespot function resulting in a loss of phototaxis. Raman spectroscopy and transmission electron microscopy suggested that EgcrtB-suppressed cells formed eyespot globules but had a defect in the accumulation of carotenoids in those packets. Motion analysis revealed the loss of phototaxis in EgcrtB-suppressed cells: a defect in the initiation of turning movements immediately after a change in light direction, rather than a defect in the termination of cell turning at the appropriate position due to a loss of the shading effect on the PFB. This study revealed that carotenoids are essential for light perception by the EA for the initiation of phototactic movement by E. gracilis, suggesting one possible photosensory role of carotenoids in the EA for the phototaxis.

Lipid Membrane Interaction of Peptide/DNA Complexes Designed for Gene Delivery.

Among gene delivery systems, peptide-based gene carriers have received significant attention because of their selectivity, biocompatibility, and biodegradability. Since cellular membranes function as a barrier toward exogenous molecules, cell-penetrating peptides (CPPs), which are usually cationic and/or amphiphilic, can serve as efficient carriers to deliver cargo into the cytosol. Here, we examined the interactions of carrier peptides and their DNA complexes with lipid membranes using a quartz crystal microbalance (QCM) and high-speed atomic force microscopy (HS-AFM). The carrier peptides are a 12-residue partial presequence of yeast cytochrome c oxidase subunit IV (Cytcox) and BP100, which are a mitochondria-targeting signal peptide and a CPP, respectively. QCM data showed that BP100 has a higher binding affinity than Cytcox to both plasma membrane- and mitochondrial membrane-mimicking lipid bilayers. The DNA complexes with either Cytcox or BP100 exhibited the same tendency. Furthermore, HS-AFM data demonstrated that the DNA complexes of either peptide can disrupt the lipid membranes, forming larger pores in the case of Cytcox. Our results suggest that the binding affinity of the peptide/DNA complex to the plasma membrane is more critical than its membrane disruption ability in enhancing the cellular uptake of DNA.

Construction and Piezoelectric Properties of a Single-Peptide Nanotube Composed of Cyclic ß-peptides with Helical Peptides on the Side Chains.

To develop nanopiezoelectronics, it is necessary to investigate the relationship between the sizes and piezoelectric properties of the material. Peptide nanotubes (PNTs) composed of cyclic ß-peptides have been studied as leading candidates for nanopiezoelectric materials. The current drawback of PNTs is aggregation to form a PNT bundle structure due to strong dipole-dipole interactions between PNTs. Here, we report the construction and piezoelectric properties of single PNTs without nonspecific aggregation by side-chain modification of helical peptides. A cyclic tri-ß-peptide with a helical peptide was prepared by multiple-step liquid-phase peptide synthesis and assembled into PNTs by the vapor diffusion method. These nanotubes were characterized by polarized light microscopy and Fourier transform infrared (FTIR) spectroscopy. Additionally, atomic force microscopy (AFM) topographic images showed nanotubes with a height of 4 nm, which corresponds to the diameter of a PNT on a gold-coated mica substrate, indicating that a single PNT was prepared successfully. The converted piezoelectric response of a single PNT was determined to be 1.39 ± 0.12 pm/V. This value was consistent with that of a PNT bundle, which reveals that the piezoelectricity of PNTs is induced by deformation of their cyclic skeletons and is independent of the bundled structure. This finding not only demonstrates a new molecular design strategy to construct these smallest piezoelectric biomaterials by controlling the supramolecular hierarchical structures but also provides insights into the correlation between molecular assembly morphology and size-dependent piezoelectric properties.

Peptide-Based Polyion Complex Vesicles That Deliver Enzymes into Intact Plants To Provide Antibiotic Resistance without Genetic Modification.

Direct delivery of enzymes into intact plants using cell-penetrating peptides (CPPs) is an attractive approach for modifying plant functions without genetic modification. However, by conventional methods, it is difficult to maintain the enzyme activity for a long time because of proteolysis of the enzymes under physiological conditions. Here, we developed a novel enzyme delivery system using polyion complex vesicles (PICsomes) to protect the enzyme from proteases. We created PICsome-bearing reactive groups at the surface by mixing an anionic block copolymer, alkyne-TEG-P(Lys-COOH), and a cationic peptide, P(Lys). The PICsome encapsulated neomycin phosphotransferase II (NPTII), a kanamycin resistance enzyme, and protected NPTII from proteases in vitro. A CPP-modified PICsome delivered NPTII into the root hair cells of Arabidopsis thaliana seedlings and provided kanamycin resistance in the seedlings that lasted for 7 days. Thus, the PICsome-mediated enzyme delivery system is a promising method for imparting long-term transient traits to plants without genetic modification.

Dual Peptide-Based Gene Delivery System for the Efficient Transfection of Plant Callus Cells.

Owing to their diverse functions and tunable physicochemical properties, peptides are promising alternatives to the conventional gene delivery tools that are available for plant systems. However, peptide-mediated gene delivery is limited by low transfection efficiency in plants because of the insufficient cytosolic translocation of DNA cargo. Here, we report a dual peptide-based gene delivery system for the efficient transfection of plant callus cells. This system is based on the combination of an artificial peptide composed of cationic cell-penetrating and hydrophobic endosomal escape domains with a gene carrier peptide composed of amphiphilic cell-penetrating and cationic DNA-binding domains. Cellular internalization and transfection studies revealed that this dual peptide-based system enables more efficient transfection of callus cells than does a carrier peptide alone by enhancing the endocytic uptake and subsequent cytosolic translocation of a carrier peptide/DNA complex. The present strategy will expand the utility of peptide-mediated plant gene delivery for a wide range of applications and basic research.