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Kinetic studies on the photochemical quenching reaction of the tris(2,2'-bipyridyl) ruthenium(II) complex ([Ru(bpy) 3 ] 2+ ) in water-glycerol binary media were conducted based on the Einstein-Smoluchowski (E-S) theory. Dynamic and static quenching behaviors were analyzed by comparing results from time-resolved spectroscopy and emission spectroscopy. While the dynamic quenching reaction aligns well with the E-S theory, static quenching was observed, leading to a notable increase in the overall photoquenching reaction rate constant. Employing chromatography and infrared spectroscopy, we correlated the microscopic molecular structure of the binary solvent system and the solvation environment around the emitters with the reaction mechanism. This correlation was found to correspond to ion pair formation and the confinement effect of the emitter, respectively.

Lignocellulosic agricultural waste is an abundant renewable feedstock that can be utilized as a sustainable source of biomass-based plastics. Ideally, it is used without discarding any components, including cellulose, hemicellulose, and lignin. However, their utilization as lignocellulose-based plastics has been limited because of the low compatibility between the polysaccharides and lignin derivatives and the resulting poor mechanical properties of the final products. Here, we demonstrate a facile but highly controllable conversion of sugarcane bagasse into valuable thermoplastics by utilizing the excellent solubility and unique organocatalytic abilities of an ionic liquid, 1-ethyl-3-methylimidazolium acetate. In a homogeneous and one-pot chemical modification reaction system, the substitution ratio of an aromatic benzoyl group to an aliphatic hexanoyl group in the bagasse derivative was adjusted by the ratio of acyl reagents used. Moreover, the allocation of these two acyl groups to polysaccharide and lignin components in bagasse was successfully controlled only by exchanging the order of the acyl reagents introduced into the reaction system. The controlled introduction of the acyl groups into bagasse achieved a homogeneous polymer phase in the resultant multicomponent hot-pressed film, resulting in enhanced mechanical properties such as sufficient tensile strength (∼20 MPa) and excellent ductility with a high strain energy density (∼5 MJ m -3 )., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

The radical S -adenosyl-l-methionine (SAM) methylase Orf29 catalyzes the C -methylation of SAM in the biosynthesis of 1-amino-2-methylcyclopropanecarboxylic acid. Here, we determined that the methylation product is (4″ R )-4″-methyl-SAM. Furthermore, we found that the 5'-deoxyadenosyl radical generated by Orf29 abstracts the pro-R hydrogen atom from the C-4″ position of SAM to generate the radical intermediate, which reacts with methylcobalamin to give (4″ R )-4″-methyl-SAM. Consequently, the Orf29-catalyzed C -methylation was confirmed to proceed with retention of configuration.

While the genome mining approach has enabled the rational exploration of untapped bioactive natural products, in silico identifications of their biosynthetic genes are often unconnected to the actual production of the corresponding molecules in native strains due to the genetic dormancy. We report here the rational discovery of an unexplored cationic homo polyamino acid (CHPA) antibiotic by potential producer prioritization-guided genome mining. Mining the genome of γ-poly-d-diaminobutyric acid (poly-d-Dab)-producing Streptoalloteichus hindustanus NBRC 15115, which was selected based on the finding that the known CHPAs are universally co-produced in pairs, identified a putative CHPA synthetase, PblA, as a potential candidate being expressed actively. Bioinformatic and biochemical analyses of PblA provided the critical clue that its polymer product could be an unusual CHPA consisting of l-β-lysine. Instrumental analyses of the metabolites from S. hindastanus indeed revealed the production of an unprecedented linear CHPA, ε-poly-l-β-lysine, concomitantly with poly-d-Dab. The CHPA we discovered exerted excellent antimicrobial activity against a broad spectrum of microorganisms, including bacteria and fungi, and was revealed to show resistance against nonspecific proteolytic enzymes. This study marks the first report of the efficacy of the strain prioritization-guided genome mining strategy for the discovery of bioactive CHPAs.

Among the four bioactive cationic homo-poly(amino acids) discovered in nature, two are mirror-image isomers of poly(2,4-diaminobutyric acid) (poly-Dab) whose biosynthesis has long been unexplained. Their structural analogy plausibly suggested that they could share a common biosynthetic pathway utilizing ε-poly(l-lysine) synthetase-like enzymology but with an unprecedented process for enantiomeric inversion of polymer building blocks. To investigate this possibility, we comparatively explored the biosynthesis of poly-l-Dab and its mirror-image isomer poly-d-Dab in Streptomyces celluloflavus USE31 and Streptoalloteichus hindustanus NBRC15115, respectively, through genome mining, genetic inactivation, and heterologous expression combined with biochemical assays. While they shared the same biosynthetic pathway, the poly-d-Dab biosynthetic gene cluster additionally harbored the racemase gene. The critical finding that poly-d-Dab synthetase, in contrast to the synthetase generating the l-isomer, selectively activated d-Dab through adenylation conclusively demonstrated that free diffusible d-Dab preactivationally generated by the racemase is directly activated to be incorporated into the polymer. Our study thus represents the first demonstration of the stereoselective biosynthesis of a nonribosomal peptide governed by adenylation activity for a d-amino acid other than alanine. In silico sequence comparison between poly-Dab synthetases allowed us to identify amino acid residues potentially responsible for the discrimination of Dab enantiomers. Our results will provide significant insight not only for the future discovery of novel bioactive cationic poly(amino acids) but also for the creation of designer nonribosomal peptides with d-configuration.

Marine microorganisms de novo biosynthesize polyunsaturated fatty acids such as docosahexaenoic acid and eicosapentaenoic acid by polyunsaturated fatty acid (PUFA) synthases composed of three or four polypeptides in a manner similar to fatty acid synthases (FASs). FASs usually possess thioesterase (TE) domains to release free fatty acids from acyl carrier protein (ACP)-tethered intermediates. Here, we investigated the off-loading mechanism with microalgal and bacterial PUFA synthases through in vivo and in vitro experiments. The in vitro experiments with acyltransferase (AT)-like domains and acyl-ACP substrates clearly demonstrated that the AT-like domains catalyzed the hydrolysis of acyl-ACPs to yield free fatty acids.

A moldable material from a natural cationic polyelectrolyte, ε-poly-l-lysine (ε-PL), was prepared by mixing with two lignosulfonates a reagent for research (L-SO 3 Na) and a commercially available purified lignosulfonate (Pearllex NP). The obtained ε-PL/lignosulfonate complexes demonstrated the ability to be tuned from a rigid form, such as polystyrene or poly(methyl methacrylate), to a soft elastomer form such as silicone by varying the lignosulfonate species and composition. The maximum toughness of the complex (8.4 MJ/m 3 ) was superior to that of ε-PL or lignosulfonate-derived polyelectrolyte complexes. In addition, the ε-PL/lignosulfonate complex showed self-healing properties due to the many reversible ionic bonds in the complex. The preparation process for the novel complex was simple, involving the mixing and drying of an aqueous solution of the polyelectrolyte without any extra reagents (organic solvents, condensation reagents, and cross-linker). Thus, given these many advantages and the excellent biodegradability of the components, the ε-PL/lignosulfonate complex is expected to be useful as a sustainable structural material., Competing Interests: The authors declare no competing financial interest.

Molecular design of stimuli-sensitive polymers has been attracting considerable interest of chemists because of their latent ability to achieve smart materials. Heat, light, pH, and chemicals have been often utilized as a stimuli-inducing polymer phase transition from solution to aggregation and vice versa. In this report, as a new trigger for lower critical solution temperature (LCST)-type polymer phase transition, we introduce organic reaction of small organic molecules, not to the polymer chain itself. The addition of the reactant for the "effector", which can interact with the polymer chain for increasing the compatibility of the polymer chain with the media, caused a polymer phase separation, due to reduction of the solvation ability of the effector to the polymer chain. In other words, decrease of the "effector" concentration induced the polymer phase separation. Within our knowledge, this is the first report to connect a polymer phase separation with organic reaction dynamics. This process will be the first step for the development of artificial allosteric enzyme mimics from a combination of a simple synthetic polymer and a product or reactant in organic reactions.

ε-Poly-l-lysine (ε-PL) is one of the few homopoly(amino-acid)s occurring in nature. ε-PL, which possesses multiple amino groups, is highly soluble in water, where it forms the antimicrobial polycationic chain (PL n+ ). Although the high water-solubility is advantageous for the use of ε-PL as a food preservative, it has limited the applicability of ε-PL as a biopolymer plastic. Here, we report on the preparation and availability of a water-insoluble complex formed with PL n+ and an anionic surfactant, bis(2-ethylhexyl) sulfosuccinate (BEHS - , is also commercialized as AOT) anion. The PL n+ /BEHS - -complex, which is soluble in organic solvents, was successfully used as a coating material for a cellulose acetate membrane to create a water-resistant antimicrobial membrane. In addition, the thermoplastic PL n+ /BEHS - -complex was able to be uniformly mixed with polypropylene by heating, resulting in materials exhibiting antimicrobial activities.

The microtubule (MT) is the stiffest cytoskeletal filamentous protein that takes part in a wide range of cellular activities where its mechanical property plays a crucially significant role. How a single biological entity plays multiple roles in cell has been a mystery for long time. Over the recent years, it has been known that modulation of the mechanical property of MT by different cellular agents is the key to performing manifold in vivo activities by MT. Studying the mechanical property of MT thus has been a prerequisite in understanding how MT plays such diversified in vivo roles. However, the anisotropic structure of MT has been an impediment in obtaining a precise description of the mechanical property of MT along its longitudinal and lateral directions that requires employment of distinct experimental approach and has not been demonstrated yet. In this work, we have developed an experimental system that enabled us to investigate the effect of tensile stress on MT. By using our newly developed system, (1) we have determined the Young's modulus of MT considering its deformation under applied tensile stress and (2) a new role of MT associated motor protein kinesin in modulating the mechanical property of MT was revealed for the first time. Decrease in Young's modulus of MT with the increase in interaction with kinesin suggests that kinesin has a softening effect on MT and thereby can modulate the rigidity of MT. This work will be an aid in understanding the modulation of mechanical property of MTs by MT associated proteins and might also help obtain a clear insight of the endurance and mechanical instability of MTs under applied stress.

[reaction: see text] The biosynthesis of the meroterpenoid neomarinone from a marine actinomycete was probed through feeding experiments with (13)C-labeled precursors. NMR characterization of [U-(13)C(6)]glucose-enriched neomarinone led to the structural revision of structure 4a to 4b, which was confirmed by extensive 2D NMR spectrometry with unlabeled compound.

Recent methodology for the investigation of isoprenoid biosynthesis featuring pathway switching and hyperdeuteration has shown significant advantages in elucidating the reaction mechanism of a novel Streptomyces diterpene cyclase with use of precise atom-level analysis. Insight into the cyclization mechanism involved in the conversion of geranylgeranyl diphosphate (GGPP) into a clerodane hydrocarbon terpentetriene was obtained by heterologous expression in doubly engineered Streptomyces lividans of a diterpene cyclase gene derived from Streptomyces griseolosporeus, a producer of an unique diterpenoid cytotoxic antibiotic terpentecin, and by in vivo labeling with mevalonate-d(9). The cyclization involved electrophilic protonation, cationic ring closure, Wagner-Meerwein-type rearrangements, and deprotonation. A key feature was that the labeled metabolite as a mixture of predominantly deuterated mosaic molecules provided sufficient information that close analysis of the labeling pattern for each individual isoprene unit was achieved primarily by (1)H NMR spectroscopy. The cyclization of GGPP into the clerodane skeleton catalyzed by the cyclase appears to involve Si-face specific protonation, intermediates with A/B chair-boat conformation, and specific methyl and hydride migrations to give an intermediary C-4 carbocation. Subsequent collapse of the cation through specific removal of the initiating proton and final elimination of diphosphate gives rise to the terpentetriene hydrocarbon.