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Proton exchange membrane (PEM) water electrolysis is attracting attention as a promising method for producing clean hydrogen (H2) without emitting carbon dioxide. H2 is produced by the reduction of protons at the cathode in a PEM electrolyzer. Platinum on carbon (Pt/C) is extensively used as a cathodic electrocatalyst; however, the aggregation of Pt in Pt/C necessitates high loading to maintain catalytic activity. Therefore, the development of efficient H2 production electrocatalysts with low Pt loadings is necessary. Herein, we report the preparation of electrocatalysts consisting of solution-processed platinum nanoparticle (PtNP)/carbon nanomaterial (CNM) composites using surfactant-free aqueous-dispersed PtNPs as a dispersant for CNMs. Direct aqueous suspension by PtNPs through noncovalent functionalization occurs universally with single-walled carbon nanotubes (SWCNTs), graphene, and acetylene black, yielding the respective composites. In particular, the PtNP/SWCNT nanocomposite electrocatalyst with a PtNP loading of 6 μgPt cm–2 exhibited a high mass activity of 89,300 A gPt–1 at 2.0 V, which is 270 times higher than that of Pt/C (324 A gPt–1 at 2.0 V) with a Pt loading of 2.8 mgPt cm–2. Furthermore, a PEM electrolyzer containing this electrocatalyst exhibited a Faradaic efficiency of 99% and operated continuously for 150 h at 100 mA cm–2 at an estimated cost of US$5.3/(kg H2). Our findings are promising in terms of not only establishing a methodology for reducing PtNP loading to the microgram order but also demonstrating the practical feasibility of H2-production electrocatalysts for PEM electrolyzers. [ABSTRACT FROM AUTHOR]

Single-walled carbon nanotubes (SWCNTs) have remarkable electrical properties, making them excellent candidate energy materials for applications, such as transistors and thermoelectric devices. However, as-prepared SWCNTs are mixtures of various chiral indices associated with different diameters, and this heterogeneity hinders their practical applications. Therefore, the development of a method for sorting SWCNTs according to the diameter is required. Here, we report one-pot diameter sorting of SWCNTs through noncovalent functionalization with π-molecular tweezers, which act as a structure-selective oligomeric dispersant for SWCNTs. The tweezers are capable of isolating (9,4) SWCNTs and (7,6) SWCNTs with diameters of ∼0.9 nm from as-prepared SWCNTs to a sorting ratio of 90%. This high-diameter selectivity originates from molecular wrapping of the π-molecular tweezers around the SWCNT sidewalls based on π–π and hydrophobic interactions. Our findings are promising not only in terms of developing a suitable SWCNT sorting methodology but also for understanding their molecular-level sorting mechanism. [ABSTRACT FROM AUTHOR]

The preparation of the Beta-fluorinated derivative of the 1,3-dipyrrolyl-1,3-propanedione B[F.sub.2] complex from 3,4-difluoropyrrole and malonyl chloride, followed by treatment with B[F.sub.3].O[Et.sub.2] is presented. Results show that, despite the simple, acyclic, and neutral structure, the Beta-fluorinated derivative exhibits efficient 1:1 binding for anions in C[H.sub.2][Cl.sub.2] using the bridging CH and pyrrole NH as interaction sites.

A new binding assay that uses oligodeoxyribonucleotides (DNAs) obtained by the in vitro selection method, instead of antibodies, to bind to the target molecule, thyroxine ([T.sub.4]), is described. The DNAs which selectively bound to the [T.sub.4] were selected, labeled with biotin or radioisotope, and then used to detection of [T.sub.4] in the presence of liothyronine ([T.sub.3]), which has a chemical structure similar to that of [T.sub.4].

We describe a new means of surface staining using a fluorescent oligonucleotide. A folic acid-specific, fluorescent-labeled oligonucleotide was selected from a group of randomly sequenced oligonucleotides by repeated elution through a folic acid-immobilized column and amplified by the polymerase chain reaction. We then examined the oligonucleotide scattered on a polyester film with folic acid immobilized in a defined pattern, by means of laser fluorescence microscopy. The results showed that the selected oligonucleotide fluoresced exactly following the pattern of immobilized folic acid.

The design and synthesis of circular RNA dumbbells, containing a stem sequence encoding the firefly luciferase gene and two 9-mer loops are described. The studies have shown that despite their natural RNA strands, dumbbell-shapes RNAs withstand enzymatic degradation and offer prolonged RNAi activity because of the shape of the molecule.

A new nanocomponent is developed that has the function of self-oscillation and a thermoresponsive polymer carrying a Ru complex, a catalyst of the Belousov-Zhabotinsky, is synthesized and immobilized on a glass plate. Periodic turbidity changes in the aqueous solution of the polymer and nanoscale self-oscillation of the immobilized polymer are observed by using atomic force microscopy (AFM).

Atomic force microscopy was used to visualize the extension and contraction events undergone by polymer chains in 'polyelectrolyte brushes' that have been grafted on a porous polymeric membrane. The results revealed that the polyelectrolyte grafts behave like a gate that open and close the pores of the membrane. Such gating mechanism was found to be pH-dependent, that is, at low pH, the membrane pores open while at high pH, the polymer brushes cover the pores.

The β-fluorinated derivative (2b) of the 1,3-dipyrrolyl-1,3-propanedione BF2 complex has been prepared from 3,4-difluoropyrrole and malonyl chloride, followed by treatment with BF3•OEt2. Despite the simple, acyclic, and neutral structure, 2b exhibits efficient 1:1 binding for anions in CH2Cl2 using the bridging CH and pyrrole NH as interaction sites. The binding constant (Ka) of 2b for acetate (CH3CO2-), associating more effectively than anions such as F-, Cl-, Br-, H2PO4-, and HSO4-, is estimated to be 9.6 × 105 M-1, ~9 times larger than that of the β-H derivative 2a (1.1 × 105 M-1). The UV-vis and fluorescence spectral changes of 2b elucidate the effective recognition of an amino acid, such as phenylalanine, in the anionic form; this is also supported by CD spectral changes with mirror images by L- and o-isomers. Furthermore, in the solid state, BF2 complex 2b provides Cl--bridged supramolecular networks and, in sharp contrast, deprotonated "anionic" self-assembled structures by F- binding. [ABSTRACT FROM AUTHOR]

Cancer-specific metabolic alterations hyperactivate the kinase activity of the mammalian/mechanistic target of rapamycin (mTOR) for overcoming stressful environments. Rapalogs, which allosterically inhibit mTOR complex 1 (mTORC1), have been approved as anticancer agents. However, the immunosuppressive side effect of these compounds results in the promotion of tumor metastasis, thereby limiting their therapeutic efficacy. We first report a nonrapalog inhibitor, WRX606 , identified by a hybrid strategy of in silico and in cell selections. Our studies showed that WRX606 formed a ternary complex with FK506-binding protein-12 (FKBP12) and FKBP-rapamycin-binding (FRB) domain of mTOR, resulting in the allosteric inhibition of mTORC1. WRX606 inhibited the phosphorylation of not only the ribosomal protein S6 kinase 1 (S6K1) but also eIF4E-binding protein-1 (4E-BP1). Hence, WRX606 efficiently suppressed tumor growth in mice without promotion of metastasis. These results suggest that WRX606 is a potent lead compound for developing anticancer drugs discovered by in silico and in cell methods.

Inhibiting the programmed death-1 (PD-1)/programmed death ligand 1 (PD-L1) axis by monoclonal antibodies (mAbs) is a successful cancer immunotherapy. However, mAb-based drugs have various disadvantages including high production costs and large molecular sizes, which motivated us to develop a smaller alternative drug. Since PD-L1 binds PD-1 with moderate affinity, a higher affinity PD-1 variant should serve as a competitive inhibitor of the wild-type PD-1/PD-L1 interaction. In this report, we conducted in silico point mutagenesis of PD-1 to identify potent PD-1 variants with a higher affinity toward PD-L1 and refined the in silico results using a luciferase-based in-cell protein-protein interaction (PPI) assay. As a result, a PD-1 variant was developed that had two mutated amino acids (T76Y, A132V), termed 2-PD-1. 2-PD-1 could bind with PD-L1 at a dissociation constant of 12.74 nM. Moreover, 2-PD-1 successfully inhibited the PD-1/PD-L1 interaction with a half maximal inhibitory concentration of 19.15 nM and reactivated the T cell with a half maximal effective concentration of 136.1 nM. These results show that in silico mutagenesis combined with an in-cell PPI assay verification strategy successfully prepared a non-IgG inhibitor of the PD-1/PD-L1 interaction.

Antimicrobial peptides are a potential solution to the threat of multidrug-resistant bacterial pathogens. Recently, deep generative models including generative adversarial networks (GANs) have been shown to be capable of designing new antimicrobial peptides. Intuitively, a GAN controls the probability distribution of generated sequences to cover active peptides as much as possible. This paper presents a peptide-specialized model called PepGAN that takes the balance between covering active peptides and dodging nonactive peptides. As a result, PepGAN has superior statistical fidelity with respect to physicochemical descriptors including charge, hydrophobicity, and weight. Top six peptides were synthesized, and one of them was confirmed to be highly antimicrobial. The minimum inhibitory concentration was 3.1 μg/mL, indicating that the peptide is twice as strong as ampicillin., Competing Interests: The authors declare no competing financial interest., (Copyright © 2020 American Chemical Society.)

Artificial tubular networks are promising structures for biomaterial applications because of their large surface areas. A tubular network was formed by co-assembling two different amphiphilic polypeptides, poly(ethylene glycol)- b -(l-Leu-Aib) 6 (PL12) and polysarcosine- b -(l-Leu-Aib) 6 (SL12). They both have the same hydrophobic 12-mer helical block (l-Leu-Aib) 6 but different hydrophilic chains, poly(ethylene glycol) and polysarcosine. In water, both polypeptides self-assembled into a tubular structure having a uniform 80 nm diameter that was formed by packing among the hydrophobic L12 blocks. The SL12 nanotubes were short (200 nm), straight, and robust. PL12 formed long (>1 μm), bendable, and fusogenic nanotubes. The amphiphiles were then co-assembled with various mixing ratios to form tubular networks. Higher concentrations of PL12 made the nanotubes more bendable and fusogenic between open tube ends, which produced branching junctions under heat treatment.

A thermoresponsive ABA triblock copolymer bearing an aldehyde group on the thermoresponsive A segments was synthesized. The polymer formed a micellar assembly due to the hydrophobic interactions of the thermoresponsive segment above the lower critical solution temperature (LCST). In contrast, the ABA polymer assembly decomposed upon lowering the temperature below the LCST. Using this structural change, the reactivity of the aldehyde group toward primary amines of albumin and poly(allylamine) was investigated. When the ABA polymer assembly and reactant were mixed above the LCST, Schiff base formation was suppressed because of the aldehyde group being protected by the hydrophobic thermoresponsive core. In contrast, Schiff base formation between the ABA triblock copolymer and the primary amine moiety on the molecules was confirmed below the LCST. The reactivity of the aldehyde functional group can therefore be controlled by altering the structure of the thermoresponsive ABA polymer., Competing Interests: The authors declare no competing financial interest., (Copyright © 2019 American Chemical Society.)

Nanomaterial morphology is important for the targeted delivery of drugs to tissues as well as subsequent cellular uptake. Hollow nanotubes composed of peptides, with a diameter of 80 nm and various lengths (100, 200, 300, 600 nm), were successfully capped and sealed with a peptide hemisphere to encapsulate the anticancer drug, cisplatin. The torpedo-shaped nanocapsules with an aspect ratio (length/diameter) of 2.4 showed more rapid cellular uptake and accumulation at the tumor site compared with spherical analogues. Successful delivery of cisplatin to tumors was achieved in a mouse model and tumor growth was efficiently suppressed.

Laser ablation in liquids (LAL) offers a facile technique to develop a large variety of surfactant-free nanomaterials with high purity. However, due to the difficulty in the control of the particle synthesis process, the as-prepared nanomaterials always have a broad size distribution with a large polydispersity (σ). Surfactant-free properties can also cause problems with particle growth, which further increases the difficulty in size control of the colloids. Therefore, searching for strategies to simultaneously unify the sizes of colloids and inhibit particle growth has become significantly important for LAL-synthesized nanomaterials to be extensively used for biological, catalytic, and optical applications, in which fields particle size plays an important role. In this work, we present a facile way to simultaneously realize these two goals by ex situ SU-8 photoresist functionalization. Ag nanoparticles (NPs) synthesized by femtosecond laser ablation of silver in acetone at laser powers of 300 and 600 mW were used as starting materials. The synthesized Ag NPs have a broad size distribution between 1 and 200 nm with an average size of ca. 5.9 nm and σ of 127-207%. After ex situ SU-8 functionalization and 6 months storage, most particles larger than 10 nm become aggregates and precipitate, which makes the size distribution narrow with an average diameter of 4-5 nm and σ of 48-78%. The precipitation process is accompanied by the decrease in colloid mass from the initial ∼0.2 to 0.10-0.11 mg after ex situ SU-8 functionalization and 6 months colloid storage. Morphology analysis indicates that ex situ SU-8 functionalization inhibits the particle growth into polygonal nanocrystals. Radical polymerization of SU-8 on Ag NPs is considered to be the reason for both spontaneous size separation and growth inhibition phenomena. Benefiting from Ag NPs embedment and acetone dissolution, the glass-transition temperature of SU-8 photoresist increased from 314 to 331 °C according to thermogravimetric analysis. The universality of ex situ SU-8 functionalization-induced growth inhibition and size separation behaviors is further proved using the Au colloids generated by LAL in acetone. This work is expected to provide a new route for better size control of LAL-synthesized colloids via ex situ photoresist functionalization, although a half of colloidal mass is wasted due to radical polymerization-induced colloidal precipitation., Competing Interests: The authors declare no competing financial interest.

Single-walled carbon nanotubes (SWCNTs) have received much attention because of their potential in optoelectronic applications. Pristine SWCNTs exhibit substantial van der Waals interactions and hydrophobic characteristics, so precipitation occurs immediately in most organic solvents and water. Highly toxic and hazardous chemicals are often used to obtain well-dispersed SWCNTs. Developing environmentally friendly processing methods for safe and practical applications is a great challenge. Here, we demonstrate direct exfoliation of SWCNTs in pure water only with n-type semiconducting fullerene nanoparticles. The resultant SWCNTs can be well-dispersed in water, where they remain essentially unchanged for several weeks. Adding an aqueous solution of p-type semiconducting water-soluble polythiophene yields self-assembled p/n heterojunctions between polythiophene and the nanoparticles. The aqueous-dispersed SWCNTs yield photocurrent responses in solution-processed thin films as a potential application of water-dispersed carbon nanomaterials., Competing Interests: The authors declare no competing financial interest.

To prepare a fluorogenic peptide ligand which binds to an arbitrary target, we previously succeeded in seeking a fluorogenic ligand to calmodulin using in vitro selection. In this study the environment-sensitive fluorescent group in the selected peptide ligand was replaced with other fluorescent groups to find the possibility to increase the fluorogenic activity. Surface plasmon resonance measurement exhibited that the binding affinity was held even after the replacement. However, the replacement significantly affected the fluorogenic activity. It depended on the kind of incorporated fluorophors and linker length. As a result, the incorporation of 4-N,N-dimethylamino-1,8-naphthalimide enhanced the fluorescence intensity over 100-fold in the presence of target calcium-bound calmodulin. This study demonstrated that the functionality of in vitro selected peptide can be tuned with keeping the binding affinity.