Abstract
Connecting molecular-level phenomena to larger scales and, ultimately, to sophisticated molecular systems that resemble living systems remains a considerable challenge in supramolecular ...chemistry. To this end, molecular self-assembly at higher hierarchical levels has to be understood and controlled. Here, we report unusual self-assembled structures formed from a simple porphyrin derivative. Unexpectedly, this formed a one-dimensional (1D) supramolecular polymer that coiled to give an Archimedean spiral. Our analysis of the supramolecular polymerization by using mass-balance models suggested that the Archimedean spiral is formed at high concentrations of the monomer, whereas other aggregation types might form at low concentrations. Gratifyingly, we discovered that our porphyrin-based monomer formed supramolecular concentric toroids at low concentrations. Moreover, a mechanistic insight into the self-assembly process permitted a controlled synthesis of these concentric toroids. This study both illustrates the richness of self-assembled structures at higher levels of hierarchy and demonstrates a topological effect in noncovalent synthesis.
Far‐from‐equilibrium thermodynamic systems that are established as a consequence of coupled equilibria are the origin of the complex behavior of biological systems. Therefore, research in ...supramolecular chemistry has recently been shifting emphasis from a thermodynamic standpoint to a kinetic one; however, control over the complex kinetic processes is still in its infancy. Herein, we report our attempt to control the time evolution of supramolecular assembly in a process in which the supramolecular assembly transforms from a J‐aggregate to an H‐aggregate over time. The transformation proceeds through a delicate interplay of these two aggregation pathways. We have succeeded in modulating the energy landscape of the respective aggregates by a rational molecular design. On the basis of this understanding of the energy landscape, programming of the time evolution was achieved through adjusting the balance between the coupled equilibria.
Finding the right balance: The energy landscape of a supramolecular polymerization in which the supramolecular assembly transforms from a J‐aggregate to an H‐aggregate over time has been modulated by a rational molecular design. Based on this, kinetic control over pathway complexity was achieved through adjusting the balance between the coupled equilibria.
Although living supramolecular polymerization (LSP) has recently been realized, the scope of the monomer structures applicable to the existing methods is still limited. For instance, a monomer that ...spontaneously nucleates itself cannot be processed in a manner consistent with LSP. Herein, we report a new method for such a "reactive" monomer. We use a 'dummy' monomer which has a similar structure to the reactive monomer but is incapable of one-dimensional supramolecular polymerization. We show that in the presence of the dummy monomer, the reactive monomer is kinetically trapped in the dormant state. In this way, spontaneous nucleation of the reactive monomer is retarded; yet, addition of seeds of a supramolecular polymer can initiate the supramolecular polymerization in a chain growth manner. As a result, we obtain the supramolecular polymer of the reactive monomer with a controlled length, which is otherwise thermodynamically inaccessible. We believe that this concept will expand the scope of LSP for the synthesis of other functional supramolecular polymers, and thus lead to a variety of applications.
New method of living supramolecular polymerization is demonstrated. Spontaneous nucleation of a reactive monomer is suppressed by using a 'dummy' monomer. Addition of seeds can initiate supramolecular polymerization in a chain-growth manner.
Recent developments in kinetically controlled supramolecular polymerization permit control of the size (i.e., length and area) of self‐assembled nanostructures. However, control of molecular ...self‐assembly at a level comparable with organic synthetic chemistry and the achievement of structural complexity at a hierarchy larger than the molecular level remain challenging. This study focuses on controlling the aspect ratio of supramolecular nanosheets. A systematic understanding of the relationship between the monomer structure and the self‐assembly energy landscape has derived a new monomer capable of forming supramolecular nanosheets. With this monomer in hand, the aspect ratio of a supramolecular nanosheet is demonstrated that it can be controlled by modulating intermolecular interactions in two dimensions.
Design on a small scale! Molecular self‐assembly in solution, with rational molecular design and under kinetic control, has achieved supramolecular nanosheets with controlled area and aspect ratio.
Despite recent advances in mechanistic understanding and controlled‐synthesis methodologies regarding synthetic supramolecular assemblies, it has remained challenging to capture the molecular‐level ...phenomena in real time, thus hindering further progress in this research field. In this study, we applied high‐speed atomic‐force microscopy (AFM), which has extraordinary spatiotemporal resolution (1 nm and sub‐100 ms), to capture dynamic events occurring during synthetic molecular self‐assembly. High‐speed AFM permitted the visualization of unique dynamic behavior, such as seeded growth and self‐repair in real time. Furthermore, scanning‐probe AFM permitted the site‐specific manipulation and functionalization of a molecular self‐assembly. This powerful combination of bottom‐up and top‐down approaches at the molecular level should enable targeted syntheses of unprecedented functional nanoarchitectures.
Up to speed: The extraordinary spatiotemporal resolution of high‐speed AFM permitted visualization of the seeded growth and self‐repair of supramolecular polymers in real time, and scanning‐probe AFM permitted the site‐specific manipulation and functionalization of a molecular self‐assembly (see picture). This combination of bottom‐up and top‐down approaches at the molecular level should enable the targeted synthesis of functional nanoarchitectures.
Despite substantial effort devoted in the history of supramolecular chemistry, synthetic supramolecular systems still lag behind biomolecular systems in terms of complexity and functionality. This is ...because biomolecular systems function in a multicomponent molecular network under out-of-equilibrium conditions. Here we report two-component supramolecular assemblies that are metastable and thus show time-dependent evolution. We found that the systems undergo either self-sorting or coassembly in time depending on the combination of components. Interestingly, this outcome, which had been previously achievable only under specific conditions, emerged from the two-component systems as a result of synergistic or reciprocal interplay between the coupled equilibria. We believe that this study sheds light on the similarity between synthetic and biomolecular systems and promotes better understanding of their intricate kinetic behaviors.
Molecular self-assembly under kinetic control has many opportunities leading to novel phenomena and applications. However, a mechanistic insight into the intricate kinetic behavior is still lacking. ...Herein, we demonstrate that even a subtle change in the molecular structure affects the kinetic behavior of metastable supramolecular assembles. Interestingly, the kinetic process influenced the size of the final outcomes (in this study, nanosheet structures) in a manner opposite to that predicted by the thermodynamic model. Our findings illustrate the difference between thermodynamically and kinetically controlled molecular self-assemblies. We believe that this study will expand the potential applications of molecular self-assemblies.
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•Transformation kinetics of metastable supramolecular assembles was investigated.•We found that only a subtle alternation in molecular structure affects the kinetics.•We found that the size of the final outcome was determined kinetically.
Immune checkpoint inhibitor has greatly altered the standard of care for patients with advanced non–small-cell lung cancer (NSCLC). This prospective study reported the benefits of nivolumab in a ...routine clinical practice. Furthermore, neutrophil-to-lymphocyte ratio was identified as a candidate of predictive markers in nivolumab-treated NSCLC patients.
The immune checkpoint inhibitor nivolumab is entering routine oncologic practice. We investigated the safety and efficacy of nivolumab in the real world and alternative predictive factors for survival in patients with advanced non–small-cell lung cancer (NSCLC).
We performed a prospective observational study to evaluate the activity of nivolumab treatment for chemotherapy-refractory NSCLC. Patients were treated with nivolumab once every 2 weeks, and the efficacy was assessed every 8 ± 2 weeks.
Fifty-two patients were enrolled after nivolumab approval in Japan. These patients received a median of 4 (range, 1-43) cycles of nivolumab. Overall objective response was observed in 12 patients (23.1%). Median progression-free survival was 2.1 (95% confidence interval, 1.0-3.2) months, and 1-year overall survival rate was 59.9%. A total of 23 immune-related adverse events occurred in 20 patients, as follows: 7 cases of pneumonitis, 6 of oral mucositis, 5 of hypothyroidism, 2 of colitis, 2 of liver dysfunction, and 1 of arthritis. All patients recovered after appropriate management. A pretreatment neutrophil-to-lymphocyte ratio (NLR) of ≥ 5 was significantly associated with poor prognosis compared to NLR < 5 (hazard ratio, 4.52; 95% confidence interval, 1.84-11.14; P = .013), independently.
Nivolumab showed promising activity with a manageable safety profile in clinical practice, consistent with effects of previous clinical trials. This drug could affect a specific population of patients with advanced NSCLC, and pretreatment NLR was a candidate for surrogate markers for survival benefit of patients with NSCLC treated with nivolumab.
Extrusion of chloroquine (CQ) from digestive vacuoles through the Plasmodium falciparum CQ resistance transporter (PfCRT) is essential to establish CQ resistance of the malaria parasite. However, the ...physiological relevance of PfCRT and how CQ-resistant PfCRT gains the ability to transport CQ remain unknown. We prepared proteoliposomes containing purified CQ-sensitive and CQ-resistant PfCRTs and measured their transport activities. All PfCRTs tested actively took up tetraethylammonium, verapamil, CQ, basic amino acids, polypeptides, and polyamines at the expense of an electrochemical proton gradient. CQ-resistant PfCRT exhibited decreased affinity for CQ, resulting in increased CQ uptake. Furthermore, CQ competitively inhibited amino acid transport. Thus, PfCRT is a H ⁺-coupled polyspecific nutrient and drug exporter.
Significance Malaria caused by Plasmodium falciparum is a severe infectious disease with high mortality and morbidity rates worldwide. Chloroquine (CQ) is a widely used antimalarial agent, but the emergence and spread of CQ-resistant parasites is a growing global health problem. Although its physiological relevance remains unknown, P. falciparum CQ resistance transporter (PfCRT) confers CQ resistance through CQ egress from digestive vacuoles of P. falciparum . To address this issue, recombinant CQ-sensitive or CQ-resistant PfCRT proteins were purified and their transport activities were assessed. Both CQ-sensitive and CQ-resistant PfCRTs transported CQ, various antimalarial agents, and basic amino acids, indicating that PfCRT is a polyspecific drug and nutrient exporter.
Small airways are the primary site of pathologic changes in chronic obstructive pulmonary disease (COPD), the major smoking-induced lung disorder.
On the basis of the concept of proximal-distal ...patterning that determines regional specialization of the airway epithelium during lung development, we hypothesized that a similar program operates in the adult human lung being altered by smoking, leading to decreased regional identity of the small airway epithelium (SAE).
The proximal and distal airway signatures were identified by comparing the transcriptomes of large and small airway epithelium samples obtained by bronchoscopy from healthy nonsmokers. The expression of these signatures was evaluated in the SAE of healthy smokers and smokers with COPD compared with that of healthy nonsmokers. The capacity of airway basal stem cells (BCs) to maintain region-associated phenotypes was evaluated using the air-liquid interface model.
The distal and proximal airway signatures, containing 134 and 233 genes, respectively, were identified. These signatures included known developmental regulators of airway patterning, as well as novel regulators such as epidermal growth factor receptor, which was associated with the proximal airway phenotype. In the SAE of smokers with COPD, there was a dramatic smoking-dependent loss of the regional transcriptome identity with concomitant proximalization. This repatterning phenotype was reproduced by stimulating SAE BCs with epidermal growth factor, which was up-regulated in the SAE of smokers, during differentiation of SAE BCs in vitro.
Smoking-induced global distal-to-proximal reprogramming of the SAE represents a novel pathologic feature of COPD and is mediated by exaggerated epidermal growth factor/epidermal growth factor receptor signaling in SAE BCs.
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