Development of photoresponsive supramolecular machines inspired by biological molecular systems

In the growing research area on molecular machinery, light is one of the attractive and useful stimuli source to operate synthetic molecular machines, since light allows selective operation of photoresponsive moieties without additives. We have proposed a new approach to design of photoresponsive molecular machines by interlocking mechanical motions between photoresponsive and movable units through covalent and non-covalent bonds. This approach is inspired by biological molecular machines consisting of multiple protein subunits, and potentially useful for construction of giant mechanical systems. In this review, we will introduce our concepts of the molecular design with several successful examples as well as their applications for controlling chemical events, and also glance at a semi-biological molecular machine controllable by light, which reveals a potential of biological systems for development of elaborate molecular devices.     

Computational models of chemical systems inspired by Braess’ paradox

Systems chemistry is a new discipline which investigates the interactions within a network of chemical reactions. We have studied several computational models of chemical systems inspired by mathematical paradoxes and have found that even simple systems may behave in a counterintuitive, non-linear manner depending upon various conditions. In the present study, we modeled a set of reactions inspired by one such paradox, Braess’ paradox, an interesting phenomenon whereby the introduction of additional capacity (e.g. pathways) in some simple network systems can lead to an unexpected reduction in the overall flow rate of “traffic” through the system. We devised several chemical systems that behaved in this counterintuitive manner; the overall rate of product formation was diminished when an additional pathway was introduced and, conversely, there was an enhancement of product formation when the same interconnecting pathway was removed. We found that, unlike a traffic model, the chemical model needed to include reversible pathways in order to mimic “congestion”—a condition necessary to produce Braess-like behavior. The model was investigated numerically, but a full analytical solution is also included. We propose that this intriguing situation may have interesting implications in chemistry, biochemistry and chemical engineering.     

Shell crosslinked polymer assemblies: Nanoscale constructs inspired from biological systems

The general approach involving the organization of polymers into micellar assemblies followed by stabilization through covalent intramicellar crosslinking of the assemblies has emerged as a powerful method for the production of well‐defined nanostructured materials, having an amphiphilic core‐shell morphology. When the covalent crosslinks are limited to the chain segments that compose the polymer micelle shell, then shell crosslinked knedel‐like (SCK) nanostructures result. The shell composition dictates the interactions of the SCKs with external agents, forms a barrier layer over the core domain, and provides robust character to the nanoparticle. Because of the stability that the crosslinked shell provides, the core domain can be of dramatically different compositions and properties—glassy, fluidlike, and crystalline polymer chains have been employed for the core material and the effects that each contributes to the overall nanostructure properties have been examined. Most notably, the shell crosslinks allow for complete removal of the core to generate hollow (solvent‐filled) nanoscale cagelike structures. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1397–1407, 2000     

A chemical systems approach to evolution

A novel approach to the evolution of organisms is given. It asserts that biological evolution was consequential upon geochemical, environment, change and was inevitable not accidental.     

Synthetic ventures inspired by biosynthetic hypotheses: the evolution of a method for the oxidative amidation of phenols

We describe the development of a technique for the oxidative conversion of 4-alkyl phenols to derivatives of the corresponding 4-alkyl-4-amino-2,5-cyclohexanediones. This transformation, which was inspired by biogenetic considerations, constitutes a key step in the total syntheses of FR-901483, TAN-1251C, and cylindricine C.     

Sulfated liposaccharides inspired by telomerase inhibitor axinelloside A

Sulfated liposaccharides are known inhibitors of telomerase and here we describe the synthesis of a series of sulfated liposaccharides inspired by the natural product axinelloside A, reported to act as an inhibitor of human telomerase. We established a robust and scalable synthetic route to galactosyl liposaccharides capitalizing on a series of regioselective acylation reactions with 2-decenoic acid and imidazolium sulfate esters.     

Enantioselective reactions catalyzed by synthetic enzymes. A model for chemical evolution

Polyleucines of various lengths act as enantioselective catalysts in the aldol condensation between cyclohexanone and various aromatic aldehydes. Polyleucine and other polyamino acids behave as synthetic enzymes in the epoxidation of chalcone and other electron-deficient alkenes. Both reactions are of considerable prebiotic significance.     

Ordering chemical unicyclic graphs by Wiener polarity index

Suppose G is a chemical graph with vertex set V(G). Define D(G) = {{u, v} ⊆ V (G) | d _G (u, v) = 3}, where d _G (u, v) denotes the length of the shortest path between u and v. The Wiener polarity index of G, W _p (G), is defined as the size of D(G). In this article, an ordering of chemical unicyclic graphs of order n with respect to the Wiener polarity index is given.     

Functionalised nanopores: chemical and biological modifications

Nanopore technology has established itself as a powerful tool for single-molecule studies. By analysing changes in the ion current flowing through a single transmembrane channel, a wealth of molecular information can be elucidated. Early studies utilised nanopore technology for sensing applications, and subsequent developments have diversified its remit. Nanopores can be synthetic, solid-state, or biological in origin, but recent work has seen these boundaries blurred as hybrid functionalised pores emerge. The modification of existing pores and the construction of novel synthetic pores has been an enticing goal for creating systems with tailored properties and functionality. Here, we explore chemically functionalised biological pores and the bio-inspired functionalisation of solid-state pores, highlighting how the convergence of these domains provides enhanced functionality.

The convergence of chemistry, biology, and solid-state approaches enables the construction hybrid nanopores with enhanced single-molecule applications.     

Wood plastic composites weathering: Visual appearance and chemical changes

The effects of outside and accelerated (xenon-arc and UVA) weathering on the visual appearance and chemical changes of wood plastic composite (WPC) formulations based on high density polyethylene (HDPE) and polypropylene (PP) were investigated. Colorimetry, scanning electron microscopy, Fourier transform infrared spectroscopy (FT-IR), and pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) were employed in this study. The study showed that for both outside and accelerated weathering, longer exposure time increased the degree of color change (and lightness), carbonyl concentrations, and wood loss on weathered WPC surfaces. HDPE-based WPC exhibited decreased lightening, carbonyl concentrations, and wood content loss when compared to PP-based WPC. From this study, relationships between chemical and color changes that occurred during exterior weathering of HDPE-based WPC were established. Oxidation and degradation of wood lignin influenced WPC color changes (lightening) during weathering.     

The biological targets of acivicin inspired 3-chloro- and 3-bromodihydroisoxazole scaffolds

Target analysis of acivicin derived 3-halodihydroisoxazoles scaffolds in living non-pathogenic and pathogenic bacteria.     

Radiation-induced chemical evolution of biomolecules

Chemical evolution in glycilglycine (Gly2) films irradiated with 146 nm vacuum ultraviolet light was studied. It is found that quantum efficiency of chemical evolution from Gly2 to glycilglycilglycine (Gly3) is smaller than that to glycilglycilglycilglycine (Gly4) due to the multiple step of reaction. Furthermore, we have carried out measurement of soft X-ray natural circular dichroism spectra for serine and alanine films in the energy region of oxygen 1s transition and we report the splitting of 1s→π* transitions.     

A linear algorithm for the Hyper-Wiener index of chemical trees

An algorithm with a complexity linear in the number of vertices is proposed for the computation of the Hyper-Wiener index of chemical trees. This complexity is the best possible. Computational experience for alkanes is reported.     

Total synthesis of exiguamines A and B inspired by catecholamine chemistry

The evolution of a total synthesis of the exiguamines, two structurally unusual natural products that are highly active inhibitors of indolamine-2,3-dioxygenase (IDO), is described. The ultimately successful strategy involves advanced cross-coupling methodology and features a potentially biosynthetic tautomerization/electrocyclization cascade reaction that forms two heterocycles and installs a quaternary ammonium ion in a single synthetic operation.