[Show abstract][Hide abstract] ABSTRACT: This paper aims to investigate approximate controllability of stochastic nonlinear partial differential systems with infinite delay. In the systems under study, nonlinearity and control variable exist both in drift and diffusion terms, and controllability problems are considered in the framework with a novel Banach space, which not only leads to some difficulties in deriving the properties of interest but also bring some opportunities to study the system in a more general framework. With the help of a new fundamental lemma established in this paper and some useful inequality techniques, some improved results for approximate controllability of stochastic partial differential systems are obtained by using the Banach contraction theorem without introducing any additional restraints on the terms of the system. An example of stochastic heat equation is also provided to illustrate our results.
Full-text · Article · Dec 2015 · Advances in Difference Equations
[Show abstract][Hide abstract] ABSTRACT: Surface stiffness is considered a key parameter for designing high-performance implantable materials and artificial extracellular matrices, because of its substantial effects on cell behaviours. How to transform biomolecule recognition events, particularly chiral recognition, into stiffness change on material surfaces is biologically essential but much challenging for chemists. Here, we report chirality-triggered stiffness transition on a smart polymer film consisting of flexible polyethylenimine (PEI) main chains grafted with dipeptide units capable of discriminating chiral monosaccharides. The polymer film became substantially softer after interacting with L-ribose, and became more rigid after interacting with D-ribose (the basic building block of DNA and RNA). This chiral effect provides a new method for determining the enantiomeric purity of L/D-ribose mixture, and facilitates the chiral separation of deoxy-ribose racemates, as well as the separations of diverse mono-saccharides, di-saccharides, and oligo-saccharides. These are three puzzle problems in carbohydrate chemistry. Furthermore, taking advantages of the significant differences in the surface stiffness, the proliferation of fibroblast cells on the polymeric surfaces can also be regulated by chiral biomolecules.
No preview · Article · Nov 2015 · ACS Applied Materials & Interfaces
[Show abstract][Hide abstract] ABSTRACT: Life systems have evolved to utilize weak noncovalent interactions, particularly CH-π € interaction, to achieve various biofunctions, for example cellular communication, immune response, and protein folding. However, for artificial materials, it remains a great challenge to recognize such weak interaction, further transform it into tunable macroscopic properties and realize special functions. Here we integrate monosaccharide-based CH-π € receptor capable of recognizing aromatic peptides into a smart polymer with three-component " Recognition-Mediating-Function" design, and report the CH-π € interaction driven surface property switching on smart polymer film, including wettability, adhesion, viscoelasticity and stiffness. Detailed studies indicate that, the CH-π € interaction induces the complexation between saccharide unit and aromatic peptide, which breaks the initial amphiphilic balance of the polymer network, resulting in contraction-swelling conformational transition for polymer chains and subsequent dramatic switching in surface properties. This work not only presents a new approach to control the surface property of materials, but also points to a broader research prospect on CH-π € interaction at a macroscopic level.
Full-text · Article · Oct 2015 · Scientific Reports
[Show abstract][Hide abstract] ABSTRACT: The identification of nonlinear spatiotemporal dynamical systems given by partial differential equations has attracted a lot of attention in the past decades. Several methods, such as searching principle-based algorithms, partially linear kernel methods, and coupled lattice methods, have been developed to address the identification problems. However, most existing methods have some restrictions on sampling processes in that the sampling intervals should usually be very small and uniformly distributed in spatiotemporal domains. These are actually not applicable for some practical applications. In this paper, to tackle this issue, a novel kernel-based learning algorithm named integral least square regularization regression (ILSRR) is proposed, which can be used to effectively achieve accurate derivative estimation for nonlinear functions in the time domain. With this technique, a discretization method named inverse meshless collocation is then developed to realize the dimensional reduction of the system to be identified. Thereafter, with this novel inverse meshless collocation model, the ILSRR, and a multiple-kernel-based learning algorithm, a multistep identification method is systematically proposed to address the identification problem of spatiotemporal systems with pointwise nonuniform observations. Numerical studies for benchmark systems with necessary discussions are presented to illustrate the effectiveness and the advantages of the proposed method.
Full-text · Article · Oct 2015 · IEEE transactions on neural networks and learning systems
[Show abstract][Hide abstract] ABSTRACT: We reported a three-component smart polymer, which could discriminate disaccharide homologues and translate the recognition signals into distinct differences in the macroscopic properties (i.e. wettability and adhesion force) of materials. With these features, we further showed its application in glycopeptide enrichment.
No preview · Article · Sep 2015 · Chemical Communications
[Show abstract][Hide abstract] ABSTRACT: Chiral separation that is closely related to daily life is a meaningful research. Polysaccharide-(e.g., cellulose, amylose derivatives) based chiral packing materials afford powerful chiral stationary phases (CSPs) toward a broad range of racemic compounds. However, considering the explosive growth of specific chiral drugs, the separation efficiencies of these CSPs need further improvement, which calls for new approaches and strategies. Smart polymers can change their physical or chemical properties dynamically and reversibly according to the external stimuli (e.g., thermo-, pH, solvent, ion, light, critical parameters for chromatographic separation) exerted on them, subsequently resulting in tunable changes in the macroscopic properties of materials. In addition to their excellent controllability, the introduction of chiral characteristics into the backbones or side-chains of smart polymers provides a promising route to realize reversibly conformational transition in response to the chiral analytes. This dramatic transition may significantly improve the performance of materials in chiral separation through modulating the enantioselective interactions between materials and analytes. With the help of chirality-responsive polymers, intelligent and switchable CSPs could be developed and applied in column-liquid chromatography. In these systems, the elution order or enantioselectivity of chiral drugs can be precisely modulated, which will help to solve many challenging problems that involve complicated enantiomers. In this paper we introduce some typical examples of smart polymers that serve as the basis for a discussion of emerging developments of CPSs, and then briefly outline the recent CSPs based on natural and certain synthetic polymers.
No preview · Article · Nov 2014 · Science China-Chemistry
[Show abstract][Hide abstract] ABSTRACT: The transformation of recognition signals into regulating macroscopic behaviors of biological entities (e.g., biomolecules and cells) is an extraordinarily challenging task in engineering interfacial properties of artificial materials. Recently, there has been extensive research for dynamic biointerfaces driven by biomimetic techniques. Weak interactions and chirality are two crucial routes that nature uses to achieve its functions, including protein folding, the DNA double helix, phospholipid membranes, photosystems, and shell and tooth growths. Learning from nature inspires us to design dynamic biointerfaces, which usually take advantage of highly selective weak interactions (e.g., synergetic chiral H-bonding interactions) to tailor their molecular assemblies on external stimuli. Biomolecules can induce the conformational transitions of dynamic biointerfaces, then drive a switching of surface characteristics (topographic structure, wettability, etc.), and eventually achieve macroscopic functions. The emerging progresses of dynamic biointerfaces are reviewed and its role from molecular recognitions to biological functions highlighted. Finally, a discussion is presented of the integration of dynamic biointerfaces with the basic biochemical processes, possibly solving the big challenges in life science.
[Show abstract][Hide abstract] ABSTRACT: Protein misfolding to form amyloid aggregates is the main cause of neurodegenerative diseases. While it has been widely acknowledged that amyloid formation in vivo is highly associated with molecular surfaces, particularly biological membranes, how their intrinsic features, e.g. chirality, influence this process still remains unclear. Here we use cysteine enantiomer modified graphene oxide (GO) as a model to show that surface chirality strongly influences this process. We report that R-cysteine modification suppresses the adsorption, nucleation and fiber elongation processes of Aβ(1-40), thus largely inhibits amyloid fibril formation on surface; while S-modification promotes these processes. And surface chirality also greatly influences the conformational transition of Aβ(1-40) from α-helix to β-sheet. More interestingly, we find that this effect is highly related to the distance between chiral moieties and GO surface, and inserting a spacer group of about 1-2 nm between them prevents the adsorption of Aβ(1-40) oligomers, which eliminates the chiral effect. Detailed study stresses the crucial roles of GO surface. It brings novel insights for better understanding the amyloidosis process on surface from a biomimetic perspective.
No preview · Article · Jul 2014 · Journal of the American Chemical Society
[Show abstract][Hide abstract] ABSTRACT: Enantioselective wetting: Regulating the surface wettability of materials through chiral molecules provides new insight into the design of chiral materials. By taking advantage of a reversible conformational transition, smart polymers present an ideal platform for translating weak chiral signals into macroscopic properties of materials, thus resulting in a distinctive wettability switching driven by chirality.
No preview · Article · May 2014 · Angewandte Chemie International Edition
[Show abstract][Hide abstract] ABSTRACT: Chirality is a unique phenomenon in nature. Chiral interactions play an important role in biological and physiological processes, which provides much inspiration for scientists to develop chiral materials. As a breakthrough from traditional materials, biointerface materials based on chiral polymers have attracted increasing interest over the past few years. Such materials elegantly combine the advantages of chiral surfaces and traditional polymers, and provide a novel solution not only for the investigation of chiral interaction mechanisms but also for the design of biomaterials with diverse applications, such as in tissue engineering and biocompatible materials, bioregulation, chiral separation and chiral sensors. Herein, we summarize recent advances in the study of chiral effects and applications of chiral polymer-based biointerface materials, and also present some challenges and perspectives.
No preview · Article · Apr 2014 · Science China-Chemistry
[Show abstract][Hide abstract] ABSTRACT: For the development of rapid glycopeptide enrichment materials, conventional monolayer phenylboronic acid (PBA) based materials inevitably encounter many problems, such as low loading efficiency, long incubation time, and unsatisfactory selectivity. Extending the materials from a 1D monolayer to a 3D polymeric matrix will be one of the best candidates tackling these problems. In this work, a PBA-based polymer material (denoted as polyPBA@SiO2) was developed, in which flexible PBA polymer brushes were immobilized on the surface of silica microspheres, constructing an ideal platform for the efficient enrichment of glycopeptides. This material exhibits stronger interaction with glycopeptides in a higher concentration of organic solvent than in aqueous solution, resulting in the high binding capacity of 60 mg g−1. Moreover, higher selectivity for glycopeptides can be achieved with polyPBA@SiO2 than with both monolayer PBA modified silica and commercial PBA-agarose. These unique features of polyPBA@SiO2 could be attributed to the synergistic effect of polyvalent interactions provided by the polymer brush, specific interaction between PBA and glycopeptides and suppression of the non-specific binding of non-glycopeptides under high ACN concentration.
[Show abstract][Hide abstract] ABSTRACT: For chiral gels and related applications, one of the critical issues is how to modulate the stereoselective interaction between the gel and the chiral guest precisely, as well as how to translate this information into the macroscopic properties of materials. Herein, we report that this process can also be modulated by nonchiral solvents, which can induce a chiral-interaction reversion for organogel formation. This process could be observed through the clear difference in gelation speed and the morphology of the resulting self-assembly. This chiral effect was successfully applied in the selective separation of quinine enantiomers and imparts "smart" merits to the gel materials.
Full-text · Article · Feb 2014 · Angewandte Chemie International Edition
[Show abstract][Hide abstract] ABSTRACT: Enantioselektive Benetzbarkeit: Die Benetzbarkeit einer Materialoberfläche kann gezielt mithilfe chiraler Moleküle verändert werden. Intelligente Polymere bieten die Möglichkeit von reversiblen Konformationsübergängen und eignen sich somit ideal, um ein schwaches chirales Signal in eine makroskopische Eigenschaft eines Materials umzusetzen. Man erhält schaltbare Oberflächen, deren Benetzbarkeit durch die Chiralität von Molekülen bestimmt wird (siehe Schema).
No preview · Article · Jan 2014 · Angewandte Chemie
[Show abstract][Hide abstract] ABSTRACT: Stimuli-responsive polymers could respond to external stimuli, such as temperature, pH, photo-irradiation, electric field, biomolecules in solution, etc., which further induce reversible transformations in the structures and conformations of polymers, providing an excellent platform for controllable drug release, while the accuracy of drug delivery could obtain obvious improvement in this system. In this review, recent progresses in the drug release systems based on stimuli-responsive polymers are summarized, in which drugs can be released in an intelligent mode with high accuracy and efficiency, while potential damages to normal cells and tissues can also be effectively prevented owing to the unique characteristics of materials. Moreover, we introduce some smart nanoparticles-polymers conjugates and drug release devices, which are especially suitable for the long-term sustained drug release.
No preview · Article · May 2013 · Mini Reviews in Medicinal Chemistry
[Show abstract][Hide abstract] ABSTRACT: A dispersion-dominated colorimetric approach for the recognition of carbohydrates based on biomolecule-responsive AuNPs is presented. Taking advantage of the unique dual-responsiveness of smart copolymers, the aggregation and dispersion of AuNPs can be modulated by both temperature and different kinds of carbohydrates, giving rise to a novel chromogenic mechanism for the recognition and testing of carbohydrates in aqueous media.
No preview · Article · Feb 2013 · Advanced Materials
[Show abstract][Hide abstract] ABSTRACT: Die Antwort gibt es hier: Am Naphthalinderivat NTCDA wird ein neuartiges Modell für die Lithiumioneninsertion vorgestellt, bei dem jedes Ringkohlenstoffatom reversibel ein Lithiumion aufnehmen kann, was Entladekapazitäten bis fast 2000 mA h g−1 ergibt. Diese Methode bietet eine neue Strategie für den Aufbau von organischen Hochleistungselektroden.
No preview · Article · May 2012 · Angewandte Chemie
[Show abstract][Hide abstract] ABSTRACT: Getting a charge out of lithium: The naphthalene derivative NTCDA is used to demonstrate a novel lithium ion insertion model in which each ring carbon atom can reversibly accept a lithium ion, giving discharge capacities of up to nearly 2000 mA h g(-1) . This method provides a new strategy for the design of high-performance organic electrodes.
No preview · Article · May 2012 · Angewandte Chemie International Edition
[Show abstract][Hide abstract] ABSTRACT: Carbon-based materials, such as graphite, are the most common anodes used in lithium ion batteries, but the fundamental question of how many Li ions can be inserted onto C(6) aromatic rings remains unsolved. In their Communication (DOI: 10.1002/anie.201109187), T. Sun and co-workers use a model compound to demonstrate that each C(6) ring can accept up to 6 Li ions to create Li(6) /C(6) additive complexes through a reversible electrochemical reaction, which results in Li ion insertion capacities of up to nearly 2000 mA h g(-1) .
Full-text · Article · May 2012 · Angewandte Chemie International Edition
[Show abstract][Hide abstract] ABSTRACT: Kohlenstoffmaterialien wie Graphit sind die gängigsten Anoden in Lithiumionenbatterien, doch die grundlegende Frage, wie viele Li‐Ionen an aromatischen C6‐Ringen gebunden sein können, blieb bisher unbeantwortet. In der Zuschrift auf S. 5237 ff. zeigen T. Sun et al. anhand einer Modellverbindung, dass jeder C6‐Ring in einer reversiblen elektrochemischen Reaktion bis zu 6 Li‐Ionen in Li6/C6‐Additionskomplexen binden kann. Daraus ergibt sich eine Lithiumionen‐Insertionskapazität von fast 2000 mA h g−1.
No preview · Article · May 2012 · Angewandte Chemie