Collagen-like peptides and peptide–polymer conjugates in the design of assembled materials

Collagen is the most abundant protein in mammals, and there has been long-standing interest in understanding and controlling collagen assembly in the design of new materials. Collagen-like peptides (CLPs), also known as collagen-mimetic peptides (CMPs) or collagen-related peptides (CRPs), have thus been widely used to elucidate collagen triple helix structure as well as to produce higher-order structures that mimic natural collagen fibers. This mini-review provides an overview of recent progress on these topics, in three broad topical areas. The first focuses on reported developments in deciphering the chemical basis for collagen triple helix stabilization, which we review not with the intent of describing the basic structure and biological function of collagen, but to summarize different pathways for designing collagen-like peptides with high thermostability. Various approaches for producing higher-order structures via CLP self-assembly, via various types of intermolecular interaction, are then discussed. Finally, recent developments in a new area, the production of polymer–CLP bioconjugates, are summarized. Biological applications of collagen contained hydrogels are also included in this section. The topics may serve as a guide for the design of collagen-like peptides and their bioconjugates for targeted application in the biomedical arena.     

A Luminescent Cage‐Like Complex Constructed by Bidentate Pyridine‐Containing Ligand and Silver Nitrate

The cage‐like complex, Ag₄L₄(NO₃)₄ ( 1 ) [L = 1, 4‐bis(pyridine‐2‐ylmethoxy)benzene] was synthesized by the reaction of the flexible bidentate ligand and silver nitrate. It was characterized by elemental analysis, IR spectroscopy, TG, and single‐crystal X‐ray analysis. Complex 1 is reported as the first cage‐like cluster constructed by four nitrate anions bridging two [2+2] macrocycles. A blue luminescent emission and luminescent enhancement effect are observed in complex 1 .     

Conductor‐like screening model for relaxed excited states: Implementation in the semiempirical method MSINDO

Two approaches to treat solvent polarization and reorientation effects for excited states of molecules and surfaces have been implemented in the recently developed MSINDO‐sCIS method (Gadaczek, Krause, Hintze, Bredow, J. Chem. Theory Comput. 2011, 7, 3675). They allow for an efficient calculation of analytical energy gradients and hence open the opportunity to investigate fluorescence effects or photochemical reactions in solution for large molecules that are difficult to treat with high‐level methods. Both approaches are based on the conductor‐like screening model (COSMO) (Klamt and Schüürmann, J. Chem. Soc., Perkin Trans. 1993, 2, 799) in combination with the configuration interaction singles (CIS) method (Foresman, Head‐Gordon, Pople, and Frisch, J. Phys. Chem. 1992, 96, 135). The paper gives a brief outline of the theoretical background. As a first application, solvent shifts of three well‐studied, environment‐sensitive fluorescent dyes (Kucherak, Didier, Mély, and Klymchenko, J. Phys. Chem. Lett. 2010, 1, 616) have been calculated and compared with experimental results and standard time‐dependent density functional theory. A statistical evaluation of MSINDO‐COSMO‐sCIS is provided for a set of 39 molecules suggested recently by Jacquemin et al. (Jacquemin, Planchat, Adamo, and Mennucci, J. Chem. Theory Comput. 2012, 8, 2359). Calculated vertical and adiabatic excitation energies and fluorescence energies are compared to experimental data. © 2014 Wiley Periodicals, Inc.     

ABC Triblock Copolymer Micelles: Spherical Versus Worm‐Like Micelles Depending on the Preparation Method

Well‐defined ABC triblock copolymers based on two hydrophilic blocks, A and C, and a hydrophobic block B are synthesized and their self‐assembly behavior is investigated. Interestingly, at the same solvent, concentration, pH, and temperature, different shape micelles are observed, spherical and worm‐like micelles, depending on the preparation method. Specifically, spherical micelles are observed with bulk rehydration while both spherical and worm‐like micelles are observed with film rehydration.

     

Synthesis,crystal structure,and electronic structure of Li2PbSiS4: a quaternary thiosilicate with a compressed chalcopyrite‐like structure

The new quaternary thiosilicate, Li₂PbSiS₄ (dilithium lead silicon tetrasulfide), was prepared in an evacuated fused‐silica tube via high‐temperature, solid‐state synthesis at 800 °C, followed by slow cooling. The crystal structure was solved and refined using single‐crystal X‐ray diffraction data. By strict definition, the title compound crystallizes in the stannite structure type; however, this type of structure can also be described as a compressed chalcopyrite‐like structure. The Li⁺ cation lies on a crystallographic fourfold rotoinversion axis, while the Pb²⁺ and Si⁴⁺ cations reside at the intersection of the fourfold rotoinversion axis with a twofold axis and a mirror plane. The Li⁺ and Si⁴⁺ cations in this structure are tetrahedrally coordinated, while the larger Pb²⁺ cation adopts a distorted eight‐coordinate dodecahedral coordination. These units join together via corner‐ and edge‐sharing to create a dense, three‐dimensional structure. Powder X‐ray diffraction indicates that the title compound is the major phase of the reaction product. Electronic structure calculations, performed using the full potential linearized augmented plane wave method within density functional theory (DFT), indicate that Li₂PbSiS₄ is a semiconductor with an indirect bandgap of 2.22 eV, which compares well with the measured optical bandgap of 2.51 eV. The noncentrosymmetric crystal structure and relatively wide bandgap designate this compound to be of interest for IR nonlinear optics.     

Aharonov–Bohm effect in non-uniform crater-like quantum dot with double rim

We study electron energies in a double concentric quantum ring with anisotropy in the rims heights in the presence of the external magnetic field applied along the symmetry axis. To this end, we consider a model in which the thickness grows linearly from the axis up to the inner rim with a slope different from one between the inner and the outer rims. The anisotropy in the rims heights originated by the presence in the structure of various valleys we simulate by periodic dependence of the slope on the radial direction. We show that the wave functions of the electron confined in such structure can be found analytically if the slopes in all radial directions are the same, and by using a simple exact diagonalization procedure otherwise. The behavior of the electron energies as functions of the magnetic field, rings radii and rims heights, as well as the number of the valleys and their depths is consistently described with our formalism. The entanglement of the states with different radial and orbital quantum numbers, the period and the amplitude of the Aharonov–Bohm oscillations are very sensible to any variations of the rims heights.     

Photoelectrochemical Detection of H2O2 Based on Flower‐Like CuInS2‐Graphene Hybrid

A novel photoelectrochemcial biosensing system was fabricated based on the composition of horseradish peroxidase (HRP), flower‐like CuInS₂ (CIS) and graphene on indium tin oxide (ITO) electrode for detecting H₂O₂. The graphene layer was used as highly conductive scaffolds for electron transport from the ITO electrode to CIS. Furthermore, the flower‐like CIS enhanced the multi‐reflection of light and provided matrixes for the adsorption of HRP. Utilizing one‐pot solvothermal method, we prepared flower‐like CIS‐graphene hybrid (GCIS). Electrochemical tests displayed advantage of graphene with better electron conductivity, and HRP/GCIS showed higher photoelectrochemical behavior.     

Preparation of dendritic‐like CdS by hydrothermal method and its photocatalytic performance

In this article, dendritic‐like CdS has been prepared by a hydrothermal method using thiourea as the sulfur source, and the effects of experimental conditions on the morphologies of CdS have been investigated. The performances of CdS have been analyzed by X‐ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and the fluorescence and photodegradation properties of CdS have also been investigated. The XRD result indicates that the dendritic‐like CdS are of hexagonal phase and they are highly crystallized. Also, the FESEM results show that the ratio of raw material affects the yield of CdS, the reaction time affects the morphology of CdS. The best morphology of CdS is dendritic structures and the length is about 6 μm. The fluorescence spectrum shows three peaks at 470 nm, 513 nm and 547 nm, which indicates that the dendritic‐like CdS mainly emits green and blue fluorescence. Moreover, the dendritic‐like CdS exhibits good photocatalytic activity and its photodegradation rate to methylene blue can reach 92%. The growth mechanism for the formation of CdS with dendritic structure is also described.     

Optical properties of flower‐like CdS prepared by a hydrothermal method with SDBS as surfactant

In this article, flower‐like CdS structures have been prepared by a hydrothermal method with SDBS as surfactant. The influences of different experimental conditions on the morphologies, UV‐Vis and fluorescence properties of CdS have been investigated. The performances of CdS have been analyzed by X‐ray diffraction (XRD), field emission scanning electron microscopy (FESEM), ultraviolet‐visible (UV–Vis) and room‐temperature photoluminescence (PL). The XRD result indicates that the flower‐like CdS structures are of hexagonal phase. The FESEM results indicate that the main role of SDBS is to make the CdS crystals assemble together to form the flower‐like structures. The UV–Vis results show CdS has a strong absorption in the ultraviolet region and visible‐light region. The PL results show CdS has two emission peaks, respectively at 461 nm and 553 nm. The growth mechanism for the formation of flower‐like CdS structures is also described.     

钴镁铁水滑石的合成、表征及衍生复合氧化物酸碱催化活性研究

以Co(NO3)2.6(H2O)、Mg(NO3)2.6(H2O)和Fe(NO3)3.9(H2O)为原料,以NaOH和Na2CO3为沉淀剂采用低过饱和共沉淀法合成了CoMgFe系列的碳酸根水滑石,通过XRD,IR,TG-DTA,等手段对样品进行测试和表征,X-衍射结果显示,其M2 /M3 投料物质的量比为2-4得到的水滑石为理想构型。经焙烧后,发现其复合氧化物对乙醇催化脱水、脱氢反应有一定的活性。