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1.
Artigo em Inglês | MEDLINE | ID: mdl-31916356

RESUMO

The protein Survivin is highly upregulated in most cancers and considered to be a key player in carcinogenesis. We explored a supramolecular approach to address Survivin as a drug target by inhibiting the protein-protein interaction of Survivin and its functionally relevant binding partner Histone H3. Ligand L1 is based on the guanidiniocarbonyl pyrrole cation and serves as a highly specific anion binder in order to target the interaction between Survivin and Histone H3. NMR titration confirmed binding of L1 to Survivin's Histone H3 binding site. The inhibition of the Survivin-Histone H3 interaction and consequently a reduction of cancer cell proliferation were demonstrated by microscopic and cellular assays.

2.
Chem Commun (Camb) ; 56(7): 1105-1108, 2020 Jan 23.
Artigo em Inglês | MEDLINE | ID: mdl-31894766

RESUMO

A series of hydrogen-bonded liquid crystals based on resveratrol and resveratrone is reported and investigated with respect to their photo-switchability (at 405 nm) and photo-cyclisation (at 300 nm).

3.
Chem Asian J ; 14(6): 814-820, 2019 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-30478991

RESUMO

In this contribution, we present the synthesis and self-assembly of alkylated thioethers with interesting photophysical properties. To this end, the emission, absorption and excitation spectra in organic solvents and as aggregates in water were measured as well as the corresponding photoluminescence quantum yields and lifetimes. The aggregates in aqueous media were visualized and measured using transmission electron microscopy. Besides that, crystal structures of selected compounds allowed a detailed discussion of the structure-property relationship. Furthermore, the mesomorphic behavior was investigated using polarized optical microscopy (POM) as well as differential scanning calorimetry (DSC).

4.
Nanomaterials (Basel) ; 8(12)2018 Dec 10.
Artigo em Inglês | MEDLINE | ID: mdl-30544769

RESUMO

The self-assembly of AB diblock copolymers in three-dimensional (3D) soft confinement of nanoemulsions has recently become an attractive bottom up route to prepare colloids with controlled inner morphologies. In that regard, ABC triblock terpolymers show a more complex morphological behavior and could thus give access to extensive libraries of multicompartment microparticles. However, knowledge about their self-assembly in confinement is very limited thus far. Here, we investigated the confinement assembly of polystyrene-block-poly(4-vinylpyridine)-block-poly(tert-butyl methacrylate) (PS-b-P4VP-b-PT or SVT) triblock terpolymers in nanoemulsion droplets. Depending on the block weight fractions, we found spherical microparticles with concentric lamella⁻sphere (ls) morphology, i.e., PS/PT lamella intercalated with P4VP spheres, or unusual conic microparticles with concentric lamella⁻cylinder (lc) morphology. We further described how these morphologies can be modified through supramolecular additives, such as hydrogen bond (HB) and halogen bond (XB) donors. We bound donors to the 4VP units and analyzed changes in the morphology depending on the binding strength and the length of the alkyl tail. The interaction with the weaker donors resulted in an increase in volume of the P4VP domains, which depends upon the molar fraction of the added donor. For donors with a high tendency of intermolecular packing, a visible change in the morphology was observed. This ultimately caused a shape change in the microparticle. Knowledge about how to control inner morphologies of multicompartment microparticles could lead to novel carbon supports for catalysis, nanoparticles with unprecedented topologies, and potentially, reversible shape changes by light actuation.

5.
Soft Matter ; 14(30): 6214-6221, 2018 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-29932197

RESUMO

The impact of the linking group in hydrogen-bonded liquid crystals is systematically studied by a modular approach. POM and DSC results exhibited tremendous differences in the mesomorphic behaviour of the assemblies, due to the versatile linkages of the side chains, which were correlated with structural features and the elctronical nature of the side chains.

6.
Langmuir ; 32(36): 9329-34, 2016 09 13.
Artigo em Inglês | MEDLINE | ID: mdl-27588561

RESUMO

Novel hybrid materials of cellulose and magnetic nanoparticles (NPs) were synthesized and characterized. The materials combine the chiral nematic structural features of mesoporous photonic cellulose (MPC) with the magnetic properties of cobalt ferrite (CoFe2O4). The photonic, magnetic, and dielectric properties of the hybrid materials were investigated during the dynamic swelling and deswelling of the MPC films. It was observed that the dielectric properties of the generated MPC films increased tremendously following swelling in water, endorsing efficient swelling ability of the generated mesoporous films. The high magnetic permeability of the developed MPC films in conjunction with their superior dielectric properties, predominantly in the swollen state, makes them interesting for electromagnetic interference shielding applications.

7.
Chem Commun (Camb) ; 52(55): 8549-52, 2016 Jun 30.
Artigo em Inglês | MEDLINE | ID: mdl-27314613

RESUMO

Herein we report an efficient modular approach to supramolecular functional materials. Hierarchical self-assembly of azopyridine derivatives and hydrogen-bond donors yielded discotic assemblies. Subtle differences in the core units introduced mesomorphic behaviour and fast photo-response of the liquid crystals based on phloroglucinol. The presented results prove the benefits of a modular methodology towards highly responsive materials with tailor-made properties.

8.
Chem Rev ; 115(16): 8867-95, 2015 Aug 26.
Artigo em Inglês | MEDLINE | ID: mdl-26278927
9.
Chem Sci ; 6(1): 354-359, 2015 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-28966761

RESUMO

The present study gives a comprehensive insight into anion-π interactions in the solid state, focusing on purely organic and charge-neutral fluorophenyl groups bearing a positive charge located at a side chain. The detailed statistical analysis of a series of structural data sets shows the geometrical variability of anion-π bonding in the solid state. It reveals the directing substituents at the arene as key elements for the positional preferences of anions above π-systems. The structural variety of the interaction between anions and electron-deficient arenes is considered by use of the hapticity concept. Together with new evaluation criteria, two helpful tools to understand and describe anion-π interactions in the solid are used.

10.
Angew Chem Int Ed Engl ; 54(10): 2888-910, 2015 Mar 02.
Artigo em Inglês | MEDLINE | ID: mdl-25521805

RESUMO

Cellulose nanocrystals (CNCs), known for more than 50 years, have attracted attention because of their unique properties such as high specific strength and modulus, high surface area, and fascinating optical properties. Just recently, however, their potential in supramolecular templating was identified by making use of their self-assembly behavior in aqueous dispersions in the presence of compatible precursors. The combination of the mesoporosity, photonic properties, and chiral nematic order of the materials, which are available as freestanding films, has led to a significant number of interesting and promising discoveries towards new functional materials. This Review summarizes the use of cellulose derivatives, especially CNCs, as novel templates and gives an overview of the recent developments toward new functional materials.

11.
Chem Commun (Camb) ; 51(3): 530-3, 2015 Jan 11.
Artigo em Inglês | MEDLINE | ID: mdl-25412150

RESUMO

Gold nanoparticles (NPs) have been loaded into mesoporous photonic cellulose (MPC) films. The NPs show a low polydispersity and a nanoparticle-based plasmonic chiroptical activity with potential for novel sensing materials.

12.
Magn Reson Chem ; 52(10): 532-9, 2014 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-25251221

RESUMO

Liquid crystals confined to porous materials often have different critical phenomena and ordering than in the bulk. Through the selection of pore size, structure and guest liquid crystal, these systems could enable a variety of functional materials for applications such as sensors and displays. A recent example of such a system is chiral nematic mesoporous films infiltrated with liquid crystal 4-cyano-4'-n-octylbiphenyl (8CB), which has reversible thermal switching of its optical bandgap. The optical bandgap is lost when the ordered 8CB guests are heated above ∼50 °C, where the 8CB becomes isotropic. In this study, we have used NMR cryoporometry and pulsed-field gradient diffusion measurements to determine the pore sizes and structures of various chiral nematic mesoporous silica and organosilica films. Temperature and orientation-dependent wideline (15)N NMR spectra of films infiltrated with (15)N-labelled 8CB guests show that the ordering of the 8CB mesogens is consistent with an average orientation parallel to the chiral nematic pore axes. Inclusion of a large, orientation-dependent shift was necessary to fit the spectra, probably due to susceptibility differences between the 8CB guests and the organosilica host.

13.
Angew Chem Int Ed Engl ; 53(34): 8880-4, 2014 Aug 18.
Artigo em Inglês | MEDLINE | ID: mdl-24981200

RESUMO

Cellulose-based materials have been and continue to be exceptionally important for humankind. Considering the bioavailability and societal relevance of cellulose, turning this renewable resource into an active material is a vital step towards sustainability. Herein we report a new form of cellulose-derived material that combines tunable photonic properties with a unique mesoporous structure resulting from a new supramolecular cotemplating method. A composite of cellulose nanocrystals and a urea-formaldehyde resin organizes into a chiral nematic assembly, which yields a chiral nematic mesoporous continuum of desulfated cellulose nanocrystals after alkaline treatment. The mesoporous photonic cellulose (MPC) films undergo rapid and reversible changes in color upon swelling, and can be used for pressure sensing. These new active mesoporous cellulosic materials have potential applications in biosensing, optics, functional membranes, chiral separation, and tissue engineering.


Assuntos
Celulose/química , Fótons , Formaldeído/química , Microscopia Eletrônica de Varredura , Nanopartículas , Estereoisomerismo , Ureia/química
14.
Acc Chem Res ; 47(4): 1088-96, 2014 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-24694253

RESUMO

Cellulose nanocrystals (CNCs) are obtained from the sulfuric acid-catalyzed hydrolysis of bulk cellulose. The nanocrystals have diameters of ~5-15 nm and lengths of ~100-300 nm (depending on the cellulose source and hydrolysis conditions). This lightweight material has mostly been investigated to reinforce composites and polymers because it has remarkable strength that rivals carbon nanotubes. But CNCs have an additional, less explored property: they organize into a chiral nematic (historically referred to as cholesteric) liquid crystal in water. When dried into a thin solid film, the CNCs retain the helicoidal chiral nematic order and assemble into a layered structure where the CNCs have aligned orientation within each layer, and their orientation rotates through the stack with a characteristic pitch (repeating distance). The cholesteric ordering can act as a 1-D photonic structure, selectively reflecting circularly polarized light that has a wavelength nearly matching the pitch. During CNC self-assembly, it is possible to add sol-gel precursors, such as Si(OMe)4, that undergo hydrolysis and condensation as the solvent evaporates, leading to a chiral nematic silica/CNC composite material. Calcination of the material in air destroys the cellulose template, leaving a high surface area mesoporous silica film that has pore diameters of ~3-10 nm. Importantly, the silica is brilliantly iridescent because the pores in its interior replicate the chiral nematic structure. These films may be useful as optical filters, reflectors, and membranes. In this Account, we describe our recent research into mesoporous films with chiral nematic order. Taking advantage of the chiral nematic order and nanoscale of the CNC templates, new functional materials can be prepared. For example, heating the silica/CNC composites under an inert atmosphere followed by removal of the silica leaves highly ordered, mesoporous carbon films that can be used as supercapacitor electrodes. The composition of the mesoporous films can be varied by using assorted organosilica precursors. After removal of the cellulose by acid-catalyzed hydrolysis, highly porous, iridescent organosilica films are obtained. These materials are flexible and offer the ability to tune the chemical and mechanical properties through variation of the organic spacer. Chiral nematic mesoporous silica and organosilica materials, obtainable as centimeter-scale freestanding films, are interesting hosts for nanomaterials. When noble metal nanoparticles are incorporated into the pores, they show strong circular dichroism signals associated with their surface plasmon resonances that arise from dipolar coupling of the particles within the chiral nematic host. Fluorescent conjugated polymers show induced circular dichroism spectra when encapsulated in the chiral nematic host. The porosity, film structure, and optical properties of these materials could enable their use in sensors. We describe the development of chiral nematic mesoporous silica and organosilica, demonstrate different avenues of host-guest chemistry, and identify future directions that exploit the unique combination of properties present in these materials. The examples covered in this Account demonstrate that there is a rich diversity of composite materials accessible using CNC templating.


Assuntos
Celulose/química , Nanoestruturas/química , Dicroísmo Circular , Géis , Hidrólise , Nanopartículas/química , Óptica e Fotônica/instrumentação , Porosidade , Dióxido de Silício/química , Propriedades de Superfície
15.
Dalton Trans ; 43(4): 1873-80, 2014 Jan 28.
Artigo em Inglês | MEDLINE | ID: mdl-24258002

RESUMO

The stabilization of polyhalides in the solid state with the support of electron-deficient pentafluorophenyl groups is described. Furthermore, a synthetic approach towards the sensitive tetraiodide dianion is described and ESI mass spectrometric evidence for its presence in solution is reported.


Assuntos
Ânions/química , Halogênios/química , Modelos Moleculares , Espectrometria de Massas por Ionização por Electrospray , Espectrofotometria Ultravioleta
16.
Pharmacol Ther ; 142(1): 11-32, 2014 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-24287313

RESUMO

The renin-angiotensin system (RAS) is most well-known for its role in regulation and dysregulation of blood pressure as well as fluid and electrolyte homeostasis. Due to its ability to cause cardiovascular disease, the RAS is the target of a multitude of drugs that antagonize its pathophysiological effects. While the "classical" RAS is a systemic hormonal system, there is an increasing awareness of the existence and functional significance of local RASs in a number of organs, e.g., liver, kidney, heart, lungs, reproductive organs, adipose tissue and adrenal. The eye is one of these organs where a compelling body of evidence has demonstrated the presence of a local RAS. Individual components of the RAS have been shown to be present in many structures of the eye and their potential functional significance in ocular disease states is described. Because the eye is one of the most important and complex organs in the body, this review also discusses the implications of dysregulation of the systemic RAS on the pathogenesis of ocular diseases and how pharmacological manipulation of the RAS might lead to novel or adjunctive therapies for ocular disease states.


Assuntos
Oftalmopatias/metabolismo , Olho/metabolismo , Sistema Renina-Angiotensina/fisiologia , Animais , Oftalmopatias/tratamento farmacológico , Humanos
17.
Langmuir ; 29(40): 12579-84, 2013 Oct 08.
Artigo em Inglês | MEDLINE | ID: mdl-24074378

RESUMO

The conjugated polymer poly(p-phenylenevinylene) (PPV) was polymerized in the pores of chiral nematic mesoporous organosilica to give a composite film showing the strong characteristic fluorescence of PPV as well as the iridescence due to the photonic band gap of the host material. Detailed circular dichroism (CD) studies reveal a chiral structure of the polymer within the pores. These new fluorescent materials undergo fluorescence quenching upon exposure to electron deficient aromatics such as 2,4,6-trinitrotoluene (TNT), indicating that they may be useful for developing chemical sensors.

19.
ACS Appl Mater Interfaces ; 5(15): 6854-9, 2013 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-23859140

RESUMO

Materials that undergo stimulus-induced optical changes are important for many new technologies. In this paper, we describe a new free-standing silica-based composite film that exhibits reversible thermochromic reflection, induced by a liquid crystalline guest in the pores of iridescent mesoporous films. We demonstrate that selective reflection from the novel mesoporous organosilica material with chiral nematic organization can be reversibly switched by thermal cycling of the 8CB guest between its isotropic and liquid crystalline states, which was proven by solid-state NMR experiments. The switching of the optical properties of the chiral solid-state host by stimulus-induced transitions of the guest opens the possibility of applications for these novel materials in sensors and displays.

20.
Inorg Chem ; 52(13): 7666-72, 2013 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-23756021

RESUMO

The present study describes a series of pentafluorobenzyl ammonium salts with two, three, or four C6F5 units in order to investigate simultaneous interactions of several perfluorinated arenes with anions in the crystalline state. Most of the structures show multiple anion-π contacts. However, only 6·2HI reveals an effective encapsulation of the iodide ion by the aromatic units. For comparison, the structure of 4b is investigated because it offers two π-systems with inverse charge distribution to a bromide anion. Only the electron-deficient π-system of the pentafluorophenyl group interacts with the anion.

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