Carrying out chemical transformations under environmentally sustainable conditions has become one of the important current goals of chemistry. In this context, conducting reactions under solvent-free conditions (crystals, zeolites, clay, etc.) and in water has attracted considerable attention. Since most molecules either do not crystallize and or do not dissolve in water, the two approaches are complimentary. To make molecules solubilize in water one needs to employ water-soluble hosts such as micelles, cavitands, and capsules. To achieve selectivity, one should provide a confined environment within which the motions of reactant molecules are restricted to that in free solution. The confined space in which the reaction takes place independent of the host environment could be defined in terms of the “reaction cavity” originally presented by Cohen and Schmidt. In this mini-review, examples of photodimerization of olefins carried out in cavitands such as cucurbiturils, cyclodextrins, calixarenes, and octa acid are presented. Results are discussed in terms of the reaction cavity concept, which is applicable to reactions in both solids and water. 相似文献
The development of multifunctional supramolecular nanocomposite hydrogels remains challenging. Here, the dynamic host–guest interactions involving the host molecule CB[8] and guest units were utilized to prepare Fe3O4 hybrid supramolecular nanocomposite hydrogels. The results showed that the hydrogels obtained possessed a porous structure. The CB[8]-modified Fe3O4 (Fe3O4@CB[8]) nanoparticles served as cross-linkers in forming the network of hydrogels. By adjusting the Fe3O4@CB[8] content, the mechanical properties of the hydrogels could be controlled. The tensile stress was measured at 160 kPa with a fracture strain of 1380%, while the compression stress was 230 kPa at 70% compression strain. The self-healing efficiency of the hydrogels at room temperature reached 95% after 24 h. The as-obtained hydrogels show strain sensitivity and have the potential for applications in detecting elbow and finger movements. Our supramolecular nanocomposite hydrogels exhibit multiple functions, including self-healing, injectability, photothermal responsiveness, and conductivity, making them suitable for integration into flexible electronics. 相似文献
BODIPY photosensitizers have been integrated with a hypoxia-activated prodrug to achieve synergistic photodynamic therapy (PDT) and chemotherapy. A novel BODIPY derivative BDP-CN was designed and synthesized. It had two cyano groups to make it complex well with a water-soluble pillar[5]arene. Their association constant was calculated to be (6.8±0.9)×106 M−1. After self-assembly in water, regular spherical nanocarriers can be formed; these were used to encapsulate the hypoxia-activated prodrug tirapazamine (TPZ). BDP-CN displayed excellent photodynamic activity to complete PDT. In this process, O2 can be continuously consumed to activate TPZ to allow it to be converted to a benzotriazinyl (BTZ) radical with high cytotoxicity to complete chemotherapy. As a result, the formed nanoparticles showed excellent synergistic photodynamic therapy and chemotherapy efficacy. The synergistic therapy mechanism is discussed in detail. 相似文献
Auxin, a plant hormone, is polar transported from its site of production. This auxin polar transport system establishes an auxin gradient in plant tissue that is necessary for proper plant development. Therefore, the spatial effect of the auxin gradient on plant development is highly important for the understanding of plant auxin responses. Herein we report the design, syntheses and biological properties of esterase‐resistant caged auxins. The conventional caging group, 2‐nitrobenzyl ester, was found to be enzymatically hydrolyzed in plant cells and released original auxin without photolysis. The esterase‐resistant caging group, (2,5‐dimethoxyphenyl)(2‐nitrobenzyl) ester, (DMPNB) was designed to improve the stability of caged auxins. Three auxins, indole 3‐acetic acid, naphthalene 1‐acetic acid and 2,4‐dichlorophenoxy acetic acid were caged with the DMPNB caging group. DMPNB‐caged auxins were inactive within a plant cell until photolysis, but they release auxins with photoirradiation to activate auxin‐responsive gene expression. We demonstrated spatial and temporal control of intracellular auxin levels with photoirradiation by using this caged auxin system and were able to photocontrol the physiological auxin response in Arabidopsis plants. Additionally, the photoirradiation of DMPNB‐caged auxin within a single cell can manipulate the intracellular auxin level and triggers auxin response.相似文献
Photolabile protecting groups play a significant role in controlling biological functions and cellular processes in living cells and tissues, as light offers high spatiotemporal control, is non-invasive as well as easily tuneable. In the recent past, photo-responsive inducer molecules such as 6-nitropiperonyl-caged IPTG (NP-cIPTG) have been used as optochemical tools for Lac repressor-controlled microbial expression systems. To further expand the applicability of the versatile optochemical on-switch, we have investigated whether the modulation of cIPTG water solubility can improve the light responsiveness of appropriate expression systems in bacteria. To this end, we developed two new cIPTG derivatives with different hydrophobicity and demonstrated both an easy applicability for the light-mediated control of gene expression and a simple transferability of this optochemical toolbox to the biotechnologically relevant bacteria Pseudomonas putida and Bacillus subtilis. Notably, the more water-soluble cIPTG derivative proved to be particularly suitable for light-mediated gene expression in these alternative expression hosts. 相似文献
Photocaged compounds are applied for implementing precise, optochemical control of gene expression in bacteria. To broaden the scope of UV-light-responsive inducer molecules, six photocaged carbohydrates were synthesized and photochemically characterized, with the absorption exhibiting a red-shift. Their differing linkage through ether, carbonate, and carbamate bonds revealed that carbonate and carbamate bonds are convenient. Subsequently, those compounds were successfully applied in vivo for controlling gene expression in E. coli via blue light illumination. Furthermore, benzoate-based expression systems were subjected to light control by establishing a novel photocaged salicylic acid derivative. Besides its synthesis and in vitro characterization, we demonstrate the challenging choice of a suitable promoter system for light-controlled gene expression in E. coli. We illustrate various bottlenecks during both photocaged inducer synthesis and in vivo application and possibilities to overcome them. These findings pave the way towards novel caged inducer-dependent systems for wavelength-selective gene expression. 相似文献
We report the synthesis and properties of a photoactivatable caged RGD peptide and its application for phototriggering integrin- and cell-binding to surfaces. We analysed in detail 1) the differences in the integrin-binding affinity of the caged and uncaged forms by quartz crystal microbalance (QCM) studies, 2) the efficiency and yield of the photolytic uncaging reaction, 3) the biocompatibility of the photolysis by-products and irradiation conditions, 4) the possibility of site, temporal and density control of integrin-binding and therefore human cell attachment, and 5) the possibility of in situ generation of cell patterns and cell gradients by controlling the UV exposure. These studies provide a clear picture of the potential and limitations of caged RGD for integrin-mediated cell adhesion and demonstrate the application of this approach to the control and study of cell interactions and responses. 相似文献
Remote control of cells : A polypeptide has been made that stimulates proliferation and migration of cells upon photochemical activation. This light‐activated polypeptide enables spatially defined control of cell populations at the scale of tissue organization; this is accomplished without physically contacting the cells or modifying their substrate.
The creation of caged molecules involves the attachment of protecting groups to biologically active compounds such as ligands, substrates and drugs that can be removed under specific conditions. Photoremovable caging groups are the most common due to their ability to be removed with high spatial and temporal resolution. Here, the synthesis and photochemistry of a caged inhibitor of protein farnesyltransferase is described. The inhibitor, FTI, was caged by alkylation of a critical thiol group with a bromohydroxycoumarin (Bhc) moiety. While Bhc is well established as a protecting group for carboxylates and phosphates, it has not been extensively used to cage sulfhydryl groups. The resulting caged molecule, Bhc-FTI, can be photolyzed with UV light to release the inhibitor that prevents Ras farnesylation, Ras membrane localization and downstream signaling. Finally, it is shown that Bhc-FTI can be uncaged by two-photon excitation to produce FTI at levels sufficient to inhibit Ras localization and alter cell morphology. Given the widespread involvement of Ras proteins in signal transduction pathways, this caged inhibitor should be useful in a plethora of studies. 相似文献
Ligand-based NMR screening represents a powerful method in fragment-based drug discovery for the identification of chemical matter interacting with the receptor of interest. The large dynamic range of these methods allows the detection of weakly binding ligands. However, the methodology has not been extensively used for quantifying the strength of these interactions. This knowledge is important for ranking fragments according to their binding strength and for prioritizing structure-based and medicinal chemistry activities. Rapid NMR methods for measuring the dissociation constant in direct and competition modes are presented here. The theory underpinning these methods are presented, along with their application to the measurement of the binding affinities of several ligands of the heat shock protein 90. 相似文献
