The Experts below are selected from a list of 35409 Experts worldwide ranked by ideXlab platform
Rafal Klajn - One of the best experts on this subject based on the ideXlab platform.
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Supramolecular Control of Azobenzene Switching on Nanoparticles
Journal of the American Chemical Society, 2019Co-Authors: Zonglin Chu, Yanxiao Han, Tong Bian, Petr Král, Rafal KlajnAbstract:The reversible photoisomerization of Azobenzene has been utilized to construct a plethora of systems in which optical, electronic, catalytic, and other properties can be controlled by light. However, owing to Azobenzene’s hydrophobic nature, most of these examples have been realized only in organic solvents, and systems operating in water are relatively scarce. Here, we show that by coadsorbing the inherently hydrophobic Azobenzenes with water-solubilizing ligands on the same nanoparticulate platforms, it is possible to render them essentially water-soluble. To this end, we developed a modified nanoparticle functionalization procedure allowing us to precisely fine-tune the amount of Azobenzene on the functionalized nanoparticles. Molecular dynamics simulations helped us to identify two distinct supramolecular architectures (depending on the length of the background ligand) on these nanoparticles, which can explain their excellent aqueous solubilities. Azobenzenes adsorbed on these water-soluble nanopartic...
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Reversible photoswitching of encapsulated Azobenzenes in water.
Proceedings of the National Academy of Sciences of the United States of America, 2018Co-Authors: Dipak Samanta, Julius Gemen, Zonglin Chu, Yael Diskin-posner, Linda J. W. Shimon, Rafal KlajnAbstract:Efficient molecular switching in confined spaces is critical for the successful development of artificial molecular machines. However, molecular switching events often entail large structural changes and therefore require conformational freedom, which is typically limited under confinement conditions. Here, we investigated the behavior of Azobenzene—the key building block of light-controlled molecular machines—in a confined environment that is flexible and can adapt its shape to that of the bound guest. To this end, we encapsulated several structurally diverse Azobenzenes within the cavity of a flexible, water-soluble coordination cage, and investigated their light-responsive behavior. Using UV/Vis absorption spectroscopy and a combination of NMR methods, we showed that each of the encapsulated Azobenzenes exhibited distinct switching properties. An Azobenzene forming a 1:1 host–guest inclusion complex could be efficiently photoisomerized in a reversible fashion. In contrast, successful switching in inclusion complexes incorporating two Azobenzene guests was dependent on the availability of free cages in the system, and it involved reversible trafficking of Azobenzene between the cages. In the absence of extra cages, photoswitching was either suppressed or it involved expulsion of Azobenzene from the cage and consequently its precipitation from the solution. This finding was utilized to develop an information storage medium in which messages could be written and erased in a reversible fashion using light.
Makoto Komiyama - One of the best experts on this subject based on the ideXlab platform.
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synthesis of Azobenzene tethered dna for reversible photo regulation of dna functions hybridization and transcription
Nature Protocols, 2007Co-Authors: Hiroyuki Asanuma, Xingguo Liang, Hidenori Nishioka, Daijiro Matsunaga, Makoto KomiyamaAbstract:A phosphoramidite monomer bearing an Azobenzene is synthesized from D-threoninol. Using this monomer, Azobenzene moieties can be introduced into oligodeoxyribonucleotide (DNA) at any position on a conventional DNA synthesizer. With this Azobenzene-tethered DNA, formation and dissociation of a DNA duplex can be reversibly photo-regulated by cis–trans isomerization of the Azobenzene. When the Azobenzene takes a trans-form, a stable duplex is formed. After isomerization of the trans-Azobenzene to its cis-form by UV-light irradiation (300 nm 400 nm). The introduction of Azobenzenes into the T7 promoter at specific positions also efficiently and reversibly photo-regulates transcription by T7-RNA polymerase. The reversible regulation can be repeated many times without causing damage to the DNA or the Azobenzene moiety. These procedures take approximately 10 d to complete. NOTE: In Figure 4 of the version of this article originally published online, the base sequence of the oligonucleotide was incorrect. The figure has been replaced in all versions of the article.
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Azobenzene tethered t7 promoter for efficient photoregulation of transcription
Journal of the American Chemical Society, 2006Co-Authors: Mingzhe Liu, Hiroyuki Asanuma, Makoto KomiyamaAbstract:Azobenzene was additionally introduced into side chain of T7 promoter for the photocontrol of transcription reaction by T7 RNA polymerase (T7 RNAP). When a single Azobenzene molecule was introduced into the T7 promoter either at the loop-binding region of the RNAP (−7 to −11 position) or at the unwinding region (−1 to −4 position), transcription was suppressed in the trans-form but proceeded faster in the cis-form. The amount of transcripts after UV irradiation with respect to that in the dark was 1.5−2.0-fold. Kinetic analysis of the transcription reaction revealed that the photoregulatory mechanism was different in these positions. The photoisomerization of an Azobenzene at the loop-binding region primarily affected Km. On the other hand, the isomerization of an Azobenzene at the unwinding region mainly affected kcat. Still more clear-cut photoregulation was achieved when two Azobenzenes were introduced into both loop-binding and unwinding regions, respectively: transcription proceeded 7.6-fold faster ...
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Photoregulation of DNA triplex Formation by Azobenzene
Journal of the American Chemical Society, 2002Co-Authors: Xingguo Liang, Hiroyuki Asanuma, Makoto KomiyamaAbstract:Formation and dissociation of DNA triplex are reversibly photoregulated by cis trans isomerization of the Azobenzene tethered to the third strand. When the Azobenzene takes the trans from, a stable triplex is formed. Upon the isomerization of trans-Azobenzene to its cis form by UV light irradiation (300 trans isomerization (lambda > 400 nm). The photoregulating activity significantly depends on the position of Azobenzene in the third strand, as well as on the geometric position (meta or para) of its amido substituent. For m-amidoAzobenzene, the photoregulation is the most effective when it is tethered to the 5'-end of the third strand. However, p-amidoAzobenzene should be introduced into the middle of the strand for effective regulation. In the optimal cases, the change of T(m) of the triplex, caused by the cis trans isomerization of Azobenzene, is greater than 30 degrees C. UV-visible and CD spectroscopy, as well as computer modeling studies, clearly demonstrate that the trans-Azobenzene intercalates between the base pairs in the target duplex and thus stabilizes the triplex by stacking interactions. On the other hand, nonplanar cis-Azobenzene destabilizes the triplex due to its steric hindrance against the adjacent base pairs.
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Photocontrol of DNA Duplex Formation by Using Azobenzene-Bearing Oligonucleotides
Chembiochem : a European journal of chemical biology, 2001Co-Authors: Hiroyuki Asanuma, Xingguo Liang, Takayuki Yoshida, Makoto KomiyamaAbstract:The duplex-forming activities of oligonucleotides can be photomodulated by incorporation of an Azobenzene unit. Upon isomerizing the trans-Azobenzene to the cis form by irradiation with UV light, the T(m) value of the duplex (with the complementary DNA) is lowered so that the duplex is dissociated. The duplex is formed again when the cis-Azobenzene is converted to the trans-Azobenzene by irradiation with visible light. The photoregulation is successful irrespective of the position of the Azobenzene unit in the oligonucleotides. The trans-Azobenzene in the oligonucleotides intercalates between two DNA base pairs in the duplexes and stabilizes them because of a favorable enthalpy change. The nonplanar structure of a cis-Azobenzene is unfavorable for such an interaction. These photoresponsive oligonucleotides are promising candidates for the regulation of various bioreactions.
Hiroyuki Asanuma - One of the best experts on this subject based on the ideXlab platform.
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effect of the ortho modification of Azobenzene on the photoregulatory efficiency of dna hybridization and the thermal stability of its cis form
Chemistry: A European Journal, 2010Co-Authors: Hidenori Nishioka, Xingguo Liang, Hiroyuki AsanumaAbstract:We synthesized various Azobenzenes methylated at their ortho positions with respect to the azo bond for more effective photoregulation of DNA hybridization. Photoregulatory efficiency, evaluated from the change of T(m) (DeltaT(m)) induced by trans-cis isomerization, was significantly improved for all ortho-modified Azobenzenes compared with non-modified Azobenzene due to the more stabilized trans form and the more destabilized cis form. Among the synthesized Azobenzenes, 4-carboxy-2',6'-dimethylAzobenzene (2',6'-Me-Azo), in which two ortho positions of the distal benzene ring with respect to carboxyl group were methylated, exhibited the largest DeltaT(m), whereas the newly synthesized 2,6-Me-Azo (4-carboxy-2,6-dimethylAzobenzene), which possesses two methyl groups on the two ortho positions of the other benzene ring, showed moderate improvement of DeltaT(m). Both NMR spectroscopic analysis and computer modeling revealed that the two methyl groups on 2',6'-Me-Azo were located near the imino protons of adjacent base pairs; these stabilized the DNA duplex by stacking interactions in the trans form and destabilized the DNA duplex by steric hindrance in the cis form. In addition, the thermal stability of cis-2',6'-Me-Azo was also greatly improved, but not that of cis-2,6-Me-Azo. Solvent effects on the half-life of the cis form demonstrated that cis-to-trans isomerization of all the modified Azobenzenes proceeded through an inversion route. Improved thermal stability of 2',6'-Me-Azo but not 2,6-Me-Azo in the cis form was attributed to the retardation of the inversion process due to steric hindrance between lone pair electrons of the pi orbital of the nitrogen atom and the methyl group on the distal benzene ring.
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synthesis of Azobenzene tethered dna for reversible photo regulation of dna functions hybridization and transcription
Nature Protocols, 2007Co-Authors: Hiroyuki Asanuma, Xingguo Liang, Hidenori Nishioka, Daijiro Matsunaga, Makoto KomiyamaAbstract:A phosphoramidite monomer bearing an Azobenzene is synthesized from D-threoninol. Using this monomer, Azobenzene moieties can be introduced into oligodeoxyribonucleotide (DNA) at any position on a conventional DNA synthesizer. With this Azobenzene-tethered DNA, formation and dissociation of a DNA duplex can be reversibly photo-regulated by cis–trans isomerization of the Azobenzene. When the Azobenzene takes a trans-form, a stable duplex is formed. After isomerization of the trans-Azobenzene to its cis-form by UV-light irradiation (300 nm 400 nm). The introduction of Azobenzenes into the T7 promoter at specific positions also efficiently and reversibly photo-regulates transcription by T7-RNA polymerase. The reversible regulation can be repeated many times without causing damage to the DNA or the Azobenzene moiety. These procedures take approximately 10 d to complete. NOTE: In Figure 4 of the version of this article originally published online, the base sequence of the oligonucleotide was incorrect. The figure has been replaced in all versions of the article.
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Azobenzene tethered t7 promoter for efficient photoregulation of transcription
Journal of the American Chemical Society, 2006Co-Authors: Mingzhe Liu, Hiroyuki Asanuma, Makoto KomiyamaAbstract:Azobenzene was additionally introduced into side chain of T7 promoter for the photocontrol of transcription reaction by T7 RNA polymerase (T7 RNAP). When a single Azobenzene molecule was introduced into the T7 promoter either at the loop-binding region of the RNAP (−7 to −11 position) or at the unwinding region (−1 to −4 position), transcription was suppressed in the trans-form but proceeded faster in the cis-form. The amount of transcripts after UV irradiation with respect to that in the dark was 1.5−2.0-fold. Kinetic analysis of the transcription reaction revealed that the photoregulatory mechanism was different in these positions. The photoisomerization of an Azobenzene at the loop-binding region primarily affected Km. On the other hand, the isomerization of an Azobenzene at the unwinding region mainly affected kcat. Still more clear-cut photoregulation was achieved when two Azobenzenes were introduced into both loop-binding and unwinding regions, respectively: transcription proceeded 7.6-fold faster ...
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Photoregulation of DNA triplex Formation by Azobenzene
Journal of the American Chemical Society, 2002Co-Authors: Xingguo Liang, Hiroyuki Asanuma, Makoto KomiyamaAbstract:Formation and dissociation of DNA triplex are reversibly photoregulated by cis trans isomerization of the Azobenzene tethered to the third strand. When the Azobenzene takes the trans from, a stable triplex is formed. Upon the isomerization of trans-Azobenzene to its cis form by UV light irradiation (300 trans isomerization (lambda > 400 nm). The photoregulating activity significantly depends on the position of Azobenzene in the third strand, as well as on the geometric position (meta or para) of its amido substituent. For m-amidoAzobenzene, the photoregulation is the most effective when it is tethered to the 5'-end of the third strand. However, p-amidoAzobenzene should be introduced into the middle of the strand for effective regulation. In the optimal cases, the change of T(m) of the triplex, caused by the cis trans isomerization of Azobenzene, is greater than 30 degrees C. UV-visible and CD spectroscopy, as well as computer modeling studies, clearly demonstrate that the trans-Azobenzene intercalates between the base pairs in the target duplex and thus stabilizes the triplex by stacking interactions. On the other hand, nonplanar cis-Azobenzene destabilizes the triplex due to its steric hindrance against the adjacent base pairs.
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Photocontrol of DNA Duplex Formation by Using Azobenzene-Bearing Oligonucleotides
Chembiochem : a European journal of chemical biology, 2001Co-Authors: Hiroyuki Asanuma, Xingguo Liang, Takayuki Yoshida, Makoto KomiyamaAbstract:The duplex-forming activities of oligonucleotides can be photomodulated by incorporation of an Azobenzene unit. Upon isomerizing the trans-Azobenzene to the cis form by irradiation with UV light, the T(m) value of the duplex (with the complementary DNA) is lowered so that the duplex is dissociated. The duplex is formed again when the cis-Azobenzene is converted to the trans-Azobenzene by irradiation with visible light. The photoregulation is successful irrespective of the position of the Azobenzene unit in the oligonucleotides. The trans-Azobenzene in the oligonucleotides intercalates between two DNA base pairs in the duplexes and stabilizes them because of a favorable enthalpy change. The nonplanar structure of a cis-Azobenzene is unfavorable for such an interaction. These photoresponsive oligonucleotides are promising candidates for the regulation of various bioreactions.
Christopher J Barrett - One of the best experts on this subject based on the ideXlab platform.
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shaping crystals with light crystal to crystal isomerization and photomechanical effect in fluorinated Azobenzenes
Journal of the American Chemical Society, 2013Co-Authors: Oleksandr S Bushuyev, Anna Tomberg, Tomislav Friscic, Christopher J BarrettAbstract:Unusually long thermal half-lives of perhalogenated cis-Azobenzenes enabled their structural characterization and the first evidence of a crystal-to-crystal cis → trans Azobenzene isomerization. Irradiation with visible light transforms a perhalogenated cis-Azobenzene single crystal into a polycrystalline aggregate of its trans-isomer in a photomechanical transformation that involves a significant, controllable, and thermally irreversible change of crystal shape. This is the first demonstration of permanent photomechanical modification of crystal shape in an Azobenzene.
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Novel photo-switching using Azobenzene functional materials
Journal of Photochemistry and Photobiology A: Chemistry, 2006Co-Authors: Kevin G. Yager, Christopher J BarrettAbstract:Abstract Azobenzene (azo) chromophores have been incorporated into a wide variety of materials and molecular architectures, including polymers, dendrimers, and molecular glasses. Azobenzene exhibits a uniquely clean and efficient photochemistry, with facile geometric isomerization about the azo bond, converting the molecule from trans to cis . This review discusses the extensive number of investigations of Azobenzene photo-switching and photo-modulation. In particular, azos can be used to alter material behaviour with light, switching both molecular and macroscopic properties. A large number of photobiological studies have shown that interfacing the azo chromophore with enzymes and biopolymers is feasible and useful. The all-optical surface patterning unique to Azobenzenes is also reviewed. Lastly, Azobenzene photomechanical effects are discussed.
Nobuyuki Tamaoki - One of the best experts on this subject based on the ideXlab platform.
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Photocontrol of New Molecular Functions by the Isomerization of Azobenzene
New Frontiers in Photochromism, 2013Co-Authors: Nobuyuki TamaokiAbstract:Azobenzene shows the reversible E–Z photoisomerization upon near ultraviolet (UV) and blue light irradiations. By utilizing changes in the molecular length and polarity of Azobenzene in this isomerization, Azobenzene has been applied as the molecular switching unit of various molecular functional materials. In this chapter some recent challenges on the photoswitching of new molecular functions using Azobenzene derivatives were described. They include the molecular chirality and molecular machines. The feature of these molecular functions is that the control is not accomplished until fine tuning of inter- or intramolecular motions. The racemization of the planar chiral macrocycles 2 and 5 is photochemically and dynamically controlled for the first time by controlling intramolecular free rotation of an asymmetric rotor unit by photoisomerization of an Azobenzene moiety in macrocycles. Under circular polarized lights it was possible to enrich one of the enantiomers of 5 as the results of different efficiency of the photoisomerization between racemizing Z isomer and the nonracemizing E enantiomers. It was also demonstrated that point chirality was dynamically introduced by the E–Z photoisomerization of one of the Azobenzenes in the methane derivatives substituted with two identical Azobenzenes. In the study of molecular machine the sliding motion of a motor protein, kinesin-microtubule, can be controlled by the photoisomerization of Azobenzene unit introduced to a monomolecular layer underneath the kinesin or in the adenosine triphosphate (ATP) served as an energy source.
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Photochemical and Thermal cis/trans Isomerization of Cyclic and Noncyclic Azobenzene Dimers: Effect of a Cyclic Structure on Isomerization
European Journal of Organic Chemistry, 2006Co-Authors: Yasuo Norikane, Nobuyuki TamaokiAbstract:The effect of ring strain on the photochemical and thermal isomerization of Azobenzene dimers was investigated by comparison of macrocyclic (1) and noncyclic (2) Azobenzene dimers. The macrocycle 1 comprises two Azobenzene moieties connected at their meta positions through two methylene linkers, whereas the noncyclic dimer 2 has only one methylene linker bridging two Azobenzenes at the meta positions. Upon irradiation of 1 or 2 with UV light, each (E/E )( trans/ trans) isomer exhibited a stepwise photoisomerization to give the corresponding (E/Z )( trans/cis) isomer, followed by isomerization to yield the (Z/Z )( cis/cis) isomer. Quantum yields for the isomerization indicated that the photochemical isomerizations of 1 were altered by its cyclic structure. The effect
