Modeling Structures and Spectra of Fluorescent Proteins in the Coordinate-Locking Cluster Approach: Application to the Photoswitchable Protein AsFP595

An interest in the fluorescent protein asFP595 is due to unexplained puzzles in its photophysical behavior. We report the results of calculations of structures, absorption, and emission bands in asFP595 by considering model molecular clusters in the coordinate-locking scheme. Both trans and cis conformations of the anionic chromophore are considered. Equilibrium geometry coordinates on the ground potential energy surface were optimized in the density functional theory approaches by considering both large- and reduced-size clusters. The cluster size was reduced to locate positions of the minimum energy points on the excited-state potential surface by using the configuration interaction singles approach. Vertical excitation energies and oscillator strengths were computed by using the ZINDO method. We show that consideration of large clusters mimicking the protein-containing pocket is an essential issue to calculate positions of absorption and emission bands with the accuracy compatible to experiments.

Photoswitchable Molecular Recognition Enabled by Dithienylethene-Mediated Structural Changes of Dynamic Covalent Hydrazone Bonds

Light-induced recognition,assemblies,and materials are intensive areas of research due to their high spatiotemporal resolution.Herein,we demonstrated photoswitchable molecular recognition via dithienylethene-triggeredreversible structural regulation of dynamic covalent hydrazone bonds.By combining dithienylethenes and cyclic hemiacetals,the photochemical open-ring and closed-ring forms enabled turningoff and on the creation of awide range of hydrazones when desired.Light-induced bidirectional switching between hydrazones and their cyclization structures promoted by a neighboring carboxyl group was further achieved.By taking advantage of reversible structural changes totoggleon andoff the binding pocket,photoswitchable recognitionofmetal ionswas realized.Finally,the construction of an acylhydrazone polymer offered a facile way for light-mediated selective extraction/release.The strategies and results reported here should find applications in many contexts,such asdynamicassemblies,molecular switches,and smart materials.

Preparation and study of photoswitchable fluorescence nanoparticles based on spirobenzopyran

The preparation and performance characterization of〈50 nm spirobenzopyran-based photochromic nanocomposites with photoswitchable fluorescence are presented.The nanocomposites were fabricated by means of a modifed miniemulsion polymerization process,in which the hydrophobic spirobenzopyran was covalently attached to the polymer chains and the matched fluorescent dyes were noncovalently embedded in the nanoscale cross-linked polymeric matrix,respectively.The obtained nanocomposites with a high relative fluorescence quantum yield（Q）exhibited superior fluorescent photoswitchable performance due to the effective photo-induced intermolecular energy transfer.The stability of photomerocyanine was also improved.

A New Set of Reversibly Photoswitchable Fluorescent Proteins for Use in Transgenic Plants

Fluorescent reporter proteins that allow repeated switching between a fluorescent and a non-fluorescent state in response to specific wavelengths of light are novel tools for monitoring of protein trafficking and super-resolu- tion fluorescence microscopy in living organisms. Here, we describe variants of the reversibly photoswitchable fluores- cent proteins rsFastLime, bsDronpa, and Padron that have been codon-optimized for the use in transgenic Arabidopsis plants. The synthetic proteins, designated rsFastLIME-s, bsDRONPA-s, and PADRON C-s, showed photophysical properties and switching behavior comparable to those reported for the original proteins. By combining the ＇positively switchable＇ PADRON C-s with the ＇negatively switchable＇ rsFastLIME-s or bsDRONPA-s, two different fluorescent reporter proteins could be imaged at the same wavelength upon transient expression in Nicotiana benthamiana cells. Thus, co-localiza- tion analysis can be performed using only a single detection channel. Furthermore, the proteins were used to tag the RNA-binding protein AtGRP7 （Arabidopsis thaliana glycine-rich RNA-binding protein 7） in transgenic Arabidopsis plants. Because the new reversibly photoswitchable fluorescent proteins show an increase in signal strength during each pho- toactivation cycle, we were able to generate a large number of scans of the same region and reconstruct 3-D images of AtGRP7 expression in the root tip. Upon photoactivation of the AtGRP7：rsFastLIME-s fusion protein in a defined region of a transgenic Arabidopsis root, spreading of the fluorescence signal into adjacent regions was observed, indicating that movement from cell to cell can be monitored. Our results demonstrate that rsFastLIME-s, bsDRONPA-s, and PADRON C-s are versatile fluorescent markers in plants, Furthermore, the proteins also show strong fluorescence in mammalian cells including COS-7 and HeLa cells.

Photoswitchable molecular dipole antennas with tailored coherent coupling in glassy composite

Here,we introduce the first experimental proof of coherent oscillation and coupling of photoswitchable molecules embedded randomly in a polymeric matrix and acting cooperatively upon illumination with UV light.In particular,we demonstrate the specular reflection and Brewster phenomenon alteration of photochromic molecular dipole antennas.We successfully demonstrate the concept of Brewster wavelength,which is based on the dipolar interaction between radiating dipoles and the surrounding matrix possessing a net dipole moment,as a key tool for highly localized sensing of matrix polarity.We also introduce the concept of‘tailored molecular photonic coupling’while highlighting the role of interferences for the design of optically active media by adjusting the photonic response of the medium with the real and imaginary refractive index of photoswitchable molecules in the‘ON’state.Our results enhance our fundamental understanding of coherent dipole radiation and open a new vein of research based on glassy disordered dipolar composites that act as macroscopic antenna with cooperative action;furthermore,these results have important implications for new design rules of tailored photonics.

Rational construction of self-assembly azobenzene derivative monolayers with photoswitchable surface properties

Photo-responsive azobenzene （ABZ） derivatives with different end groups （R） as photoswitchable molecules were employed to construct self-assembled monolayers （SAMs） on silicon substrate by using 3-glycidoxypropyltrimethoxysilane （GPTS） as the bridging molecules. The assembly process was optimized by changing various parameters, including the type and concentration of ABZ derivatives, reaction time, etc. The obtained SAMs were fully characterized and evaluated using UV spectroscopy, atomic force microscope （AFM）, elllipsometer, static contact angle and X-ray photoelectron spectroscopy （XPS）. It is found that the end group property of azobenzene derivatives is critical to the obtained SAMs＇ photoresponsive properties. Compared with hydrophobic compounds （4-（4＇-aminophenylazo） benzoic acid, ABZ-CF3）, the hydrophilic compounds （4-（4＇-aminophenylazo） benzoic acid, ABZ-COOH） show excellent reversible photoswitching performance with a large contact angle change of 35° under oDtimized process, and the SAMs are removable bv thermal treatment at 240 ℃ in air for onlv 5 min.

Photoswitchable vibrational nanoscopy with sub-100-nm optical resolution

Stimulated Raman scattering(SRS)microscopy has shown superior chemical resolution due to the much narrower vibrational spectral bandwidth than its fluorescence counterpart.However,breaking the diffraction-limited spatial resolution of SRS imaging is much more challenging because of the intrinsically weak scattering cross section and inert/stable nature of molecular bond vibrations.We report superresolution SRS(SR-SRS)nanoscopy based on reversible-switchable vibrational photochromic probes integrated with point spread function engineering strategy.By introducing a Gaussian-shaped ultraviolet excitation beam and a donut-shaped visible depletion beam in addition to the pump and Stokes beams,SR-SRS could reach sub-100 nm resolution on photoswitchable nanoparticles(NPs).Furthermore,NP-treated live cell imaging was demonstrated with resolution improvement by a factor of∼4.Our proof-of-principle work provides the potential for SR vibrational imaging to assist research on complex biological systems.

Optical control of neuronal activities with photoswitchable nanovesicles

Precise modulation of neuronal activity by neuroactive molecules is essential for understanding brain circuits and behavior.However,tools for highly controllable molecular release are lacking.Here,we developed a photoswitchable nanovesicle with azobenzene-containing phosphatidylcholine(azo-PC),coined‘azosome’,for neuromodulation.Irradiation with 365 nm light triggers the trans-to-cis isomerization of azo-PC,resulting in a disordered lipid bilayer with decreased thickness and cargo release.Irradiation with 455 nm light induces reverse isomerization and switches the release off.Real-time fluorescence imaging shows controllable and repeatable cargo release within seconds(<3 s).Importantly,we demonstrate that SKF-81297,a dopamine D1-receptor agonist,can be repeatedly released from the azosome to activate cultures of primary striatal neurons.Azosome shows promise for precise optical control over the molecular release and can be a valuable tool for molecular neuroscience studies.

Comparison of two thioxopeptide bond photoswitches in insect kinin

The photoisomerization abilities of secondary thioxopeptide bond(CS-NH) and thioxo prolyl bond(CS-N) incorporated into the C-terminal pentapeptide of insect kinin were compared.H-Phe-Phe-Ψ[CS-NH]-D-Ala-Trp-Gly-NH_2 and H-Phe-Tyr-Ψ[CS-N]- Pro-Trp-Gly-NH_2 were studied by UV-vis absorption.The isomerization energy barriers of the two segments,Ac-Phe-Ψ[CS-NH]- D-Ala-NH_2 and Ac-Tyr-Ψ[CS-N]-Pro-NH_2 picked from the two peptides,were calculated using ab initio method.The cis isomer of CS-N is more stable than th...

Enhancing tetraphenylethene cyclization as photoswitch

Tetraphenylethene(TPE),a star building block with promising aggregationinduced emission,has received much interest.Given that its intramolecular Woodward-Hoffmann cyclic intermediate instantaneously converts back to the original state within several picoseconds,the essentially photochromic characteristic of TPE is little investigated.Achieving a visible photocyclization of TPE is still an unsolved issue and considered as the bottleneck in the further advancement of applications.We report a strategy of attaching carbonate ester onto the TPE skeleton(TPE-4C)to enhance TPE photocyclization stability.As demonstrated,the incorporated cholesteryloxycarbonyloxy substituents in TPE-4C can increase the energy barrier for cycloreversion,thereby exhibiting extremely thermal stability of photocyclic intermediate upon UV irradiation,prolonging its lifetime from 63 picoseconds to 46 s by 7.2×10^(11)-fold.The photoinduced cyclization of TPE-4C could be monitored with naked eyes,and the photocyclization/cycloreversion is achieved by turning on/off UV light along with a relative fatigue resistance.Encapsulation of TPE-4C into the liquid crystal can induce a striking phase transformation(achiral↔chiral),which can be applicable to encode optical information.Employing carbonate ester into the TPE unit plays a vital role in enhancing the unprecedented TPE photocyclization stability,providing a toolbox to allow TPE-based photocyclization to be visually monitored.

Light-triggered fluorochromic cholesteric liquid crystal elastomer with hydrogen-bonded fluorescent switch: dualmodal-switchable circularly polarized luminescence

Solid materials with dynamically tunable circularly polarized luminescence(CPL) feature higher security levels and devicefriendly characteristics, showing great superiority in the field of information technology and anti-counterfeiting. To address the limited photoisomerization of fluorescent photoswitch in CPL-active solid materials, here a cholesteric liquid crystal elastomer(CLCE) containing a hydrogen-bonded(H-bonded) polymerizable fluorescent switch AHBA-PSD is prepared. Owing to the good flexibility and low glass-transition temperature of CLCE, AHBA-PSD shows a fast and fully reversible photocyclization/cycloreversion with fluorochromic behavior in CLCE. Further, by controlling the spectral overlapping area between the emission and reflection bands, the CLCE exhibits a strong CPL with a g_(lum) value of up to 0.76 accompanied by a reversible phototunable CPL signal. Meanwhile, the H-bond helps to stabilize the mechanical property, and the force-induced switching-off of CPL signal could be achieved due to the destroyed helical structures by external force. Finally, an automatically-recognized identification card with abundant chiroptical information is demonstrated.

Multicolor upconversion reversible modulations in YNbO_(4):Er^(3+)/Tm^(3+)/Yb^(3+) photochromic materials

Photochromic materials with multicolor upconversion reversible modulations are attractive in optical switching devices.Herein,the fabricated YNbO_(4):Er^(3+)/Tm^(3+)/Yb^(3+) materials exhibit excellent photochromism and multicolor upconversion properties from green,red to near infrared(NIR) emissions with increasing Yb concentrations.Reversible multiband upconversion modulations are achieved by alternating light(365 and 405 nm) or thermal stimuli.After 365 nm irradiation,the luminescence color changes from yellow to red,the luminescent photoswitching contrast reaches up to 86.21%(green),82.12%(red) and 77.38%(NIR) in the Y_(0.83)Er_(0.01)Tm_(0.01)NbO_(4):0.15 Yb sample.Besides,the upconversion emission intensity before and after photochromic reaction shows remarkable change in a wide temperature range of 298-718 K.These results indicate that the Er^(3+)/Tm^(3+)/Yb^(3+) tri-doped YNbO_(4) materials can be a good candidate in optical switching and data storage applications.

A New Chirality Invertible Photoswitch:Light-Driven Axially Chiral Hydrazone Enabling Dynamic Handedness Inversion of Self-Organized Helical Superstructure

Inspired by nature,dynamic self-organized helical superstructures are becoming attractive as building blocks in soft photonic crystals and advanced chiroptical devices.Herein,a chirality invertible hydrazone photoswitch,possessing high helical twisting power(HTP)was judiciously designed and synthesized.Due to the photoinduced configuration changes of the hydrazone photoswitch,it displayed superior thermal stability and strikingly reversible HTP changes.By incorporating a novel chiral hydrazone(CH)into the liquid crystal(LC)host,a handedness invertible cholesteric liquid crystal(CLC)helical superstructure with high thermal stability and light-modulated photonic bandgap was prepared.We inferred that the mechanism of chirality inversion of the novel CH photoswitch derived from changes in the dihedral angle between the two naphthalene rings induced by hydrazone isomerization.Therefore,the influence of chemical structures on its photoresponsiveness was explored.Finally,the potential applications of this advanced light-driven CLC in soft photonic crystals,showing erasable and rewritable colorful patterns and chiroptical templates to induce handedness invertible circularly polarized luminescence were illustrated.

Photoresponsive nucleic acids for gene regulation

For the main purpose of manipulating the functions of molecules, researchers have made great achievements on photoresponsive molecules using light as a trigger. Light has become a promising scientific tool due to it being a clean and noninvasive external stimulant. By attachment of photoresponsive moieties to molecules, the biological activities of molecules can be attenuated by light activation. With wide applications of laser in life sciences, it will be possible to achieve high spatiotemporal resolution. In this review, we focus on photoresponsive nucleic acids for photomodulating gene expression with light activation. With incorporation of photoswitchable or photocleavable moieties, biological behaviors of nucleic acids are photoregulated reversibly or irreversibly. Recent development and applications of photoresponsive nucleic acid in vitro and in vivo have shown a very promising future for manipulation of specific functional genes or disease genes. We expect that photoresponsive nucleic acids will be powerful scientific tools for studying biological events as well as gene therapy agents for genetic diseases.

Photogated proton conductivity of ZIF-8 membranes co-modified with graphene quantum dots and polystyrene sulfonate

Smart proton conductive metal-organic framework(MOF) membranes with dynamic remote control over proton conduction show high potential for use in advanced applications, such as sensors and bioprocesses. Here, we report a photoswitchable proton conductive ZIF-8 membrane by coencapsulating polystyrene sulfonate and graphene quantum dots into a ZIF-8 matrix(GQDs-PSS@ZIF-8) via a solidconfined conversion process. The proton conductivity of the GQDs-PSS@ZIF-8 membrane is 6.3 times higher than that of pristine ZIF-8 and can be reversibly switched by light due to photoluminescence quenching and the photothermal conversion effect, which converts light into heat. The local increase in temperature allows water molecules to escape from the porous channels, which cuts off the proton transport pathways and results in a decrease in proton conductivity. The proton conductivity is restored when the light is off owing to regaining water molecules, which act as proton carriers, from the surroundings. The GQDs-PSS@ZIF-8 membrane responds efficiently to light and exhibits an ON/OFF ratio of 12.8. This photogated proton conduction in MOFs has potential for the development and application of MOF-based protonic solids in advanced photoelectric devices.

基于可重构光开关多态荧光聚合物的信息加密工具箱

具有坚固、智能、且易于编程等特性的信息加密材料对于防止信息泄露和打击造假具有重要意义.为此,我们开发了一种信息加密材料工具箱,该工具箱基于一系列新型的自修复光开关双态(P1和P2)和多态(P3)荧光聚合物.这类聚合物含有两种二芳基乙烯光致变色荧光基团(SDTE和BTBA)和四重氢键构筑单元(UPy).在不同波长的光照射下,P1/P2可以在绿-猝灭/红-猝灭两态之间交替,而P3可以在红-绿-猝灭三态之间变化.它们可以作为像素单元用来制备可重构的图案和代码;所得到的图案和代码均显示出良好的机械性能和优异的光学特性,包括快速的光响应性、突出的光可逆性、优异的荧光热稳定性和抗酸碱腐蚀的能力.本文展示了该工具箱在3D代码阵列和二维码信息加密中的应用潜能.

Direct van der Waals epitaxial growth of 1D/2D Sb2Se3/WS2 mixed-dimensional p-n heterojunctions

The mixed-dimensional integration of two-dimensional (2D) materials with non-2D materials can give rise to prominent advances in performance or function.To date,the mixed-dimensional one-dimensional (1D)/2D heterostructures have been fabricated using various physical assembly approaches.However,direct epitaxial growth method which has notable advantages in preparing large-scale products and obtaining perfect interfaces is rarely investigated.Herein,we demonstrate for the first time the direct synthesis of the 1D/2D mixed-dimensional heterostructures by sequential vapor-phase growth of Sb2Se3 nanowires on WS2 monolayers.X-ray diffraction (XRD) pattern and Raman spectrum confirm the composition of the Sb2Se3/NS2 heterostructures.Transmission electron microscope (TEM) measurement demonstrates high quality of the heterostructures.Electrical transport characterization reveals that Sb2Se3 nanowire exhibits p-type characteristic and that WS2 monolayer exhibits n-type behavior,and that the p-n diode from 1D/2D mixed-dimensional Sb2Se3/WS2 heterostructure possesses obvious current rectification behavior.Optoelectronic measurements of the heterostructures show apparent photovoltaic response with an open-circuit voltage of 0.19 V,photoresponsivity of 1.51 A/W (Vds =5 V) and fast response time of less than 8 ms.The van der Waals epitaxial growth mode of Sb2Se3 nanowires on WS2 monolayers is verified by stripping the Sb2Se3 nanowire from the heterostructures using tape.Together,the direct van der Waals epitaxy opens a facile pathway to 1D/2D mixed-dimensional heterostructures for functional electronic and optoelectronic devices.

Rational design of a visible-light photochromic diarylethene:a simple strategy by extending conjugation with electron donating groups

Photochromic diarylethenes have been widely used in many fields. However, their cyclization process must be induced by UV light. In this article, a simple strategy is developed by extending π-conjugation with electron donating groups. The modified dirylethene derivative can photocyclolize under 405-nm light with a good photochromic efficiency. Meanwhile, its absorption and moderate fluorescence can be switched effectively in both directions by visible lights(405 and 520 nm, respectively) in different solutions and in living cells. We believe that this simple method will become a versatile strategy for developing various dirylethylenes with visible-light photochromism.

Photo-Modulation of Gene-Editing Enzymes CRISPR/Cas9 with Bifunctional Small-Molecule Ligands

The control of protein functions with light is valuable for spatiotemporal probing of biological systems.Current small-molecule photo-modulation methods include the light-induced uncaging of inhibitors and chromophore-assisted light inactivation with reactive oxygen species(ROS).However,the constant target protein expression results in inadequate photo-modulation efficiency,particularly for less potent inhibitors and chromophores.Herein,we report a novel bifunctional small-molecule ligands strategy to photo-modulate gene-editing enzymes CRISPR/Cas9.A coumarin-derived small-molecule ligand Bhc-BRD0539 is developed to uncage the active inhibitor upon light irradiation and to generate ROS in the Cas9 proximity for the dual inhibition of Cas9 activity.Our results highlight the synergistic photo-modulation with bifunctional small-molecule ligands,which offers a valuable addition to current CRISPR/Cas9 photo-modulation technologies and may extend to other protein classes.

Process-controllable modulation of plasmon-induced transparency in terahertz metamaterials

Recently reported plasmon-induced transparency(PIT)in metamaterials endows the optical structures in classical systems with quantum optical effects.In particular,the nonreconfigurable nature in metamaterials makes multifunctional applications of PIT effects in terahertz communications and optical networks remain a great challenge.Here,we present an ultrafast process-selectable modulation of the PIT effect.By incorporating silicon islands into diatomic metamaterials,the PIT effect is modulated reversely,depending on the vertical and horizontal configurations,with giant modulation depths as high as 129%and 109%.Accompanied by the enormous switching of the transparent window,remarkable slow light effect occurs.