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Plasmon-Enhanced Fluorescent Sensor based on Aggregation-Induced Emission for the Study of Protein Conformational Transformation
摘要： The alteration in protein conformation not only affects the performance of its biological functions, but also leads to a variety of protein-mediated diseases. Developing a sensitive strategy for protein detection and monitoring its conformation changes is of great significance for the diagnosis and treatment of protein conformation diseases. Herein, a plasmon-enhanced fluorescence (PEF) sensor is developed, based on an aggregation-induced emission (AIE) molecule to monitor conformational changes in protein, using prion protein as a model. Three anthracene derivatives with AIE characteristics are synthesized and a water-miscible sulfonate salt of 9,10-bis(2-(6-sulfonaphthalen-2-yl)vinyl)anthracene (BSNVA) is selected to construct the PEF–AIE sensor. The sensor is nearly non-emissive when it is mixed with cellular prion protein while emits fluorescence when mixed with disease-associated prion protein (PrPSc). The kinetic process of conformational conversion can be monitored through the fluorescence changes of the PEF–AIE sensor. By right of the amplified fluorescence signal, this PEF–AIE sensor can achieve a detection limit 10 pM lower than the traditional AIE probe and exhibit a good performance in human serum sample. Furthermore, molecular docking simulations suggest that BSNVA tends to dock in the β-sheet structure of PrP by hydrophobic interaction between BSNVA and the exposed hydrophobic residues.
关键词： fluorescence sensor,protein conformation,aggregation-induced emission,prion protein,plasmonic enhancement
更新于2025-11-19 16:46:39
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Planar Antiaromatic Core-Modified 24π Hexaphyrin(1.0.1.0.1.0) and 32π Octaphyrin(1.0.1.0.1.0.1.0) Bearing Alternate Hybrid-Diheterole Units
摘要： Lewis acid catalyzed self-condensation of hybrid diheterole (furan-pyrrole and thiophene-pyrrole) precursors afforded novel Hückel antiaromatic 24π hexaphyrin(1.0.1.0.1.0) and 32π octaphyrin(1.0.1.0.1.0.1.0) without β-annulated bridges. Single-crystal X-ray diffraction analysis of the hybrid porphyrinoids (S3N3-ox and O4N4-ox) revealed nearly planar conformation and the 1H NMR spectra suggested the presence of paratropic ring currents. These antiaromatic macrocycles showed the characteristic optical features and undergo reversible two-electron reduction to Hückel aromatic 26π- and 34π-electron species, respectively, as is evident from the spectroscopic and theoretical studies (NICS and ACID calculations). Implementation of hybrid diheteroles alternately into the expanded porphyrin skeletons would be a novel approach for fine-tuning of the electronic structures of the planar antiaromatic macrocycles.
关键词： cyclization,antiaromaticity,conformation,redox,porphyrinoids
更新于2025-09-23 15:22:29
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Detection of the conformational changes of <i>Discosoma</i> red fluorescent proteins adhered on silver nanoparticles-based nanocomposites <i>via</i> surface-enhanced Raman scattering
摘要： Description of the relationship between protein structure and function remains a primary focus in molecular biology, biochemistry, protein engineering and bioelectronics. Regardless the targeted application, the current strategies on revealing the relationship between protein structure and function lead to exposure and interaction of proteins with non-biological organic and inorganic solid surfaces. Proper description of the underlying mechanisms will certainly unveil the fundamental protein-adsorption problem and add value to the effort of record and quantification of the conformational changes of the protein native state when interacting with solid surfaces. To that end the application of physics-based diagnostic methods is suitable and highly demanded. Raman spectroscopy appears the most frequently used method for the study of biomolecule recognition, and ultra-sensitive analysis, down to a single molecule. However, to tackle the sensitivity limitations of Raman spectroscopy imposed by the small Raman cross sections, the biological systems should be coupled with metallic nanostructures. The scattering efficiency can be thus increased by several orders of magnitude due to the activation of localized surface plasmon resonance (LSPR) that induces strong enhancement of the electromagnetic (EM) field in the vicinity of the metallic surface. This enables to largely extend the application of Raman spectroscopy in molecular spectroscopy, biomolecule recognition, and ultra-sensitive analysis, down to a single molecule. Besides the sensing properties, the strong EM enhancement can be exploited to probe protein conformational changes under photoexcitation, including real-time monitoring. Therefore, since its discovery in the late 70s, the Surface-Enhanced Raman Scattering (SERS) has proven to be a very powerful and reliable analytical tool for chemo- and bio-sensing, due to the strong enhancement of the vibrational signatures of analytes in different chemical environments. In this context, a lot of resources and time have been employed in the effort to develop plasmonic substrates based on metallic nanostructures aiming at a further increase of the EM enhancement for the realization of noninvasive, highly-sensitive, and large-scale optical sensors. A large variety of metallic nanostructure morphologies and arrangements (nanosphere, nanotriangles, nanodisks, nanorods, nanocubes, etc.) and different coupling geometries (dimers, trimers, arrays, etc.) have been developed up to date for SERS platforms. However, their conversion to macroscopic plasmonic substrates relies generally on the NPs volunteer arrangement on dielectric surfaces (mainly through applying chemical methods), thus often resulting in non-uniform distribution on large areas, without a well-defined control of the spacing between the metallic nanostructures and the probed molecules, high point-to-point variability, scarce reproducibility and stability under irradiation conditions (due to photothermal and photodegradation processes). To overcome the limitations in producing solid SERS substrates various physical approaches, like thermal evaporation, combined nanoimprint lithography-shadow evaporation, gas aggregation source (GAS), pulsed laser deposition (PLD), low-energy ion beam synthesis (LE-IBS), and plasma-based deposition processes, have been proposed in the literature. It is generally acknowledged that the silver nanoparticles (AgNPs) realize the best nanoscale antenna in the visible range for amplifying local electronic and vibrational signals, thus providing unique molecular information in the optical far-field regime. Indeed, compared to gold nanoparticles, the AgNPs offer the advantage of stronger plasmonic enhancement because of lower interference between intraband and interband electronic transitions. Moreover, the use of AgNPs covers another aspect of the relationship between protein structure and function which concerns the biological activity of the AgNPs. Because of their antimicrobial properties, the AgNPs have the potential to impact human health and environment. The biological activity of AgNPs goes both ways, through the activity of ionic silver (Ag+) and through direct contact with the AgNPs resulting in protein denaturation at different cell locations; specifically sensible are those enzymes of the respiratory chain and transport channels. Therefore, there exists a recognized need to address the relationship between protein structure and function from two distinctly different vantage points: (i) quantification of the conformational changes of proteins by using the antenna effect of AgNPs and (ii) analysis of the conformational changes of proteins induced by the AgNPs extreme chemical and biological activities. The intent of this work is to bring additional insight into the mechanisms of adsorption of proteins on solid surfaces through quantification of the conformational changes of proteins adhered on AgNPs-based nanocomposites via SERS. We focus on the wild-type Discosoma recombinant red fluorescent protein (DsRed), belonging to the family of naturally fluorescent proteins (FPs). The strong interest toward the FP family originates from their application in molecular biology as reporters of gene expression, as noninvasive markers in molecular biology and other singular events of cell activity. Potential use of the FPs extends toward therapeutics, tissue regeneration, bioelectronics and protein engineering. The most widely characterized member of this family is the green fluorescent protein (GFP). The lately cloned from reef coral Discosoma sp. DsRed protein possesses the longest yet reported, for a wild-type spontaneously fluorescent protein, excitation and emission maxima at 558 nm and 583 nm, respectively. Owing to its high fluorescence yield the red fluorescent DsRed protein has become important both as a model for understanding fluorescent proteins and as a tool for biomedical research. The DsRed protein and its engineered derivatives have found broad use in cell and molecular biology including fluorescence microscopy as a marker, fluorescence correlation spectroscopy (FCS) and fluorescence activated cell sorting (FACS). Recently, the DsRed was found suitable for rational design of ultra-stable and reversible photoswitches for super-resolution imaging. Moreover, it has been hypothesized that FPs from reef-building corals operate as part of an adaptive mechanism to optically interact and to regulate the symbiotic relationship between corals and photosynthetic algae. Structural rearrangements near the chromophore influence the maturation speed and brightness of the DsRed variants. It is therefore essential to examine the conformational transitions that affect the protein’s ability to transfer optical excitation energy. Studies of the conformational changes of DsRed protein have been reported in the literature but the DsRed Raman fingerprints were investigated only by recurring to chemically synthesized model chromophores. However, the later differ from the wild-type DsRed protein for the absence of the α-helix and β-sheets that naturally surround the chromophore and for the different extensions of the conjugated π-system. The choice of chemically synthesized model chromophores is explained by the complications brought by the presence of immature green species in the solution created as a photoproduct of the red ones, thus often resulting in an unclear or incomplete band assignment. The novelty of this work lays down the point that we work with the wild-type DsRed protein in its native state and not with DsRed model chromophore. All reported experimental studies in the literature were performed in solution. No information on the DsRed protein structural and conformational changes can be found when the DsRed protein is adhered on a solid substrate and irradiated by light. The lack of information on the above discussed issues motivated this study focusing on the investigation of the interaction of wild-type DsRed proteins with AgNPs-based plasmonic substrates. Our approach involves analysis of dehydrated DsRed protein layers in link with natural conditions during drying. To perform the SERS study on the conformational changes of DsRed proteins adhered on AgNPs-based nanocomposites we have elaborated, by plasma process, highly uniform and reproducible plasmonic substrates composed of a single layer of AgNPs coated by a silica layer. Focus was made on the possibility to well control, on a large scale, the AgNPs size distribution and interparticle distances. The resulting uniformity of hot-spot distribution guarantees the reproducibility and stability of this plasmonic sensor. Subsequently, we show how the enhanced EM field in the vicinity of the AgNPs could be employed to detect the presence and identify the conformational changes of proteins, adsorbed and adhered to the plasmonic substrate, during optical irradiation. The achieved enhancement of the electromagnetic field in the vicinity of the AgNPs is as high as 105. This very strong enhancement factor allowed detecting Raman signals from discontinuous layers of DsRed issued from solution with protein concentration of only 80 nM. Three different conformations of the DsRed proteins after adhesion and dehydration on the plasmonic substrates were identified. It was found that the DsRed chromophore structure of the adsorbed proteins undergoes optically assisted chemical transformations when interacting with the optical beam, which leads to reversible transitions between the three different conformations. The proposed time-evolution scenario endorses the dynamical character of the relationship between protein structure and function. It also confirms that the conformational changes of proteins with strong internal coherence, like DsRed proteins, are reversible.
关键词： plasmonic substrate,protein conformation,surface-enhanced Raman scattering,plasma deposition process,Discosoma red-fluorescent protein DsRed,Silver nanoparticles
更新于2025-09-23 15:22:29
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Triplet acceptors with Da??A structure and twisted conformation for efficient organic solar cells
摘要： Triplet acceptors have been developed to construct high performance organic solar cells (OSCs) since the long lifetime and diffusion range of triplet excitons may dissociate into free charges instead of net recombination when the energy levels of triplet states (T1) are close to those of charge transfer states (3CT). The current triplet acceptors were designed by introducing heavy atoms to enhance the intersystem crossing, limiting their applications. Herein, two twisted acceptors without heavy atoms, analogues of Y6, were constructed with large π-conjugated core and D-A structure, proved to be triplet materials, leading to a high performance OSCs. The mechanism of triplet excitons were investigated to show that the twisted and D-A structures result in large spin orbital coupling (SOC) and small energy gap between the singlet and triplet states, and thus efficient intersystem crossing. Moreover, the energy level of T1 is close to 3CT, facilitating the split of triplet exciton to free charges. This contribution provided new insights in working mechanism of triplet excitons in OSCs.
关键词： twisted conformation,D-A structure,long lifetime exciton,triplet acceptor,organic solar cells
更新于2025-09-23 15:21:01
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Vibrational Properties of Thiolate-Protected Gold Nanoclusters
摘要： Over recent years, the field of thiolate-protected gold nanoclusters has made remarkable progress. The successful determination of the structure of some of these clusters by X-ray crystallography was a milestone in this field. X-ray crystallography is arguably the most important technique in the field up to now, and it enabled the study of structure evolution as a function of cluster size. It also shed light on the structure of the Au?S interface. Recently, it has been realized that thiolate-protected gold clusters are very dynamic systems. Metal atoms and ligands can exchange easily between clusters. Furthermore, the adsorbed ligands bear conformational dynamics. Such dynamic effects call for experimental methods that can cope with it. Future efforts in this field will be directed toward applications of thiolate-protected clusters, and many of them will rely on dissolved clusters. Therefore, structure determination in solution is an important issue, though it is very challenging. The structure of the metal core and the Au?S interface is not expected to change in solution with respect to the crystal. However, the structure of the adsorbed ligand itself is sensitive to the environment and may be different in the solid state and in solution, as has been shown in fact in the past. It is this (dynamic) structure of the ligand that determines the interaction between the cluster and its environment, which is crucial, for example, for sensing applications. Vibrational spectroscopy is a promising technique to characterize thiolate-protected clusters in different environments. A vibrational spectrum is sensitive to structure (conformation) although this information is often 'hidden' in the spectrum, requiring detailed analysis and support from theory to be deciphered. Compared to other techniques like UV?vis spectroscopy and mass spectrometry, vibrational spectroscopy was not extensively used in the field of thiolate-protected clusters, but we believe that the technique will be very valuable for the future developments in the field.
关键词： vibrational spectroscopy,ligand conformation,thiolate-protected gold nanoclusters,Au?S interface,chirality transfer
更新于2025-09-23 15:21:01
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A versatile fluorometric in-situ hybridization method for the quantitation of hairpin conformations in DNA self-assembled monolayers
摘要： As the performance of hairpin DNA (hpDNA)-based biosensors is highly dependent on the yield of stem-loop (hairpin) conformations, we report herein a versatile fluorometric in-situ hybridization protocol for examining hpDNA self-assembled monolayers (SAMs) on popularly used biochip substrates. Specifically, the ratio of fluorescence (FL) intensities of hpDNA SAMs (in an array format) before and after hybridization was adapted as the key parameter for performing such a determination. Upon confirming the existence of mixed and tunable DNA conformations in binary deposition solutions and the efficient hybridization of the hairpin strands with target DNA via gel electrophoresis assays, we have tested the fluorometric protocol for determining the coverages of hpDNA in hpDNA/ssDNA SAMs prepared on gold; its accuracy was validated by Exonuclease I (Exo I)-assisted electrochemical quantitation. To further confirm its versatility, this FL protocol was adapted for quantifying hairpin conformations formed on glass and polycarbonate (PC) substrates. The molar ratios of surface-tethered hairpin conformations on the three different substrates were all found to be proportional to but less than that in the binary deposition solutions, and dependent on the substrate morphology. The findings reported herein are beneficial to the construction of highly efficient DNA hairpin-based sensing surfaces, which essentially facilitates the creation of hpDNA-based biosensors with optimal detection performance.
关键词： In-situ hybridization,conformation evaluation,DNA biosensor/biochip,fluorescence microarray,Hairpin DNA
更新于2025-09-23 15:19:57
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Determination of the Chronological Order of a Laser Printing and Gel Pen Writing Without any Crossing Strokes
摘要： Laser printers and writing instruments are being exploited by the forgers to produce fabricated documents. They often produce such documents by appending genuine signature on a blank sheet and later printing on it. Often these fabricated documents do not contain intersection of strokes and may pose a difficulty to forensic document examiners in analyzing cases related to such documents. Keeping in mind the limited research work done on nonintersecting strokes, the present study has been conducted with an aim to determine the sequence of nonintersecting strokes of gel pens and laser printers. Three hundred samples of nonintersecting strokes of gel pen ink and laser printing were prepared. Of these 300, 150 had laser-printed text below the gel pen strokes and the remaining 150 were prepared with gel pen stokes below the laser-printed text. The samples have been analyzed using Nikon SMZ 800N stereomicroscope. Three micro-conformation features, that is, pattern of toner distribution, ink distribution, and fiber distribution have been observed in the samples. The results demonstrate the successful establishment of sequence of nonintersecting strokes in case of gel pen and laser-printed documents by the determination of micro-conformation features.
关键词： nonintersecting strokes,laser printer,questioned document examination,sequence of nonintersecting strokes,stereomicroscope,gel pen,micro-conformation features
更新于2025-09-23 15:19:57
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Crystal Multi-Conformational Control Through Deformable Carbon-Sulfur Bond for Singlet-Triplet Emissive Tuning
摘要： Crystal-state luminophores have been of great interest in optoelectronics for years, whereas the excited state regulation at the crystal level is still restricted by the lack of control ways. We report that the singlet–triplet emissive property can be profoundly regulated by crystal conformational distortions. Employing fluoro-substituted tetrakis(arylthio)benzene luminophores as prototype, we found that couples of molecular conformations formed during different crystallizations. The deformable carbon–sulphur bond essentially drove the distortion of the molecular conformation and varied the stacking mode, together with diverse non-covalent interactions, leading to the proportional adjustment of the fluorescence and phosphorescence bands. This intrinsic strategy was further applied for solid-state multicolor emission and mechanoluminescence, probably offering new insights for design of smart crystal luminescent materials.
关键词： Luminescence,Crystal engineering,Noncovalent interactions,Molecular Stacking,Single-crystal conformation
更新于2025-09-19 17:15:36
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Optoelectronic properties and aggregation effects on the performance of planar versus contorted pyrene-cored perylenediimide dimers for organic solar cells
摘要： In this work, we present a new strategy to develop small molecules based on perylenediimde (PDI) with fused and contorted conjugated backbones as electron acceptors for fullerene-free organic solar cells. The two new electron acceptors, 27-Py-PDI and 49-Py-PDI, containing binary PDI units fused with pyrene at different positions were structurally isomers, which were investigated systematically. Theoretical calculations indicated that the two positional isomers exhibit distinct molecular geometries (planar for 27-Py-PDI vs contorted for 49-Py-PDI), which lead to huge differences on their synthetic methods, aggregation effects and their optoelectronic properties. The effects of structural isomerism on the molecular geometry, optical spectra, energy levels, charge carrier mobility and the morphology discrepancies as well as the corresponding photovoltaic performance were fully investigated. Temperature-dependent 1H NMR and the film UV-vis spectroscopy were used to study the molecular aggregation behaviors. Calculations of nuclear independent chemical shifts (NICS) indicate significant difference of the aromaticity between the isomers. Blended with donor materials of PTB7-Th to fabricate the inverted solar cells, an encouraging PCE of 4.53% along with an impressive open-circuit voltage (VOC) of 1.0 V (higher than the other acceptors based on PDIs and the PC71BM) were achieved by using 49-Py-PDI, which were superior to those of its isomer 27-Py-PDI (2.51%). The work suggests that introducing rigid and contorted features into fully fused acceptors based on PDI motifs can enhance the interface energy gap (?EDA), extend the π-delocalization and decrease the conformational disorder resulting into improved VOC without sacrificing JSC in OPV devices. This design strategy by introducing rigid and steric hindrance to increase intermolecular strain to construct fully ring fused contorted acceptors is an effective approach for the development of novel NFAs.
关键词： fused perylenediimides,pyrene core,non-fullerene acceptors,contorted conformation
更新于2025-09-19 17:13:59
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Gr/TiO2 films with light controlled positive/negative charge for cell harvesting application
摘要： Light-induced cell harvest shows much potential in in vitro cell culture. In this work, a light-responsive monolayer graphene (Gr)/titanium dioxide nanodots (TN) film is designed and used for light induced cell harvest. It is found that after 20 min of 365 nm UV or 450 nm visible light illumination, different types of cells could be detached from the surface effectively. The highest cells detachment ratio reaches about 95%. The mechanism of such cell detachment is contributed to that light illumination generates charges accumulation, which, in turn, changes the conformation of extracellular matrix protein molecules adsorbed to a more disordered state, and eventually leads to the cells detachment. Such UV and visible light responsive Gr/TiO2 film could be a good candidate for surface with light-induced cell detachment property.
关键词： protein conformation,cell harvest,light illumination,surface charges,graphene/TiO2 nanodots
更新于2025-09-16 10:30:52