Prolonged Excited-State Lifetime of Porphyrin Due to the Addition of Colloidal SiO₂ to Triton X-100 Micelles

A water-insoluble porphyrin derivative was studied in Triton X-100 micelles by steady-state spectroscopy and picosecond photolysis. The porphyrin in micelles formed J aggregates, and, consequently, the excited-state lifetime of such a porphyrin was very short. After the addition of colloidal SiO2, the B-band absorption blue-shifted, forming a broad absorption peak. This peak can be ascribed to the monomer-dominated absorption of porphyrin. The photolysis experiment showed that the dynamic curve of the porphyrin with SiO2 exhibited a rapid recovery plus an offset resulting from the S1 state absorption. The long lifetime part constituted about half of the total absorption. Such a long-lifetime component could be ascribed to the absorption of monomeric porphyrin. The fluorescence near-field scanning optical microscopy showed that the porphyrin in the presence of SiO2 exhibited stronger fluorescence images compared with that in the absence of SiO2, though the topography images of the these samples were similar. The monomeric dispersion of porphyrin in SiO2 solution may be due to its inset in the fragmented bilayers on the surface of the SiO2 particles, assisted by the hydrogen bond between the amino group and the ionized silanol of SiO2. The prolonged excited lifetime can be greatly beneficial to the application of porphyrin in heterogeneous photosensitization or photocatalysis

Photoamidation of <i>N</i>-Acetyl-2-chlorotyrosine Methyl Ester and 3-Chlorophenol^†

Photoamidation of N-Acetyl-2-chlorotyrosine Methyl Ester and 3-Chlorophenol†</sup

Effect of Chelation to Lanthanum Ions on the Photodynamic Properties of Hypocrellin A

Hypocrellin A (HA), an efficient phototherapeutic agent, can chelate with lanthanum ion to form a 1:1 complex, which exhibits enhanced 1O2 generation quantum yield, a red-shifted absorption window, greatly improved water solubility, a much lengthened triplet excited state lifetime, and an increased affinity to DNA with respect to HA. These effects in turn lead to a more potent photodamage ability on calf thymus DNA for La3+−HA than HA in both aerobic and anaerobic conditions, indicating the potential application of La3+−HA in the field of photodynamic therapy (PDT)

Photoluminescence Quenching in Recyclable Water-Soluble Zn-Based Metal–Organic Framework Nanoflakes for Dichromate Sensing

Nanoflakes are materials with high dispersion, a large specific surface area, and a high number of active sites that can provide a good platform for various fluorescence sensors and are very popular among researchers. In this study, a nanoflake-like zinc metal–organic framework (Zn-MOF) was successfully synthesized from the organic ligand 1,2,4,5-tetra­(1H-imidazol-1-yl)­benzene and zinc nitrate. The synthesized Zn-MOF nanoflakes are extremely soluble in water and exhibit high fluorescence stability. Since Cr2O72– can significantly quench the fluorescence of Zn-MOF aqueous solution, a rapid detection method for Cr2O72– content in water was constructed with a linear range and linear correlation of 0.3–20 μM and 0.992, respectively. The fluorescence quenching constant of the Zn-MOF is KSV = 2.003 × 104 M–1, and the detection limit for Cr2O72– is as low as 0.09 μM. Through the study of fluorescence lifetime and UV absorption, it is proven that the mechanism of Cr2O72– quenching the fluorescence of the Zn-MOF is the inner filter effect. In addition, even after being applied five times, the Zn-MOF still maintained good detection performance for Cr2O72–. The proposed method was successfully applied to the determination of real water samples, confirming that it can be used as an alternative method for the detection of Cr2O72– in environmental samples

Presentation_1_The BR signaling pathway regulates primary root development and drought stress response by suppressing the expression of PLT1 and PLT2 in Arabidopsis thaliana.pptx

IntroductionWith the warming global climate, drought stress has become an important abiotic stress factor limiting plant growth and crop yield. As the most rapidly drought-sensing organs of plants, roots undergo a series of changes to enhance their ability to absorb water, but the molecular mechanism is unclear.Results and methodsIn this study, we found that PLT1 and PLT2, two important transcription factors of root development in Arabidopsis thaliana, are involved in the plant response to drought and are inhibited by BR signaling. PLT1- and PLT2-overexpressing plants showed greater drought tolerance than wild-type plants. Furthermore, we found that BZR1 could bind to the promoter of PLT1 and inhibit its transcriptional activity in vitro and in vivo. PLT1 and PLT2 were regulated by BR signaling in root development and PLT2 could partially rescue the drought sensitivity of bes1-D. In addition, RNA-seq data analysis showed that BR-regulated root genes and PLT1/2 target genes were also regulated by drought; for example, CIPK3, RCI2A, PCaP1, PIP1;5, ERF61 were downregulated by drought and PLT1/2 but upregulated by BR treatment; AAP4, WRKY60, and AT5G19970 were downregulated by PLT1/2 but upregulated by drought and BR treatment; and RGL2 was upregulated by drought and PLT1/2 but downregulated by BR treatment.DiscussionOur findings not only reveal the mechanism by which BR signaling coordinates root growth and drought tolerance by suppressing the expression of PLT1 and PLT2 but also elucidates the relationship between drought and root development. The current study thus provides an important theoretical basis for the improvement of crop yield under drought conditions.</p

Self-Assembled Spiral Nanoarchitecture and Supramolecular Chirality in Langmuir−Blodgett Films of an Achiral Amphiphilic Barbituric Acid

An amphiphilic barbituric acid derivative was found to form stable monolayers showing a clear phase transition at the air/water interface. It is interesting to find that the deposited Langmuir−Blodgett (LB) films of the compound showed circular dichroism (CD) although the molecule itself was achiral. AFM measurements on the transferred one-layer LB film revealed that spiral nanoarchitectures were formed. It was further found that the supramolecular chirality of the LB films was related to symmetry breaking at the interface. Hydrogen bonding and the π−π stacking between the neighboring molecules resulted in chiral fibers which formed the spiral structures. To the best of our knowledge, this is the first report on the chirality of the molecular assemblies and spiral nanostructures formed through the air/water interface by achiral molecules

Table_1_The BR signaling pathway regulates primary root development and drought stress response by suppressing the expression of PLT1 and PLT2 in Arabidopsis thaliana.xlsx

IntroductionWith the warming global climate, drought stress has become an important abiotic stress factor limiting plant growth and crop yield. As the most rapidly drought-sensing organs of plants, roots undergo a series of changes to enhance their ability to absorb water, but the molecular mechanism is unclear.Results and methodsIn this study, we found that PLT1 and PLT2, two important transcription factors of root development in Arabidopsis thaliana, are involved in the plant response to drought and are inhibited by BR signaling. PLT1- and PLT2-overexpressing plants showed greater drought tolerance than wild-type plants. Furthermore, we found that BZR1 could bind to the promoter of PLT1 and inhibit its transcriptional activity in vitro and in vivo. PLT1 and PLT2 were regulated by BR signaling in root development and PLT2 could partially rescue the drought sensitivity of bes1-D. In addition, RNA-seq data analysis showed that BR-regulated root genes and PLT1/2 target genes were also regulated by drought; for example, CIPK3, RCI2A, PCaP1, PIP1;5, ERF61 were downregulated by drought and PLT1/2 but upregulated by BR treatment; AAP4, WRKY60, and AT5G19970 were downregulated by PLT1/2 but upregulated by drought and BR treatment; and RGL2 was upregulated by drought and PLT1/2 but downregulated by BR treatment.DiscussionOur findings not only reveal the mechanism by which BR signaling coordinates root growth and drought tolerance by suppressing the expression of PLT1 and PLT2 but also elucidates the relationship between drought and root development. The current study thus provides an important theoretical basis for the improvement of crop yield under drought conditions.</p

ESR Signal of Superoxide Radical Anion Adsorbed on TiO₂ Generated at Room Temperature

The electron spin resonance spectrum of superoxide anion radical adsorbed on the surface of colloidal TiO2 was detected directly at room temperature for the first time. This signal was generated partially by porphyrin-sensitized titanium dioxide, i.e., the reduction of adsorbed oxygen on the TiO2 nanocluster surface by the just injected electron from the excited porphyrin

Photodynamic Properties of a Bispyrrolecarboxamide-Modified Hypocrellin B: The Role of Affinity and Ascorbic Acid

The photodynamic properties of a new hypocrellin B (HB) derivative bearing a bispyrrolecarboxamide pendant (HB-Net) were investigated in detail. EPR experiments revealed that the generation ability of reactive oxygen species (ROS) of HB-Net is inferior to that of HB. DNA melting temperature measurements and ethidium bromide (EB) displacement assay illustrated the affinity of HB-Net toward dsDNA as the result of the bispyrrolecarboxamide unit, which is structurally related to the well-known minor groove binder netropsin. The radical generation abilities of HB and HB-Net can be enhanced by ascorbic acid via the photoinduced electron transfer from ascorbic acid to the photosensitizer, however, only the DNA photodamage capability of HB-Net can be improved significantly by ascorbic acid due to the stronger affinity of HB-Net to DNA. Consequently, the combination of HB-Net and ascorbic acid may lead to efficient DNA photodamage even in anaerobic conditions

Photodynamic Properties of Hypocrellin A, Complexes with Rare Earth Trivalent Ions: Role of the Excited State Energies of the Metal Ions

Fifteen complexes of hypocrellin A (HA) with rare earth trivalent ions (except Pm3+) along with the complex of HA with Sc3+ were prepared, and their photodynamic activities, including absorption in the phototherapeutic window (600−900 nm); water-solubility; triplet lifetime; generation of reactive oxygen species (ROS), such as singlet oxygen (1O2), superoxide anion radical (O2-•), and hydroxyl radical (OH•); generation of semiquinone anion radical; and affinity to DNA, as well as photosensitized damage on calf thymus DNA (CT DNA), were compared in detail using the UV−visible spectrum, fluorescence spectrum, spin-trapping EPR technique, and laser photolysis technique. All complexes exhibit a red-shifted absorption spectrum, an increased absorbance above 600 nm, improved water solubility, and an enhanced affinity to CT DNA over the parent HA. For ions that possess low-energy excited states, including Ce3+, Pr3+, Nd3+, Sm3+, Eu3+, Tb3+, Dy3+, Ho3+, Er3+, Tm3+, and Yb3+, the corresponding complexes show undetectable or nearly undetectable fluorescence, a triplet excited-state lifetime, generation of ROS, and photodamage in CT DNA. In contrast, for ions that do not possess low-energy excited states, including Sc3+, Y3+, La3+, Gd3+, and Lu3+, the corresponding complexes exhibit higher photodamage abilities with CT DNA with respect to HA, benefitting from both their comparable or even higher 1O2 quantum yields and an electrostatic affinity that is higher for DNA than HA