The aim of this study was to assess the efficacy human mesenchymal stem cells (

Phytochrome photoreceptors control plant growth, development, and the shade avoidance response that limits crop yield in high-density agricultural plantings. Cyanobacteriochromes (CBCRs) are distantly related photosensory proteins that control cyanobacterial metabolism and behavior in response to light. Photoreceptors in both families reversibly photoconvert between two photostates via photoisomerization of linear tetrapyrrole (bilin) chromophores. Spectroscopic and biochemical studies have demonstrated heterogeneity in both photostates, but the structural basis for such heterogeneity remains unclear. We report solution NMR structures for both photostates of the red/green CBCR NpR6012g4 from In addition to identifying structural changes accompanying photoconversion, these structures reveal structural heterogeneity for residues Trp655 and Asp657 in the red-absorbing NpR6012g4 dark state, yielding two distinct environments for the phycocyanobilin chromophore. We use site-directed mutagenesis and fluorescence and absorbance spectroscopy to assign an orange-absorbing population in the NpR6012g4 dark state to the minority configuration for Asp657. This population does not undergo full, productive photoconversion, as shown by time-resolved spectroscopy and absorption spectroscopy at cryogenic temperature. Our studies thus elucidate the spectral and photochemical consequencesof structural heterogeneity in a member of the phytochrome superfamily, insights that should inform efforts to improve photochemical or fluorescence quantum yields in the phytochrome superfamily.

Recent characterization of the red/green cyanobacteriochrome (CBCR) NpR6012g4 revealed a high quantum yield for its forward photoreaction [J. Am. Chem. Soc. 2012, 134, 130-133] that was ascribed to the activity of hidden, productive ground-state intermediates. The dynamics of the pathways involving these ground-state intermediates was resolved with femtosecond dispersed pump-dump-probe spectroscopy, the first such study reported for any CBCR. To address the ubiquity of such second-chance initiation dynamics (SCID) in CBCRs, we examined the closely related red/green CBCR NpF2164g6 from Nostoc punctiforme. Both NpF2164g6 and NpR6012g4 use phycocyanobilin as the chromophore precursor and exhibit similar excited-state dynamics. However, NpF2164g6 exhibits a lower quantum yield of 32% for the generation of the isomerized Lumi-R primary photoproduct, compared to 40% for NpR6012g4. This difference arises from significantly different ground-state dynamics between the two proteins, with the SCID mechanism deactivated in NpF2164g6. We present an integrated inhomogeneous target model that self-consistently fits the pump-probe and pump-dump-probe signals for both forward and reverse photoreactions in both proteins. This work demonstrates that reactive ground-state intermediates are not ubiquitous phenomena in CBCRs.

Phytochromes are red/far-red photosensory proteins that detect the ratio of red to far-red light. Crucial to light regulation of plant developmental biology, phytochromes are also found in fungi, bacteria, and eukaryotic algae. In addition to phytochromes, cyanobacteria also can contain distantly related cyanobacteriochromes (CBCRs) that, like phytochromes, utilize the photoisomerization of a linear tetrapyrrole (bilin) chromophore to convert between two photostates with distinct spectral properties. CBCRs exhibit a wide range of photostates spanning the visible and even near-ultraviolet spectrum. In both phytochromes and CBCRs, biosynthesis initially yields a holoprotein with bilin in the 15Z configuration, and the 15E photoproduct can often revert to the 15Z photostate in the absence of light (dark reversion). One CBCR subfamily, red/green CBCRs, typically exhibits red-absorbing dark states and green-absorbing photoproducts. Dark reversion is extremely variable in red/green CBCRs with known examples ranging from seconds to days. One red/green CBCR, NpR6012g4 from Nostoc punctiforme, is also known to exhibit forward photoconversion that has an unusually high quantum yield at ∼40% compared to 10-20% for phytochromes and CBCRs from other subfamilies. In the current study, we use time-resolved pump-probe absorption spectroscopy with broadband detection and multicomponent global analysis to characterize forward photoconversion of seven additional red/green CBCRs from N. punctiforme on an ultrafast time scale. Our results reveal that red/green CBCRs exhibit a conserved pathway for primary forward photoconversion but that considerable diversity exists in their excited-state lifetimes, photochemical quantum yields, and primary photoproduct stabilities.

Efficient nanotextured black silicon solar cells passivated by an Al2O3 layer are demonstrated. The broadband antireflection of the nanotextured black silicon solar cells was provided by fabricating vertically aligned silicon nanowire (SiNW) arrays on the n(+) emitter. A highly conformal Al2O3 layer was deposited upon the SiNW arrays by the thermal atomic layer deposition (ALD) based on the multiple pulses scheme. The nanotextured black silicon wafer covered with the Al2O3 layer exhibited a low total reflectance of ∼1.5% in a broad spectrum from 400 to 800 nm. The Al2O3 passivation layer also contributes to the suppressed surface recombination, which was explored in terms of the chemical and field-effect passivation effects. An 8% increment of short-circuit current density and 10.3% enhancement of efficiency were achieved due to the ALD Al2O3 surface passivation and forming gas annealing. A high efficiency up to 18.2% was realized in the ALD Al2O3-passivated nanotextured black silicon solar cells.

The accumulation of extracellular β-amyloid (Aβ) plaques within the brain is unique to Alzheimer’s disease (AD) and thought to induce synaptic deficits and neuronal loss. Optimal therapies should tackle the core AD pathophysiology and prevent the decline in memory and cognitive functions. This study aimed to evaluate the therapeutic performance of mesenchymal stem cell-derived exosomes (MSC-exosomes), which are secreted membranous elements encapsulating a variety of MSC factors, on AD. A human neural cell culture model with familial AD (FAD) mutations was established and co-cultured with purified MSC-exosomes. 2-[18F]Fluoro-2-deoxy-d-glucose ([18F]FDG) and novel object recognition (NOR) testing were performed before/after treatment to evaluate the therapeutic effect in vivo. The AD-related pathology and the expression of neuronal memory/synaptic plasticity-related genes were also evaluated. The results showed that MSC-exosomes reduced Aβ expression and restored the expression of neuronal memory/synaptic plasticity-related genes in the cell model. [18F]FDG-PET imaging and cognitive assessment revealed a significant improvement in brain glucose metabolism and cognitive function in AD transgenic mice. The phase of neurons and astrocytes in the brain of AD mice were also found to be regulated after treatment with MSC-exosomes. Our study demonstrates the therapeutic mechanism of MSC-exosomes and provides an alternative therapeutic strategy based on cell-free MSC-exosomes for the treatment of AD.

Series of dyes containing a cyanovinyl entity in the spacer have been developed and characterized. Dye-sensitized solar cells (DSSCs) using the dyes as the sensitizers exhibited good efficiencies ranging from 3.48−4.92%, which reached 45−70% with respect to that of an N719-based device fabricated under similar conditions. In general, better DSSC performances are observed with molecules having a shorter distance between the internal cyanovinyl entity and the amine donor. Computational analysis indicated that the cyanovinyl entity may behave as a charge trap, especially in the long molecules studied, where the cyanovinyl group is away from the electron-donating amine by two or more aromatic groups. A positive correlation is observed between the theoretically calculated product of oscillator strengths and the charge shift at the cyanoacrylic acid group and the measured short-circuit current in DSSCs. Therefore, it is likely that the charge-trapping in the cyanovinyl entity reduces the electronic interaction between the dye and the attached TiO2 and, therefore, compromises the DSSC performance.

Femtosecond photodynamics of the reverse (15EPfr→15ZPr) reaction of the red/far-red phytochrome Cph1 from Synechocystis were resolved with visible broadband transient absorption spectroscopy. Multi-phasic dynamics were resolved and separated via global target analysis into a fast-decaying (260 fs) excited-state population that bifurcates to generate the isomerized Lumi-F primary photoproduct and a non-isomerizing vibrationally excited ground state that relaxes back into the 15EPfr ground state on a 2.8-ps time scale. Relaxation on a 1-ms timescale results in the loss of red absorbing region, but not blue region, of Lumi-F, which indicates that formation of 15ZPr occurs on slower timescales.