Bleaching Rate Research Articles

Analysis tools for single-monomer measurements of self-assembly processes

Protein assembly plays an important role throughout all phyla of life, both physiologically and pathologically. In particular, aggregation and polymerization of proteins are key-strategies that regulate cellular function. In recent years, methods to experimentally study the assembly process on a single-molecule level have been developed. This progress concomitantly has triggered the question of how to analyze this type of single-filament data adequately and what experimental conditions are necessary to allow a meaningful interpretation of the analysis. Here, we developed two analysis methods for single-filament data: the visitation analysis and the average-rate analysis. We benchmarked and compared both approaches with the classic dwell-time-analysis frequently used to study microscopic association and dissociation rates. In particular, we tested the limitations of each analysis method along the lines of the signal-to-noise ratio, the sampling rate, and the labeling efficiency and bleaching rate of the fluorescent dyes used in single-molecule fluorescence experiments. Finally, we applied our newly developed methods to study the monomer assembly of actin at the single-molecule-level in the presence of the class II nucleator Cappuccino and the WH2 repeats of Spire. For Cappuccino, our data indicated fast elongation circumventing a nucleation phase whereas, for Spire, we found that the four WH2 motifs are not sufficient to promote de novo nucleation of actin.

Photoinduced bleaching in an efficient singlet oxygen photosensitizing protein: Identifying a culprit in the flavin-binding LOV-based protein SOPP3

Light-oxygen-voltage (LOV) proteins that bind flavin mononucleotide (FMN) have received attention as optogenetic systems that can photosensitize the production of singlet molecular oxygen, O2(a1Δg). Although the seminal compound in this family, mini singlet oxygen generator (miniSOG), does not make O2(a1Δg) in appreciable yield, it is a convenient standard against which other singlet oxygen photosensitizing proteins (SOPPs) can be judged. SOPP3 is a re-engineered version of miniSOG that selectively produces O2(a1Δg) in high yield but, when localized in a cell, the protein-encased FMN readily bleaches upon irradiation. In contrast, the bleaching of FMN in miniSOG is slow under the same conditions. The available evidence indicates that O2(a1Δg) is not directly involved in the bleaching reaction. Rather, electron-transfer reactions between FMN and molecules in the surrounding medium, likely mediated by residues in the LOV protein, accelerate FMN bleaching. In this regard, and identifying a culprit, replacing a glutamine that H-bonds to FMN in miniSOG with either leucine (Q103L) or valine (Q103V) increases the 3FMN lifetime and, thereby, increases both the O2(a1Δg) yield and the bleaching rate. Although the same electron transfer reactions likely influence these respective observations, the O2(a1Δg) yield principally reflects the kinetic competition between two processes that remove/deactivate 3FMN: (1) quenching by ground state oxygen, O2(X3Σg-), to produce O2(a1Δg), and (2) electron transfer to produce the FMN radical anion. Photobleaching principally reflects the accumulated electron-transfer-mediated depletion of ground state FMN, which, over time in the dark, is partly regenerated by compensating redox reactions. Despite the bleaching, irradiation of SOPP3 induces morphological change in a cell. This result, which contradicts conclusions from previous experiments with a lower light dose, indicates that SOPP3 may indeed be a viable optogenetic actuator.

Characterizing photostability of red fluorescent proteins under multiphoton excitation

Red fluorescent proteins (RFPs) and biosensors built upon them provide an attractive advantage for two-photon laser microscopy (2PLM) because they can report from deeper layers of tissue compared to green fluorescent proteins. The two-photon excitation spectra of RFPs consist of two different transitions, a weak one, at 1000-1200 nm (S0->S1), and a strong one, at 740-800 nm (S0->Sn). Therefore, using 740-800 nm excitation looks more efficient. Here we study the multiphoton bleaching rate of RFP mCherry in these two spectral regions.

Simultaneously Achieving Highly Efficient and Stable Polymer:Non-Fullerene Solar Cells Enabled By Molecular Structure Optimization and Surface Passivation.

Despite the tremendous efforts in developing non‐fullerene acceptor (NFA) for polymer solar cells (PSCs), only few researches are done on studying the NFA molecular structure dependent stability of PSCs, and long‐term stable PSCs are only reported for the cells with low efficiency. Herein, the authors compare the stability of inverted PM6:NFA solar cells using ITIC, IT‐4F, Y6, and N3 as the NFA, and a decay rate order of IT‐4F > Y6 ≈ N3 > ITIC is measured. Quantum chemical calculations reveal that fluorine substitution weakens the C═C bond and enhances the interaction between NFA and ZnO, whereas the β‐alkyl chains on the thiophene unit next to the C═C linker blocks the attacking of hydroxyl radicals onto the C═C bonds. Knowing this, the authors choose a bulky alkyl side chain containing molecule (named L8‐BO) as the acceptor, which shows slower photo bleaching and performance decay rates. A combination of ZnO surface passivation with phenylethanethiol (PET) yields a high efficiency of 17% and an estimated long T 80 and Ts80 of 5140 and 6170 h, respectively. The results indicate functionalization of the β‐position of the thiophene unit is an effective way to improve device stability of the NFA.

Coastal corals during heat stress and eutrophication: A case study in Northwest Hainan coastal areas

This study initially investigated the coral status during the unexpected bleaching event in three coastal areas in Northwest Hainan coastal areas and analyzed changes in coral holobionts of the healthy and bleached Galaxea fascicularis. Coral coverage had declined severely, and the bleaching rate was extremely high during heat stress. The bleached corals had lower maximum photosynthetic yield, actual photosynthetic yield, zooxanthellae density, and chlorophyll a content than the healthy G. fascicularis, but there was no significant difference in protein, carbohydrate and lipid in eutrophic waters. The diversity and community composition of Symbiodiniaceae and symbiotic bacteria between healthy and bleached G. fascicularis showed no difference. Function prediction of the symbiotic bacteria revealed that the metabolism process was the main pathway of annotation. Present findings suggested that energy reserve functioning and high stability of the holobiont structure and might provide opportunities to G. fascicularis to adapt to eutrophication and heat stress.

Designing a hybrid type photoelectrochromic device with dual coloring modes for realizing ultrafast response/high optical contrast self-powered smart windows

The self-powered smart window is a promising wire-free system to integrate on the energy-saving building due to its independent and sustainable operations without an external power source. Solar-driven photoelectrochromic devices (PECDs), which derived from the hybridization of dye-sensitized solar cells (DSSCs) and electrochromic devices (ECDs), are potential systems to realize the convenient self-powered smart window. To further boosting up the optical contrast and minimizing the response time, in this study, a brand new hybrid type photoelectrochromic device (H-PECD) composed with a new architecture of independently covered photoelectrode with electrochromic conducting polymeric layer and a novel counter electrode (CE) with bifunctional electrochemical layer is proposed in the first time. Compared to traditional combined-type PECDs (C-PECD), the electrochromic and the photoactive layers are independently integrated on the photoelectrode to overcome the limitation of electrochromic material selection. By taking this advantage, a conducting polymer of PEDOT-MeOH with high coloration efficiency can be introduced to serve as the electrochromic layer for further enhancing the optical performance of H-PECD. Furthermore, a highly transparent electrochemical layer serves as bifunctional CE for not only facilitating the I3- reduction reaction for accelerating the bleaching rate, but also contributes additional optical contrast of 3% under coloring process. By comparing with another classic configuration of separated type PECD (S-PECD), the coloring and bleaching time of H-PECD can be shortened within 5 s under maximum transmittance change at 600 nm for 31.7% since the photovoltaic performance and photo-coloration efficiency (PhCE) is improved by integrating with bifunctional CE. By taking advantage of H-PECD, duel-coloring modes of high optical contrast and ultrafast response can be achieved by controlling the operating processes. This research is a substantial advancement toward the practical application of PECDs and self-powered smart windows.

Construction of pillar[5]arene-based photochromic supramolecular polymeric system with tunable thermal bleaching rate

Naphthopyran is targeted as the photochromic material here due to its fast photo-sensitivity, high optical density, relative chemical structural simplicity, and its colorless degradation products are also important in commercial ophthalmic applications as variable transmission lenses. In this paper, we reported the synthesis and characterization of a new class of photochromic supramolecular system containing both pillar[5]arene subunit and naphthopyran moiety in the chemical structural backbone. Owing to the supramolecular host-guest interactions of pillar[5]arene/neutral nitrile molecular recognition motif, the designed molecules could be spontaneously self-assembled. Thus, the photochromic supramolecular system indicates an efficient photochromism with convenient tunable fading rate, providing a simple and versatile strategy to fabricate photochromic supramolecular system, as well as potential applications in advanced photo-responsive materials.

Coupling high-resolution coral bleaching modeling with management practices to identify areas for conservation in a warming climate: Keramashoto National Park (Okinawa Prefecture, Japan)

Increases in sea-surface temperature due to global warming are a major threat to tropical and subtropical corals as exposure to high water temperatures is the primary cause of coral bleaching. To continue receiving high ecosystem services from coral reef ecosystems in the future, it is important to predict the growth conditions of corals and take appropriate countermeasures to protect them at both global and local scales. The Kerama Islands (part of the Nansei Islands, Japan) were selected as the study area. The islands have been designated as a national park and attract substantial tourism, which utilizes the coral reef ecosystem. The selected study site is significant as it is known to act as a source of coral larvae for the surrounding area. In this study, coral bleaching and mortality rates under present and +1.5 °C/+2.0 °C water temperature conditions were estimated using a 1) three-dimensional hydrodynamic model with a spatial resolution of 100 m and 2) statistical model describing the relationship between various environmental parameters and coral bleaching and mortality rates. Applying a local hydrodynamic model enabled us to obtain high-resolution spatial and temporal variations in water temperature and current speed, and these data were used to obtain statistical model data. Coral conservation sites were prioritized based on 1) projections of the spatial distribution of bleaching and mortality rates under global warming conditions and 2) locations of the main diving and conservation points, with the intention of continuing the present use and management locations. The results of this study are expected to contribute to the management of coral reef ecosystems through conservation and adaptation strategies at local scales.

Stable Transfection of the Singlet Oxygen Photosensitizing Protein SOPP3: Examining Aspects of Intracellular Behavior†

Protein-encased chromophores that photosensitize the production of reactive oxygen species, ROS, have been the center of recent activity in studies of oxidative stress. One potential attribute of such systems is that the local environment surrounding the chromophore, and that determines the chromophore's photophysics, ideally remains constant and independent of the global environment into which the system is placed. Therefore, a protein-encased sensitizer localized in the mitochondria would arguably have the same photophysics as that protein-encased sensitizer at the plasma membrane, for example. One thus obtains a useful tool to study processes modulated by spatially localized ROS. One ROS of interest is singlet oxygen, O2 (a1 Δg ). We recently developed a singlet oxygen photosensitizing protein, SOPP, in which flavin mononucleotide, FMN, is encased in a re-engineered light-oxygen-voltage protein. One goal was to ascertain how a version of this system, SOPP3, which selectively makes O2 (a1 Δg ), invitro, behaves in a cell. We now demonstrate that SOPP3 undergoes exacerbated irradiation-mediated bleaching when expressed at either the plasma membrane or mitochondria in stable cell lines. We find that the environment around the SOPP3 system affects the bleaching rate, which argues against one of the key suppositions in support of a protein-encased chromophore.

The effect of natural and anthropogenic nutrient and sediment loads on coral oxidative stress on runoff-exposed reefs

Recently, corals on the Great Barrier (GBR) have suffered mass bleaching. The link between ocean warming and coral bleaching is understood to be due to temperature-dependence of complex physiological processes in the coral host and algal symbiont. Here we use a coupled catchment-hydrodynamic-biogeochemical model, with detailed zooxanthellae photophysiology including photoadaptation, photoacclimation and reactive oxygen build-up, to investigate whether natural and anthropogenic catchment loads impact on coral bleaching on the GBR. For the wet season of 2017, simulations show the cross-shelf water quality gradient, driven by both natural and anthropogenic loads, generated a contrasting zooxanthellae physiological state on inshore versus mid-shelf reefs. The relatively small catchment flows and loads delivered during 2017, however, generated small river plumes with limited impact on water quality. Simulations show the removal of the anthropogenic fraction of the catchment loads delivered in 2017 would have had a negligible impact on bleaching rates.

The effect of plastic debris attachment to the health of branching corals in Kelapa Dua Island, Thousand Islands

Plastic marine debris are a potential threat to the life of marine organisms such as corals. This study aimed to analyze the effect of different plastic waste attachments on the bleaching rate and the health of branching corals at Kelapa Dua Island. Branching coral colonies consisted of 15 fragments of Porites cylidrica at the water depth of 80-90 cm, then treated with plastic waste (control, clear plastic, sack plastic, packaging plastic, and black plastic) for four days. Determination of color changes in corals was determined using Adobe Photoshop CC 2019 and Image j software to obtain the area of the discoloration. The treatment with black plastic became most impactful, with a discoloration area of 5.33 ± 0.48 cm2 and a healthy percentage of 73.62 ± 2.00%. Results of the linear regression between coral discoloration rate and light intensity showed a negative correlation, with r = -0.77 and R2 = 0.59, then between the percentage of coral health and light intensity showed a positive correlation, with r = 0.83 and R2 = 0.69. These results indicated that the decrease in light intensity due to the covered plastic debris affected the discoloration rate and the health percentage of branching coral.

Plasma-catalytic Efficiency on the Discolouration of Sunset Yellow FCF in a Glidarc Plasma Reactor in Presence of WO₃ Used as Catalyst

In this work, we highlight the plasma-catalytic effect of gliding arc discharge on the bleaching of azo dye sunset yellow FCF in aqueous solution. The effect has been studied in the presence of tungsten oxide as a catalyst in the glidarc reactor. The catalyst has been synthesized via acid precipitation process. The product obtained was characterized by X-ray powder diffraction (XRD), Fourier Transform Infrared (FTIR) and Nitrogen Physisorption. The results showed firstly monoclinic structure of WO3 catalyst. The maximum bleaching rates obtained are 17% and 52.5% after 30 min for initial dye concentration of 25 mg.L-1 for plasma alone and plasma-catalyst, respectively. These results have clearly shown that gliding arc discharge has a double effect, in on hand as a source of hydroxyl radical and on other hands as a source of radiation able to excite the catalyst. The effects of initial pH and photocatalyst loading have been studied.

Insights into blue light accelerated tooth whitening

ObjectiveTo test the hypotheses that blue light accelerates whitening through either (1) direct photobleaching or (2) photon-assisted oxidation using sequential longitudinal bleaching. MethodsThirty extracted human tooth samples having natural life accumulated color were divided over five groups: A. 9h light + 10h 6% H2O2 gel + 6h light & 6% H2O2 combined; B. 9h 6% H2O2 gel + 10h light + 6h light & 6% H2O2 combined; C. 11 h light & 6% H2O2 combined; D. 8.45h 25 %H2O2 gel + 10h of light only + 6h light & 25% H2O2 combined E. 10.45 h light & 25 %H2O2 combined. Blue light (456nm) was used at 190 mW/cm2. Color change (ΔE) was measured over time, and reported after 48h color stabilization. ResultsGroups A, B and D reached saturation in the first phase (at 9h) at a ΔE of 4.3 ± 0.7, 4.9 ± 1.3 and 10.9 ± 2.2, respectively. Groups C and E achieved in the same time a significantly higher ΔE of 14.2 ± 1.7 and 15.6 ± 1.9, respectively. Subsequently adding the opposite single modality to groups A, B and D for 10h did reach an end stage at 8.1 ± 1.3, 8.8 ± 1.8 and 10.8 ± 1.4 ΔE, respectively. The final 6h treatment combining light and H2O2 showed in these groups a statistically significant step in ΔE reaching 12.9 ± 1.4, 10.7 ± 2.5 and 15.3 ± 1.7, respectively. ConclusionsBlue light significantly increases bleaching rate and final achievable ΔE.This sequential whitening study provides a first indication that this enhanced bleaching is the result of the hypothesized light mechanisms acting in parallel to hydrogen peroxide bleaching. Clinical significanceThis study shows that blue light can accelerate whitening, within the limits of an in-vitro model. The findings help the clinician explain to their patients that in light accelerated whitening the light not merely accelerates the bleaching process, but that it attacks more stain compounds than peroxide alone does.

Ultraviolet plasmonic enhancement of the native fluorescence of tryptophan on aluminum nano-hole arrays

The native fluorescence of biomolecules has been used in analytical chemistry to determine the concentration of an analyte. However, detecting biomolecules based on their intrinsic fluorescence at low concentration is challenging due to their small quantum yield and poor photon stability. Ultraviolet plasmonics have been reported to increase the photon yield and the photon stability of the native fluorescence of biomolecules such as DNA, peptides, and proteins. However, the experimentally reported count rate, or net enhancement factor, is small-with 80× for DNA and 14× for amino acids. Here we report native fluorescence enhancement of tryptophan on aluminum hole-arrays. By optimizing excitation geometry and the hole spacings, we are able to achieve a 47× net enhancement factor, the highest reported in the literature for tryptophan molecules. We conducted photobleaching experiments and observed a 2.3× reduction in the fast photon bleaching rate and 1.9× reduction in the slow photon bleaching rate on an aluminum hole-array with 300 nm periodicity compared to an aluminum thin film. The enhancement of the total photon yield reaches 58×, which is a result of the enhanced radiative rate. This study shows that periodic aluminum hole-arrays allow detection of tryptophan at concentration levels lower than previously reported, underpinning further research into label-free biosensing.

Severe coral bleaching of Siderastrea stellata at the only atoll in the South Atlantic driven by sequential Marine Heatwaves

Abstract: Threatened by global warming and extreme climatic events, such as El Niño Southern Oscillation (ENSO) and Marine Heatwaves (MHW), coral reefs worldwide faced the worst bleaching and mortality event between 2014 and 2017, induced by the 2015/2016 ENSO. We evaluated the impacts of ENSO and MHW episodes on bleaching and mortality frequencies of Siderastrea stellata at Rocas Atoll, Southwestern Atlantic, using visual censuses conducted in 2016, 2017 and 2019. Bleaching rate varied significantly along the sampling period (11.71% in 2016, 1.52% in 2017, and 88% in 2019), but mortality was always less than 4%. Bleaching events in Atlantic reefs have been constantly associated with ENSO, until these recent events of the last two years. We suggest that MHW were probably the primary driver of the observed bleaching, especially in 2019, when much higher bleaching rates were observed than in ENSO periods. Although Southwestern Atlantic massive corals are considered more resistant to thermal stress than reefs corals worldwide, the strong events registered since 2019 highlight the need for continuous monitoring to better understand coral bleaching dynamics and improve predictions on the effects of global change in the region.

First reliable chronology for the Early Khvalynian Caspian Sea transgression in the Lower Volga River valley

During the late Quaternary, dramatic changes in relative sea level (~170 m) are known to have occurred in the Caspian Sea. However, all previous attempts at resolving the uncertainty associated with the timing of these transgressive/regressive events, primarily using radiocarbon, have produced inconclusive or controversial results. Here we present the first reliable chronology for the largest known transgression (Early Khvalynian). This was derived using optically stimulated luminescence (OSL) analysis of sand‐sized quartz, with support from infrared stimulated luminescence (IRSL) from K‐rich feldspar grains, all extracted from 16 sediment samples collected along the Lower Volga River. These samples were taken from loessic sediments, marine clays (known as Chocolate Clays) and the overlying modern soils exposed at three sections (Srednyaya Akhtuba, Raygorod, Leninsk) ~200 km upstream of the present‐day estuary. The differential bleaching rates of the quartz OSL and feldspar IRSL signals were used to evaluate the degree of resetting of quartz (and feldspar) signals; it was possible to conclude that all signals, and particularly quartz OSL, were sufficiently reset at deposition to allow accurate age estimation. Our results show unambiguously that the Early Khvalynian marine Chocolate Clays present at all three sections were deposited post‐LGM, between ~17 and ~13.1 ka ago. These age estimates are further constrained by those from the overlying Kastanozem soils (9.6–0.7 ka) and underlying loess‐soil series (32–19 ka), confirming a young (17–13 ka) age of the transgressive stage of the Early Khvalynian. Relative sea level during this period must have been well above the sampling altitudes of 11.7 m a.s.l. (Srednyaya Akhtuba), 11.3 m a.s.l. (Raygorod) and 4.7 m a.s.l. (Leninsk) to explain the absence of significant alluvial sand and to allow the deposition of the fine Chocolate Clays marker horizon.

Bleaching of blue light stimulated luminescence of quartz by moonlight

Moonlight is sunlight reflected from the moon’s surface. It is additionally modulated by the Earth’s atmosphere, dust and pollutants on its way to the surface of the Earth. This contribution reports the bleaching rates of blue light stimulated luminescence (BLSL) signal of Quartz under full moonlight exposure at the Earth’s surface. Quartz BLSL reduced to 70% by an exposure of 5 hrs moonlight, is in contrast to ~90% reduction in < 3 s with daylight. This was anticipated due to (a) reduced moonlight flux by about a factor of half a million (Agrawal in Lat. Am. J. Phys. Educ. 4(2):325–328, 2010; J. Phys. Astron. 5(1):1–15, 2017); (b) inverse power law dependence of bleaching efficiency on wavelength (Spooner in The validity of optical dating based on feldspar, Ph.D. Thesis, Oxford University, Oxford, 1993; Chen and McKeever in Theory of Thermoluminescence and related phenomena, World Scientific Publications, London, 1997, Chen and Pagonis in Thermally and optically stimulated luminescence: A simulation approach, Wiley and Sons, Chichester, 2011); and (c) moonlight and daylight have spectral peaks around 650 and 550 nm, respectively. Deconvolution of OSL components suggests that moonlight affects the fast component of OSL signal the most. This has ramification for the application in polar regions, where the availability of daylight is at a premium during the winter months. Within a given context, it is conjectured that this could be used to infer the seasonality of sediment transport.

Fluorescent photochromic complex of 1,8-naphthalimide derivative and benzopyrane containing benzo-18-crown-6 ether

We present here design, preparation, characterization, and properties of a photochromic supramolecular complex of benzopyran containing benzo-18-crown-6-ether 1 with 4-aminonaphthalimide 2 as a fluorophore. Phototransformation of the supramolecular complex 1⋅2 is accompanied by the appearance of a predominantly open TC form, which is consistent with the monoexponential bleaching curve of an open form at room temperature. Compared with free benzopyran 1, the bleaching rate is increased by 5–6 times in the presence of 2. From a synthetic point of view, varying the components in the supramolecular complex is more preferable to obtain a system with the desired characteristics. Thus, this study demonstrates that the supramolecular approach is promising for systems that contain photochromic and fluorescent components that influence each other.

Photo-induced bleaching and thermally stimulated recovery of BAC-P in Bi-doped phosphosilicate fibers.

The first results of the study on photobleaching and thermally induced recovery in Bi-doped phosphosilicate fiber have been presented. It was revealed that the rate of bleaching of phosphor-related Bi active center (BAC-P) becomes slower with the decrease of photon energy. The quadratic dependence of the bleaching rate of BAC-P on laser power is obtained under 532 nm laser irradiation. The effect of temperature on the bleaching dynamics of BAC-P is also investigated under 532 nm radiation, suggesting a thermally aggravated bleaching process upon heating at certain temperatures (≥300∘C). Furthermore, the thermal recovery of bleached Bi-doped silica-based fiber (BDF) is investigated and a 13% increase of luminescence is achieved upon thermal quenching for 5 min at 400ºC. The underlying mechanism of photobleaching and thermo-stimulated recovery process of BAC-P is also discussed.

Reaction Mechanism of Phenolic Lignin and High Concentration Chlorine Dioxide and Its Application.

In fact, the chemical reaction rate of traditional chlorine dioxide bleaching of pulp is too fast to observe the intermediate process. The mechanism behind the reaction of 4-hydroxy-3-methoxyacetophenone (APO), a phenolic lignin model compound, with high concentrations of chlorine dioxide was investigated. Individual solutions of each compound and a mixture of the two were analyzed by UV–vis spectrophotometry, and an absorbance band at 260 nm was observed for the stable benzoquinone intermediates at room temperature. Free chlorine dioxide displayed an absorbance at 360 nm and changes in this absorbance were studied with different APO concentrations. A fixed molar ratio of 1:3 was obtained between APO and chlorine dioxide consumption. The intermediate absorbance demonstrated a linear relationship with the APO concentration. The reaction path between APO and chlorine dioxide at high concentrations was speculated, and it was observed that the activity of C1, C2, C3, C5, and C6 on the APO benzene ring was enhanced when high concentrations of chlorine dioxide were present. From these results, a new method for efficient and clean chlorine dioxide bleaching can be developed.