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Journal of the American Chemical Society Apr 2024Nitroaromatic compounds are major constituents of the brown carbon aerosol particles in the troposphere that absorb near-ultraviolet (UV) and visible solar radiation and...
Nitroaromatic compounds are major constituents of the brown carbon aerosol particles in the troposphere that absorb near-ultraviolet (UV) and visible solar radiation and have a profound effect on the Earth's climate. The primary sources of brown carbon include biomass burning, forest fires, and residential burning of biofuels, and an important secondary source is photochemistry in aqueous cloud and fog droplets. Nitrobenzene is the smallest nitroaromatic molecule and a model for the photochemical behavior of larger nitroaromatic compounds. Despite the obvious importance of its droplet photochemistry to the atmospheric environment, there have not been any detailed studies of the ultrafast photochemical dynamics of nitrobenzene in aqueous solution. Here, we combine femtosecond transient absorption spectroscopy, time-resolved infrared spectroscopy, and quantum chemistry calculations to investigate the primary steps following the near-UV (λ ≥ 340 nm) photoexcitation of aqueous nitrobenzene. To understand the role of the surrounding water molecules in the photochemical dynamics of nitrobenzene, we compare the results of these investigations with analogous measurements in solutions of methanol, acetonitrile, and cyclohexane. We find that vibrational energy transfer to the aqueous environment quenches internal excitation, and therefore, unlike the gas phase, we do not observe any evidence for formation of photoproducts on timescales up to 500 ns. We also find that hydrogen bonding between nitrobenzene and surrounding water molecules slows the S/S internal conversion process.
PubMed: 38572973
DOI: 10.1021/jacs.3c13826 -
Journal of the American Chemical Society Apr 2024In the long-standing quest to synthesize fundamental building blocks with key functional group motifs, photochemistry in the recent past has comprehensively established...
In the long-standing quest to synthesize fundamental building blocks with key functional group motifs, photochemistry in the recent past has comprehensively established its attractiveness. Amino alcohols are not only functionally diverse but are ubiquitous in the biologically active realm of compounds. We developed bench-stable bifunctional reagents that could then access the sparsely reported γ-amino alcohols directly from feedstock alkenes through energy transfer (EnT) photocatalysis. A designed 1,3-linkage across alkenes is made possible by the intervention of a radical Brook rearrangement that takes place downstream to the EnT-mediated homolysis of our reagent(s). A combination of experimental mechanistic investigations and detailed computational studies (DFT) indicates a radical chain propagated reaction pathway.
PubMed: 38569596
DOI: 10.1021/jacs.4c01667 -
ACS Physical Chemistry Au Mar 2024Electron transfer (ET) at molecule-metal or molecule-semiconductor interfaces is a fundamental reaction that underlies all electrochemical processes and...
Electron transfer (ET) at molecule-metal or molecule-semiconductor interfaces is a fundamental reaction that underlies all electrochemical processes and substrate-mediated surface photochemistry. In this study, we show that ET rates near a metal surface can be significantly manipulated by periodic driving (e.g., Floquet engineering). We employ the Floquet surface hopping and Floquet electronic friction algorithms developed previously to calculate the ET rates near the metal surface as a function of driving amplitudes and driving frequencies. We find that ET rates have a turnover effect when the driving frequencies increase. A Floquet Marcus theory is further formulated to analyze such a turnover effect. We then benchmark the Floquet Marcus theory against Floquet surface hopping and Floquet electronic friction methods, indicating that the Floquet Marcus theory works in the strong nonadiabatic regimes but fails in the weak nonadiabatic regimes. We hope these theoretical tools will be useful to study ET rates in the plasmonic cavity and plasmon-assisted photocatalysis.
PubMed: 38560755
DOI: 10.1021/acsphyschemau.3c00049 -
Nature Communications Mar 2024Photoreceptor proteins utilise chromophores to sense light and trigger a biological response. The discovery that adenosylcobalamin (or coenzyme B) can act as a...
Photoreceptor proteins utilise chromophores to sense light and trigger a biological response. The discovery that adenosylcobalamin (or coenzyme B) can act as a light-sensing chromophore heralded a new field of B-photobiology. Although microbial genome analysis indicates that photoactive B-binding domains form part of more complex protein architectures, regulating a range of molecular-cellular functions in response to light, experimental evidence is lacking. Here we identify and characterise a sub-family of multi-centre photoreceptors, termed photocobilins, that use B and biliverdin (BV) to sense light across the visible spectrum. Crystal structures reveal close juxtaposition of the B and BV chromophores, an arrangement that facilitates optical coupling. Light-triggered conversion of the B affects quaternary structure, in turn leading to light-activation of associated enzyme domains. The apparent widespread nature of photocobilins implies involvement in light regulation of a wider array of biochemical processes, and thus expands the scope for B photobiology. Their characterisation provides inspiration for the design of broad-spectrum optogenetic tools and next generation bio-photocatalysts.
Topics: Photochemistry; Bile Pigments; Biliverdine; Bacterial Proteins; Photoreceptors, Microbial; Light
PubMed: 38548733
DOI: 10.1038/s41467-024-46995-1 -
The Journal of Physical Chemistry... Apr 2024The radical-radical reaction between OH and HO has been considered for a long time as an important reaction in tropospheric photochemistry and combustion chemistry....
Accurate Kinetic Studies of OH + HO Radical-Radical Reaction through Direct Measurement of Precursor and Radical Concentrations with High-Resolution Time-Resolved Dual-Comb Spectroscopy.
The radical-radical reaction between OH and HO has been considered for a long time as an important reaction in tropospheric photochemistry and combustion chemistry. However, a significant discrepancy of an order of magnitude for rate coefficients of this reaction is found between two recent experiments. Herein, we investigate the reaction OH + HO via direct spectral quantification of both the precursor (HO) and free radicals (OH and HO) upon the 248 nm photolysis of HO using infrared two-color time-resolved dual-comb spectroscopy. With quantitative and kinetic analysis of concentration profiles of both OH and HO at varied conditions, the rate coefficient is determined to be (1.10 ± 0.12) × 10 cm molecule s at 296 K. Moreover, we explore the kinetics of this reaction under conditions in the presence of water, but no enhancement in the can be observed. This work as an independent experiment plays a crucial role in revisiting this prototypical radical-radical reaction.
PubMed: 38547368
DOI: 10.1021/acs.jpclett.4c00494 -
Pharmaceutics Mar 2024One of the major challenges in harnessing the therapeutic benefits of curcumin (an active ingredient from turmeric) is its poor bioavailability due to its short... (Review)
Review
One of the major challenges in harnessing the therapeutic benefits of curcumin (an active ingredient from turmeric) is its poor bioavailability due to its short biological half-life. In this regard, nanoformulations have shown tremendous hope for improving the pharmacokinetic and therapeutic behavior of curcumin by altering its biological stability and bioavailability. Biopolymers, especially alginate and chitosan, have received special attention as excipients to prepare nanoformulations of curcumin due to their abundant availability, biocompatibility, and amicability to form different types of self-assembled structures and ease of undergoing chemical modifications. However, there are certain challenges, such as poor water solubility under physiological conditions and heterogeneity with regard to molecular weight and large-scale production of well-preserved nanostructures. Substantial advancement has been achieved towards overcoming these challenges by developing newer derivatives through a chemical modifications approach, and this has ascertained the suitability of alginate and chitosan as excipients for drug delivery systems (DDS). The present minireview briefly discusses curcumin and its limitation as a drug molecule, carbohydrates as DDS, and the recent developments related to the alginate and chitosan-based nanoformulations of curcumin. Special emphasis has been given to highlighting the impact of alginate and chitosan-based nanoformulations in improving the therapeutic efficacy and bioavailability of curcumin.
PubMed: 38543316
DOI: 10.3390/pharmaceutics16030423 -
Pharmaceutics Mar 2024In the field of preparing cosmetic formulations, recent advances recommend the usage of excipients derived from biocompatible materials. In this context, the present...
The Preparation of Curcumin-Loaded Pickering Emulsion Using Gelatin-Chitosan Colloidal Particles as Emulsifier for Possible Application as a Bio-Inspired Cosmetic Formulation.
In the field of preparing cosmetic formulations, recent advances recommend the usage of excipients derived from biocompatible materials. In this context, the present study aimed to prepare and characterize the curcumin-loaded Pickering emulsion for possible applications in cosmetic formulation. The coconut oil which is often the component of skin care formulations is used as the oily phase. Curcumin, which is well known for absorbing solar radiation, is expected to work synergistically with coconut oil towards improving the sun protection factor (SPF) of the formulation. Additionally, curcumin can also protect the intracellular components through its well-known antioxidant mechanisms. The Pickering emulsion of coconut oil into water was prepared using the composite colloidal particles derived from β-carboxymethyl chitosan (CMC) and Gelatin-A (GA) as the emulsifying agent. The reaction conditions in terms of the weight ratios of CMC and GA, the pH of the reaction medium, the oil volume fraction, and the homogenization speed were optimized to obtain the most stable Pickering emulsion. The obtained systems were physico-chemically characterized by dynamic light scattering, zeta potential, optical microscopy, and rheometric measurements. The final CMC-GA-stabilized emulsion demonstrated an oil droplet size of 100 µm and a SPF value of 8.5 at a curcumin loading of 4 mg/mL. Additionally, the final formulation facilitated the uptake of curcumin into fibroblast (WI26) cells under in vitro conditions. Together, the investigation demonstrates a bio-inspired approach to prepare a curcumin-loaded green Pickering emulsion using biocompatible pharmaceutical grade excipients, which may find utility in cosmetic applications.
PubMed: 38543250
DOI: 10.3390/pharmaceutics16030356 -
Advanced Synthesis & Catalysis May 2023The electron donor-acceptor complex-enabled asymmetric photochemical alkylation strategy holds potential to attain elusive chiral α-alkylated aldehydes without an...
The electron donor-acceptor complex-enabled asymmetric photochemical alkylation strategy holds potential to attain elusive chiral α-alkylated aldehydes without an external photoredox catalyst. The photosensitizer-free conditions are beneficial concerning process costs and sustainability. However, lengthy organocatalyst preparation steps as well as limited productivity and difficult scalability render the current approaches unsuitable for synthesis on enlarged scales. Inspired by these limitations, a protocol was developed for the enantioselective α-alkylation of aldehydes based on the synergistic combination of visible light-driven asymmetric organocatalysis and a controlled continuous flow reaction environment. With the aim to reduce process costs, a commercially available chiral catalyst has been exploited to achieve photosensitizer-free enantioselective α-alkylations using phenacyl bromide derivates as alkylating agents. As a result of elaborate optimization and process development, the present flow strategy furnishes an accelerated and inherently scalable entry into enantioenriched α-alkylated aldehydes including a chiral key intermediate of the antirheumatic esonarimod.
PubMed: 38515505
DOI: 10.1002/adsc.202300289 -
Scientific Reports Mar 2024Corms of Gladiolus grandiflorus cv. "White Prosperity" was irradiated via red laser at wavelength 635 nm. Various morphological, flowering, elemental and chemical...
Corms of Gladiolus grandiflorus cv. "White Prosperity" was irradiated via red laser at wavelength 635 nm. Various morphological, flowering, elemental and chemical characterizations were studied. Irradiation with different power (5, 20, and 50 mW) and various irradiation time (0.0, 0.5, 1, 3, 5 and 10 min) was studied. Several characters), totaletermined include vegetative growth parameter (spouting days, plant height (cm), leaves number, leaves fresh and dry weights (g/plant), diameter of plant middle part (mm) and leaf area (cm), floral parameters (flowering days, vase life (day), fresh and dry weights of inflorescence (g/plant), number of flowers per inflorescence, inflorescence length(cm), flowers diameter(cm), number of corms per plant, corms fresh weight(g/plant), circumference/ corms), pigments [total chlorophylls in leaves (SPAD), anthocyanin content (mg/100 g F.W.) in petals], NPK (%) in new corms and chemical composition in corms; total carbohydrates (%),total phenol (μg CE/g (%),total flavonoid (μg CE/g) (%), antioxidant (DPPH IC50 (μg /ml (%), and proline content (μ moles/g). The results showed that the medium level (20 mW) of He-Ne laser at 5 min caused favorable changes in the leaf anatomical structures and other studied characters followed by the low level (5 mW) of He-Ne laser at 5min. 112 bands emerged from 22 SSR primers, ranging between 130 and 540 bp, with 32 bands having polymorphism ranging from 17-100%. Out of the 22 SSR primers, 3 primers exhibited a high polymorphism percentage, i.e., SSR6, SSR16 and SSR22 which exhibited 7 positive markers. These findings revealed the efficiency of SSR primers for differentiating gladiolus plants and revealed that some alleles were affected by laser in their corms and the expression resulted in color or abnormalities in leaves and/or flowers. Mutation in some alleles could result in abnormalities like mutation in the allele with 410 bp revealed by SSR16.
Topics: Flowers; Plant Leaves; Iridaceae; Lasers; Growth and Development; Gene Expression
PubMed: 38491044
DOI: 10.1038/s41598-024-56430-6 -
Nature Communications Mar 2024Reactive uptake of dinitrogen pentaoxide (NO) into aqueous aerosols is a major loss channel for NO in the troposphere; however, a quantitative understanding of the...
Reactive uptake of dinitrogen pentaoxide (NO) into aqueous aerosols is a major loss channel for NO in the troposphere; however, a quantitative understanding of the uptake mechanism is lacking. Herein, a computational chemistry strategy is developed employing high-level quantum chemical methods; the method offers detailed molecular insight into the hydrolysis and ammonolysis mechanisms of NO in microdroplets. Specifically, our calculations estimate the bulk and interfacial hydrolysis rates to be (2.3 ± 1.6) × 10 and (6.3 ± 4.2) × 10 ns, respectively, and ammonolysis competes with hydrolysis at NH concentrations above 1.9 × 10mol L. The slow interfacial hydrolysis rate suggests that interfacial processes have negligible effect on the hydrolysis of NO in liquid water. In contrast, NO ammonolysis in liquid water is dominated by interfacial processes due to the high interfacial ammonolysis rate. Our findings and strategy are applicable to high-chemical complexity microdroplets.
PubMed: 38491022
DOI: 10.1038/s41467-024-46674-1