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The photochemical reactions between 1-naphthol (1-NP) and the superoxide anion radical ([O.sub.2.sup.*-]) were investigated in detail by using 365 nm UV irradiation. The results showed that the conversion rate of 1-NP decreased with the increase of the initial concentration of 1-NP, whereas by increasing the pH and riboflavin concentration, the photochemical reaction was accelerated. The second-order reaction rate constant was estimated to be (3.64 [+ or -] 0.17) * [10.sup.8] L [mol.sup.-1] [s.sup.-1]. The major photolysis products identified by using gas chromatography--mass spectrometry (GC-MS) were 1,4-naphquinone and 2,3-epoxyresin-2,3-dihydro-1,4-naphquinone, and their reaction pathways were also discussed. An atmospheric model showed that both the bulk water reaction and the heterogeneous surface reaction deserve attention in atmospheric aqueous chemistry. Key words: superoxide radicals, 1-naphthol, photolysis kinetics, reaction mechanism, thermodynamics model. Nous avons etudie en detail les reactions photochimiques entre le 1naphtol (1NP) et le radical anionique superoxyde ([O.sub.2.sup.*-]) par irradiation UV a 365 nm. Les resultats ont montre que le taux de conversion du 1naphtol diminuait avec l'augmentation de la concentration initiale de ce dernier, tandis que l'augmentation du pH et de la concentration de la riboflavine accelerait la reaction photochimique. Nous avons estime que la constante de vitesse de reaction, de second ordre, etait de (3,64 [+ or -] 0,17) * [10.sup.8] L [mol.sup.-1] [s.sup.-1]. Les principaux produits de photolyse que nous avons identifies en utilisant la chromatographie en phase gazeuse couplee a la spectrometrie de masse (GC-MS) etaient la 1,4naphtoquinone et la 2,3-epoxyresine-2,3-dihydro-1,4-naphtoquinone. Nous discutons egalement des mecanismes de reaction. A l'aide d'un modele atmospherique, nous avons montre que la reaction dans un volume d'eau et la reaction sur une surface heterogene presentait un interet dans le domaine de la chimie atmospherique de l'eau. [Traduit par la Redaction] Mots-cles: radicaux superoxide, 1-naphtol, cinetique de la photolyse, mecanisme de reaction, modele thermodynamique., Introduction Polycyclic aromatic hydrocarbons (PAHs, also known as poly-nuclear aromatic hydrocarbons or PNAs) are complex chemical substances with two or more aromatic rings. (1) They are important environmental pollutants and [...]

Stability under high‐temperature environments is crucial for amylase to function in starch‐based industries. This study develops a method of modifying protein surfaces by combining computer‐aided tools including FoldX, PoPMuSiC, Discovery Studio, and I‐Mutant 2.0 with conserved sequence analysis. A truncated α‐amylase ∆AmyPTG from Parageobacillus thermoglucosidasius DSMZ 2542 is rationally designed through this method to improve its thermostability. Seven single‐site variants are constructed and five of them displayed enhanced thermostability. Next, three double‐site variants are constructed with one particularly successful double‐site variant N31RT213R, exhibiting a 4.3‐fold longer half‐life at 80 °C. Notably, the specific activity of N31RT213R reaches 10 567.16 U mg−1, higher than ∆AmyPTG (6645.43 U mg−1). When applied to the corn starch liquefaction reaction, the mutant N31RT213R gets a higher yield of product concentration of about 255.70 µg mL−1, compared to 190.72 µg mL−1 for ∆AmyPTG. Intramolecular forces analysis and surface electrostatic charges analysis are conducted to determine possible causes for the improvement. Also, molecular dynamics simulation is used to analyze the flexibility shifts of the entire protein. This innovative rational engineering approach has proven to be a successful strategy for the selection of hot spots for protein thermostability evolution and has the potential to be applied to other enzymes. [ABSTRACT FROM AUTHOR]

Objective(s): Recently directed methods of inner ear drug delivery underscore the necessity for understanding critical anatomical dimensions. This study examines anatomical measurements of the human middle and inner ear relevant for inner ear drug delivery studied with three different imaging modalities. Methods: Post‐mortem human temporal bones were analyzed using human temporal bone histopathology (N = 24), micro computerized tomography (μCT; N = 4), and synchrotron radiation phase‐contrast imaging (SR‐PCI; N = 7). Nine measurements involving the oval and round windows were performed when relevant anatomical structures were visualized for subsequent age‐controlled analysis, and comparisons were made between imaging methods. Results: Combined human temporal bone histopathology showed the mean distance to the saccule from the center of the stapes footplate (FP) was 2.07 ± 0.357 mm and the minimum distance was 1.23 mm. The mean distance from the round window membrane (RWM) to the osseous spiral lamina (OSL) was 1.75 ± 0.199 mm and the minimum distance was 1.43 mm. Instruments inserted up to 1 mm past the center of the FP are unlikely to cause saccular damage, provided there are no endolymphatic hydrops. Similarly, instruments inserted up to 1 mm through the RWM in the trajectory toward the OSL are unlikely to cause OSL damage. Conclusion: The combined analyses of inner‐ear dimensions of age‐controlled groups and imaging modalities demonstrate critical dimensions of importance to consider when inserting delivery vehicles into the human cochlea. Level of Evidence: N/A Laryngoscope, 134:2879–2888, 2024 [ABSTRACT FROM AUTHOR]

The photochemical reaction kinetics and mechanism of bisphenol A (BPA) with potassium persulfate ([K.sub.2][S.sub.2][O.sub.8]) were investigated by using 266 nm laser flash photolysis and gas chromatography mass spectrum (GC-MS) technique. Sulfate radical (SO4*~), generated upon K2S2O8 photolysis, reacted with BPA with the overall rate constant of (1.61 6 0.15) x [10.sup.9] L [mol.sup.-1] [s.sup.-1], and two main reaction mechanisms were involved. One was addition channel to generate BPA-[SO.sub.4]*~ adduct with a specific second-order rate constant of (1.09 6 0.15) x [10.sup.9] L [mol.sup.-1] [s.sup.-1]. Molecular oxygen was involved in the decay of the BPA-SO4*~ adduct with a rate constant of (1.28 6 0.14) x [10.sup.8] L [mol.sup.-1] [s.sup.-1]. Another channel was the formation of BPA's phenoxyl radical, likely derived from a deprotonation of the cation radical ([BPA*.sup.+]) generated from single electron transfer reactions. The specific rate constant of BPA's phenoxyl radical formation was determined to be (6.16 6 0.08) x [10.sup.8] L [mol.sup.-1] [s.sup.-1]. The overall rate constant was in line with the sum of aforementioned two specific rate constants for two main reaction channels. By comparing these rate constants, it was indicated that [SO.sub.4]*~ addition channel accounted for ~65% (1.09/1.61) to the overall reaction, and phenoxyl radical formation accounted for only ~35% (0.62/1.61). The transformation products of BPA were identified by using GC-MS including 4-isopropylphenol, 4-isopropenylphenol, and 2,4-di-tert-butylphenol, and the reaction mechanism was proposed. These results may provide microscopic kinetics and mechanism information on BPA degradation using [SO.sub.4]*~-based advanced oxidation processes. Key words: bisphenol A (BPA), sulfate radical (SO4*~), transient kinetics, mechanism, laser flash photolysis. Nous avons etudie la cinetique et le mecanisme de la reaction photochimique du bisphenol A (BPA) avec le persulfate de potassium ([K.sub.2]S2[O.sub.8]) en utilisant la technique de photolyse eclair au laser, a une longueur d'onde de 266 nm, et de chromatographie en phase gazeuse couplee a la spectrometrie de masse (GC-MS). Le radical sulfate ([SO.sub.4]*~) genere par photolyse du K2S2O8 reagit avec le BPA avec une constante de vitesse globale de (1,61 6 0,15) x [10.sup.9] L [mol.sup.-1] [s.sup.-1], faisant intervenir deux mecanismes de reaction principaux. L'un procede par une addition pour generer un adduit BPA-[SO.sub.4]*~ avec une constante de vitesse specifique de second ordre de (1,09 6 0,15) x [10.sup.9] L [mol.sup.-1] [s.sup.-1]. L'oxygene moleculaire intervient dans la degradation de l'adduit BPA-[SO.sub.4]*~, qui se produit avec une constante de vitesse de (1,28 6 0,14) x [10.sup.8] L [mol.sup.-1] [s.sup.-1]. L'autre mecanisme procede par la formation du radical phenoxyle du BPA, qui derive probablement de la deprotonation du radical cationique ([BPA*.sup.+]) genere par des reactions de transfert d'un electron. Nous avons determine que la constante de vitesse specifique de formation du radical phenoxyle du BPA etait de (6,16 6 0,08) x [10.sup.8] L [mol.sup.-1] [s.sup.-1]. La constante de vitesse globale concordait avec la somme des deux constantes de vitesse specifiques mentionnees ci-dessus pour les deux mecanismes de reaction principaux. En comparant ces constantes de vitesse, nous avons deduit que la voie d'addition du [SO.sub.4]*~ representait environ 65 % (1,09/1,61) de la reaction globale, tandis que la formation du radical phenoxyle ne representait qu'environ 35 % (0,62/1,61). Nous avons identifie les produits de transformation du BPA par GC-MS, notamment le 4-isopropylphenol, le 4-isopropenylphenol et le 2,4-di-tert-butylphenol, et nous avons propose un mecanisme de reaction. Ces resultats pourraient fournir des donnees sur la cinetique microscopique et le mecanisme de la degradation du BPA par des processus d'oxydation avances par le [SO.sub.4]*-. Mots-cles: bisphenol A (BPA), radical sulfate ([SO.sub.4]*~), cinetique transitoire, mecanisme, photolyse eclair au laser., Introduction Bisphenol A (BPA) is proverbially used in the industrial production of coatings, plastics, and epoxy resins. (1,2) It has been detected in numerous water bodies, with concentrations of 0.1-12 [...]