Effects of Conditioning Contractions on Lower-Body Explosive Force Post-Static Stretching.

The present study assessed the impacts of two distinct protocols, static stretching(StS, 4 sets of 30 seconds) and static stretching combined with conditioning contractions(10 repetitive drop jumps)(SC), on neuromuscular response and rate of force development(RFD) in the lower limbs during squat jumps (SJs) at varying initial knee-joint angles(60°,90°,120°). Twelve participants completed three randomized experimental trials(no intervention, StS intervention, and SC intervention). Except for the intervention segments, each trial included standardized warm-ups and SJs at three different angles. Data were collected using a 3-dimensional injury motion capture system, an electromyography(EMG) recording system, and a force platform. The collected EMG data were subjected to amplitude calculations, while force-time data were used for RFD computation. Neither StS nor SC significantly impacted the average or peak EMG amplitudes of the five muscles examined(p > 0.05). However, at an initial knee-joint angle of 120°, the StS group demonstrated significantly lower RFD values at three distinct phases(0-50 ms, 50-100 ms, and 0-peakforce) compared to those seen in the SC and control groups(p < 0.05). For activities starting with a knee-joint angle of 120°, it is recommended to either avoid StS or combine it with ten repetitive drop jumps to mitigate any potential negative impact on explosiveness.

Cinnamyl Alcohol Attenuates Adipogenesis in 3T3-L1 Cells by Arresting the Cell Cycle.

Cinnamyl alcohol (CA) is an aromatic compound found in several plant-based resources and has been shown to exert anti-inflammatory and anti-microbial activities. However, the anti-adipogenic mechanism of CA has not been sufficiently studied. The present study aimed to investigate the effect and mechanism of CA on the regulation of adipogenesis. As evidenced by Oil Red O staining, Western blotting, and real-time PCR (RT-PCR) analyses, CA treatment (6.25-25 µM) for 8 d significantly inhibited lipid accumulation in a concentration-dependent manner and downregulated adipogenesis-related markers (peroxisome proliferator-activated receptor γ (PPARγ), CCAAT/enhancer-binding protein α (C/EBPα), fatty acid binding protein 4 (FABP4), adiponectin, fatty acid synthase (FAS)) in 3-isobutyl-1-methylxanthine, dexamethasone, and insulin(MDI)-treated 3T3-L1 adipocytes. In particular, among the various differentiation stages, the early stage of adipogenesis was critical for the inhibitory effect of CA. Cell cycle analysis using flow cytometry and Western blotting showed that CA effectively inhibited MDI-induced initiation of mitotic clonal expansion (MCE) by arresting the cell cycle in the G0/G1 phase and downregulating the expression of C/EBPß, C/EBPδ, and cell cycle markers (cyclin D1, cyclin-dependent kinase 6 (CDK6), cyclin E1, CDK2, and cyclin B1). Moreover, AMP-activated protein kinase α (AMPKα), acetyl-CoA carboxylase (ACC), and extracellular signal-regulated kinase 1/2 (ERK1/2), markers of upstream signaling pathways, were phosphorylated during MCE by CA. In conclusion, CA can act as an anti-adipogenic agent by inhibiting the AMPKα and ERK1/2 signaling pathways and the cell cycle and may also act as a potential therapeutic agent for obesity.

Simultaneous determination of the free and total forms of nonylphenol, nonylphenol monoethoxylate, and nonylphenol diethoxylate in human urine by gas chromatography-mass spectrometry.

Nonylphenol (NP), nonylphenol monoethoxylate (NP1EO), and nonylphenol diethoxylate (NP2EO) are widely used in various daily products and have been cataloged as endocrine-disrupting chemicals. Due to their high lipophilicity and low biodegradability, these compounds remain in the environment and enter the human body through the food chain. Growing concerns regarding the potential negative effects of NP, NP1EO, and NP2EO on human health have raised the need for biomonitoring to investigate human exposure to these compounds. In this study, a simultaneous analysis method using solid-phase extraction (SPE) combined with gas chromatography-mass spectrometry (GC-MS) was established by controlling the background contamination of NP, NP1EO, and NP2EO, which are ubiquitous in laboratory environments. The proposed method showed proper linearity of over 0.999 and a recovery greater than 85.8% for all analytes. Accuracy and precision were verified in ranges of 92.97-116.30% and 0.65-9.29%, respectively. The detection limits for NP, NP1EO, and NP2EO were 0.0363 µg L-1, 0.0401 µg L-1, and 0.0364 µg L-1, respectively, which were suitable for determining the trace analytes in human urine. Therefore, this simple and integrated analytical method was applied to measure the free and total forms of the target analytes in 25 human urine samples collected in Korea. Overall, free NP, NP1EO, and NP2EO were detected with average contents of 3.94 ± 4.14 µg L-1, 4.63 ± 2.62 µg L-1, and 0.293 ± 0.638 µg L-1, respectively, and with total NP, NP1EO, and NP2EO contents of 6.14 ± 8.24 µg L-1, 5.99 ± 2.91 µg L-1, and 0.806 ± 1.10 µg L-1, respectively. These data showed that these compounds are prevalent in human urine, and indicate the need for further studies.

Oral discourse skills: Dimensionality of comprehension and retell of narrative and expository texts, and the relations of language and cognitive skills to identified dimensions.

We examined the dimensionality of oral discourse skills (comprehension and retell of texts) and the relations of language and cognitive skills to the identified dimensions. Data were from 529 English-speaking second graders (Mage = 7.42; 46% female; 52.6% Whites, 33.8% African Americans, 4.9% Hispanics, 4.7% two or more races, .8% Asian Americans, .6% American Indians, .2% Native Hawaiians, 2.5% unknown; data from 2014-2015 to 2016-2017). Confirmatory factor analysis revealed that oral discourse skills are best described as four related but dissociable dimensions of narrative comprehension, narrative retell, expository comprehension, and expository retell (rs = .59-.84). Language and cognitive skills had different patterns of relations to the identified dimensions and explained larger amounts of variance in comprehension than in retell.

Executive Functions and Morphological Awareness Explain the Shared Variance Between Word Reading and Listening Comprehension.

Purpose: A large body of literature showed that word reading and listening comprehension-two proximal predictors of reading comprehension according to the simple view of reading-are related. Grounded on the direct and indirect effects model of reading (Kim, 2020a, 2020b, 2023), we examined the extent to which the relation is explained by domain-general cognitions or executive functions (working memory and attentional control) and emergent literacy skills (language and code-related skills including morphological awareness, phonological awareness, orthographic pattern recognition, letter naming fluency, and rapid automatized naming). Method: Data were from English-speaking children in Grade 1 (N = 372; 52% boys; 60% White children, 26% African American children, 6% multiracial children, 6% Hispanic children, and 2% Asian American children). Results: Results from structural equation models showed that word reading and listening comprehension were moderately related (.54). When working memory and attentional control were included as predictors, the relation became weaker (.39). When morphological awareness was additionally included, they were no longer related (.05). The other emergent literacy skills did not add explanatory power beyond executive functions and morphological awareness. Conclusion: These results indicate that executive functions and morphological awareness largely explain the shared variance between word reading and listening comprehension for English-speaking beginning readers.

Effect of Polycan, a ß-Glucan from Aureobasidium pullulans SM-2001, on Inflammatory Response and Intestinal Barrier Function in DSS-Induced Ulcerative Colitis.

Ulcerative colitis (UC), a subtype of inflammatory bowel disease, is a chronic gastrointestinal inflammatory disease with unclear etiology and pathophysiology. Herein, we determined the effects of extracellular polysaccharides purified from Aureobasidium pullulans SM-2001 (Polycan) on tight junction protein expression, inflammation, and apoptosis in a dextran sodium sulfate (DSS)-induced acute colitis model. Fifty mice were divided into normal, DSS, DSS + Polycan 250 mg/kg (Polycan 250), DSS + Polycan 500 mg/kg (Polycan 500), and DSS + 5-aminosalicylic acid 100 mg/kg (5-ASA) groups. Their body weights, colon lengths, histological changes in colon tissue, and tight junction function were observed. Results showed that Polycan 250, Polycan 500, and 5-ASA significantly inhibited body weight loss compared with DSS. Similar to 5-ASA, Polycan 500 exhibited preventive effects on colon length shortening and histological changes in colon tissues. Polycan inhibited the DSS-induced decrease in fluorescein isothiocyanate-dextran permeability and myeloperoxidase activity. Moreover, Polycan significantly recovered serum cytokine (e.g., tumor necrosis factor-α, interleukin (IL)-6, and IL-1ß) or mRNA expression in colon tissue compared with DSS. Polycan also inhibited apoptosis by reducing caspase-3 activity and the Bcl-2 associated X/B-cell lymphoma 2 (Bcl-2) ratio. Additionally, DSS treatment significantly reduced microbial abundance and diversity, but the administration of Polycan reversed this effect. Collectively, Polycan protected intestinal barrier function and inhibited inflammation and apoptosis in DSS-induced colitis.

Comparing the Effects of Static Stretching Alone and in Combination with Post-Activation Performance Enhancement on Squat Jump Performance at Different Knee Starting Angles.

We aimed to investigate the impact of isolated static stretching (4 sets of 30 seconds) and its combined form with 10 repetitive drop jumps on lower limb performance during squat jumps at different knee joint starting angles (60°, 90°, and 120°). Thirteen participants completed three randomly ordered experimental visits, each including a standardized warm-up and squat jumps at three angles, apart from the intervention or control. Information was gathered through a three-dimensional movement tracking system, electromyography system, and force platform. The electromyography data underwent wavelet analysis to compute the energy values across the four wavelet frequency bands. The average power (Pavg), peak power (Ppeak), peak ground reaction force (GRFpeak), peak center of mass velocity (Vpeak), and force-velocity relationship at peak power (SFv) were extracted from the force and velocity-time data. The results revealed no significant influence of isolated static stretching, or its combined form with drop jumps, on the energy values across the frequency bands of the gastrocnemius, biceps femoris and rectus femoris, or the Pavg or Ppeak (P > 0.05). However, at 120°, static stretching reduced the GRFpeak (P = 0.001, d = 0.86) and SFv (P < 0.001, d = 1.12), and increased the Vpeak (P = 0.001, d = 0.5). The GRFpeak, Pavg, Ppeak, and SFv increased with an increase in the joint angle (P < 0.05), whereas the Vpeak decreased (P < 0.05). These findings suggest that static stretching does not diminish power output during squat jumps at the three angles; however, it alters GRFpeak, Vpeak, and the relative contributions of force and velocity to peak power at 120°, which can be eliminated by post-activation performance enhancement. Moreover, compared to 60° and 90°, 120° was more favorable for power and peak force output.

Uncovering Nitrosyl Reactivity at N-Heterocyclic Carbene Center.

N-heterocyclic carbenes (NHCs) have garnered much attention due to their unique properties, such as strong σ-donating and π-accepting abilities, as well as their transition-metal-like reactivity toward small molecules. In 2015, we discovered that NHCs can react with nitric oxide (NO) gas to form radical adducts that resemble transition metal nitrosyl complexes. To elucidate the analogy between NHC and transition metal NO adducts, here we have undertaken a systematic investigation of the electron- and proton-transfer chemistry of [NHC-NO]⋅ (N-heterocyclic carbene nitric oxide radical) compounds. We have accessed a suite of compounds, comprised of [NHC-NO]+ , [NHC-NO]- , [NHC-NOH]0 , and [NHC-NHOH]+ species. In particular, [NHC-NO]- was isolated as potassium and lithium ion adducts. Most interestingly, a monomeric potassium [NHC-NO]- compound was isolated with the assistance of 18-crown-6, which is the first instance of a monomeric alkali N-oxyl compound to the best of our knowledge. Our results demonstrate that [NHC-NO]⋅ exhibits redox behavior broadly similar to metal nitrosyl complexes, which opens up more possibilities for utilizing NHCs to build on the known reactivity of metal complexes.

Characterization by ENDOR Spectroscopy of the Iron-Alkyl Bond in a Synthetic Counterpart of Organometallic Intermediates in Radical SAM Enzymes.

Members of the radical S-adenosyl-l-methionine (SAM) enzyme superfamily initiate a broad spectrum of radical transformations through reductive cleavage of SAM by a [4Fe-4S]1+ cluster it coordinates to generate the reactive 5'-deoxyadenosyl radical (5'-dAdo•). However, 5'-dAdo• is not directly liberated for reaction and instead binds to the unique Fe of the cluster to create the catalytically competent S = 1/2 organometallic intermediate Ω. An alternative mode of reductive SAM cleavage, especially seen photochemically, instead liberates CH3•, which forms the analogous S = 1/2 organometallic intermediate with an Fe-CH3 bond, ΩM. The presence of a covalent Fe-C bond in both structures was established by the ENDOR observation of 13C and 1H hyperfine couplings to the alkyl groups that show isotropic components indicative of Fe-C bond covalency. The synthetic [Fe4S4]3+-CH3 cluster, M-CH3, is a crystallographically characterized analogue to ΩM that exhibits the same [Fe4S4]3+ cluster state as Ω and ΩM, and thus an analysis of its spectroscopic properties─and comparison with those of Ω and ΩM─can be grounded in its crystal structure. We report cryogenic (2 K) EPR and 13C/1/2H ENDOR measurements on isotopically labeled M-CH3. At low temperatures, the complex exhibits EPR spectra from two distinct conformers/subpopulations. ENDOR shows that at 2 K, one contains a static methyl, but in the other, the methyl undergoes rapid tunneling/hopping rotation about the Fe-CH3 bond. This generates an averaged hyperfine coupling tensor whose analysis requires an extended treatment of rotational averaging. The methyl group 13C/1/2H hyperfine couplings are compared with the corresponding values for Ω and ΩM.

Dialogue with a conversational agent promotes children's story comprehension via enhancing engagement.

Dialogic reading, when children are read a storybook and engaged in relevant conversation, is a powerful strategy for fostering language development. With the development of artificial intelligence, conversational agents can engage children in elements of dialogic reading. This study examined whether a conversational agent can improve children's story comprehension and engagement, as compared to an adult reading partner. Using a 2 (dialogic reading or non-dialogic reading) × 2 (agent or human) factorial design, a total of 117 three- to six-year-olds (50% Female, 37% White, 31% Asian, 21% multi-ethnic) were randomly assigned into one of the four conditions. Results revealed that a conversational agent can replicate the benefits of dialogic reading with a human partner by enhancing children's narrative-relevant vocalizations, reducing irrelevant vocalizations, and improving story comprehension.

Is reading prosody related to reading comprehension? A meta-analysis.

We examined the relation between reading prosody and reading comprehension, using a systematic review and meta-analysis to estimate the strength of the relation and to understand whether the strength of the relation varies by prosody feature (adult-like contour, F0 sentence-final declination, grammatical pauses, ungrammatical pauses, prosody scale), students' developmental phase of reading skill as examined by grade level, and orthographic depth. A total of 35 studies (K = 98; N = 9,349; Grades 1-9, 8 languages) met inclusion criteria. Overall a moderate relation (.51) was found between reading prosody and reading comprehension. Furthermore, the strength varied by prosody feature such that the relation was stronger for prosody rating scale than for pitch indicators such as adult-like contour and F0 sentence-final declination. However, grade and orthographic depth were not significant moderators. These results suggest that the relation between reading prosody and reading comprehension is not unitary and should consider specific aspects of reading prosody.

Expanding the Direct and Indirect Effects Model of Writing (DIEW): Reading-Writing Relations, and Dynamic Relations As a Function of Measurement/Dimensions of Written Composition.

Within the context of the Direct and Indirect Effects model of Writing, we examined a dynamic relations hypothesis, which contends that the relations of component skills, including reading comprehension, to written composition vary as a function of dimensions of written composition. Specifically, we investigated (a) whether higher order cognitive skills (i.e., inference, perspective taking, and monitoring) are differentially related to three dimensions of written composition-writing quality, writing productivity, and correctness in writing; (b) whether reading comprehension is differentially related to the three dimensions of written composition after accounting for oral language, cognition, and transcription skills; and whether reading comprehension mediates the relations of discourse oral language and lexical literacy to the three dimensions of written composition; and (c) whether total effects of oral language, cognition, transcription, and reading comprehension vary for the three dimensions of written composition. Structural equation model results from 350 English-speaking second graders showed that higher order cognitive skills were differentially related to the three dimensions of written composition. Reading comprehension was related only to writing quality, but not to writing productivity or correctness in writing; and reading comprehension differentially mediated the relations of discourse oral language and lexical literacy to writing quality. Total effects of language, cognition, transcription, and reading comprehension varied largely for the three dimensions of written composition. These results support the dynamic relation hypothesis, role of reading in writing, and the importance of accounting for dimensions of written composition in a theoretical model of writing.

Crosslinguistic Transfer of Higher Order Cognitive Skills and Their Roles in Writing for English-Spanish Dual Language Learners.

We investigated the dimensionality and relations between L1 and L2 writing skills in narrative and informational genres, and higher order cognitive skills-inference, perspective taking, and comprehension monitoring-for Spanish-English dual language learners in primary grades. Dimensions of written composition and higher order cognitive skills were examined, comparing nine alternative models. Data from 317 dual language learners in Grades 1 and 2 were used in confirmatory factor analysis and structural equation modeling. For the dimensionality of written composition, a unidimensional model, where writing was characterized as a single underlying construct across languages (Spanish and English) and genres (narrative & opinion), fit the data best. With regard to the dimensionality of higher order cognitive skills, data supported a bifactor model with (a) a general factor that captures common variance across languages and across inference, perspective taking, and comprehension monitoring skills and (b) specific factors by language (Spanish and English). The higher order cognition general factor was fairly strongly related to writing quality (.59), and the relation remained even after accounting for sex, poverty status, grade level, English learner status, school, and biliterate status. These relations were similar for students in English immersion program and Spanish-English dual immersion programs. These results indicate potential cross-language transfer of higher order cognitive skills, and the roles of higher order cognitions in written composition for Spanish-English dual language learners.

The Effects of Antioxidants on the Changes in Volatile Compounds in Heated Welsh Onions (Allium fistulosum L.) during Storage.

Welsh onion (Allium fistulosum L.) is usually used to enhance the flavor characteristics of various foods. Volatile compounds in Welsh onions, including sulfur-containing compounds, may vary during heat process and storage. Accordingly, the changes in the volatile compounds in Welsh onions, subjected to heat and antioxidant (ascorbic acid and glutathione) treatments during storage, are investigated in the present study. The majority of sulfur-containing compounds in Welsh onions showed significant differences between the untreated Welsh onions and heated Welsh onions. During the heating of the Welsh onions, some sulfur-containing compounds, such as 2-methylthiirane, 1-(methyldisulfanyl)prop-1-ene, 1-[[(E)-prop-1-enyl]disulfanyl]propane, 1-(propyltrisulfanyl)propane, 1-[[(E)-prop-1-enyl]trisulfanyl]propane, and (methyltetrasulfanyl)methane, showed significant differences between the untreated and heated Welsh onions (p < 0.05). In addition, partial least square discriminant analysis (PLS-DA) was applied to discriminate the heated Welsh onion samples added with different antioxidants. The heated Welsh onion samples added with ascorbic acid was mainly associated with 2-phenylacetaldehyde, acetic acid, methylsulfanylmethane, prop-2-ene-1-thiol, undecan-2-one, and (2E,4E)-deca-2,4-dienal. Moreover, the key volatile compounds in the heated Welsh onion samples added with glutathione were 3-ethylthiophene, 1-(methyldisulfanyl)-1-methylsulfanylpropane, 1-methylsulfanylpentane, 2-prop-2-enylsulfanylpropane, and 1-propan-2-ylsulfanylbutane.

Evaluation of Caspase-3 and Ki-67 expression in squamous cell hyperplasia of the stomach induced by Platycodi radix water extract in Sprague-Dawley rats.

Platycodi radix is widely used in traditional herbal medicine for the treatment of bronchitis, asthma, pulmonary tuberculosis, hypertension, hyperlipidemia, and diabetes. This study aimed to investigate cell proliferation (Ki-67) and apoptosis (Caspase-3) potential in squamous cell hyperplasia of the stomach induced by a Platycodi radix water extract in a subchronic toxicity study. One hundred formalin-fixed, paraffin-embedded stomach tissues of rats treated with Platycodi radix at doses of 0, 500, 1,000, and 3,000 mg/kg body weight/day were used for the analysis. They were conventionally stained using hematoxylin and eosin (H&E) and immunohistochemically (IHC) stained using caspase-3 and Ki-67 antibodies. The incidence of squamous cell hyperplasia was significantly increased in the 3,000 mg/kg b.w./day treatment group in both sexes (p<0.01). However, the hyperplastic change was completely repaired after 4 weeks of recovery period. Ki-67 expression was similar in all groups, with no statistically significant differences among the groups. Caspase-3 expression was significantly increased in both sexes in the 3,000 mg/kg b.w./day treatment group (p<0.01), compared with the vehicle control groups, and then reduced to normal levels in the recovery groups in both sexes. In conclusion, this study showed that squamous cell hyperplasia induced by the Platycodi radix water extract in the limiting ridge of the stomach is not considered to be abnormal proliferative change; as a result, squamous cell hyperplasia is considered to be a non-adverse effect when induced by the oral administration of the Platycodi radix water extract once daily for 13 weeks in rats.

Do Written Language Bursts Mediate the Relations of Language, Cognitive, and Transcription Skills to Writing Quality?

In this study, we examined burst length and its relation with working memory, attentional control, transcription skills, discourse oral language, and writing quality, using data from English-speaking children in Grade 2 (N = 177; M age = 7.19). Results from structural equation modeling showed that burst length was related to writing quality after accounting for transcription skills, discourse oral language, working memory, and attentional control. Burst length completely mediated the relations of attentional control and handwriting fluency to writing quality whereas it partially mediated the relations of working memory and spelling to writing quality. Discourse oral language had a suppression effect on burst length but was positively and independently related to writing quality. Working memory had an indirect relation to burst length via transcription skills whereas attentional control had a direct and indirect relation. These results suggest roles of domain-general cognitions and transcription skills in burst length, and reveal the nature of their relations to writing quality.

The Elusive Mononitrosylated [Fe4 S4 ] Cluster in Three Redox States.

Iron-sulfur clusters are well-established targets in biological nitric oxide (NO) chemistry, but the key intermediate in these processes-a mononitrosylated [Fe4 S4 ] cluster-has not been fully characterized in a protein or a synthetic model thereof. Here, we report the synthesis of a three-member redox series of isostructural mononitrosylated [Fe4 S4 ] clusters. Mononitrosylation was achieved by binding NO to a 3 : 1 site-differentiated [Fe4 S4 ]+ cluster; subsequent oxidation and reduction afforded the other members of the series. All three clusters feature a local high-spin Fe3+ center antiferromagnetically coupled to 3 [NO]- . The observation of an anionic NO ligand suggests that NO binding is accompanied by formal electron transfer from the cluster to NO. Preliminary reactivity studies with the monocationic cluster demonstrate that exposure to excess NO degrades the cluster, supporting the intermediacy of mononitrosylated intermediates in NO sensing/signaling.

Highly Stable 1,2-Dicarbonyl Radical Cations Derived from N-Heterocyclic Carbenes.

Stable organic radicals have been of great academic interest not only in the context of fundamental understanding of reactive intermediates but also because of their numerous applications as functional materials. Apart from the early examples of triphenylmethyl and TEMPO derivatives, reports on air- and water-stable organic radicals are scarce, and their development remains a challenge. Herein, we present the design and synthesis of a novel organic radical based on a 1,2-dicarbonyl scaffold supported by N-heterocyclic carbenes (NHCs). The presented radical cations exhibit remarkable stability toward various harsh conditions, such as the presence of reactive chemicals (reductants, oxidants, strong acids, and bases) or high temperatures, by far exceeding the stability of triphenylmethyl and TEMPO radicals. In addition, physiological conditions including aqueous buffer and blood serum are tolerated. The steric and electronic stabilization provided by the two NHC moieties enabled the successful design of the highly stable radical.

Azelaic Acid Promotes Caenorhabditis elegans Longevity at Low Temperature Via an Increase in Fatty Acid Desaturation.

PURPOSE: Azelaic acid (AzA) is a dicarboxylic acid naturally occurring in various grains having anti-inflammatory and anti-oxidation properties. Recently, AzA is shown to reduce high-fat diet-induced adiposity in animals. However, its physiological role in lipid metabolism and aging in various environmental stresses is unknown. METHODS AND RESULTS: Using C. elegans as an invertebrate animal model, we demonstrate that AzA suppresses fat accumulation with no effect on lifespan at normal temperatures. Moreover, AzA promotes lifespan at low temperatures by elevation of unsaturated long-chain fatty acids and expression of genes in fatty acid desaturation. We further find that genes encoding fatty acid desaturases such as fat-1, fat-5, fat-6, and fat-7 are crucial for the lifespan-extending effect of AzA at low temperature. CONCLUSIONS: Taken together, our results suggest that AzA promotes adaption to low temperature in C. elegans via shifting fatty acid profile to unsaturated long-chain fatty acids.

Deeper Understanding of Mononuclear Manganese(IV)-Oxo Binding Brønsted and Lewis Acids and the Manganese(IV)-Hydroxide Complex.

Binding of Lewis acidic metal ions and Brønsted acid at the metal-oxo group of high-valent metal-oxo complexes enhances their reactivities significantly in oxidation reactions. However, such a binding of Lewis acids and proton at the metal-oxo group has been questioned in several cases and remains to be clarified. Herein, we report the synthesis, characterization, and reactivity studies of a mononuclear manganese(IV)-oxo complex binding triflic acid, {[(dpaq)MnIV(O)]-HOTf}+ (1-HOTf). First, 1-HOTf was synthesized and characterized using various spectroscopic techniques, including resonance Raman (rRaman) and X-ray absorption spectroscopy/extended X-ray absorption fine structure. In particular, in rRaman experiments, we observed a linear correlation between the Mn-O stretching frequencies of 1-HOTf (e.g., νMn-O at ∼793 cm-1) and 1-Mn+ (Mn+ = Ca2+, Zn2+, Lu3+, Al3+, or Sc3+) and the Lewis acidities of H+ and Mn+ ions, suggesting that H+ and Mn+ bind at the metal-oxo moiety of [(dpaq)MnIV(O)]+. Interestingly, a single-crystal structure of 1-HOTf was obtained by X-ray diffraction analysis, but the structure was not an expected Mn(IV)-oxo complex but a Mn(IV)-hydroxide complex, [(dpaq)MnIV(OH)](OTf)2 (4), with a Mn-O bond distance of 1.8043(19) Å and a Mn-O stretch at 660 cm-1. More interestingly, 4 reverted to 1-HOTf upon dissolution, demonstrating that 1-HOTf and 4 are interconvertible depending on the physical states, such as 1-HOTf in solution and 4 in isolated solid. The reactivity of 1-HOTf was investigated in hydrogen atom transfer (HAT) and oxygen atom transfer (OAT) reactions and then compared with those of 1-Mn+ complexes; an interesting correlation between the Mn-O stretching frequencies of 1-HOTf and 1-Mn+ and their reactivities in the OAT and HAT reactions is reported for the first time in this study.