Sequential Pathway Research Articles

Multiple insular-prefrontal pathways underlie perception to execution during response inhibition in humans

Inhibiting prepotent responses in the face of external stop signals requires complex information processing, from perceptual to control processing. However, the cerebral circuits underlying these processes remain elusive. In this study, we used neuroimaging and brain stimulation to investigate the interplay between human brain regions during response inhibition at the whole-brain level. Magnetic resonance imaging suggested a sequential four-step processing pathway: initiating from the primary visual cortex (V1), progressing to the dorsal anterior insula (daINS), then involving two essential regions in the inferior frontal cortex (IFC), namely the ventral posterior IFC (vpIFC) and anterior IFC (aIFC), and reaching the basal ganglia (BG)/primary motor cortex (M1). A combination of ultrasound stimulation and time-resolved magnetic stimulation elucidated the causal influence of daINS on vpIFC and the unidirectional dependence of aIFC on vpIFC. These results unveil asymmetric pathways in the insular-prefrontal cortex and outline the macroscopic cerebral circuits for response inhibition: V1→daINS→vpIFC/aIFC→BG/M1.

Understanding educational inequalities in sports participation through structurally based resources and individual agency - a sequential mediation analysis.

Educational inequalities in sports participation remain a public health issue in the Netherlands. Combining structurally based resources from Pierre Bourdieu's theory of capital with Amartya Sen's conceptualization of individual agency may offer new insights into the complex mechanisms that drive these inequalities. Specifically, we posited that the way individuals are able to exercise their agency within the structurally based economic, social, and cultural resources they have access to may help explain educational inequalities in sports participation.Data from two waves of the GLOBE study (2014, 2021) were used to test whether two sequential mediators, structurally based resources followed by individual agency, help explain the relationship between educational level and sports participation. Adults aged 25 and older residing in Eindhoven, the Netherlands self-reported highest attained educational level, structurally based resources (economic, social, and embodied cultural capital), individual agency (self-control, perceived choice, and reflexivity), and sports participation. A sequential mediation analysis using structural equation modelling was used to test the direct effect of education on sports participation, the sequential indirect effect through both mediators, and partial indirect effects through each mediator individually.Educational level was positively associated with sports participation. The hypothesized sequential mediation pathway was not supported; educational level was positively associated with structurally based resources and structurally based resources were positively associated with individual agency, but individual agency was not related to sports participation. Though not through individual agency, structurally based resources helped explain educational inequalities in sports participation.Having access to more economic, social, and cultural resources may empower individuals by increasing their agency. This increased agency was not associated with sports participation, which could be because sports participation is not universally valued as a goal. The conceptualization and operationalization of individual agency in the context of sports participation warrants more research. We found that structurally based resources helped explain a substantial portion of educational inequalities in sport, so we propose that policies alleviating more than just economic barriers to sports participation, but also social and cultural barriers, may help reduce educational inequalities in sports participation in the Netherlands.

Kinetics and Mechanism of PPh3/Ni-Catalyzed, Zn-Mediated, Aryl Chloride Homocoupling: Antagonistic Effects of ZnCl2/Cl.

The Ni/PPh3-catalyzed homocoupling of aryl chlorides in DMF using Zn as the stochiometric reducing agent is one of a general class of Ni-catalyzed processes, where the mechanism has been a matter of long-standing debate. This study re-evaluates prior conclusions and insights. NMR spectroscopy is used to identify [(PPh3)2NiII(Ar)Cl] as a key intermediate and to explore the indirect roles of using Zn as the reductant. The [ZnCl2] coproduct is responsible for several features, including a sequential transmetalation pathway involving [ArZnCl]. [ZnCl2] also abstracts halide from [(PPh3)2NiCl2] to generate [NiIICl(DMF)5]+[ZnCl3(DMF)]-, and in doing so, affects the NiII + Ni0 ↔ 2 NiI speciation. [ZnCl2] thus acts as an accelerator and inhibitor, resulting in mildly sigmoidal reaction profiles. When the [ZnCl2] concentration becomes too high or the phosphine ligand concentration too low, catalysis stalls. Turnover is restored by the addition of further phosphine ligand, or chloride ion. In the presence of an exogenous chloride ion, turnover is rapid, again proceeding via [(PPh3)2NiII(Ar)Cl] but via dinuclear metathesis. The generation of [ZnCl3(DMF)]- results in mutually antagonistic effects between [ZnCl2] and [Cl]- such that turnover proceeds via one mechanism or the other, depending on which species is in excess. The intermediacy of [ArZnCl] suggests a solution to the long-standing anomaly that many other reductants were found to be much less effective than Zn in inducing turnover of Ni/PPh3 catalyzed aryl chloride homocoupling in DMF. The use of DMAc as a solvent in place of DMF inhibits stalling through the steric inhibition of mixed metalate generation.

Identifying bound compounds in non-extractable residues of pesticides in soil by 4-pool kinetic analysis

This study explores the feasibility of identifying bound compounds in non-extractable residues (NERs) of pesticides in soil by 4-pool kinetic analysis. The 4-pools refer to parent compound, metabolites, NERs, and CO2 in 14C-labeled pesticide soil degradation studies. We discovered the following two characteristic 4-pool kinetic behaviors of formation of NERs: (1) if parent compound is bound as NERs, the metabolites (m(t) in % applied radioactivity (AR)) kinetically drive the evolution of CO2 only; and (2) if a metabolite (x) in a sequential degradation pathway is bound as NERs, m(t) is split into m1(t) and m2(t) at the metabolite (x) that is bound as NERs, which kinetically drive the formation of NERs and evolution of CO2 respectively. We developed two (i.e., Parent➔NER and metabolite➔NER) 4-pool models to capture the kinetic behaviors respectively. By fitting the models to a set of 4-pool data, we not only determine whether NERs form from parent compound or metabolites but also identify the bound metabolite (x) by resolving the metabolites into M1(t) and M2(t) (i.e., the variables used to simulate m1(t) and m2(t)) and then matching m1(t) (i.e., the sum of the bound metabolite (x) and its metabolite precursors) with M1(t). By applying the models to 14C-labeled parent compound-dosed studies and then sequentially to metabolite-dosed studies for 7 pesticides with ≥70 % AR NERs, we identified the bound compounds, which have the moieties known to be responsible for NERs, are bound as NERs instantaneously when dosed into soil, and account for pH dependency of NER formation.

Catalytic hydrodehalogenation of iodinated contrast agents in drinking water: A kinetic study

The occurrence of iodinated contrast media (ICM) in water bodies represents a significant threat for public health due to their strong biochemical stability and recalcitrance to conventional water treatment systems. In this work, the feasibility of catalytic hydrodehalogenation (HDH) for the degradation of a representative group of ICMs (iohexol (IHX), iopromide (IPR), iopamidol (IPM) and diatrizoic acid (DIA)) is investigated. Complete degradation and deiodination of the isolated ICMs (1.6·10−2 mmol L−1) was achieved in less than 30 min in the presence of 0.25 g L−1 of different precious metal catalysts (Pd/Al2O3, Rh/Al2O3 and Pt/Al2O3) under ambient conditions, closing iodine balance by >95 %. Based on the identified reaction intermediates and final products, reaction mechanisms were accordingly proposed. A sequential reaction pathway was proposed for DIA removal, while reaction mechanisms encompassing both sequential and concerted reaction steps were proposed for the non-ionic ICMs (IHX, IPR, and IPM). Subsequent kinetic models, which successfully described experimental data, were developed from the elucidated reaction mechanisms, considering all species involved in the reaction. The versatility of the process was finally demonstrated in the treatment of real aqueous matrices (surface water and tap water) spiked with the ICMs mixture, except in the case of Pt/Al2O3 which suffered deactivation due to surface poisoning by halides. For this catalyst, kinetic constants ranged from 0.31 to 0.22 min−1 in deionized water, and from 0.04 to 0.08 min−1 in surface water as the reaction matrix. Among the tested catalysts, Pd/Al2O3 showed the highest activity and stability for the removal of ICMs.

On-surface synthesis of porous graphene nanoribbons mediated by phenyl migration

Advancements in the on-surface synthesis of atomically precise graphene nanostructures are propelled by the introduction of innovative precursor designs and reaction types. Until now, the latter has been confined to cross-coupling and cyclization reactions that involve the cleavage of specific atoms or groups. In this article, we elucidate how the migration of phenyl substituents attached to graphene nanoribbons can be harnessed to generate arrays of [18]-annulene pores at the edges of the nanostructures. This sequential pathway is revealed through a comprehensive study employing bond-resolved scanning tunneling microscopy and ab-initio computational techniques. The yield of pore formation is maximized by anchoring the graphene nanoribbons at steps of vicinal surfaces, underscoring the potential of these substrates to guide reaction paths. Our study introduces a new reaction to the on-surface synthesis toolbox along with a sequential route, altogether enabling the extension of this strategy towards the formation of other porous nanostructures.

A test of moderated serial mediation model of compulsive buying among Gen Z fandoms moderated by trash talking

Purpose The study aims to identify the factors that influence young consumers’ compulsive buying, particularly Gen Z consumers who exhibit fandom qualities such as sharing the same interests and being willing to collaborate with others. This study investigates the direct and indirect impact of brand love and brand addiction on the relationship between social media addiction and compulsive buying. Design/methodology/approach The study collected data from 338 Gen Z fandoms. The snowball sampling approach is used to determine and collect data from the sample. To test for hypotheses, the study used the PROCESS macro with bootstrapping techniques to explore the direct and indirect relationships, as well as the moderated serial mediation model in this study. Findings The study found that social media addiction influences compulsive buying via the hierarchical linkages between brand love and brand addiction. Trash talking functions as a stimulant, amplifying the effect of brand addiction on compulsive buying. Research limitations/implications The data were collected from young Thai consumers; thus, the generalizability aspect of the research is limited and needs to be tested in different countries and cultures. Originality/value This research provides several key contributions to the understanding of compulsive buying behavior among Gen Z, particularly within the context of a developing country. By integrating the stimulus-organism-response framework and psychological theories, this study offers a nuanced understanding of how social media addiction influences emotional and behavioral outcomes. Previous studies have primarily focused on these variables in isolation. The study fills this gap by demonstrating the sequential pathway through which social media addiction translates into compulsive buying behavior via brand love and brand addiction.

Transition Approaches towards Positive Energy Districts: A Systematic Review

The positive energy district (PED) concept is attracting growing research interest; however, the need for practical approaches to facilitate their implementation remains crucial. This study, framed in the COST Action ‘Positive Energy Districts European Network’, offers a comprehensive review of the roadmaps, pathways, and guidelines—namely ‘PED-Transition Approaches’—currently available to support the implementation of district-scale innovative models, thereby advancing energy transitions and enhancing livability at the city level. The review involved a systematic search and web scraping of documents, including scientific and grey literature, as well as EU-funded projects’ reports. The studies were identified according to multiple filters and eligibility criteria, then categorised in a structured repository using a multidimensional matrix, and finally examined following three-levels of detail (i.e., bibliometric study) overview and in-depth analysis. The findings reflect the main characteristics, gaps, and challenges in PED implementation by underlying the growing need for effective step-by-step, user-centric, and context-based transition approaches. In conclusion, the research, building on an extensive literature of multiple inspirational methodologies and their associated use cases, is a strong basis to develop sequential pathways to facilitate PED implementation among key stakeholders in a short–medium-term perspective towards a climate-neutral city vision.

Impacts of graphene oxide contamination on a food web: Threats to somatic and reproductive health of organisms

Contamination of aquatic food webs with nanomaterials poses a significant ecological and human health challenge. Ingestion of nanomaterials alongside food disrupts digestion and impairs physiological processes, with potential consequences for organism fitness and survival. Complex interactions between nanomaterials and biota further exacerbate the issue, influencing life-history strategies and ecosystem dynamics. Accumulation of nanomaterials within autotrophic and detritus-based food webs raises concerns about biomagnification, especially for top-level consumers and seafood-dependent human populations. Understanding the extent and impact of nanomaterial contamination on aquatic biota is crucial for effective mitigation strategies. To address this challenge, we conducted a comprehensive study evaluating the bioaccumulation effects of graphene oxide (GO), a commonly used nanomaterial, within an aquatic food chain. Using a gnotobiotic freshwater microcosm, we investigated the effects of micro- and nano-scale GO sheets on key organisms: green algae (Chlorella vulgaris), brine shrimp (Artemia salina), and zebrafish (Danio rerio). Two feeding regimes, direct ingestion and trophic transfer, were employed to assess GO uptake and transfer within the food web. Direct exposure involved individual organisms being exposed to either nano- or micro-scale GO sheets, while trophic transfer involved a sequential exposure pathway: algae exposed to GO sheets, artemias feeding on the algae, and zebrafish consuming the artemias. Our study provides critical insights into nanomaterial contamination in aquatic ecosystems. Physicochemical properties of GO sheets, including ζ-potential and dispersion, were influenced by salt culture media, resulting in aggregation under salt conditions. Microscopic imaging confirmed the bioaccumulation of GO sheets within organisms, indicating prolonged exposure and potential long-term effects. Notably, biodistribution analysis in zebrafish demonstrated the penetration of nano-sized GO into the intestinal wall, signifying direct interaction with vital organs. Exposure to GO resulted in increased zebrafish mortality and impaired reproductive performance, particularly through trophic transfer. These findings emphasize the urgent need to address nanomaterial contamination in aquatic food webs to protect ecosystem components and human consumers. Our study highlights the importance of developing effective mitigation strategies to preserve the integrity of aquatic ecosystems, ensure resource sustainability, and safeguard human well-being. In conclusion, our study provides crucial insights into the impact of nanomaterial pollution on aquatic biota. By recognizing the challenges posed by nanomaterial contamination and implementing targeted interventions, we can mitigate the adverse effects, preserving the integrity of aquatic ecosystems and safeguarding human health.

Temperamental Shyness, Peer Competence, and Loneliness in Middle Childhood: The Role of Positive Emotion

Guided by the conceptual frameworks of social withdrawal (Rubin, K. H., & Chronis-Tuscano, A. (2021). Perspectives on social withdrawal in childhood: Past, present, and prospects. Child Development Perspectives, 15(3), 160–167.) and emotion socialization (Eisenberg, N., Cumberland, A., & Spinrad, T. L. (1998). Parental socialization of emotion. Psychological Inquiry, 9, 241–273.; Morris, (A) S., Criss, M. M., Silk, J. S., & Houltberg, (B) J. (2017). The impact of parenting on emotion regulation during childhood and adolescence. Child Development Perspectives, 11(4), 233–238.), the current study examined multifaceted relations among temperamental shyness, peer competence, and loneliness and focused on the role of socializing and expressing positive emotion in middle childhood. Participants included 1,364 families, among whom mothers reported children’s temperament when children were 4.5 years old. Mothers and alternative caregivers (usually fathers) independently rated family expressiveness when children were 8–9 years old. Mothers rated their children’s peer competence, and children’s positive affect with peers were observed when children were ages 8–9 and 10–11. Children self-rated their loneliness levels at ages 10–11. A path model revealed a moderated mediation effect, such that family positive expressiveness moderated the sequential mediation pathway from child temperamental shyness through child peer competence at ages 8–9 and positive affect with peers at ages 10–11 to loneliness at ages 10–11. This sequential mediation was significant only under low but not high levels of family positive expressiveness. Findings support the importance of socializing positive emotion in the context of temperamental shyness and have implications for family-based intervention strategies aimed at children exhibiting high temperamental shyness.

Early screening for chronic liver disease: impact of a FIB-4 first integrated care pathway to identify patients with significant fibrosis

Liver fibrosis is often undetected whereas it is the determinant of liver-related mortality. We evaluate a pathway based on the systematic calculation of FIB-4 to screen for advanced hepatic fibrosis. Systematic calculation of FIB-4 was implemented in the centralized laboratory of a French University Hospital in 4 pilot departments. If ≥ 2.67, the FIB-4 result was returned to the prescribers, for patients between 18 and 70 years of age, with an incentive to measure liver stiffness by vibration controlled transient elastography. During a 2-years period, a FIB-4 was calculated in 2963 patients and 135 were ≥ 2.67 (4.6%). After exclusion of patients with a known cause of elevated FIB-4, 47 patients (34.8%) were eligible for elastography. Forty patients underwent elastography, but only 15% (7/47) at the spontaneous request of the referring physician. Fifteen patients were identified with significant fibrosis, among which 8 attended the scheduled specialist consultation, all with a confirmed diagnosis of cirrhosis. A sequential pathway based on the systematic calculation of FIB-4 enables the identification of patients with significant unknown liver fibrosis, allowing to refer them to specialized care. Raising awareness is essential to improve the care pathway.

Intracellular Construction of Organelle-like Compartments Facilitates Metabolic Flux in Escherichia coli.

The formation of well-designed synthetic compartments or membraneless organelles for applications in synthetic biology and cellular engineering has aroused enormous interest. However, establishing stable and robust intracellular compartments in bacteria remains a challenge. Here, we use the structured DIX domains derived from Wnt signaling pathway components, more specifically, Dvl2 and Axin1, as building blocks to generate intracellular synthetic compartments in Escherichia coli. Moreover, the aggregation behaviors and physical properties of the DIX-based compartments can be tailored by genetically embedding a specific dimeric domain into the DIX domains. Then, a pair of interacting motifs, consisting of the aforementioned dimeric domain and its corresponding binding ligand, was incorporated to modify the client recruitment pattern of the synthetic compartments. As a proof of concept, the human milk oligosaccharide lacto-N-tetraose (LNT) biosynthesis pathway was selected as a model metabolic pathway. The fermentation results demonstrated that the co-compartmentalization of sequential pathway enzymes into intracellular compartments created by DIX domain, or by the DIX domain in conjunction with interacting motifs, prominently enhanced the metabolic flux and increased LNT production. These synthetic protein compartments may provide a feasible and effective tool to develop versatile organelle-like compartments in bacteria for applications in cellular engineering and synthetic biology.

The Effects of Fathers’ Family-of-Origin Experiences on Co-parenting: The Mediating Role of Marital Conflict and Psychological Well-Being

Objectives: The purpose of this research was to investigate how fathers’ individual characteristics and the quality of their marital relationships influence co-parenting. Previous research on fathers’ perceptions of co-parenting has been relatively under-explored. Therefore, this study aimed to explore the direct impact of fathers’ family-of-origin experiences on co-parenting and to examine the indirect effects mediated by marital conflict and fathers’ psychological well-being.Methods: Data were collected from a sample of 250 fathers with preschool-aged children (aged 3 to 5). Fathers completed comprehensive questionnaires assessing their family-of-origin experiences, levels of marital conflict, psychological well-being, and perceptions of co-parenting.Results: The findings revealed several significant relationships. Firstly, fathers’ family-of-origin experiences had a notable direct impact on co-parenting. Secondly, these experiences indirectly influenced co-parenting through the pathway of marital conflict. Thirdly, fathers’ family-of-origin experiences indirectly affected co-parenting through their psychological well-being. Additionally, fathers’ family-of-origin experiences had an indirect impact on co-parenting through sequential pathways involving marital conflict and psychological well-being. Specifically, stronger positive experiences from fathers' family-of-origin were associated with reduced levels of perceived marital conflict, leading to enhanced psychological well-being and more positive perceptions of co-parenting.Conclusion: This study enhances our understanding of the factors influencing co-parenting from the perspective of fathers. The results highlight the importance of interventions aimed at improving fathers’ perceptions of co-parenting, emphasizing reflection on family-of-origin experiences, resolution of marital conflicts, and enhancement of psychological well-being through targeted interventions. By addressing these areas, interventions may effectively promote positive co-parenting dynamics within families and contribute to overall family well-being.

Formation of acetonitrile and ethylene from activation of ethane over cobalt-exchanged aluminosilicates: Active sites and reaction pathways

Cobalt-exchanged ZSM-5 catalyzes the ammoxidation of ethane (2 C2H6 + 3 O2 + 2 NH3 → 2 CH3CN + 6 H2O), yet the active form of cobalt, the role of the Brønsted acidic zeolite, and the reaction pathways remain elusive. Comparisons of rates and selectivities of reactions at distinctive cobalt sites (Co2+ at Al pair sites (CoZ2), Co3O4, cobalt phyllosilicate, and cobalt aluminate) suggest sites that form from CoZ2 provide the greatest rates and selectivities for CH3CN and C2H4 formation. Significantly, we revealed a large fraction of CH3CN appears to form directly through a trimolecular reaction at cobalt ions without desorption of intermediates. In parallel, a more conventional sequential pathway dehydrogenates C2H6, aminates C2H4, and oxidatively dehydrogenates C2H5NH2 to produce CH3CN. Combined rate measurements with temperature programmed reactions and in situ infrared spectra demonstrate that O2-derived intermediates at cobalt ions initiate both reaction sequences by abstracting H-atom from C2H6.

Alumanyl Reduction, Reductive Coupling and C-H Isomerization of Organic Nitriles.

The behavior of the potassium alumanyl, [{SiNDipp}AlK]2 ({SiNDipp} = {CH2SiMe2N(Dipp)}2; Dipp = 2,6-i-Pr2C6H3), toward organic nitriles has been investigated. In common with earlier studies of the reactivity of charge neutral Al(I) species with multiply bonded small molecules, it is suggested that the initial step in all the reactions involves [2 + 1] cycloaddition and the generation of an [η2-C=N-Al] alumina azacyclopropane unit. In the cases of o- and m-tolyl-substituted aryl nitriles, this species is too kinetically labile to allow its isolation and undergoes C-C coupling via immediate Al-C/C≡N insertion to yield the alumina diazabutadiene derivatives. In contrast, the increased steric profile of alkyl nitriles imposes a marked influence on the nature of the products formed. Consistent with the proposed sequential pathway, reaction of [{SiNDipp}AlK]2 with t-BuCN provides an isolable alumina cyclopropane species that is kinetically resistant to onward reaction with a further nitrile equivalent. While reduction in the alkyl nitrile steric demands by use of i-PrCN again facilitates C-C bond formation, the crowding of the Al center by the resultant alumina-diazabutadienediide moiety appears to be beyond the limit of kinetic viability, resulting in an unusual 2-fold C-H to N-H isomerization from one of the C-iso-propyl substituents and the isolation of a 1-alumina-2,5-diazabutadiene structure.

From the Workroom to the Bedroom: Work-to-Home Spillover as a Mechanism Linking Work Characteristics to Sleep Health.

Work may influence the home domain and subsequently impact employee sleep. Past work found that negative spillover mediated the relationship between perceived unfairness about work and insomnia symptoms across 20 years. As an extension of past work, this study investigated whether negative spillover and positive spillover mediate the relationship between job demands (perceived unfairness, job discrimination) and job resources (coworker and supervisor support) on multidimensional sleep health. Two waves of survey data from a subset of full-time workers were obtained from the Midlife in the United States Study approximately 10 years apart. A sleep health composite captured irregularity, dissatisfaction, nap frequency, inefficiency, and suboptimal sleep duration (higher=more sleep health problems). PROCESS Macro evaluated cross-sectional (T1) and sequential (T1 exposureaT1 mediatoraT2 outcome) mediation pathways, adjusting for sociodemographic characteristics, physical health, neuroticism, and work hours. Both cross-sectionally and prospectively, higher negative spillover mediated the association of higher unfairness with more sleep health problems, and the association between higher discrimination and more sleep health problems. There was no support for positive spillover as a mediator between job resources and sleep health cross-sectionally or prospectively. Findings suggest that organizations should reduce the amount of negative spillover by limiting instances of unfairness and discrimination at work to promote specific aspects of employee sleep health such as sleep irregularity, dissatisfaction, efficiency, and nap frequency.

Character-Audience Racial Matching, Prescription Opioid Misuse Experience, and the Effectiveness of Anti-Prescription Opioid Messages: The Mediating Roles of Identification and Perceived Severity

ABSTRACT An online experiment was conducted among a convenience sample of non-Hispanic young Black and White Americans to test the impact of character-audience racial matching on intentions to avoid (mis)using prescription opioids while considering the mediating roles of identification and perceived severity and the moderating role of prescription opioid misuse experience. It found that the racial matching had a positive overall impact on the behavioral intentions. The impact was partly explained by three pathways: 1) identification, 2) perceived severity, and 3) the sequential pathway of identification and perceived severity. It also found that prescription opioid misuse experience moderated the impact of the racial matching on identification. As a result, the racial matching was found to influence the behavioral intentions of participants with different prescription opioid misuse experience via somewhat different routes. These findings have a number of theoretical and practical implications.

CdS Quantum Dot Gels as a Direct Hydrogen Atom Transfer Photocatalyst for C-H Activation.

Here, we report CdS quantum dot (QD) gels, a three-dimensional network of interconnected CdS QDs, as a new type of direct hydrogen atom transfer (d-HAT) photocatalyst for C-H activation. We discovered that the photoexcited CdS QD gel could generate various neutral radicals, including α-amido, heterocyclic, acyl, and benzylic radicals, from their corresponding stable molecular substrates, including amides, thio/ethers, aldehydes, and benzylic compounds. Its C-H activation ability imparts a broad substrate and reaction scope. The mechanistic study reveals that this reactivity is intrinsic to CdS materials, and the neutral radical generation did not proceed via the conventional sequential electron transfer and proton transfer pathway. Instead, the C-H bonds are activated by the photoexcited CdS QD gel via a d-HAT mechanism. This d-HAT mechanism is supported by the linear correlation between the logarithm of the C-H bond activation rate constant and the C-H bond dissociation energy (BDE) with a Brønsted slope α=0.5. Our findings expand the currently limited direct hydrogen atom transfer photocatalysis toolbox and provide new possibilities for photocatalytic C-H activation.

CdS Quantum Dot Gels as a Direct Hydrogen Atom Transfer Photocatalyst for C−H Activation

AbstractHere, we report CdS quantum dot (QD) gels, a three‐dimensional network of interconnected CdS QDs, as a new type of direct hydrogen atom transfer (d‐HAT) photocatalyst for C−H activation. We discovered that the photoexcited CdS QD gel could generate various neutral radicals, including α‐amido, heterocyclic, acyl, and benzylic radicals, from their corresponding stable molecular substrates, including amides, thio/ethers, aldehydes, and benzylic compounds. Its C−H activation ability imparts a broad substrate and reaction scope. The mechanistic study reveals that this reactivity is intrinsic to CdS materials, and the neutral radical generation did not proceed via the conventional sequential electron transfer and proton transfer pathway. Instead, the C−H bonds are activated by the photoexcited CdS QD gel via a d‐HAT mechanism. This d‐HAT mechanism is supported by the linear correlation between the logarithm of the C−H bond activation rate constant and the C−H bond dissociation energy (BDE) with a Brønsted slope α=0.5. Our findings expand the currently limited direct hydrogen atom transfer photocatalysis toolbox and provide new possibilities for photocatalytic C−H activation.

ι-Carrageenan catabolism is initiated by key sulfatases in the marine bacterium Pseudoalteromonas haloplanktis LL1.

Marine bacteria contribute substantially to cycle macroalgae polysaccharides in marine environments. Carrageenans are the primary cell wall polysaccharides of red macroalgae. The carrageenan catabolism mechanism and pathways are still largely unclear. Pseudoalteromonas is a representative bacterial genus that can utilize carrageenan. We previously isolated the strain Pseudoalteromonas haloplanktis LL1 that could grow on ι-carrageenan but produce no ι-carrageenase. Here, through a combination of bioinformatic, biochemical, and genetic analyses, we determined that P. haloplanktis LL1 processed a desulfurization-depolymerization sequential pathway for ι-carrageenan utilization, which was initiated by key sulfatases PhSulf1 and PhSulf2. PhSulf2 acted as an endo/exo-G4S (4-O-sulfation-β-D-galactopyranose) sulfatase, while PhSulf1 was identified as a novel endo-DA2S sulfatase that could function extracellularly. Because of the unique activity of PhSulf1 toward ι-carrageenan rather than oligosaccharides, P. haloplanktis LL1 was considered to have a distinct ι-carrageenan catabolic pathway compared to other known ι-carrageenan-degrading bacteria, which mainly employ multifunctional G4S sulfatases and exo-DA2S (2-O-sulfation-3,6-anhydro-α-D-galactopyranose) sulfatase for sulfate removal. Furthermore, we detected widespread occurrence of PhSulf1-encoding gene homologs in the global ocean, indicating the prevalence of such endo-acting DA2S sulfatases as well as the related ι-carrageenan catabolism pathway. This research provides valuable insights into the enzymatic processes involved in carrageenan catabolism within marine ecological systems.IMPORTANCECarrageenan is a type of linear sulfated polysaccharide that plays a significant role in forming cell walls of marine algae and is found extensively distributed throughout the world's oceans. To the best of our current knowledge, the ι-carrageenan catabolism in marine bacteria either follows the depolymerization-desulfurization sequential process initiated by ι-carrageenase or starts from the desulfurization step catalyzed by exo-acting sulfatases. In this study, we found that the marine bacterium Pseudoalteromonas haloplanktis LL1 processes a distinct pathway for ι-carrageenan catabolism employing a specific endo-acting DA2S-sulfatase PhSulf1 and a multifunctional G4S sulfatase PhSulf2. The unique PhSulf1 homologs appear to be widely present on a global scale, indicating the indispensable contribution of the marine bacteria containing the distinct ι-carrageenan catabolism pathway. Therefore, this study would significantly enrich our understanding of the molecular mechanisms underlying carrageenan utilization, providing valuable insights into the intricate roles of marine bacteria in polysaccharide cycling in marine environments.