Quantum dot-protein interface: Interaction of the CdS quantum dot with human hemoglobin for the study of the energy transfer process and binding mechanism along with detection of the unfolding of hemoglobin.

In this study, the interaction of the human hemoglobin with cost effective and chemically fabricated CdS quantum dots (QDs) (average sizes ≈3nm) has been investigated. The semiconductor QDs showed maximum visible absorption at 445 nm with excitonic formation and band gap of ≈ 2.88 eV along with hexagonal crystalline phase. The binding of QDs-Hb occurs through corona formation to the ground sate complex formation. The life time of the heme pocket binding and reorganization were found to be t1 = 43 min and t2 = 642 min, respectively. The emission quenching of the Hb has been indicated large energy transfer between CdS QDs and Hb with tertiary deformation of Hb. The binding thermodynamics showed highly exothermic nature. The ultrafast decay during corona formation was studied from TCSPC. The results showed that the energy transfer efficiency increases with the increase of the QDs concentration and maximum ≈71.5 % energy transfer occurs and average ultrafast lifetime varies from 5.45 ns to1.51 ns. The deformation and unfolding of the secondary structure of Hb with changes of the α-helix (≈74 % to ≈51.07 %) and ß-sheets (≈8.63 % to ≈10.25 %) have been observed from circular dichroism spectrum. The SAXS spectrum showed that the radius of gyration of CdS QDs-Hb bioconjugate increased (up to 23 ± 0.45 nm) with the increase of the concentration of QDs compare with pure Hb (11 ± 0.23 nm) and Hb becoming more unfolded.

Local and regional processes drive distance decay in structure in a spatial multilayer plant-pollinator network.

Understanding spatial variation in species distribution and community structure is at the core of community ecology. Nevertheless, the effect of distance on metacommunity structure remains little studied. We examine how plant-pollinator community structure changes across geographical distances at a regional scale and disentangle its underlying local and regional processes. We use a multilayer network to represent linked plant-pollinator communities as a metacommunity in the Canary Islands. We used modularity (i.e. the extent to which the community is partitioned into groups of densely interacting species) to quantify distance decay in structure across space. In multilayer modularity, the same species can belong to different modules in different communities, and modules can span communities. This enabled quantifying how similarity in module composition varied with distance between islands. We developed three null models, each controlling for a separate component of the multilayer network, to disentangle the role of species turnover, interaction rewiring and local factors in driving distance decay in structure. We found a pattern of distance decay in structure, indicating that islands tended to share fewer modules with increasing distance. Species turnover (but not interaction rewiring) was the primary regional process triggering distance decay in structure. Local interaction structure also played an essential role in determining the structure similarity of communities at a regional scale. Therefore, local factors that determine species interactions occurring at a local scale drive distance decay in structure at a regional scale. Our work highlights the interplay between local and regional processes underlying community structure. The methodology, and specifically the null models, we developed provides a general framework for linking communities in space and testing different hypotheses regarding the factors generating spatial structure.

Associations between disability type and untreated dental decay among community dwelling US adults.

OBJECTIVE: Individuals with disabilities face elevated risks of adverse oral health outcomes compared with the general population, including worse periodontal health, increased edentulism, and untreated dental decay. Given the varied impacts of different disabilities on people's health and well-being, this study aims to investigate diverse associations between untreated decay and cognitive, physical, emotional, and sensory disabilities among US adults. METHODS: This cross-sectional study analyzed questionnaire and clinical examination data on 7084 adults (≥20 years) from the 2015-18 National Health and Nutrition Examination Survey cycles. Sociodemographics, oral health behaviors, health conditions, and disability were all examined. The prevalence of tooth decay was calculated as the proportion of adults with untreated decay. Survey-weighted multivariable logistic regression was used to assess associations between disability and untreated decay. RESULTS: In general, untreated decay was more than twice as prevalent in individuals with three or more disabilities as in those without any disabilities (34.5% vs. 13.2%, p < 0.001). After adjusting for confounders, lack of functional dentition was the most significant predictor of untreated decay prevalence (adjusted odds ratio: 2.97, 95% CI: 2.37-3.72). Other significant factors were younger age (20-44), non-Hispanic black race or ethnicity, low-income status, having an underlying chronic condition, not having a past-year dental visit, symptomatic dental visits, and current tobacco use. CONCLUSION: No associations were found between disability type (cognitive, emotional, physical, and sensory) and untreated decay among community-dwelling US adults. Several health-related, social, and behavioral factors emerged as primary predictors of untreated decay. Further research is needed to explore disability types and dental caries determinants.

Homozygous mutation of KISS1 receptor (KISS1R) gene identified in a Chinese patient with congenital hypogonadotropic hypogonadism (CHH): case report and literature review.

OBJECTIVES: Congenital hypogonadotropic hypogonadism (CHH) is a rare condition caused by a defect in the production, secretion or action of gonadotropin-releasing hormone. The absence of puberty and varying degrees of gonadotropic deficiency are common symptoms of this disorder. Heterogeneity exists in the clinical presentation of the different clinical subtypes and multiple genes have been implicated in CHH. A number of genetic defects have been identified as causes normosmic CHH, including mutations of GnRHR, GNRH1, KISS1R, KISS1, TACR3 and TAC3. Loss-of-function mutations in KISS1R gene are a rare cause of normosmic CHH. CASE PRESENTATION: We described an 11.5 years old Chinese patient who presented at birth with micropenis, microorchidia and bilateral cryptorchidism. Whole-exome sequencing was also performed and identified a homozygous mutation of KISS1R gene, c.1010_1028del (p.V337Afs*82). The variant was predicted as "deleterious" and classified as "likely pathogenic". This variant has never been reported in patients with CHH. Furthermore, we summarized the clinical presentations and analyzed the phenotype-genotype correlation between CHH and KISS1R mutations in previous reports. CONCLUSIONS: This study details the clinical phenotypes and hormone levels of the patient and expands the spectrum of mutations in the KISS1R gene associated with CHH.

Taming the Production of Bioluminescent Wood Using the White Rot Fungus Desarmillaria Tabescens.

Although bioluminescence is documented both anecdotally and experimentally, the parameters involved in the production of fungal bioluminescence during wood colonization have not been identified to date. Here, for the first time, this work develops a methodology to produce a hybrid living material by manipulating wood colonization through merging the living fungus Desarmillaria tabescens with nonliving balsa (Ochroma pyramidale) wood to achieve and control the autonomous emission of bioluminescence. The hybrid material with the highest bioluminescence is produced by soaking the wood blocks before co-cultivating them with the fungus for 3 months. Regardless of the incubation period, the strongest bioluminescence is evident from balsa wood blocks with a moisture content of 700-1200%, highlighting the fundamental role of moisture content for bioluminescence production. Further characterization reveals that D. tabescens preferentially degraded hemicelluloses and lignin in balsa wood. Fourier-transform infrared spectroscopy reveals a decrease in lignin, while X-ray diffraction analysis confirms that the cellulose crystalline structure is not altered during the colonization process. This information will enable the design of ad-hoc synthetic materials that use fungi as tools to maximize bioluminescence production, paving the way for an innovative hybrid material that could find application in the sustainable production of light.

Nonsense-Mediated mRNA Decay in Human Health and Diseases: Current Understanding, Regulatory Mechanisms and Future Perspectives.

Nonsense-mediated mRNA decay (NMD) is a surveillance mechanism that is conserved across all eukaryotes ensuring the quality of transcripts by targeting messenger RNA (mRNA) harbouring premature stop codons. It regulates the gene expression by targeting aberrant mRNA carrying pre-termination codons (PTCs) and eliminates C-terminal truncated proteins. NMD distinguishes aberrant and non-aberrant transcript by looking after long 3' UTRs and exon-junction complex (EJC) downstream of stop codon that indicate the presence of PTC. Therefore, NMD modulates cellular surveillance and eliminates the truncated proteins but if the PTC escapes the surveillance pathway it can lead to potential negative phenotype resulting in genetic diseases. The alternative splicing also contributes in formation of NMD-sensitive isoforms by introducing PTC. NMD plays a complex role in cancer, it can either aggravate or downregulates the tumour. Some tumours agitate NMD to deteriorate mRNAs encoding tumour suppressor proteins, stress response proteins and neoantigens. In other case, tumours suppress the NMD to encourage the expression of oncoproteins for tumour growth and survival. This mechanism augmented in the development of new therapeutics by PTC read-through mechanism and personalized medicine. Detailed studies on NMD surveillance will possibly lead towards development of strategies for improving human health aligning with United Nations sustainable development goals (SDG 3: Good health and well-being). The potential therapeutic applications of NMD pose a challenge in terms of safe and effective modulation. Understanding the complexities of NMD regulation and its interaction with other cellular processes can lead to the development of new interventions for various diseases.

Curcumin-mediated photodynamic treatment to extend the postharvest shelf-life of strawberries.

This study investigated the potential use of curcumin-mediated photodynamic treatment as a postharvest decontamination technique to reduce microbial load and growth and therefore extend the shelf life of strawberries. Curcumin was applied on strawberries, followed by illumination and storage at 4°C for 16 days. Strawberries were evaluated for decay, microbial load, and physicochemical properties such as weight loss, color, and firmness during storage. The findings revealed that curcumin-mediated photodynamic treatment effectively reduced the decay incidence and severity in strawberries, with 20% less decay occurrence compared to untreated fruits, which was shown to be dependent on curcumin concentration. While a complete reduction in microbial load was observed upon treatment, microbial growth remained unaffected throughout storage. Moreover, photodynamic treatment did not show any adverse impact on color properties and firmness of strawberries. This eco-friendly technique presents potential for fruit's shelf-life extension, although optimization of treatment parameters and photodynamic unit design seems to be essential.

Nutrient-loaded seagrass litter experiences accelerated recalcitrant organic matter decay.

High coastal nutrient loading can cause changes in seagrass chemistry traits that may lead to variability in seagrass litter decomposition processes. Such changes in decomposition have the potential to alter the carbon (C) sequestration capacity within seagrass meadows ('blue carbon'). However, the external and internal factors that drive the variability in decomposition rates of the different organic matter (OM) types of seagrass are poorly understood, especially recalcitrant OM (i.e. cellulose-associated OM and lignin-associated OM), thereby limiting our ability to evaluate the C sequestration potential. It was conducted a laboratory incubation to compare differences in the decomposition of Halophila beccarii litter collected from seagrass meadows with contrasting nutrient loading histories. The exponential decay constants of seagrass litter mass, cellulose-associated OM and lignin-associated OM were 0.009-0.032, 0.014-0.054 and 0.009-0.033 d-1, respectively. The seagrass litter collected from meadows with high nutrient loading exhibited greater losses of mass (25.0-41.2 %), cellulose-associated OM (2.8-18.5 %) and lignin-associated OM (9.6-31.2 %) than litter from relatively low nutrient loading meadows. The initial and temporal changes of the litter nitrogen (N) and phosphorus (P) concentrations, stoichiometric ratios of lignin/N, C/N, and C/P, and cellulose-associated OM content, were strongly correlated with the losses of litter mass and different types of OM. Further, temporal changes of litter C and OM types, particularly the OM and labile OM concentrations, were identified as the main driving factors for the loss of litter mass and loss of different OM types. These results indicated that nutrient-loaded seagrass litter, characterized by elevated nutrient levels and diminished amounts of recalcitrant OM, exhibits an accelerated decay rate for the recalcitrant OM. These differences in litter quality would lead to a reduced contribution of seagrass litter to long-term C stocks in eutrophic meadows, thereby weakening the stability of C sequestration. Considering the expected changes in seagrass litter chemistry traits and decay rates due to long-term nutrient loading, this study provides useful information for improving C sequestration capabilities through effective pollution management.

Characterization of BioID tagging systems in budding yeast and exploring the interactome of the Ccr4-Not complex.

The modified E. coli biotin ligase BirA* was the first developed for proximity labeling of proteins (BioID). However, it has low activity at temperatures below 37˚C, which reduces its effectiveness in organisms growing at lower temperatures, such as budding yeast. Multiple derivatives of the enzymes have been engineered, but a thorough comparison of these variations of biotin ligases and the development of versatile tools for conducting these experiments in Saccharomyces cerevisiae would benefit the community. Here, we designed a suite of vectors to compare the activities of biotin ligase enzymes in yeast. We found that the newer TurboID versions were the most effective at labeling proteins, but they displayed low constitutive labeling of proteins even in the absence of exogenous biotin, due to biotin contained in the culture medium. We describe a simple strategy to express free BioID enzymes in cells that can be used as an appropriate control in BioID studies to account for the promiscuous labeling of proteins caused by random interactions between bait-BioID enzymes in cells. We also describe chemically-induced BioID systems exploiting the rapamycin-stabilized FRB-FKBP interaction. Finally, we used the TurboID version of the enzyme to explore the interactome of different subunits of the Ccr4-Not gene regulatory complex. We find that Ccr4-Not predominantly labeled cytoplasmic mRNA regulators, consistent with its function in mRNA decay and translation quality control in this cell compartment.

Assessing Clinical Variables Associated With Femoral Muscle Decay as Measured by Point-of-Care Ultrasound in Critically Ill Children.

OBJECTIVES: Skeletal muscle wasting is a common occurrence in critical illness, often resulting in intensive care unit (ICU)-acquired weakness. This study aims to identify clinical factors associated with muscle decay in mechanically ventilated critically ill children. Utilizing point-of-care ultrasound, a noninvasive and cost-effective tool, we assess muscle decay through ultrasound of the quadriceps femoris. METHODS: A prospective observational study was conducted in a single-center quaternary-care pediatric intensive care unit at a children's hospital. A convenience sample of 103 sedated and mechanically ventilated patients were enrolled in this study. Ultrasound measurements of quadriceps femoris muscle thickness were taken, and daily muscle decay rates were calculated. Demographic, clinical, and outcome data were analyzed for correlations with muscle decay. RESULTS: Among the enrolled patients, 67 had repeat measurements. Muscle thickness change aligned with prior studies, with a mean daily change of -1.9% [IQR -0.8, -5.0]. Adequate cumulative caloric intake (>60% of goal) correlated with less muscle decay compared with inadequate intake (-1.8 vs -2.4%, P < .001). Average daily muscle change correlated with both ICU and hospital length of stay (LOS) (r = .328, P = .007 and r = .393, P = .001). No significant correlations emerged between muscle change and mortality, disease severity, fluid balance, early mobilization, steroid exposure, or sedative and paralytic use. CONCLUSION: This study demonstrates early and frequent muscle decay in critically ill children, as detected by point-of-care ultrasound. Average daily muscle decay was associated with longer ICU and hospital LOS. Adequate cumulative caloric intake is linked to reduced muscle decay. These findings contribute to understanding muscle wasting in critically ill pediatric patients.

Analysis of vibration signals near ground surface during blasting excavation of a tunnel in fractured rock.

This study aims to analyze the vibration signals near the ground surface due to the underneath drilling and blasting activities in a fissured rock tunnel. Blasting induced vibration on the ground surface was continuously monitored in a fissured rock tunnel drilling and blasting excavation project in field. Wavelet packet analysis of the vibration signals using Matlab was carried out for signal denoising, differential blasting delay time interval identification, and three-way time-frequency energy analysis. The results show that within a 30 m range from the palm face, the dominant frequency bands of blasting-induced vibrations on the ground surface were concentrated in the range of 0-130 Hz. Two prominent peak frequency bands were identified at 31.25-39.063 Hz (low-frequency band) and 93.75-101.56 Hz (high-frequency band), accounting for 12% of the total energy. Among the three directions of ground surface vibrations, the energy decay was the most significant in the x-direction (tunnel excavation direction), which amounted to 54.29% of the overall energy decay with increasing distance. The energy decay within the 50-80 Hz range was the most pronounced (more than 90%), when the angle between the vibration propagation direction and the fissure or joint direction was 75°. The conclusions provide the insights in the attenuation of blast-induced vibrations in fissured rock and can potentially assist in the design of blasting vibration control.

Recurrent neural network-aided processing of incomplete free induction decays in 1H-MRS of the brain.

In the case of limited sampling windows or truncation of free induction decays (FIDs) for artifact removal in proton magnetic resonance spectroscopy (1H-MRS) and spectroscopic imaging (1H-MRSI), metabolite quantification needs to be performed on incomplete FIDs. Given that FIDs are naturally time-domain sequential data, we investigated the potential of recurrent neural network (RNN)-types of neural networks (NNs) in the processing of incomplete human brain FIDs with or without FID restoration prior to quantitative analysis at 3.0T. First, we employed an RNN encoder-decoder and developed it to restore incomplete FIDs (rRNN) with different amounts of sampled data. The quantification of metabolites from the rRNN-restored FIDs was achieved by using LCModel. Second, we modified the RNN encoder-decoder and developed it to convert incomplete brain FIDs into incomplete metabolite-only FIDs without restoration, followed by linear regression using a metabolite basis set for quantitative analysis (cRNN). In consideration of the practical benefit of the FID restoration with respect to pure zero-filling, development and analysis of the NNs were focused particularly on the incomplete FIDs with only the first 64 data points retained. All NNs were trained on simulated data and tested mainly on in vivo data acquired from healthy volunteers (n = 27). Strong correlations were obtained between the NN-derived and ground truth metabolite content (LCModel-derived content on fully sampled FIDs) for myo-inositol, total choline, and total creatine (normalized to total N-acetylaspartate) on the in vivo data using both rRNN (R = 0.83-0.94; p ≤ 0.05) and cRNN (R = 0.86-0.91; p ≤ 0.05). RNN-types of NNs have potential in the quantification of the major brain metabolites from the FIDs with substantially reduced sampled data points. For the metabolites with low to medium SNR, the performance of the NNs needs to be further improved, for which development of more elaborate and advanced simulation techniques would be of help, but remains challenging.

Evaluation of drinking water quality and associated health risks in Adama City, Ethiopia.

Drinking water deterioration causes to risk of public health which is essential to supply safe water to the public. This study assessed groundwater quality and health risks in Adama City by analyzing groundwater and chlorine samples. Ion photometry techniques detected anions and cations, ensuring accuracy with quality control protocols. Water Quality Index (WQI) and chlorine decay modeling via WaterGEMs assessed water quality. Hazard index (HI) calculations evaluated exposure risks; Pearson correlation analyzed physicochemical relationships. Findings highlighted water quality and hazards. Aquachem software analyzed Adama's groundwater, revealing high total alkalinity and potassium exceeding WHO limits. Other parameters (nitrate, nitrite, chloride, fluoride, and sulfate) met WHO standards. Sodium, calcium, magnesium, iron, manganese, and boron also complied. Multivariate analysis showed significant parameter associations. Water types included Ca-Na-HCO3 (27.27 %), Na-Ca-HCO3 (36.36 %), Na-Ca-Mg-HCO3, Na-HCO3 (9.09 % each), and Na-Mg-HCO3 (18.18 %). Drinking Water Quality Index rated boreholes as "Good." Health risk assessments found no significant fluoride, iron, or manganese risks across ages. Chlorine residual analysis indicated 74 % had levels below WHO recommendations, prompting chlorine dosing adjustments. Findings inform groundwater management in Adama City.

Highly Efficient Near-Infrared Luminescent Radicals with Emission Peaks over 750 nm.

Purely organic molecules exhibiting near-infrared (NIR) emission possess considerable potential for applications in both biological and optoelectronic technological domains, owing to their inherent advantages such as cost-effectiveness, biocompatibility, and facile chemical modifiability. However, the repertoire of such molecules with emission peaks exceeding 750 nm and concurrently demonstrating high photoluminescence quantum efficiency (PLQE) remains relatively scarce due to the energy gap law. Herein, we report two open-shell NIR radical emitters, denoted as DMNA-Cz-BTM and DMNA-PyID-BTM, achieved through the strategic integration of a donor group (DMNA) onto the Cz-BTM and PyID-BTM frameworks, respectively. We found that the donor-acceptor molecular structure allows the two designed radical emitters to exhibit a charge-transfer excited state and spatially separated electron and hole levels with non-bonding characteristics. Thus, the high-frequency vibrations are effectively suppressed. Besides, the reduction of low-frequency vibrations is observed. Collectively, the non-radiative decay channel is significantly suppressed, leading to exceptional NIR PLQE values. Specifically, DMNA-Cz-BTM manifests an emission peak at 758 nm alongside a PLQE of 55%, whereas DMNA-PyID-BTM exhibits an emission peak at 778 nm with a PLQE of 66%. Notably, these represent the pinnacle of PLQE among metal-free organic NIR emitters with emission peaks surpassing 750 nm.

Size-dependent release and temperature-dependent degradation of salmonid environmental DNA under laboratory conditions.

The degradation of environmental DNA (eDNA) and its release from fish were investigated in laboratory experiments for seven salmonid fishes. The eDNA concentration in experimental tanks without fish decreased exponentially, with a higher rate of decline observed under higher water temperature conditions. When a fish was introduced into a tank, the eDNA concentration was positively correlated with the length and weight of the fish.

Spatial and environmental drivers of temperate estuarine archaeal communities.

Archaea play a crucial role in the global biogeochemical cycling of elements and nutrients, helping to maintain the functional stability of estuarine systems. This study characterised the abundance and diversity of archaeal communities and identified the environmental conditions shaping these microbial communities within six temperate estuaries along approximately 500 km of the New South Wales coastline, Australia. Estuarine sediments were found to exhibit significantly higher species richness than planktonic communities, with representative sequences from the Crenarchaeota phylum characterising each environment. Ordinate analyses revealed catchment characteristics as the strongest drivers of community variability. Our results also provide evidence supporting distance-decay patterns of archaeal biogeography across intermediate scales within and between temperate estuaries, contributing to a growing body of evidence revealing the extent spatial scales play in shaping microbial communities. This study expands our understanding of microbial diversity in temperate estuaries, with a specific focus on archaeal community structure and their role in maintaining ecosystem stability.

Comparative analyses suggest a link between mRNA splicing, stability, and RNA covalent modifications in flowering plants.

BACKGROUND: In recent years, covalent modifications on RNA nucleotides have emerged as pivotal moieties influencing the structure, function, and regulatory processes of RNA Polymerase II transcripts such as mRNAs and lncRNAs. However, our understanding of their biological roles and whether these roles are conserved across eukaryotes remains limited. RESULTS: In this study, we leveraged standard polyadenylation-enriched RNA-sequencing data to identify and characterize RNA modifications that introduce base-pairing errors into cDNA reads. Our investigation incorporated data from three Poaceae (Zea mays, Sorghum bicolor, and Setaria italica), as well as publicly available data from a range of stress and genetic contexts in Sorghum and Arabidopsis thaliana. We uncovered a strong enrichment of RNA covalent modifications (RCMs) deposited on a conserved core set of nuclear mRNAs involved in photosynthesis and translation across these species. However, the cohort of modified transcripts changed based on environmental context and developmental program, a pattern that was also conserved across flowering plants. We determined that RCMs can partly explain accession-level differences in drought tolerance in Sorghum, with stress-associated genes receiving a higher level of RCMs in a drought tolerant accession. To address function, we determined that RCMs are significantly enriched near exon junctions within coding regions, suggesting an association with splicing. Intriguingly, we found that these base-pair disrupting RCMs are associated with stable mRNAs, are highly correlated with protein abundance, and thus likely associated with facilitating translation. CONCLUSIONS: Our data point to a conserved role for RCMs in mRNA stability and translation across the flowering plant lineage.

Recessive loss-of-function variants in DPH1 identified as the molecular cause in a sibling pair previously diagnosed with Fine-Lubinsky syndrome.

Fine-Lubinsky syndrome is a rare clinically defined syndrome sometimes referred to as brachycephaly, deafness, cataract, microstomia, and impaired intellectual development syndrome. Here we provide a clinical and molecular update for a sibling pair diagnosed with Fine-Lubinsky syndrome. An extensive genetic work-up, including chromosomal microarray analysis and quad exome sequencing, was nondiagnostic. However, a research reanalysis of their exome sequencing data revealed that both were homozygous for an intronic c.749+39G>A [NM_001383.6] variant in DPH1. RNAseq analysis performed on RNA from fibroblasts revealed significantly reduced expression of DPH1 transcripts suggestive of abnormal splicing followed by nonsense mediated mRNA decay. Since the phenotypes of this sibling pair were consistent with those associated with the inheritance of biallelic pathogenic variants in DPH1, they were given a diagnosis of developmental delay with short stature, dysmorphic facial features, and sparse hair 1 (DEDSSH1). This leads us to recommend that all individuals with a clinical diagnosis of Fine-Lubinsky syndrome be screened for variants in DPH1. The clinical histories of this sibling pair emphasize that hearing loss associated with DEDSSH1 may remit over time and that individuals with DEDSSH1 should be monitored for the development of cardiomyopathy. This case also demonstrates the clinical utility of RNAseq as a means of functionally validating the effects of intronic variants that may affect splicing.

Unveiling the kinetic versatility of aryl-alcohol oxidases with different electron acceptors.

Introduction: Aryl-alcohol oxidase (AAO) shows a pronounced duality as oxidase and dehydrogenase similar to that described for other glucose-methanol-choline (GMC) oxidase/dehydrogenase superfamily proteins involved in lignocellulose decomposition. In this work, we detail the overall mechanism of AAOs from Pleurotus eryngii and Bjerkandera adusta for catalyzing the oxidation of natural aryl-alcohol substrates using either oxygen or quinones as electron acceptors and describe the crystallographic structure of AAO from B. adusta in complex with a product analogue. Methods: Kinetic studies with 4-methoxybenzyl and 3-chloro-4- methoxybenzyl alcohols, including both transient-state and steady-state analyses, along with interaction studies, provide insight into the oxidase and dehydrogenase mechanisms of these enzymes. Moreover, the resolution of the crystal structure of AAO from B. adusta allowed us to compare their overall folding and the structure of the active sites of both AAOs in relation to their activities. Results and Discussion: Although both enzymes show similar mechanistic properties, notable differences are highlighted in this study. In B. adusta, the AAO oxidase activity is limited by the reoxidation of the flavin, while in P. eryngii the slower step takes place during the reductive half-reaction, which determines the overall reaction rate. By contrast, dehydrogenase activity in both enzymes, irrespective of the alcohol participating in the reaction, is limited by the hydroquinone release from the active site. Despite these differences, both AAOs are more efficient as dehydrogenases, supporting the physiological role of this activity in lignocellulosic decay. This dual activity would allow these enzymes to adapt to different environments based on the available electron acceptors.

The influence of vertebrate scavengers on leakage of nutrients from carcasses.

The decomposition of carcasses by scavengers and microbial decomposers is an important component of the biochemical cycle that can strongly alter the chemical composition of soils locally. Different scavenger guilds are assumed to have a different influence on the chemical elements that leak into the soil, although this assumption has not been empirically tested. Here, we experimentally determine how different guilds of vertebrate scavengers influence local nutrient dynamics. We performed a field experiment in which we systematically excluded different subsets of vertebrate scavengers from decomposing carcasses of fallow deer (Dama dama), and compared elemental concentrations in the soil beneath and in the vegetation next to the carcasses over time throughout the decomposition process. We used four exclusion treatments: excluding (1) no scavengers, thus allowing them all; (2) wild boar (Sus scrofa); (3) all mammals; and (4) all mammals and birds. We found that fluxes of several elements into the soil showed distinct peaks when all vertebrates were excluded. Especially, trace elements (Cu and Zn) seemed to be influenced by carcass decomposition. However, we found no differences in fluxes between partial exclusion treatments. Thus, vertebrate scavengers indeed reduce leakage of elements from carcasses into the soil, hence influencing local biochemical cycles, but did so independent of which vertebrate scavenger guild had access. Our results suggest that carcass-derived elements are dispersed over larger areas rather than locally leak into the soil when vertebrate scavengers dominate the decomposition process.