IMBAS-MS Discovers Organ-Specific HLA Peptide Patterns in Plasma.

Distinction of non-self from self is the major task of the immune system. Immunopeptidomics studies the peptide repertoire presented by the human leukocyte antigen (HLA) protein, usually on tissues. However, HLA peptides are also bound to plasma soluble HLA (sHLA), but little is known about their origin and potential for biomarker discovery in this readily available biofluid. Currently, immunopeptidomics is hampered by complex workflows and limited sensitivity, typically requiring several mL of plasma. Here, we take advantage of recent improvements in the throughput and sensitivity of mass spectrometry (MS)-based proteomics to develop a highly sensitive, automated, and economical workflow for HLA peptide analysis, termed Immunopeptidomics by Biotinylated Antibodies and Streptavidin (IMBAS). IMBAS-MS quantifies more than 5000 HLA class I peptides from only 200 µl of plasma, in just 30 min. Our technology revealed that the plasma immunopeptidome of healthy donors is remarkably stable throughout the year and strongly correlated between individuals with overlapping HLA types. Immunopeptides originating from diverse tissues, including the brain, are proportionately represented. We conclude that sHLAs are a promising avenue for immunology and potentially for precision oncology.

Full Mass Range ΦSDM Orbitrap Mass Spectrometry for DIA Proteome Analysis.

Optimizing data-independent acquisition methods for proteomics applications often requires balancing spectral resolution and acquisition speed. Here, we describe a real-time full mass range implementation of the phase-constrained spectrum deconvolution method (ΦSDM) for Orbitrap mass spectrometry that increases mass resolving power without increasing scan time. Comparing its performance to the standard enhanced Fourier transformation signal processing revealed that the increased resolving power of ΦSDM is beneficial in areas of high peptide density and comes with a greater ability to resolve low-abundance signals. In a standard 2 h analysis of a 200 ng HeLa digest, this resulted in an increase of 16% in the number of quantified peptides. As the acquisition speed becomes even more important when using fast chromatographic gradients, we further applied ΦSDM methods to a range of shorter gradient lengths (21, 12, and 5 min). While ΦSDM improved identification rates and spectral quality in all tested gradients, it proved particularly advantageous for the 5 min gradient. Here, the number of identified protein groups and peptides increased by >15% in comparison to enhanced Fourier transformation processing. In conclusion, ΦSDM is an alternative signal processing algorithm for processing Orbitrap data that can improve spectral quality and benefit quantitative accuracy in typical proteomics experiments, especially when using short gradients.

Synthesis and characterization of Craig-type antiaromatic species with [4n + 2] π electrons.

Antiaromaticity is extended from aromaticity as a complement to describe the unsaturated cyclic molecules with antiaromatic destabilization. To prepare antiaromatic species is a particularly challenging goal in synthetic chemistry because of the thermodynamic instability of such molecules. Among that, both Hückel and Möbius antiaromatic species have been reported, whereas the Craig one has not been realized to date. Here, we report the first example of planar Craig antiaromatic species. Eight Craig antiaromatic compounds were synthesized by deprotonation-induced reduction process and were fully characterized as follows. Single-crystal X-ray crystallography showed that these complexes have planar structures composed of fused five-membered rings with clearly alternating carbon-carbon bond lengths. In addition, proton NMR (1H NMR) spectroscopy in these structures showed distinctive upfield shifts of the proton peaks to the range of antiaromatic peripheral hydrogens. Experimental spectroscopy observations, along with density-functional theory (DFT) calculations, provided evidence for the Craig antiaromaticity of these complexes. Further study experimentally and theoretically revealed that the strong exothermicity of the acid-base neutralization process was the driving force for this challenging transformation forming Craig antiaromatic species. Our findings complete a full cycle of aromatic chemistry, opening an avenue for the development of new class of antiaromatic systems.

Recent H9N2 avian influenza virus lost hemagglutination activity due to a K141N substitution in hemagglutinin.

The H9N2 avian influenza virus (AIV) represents a significant risk to both the poultry industry and public health. Our surveillance efforts in China have revealed a growing trend of recent H9N2 AIV strains exhibiting a loss of hemagglutination activity at 37°C, posing challenges to detection and monitoring protocols. This study identified a single K141N substitution in the hemagglutinin (HA) glycoprotein as the culprit behind this diminished hemagglutination activity. The study evaluated the evolutionary dynamics of residue HA141 and studied the impact of the N141K substitution on aspects such as virus growth, thermostability, receptor-binding properties, and antigenic properties. Our findings indicate a polymorphism at residue 141, with the N variant becoming increasingly prevalent in recent Chinese H9N2 isolates. Although both wild-type and N141K mutant strains exclusively target α,2-6 sialic acid receptors, the N141K mutation notably impedes the virus's ability to bind to these receptors. Despite the mutation exerting minimal influence on viral titers, antigenicity, and pathogenicity in chicken embryos, it significantly enhances viral thermostability and reduces plaque size on Madin-Darby canine kidney (MDCK) cells. Additionally, the N141K mutation leads to decreased expression levels of HA protein in both MDCK cells and eggs. These findings highlight the critical role of the K141N substitution in altering the hemagglutination characteristics of recent H9N2 AIV strains under elevated temperatures. This emphasizes the need for ongoing surveillance and genetic analysis of circulating H9N2 AIV strains to develop effective control and prevention measures.IMPORTANCEThe H9N2 subtype of avian influenza virus (AIV) is currently the most prevalent low-pathogenicity AIV circulating in domestic poultry globally. Recently, there has been an emerging trend of H9N2 AIV strains acquiring increased affinity for human-type receptors and even losing their ability to bind to avian-type receptors, which raises concerns about their pandemic potential. In China, there has been a growing number of H9N2 AIV strains that have lost their ability to agglutinate chicken red blood cells, leading to false-negative results during surveillance efforts. In this study, we identified a K141N mutation in the HA protein of H9N2 AIV to be responsible for the loss of hemagglutination activity. This finding provides insight into the development of effective surveillance, prevention, and control strategies to mitigate the threat posed by H9N2 AIV to both animal and human health.

The structural context of posttranslational modifications at a proteome-wide scale.

The recent revolution in computational protein structure prediction provides folding models for entire proteomes, which can now be integrated with large-scale experimental data. Mass spectrometry (MS)-based proteomics has identified and quantified tens of thousands of posttranslational modifications (PTMs), most of them of uncertain functional relevance. In this study, we determine the structural context of these PTMs and investigate how this information can be leveraged to pinpoint potential regulatory sites. Our analysis uncovers global patterns of PTM occurrence across folded and intrinsically disordered regions. We found that this information can help to distinguish regulatory PTMs from those marking improperly folded proteins. Interestingly, the human proteome contains thousands of proteins that have large folded domains linked by short, disordered regions that are strongly enriched in regulatory phosphosites. These include well-known kinase activation loops that induce protein conformational changes upon phosphorylation. This regulatory mechanism appears to be widespread in kinases but also occurs in other protein families such as solute carriers. It is not limited to phosphorylation but includes ubiquitination and acetylation sites as well. Furthermore, we performed three-dimensional proximity analysis, which revealed examples of spatial coregulation of different PTM types and potential PTM crosstalk. To enable the community to build upon these first analyses, we provide tools for 3D visualization of proteomics data and PTMs as well as python libraries for data accession and processing.

APC mutations disrupt ß-catenin destruction complex condensates organized by Axin phase separation.

The Wnt/ß-catenin pathway is critical to maintaining cell fate decisions. Recent study showed that liquid-liquid-phase separation (LLPS) of Axin organized the ß-catenin destruction complex condensates in a normal cellular state. Mutations inactivating the APC gene are found in approximately 80% of all human colorectal cancer (CRC). However, the molecular mechanism of the formation of ß-catenin destruction complex condensates organized by Axin phase separation and how APC mutations impact the condensates are still unclear. Here, we report that the ß-catenin destruction complex, which is constructed by Axin, was assembled condensates via a phase separation process in CRC cells. The key role of wild-type APC is to stabilize destruction complex condensates. Surprisingly, truncated APC did not affect the formation of condensates, and GSK 3ß and CK1α were unsuccessfully recruited, preventing ß-catenin phosphorylation and resulting in accumulation in the cytoplasm of CRCs. Besides, we propose that the phase separation ability of Axin participates in the nucleus translocation of ß-catenin and be incorporated and concentrated into transcriptional condensates, affecting the transcriptional activity of Wnt signaling pathway.

Bleeding Risk of Cold Versus Hot Snare Polypectomy for Pedunculated Colorectal Polyps Measuring 10 mm or Less: Subgroup Analysis of a Large Randomized Controlled Trial.

INTRODUCTION: Concerns regarding bleeding remain in cold snare polypectomy (CSP) for small pedunculated (0-Ip) polyps. The aim of this study was to compare the risk of CSP and hot snare polypectomy (HSP) for such lesions. METHODS: Data on 0-Ip colorectal polyps ≤10 mm were extracted from a large, pragmatic, randomized trial. Immediate postpolypectomy bleeding (IPPB), defined as the perioperative use of a clip for bleeding, was evaluated through polyp-level analysis. Delayed postpolypectomy bleeding (DPPB), defined as bleeding occurring within 2 weeks postoperatively, was assessed at the patient-level among patients whose polyps were all ≤10 mm, including at least one 0-Ip polyp. RESULTS: A total of 647 0-Ip polyps (CSP: 306; HSP: 341) were included for IPPB analysis and 386 patients (CSP: 192; HSP: 194) for DPPB analysis. CSP was associated with a higher incidence of IPPB (10.8% vs 3.2%, P < 0.001) but no adverse clinical events. The procedure time of all polypectomies was shorter for CSP than for HSP (123.0 ± 117.8 vs 166.0 ± 237.7 seconds, P = 0.003), while the procedure time of polypectomies with IPPB were similar (249.8 ± 140.2 vs 227.4 ± 125.9 seconds, P = 0.64). DPPB was observed in 3 patients (1.5%) in the HSP group, including one patient (0.5%) with severe bleeding, but not in the CSP group. DISCUSSION: Despite CSP being associated with more IPPB events, it could be timely treated without adverse outcomes. Notably, no delayed bleeding occurred in the CSP group. Our findings support the use of CSP for 0-Ip polyps ≤ 10 mm.

Precise, fast and comprehensive analysis of intact glycopeptides and modified glycans with pGlyco3.

Great advances have been made in mass spectrometric data interpretation for intact glycopeptide analysis. However, accurate identification of intact glycopeptides and modified saccharide units at the site-specific level and with fast speed remains challenging. Here, we present a glycan-first glycopeptide search engine, pGlyco3, to comprehensively analyze intact N- and O-glycopeptides, including glycopeptides with modified saccharide units. A glycan ion-indexing algorithm developed for glycan-first search makes pGlyco3 5-40 times faster than other glycoproteomic search engines without decreasing accuracy or sensitivity. By combining electron-based dissociation spectra, pGlyco3 integrates a dynamic programming-based algorithm termed pGlycoSite for site-specific glycan localization. Our evaluation shows that the site-specific glycan localization probabilities estimated by pGlycoSite are suitable to localize site-specific glycans. With pGlyco3, we confidently identified N-glycopeptides and O-mannose glycopeptides that were extensively modified by ammonia adducts in yeast samples. The freely available pGlyco3 is an accurate and flexible tool that can be used to identify glycopeptides and modified saccharide units.

Global distribution, receptor binding, and cross-species transmission of H6 influenza viruses: risks and implications for humans.

The H6 subtype of avian influenza virus (AIV) is a pervasive subtype that is ubiquitously found in both wild bird and poultry populations across the globe. Recent investigations have unveiled its capacity to infect mammals, thereby expanding its host range beyond that of other subtypes and potentially facilitating its global transmission. This heightened breadth also endows H6 AIVs with the potential to serve as a genetic reservoir for the emergence of highly pathogenic avian influenza strains through genetic reassortment and adaptive mutations. Furthermore, alterations in key amino acid loci within the H6 AIV genome foster the evolution of viral infection mechanisms, which may enable the virus to surmount interspecies barriers and infect mammals, including humans, thus posing a potential threat to human well-being. In this review, we summarize the origins, dissemination patterns, geographical distribution, cross-species transmission dynamics, and genetic attributes of H6 influenza viruses. This study holds implications for the timely detection and surveillance of H6 AIVs.

Robust dimethyl-based multiplex-DIA doubles single-cell proteome depth via a reference channel.

Single-cell proteomics aims to characterize biological function and heterogeneity at the level of proteins in an unbiased manner. It is currently limited in proteomic depth, throughput, and robustness, which we address here by a streamlined multiplexed workflow using data-independent acquisition (mDIA). We demonstrate automated and complete dimethyl labeling of bulk or single-cell samples, without losing proteomic depth. Lys-N digestion enables five-plex quantification at MS1 and MS2 level. Because the multiplexed channels are quantitatively isolated from each other, mDIA accommodates a reference channel that does not interfere with the target channels. Our algorithm RefQuant takes advantage of this and confidently quantifies twice as many proteins per single cell compared to our previous work (Brunner et al, PMID 35226415), while our workflow currently allows routine analysis of 80 single cells per day. Finally, we combined mDIA with spatial proteomics to increase the throughput of Deep Visual Proteomics seven-fold for microdissection and four-fold for MS analysis. Applying this to primary cutaneous melanoma, we discovered proteomic signatures of cells within distinct tumor microenvironments, showcasing its potential for precision oncology.

Comparison of Short-Term Outcomes After Robotic Versus Laparoscopic Radical Gastrectomy for Advanced Gastric Cancer in Elderly Individuals: A Propensity Score-Matching Study.

BACKGROUND: Robotic gastrectomy (RG) has been widely used to treat gastric cancer. However, whether the short-term outcomes of robotic gastrectomy are superior to those of laparoscopic gastrectomy (LG) for elderly patients with advanced gastric cancer has not been reported. METHODS: The study enrolled of 594 elderly patients with advanced gastric cancer who underwent robotic or laparoscopic radical gastrectomy. The RG cohort was matched 1:3 with the LG cohort using propensity score-matching (PSM). RESULTS: After PSM, 121 patients were included in the robot group and 363 patients in the laparoscopic group. Excluding the docking and undocking times, the operation time of the two groups was similar (P = 0.617). The RG group had less intraoperative blood loss than the LG group (P < 0.001). The time to ambulation and first liquid food intake was significantly shorter in the RG group than in the LG group (P < 0.05). The incidence of postoperative complications did not differ significantly between the two groups (P = 0.14). Significantly more lymph nodes were dissected in the RG group than in the LG group (P = 0.001). Postoperative adjuvant chemotherapy was started earlier in the RG group than in the LG group (P = 0.02). CONCLUSIONS: For elderly patients with advanced gastric cancer, RG is safe and feasible. Compared with LG, RG is associated with less intraoperative blood loss; a faster postoperative recovery time, allowing a greater number of lymph nodes to be dissected; and earlier adjuvant chemotherapy.

Heterozygous Seryl-tRNA Synthetase 1 Variants Cause Charcot-Marie-Tooth Disease.

OBJECTIVE: Despite the increasing number of genes associated with Charcot-Marie-Tooth (CMT) disease, many patients currently still lack appropriate genetic diagnosis for this disease. Autosomal dominant mutations in aminoacyl-tRNA synthetases (ARSs) have been implicated in CMT. Here, we describe causal missense mutations in the gene encoding seryl-tRNA synthetase 1 (SerRS) for 3 families affected with CMT. METHODS: Whole-exome sequencing was performed in 16 patients and 14 unaffected members of 3 unrelated families. The functional impact of the genetic variants identified was investigated using bioinformatic prediction tools and confirmed using cellular and biochemical assays. RESULTS: Combined linkage analysis for the 3 families revealed significant linkage (Zmax LOD = 6.9) between the genomic co-ordinates on chromosome 1: 108681600-110300504. Within the linkage region, heterozygous SerRS missense variants segregated with the clinical phenotype in the 3 families. The mutant SerRS proteins exhibited reduced aminoacylation activity and abnormal SerRS dimerization, which suggests the impairment of total protein synthesis and induction of eIF2α phosphorylation. INTERPRETATION: Our findings suggest the heterozygous SerRS variants identified represent a novel cause for autosomal dominant CMT. Mutant SerRS proteins are known to impact various molecular and cellular functions. Our findings provide significant advances on the current understanding of the molecular mechanisms associated with ARS-related CMT. ANN NEUROL 2023;93:244-256.

Quantitative evaluation of choroidal and retinal microvasculature post-alcohol consumption: A pilot study.

PURPOSE: The aim of this study was to assess the impact of acute, heavy alcohol consumption on the ocular microvasculature, providing insight into the largely unexplored response of microvascular structures to excessive drinking. METHODS: Healthy volunteers in this prospective pilot study were tasked with consuming spirits, wine, and water at different times. Alcohol intake was measured according to body weight (g/kg). The ocular microvascular parameters primarily including choroidal volume (CV) and choroidal vessel volume (CVV) reflecting arteriolovenularity, and choroidal capillary density (CCD) reflecting capillary, were evaluated using swept-source optical coherence tomography angiography at baseline and 0.5-, 1-, 2-, and 3-hour post-consumption. RESULTS: A total of 34 eyes underwent 170 successful examinations in this study. After consuming spirits or wine, we observed significant decreases in CV and CVV values (all P < 0.01 for 0.5-, 1-, 2-, and 3-hour post-consumption), along with significant increase in CCD (P < 0.05 at 0.5-, 1-, 2-hour post-spirits consumption and 1-hour post-wine consumption). The most pronounced changes occurred 1-hour after spirits or wine consumption (all P < 0.001 in both univariate and multivariate model). However, post-consumption changes in the ocular microvasculature showed no significant differences between spirits and wine (P > 0.05). Additionally, no significant differences were observed in any parameters after water intake (all P > 0.05). CONCLUSIONS: Excessive alcohol consumption leads to ocular arteriolovenular vasoconstriction and capillary vasodilation, most evident 1-hour post-consumption of spirits and wine. Our research provides insight into alcohol's immediate ocular microvascular effects, hinting at systemic microvascular effects.

Association between three-dimensional morphological features and functional indicators of neovascular age-related macular degeneration.

PURPOSE: To investigate the correlation between morphological lesions and functional indicators in eyes with neovascular age-related macular degeneration (nAMD). METHODS: This was a prospective observational study of treatment-naïve nAMD eyes. Various morphological lesions and impaired retinal structures were manually measured at baseline and month-3 in three-dimensional optical coherence tomography (OCT) and optical coherence tomography angiography (OCTA) images, including the volumes (mm3) of macular neovascularization (MNV), avascular subretinal hyperreflective material (avascular SHRM), subretinal fluid (SRF), intraretinal fluid (IRF), serous pigment epithelial detachment (sPED) and the impaired area (mm2) of ellipsoid zone (EZ), external limiting membrane (ELM) and outer nuclear layer (ONL). RESULTS: Sixty-three eyes were included. The volume of avascular SHRM showed persistent positive associations with the area of EZ damage, both at baseline, month-3, and change values (all P < 0.001). Poor BCVA (month-3) was associated with larger volumes of baseline IRF (ß = 0.377, P < 0.001), avascular SHRM (ß = 0.306, P = 0.032), and ELM impairment area (ß = 0.301, P = 0.036) in multivariate model. EZ and ELM impairment were primarily associated with baseline avascular SHRM (ß = 0.374, p = 0.003; ß = 0.388, P < 0.001, respectively), while ONL impairment primarily associated with MNV (ß = 0.475, P < 0.001). CONCLUSION: The utilization of three-dimensional measurements elucidates the intrinsic connections among various lesions and functional outcomes. In particular, avascular SHRM plays an important role in prognosis of nAMD.

Prognostic value of the Naples prognostic score in patients with intrahepatic cholangiocarcinoma after hepatectomy.

BACKGROUND: The Naples Prognostic Score (NPS), integrating inflammatory and nutritional biomarkers, has been reported to be associated with the prognosis of various malignancies, but there is no report on intrahepatic cholangiocarcinoma (ICC). This study aimed to explore the prognostic value of NPS in patients with ICC. METHODS: Patients with ICC after hepatectomy were collected, and divided into three groups. The prognosis factors were determined by Cox regression analysis. Predictive efficacy was evaluated by the time-dependent receiver operating characteristic (ROC) curves. RESULTS: A total of 174 patients were included (Group 1: 33 (19.0%) patients; Group 2: 83 (47.7%) patients; and Group 3: 58 (33.3%) patients). The baseline characteristics showed the higher the NPS, the higher the proportion of patients with cirrhosis and Child-Pugh B, and more advanced tumors. The Kaplan-Meier curves reflect higher NPS were associated with poor survival. Multivariable analysis showed NPS was an independent risk factor of overall survival (NPS group 2 vs. 1: HR = 1.671, 95% CI: 1.022-3.027, p = 0.009; NPS group 3 vs. 1: HR = 2.208, 95% CI: 1.259-4.780, p = 0.007) and recurrence-free survival (NPS group 2 vs. 1: HR = 1.506, 95% CI: 1.184-3.498, p = 0.010; NPS group 3 vs. 1: HR = 2.141, 95% CI: 2.519-4.087, P = 0.001). The time ROC indicated NPS was superior to other models in predicting prognosis. CONCLUSIONS: NPS is a simple and effective tool for predicting the long-term survival of patients with ICC after hepatectomy. Patients with high NPS require close follow-up, and improving NPS may prolong the survival time.

Antifungal activity and mechanism of oxanthromicin against Verticillium dahliae.

Oxanthromicin is an anthranone-type natural product isolated from Streptomyces sp. TRM 15522, which exhibits antifungal activity. However, the underlying mechanisms remain unclear. This study, therefore, aimed at investigating the mode of action of oxanthromicin against the phytopathogen Verticillium dahliae. We found that oxanthromicin substantially suppressed spore germination and mycelial growth in V. dahliae. Further, electron microscopy and staining with propidium iodide and Rhodamine 123 indicated that oxanthromicin causes cell membrane damage and induces changes in mitochondrial membrane potential. These findings suggest that oxanthromicin exhibits its antifungal activity by damaging fungal cell membranes. This discovery could potentially facilitate the development of oxanthromicin as a biological pesticide.

Ultrathin Ni-Fe MOF Nanosheets: Efficient and Durable Water Oxidation at High Current Densities.

Efficient, durable, and economical electrocatalysts are crucial for advancing energy technology by facilitating the oxygen evolution reaction (OER). Here, ultrathin Ni-Fe metal-organic skeleton (MOF) nanosheets were created in situ on nickel foam (NiFe-UMNs/NF). The catalyst exhibited excellent OER catalytical abilities, with only 269 mV overpotentials at 250 mA cm-2. Besides, when integrated with Pt/C/NF, NiFe-UMNs/NF held the potential for application in industrial alkaline water electrolysis with an initial voltage retention of approximately 86% following a continuous operation of 100 h at a current density of 250 mA cm-2. The super performance of the NiFe-UMNs/NF catalyst was attributed to ultrathin morphology, super hydrophilicity, and synergistic effects between Ni and Fe within the MOF. In situ Raman showed that NiFe-UMNs were converted to NiFeOOH as the active species in the OER process. Density functional theory revealed that iron doping accelerated the rate-determining step and reduced the OER reaction energy barrier. This work elucidated a promising electrocatalyst for OER and enriched the practical implementation of MOF materials.

Dual Photoredox/Nickel Catalysis Enables Diastereoselective Synthesis of Multisubstituted γ-Lactams Using Alkyl-GeMe3 as Radical Precursors.

Herein, we report a single-step, multicomponent approach to versatile γ-lactams through dual photoredox/nickel-catalyzed dicarbofunctionalization of α,ß-unsaturated γ-butyrolactam. This reaction utilized alkyl trimethylgermanium as a radical precursor and acyl chloride as the electrophile, demonstrating remarkable functional group compatibility.

Dinitrosyl Iron Complex-Derived Nanosized Zerovalent Iron (NZVI) as a Template for the Fe-Co Cracked NZVI: An Electrocatalyst for the Oxygen Evolution Reaction.

Nanosized zerovalent iron (NZVI) Fe@Fe3O4 with a core-shell structure derived from photocatalytic MeOH aqueous solution of dinitrosyl iron complex (DNIC) [(N3MDA)Fe(NO)2] (N3MDA = N,N-dimethyl-2-(((1-methyl-1H-imidazole-2-yl)methylene)amino)ethane-1-amine) (1-N3MDA), eosin Y, and triethylamine (TEA) is demonstrated. The NZVI Fe@Fe3O4 core shows a high percentage of zerovalent iron (Fe0 %) and is stabilized by a hydrophobic organic support formed through the photodegradation of eosin Y hybridized with the N3MDA ligand. In addition to its well-known reductive properties in wastewater treatment and groundwater remediation, NZVI demonstrates the ability to form heterostructures when it interacts with metal ions. In this research, Co2+ is employed as a model contaminant and reacted with NZVI Fe@Fe3O4 to result in the formation of a distinct Fe-Co heterostructure, cracked NZVI (CNZVI). The slight difference in the standard redox potentials between Fe2+ and Co2+, the magnetic properties of Co2+, and the absence of surface hydroxides of Fe@Fe3O4 enable NZVI to mildly reduce Co2+ and facilitate Co2+ penetration into the iron core. Taking advantage of the well-dispersed nature of CNZVI on an organic support, the reduction in particle size due to Co2+ penetration, and Fe-Co synergism, CNZVI is employed as a catalyst in the alkaline oxygen evolution reaction (OER). Remarkably, CNZVI exhibits a highly efficient OER performance, surpassing the benchmark IrO2 catalyst. These findings show the potential of using NZVI as a template for synthesizing highly efficient OER catalysts. Moreover, the study demonstrates the possibility of repurposing waste materials from water treatment as valuable resources for catalytic energy conversion, particularly in water oxidation processes.

Electronic Structure and Transformation of Dinitrosyl Iron Complexes (DNICs) Regulated by Redox Non-Innocent Imino-Substituted Phenoxide Ligand.

The coupled NO-vibrational peaks [IR νNO 1775 s, 1716 vs, 1668 vs cm-1 (THF)] between two adjacent [Fe(NO)2] groups implicate the electron delocalization nature of the singly O-phenoxide-bridged dinuclear dinitrosyliron complex (DNIC) [Fe(NO)2(µ-ON2Me)Fe(NO)2] (1). Electronic interplay between [Fe(NO)2] units and [ON2Me]- ligand in DNIC 1 rationalizes that "hard" O-phenoxide moiety polarizes iron center(s) of [Fe(NO)2] unit(s) to enforce a "constrained" π-conjugation system acting as an electron reservoir to bestow the spin-frustrated {Fe(NO)2}9-{Fe(NO)2}9-[·ON2Me]2- electron configuration (Stotal = 1/2). This system plays a crucial role in facilitating the ligand-based redox interconversion, working in harmony to control the storage and redox-triggered transport of the [Fe(NO)2]10 unit, while preserving the {Fe(NO)2}9 core in DNICs {Fe(NO)2}9-[·ON2Me]2- [K-18-crown-6-ether)][(ON2Me)Fe(NO)2] (2) and {Fe(NO)2}9-[·ON2Me] [(ON2Me)Fe(NO)2][PF6] (3). Electrochemical studies suggest that the redox interconversion among [{Fe(NO)2}9-[·ON2Me]2-] DNIC 3 ↔ [{Fe(NO)2}9-[ON2Me]-] ↔ [{Fe(NO)2}9-[·ON2Me]] DNIC 2 are kinetically feasible, corroborated by the redox shuttle between O-bridged dimerized [(µ-ONMe)2Fe2(NO)4] (4) and [K-18-crown-6-ether)][(ONMe)Fe(NO)2] (5). In parallel with this finding, the electronic structures of [{Fe(NO)2}9-{Fe(NO)2}9-[·ON2Me]2-] DNIC 1, [{Fe(NO)2}9-[·ON2Me]2-] DNIC 2, [{Fe(NO)2}9-[·ON2Me]] DNIC 3, [{Fe(NO)2}9-[ONMe]-]2 DNIC 4, and [{Fe(NO)2}9-[·ONMe]2-] DNIC 5 are evidenced by EPR, SQUID, and Fe K-edge pre-edge analyses, respectively.