Landscape of New Nuclease-Containing Antiphage Systems in Escherichia coli and the Counterdefense Roles of Bacteriophage T4 Genome Modifications.

Many phages, such as T4, protect their genomes against the nucleases of bacterial restriction-modification (R-M) and CRISPR-Cas systems through covalent modification of their genomes. Recent studies have revealed many novel nuclease-containing antiphage systems, raising the question of the role of phage genome modifications in countering these systems. Here, by focusing on phage T4 and its host Escherichia coli, we depicted the landscape of the new nuclease-containing systems in E. coli and demonstrated the roles of T4 genome modifications in countering these systems. Our analysis identified at least 17 nuclease-containing defense systems in E. coli, with type III Druantia being the most abundant system, followed by Zorya, Septu, Gabija, AVAST type 4, and qatABCD. Of these, 8 nuclease-containing systems were found to be active against phage T4 infection. During T4 replication in E. coli, 5-hydroxymethyl dCTP is incorporated into the newly synthesized DNA instead of dCTP. The 5-hydroxymethylcytosines (hmCs) are further modified by glycosylation to form glucosyl-5-hydroxymethylcytosine (ghmC). Our data showed that the ghmC modification of the T4 genome abolished the defense activities of Gabija, Shedu, Restriction-like, type III Druantia, and qatABCD systems. The anti-phage T4 activities of the last two systems can also be counteracted by hmC modification. Interestingly, the Restriction-like system specifically restricts phage T4 containing an hmC-modified genome. The ghmC modification cannot abolish the anti-phage T4 activities of Septu, SspBCDE, and mzaABCDE, although it reduces their efficiency. Our study reveals the multidimensional defense strategies of E. coli nuclease-containing systems and the complex roles of T4 genomic modification in countering these defense systems. IMPORTANCE Cleavage of foreign DNA is a well-known mechanism used by bacteria to protect themselves from phage infections. Two well-known bacterial defense systems, R-M and CRISPR-Cas, both contain nucleases that cleave the phage genomes through specific mechanisms. However, phages have evolved different strategies to modify their genomes to prevent cleavage. Recent studies have revealed many novel nuclease-containing antiphage systems from various bacteria and archaea. However, no studies have systematically investigated the nuclease-containing antiphage systems of a specific bacterial species. In addition, the role of phage genome modifications in countering these systems remains unknown. Here, by focusing on phage T4 and its host Escherichia coli, we depicted the landscape of the new nuclease-containing systems in E. coli using all 2,289 genomes available in NCBI. Our studies reveal the multidimensional defense strategies of E. coli nuclease-containing systems and the complex roles of genomic modification of phage T4 in countering these defense systems.

The s-p Nonhybrid Nature Causes Adaptive Superatomic States of Bismuth Clusters.

We report a joint experimental and theoretical study on the stability and reactivity of Bin + (n=5-33) clusters. The alternating odd-even effect on the reaction rates of Bin + clusters with NO is observed, and Bi7 + finds the most inertness. First-principles calculation results reveal that the lowest energy structures of Bi6-9 + exhibit quasi-spherical geometry pertaining to the jellium shell model; however, the Bin + (n≥10) clusters adopt assembly structures. The prominent stability of Bi7 + is associated with its highly symmetric structure and superatomic states with a magic number of 34e closed shell. For the first time, we demonstrate that the unique s-p nonhybrid feature in bismuth rationalizes the stability of Bi6-9 + clusters within the jellium model, by filling the 6s electrons into the superatomic orbitals (forming "s-band"). Interestingly, the stability of 18e "s-band" coincides with the compact structure for Bin + at n≤9 but assembly structures for n≥10, showing an accommodation of the s electrons to the geometric structure. The atomic p-orbitals also allow to form superatomic orbitals at higher energy levels, contributing to the preferable structures of tridentate binding units. We illustrate the s-p nonhybrid nature accommodates the structure and superatomic states of bismuth clusters.

Mouse nerve growth factor suppresses neuronal apoptosis in valproic acid-induced autism spectrum disorder rats by regulating the phosphoinositide-3-kinase/serine/threonine kinase signaling pathway.

BACKGROUND: Autism spectrum disorder (ASD) is a group of neurodevelopmental disorders characterized by deficits in social communication and restrictive behaviors. Mouse nerve growth factor (mNGF), a neurotrophic factor, is critical for neuronal growth and survival, and the mNGF treatment is considered a promising therapy for neurodegeneration. In light of this, we aimed to evaluate the effect of mNGF on neurological function in ASD. METHODS: An ASD rat model was established by intraperitoneal injection of valproic acid (VPA). Social behavior, learning, and memory of the rats were measured. TdT-mediated dUTP Nick-end labeling and Nissl assays were performed to detect neuronal apoptosis and survival in the hippocampus and prefrontal cortex. Apoptosis-related proteins and oxidative stress markers were detected. RESULTS: mNGF improved locomotor activity, exploratory behavior, social interaction, and spatial learning and memory in VPA-induced ASD rats. In the hippocampus and prefrontal cortex, mNGF suppressed neuronal apoptosis, increased the number of neurons, superoxide dismutase, and glutathione levels, and decreased reactive oxygen species, nitric oxide, TNF-α, and IL-1ß levels compared with the VPA group. In addition, mNGF increased the levels of Bcl-2, p-phosphoinositide-3-kinase (PI3K), and p-serine/threonine kinase (Akt), and decreased the levels of Bax and cleaved caspase-3, while the PI3K inhibitor LY294002 reversed these effects. CONCLUSION: These data suggest that mNGF suppressed neuronal apoptosis and ameliorated the abnormal behaviors in VPA-induced ASD rats, in part, by activating the PI3K/Akt signaling pathway.

GM1 Reduced the Symptoms of Autism Spectrum Disorder by Suppressing α-Syn Through Activating Autophagy.

Autism spectrum disorder (ASD) is a neurodevelopmental disorder that cannot be cured. The ASD rat model was developed in this study to demonstrate the role and mechanism of ganglioside GM1 (GM1). Rats were given valproic acid (VPA) to create the ASD rat model. The rats' behaviors were assessed using the Y-maze test, open-field test, three-chamber social interaction test, and Morris water maze test. Relative levels of glutathione (GSH), malondialdehyde (MDA), catalase (CAT), reactive oxygen species (ROS), and superoxide dismutase (SOD) were quantitated using relative kits. Nissl, TUNEL, immunofluorescent, and immunohistochemistry staining techniques were used. GM1 treatment improved the ASD model rats' behavior disorders, including locomotor activity and exploratory behavior, social interaction, learning and memory capacity, and repetitive behavior. Following GM1 injection, striatal neurons grew and apoptosis decreased. GM1 reduced the excessively elevated α-Syn in ASD by encouraging autophagy. The behavior disorder of ASD model rats was exacerbated by autophagy inhibition, which also increased α-Syn levels. By increasing autophagy, GM1 reduced α-Syn levels and, ultimately, improved behavioral abnormalities in ASD model rats.

TCHis mitigate oxidative stress and improve abnormal behavior in a prenatal valproic acid-exposed rat model of autism.

Troxerutin is known for its anti-inflammatory and antioxidative effects in nerve impairment. The purpose of this study is to investigate the effect of troxerutin and cerebroprotein hydrolysate injections (TCHis) on prenatal valproic acid (VPA)-exposed rats. The VPA was administered to pregnant rats on gestational day 12.5 to induce a model of autism. The offspring were given the treatment of TCHis on postnatal day (PND) 21-50. On PND 43-50, the behavioral analysis of offspring was performed after the treatment of TCHis for 1 h. On PND 50, the offspring were harvested and the brains were collected. The hippocampus and prefrontal cortex were isolated for relevant biochemical detections. The administration of TCHis increased pain sensitivity and improved abnormal social behaviors in prenatal VPA-exposed rats. Prenatal exposure of VPA induced neuronal loss and apoptosis, enhanced reactive oxygen species (ROS) production, and promoted oxidative stress in hippocampus and prefrontal cortex, whereas these effects were reversed by the postnatal treatment of TCHis. In addition, postnatal administration of TCHis ameliorated mitochondrial function in hippocampus and prefrontal cortex of prenatal VPA-exposed rats. This study concluded that postnatal treatment of TCHis reduced oxidative stress and ameliorated abnormal behavior in a prenatal VPA-induced rat model of autism.

Cyclotrimerization of Acetylene on Clusters Con+/Fen+/Nin+(n = 1-16).

Cyclotrimerization of acetylene to benzene has attracted significant interest, but the role of geometric and electronic effects on catalytic chemistry remains unclear. To fully elucidate the mechanism of catalytic acetylene-to-benzene conversion, we have performed a gas-phase reaction study of the Fen+, Con+, and Nin+ (n = 1-16) clusters with acetylene utilizing a customized mass spectrometer. It is found that their reactions with acetylene are initiated by C2H2 molecular adsorption and allow for dominant dehydrogenation with the relatively low partial pressure of the acetylene gas. However, at high acetylene concentrations, the cyclotrimerization in Mn+ + 3C2H2 (M = Fe, Co, Ni) becomes the dominant reaction channel. We demonstrate theoretically the favorable thermodynamics and reaction dynamics leading to the formation of the M+(C6H6) products. The results are discussed in terms of a cluster-catalyzed multimolecule synergistic effect and the cation-π interactions.

Probing Cluster-π Interactions between Cun- and C2H2/C2H4 for Gas Separation.

Copper-related materials are used for separation of ethylene and acetylene gases in chemistry; however, the precise mechanism regarding selectivity is elusive to be fully understood. Here, we have conducted a joint experimental and theoretical study of the Cun- (n = 7-30) clusters in reacting with C2H4 and C2H2. It is found that all of the Cun- clusters readily react with C2H2, giving rise to C2H2-addition products; however, Cu18- and Cu19- do not react with C2H4. We illustrate the superatomic stability of Cu18- and advocate its availability to separate C2H4 from C2H2. Further, we demonstrate the atomically precise mechanism regarding selectivity by fully unveiling the size-dependent cluster-π interactions.

Reactivity of Cobalt Clusters Con±/0 with Dinitrogen: Superatom Co6+ and Superatomic Complex Co5N6.

We report a joint experimental and theoretical study on the reactions of cobalt clusters (Con±/0) with nitrogen using the customized reflection time-of-flight mass spectrometer combined with a 177.3 nm deep-ultraviolet laser. Comparing to the behaviors of neutral Con (n = 2-30) and anionic Con- clusters (n = 7-53) which are relatively inert in reacting with nitrogen in the fast-flow tube, Con+ clusters readily react with nitrogen resulting in adducts of one or multiple N2 except Co6+ which stands firm in the reaction with nitrogen. Detailed quantum chemistry calculations, including the energetics, electron occupancy, and orbital analysis, well-explained the reasonable reactivity of Con+ clusters with nitrogen and unveiled the open-shell superatomic stability of Co6+ within a highly symmetric (D3d) structure. The D3d Co6+ bears an electron configuration of a half-filled superatomic 1P orbital (i.e., 1S21P3||1D0), a large α-highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gap, symmetric multicenter bonds, and reasonable electron delocalization pertaining to metallic aromaticity. Topology analysis by atom-in-molecule illustrates the interactions between Con+ and N2 corresponding to covalent bonds, but the Co-N interactions in cationic Co2+N2 and Co6+N2 clusters are apparently weaker than those in the other systems. In addition, we identify a superatomic complex Co5N6+ which exhibits similar frontier orbitals as the naked Co5+ cluster, but the alpha HOMO-LUMO gap is nearly double-magnified, which is consistent with the high-abundance peak of Co5N6+ in the experimental observation. The enhanced stability of such a ligand-coordinated superatomic complex Co5N6+, along with the superatom Co6+ with aromaticity, sheds light on special and general superatoms.

Vanadium Cluster Neutrals Reacting with Water: Superatomic Features and Hydrogen Evolution in a Fishing Mode.

Hydrogen evolution reaction (HER) is known as the heart of various energy storage and conversation systems of renewable energy sources. Here we observe the cluster reactions of a light transition metal, vanadium, with water in a gas-phase flow tube reactor. While HER products of V1 and V2 were not observed, the effective HER of water on neutral Vn (n ≥ 3) clusters reveals reasonable and size-dependent reactivity of the vanadium clusters. Superatomic features and reaction dynamics of V10, V13, and V16 are highlighted. Among the three typical superatoms, V10 and V16 exhibit an abnormal superatomic orbital energy level order, 1S|2S|1P|1D..., where the energy-reduced 2S orbital helps to accommodate the geometric structure and hence reinforce the cluster stability. In comparison, V13 bears a less symmetrical structure and reacts readily with water, allowing for recombination of a hydroxyl atom with an adsorbed hydrogen atom, akin to a fishing-mode HER process. The joint experimental and theoretical study on neutral Vn clusters clarifies the availability of superatom chemistry for transition metals and appeals further development of cluster theory based on electronic cloud/orbital analysis instead of simply counting the valence electrons. Also, we provide insights into the HER mechanism of metal clusters and propose a strategy to design new materials for portable fuel cells of hydrogen energy.

Combined the GABA-A and GABA-B receptor agonists attenuates autistic behaviors in a prenatal valproic acid-induced mouse model of autism.

Autism spectrum disorder (ASD) is an immensely challenging developmental disorder characterized primarily by two core behavioral symptoms of social communication deficits and restricted/repetitive behaviors. Investigating the etiological process and identifying an appropriate therapeutic target remain as formidable challenges to overcome ASD due to numerous risk factors and complex symptoms associated with the disorder. Among the various mechanisms that contribute to ASD, the maintenance of excitation and inhibition balance emerged as a key factor to regulate proper functioning of neuronal circuitry. In this study, we employed prenatally exposed to valproic acid (VPA) to establish a validated ASD mouse model and found impaired inhibitory gamma-aminobutyric acid (GABAergic) neurotransmission through a presynaptic mechanism in these model mice, which was accompanied with decreased GABA release and GABA-A and GABA-B receptor subunits expression. And acute administration of individual GABA-A or GABA-B receptor agonists partially reversed autistic-like behaviors in the model mice. Furthermore, acute administration of the combined GABA-A and GABA-B receptor agonists palliated sociability deficits, anxiety and repetitive behaviors in the animal model of autistic-like behaviors, demonstrating the therapeutic potential of above cocktail in the treatment of ASD.

Anionic Copper Clusters Reacting with NO: An Open-Shell Superatom Cu18.

Gas-phase metal clusters have been a subject of research interest for allowing reliable strategies to explore the stability and reactivity of materials at reduced sizes with atomic precision. Here we have prepared well-resolved copper cluster anions Cun- (n = 7-37) and systematically studied their reactivity with O2, NO, and CO. We found remarkable stability of an open-shell cluster Cu18-, which is comparable with the closed-shell clusters Cu17- and Cu19- within the picture of an electronic shell model. Even without having a magic number of valence electrons, intriguingly, the unpaired electron on the singly occupied molecular orbital of Cu18- is mainly contributed by the central copper atom, while the other 18 delocalized valence electrons occupy the lower-energy superatomic orbitals of the cluster. The finding of such an open-shell superatom Cu18-, with an electron configuration of 1S21P61D102S1||1F0, is interesting in the sense that an elementary cluster of coinage metal atoms could still behave as a superatom mimicking coinage metals like silver or gold atoms with an empty f orbital. The superatomic stability of this Cu18- cluster is reinforced by the unique electrostatic interaction between the Cu- core and Cu17 shell, which provides new insights into the chemistry of metal clusters.

Reactivity of Cobalt Clusters Con±/0 with Ammonia: Co3+ Cluster Catalysis for NH3 Dehydrogenation.

A customized reflection time-of-flight (Re-TOF) mass spectrometer combined with a 177 nm deep-ultraviolet laser has enabled us to observe well-resolved cobalt clusters Con±/0 and perform a comprehensive study of their reactivity with ammonia (NH3). The anions Con- are found to be inert, the neutrals allow the adsorption of multiple NH3 molecules, while the cationic Con+ clusters readily react with NH3 giving rise to dehydrogenation. However, incidental dehydrogenation of NH3 on Con+ is only observed for n ≥ 3. The dramatic charge- and size-dependent reactivities of Con±/0 clusters with NH3 are studied by the density functional theory (DFT)-calculation results of energetics, density of states, orbital interactions, and reaction dynamics. We illustrate the dehydrogenation from two NH3 molecules, where a significantly reduced transition-state energy barrier is found pertaining to the dimolecular co-catalysis effect. The reactivity of Co3+ with NH3 is illustrated showing effective catalysis for N-H dissociation to produce hydrogen applicable for designing ammonia fuel cells.

Charge-Sensitive Cluster-π Interactions Cause Altered Reactivity of Aln±,0 Clusters with Benzene: Enhanced Stability of Al13+Bz.

Utilizing the homemade reflection time-of-flight mass spectrometer (Re-TOFMS), here we report a comprehensive study of the reactivity of aluminum clusters Aln±,0 with molecular benzene in the gas-phase flow tube reactor. During the reactions with benzene, Aln+ clusters were found to be relatively more reactive than Aln0/-, and interestingly, the Al13+ cluster exhibited more reaction product than its neighboring Aln+ clusters. With an emphasis on Al13±,0 clusters, we have performed an in-depth study utilizing DFT calculations to unravel the diverse reactivity of aluminum clusters with benzene. It is revealed that the Al13+Bz cluster has a short Al-C distance and high binding energy, as well as an enlarged HOMO-LUMO gap in comparison with that of Al13+. This contrasts with Al130/- and Al15+, of which the HOMO-LUMO gaps are reduced when the cluster binds with a benzene molecule. Further, the cluster-π interactions between aluminum clusters and benzene are fully demonstrated via topological analysis, natural bonding orbital (NBO) analysis, and noncovalent interaction plots based on independent gradient model (IGM). The unique gyro-like structure of Al13+ and cluster-π interaction induce uneven redistribution of charges on the 13- atoms of Al13+, enabling a tight Al-C bond with strong electrostatic attraction and orbital interactions, which largely differs from the weak orbital overlap and electrostatic repulsion between benzene molecule and Al130/- clusters.

Hydrogen release from a single water molecule on Vn+ (3 ≤ n ≤ 30).

Water and its interactions with metals are closely bound up with human life, and the reactivity of metal clusters with water is of fundamental importance for the understanding of hydrogen generation. Here a prominent hydrogen evolution reaction (HER) of single water molecule on vanadium clusters Vn+ (3 ≤ n ≤ 30) is observed in the reaction of cationic vanadium clusters with water at room temperature. The combined experimental and theoretical studies reveal that the wagging vibrations of a V-OH group give rise to readily formed V-O-V intermediate states on Vn+ (n ≥ 3) clusters and allow the terminal hydrogen to interact with an adsorbed hydrogen atom, enabling hydrogen release. The presence of three metal atoms reduces the energy barrier of the rate-determining step, giving rise to an effective production of hydrogen from single water molecules. This mechanism differs from dissociative chemisorption of multiple water molecules on aluminium cluster anions, which usually proceeds by dissociative chemisorption of at least two water molecules at multiple surface sites followed by a recombination of the adsorbed hydrogen atoms.

Vitamin B1 and B12 mitigates neuron apoptosis in cerebral palsy by augmenting BDNF expression through MALAT1/miR-1 axis.

Through the roles of vitamin B1 and B12 in neuroprotection and in improving cerebral palsy symptoms have been previously noticed, the action mechanism is still unclear. This study aims to investigate the protective effect of vitamin B1 and B12 on neuron injury in cerebral palsy and to clarify the mechanism of vitamin B1 and B12 inhibiting neurons apoptosis, and to focus on the role of lncRNA MALAT1 in this process. In order to investigate the effect of vitamin B1 and B12 on neurons injury in vivo and on neuron apoptosis in vitro, we, respectively, introduced vitamin B1 and B12 into cerebral palsy rat and in apoptosis-induced N2A neurons by Oxygen Glucose Deprivation/reoxygenation (OGD/R). Our results demonstrated that vitamin B1 and B12 treatment improved the motor and memory functions and ameliorated the neurons injury in cerebral palsy rats. OGD/R treatment repressed the expression of MALAT1 and BDNF and the phosphorylation of PI3K and Akt, and enhanced the miR-1 expression, which were all reversed by vitamin B1 and B12 treatment in N2A neurons. Vitamin B1 and B12 inhibited miR-1 expression through MALAT1, promoted BDNF expression and activated PI3K/Akt signaling through the MALAT1/miR-1 axis. Vitamin B1 and B12 suppressed neuron apoptosis by up-regulating BDNF via MALAT1/miR-1 pathway. MALAT1 interference abolished the neuroprotective effect of vitamin B1 and B12 in cerebral palsy rats. Collectively, vitamin B1 and B12 up-regulates BDNF and its downstream PI3K/Akt signaling through MALAT1/miR-1 axis, thus suppressing neuron apoptosis and mitigating nerve injury in cerebral palsy rats.

LncRNA MIAT overexpression reduced neuron apoptosis in a neonatal rat model of hypoxic-ischemic injury through miR-211/GDNF.

OBJECTIVE: To investigate the underlying mechanism of lncRNA myocardial infarction-associated transcript (MIAT) in hypoxic-ischemic (HI)-induced neonatal cerebral palsy. MATERIALS AND METHODS: Neonatal rat model of HI injury was established to detect the motor function. LncRNA MIAT, miR-211, glial cell line-derived neurotrophic factor (GDNF) and caspase-3 expressions were measured by qRT-PCR or western blot. The apoptosis of Neuro2A cells was detected by flow cytometry. RNA immunoprecipitation (RIP) and RNA pull-down assays were performed to confirm the interaction between MIAT and miR-211. RESULTS: Compared with control group, lncRNA MIAT and GDNF were downregulated in striatal tissues of neonatal rats in HI group and oxygen glucose deprivation (OGD)-induced ischemic injury of Neuro2A cells, whereas miR-211 was up-regulated in striatal tissues of HI group and OGD-induced ischemic injury of Neuro2A cells. LncRNA MIAT interacted with miR-211, and lncRNA MIAT overexpression reduced neuron apoptosis through miR-211. Besides, GDNF expression was positively regulated by lncRNA MIAT and negatively regulated by miR-211 in Neuro2A cells. In vivo experiment proved MIAT promoted motor function and relieved HI injury. CONCLUSION: MIAT overexpression reduced apoptosis of Neuro2A cells through miR-211/GDNF, which relieved HI injury of neonatal rats.

Adsorption of O2 on Anionic Gold Clusters in the 0-1 nm Size Range: An Insight into the Electron Transfer Dynamics from Kinetic Measurements.

We systematically studied the adsorption of O2 on Au n- in the size range of 0-1 nm at low temperatures and determined new active sizes with n = 22, 24, 34, and 36. The kinetic measurements more clearly showed the correlation between the reactivity of Au n- with O2 and their electronic properties: the sizes with a closed electron shell are always inert, and the sizes with an unpaired electron can chemically adsorb one O2 molecule if their adiabatic detachment energies (ADEs) are lower than a threshold around 3.5 eV. This ADE threshold dividing the active and inert Au n- is independent of the clusters' sizes, global geometries, and local adsorption sites. According to the widely accepted electron transfer mechanism, this threshold could stand for the case in which the total energy of the Au n- and an O2 roughly equals that of the spin crossover point of the potential surfaces of Au n-O2- and Au n-···O2.

CO oxidation by the atomic oxygen on silver clusters: structurally dependent mechanisms generating free or chemically bonded CO2.

Atomic oxygen on silver is the crucial active species in many catalytic oxidation processes, while it is a big challenge to explore the relationship between its activity and molecular-level structures in condensed phases. We carried out kinetic measurements of the gas phase reactions between AgnO- (n = 1-8) and CO, in which the oxygen atoms were predicted to be terminal ones in AgO- and Ag2O-, in quasi-Ag-O-Ag chains for Ag3O- and Ag4O-, and on the two-fold or three-fold bridging positions in AgnO- (n = 5-8). All these oxygen species are highly reactive even at a low temperature of 150 K. AgnO- (n = 1, 2, 5-8) with terminal or bridging oxygen generate free CO2, while the quasi-chains of AgnO- (n = 3, 4) generate chemically bonded CO2 with a structural formula of Agn-CO2-Ag2- (n = 1, 2). Density functional theory calculations well interpreted all experimental observations, showing that no extra excitation energies are needed to initiate all these reactions. The structurally dependent mechanisms and the formation of chemically bonded CO2 revealed in this work help us to catch a glimpse of some important processes and intermediates on real silver catalysts.

Low-Temperature Disproportionation Reaction of NO on Au6-: A Mechanism Involving Three NO Molecules Promoted by the Negative Charge.

Conversion of NO to other nitrogen oxides is an elementary step in its catalytic removal processes. On coinage metal surfaces, two kinds of NO activation mechanisms have been well documented: the unimolecular dissociation of NO generates two adsorbed atoms, and the dissociation of an adsorbed (NO)2 unit generates an adsorbed O and a free N2O. In this work, we observed a disproportionation mechanism involving three NO molecules on Au6- at a very low temperature (150 K), in which an adsorbed (NO)2 reacts with a free NO forming an adsorbed NO2 and a free N2O. The density functional theory (DFT) calculations indicated that this disproportionation step is significantly exothermic and has a very low activation barrier. The charge distributions on the involved cluster complexes and the correlation between the activity and the electronic properties of Au6- indicate the important role of extra negative charge in all reaction steps. The disproportionation mechanism revealed in this work could possibly exist in the NO removal processes on real gold catalysts.