Tuning Local Coordination Environments of Manganese Single-Atom Nanozymes with Multi-Enzyme Properties for Selective Colorimetric Biosensing.

Single-atom nanozymes (SAzymes) are promising in next-generation nanozymes, nevertheless, how to rationally modulate the microenvironment of SAzymes with controllable multi-enzyme properties is still challenging. Herein, we systematically investigate the relationship between atomic configuration and multi-enzymatic performances. The constructed MnSA -N3 -coordinated SAzymes (MnSA -N3 -C) exhibits much more remarkable oxidase-, peroxidase-, and glutathione oxidase-like activities than that of MnSA -N4 -C. Based on experimental and theoretical results, these multi-enzyme-like behaviors are highly dependent on the coordination number of single atomic Mn sites by local charge polarization. As a consequence, a series of colorimetric biosensing platforms based on MnSA -N3 -C SAzymes is successfully built for specific recognition of biological molecules. These findings provide atomic-level insight into the microenvironment of nanozymes, promoting rational design of other demanding biocatalysts.

Computational Screening of Single-Metal-Atom Embedded Graphene-Based Electrocatalysts Stabilized by Heteroatoms.

Metal-N-doped carbon is a promising replacement for non-precious-metal catalysts such as Pt for the oxygen reduction reaction (ORR) in polymer electrolyte membrane fuel cells (PEMFCs). Although these materials have relatively good catalytic activity and are cost-effective, they still have lower ORR activity than Pt, and so improving their performances is greatly required. In this study, high-throughput screening was employed based on density functional theory (DFT) calculations to search for good candidate catalysts with a transition metal atom coordinated by heteroatoms (B, N, S, O, and P) embedded in a graphene structure. In addition, coordinating a transition metal with two types of heteroatom dopants in a graphene structure was also considered. We calculated the binding energies of ORR intermediates on metal-heteroatom-based graphene structures because they are known to play a key role in ORR. Based on our results, the new group of electrocatalysts imparts excellent ORR activity for PEMFCs, and we suggest that our approach provides useful insight into exploring other promising candidate catalysts.

Probing an Interfacial Ionic Pairing-Induced Molecular Dipole Effect in Ionovoltaic System.

A surficial molecular dipole effect depending on ion-molecular interactions has been crucial issues regarding to an interfacial potential, which can modulate solid electronic and electrochemical systems. Their properties near the interfacial region can be dictated by specific interactions between surface and adsorbates, but understandings of the corresponding details remain at interesting issues. Here, intuitive observations of an ionic pair formation-induced interfacial potential shifts are presented with an ionovoltaic system, and corresponding output signal variations are analyzed in terms of the surficial dipole changes on self-assembled monolayer. With aiding of photoelectron spectroscopies and density function theory simulation, the ionic pair formation-induced potential shifts are revealed to strongly rely on a paired molecular structure and a binding affinity of the paired ionic moieties. Chemical contributions to the binding event are interrogated in terms of polarizability in each ionic group and consistent with chaotropic/kosmotropic character of the ionic groups. Based on these findings, the ionovoltaic output changes are theoretically correlated with an adsorption isotherm reflecting the molecular dipole effect, thereby demonstrating as an efficient interfacial molecular probing method under electrolyte interfacing conditions.

Effective Screening Route for Highly Active and Selective Metal-Nitrogen-Doped Carbon Catalysts in CO2 Electrochemical Reduction.

To identify high-efficiency metal-nitrogen-doped (M-N-C) electrocatalysts for the electrochemical CO2 -to-CO reduction reaction (CO2 RR), a method that uses density functional theory calculation is presented to evaluate their selectivity, activity, and structural stability. Twenty-three M-N4 -C catalysts are evaluated, and three of them (M = Fe, Co, or Ni) are identified as promising candidates. They are synthesized and tested as proof-of-concept catalysts for CO2 -to-CO conversion. Different key descriptors, including the maximum reaction energy, differences of the *H and *CO binding energy (ΔG*H -ΔG*CO ), and *CO desorption energy (ΔG*CO→CO( g ) ), are used to clarify the reaction mechanism. These computational descriptors effectively predict the experimental observations in the entire range of electrochemical potential. The findings provide a guideline for rational design of heterogeneous CO2 RR electrocatalysts.

Highly Sensitive Piezocapacitive Sensor for Detecting Static and Dynamic Pressure Using Ion-Gel Thin Films and Conductive Elastomeric Composites.

A new class of simple and highly sensitive piezocapacitive sensors that are capable of detecting static and dynamic pressure changes is reported. The pressure sensor structure is formed by vertically sandwiching a sandpaper-molded carbon nanotube/poly(dimethylsiloxane) composite (CPC) dielectric layer between two ion-gel thin film electrodes. Such a capacitive sensor system enables the distinguishable detection of directional movement of applied pressure as well as static pressure variation by modulating ion distribution in the ion-gel thin films. The resulting capacitive pressure sensors exhibit high sensitivity (9.55 kPa-1), high durability, and low operating voltage (0.1 V). Our proposed pressure sensors are successfully applied as potential platforms for monitoring human physiological signals and finger sliding motions in order to demonstrate their capability for practical usage. The outstanding sensor performance of the pressure sensors can permit applications in wearable electronic devices for human-machine connecting platforms, health care monitoring systems, and artificial skin.

Influence of deglaciation on microbial communities in marine sediments off the coast of Svalbard, Arctic Circle.

Increases in global temperatures have been shown to enhance glacier melting in the Arctic region. Here, we have evaluated the effects of meltwater runoff on the microbial communities of coastal marine sediment located along a transect of Temelfjorden, in Svalbard. As close to the glacier front, the sediment properties were clearly influenced by deglaciation. Denaturing gradient gel electrophoresis profiles showed that the sediment microbial communities of the stations of glacier front (stations 188-178) were distinguishable from that of outer fjord region (station 176). Canonical correspondence analysis indicated that total carbon and calcium carbonate in sediment and chlorophyll a in bottom water were key factors driving the change of microbial communities. Analysis of 16S rRNA gene clone libraries suggested that microbial diversity was higher within the glacier-proximal zone (station 188) directly affected by the runoffs than in the outer fjord region. While the crenarchaeotal group I.1a dominated at station 176 (62%), Marine Benthic Group-B and other Crenarchaeota groups were proportionally abundant. With regard to the bacterial community, alpha-Proteobacteria and Flavobacteria lineages prevailed (60%) at station 188, whereas delta-Proteobacteria (largely sulfate-reducers) predominated (32%) at station 176. Considering no clone sequences related to sulfate-reducers, station 188 may be more oxic compared to station 176. The distance-wise compositional variation in the microbial communities is attributable to their adaptations to the sediment environments which are differentially affected by melting glaciers.

Reichenbachiella faecimaris sp. nov., isolated from a tidal flat, and emended descriptions of the genus Reichenbachiella and Reichenbachiella agariperforans.

A taxonomic study was carried out on two bacterial strains, PCP11(T) and PCP104, isolated from a tidal flat of the Yellow Sea, Korea. Comparative 16S rRNA gene sequence studies showed that these strains belonged to the family Cytophagaceae, phylum Bacteroidetes. Strains PCP11(T) and PCP104 shared 99.4 % sequence similarity and were related most closely to Reichenbachiella agariperforans KMM 3525(T) (95.8 and 96.0 % sequence similarity, respectively). Members of the genera Fulvivirga, Roseivirga, Fabibacter and Marinoscillum were the next closest relatives of the new isolates, with sequence similarities ≤ 91 %. The two isolates were Gram-staining-negative, strictly aerobic, gliding bacteria. They grew in the presence of 1-5 % NaCl, at pH 5.5-8.5 and at 4-35 °C. Strains PCP11(T) and PCP104 shared a number of physiological and biochemical properties with Reichenbachiella agariperforans KMM 3525(T), but they differed from this strain in the hydrolysis of biopolymers and in the production of carotenoid and flexirubin-type pigments. Both strains possessed iso-C(15 : 0), summed feature 4 (C(16 : 1)ω7c and/or iso-C(15 : 0) 2-OH) and C(15 : 0) as major cellular fatty acids. The major respiratory quinone was menaquinone 7 (MK-7). The G+C contents of the genomic DNA of strains PCP11(T) and PCP104 were 39.6 and 41.9 mol%, respectively. On the basis of phenotypic data and phylogenetic inference, it is proposed that the two isolates represent a novel species, Reichenbachiella faecimaris sp. nov., with strain PCP11(T) ( = KACC 14523(T)  = JCM 16588(T)) as the type strain. Emended descriptions of the genus Reichenbachiella and Reichenbachiella agariperforans are also proposed.

Cultivation of autotrophic ammonia-oxidizing archaea from marine sediments in coculture with sulfur-oxidizing bacteria.

The role of ammonia-oxidizing archaea (AOA) in nitrogen cycling in marine sediments remains poorly characterized. In this study, we enriched and characterized AOA from marine sediments. Group I.1a crenarchaea closely related to those identified in marine sediments and "Candidatus Nitrosopumilus maritimus" (99.1 and 94.9% 16S rRNA and amoA gene sequence identities to the latter, respectively) were substantially enriched by coculture with sulfur-oxidizing bacteria (SOB). The selective enrichment of AOA over ammonia-oxidizing bacteria (AOB) is likely due to the reduced oxygen levels caused by the rapid initial growth of SOB. After biweekly transfers for ca. 20 months, archaeal cells became the dominant prokaryotes (>80%), based on quantitative PCR and fluorescence in situ hybridization analysis. The increase of archaeal 16S rRNA gene copy numbers was coincident with the amount of ammonia oxidized, and expression of the archaeal amoA gene was observed during ammonia oxidation. Bacterial amoA genes were not detected in the enrichment culture. The affinities of these AOA to oxygen and ammonia were substantially higher than those of AOB. [(13)C]bicarbonate incorporation and the presence and activation of genes of the 3-hydroxypropionate/4-hydroxybutyrate cycle indicated autotrophy during ammonia oxidation. In the enrichment culture, ammonium was oxidized to nitrite by the AOA and subsequently to nitrate by Nitrospina-like bacteria. Our experiments suggest that AOA may be important nitrifiers in low-oxygen environments, such as oxygen-minimum zones and marine sediments.

Marinobacterium maritimum sp. nov., a marine bacterium isolated from Arctic sediment.

A Gram-negative, aerobic, rod-shaped, motile, marine bacterium, strain AR11(T), was isolated from Arctic marine sediment. Strain AR11(T) grew with 0.5-7 % NaCl and at 7-37 degrees C and pH 5.5-9.0. It utilized propionate, 3-hydroxybenzoate, l-proline, acetate, d- and l-lactate, l-alanine, malate and phenylacetic acid. Alkaline phosphatase, esterase lipase (C8), leucine arylamidase and acid phosphatase activity tests were positive. Acid was produced from 5-ketogluconate and aesculin. Strain AR11(T) possessed C(16 : 0) (22.0 %), summed feature 4 (C(16 : 1)omega7c and/or iso-C(15 : 0) 2-OH; 28.1 %) and summed feature 7 (one or more of C(18 : 1)omega7c, omega9t and omega12t; 34.0 %) as the major cellular fatty acids. The major ubiquinone was Q-8. Comparative 16S rRNA gene sequence studies showed that strain AR11(T) belonged to the Gammaproteobacteria and was most closely related to Marinobacterium stanieri DSM 7027(T), Marinobacterium halophilum mano11(T) and Marinobacterium georgiense KW-40(T) (97.8, 97.0 and 96.7 % similarity, respectively). The G+C content of the genomic DNA of strain AR11(T) was 57.9 mol%. DNA-DNA relatedness data indicated that strain AR11(T) represented a distinct species that was separated from M. stanieri DSM 7027(T), M. halophilum KCTC 12240(T) and M. georgiense JCM 21667(T). On the basis of evidence from this polyphasic study, it is proposed that strain AR11(T) (=KCTC 22254(T)=JCM 15134(T)) represents the type strain of a novel species, Marinobacterium maritimum sp. nov.

[Relapse rates of ulcerative colitis in remission and factors related to relapse].

BACKGROUND/AIMS: Ulcerative colitis (UC) is a chronic inflammatory bowel disease with heterogeneous clinical features. Data on the disease course and prognosis of UC patients who have been regularly treated are lacking. We aimed to investigate relapse rates of UC in remission and factors related to relapse. METHODS: We retrospectively analyzed clinical courses of 84 patients (43 males, median age 43 years, ranged 20-73 years) diagnosed as UC at Ajou University Hospital between January 1997 and December 2005 based on clinical, endoscopic and pathologic findings, and who were regularly followed for at least one year after the remission. RESULTS: Study subjects consisted of 32 proctitis (38%), 21 left-sided colitis (25%), and 31 subtotal or total colitis (37%). Of 84 patients, relapse was observed in 52 patients (62%) during the follow-up period (ranged 1-9 years). The relapse rate was 24%, 41%, 51%, 65%, 71%, and 79% at 1 year, 2 years, 3 years, 4 years, 5 years and 6 years, respectively. Among sex, age, hemoglobin, ESR, and the extent of disease on admission, decrease of hemoglobin level was the only independent factor related to relapse (odds ratio=2.67, 95% CI (1.32-5.42), p<0.01). CONCLUSIONS: In Korea, relapse of UC in remission is not rare. Decrease of hemoglobin level is an independent risk factor related to its relapse, while the extent of disease is not.

Microeukaryotic diversity in marine environments, an analysis of surface layer sediments from the East Sea.

Molecular techniques, based on clone library of 18S rRNA gene, were employed to ascertain the diversity of microeukaryotic organisms in sediments from the East Sea. A total of 261 clones were recovered from surface sediments. Most of the clone sequences (90%) were affiliated with protists, dominated by Ciliates (18%) and Dinoflagellates (19%) of Alveolates, phototrophic Stramenopiles (11%), and Cercozoa (20%). Many of the clones were related to uncultivated eukaryotes clones retrieved from anoxic environments with several highly divergent 18S rRNA gene sequences. However, no clones were related to cultivated obligate anaerobic protists. Protistan communities between subsurface layers of 1 and 9 cm shared 23% of total phylotypes which comprised 64% of total clones retrieved. Analysis of diversity indices and rarefaction curve showed that the protistan community within the 1 cm layer exhibited higher diversity than the 9 cm layer. Our results imply that diverse protists remain to be uncovered within marine benthic environments.

Comparative analysis of archaeal 16S rRNA and amoA genes to estimate the abundance and diversity of ammonia-oxidizing archaea in marine sediments.

Considering their abundance and broad distribution, non-extremophilic Crenarchaeota are likely to play important roles in global organic and inorganic matter cycles. The diversity and abundance of archaeal 16S rRNA and putative ammonia monooxygenase alpha-subunit (amoA) genes were comparatively analyzed to study genetic potential for nitrification of ammonia-oxidizing archaea (AOA) in the surface layers (0-1 cm) of four marine sediments of the East Sea, Korea. After analysis of a 16S rRNA gene clone library, we found various archaeal groups that include the crenarchaeotal group (CG) I.1a (54.8%) and CG I.1b (5.8%), both of which are known to harbor ammonia oxidizers. Notably, the 16S rRNA gene of CG I.1b has only previously been observed in terrestrial environments. The 16S rRNA gene sequence data revealed a distinct difference in archaeal community among sites of marine sediments. Most of the obtained amoA sequences were not closely related to those of the clones retrieved from estuarine sediments and marine water columns. Furthermore, clades of unique amoA sequences were likely to cluster according to sampling sites. Using real-time PCR, quantitative analysis of amoA copy numbers showed that the copy numbers of archaeal amoA ranged from 1.1x10(7) to 4.9x10(7) per gram of sediment and were more numerous than those of bacterial amoA, with ratios ranging from 11 to 28. In conclusion, diverse CG I.1a and CG I.1b AOA inhabit surface layers of marine sediments and AOA, and especially, CG I.1a are more numerous than other ammonia-oxidizing bacteria.