Lithium-ion battery electrode properties of hydrogen boride.

Recently, hydrogen boride (HB) with a pseudo-two-dimensional sheet structure was successfully synthesized, and it is theoretically predicted to have high potential as a negative electrode material for alkali metal ion batteries, making it a promising new candidate. This study represents the first experimental examination of the negative electrode properties of HB. HB was synthesized via cation exchange from MgB2. The confirmation of HB synthesis was achieved through various spectroscopic experiments, including synchrotron radiation X-ray diffraction and X-ray photoelectron spectroscopy, in addition to direct observation using transmission electron microscopy. The HB electrode was prepared by mixing the HB powder sample with conductive additive carbon black and a polymer binder. A test cell was assembled with the HB electrode as the working electrode, and lithium metal as the counter and reference electrodes, and its battery electrode properties were evaluated. Although reversible charge-discharge curves with good reversibility were observed, the reversible capacity was 100 ± 20 mA h g-1 which is significantly smaller than the theoretical predictions. Nitrogen gas adsorption experiments were performed on the HB powder sample to determine the specific surface area indicating that the HB sheets were stacked together. It is plausible to consider that this stacking structure led to a reduced lithium-ion storage capacity compared to the theoretical predictions.

An ependymin-related blue carotenoprotein decorates marine blue sponge.

Marine animals display diverse vibrant colors, but the mechanisms underlying their specific coloration remain to be clarified. Blue coloration is known to be achieved through a bathochromic shift of the orange carotenoid astaxanthin (AXT) by the crustacean protein crustacyanin, but other examples have not yet been well investigated. Here, we identified an ependymin (EPD)-related water-soluble blue carotenoprotein responsible for the specific coloration of the marine blue sponge Haliclona sp. EPD was originally identified in the fish brain as a protein involved in memory consolidation and neuronal regeneration. The purified blue protein, designated as EPD-related blue carotenoprotein-1, was identified as a secreted glycoprotein. We show that it consists of a heterodimer that binds orange AXT and mytiloxanthin and exhibits a bathochromic shift. Our crystal structure analysis of the natively purified EPD-related blue carotenoprotein-1 revealed that these two carotenoids are specifically bound to the heterodimer interface, where the polyene chains are aligned in parallel to each other like in ß-crustacyanin, although the two proteins are evolutionary and structurally unrelated. Furthermore, using reconstitution assays, we found that incomplete bathochromic shifts occurred when the protein bound to only AXT or mytiloxanthin. Taken together, we identified an EPD in a basal metazoan as a blue protein that decorates the sponge body by binding specific structurally unrelated carotenoids.

Symbiosis of Carpenter Bees with Uncharacterized Lactic Acid Bacteria Showing NAD Auxotrophy.

Eusocial bees (such as honey bees and bumble bees) harbor core gut microbiomes that are transmitted through social interaction between nestmates. Carpenter bees are not eusocial; however, recent microbiome analyses found that Xylocopa species harbor distinctive core gut microbiomes. In this study, we analyzed the gut microbiomes of three Xylocopa species in Japan between 2016 and 2021 by V1 to V2 region-based 16S rDNA amplicon sequencing, and 14 candidate novel species were detected based on the full-length 16S rRNA gene sequences. All Xylocopa species harbor core gut microbiomes consisting of primarily lactic acid bacteria (LAB) that were phylogenetically distant from known species. Although they were difficult to cultivate, two LAB species from two different Xylocopa species were isolated by supplementing bacterial culture supernatants. Both genomes exhibited an average LAB genome size with a large set of genes for carbohydrate utilization but lacked genes to synthesize an essential coenzyme NAD, which is unique among known insect symbionts. Our findings of phylogenetically distinct core LAB of NAD auxotrophy reflected the evolution of Xylocopa-restricted bacteria retention and maintenance through vertical transmission of microbes during solitary life. We propose five candidate novel species belonging to the families Lactobacillaceae and Bifidobacteriaceae, including a novel genus, and their potential functions in carbohydrate utilization. IMPORTANCE Recent investigations found unique microbiomes in carpenter bees, but the description of individual microbes, including isolation and genomics, remains largely unknown. Here, we found that the Japanese Xylocopa species also harbor core gut microbiomes. Although most of them were difficult to isolate a pure colony, we successfully isolated several strains. We performed whole-genome sequencing of the isolated candidate novel species and found that the two Lactobacillaceae strains belonging to the Xylocopa-specific novel LAB clade lack the genes for synthesizing NAD, a coenzyme central to metabolism in all living organisms. Here, we propose a novel genus for the two LAB species based on very low 16S rRNA gene sequence similarities and genotypic characters.

Single-walled carbon nanotubes as a reducing agent for the synthesis of a Prussian blue-based composite: a quartz crystal microbalance study.

We investigated the synthesis mechanism of Prussian blue (PB) crystals supported on single-walled carbon nanotubes (SWCNTs), by performing in situ quartz crystal microbalance (QCM) measurements to probe the change in the electrode mass during the reaction, and using photoirradiation at designated stages of the process. We found that in contrast to existing hypotheses, light irradiation played no role in the synthesis process of Prussian blue on SWCNTs. On the other hand, the number of electrons transferred per one mole of the obtained product, and the number of electrons transferrable from SWCNTs, calculated from the density of states (DOS) of the SWCNTs in the sample, both favor the hypothesis of the reaction being triggered by direct electron transfer from SWCNTs to Fe3+, which occurs because of the energy difference between the Fermi level of SWCNTs and redox potential of Fe3+ ions.

Major Carotenoids of Meiothermus ruber Are Deinoxanthin Glucoside Esters, Not Meiothermoxanthin Glucoside Esters.

Meiothermus ruber DSMZ 1279T was isolated from a hot spring in Kamchatka and was red in color. The major carotenoid present was reported to be 1'-(ß-d-glucopyranosyloxy)-3,4,3',4'-tetradehydro-1',2'-dihydro-ß,ψ-caroten-2-one after saponification (Burgess et al. J. Nat. Prod. 1999, 62, 859-863). In this study, we purified the major carotenoids in this species without saponification. We then reidentified the major carotenoids present using spectroscopic data, including electronic circular dichroism (ECD), 1H NMR, rotating-frame nuclear Overhauser effect spectroscopy (ROESY), 13C NMR, heteronuclear single-quantum correlation spectroscopy (HSQC), heteronuclear multiple-bond correlation spectroscopy (HMBC), and MS, and enzymatic hydrolysis of fatty acid moieties and found deinoxanthin glucoside iso fatty acid esters. The bound fatty acids present included four iso types, and their composition differed from cellular lipids. Moreover, the previously identified carotenoid glucoside was a saponification artifact of deinoxanthin glucoside esters. Ketomyxocoxanthin glucoside esters and 1'-hydroxytorulene glucoside esters were also present. On the basis of the identification of carotenoids and the whole genome sequence of M. ruber, we propose a carotenoid biosynthetic pathway and note the corresponding genes.

Characteristics of falls occurring during rehabilitation in an acute care hospital in older and non-older patients: A retrospective cohort study.

Introduction: Although falls are often reported in hospitals and are common in older individuals, no reports on falls during rehabilitation exist. This study evaluated patients with falls occurring during rehabilitation and identified the characteristics of older and non-older patients. Materials and methods: Our study retrospectively analyzed reports of falls occurring during rehabilitation at a university hospital from April 1, 2020 to March 31, 2022. The survey items included the number of falls in the hospital as a whole and during rehabilitation, age, gender, modified Rankin Scale (mRS) before admission and at the time of fall, functional independence measure (FIM) at admission, patient communication status at the time of fall, and whether a therapist was near the patient. Patients aged ≥ 65 were considered older; aged ≤ 64, non-older; and those with the same age, gender, and clinical department, randomly selected as non-falling patients. Results: Thirty-five falls occurred during rehabilitation (14 in the non-older and 21 in the older patients), significantly lower than the 945 for the entire hospital, without any significant difference between non-older and older patients. No significant differences in mRS before admission and FIM at admission were noted for both groups in comparison with the non-falling patient group. Furthermore, gender, mRS, FIM, good communication status, and presence of therapist near the patient were similar between non-older and older patients (non-older 71.4%, older 52.4%). Most falls were minor adverse events that did not require additional treatment. Conclusion: The rate of falls during rehabilitation was much lower than that during hospitalization, and many falls had minimal impact on the patient. It was also difficult to predict falls in daily life and communication situations, and there was no difference in characteristics between the older and non-older groups. Since more than half of the falls occurred during training with the therapist, it is necessary to reconsider the training content.

Investigation of Adverse Events Occurring during Rehabilitation in Acute Care Hospital.

Adverse events (AEs) during intensive care unit (ICU) rehabilitation and serious AEs during acute care hospital stays have been reported previously. However, no AEs have been reported for all patients needing rehabilitation in a non-ICU setting at an acute care hospital. This study aimed to investigate all AEs during acute-phase rehabilitation. Reports of AEs occurring during acute-phase rehabilitation in a university hospital from 1 April 2021 to 31 March 2022 were retrospectively analyzed. Minor and severe AEs were defined as those that did not require new treatment and those that required intensive treatment and/or prolonged hospitalization, respectively. There were 113 incidences of AEs during rehabilitation. The majority of AEs were minor (93.8%) and did not require new treatment. Only one serious AE was documented. The most common AEs were peripheral intravenous tube removal, decreased level of consciousness, poor mood due to low blood pressure, and falling down. There was no significant correlation between years of experience and the frequency of AEs. The neurosurgery department had the highest cases of AEs. Physical, occupational, and speech-language-hearing therapists had different characteristics and experiences of AEs. Risk management strategies should consider exercise load and targeted disorders due to differences in therapists' specialties.

One-step and room-temperature fabrication of carbon nanocomposites including Ni nanoparticles for supercapacitor electrodes.

With the increasing importance of power storage devices, demand for the development of supercapacitors possessing both rapid reversible chargeability and high energy density is accelerating. Here we propose a simple process for the room temperature fabrication of pseudocapacitor electrodes consisting of a faradaic redox reaction layer on a metallic electrode with an enhanced surface area. As a model metallic electrode, an Au foil was irradiated with Ar+ ions with a simultaneous supply of C and Ni at room temperature, resulting in fine metallic Ni nanoparticles dispersed in the carbon matrix with local graphitization on the ion-induced roughened Au surface. A carbon layer including fine Ni nanoparticles acted as an excellent faradaic redox reaction layer and the roughened surface contributed to an increase in surface area. The fabricated electrode, which included only 14 µg cm-2 of Ni, showed a stored charge ability three times as large as that of the bulky Ni foil. Thus, it is believed that a carbon layer including Ni nanoparticles fabricated on the charge collective electrode with an ion-irradiation method is promising for the development of supercapacitors from the viewpoints of the reduced use of rare metal and excellent supercapacitor performance.

Follow-Up Study of Subdermal Low-Echoic Lesions in the Ischial Region in Wheelchair Users With Spinal Cord Injuries.

Objective: To follow up patients with spinal cord injuries with subdermal low-echoic lesions in the ischial region for abnormalities after 1 year. Design: A retrospective cohort study. Setting: A Japanese rehabilitation center. Participants: We included patients with chronic spinal cord injuries and subdermal low-echoic lesions who underwent routine inspection and palpation examinations (n = 7). Interventions: Education on pressure injury and instruction on pressure relief and seating was provided and the patients were followed up for abnormalities after 1 year. Self-reports were obtained on wheelchair sitting time, and interface pressure was recorded while the patients were seated on the wheelchair. Interface pressure measurements at the bilateral ischial regions were recorded with a force-sensitive application pressure mapping system. Outcome Measures: The primary outcome was the presence of subdermal low-echoic lesions in the bilateral ischial regions on ultrasonography at the 1-year follow-up examination. Secondary outcomes included wheelchair sitting time and interface pressure in the bilateral ischial regions. Results: Of the 10 areas that showed subdermal low-echoic lesions on ultrasonography, nine had improved after 1 year. One area that did not improve was an open wound. At the follow-up examination, the pressure duration was reduced in all patients, and the interface pressure could be reduced in 5/7 patients. Conclusions: This is the first study to follow up with patients having spinal cord injuries and subdermal low-echoic lesions in the ischial region using ultrasonography. The low-echoic lesions improved within 1 year by reducing the pressure duration and interface pressure. Pressure injury prevention in patients with spinal cord injuries relies on the early detection of skin abnormalities, and education and instruction to change self-management behaviors are recommended.

Distribution of the Water-Soluble Astaxanthin Binding Carotenoprotein (AstaP) in Scenedesmaceae.

Photooxidative stress-inducible water-soluble astaxanthin-binding proteins, designated as AstaP, were identified in two Scenedesmaceae strains, Coelastrella astaxanthina Ki-4 and Scenedesmus obtusus Oki-4N; both strains were isolated under high light conditions. These AstaPs are classified as a novel family of carotenoprotein and are useful for providing valuable astaxanthin in water-soluble form; however, the distribution of AstaP orthologs in other microalgae remains unknown. Here, we examined the distribution of AstaP orthologs in the family Scenedesmaceae with two model microalgae, Chlamydomonas reinhardtii and Chlorella variabilis. The expression of AstaP orthologs under photooxidative stress conditions was detected in cell extracts of Scenedesmaceae strains, but not in model algal strains. Aqueous orange proteins produced by Scenedesmaceae strains were shown to bind astaxanthin. The protein from Scenedesmus costatus SAG 46.88 was purified. It was named ScosAstaP and found to bind astaxanthin. The deduced amino acid sequence from a gene encoding ScosAstaP showed 62% identity to Ki-4 AstaP. The expression of the genes encoding AstaP orthologs was shown to be inducible under photooxidative stress conditions; however, the production amounts of AstaP orthologs were estimated to be approximately 5 to 10 times lower than that of Ki-4 and Oki-4N.

One-step synthesis of visible light CO2 reduction photocatalyst from carbon nanotubes encapsulating iodine molecules.

We describe the synthesis and visible-light CO2 photoreduction catalytic properties of a three-component composite consisting of AgI, AgIO3, and single-walled carbon nanotubes (SWCNTs). The catalyst is synthesized by immersing SWCNTs encapsulating iodine molecules in AgNO3 aqueous solution, during which neutral iodine (I2) molecules encapsulated in SWCNTs transform disproportionately to I5+ (AgIO3) and I- (AgI), as revealed from the characterization of the composite by Raman spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. In addition, photoirradiation experiments using a solar-simulator (AM1.5G) showed that the obtained three-component composite works as a CO2 photoreduction catalyst under visible light despite the wide band gap of AgIO3, suggesting possible transfer of the visible light-excited electron from AgI via SWCNTs.

Switching of alternative electrochemical charging mechanism inside single-walled carbon nanotubes: a quartz crystal microbalance study.

We probed electrochemical ion storage in single-walled carbon nanotubes (SWCNTs) of different diameters in two different organic electrolytes using electrochemical quartz crystal microbalance (EQCM) tracking. The measurements showed that charge storage probed by cyclic voltammetry did not deteriorate when steric effects seemed to hinder the accessibility of counter-ions into SWCNTs, and instead proceeded predominantly by co-ion desorption, as was shown by the decrease in the electrode mass probed by EQCM. The dominant mechanism correlated with the SWCNT diameter/ion size ratio; counter-ion adsorption dominated in the whole potential range when the diameter of SWCNTs was comparable to the size of the largest ion, whereas for larger diameters the charge increase coincided with a decrease in the electrode mass, indicating the dominance of co-ion desorption. The dominance of co-ion desorption was not observed in activated carbon, nor was it previously reported for other carbon materials, and is likely switched on because the carrier density of SWCNT increases with applied potential, and maintains the electrode capacity by co-ion desorption to overcome the steric hindrances to counter-ion adsorption.

Relationship between ultrasonographically low-echoic lesions under the skin, wheelchair sitting time, and interface pressure on ischial region in individuals with chronic spinal cord injury.

Objective: To determine the relationship between physical findings, wheelchair sitting time, and interface pressure on ischial region in subjects with spinal cord injury (SCI).Design: Cross-sectional study.Setting: Rehabilitation center in Japan.Participants: Manual wheelchair users with chronic SCI (n = 45).Interventions: Pressure ulcers (PU) were diagnosed by inspection, palpation, and ultrasonography. Self-reports were obtained on wheelchair sitting time and pressure mapping was recorded while the subject was seated on the wheelchair.Outcome measures: Subjects were divided into those with ultrasonographically low-echoic lesions (PU-positive group, n = 11) and no such lesions (PU-negative group, n = 34). Outcome measures included wheelchair sitting time and interface pressure at bilateral ischial regions.Results: Using ultrasonography, 13 low-echoic lesions were identified in 11 subjects of the PU-positive group. The pressure duration was longer and interface pressure was significantly higher in subjects of the PU-positive group compared with those of the PU-negative group (P < 0.05 and P < 0.001, respectively).Conclusions: This is the first study to evaluate the interrelationship between physical findings, sitting time, and ultrasonographically measured interface pressure on ischial region area in subjects with spinal cord injury. To prevent pressure ulcers, we recommend avoidance of prolonged wheelchair sitting and measures that can reduce the interface pressure. These variables should be carefully tailored to the needs of the individual subjects with SCI.

Photooxidative stress-inducible orange and pink water-soluble astaxanthin-binding proteins in eukaryotic microalga.

Lipid astaxanthin, a potent antioxidant known as a natural sunscreen, accumulates in eukaryotic microalgae and confers photoprotection. We previously identified a photooxidative stress-inducible water-soluble astaxanthin-binding carotenoprotein (AstaP) in a eukaryotic microalga (Coelastrella astaxanthina Ki-4) isolated from an extreme environment. The distribution in eukaryotic microalgae remains unknown. Here we identified three novel AstaP orthologs in a eukaryotic microalga, Scenedesmus sp. Oki-4N. The purified proteins, named AstaP-orange2, AstaP-pink1, and AstaP-pink2, were identified as secreted fasciclin proteins with potent 1O2 quenching activity in aqueous solution, which are characteristics shared with Ki-4 AstaP. Nonetheless, the absence of glycosylation in the AstaP-pinks, the presence of a glycosylphosphatidylinositol (GPI) anchor motif in AstaP-orange2, and highly acidic isoelectric points (pI = 3.6-4.7), differed significantly from that of AstaP-orange1 (pI = 10.5). These results provide unique examples on the use of water-soluble forms of astaxanthin in photosynthetic organisms as novel strategies for protecting single cells against severe photooxidative stresses.

Preoperative In-Hospital Rehabilitation Improves Physical Function in Patients with Pancreatic Cancer Scheduled for Surgery.

Low preoperative physical function in cancer patients is associated with postoperative complications; however, there have been no reports on the benefits of in-hospital preoperative rehabilitation on preoperative physical function in patients with pancreatic cancer. Therefore, the aim of this study was to quantitatively determine the effects of preoperative in-hospital rehabilitation provided under the supervision of a physiotherapist, on preoperative physical function in patients with pancreatic cancer. The study subjects were 26 patients (15 males, 11 females; age 71.2 ± 8.5 years, range: 51-87 years), including four patients with preoperative chemotherapy, scheduled for surgery for pancreatic cancer. Muscle strengthening exercises and aerobic exercises were conducted 11.9 ± 5.1 days prior to surgery. Cardiopulmonary exercise testing, 6-minute walk distance, and the Functional Independence Measure score were measured before and after the rehabilitation program. We also investigated the relation between the rehabilitation program and incidence of postoperative complications. All 26 study patients completed the preoperative rehabilitation program and no adverse events were noted. Peak oxygen uptake during cardiopulmonary exercise testing and 6-minute walk distance increased significantly after the rehabilitation program. The Functional Independence Measure score remained constant throughout the intervention. No wound infection, delirium, deep vein thrombosis, or respiratory complications were encountered postoperatively. In-hospital preoperative rehabilitation under the supervision of a physiotherapist significantly improved physical function and maintained physical activity in patients with pancreatic cancer. Such improvements may contribute toward preventing serious postoperative complications, resulting in better outcomes.

H-NS Family Proteins Drastically Change Their Targets in Response to the Horizontal Transfer of the Catabolic Plasmid pCAR1.

H-NS family proteins regulate the expression of many genes by preferably binding to AT-rich genomic regions and altering DNA topology. They are found in both bacterial chromosomes and plasmids, and plasmid-encoded H-NS family proteins have sometimes been suggested to act as a molecular backup of the chromosomally encoded ones. Pmr is an H-NS family protein encoded on the catabolic plasmid pCAR1, which belongs to incompatibility P-7 group. We have investigated the function of Pmr in Pseudomonas putida KT2440, where two H-NS family proteins (TurA and TurB) encoded on the chromosome are expressed predominantly. Previous transcriptome analyses suggested that TurA, TurB, and Pmr cooperatively regulate numerous genes, but the differentially transcribed genes in KT2440ΔturA(pCAR1), KT2440ΔturB(pCAR1), and KT2440(pCAR1Δpmr) compared with those in KT2440(pCAR1) were somewhat different. Here, we performed RNA sequencing analyses to compare the differentially transcribed genes after the deletion of turA or turB in KT2440, and turA, turB or pmr in KT2440(pCAR1). Three pCAR1-free strains (KT2440, KT2440ΔturA, KT2440ΔturB) and four pCAR1-harboring strains [KT2440(pCAR1), KT2440ΔturA(pCAR1), KT2440ΔturB(pCAR1), KT2440(pCAR1Δpmr)], grown until the log and stationary phases, were used. In KT2440, TurA was the major H-NS family protein regulating a large number and wide range of genes, and both TurA and TurB were suggested to functionally compensate each other, particularly during the stationary phase. In KT2440(pCAR1), the numbers of differentially transcribed genes after the deletion of turA or turB drastically increased compared to those in KT2440. Notably, more than half of the differentially transcribed genes in KT2440ΔturA and KT2440ΔturB did not overlap with those in KT2440ΔturA(pCAR1) and KT2440ΔturB(pCAR1). This dynamic change could be explained by the acquisition of pCAR1 itself and the expression of Pmr. After pCAR1 was transferred into the host, TurA and TurB could be detached from the chromosome of KT2440 and they could newly bind to pCAR1. Moreover, Pmr could reconstitute the chromosome-binding heteromeric oligomers which were formed by TurA and TurB. Our study revealed that horizontal transfer of a plasmid changes the transcriptional network of the chromosomally encoded H-NS family proteins.

The effect of diameter size of single-walled carbon nanotubes on their high-temperature energy storage behaviour in ionic liquid-based electric double-layer capacitors.

We investigated the effect of the diameter size of single-walled carbon nanotubes (SWCNTs), on their high-temperature energy storage behavior in an electric double layer capacitor (EDLC) using the ionic liquid triethyl(2-methoxyethyl) phosphonium bis(trifluoromethylsulfonyl)imide (P222(2O1)-TFSI). We used four SWCNT samples with diameter sizes ranging from 0.8 to 5 nm, and evaluated their electrochemical charge storage behavior through galvanostatic charge/discharge and electrochemical impedance spectroscopy (EIS). We found that for the SWCNTs with small average diameter of 1 nm, the value of the electrode capacitance measured at a current density of 5 mA g-1 increased from 15.8 at room temperature to 27.5 F g-1 at 150 °C, and the value measured at a current density of 80 mA g-1 increased from 14.0 at room temperature to 22.1 F g-1 at 150 °C. The larger diameter samples on the other hand did not show any significant change in their capacitance with temperature. We calculated the size of the interstitial tube spaces from the Raman spectra of the samples, and used density functional theory (DFT) calculations to estimate the sizes of the cation and anion of the electrolyte. The obtained results suggest that the temperature-induced changes in the electrolyte properties improved the ion accessibility into the otherwise constrained space inside the small diameter SWCNTs, while the spaces inside the larger SWCNTs already provided easily accessible storage sites hence good performance at room temperature, making the increase in temperature of little to no effect on the charge storage performance in such SWCNTs.

Free flavins accelerate release of ferrous iron from iron storage proteins by both free flavin-dependent and -independent ferric reductases in Escherichia coli.

Ferredoxin NADP+ oxidoreductase (Fpr) and oxygen-insensitive NAD(P)H nitroreductase (NfnB) are purified from Escherichia coli JM109 (E. coli JM109) as a predominant free flavin-independent ferric reductase. In the present study, we prepared natural iron storage proteins, E. coli ferritin A (FtnA) and bacterioferritin (Bfr), to show the effective ferrous iron release from these proteins by Fpr and NfnB in the presence of free flavins. Fpr and NfnB showed flavin reductase activity for flavin adenine dinucleotide (FAD), flavin mononucleotide (FMN) and riboflavin, and their ferrous iron release activities were positively associated with the catalytic efficiencies (kcat/Km) for individual flavins. The ferrous iron release activity of E. coli cell-free extracts was affected by flavin reductase activity of the extracts. The Butyl TOYOPEARL column chromatography of the extracts, on the basis of NAD(P)H-dependent flavin reductase activity, resulted in the separation of six active fractions containing Fpr, NfnB, NAD(P)H-quinone oxidoreductase (QOR), flavin reductase (Fre) or alkyl hydroperoxide reductase subunit F (AhpF) as major components. Like Fpr and NfnB, recombinant QOR, Fre, and AhpF showed flavin reductase activity and ferrous iron release activity in the presence of free flavins, indicating an association of flavin reductase activity with ferrous iron releasing activity. Taken together, both free flavin-dependent and free flavin-independent ferric reductases in E. coli require free flavins to mediate an electron transfer from NAD(P)H to ferric iron in the iron storage proteins for the effective ferrous iron release.

Electrochemical Reactions of Iodine Molecules Encapsulated in Single-Walled Carbon Nanotubes.

We prepared iodine molecules encapsulated in single-walled carbon nanotubes (I@SWCNTs) by electro-oxidation of iodide ions with empty SWCNT electrode. Li-ion battery electrode properties of I@SWCNTs were investigated. It was found that the I@SWCNT sample can catch and release Li ions reversibly. We performed Raman measurements to reveal the Li-ion storage mechanism of I@SWCNT. It is plausible that chemical reactions of I2 from/into LiI in SWCNTs occur during Li-ion charging/discharging of I@SWCNT. We also prepared the CsI@SWCNT sample to verify that alkali metal ions can be extracted from alkali metal halide in SWCNTs. The extraction of cesium ions from CsI@SWCNT was confirmed by Raman measurements. It was also found that I@SWCNT can work as a Li-ion battery electrode in solid electrolyte as well.

Purified thioredoxin reductase from O2-sensitive Bifidobacterium bifidum degrades H2O2 by interacting with alkyl hydroperoxide reductase.

Bifidobacterium is beneficial for host health and exhibits different O2 sensitivity levels among species or strains via unknown mechanisms. Bifidobacterium bifidum JCM1255T, a type species of Bifidobacterium, is an O2-sensitive bacterium that can grow under low-O2 (5%) conditions, and the growth of this species is inhibited under high-O2 conditions (10% ∼) with accumulation of H2O2. We previously reported that NADH or NAD(P)H oxidase-active fractions were detected during purification using microaerobically grown B. bifidum cells, and the active enzyme was purified from the NADH oxidase-active fraction. The purified enzyme was identified as b-type dihydroorotate dehydrogenase (DHODb) and characterized as a dominant H2O2 producer in B. bifidum. In this study, we performed further purification of the enzyme from the NAD(P)H oxidase-active fraction and characterized the purified enzyme as a part of the H2O2 degradation system in B. bifidum. This purified enzyme was identified as thioredoxin reductase (TrxR); the NAD(P)H oxidase activity of this enzyme was not expressed in anaerobically grown B. bifidum, and mRNA expression was induced by O2 exposure. Furthermore, the purified B. bifidum TrxR interacted with recombinant alkyl hydroperoxide reductase (rAhpC) and exhibited NAD(P)H peroxidase activity. These results suggest that TrxR responds to O2 and protects B. bifidum from oxidative stress by degrading H2O2 via the TrxR-AhpC system.