The functional roles of disulfide bonds in the β-subunit of (Na,K)ATPase as studied by site-directed mutagenesis

AbstractThe β-subunit of Torpedo californica (Na,K)ATPase contains seven cysteine residues; one (Cys46) is in the single transmembrane segment and the other six (Cys127, Cys150, Cys160, Cys176, Cys215 and Cys278) are in the extracellular domain and form three highly conserved disulfide bonds. Aβ-subunit mutant with replacement of Cys46 by Ser could assemble with the α-subunit, and the resulting αβ-complex was catalytically active. Mutants in which either the N-terminal side or both Cys residues of the Cys127-Cys150 bond were replaced by Ser could also tightly assemble with the α-subunit, but the resulting αβ-complex was catalytically inactive. On the other hand, disruption of either the Cys160-Cys176 or Cys215-Cys278 bond by substituting the N-terminal side only or both Cys residues with Ser led to a β-subunit that could not assemble with the α-subunit. We conclude that the structure of the β-subunit around the Cys160-Cys176 and Cys215-Cys278 loops is indispensable for assembly with the α-subunit, whereas the Cys127-Cys150 loop is not essential for assembly but is required for enzyme activity

Diffusion-limited characteristics of mechanically induced currents in polypyrrole/Au-membrane composites

A mechanically induced current (MIC) in a polypyrrole/Au-coated membrane (PPy/Au-membrane) composite with various surface morphologies was investigated, and the electrolyte conditions were determined in an electrochemical cell. A MIC was induced on porous PPy/Au-membranes with a thin layer of PPy. Conversely, relatively small MICs were observed in non-highly porous films such as freestanding films and PPy/Au-membranes with thick PPy deposits. A MIC smaller by one order of magnitude was also observed in a Au-membrane without PPy. These results indicated that the MICs was due to a charging phenomenon in both the redox and the double layer capacitances. The MIC also varied with supporting electrolyte and their concentration. The MIC was strongly reduced in solutions with diluted electrolytes and with bulky cationic electrolytes, indicating that the number and the penetration speed of mobile ions limited the magnitude of the MIC. These characteristics indicated that the MIC was essentially a diffusion limited current. A two-electrode MIC cell was also configured to investigate a power generation film in a normal saline solution, which can possibly be utilized for biomedical applications

Complete nucleotide sequence, origin of isoform and functional characterization of the mouse hepsin gene

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66259/1/j.1432-1327.1999.00431.x.pd

Measurements of neutron total and capture cross sections of 139^{139}La and evaluation of resonance parameters

Neutron total and capture cross sections of Lanthanum(La)-139 were measured at the Accurate Ne-utron-Nucleus Reaction measurement Instrument (ANNRI) of the Materials and Life Science Experimental Facility (MLF) in the Japan Proton Accelerator Research Complex (J-PARC). The total cross section was largely different from that in evaluated libraries, such as JENDL-5, in the energy range from 80 to 900~eV. Resonance parameters for four resonances including one negative resonance were obtained using a resonance analysis code, REFIT. The resonance analysis revealed discrepancies in several resonance parameters with the evaluated libraries. Furthermore, the information about the scattering radius was also extracted from the results of the total cross section. The obtained scattering radius was larger than that recorded in the evaluated libraries.Comment: 12 pages, 16 figure

Effects of Using Alternative Extreme Pressure (EP) and Anti-Wear (AW) Additives with Oxy-Nitrided Samples

Oxy-nitriding is a widely used industrial process aiming to improve the tribological properties and performance of components. Previous studies have shown the effectiveness of the treatment with friction and wear performance, but very few have focussed on optimising this behaviour. The lubrication properties of several EP and AW additives were examined to investigate their effectiveness in improving the tribological properties of the layers formed after treatment. Previous studies showed the presence of an oxide layer on the sample could improve the effectiveness of the sulphurised olefin (SO) and tricresyl phosphate (TCP) additives. The friction and wear behaviour of oxy-nitrided samples were analysed using a tribometer and surface profiler. Scanning electron microscope, energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy were employed to identify the morphologies and chemical compositions of the treated surface before and after testing. No real effect on friction was observed when using the SO or TCP additives, mostly due to lack of interaction with the less reactive iron nitride layer and their roles as anti-wear additives. However, when the zinc dialkyldithiophosphate-containing lubricant was used, a higher friction coefficient was observed. Greater improvements in anti-wear properties with the presence of additives in comparison with only using base oil were reported, with the TCP additive producing the lowest wear rates. The study effectively demonstrated that the additive package type used could impact the tribological and tribochemical properties of oxy-nitrided surfaces

Association between serum lactate level during cardiopulmonary resuscitation and survival in adult out-of-hospital cardiac arrest: a multicenter cohort study

We aimed to investigate the association between serum lactate levels during cardiopulmonary resuscitation (CPR) and survival in patients with out-of-hospital cardiac arrest (OHCA). From the database of a multicenter registry on OHCA patients, we included adult nontraumatic OHCA patients transported to the hospital with ongoing CPR. Based on the serum lactate levels during CPR, the patients were divided into four quartiles: Q1 (≤ 10.6 mEq/L), Q2 (10.6–14.1 mEq/L), Q3 (14.1–18.0 mEq/L), and Q4 (> 18.0 mEq/L). The primary outcome was 1-month survival. Among 5226 eligible patients, the Q1 group had the highest 1-month survival (5.6% [74/1311]), followed by Q2 (3.6% [47/1316]), Q3 (1.7% [22/1292]), and Q4 (1.0% [13/1307]) groups. In the multivariable logistic regression analysis, the adjusted odds ratio of Q4 compared with Q1 for 1-month survival was 0.24 (95% CI 0.13–0.46). 1-month survival decreased in a stepwise manner as the quartiles increased (p for trend < 0.001). In subgroup analysis, there was an interaction between initial rhythm and survival (p for interaction < 0.001); 1-month survival of patients with a non-shockable rhythm decreased when the lactate levels increased (p for trend < 0.001), but not in patients with a shockable rhythm (p for trend = 0.72). In conclusion, high serum lactate level during CPR was associated with poor 1-month survival in OHCA patients, especially in patients with non-shockable rhythm