Quantitative Visualization of the Interaction between Complement Component C1 and Immunoglobulin G: The Effect of CH1 Domain Deletion

Immunoglobulin G (IgG) adopts a modular multidomain structure that mediates antigen recognition and effector functions, such as complement-dependent cytotoxicity. IgG molecules are self-assembled into a hexameric ring on antigen-containing membranes, recruiting the complement component C1q. In order to provide deeper insights into the initial step of the complement pathway, we report a high-speed atomic force microscopy study for the quantitative visualization of the interaction between mouse IgG and the C1 complex composed of C1q, C1r, and C1s. The results showed that the C1q in the C1 complex is restricted regarding internal motion, and that it has a stronger binding affinity for on-membrane IgG2b assemblages than C1q alone, presumably because of the lower conformational entropy loss upon binding. Furthermore, we visualized a 1:1 stoichiometric interaction between C1/C1q and an IgG2a variant that lacks the entire C_H1 domain in the absence of an antigen. In addition to the canonical C1q-binding site on Fc, their interactions are mediated through a secondary site on the C_L domain that is cryptic in the presence of the C_H1 domain. Our findings offer clues for novel-modality therapeutic antibodies.     

Ammonia production using iron nitride and water as hydrogen source under mild temperature and pressure

Ammonia generation was studied in the reaction between water and nitrogen-containing iron at 323 K and atmospheric pressure. Similar to metallic Fe, the interstitial compound Fe₃N reduced water through Fe oxidation to produce hydrogen gas, while the N combined with atomic hydrogen to produce ammonia as a byproduct. The addition of carbon dioxide to this system accelerated the reaction with concomitant consumption of carbon dioxide. The promoted ammonia production upon addition of carbon dioxide can be attributed to the generation of atomic hydrogen from the redox reaction of carbonic acid and Fe, as well as removal of used Fe from the reaction system through the formation of a soluble carbonato complex. When carbonate was added to the reaction system, the production rates of ammonia and hydrogen increased further. The results here confirmed that ammonia can be synthesized from iron nitride under mild conditions by utilizing carbon dioxide.     

Gait-based human age estimation using age group-dependent manifold learning and regression

Multimedia Tools and Applications - Human age estimation from gait is expected to be an important technology for a variety of applications such as automatic customer counting for marketing research...     

Ionization probability of secondary ions sputtered from Si(1 1 1) and Ge(1 1 1) surfaces

We have measured the energy distributions of the secondary ions sputtered from the Si(1 1 1) and Ge(1 1 1) surfaces and investigated the ionization probabilities of sputtered Si⁺ and Ge⁺ ions for clarifying their ionization mechanisms. The observed ionization probabilities depend on the velocity of Si⁺ and Ge⁺ ions. This velocity dependence can be successfully analyzed by a theoretical expression, which was proposed originally for the metal surfaces. This implies that the ionization mechanism of Si⁺ and Ge⁺ ions is the same as ions sputtered from the metal surface, i.e., the resonant electron transfer in the high velocity regime and the thermal excitation process in the low velocity regime. The difference in the ionization probability between Si⁺ and Ge⁺ ions is well explained by the difference in the band gap energy.     

Nonlinearity in power-current Characteristics of narrow-pulse-driven AlGaInP laser diodes

In this paper, a simple yet effective model is developed to analyze the nonlinearity in power-current characteristics, also known as "kinks", observed in AlGaInP selectively-buried-ridge (SBR) laser diodes driven by narrow pulses (/spl sim/10/sup -7/s). The model takes the temperature-induced waveguide as well as the carrier distribution into account, and the simulation results show good agreement with the experiments. The main factors influencing the kink behavior of SBR lasers are investigated based on this model, and it is believed to be of great help for the optimization AlGaInP laser structure for high-power applications.     

Onchocerca suzukii n. sp. and O. skrjabini (= O. tarsicola) from a relict bovid, Capricornis crispus, in Japan

The species from the tendons and sub-cutaneous tissue of the tarsal and carpal joints is identified as O. skrjabini Rukhlyadev, 1964 (this taxon, which was poorly defined and badly restored, is used instead of O. tarsicola to avoid dispute). O. skrjabini belongs to on homogeneous group of four species parasitic in Palearctic cervids, which seems to have evolved relatively recently. The morphological characteristics of the parasite of Capricornis are not sufficient to warrant the creation of a new taxon. The species from the subcutaneous tissue of the body is named O. suzukii n. sp. It belongs to a group comprising three species, parasites of antilocaprids and cervids from the Holarctic region and tropical domestic bovines, which seem to have evolved before the skrjabini group. The Japanese species does not present the hypertelic characters of the other species of the group. The microfilaria of O. suzukii is unknown. Thus it is not possible to say if this species is the same as one found in bovines (and, perhaps, in humans) in the Oita region of Kyushu Island.     

Characterization of the ubiquinone reduction site of mitochondrial complex I using bulky synthetic ubiquinones

A wide variety of alkyl derivatives of Q2 (6-geranyl-2, 3-dimethoxy-5-methyl-1,4-benzoquinone) and DB (6-n-decyl-2, 3-dimethoxy-5-methyl-1,4-benzoquinone), in which methoxy groups of the 2- and/or 3-positions of the quinone ring were replaced by other bulky alkoxy groups from ethoxy to butoxy, were prepared by novel synthetic procedures. Electron-accepting activities of the bulky quinones were investigated with bovine heart mitochondrial complex I and its counterpart of Paracoccus denitrificans(NDH-1) to elucidate structural and functional features of the quinone reduction site of the enzymes. The bulky quinone analogues served as sufficient electron acceptors from the physiological quinone reduction site of bovine complex I. Considering the very poor activities of even the ethoxy derivatives as substrates for other respiratory enzymes such as mitochondrial complexes II and III [He, D. Y., Gu, L. Q., Yu, L., and Yu, C. A. (1994) Biochemistry 33, 880-884], this result indicated that the quinone reduction site of bovine complex I is spacious enough to accommodate bulky exogenous substrates. In contrast to bovine complex I, bulky quinone analogues served as poor electron acceptors with Paracoccus NDH-1. These observations indicated that bovine complex I recognizes the substrate structure with poor specificity. The substituent effects in the 2- and 3-positions of the quinone ring on the electron-transfer activity with bovine complex I differed significantly between Q2 and DB series despite having the same total number of carbon atoms in the side chain. The inhibitory effect involving Q2 due to its geranyl side chain was markedly diminished by structural modifications of the quinone ring moiety. These findings indicate that the side chain plays a specific role in the redox reaction and that the quinone ring and side-chain moieties contribute interdependently to binding interaction. Moreover, structural dependency of the proton-pumping activity of the quinone analogues was comparable to that of the electron-transfer activity with bovine complex I, indicating that the mechanism of redox-driven proton-pumping does not differ depending upon the substrate structure.     

Dissolution Behavior of Mg from Magnesia-Chromite Refractory into Al-killed Molten Steel

Magnesia-chromite refractory materials are widely employed in steel production, and are considered a potential MgO source for the generation of MgO·Al₂O₃ spinel inclusions in steel melts. In this study, a square magnesia-chromite refractory rod was immersed into molten steel of various compositions held in an Al₂O₃ crucibles. As the immersion time was extended, Mg and Cr gradually dissolved from the magnesia-chromite refractory, and the Mg and Cr contents of the steel melts increased. However, it was found that the inclusions in the steel melts remained as almost pure Al₂O₃ because the Mg content of the steel melts was low, approximately 1 ppm. On the surface of the magnesia-chromite refractory, an MgO·Al₂O₃ spinel layer with a variable composition was formed, and the thickness of the MgO·Al₂O₃ spinel layer increased with the immersion time and the Al content of the steel melts. At the rod interface, the formed layer consisted of MgO-saturated MgO·Al₂O₃ spinel. The MgO content decreased along the thickness direction of the layer, and at the steel melts interface, the formed layer consisted of Al₂O₃-saturated MgO·Al₂O₃ spinel. Therefore, the low content of Mg in steel melts and the unchanged inclusions were because of the equilibrium between Al₂O₃-saturated MgO·Al₂O₃ layer and Al₂O₃. In addition, the effects of the Al and Cr contents of the steel melts on the dissolution of Mg from the magnesia-chromite refractory are insignificant.     

Dielectric properties above the glass transition for a series of epoxide prepolymers

Dielectric properties above the glass transition have been investigated for a series of bisphenol-A type epoxide prepolymers (388 ≤ M?_w ≤ 2640). Dielectric measurements were performed over a frequency range of 50 Hz–1 MHz using a vertical parallel plate cell which was constructed in the laboratory. The dielectric α-relaxation for each prepolymer fits the empirical model of the Havriliak–Negami equation. The temperature dependence of the dielectric relaxation time τ is described by the Williams–Landel–Ferry (WLF) equation as well as that of the direct current conductivity σ, which can be measured using the same cell. The relationship between τ and σ, σ^· τ^m = const, is derived from experimental results. The exponent m, which depends on the molecular weight of the prepolymer, is considered to correspond to the ratio of the segmental mobility to ionic mobility. The dielectric loss ε″ can be used as an indicator of the direct current conduction in the temperatures where the ionic component in ε″ becomes much larger than the dipole one.     

Ethanol and lactic acid production using sap squeezed from old oil palm trunks felled for replanting

Old oil palm trunks that had been felled for replanting were found to contain large quantities of high glucose content sap. Notably, the sap in the inner part of the trunk accounted for more than 80% of the whole trunk weight. The glucose concentration of the sap from the inner part was 85.2 g/L and decreased towards the outer part. Other sugars found in relatively low concentrations were sucrose, fructose, galactose, xylose, and rhamnose. In addition, oil palm sap was found to be rich in various kinds of amino acids, organic acids, minerals and vitamins. Based on these findings, we fermented the sap to produce ethanol using the sake brewing yeast strain, Saccharomyces cerevisiae Kyokai no.7. Ethanol was produced from the sap without the addition of nutrients, at a comparable rate and yield to the reference fermentation on YPD medium with glucose as a carbon source. Likewise, we produced lactic acid, a promising material for bio-plastics, poly-lactate, from the sap using the homolactic acid bacterium Lactobacillus lactis ATCC19435. We confirmed that sugars contained in the sap were readily converted to lactic acid with almost the same efficiency as the reference fermentation on MSR medium with glucose as a substrate. These results indicate that oil palm trunks felled for replanting are a significant resource for the production of fuel ethanol and lactic acid in palm oil-producing countries such as Malaysia and Indonesia.