Molecular distance measurements reveal an (alpha beta)2 dimeric structure of Na+/K+-ATPase. High affinity ATP binding site and K+-activated phosphatase reside on different alpha-subunits

ATP hydrolysis by Na+/K+-ATPase proceeds via the interaction of simultaneously existing and cooperating high (E1ATP) and low (E2ATP) substrate binding sites. It is unclear whether both ATP sites reside on the same or on different catalytic alpha-subunits. To answer this question, we looked for a fluorescent label for the E2ATP site that would be suitable for distance measurements by F?rster energy transfer after affinity labeling of the E1ATP site by fluorescein 5'-isothiocyanate (FITC). Erythrosin 5'-isothiocyanate (ErITC) inactivated, in an E1ATP site-blocked enzyme (by FITC), the residual activity of the E2ATP site, namely K+-activated p-nitrophenylphosphatase in a concentration-dependent way that was ATP-protectable. The molar ratios of FITC/alpha-subunit of 0.6 and of ErITC/alpha-subunit of 0.48 indicate 2 ATP sites per (alpha beta)2 diprotomer. Measurements of F?rster energy transfer between the FITC-labeled E1ATP and the ErITC-labeled or Co(NH3)4ATP-inactivated E2ATP sites gave a distance of 6.45 +/- 0.64 nm. This distance excludes 2 ATP sites per alpha-subunit since the diameter of alpha is 4-5 nm. F?rster energy transfer between cardiac glycoside binding sites labeled with anthroylouabain and fluoresceinylethylenediamino ouabain gave a distance of 4.9 +/- 0.5 nm. Hence all data are consistent with the hypothesis that Na+/K+-ATPase in cellular membranes is an (alpha beta)2 diprotomer and works as a functional dimer (Thoenges, D., and Schoner, W. (1997) J. Biol. Chem. 272, 16315-16321).     

An anti-inflammatory role for glucocorticoids in the ovaries?

The binding of Ca2+ ions to bovine and human thyroglobulin (Tg) was demonstrated qualitatively by 45Ca overlay on polyvinylidene difluoride (PVDF) membranes. A quantitative analysis of the interaction of metal ions with bovine Tg was conducted by fluorimetric titration of the protein with Tb3+ ions. These have been used with several proteins as isomorphous replacement probes for Ca2+ ions, as protein-bound Tb3+ ions fluoresce, upon irradiation in the UV region, because of energy transfer from tyrosyl and/or tryptophanyl residues. The fluorescence emission spectrum of Tg excited at 280 nm showed, upon addition of Tb3+ ions, a peak at 546 nm and a marked decrease at 335 nm, indicating an efficient F?rster energy transfer between bound Tb3+ ions and closely located Tg intrinsic chromophores. Titration of Tg with Tb3+ ions, carried out by monitoring the emitted fluorescence at 546 nm, indicated the presence of 13.15 metal binding sites per Tg molecule.     

Energy transfer in photosynthesis

A theoretical model is presented to account for the physical mechanism of energy transfer from antenna molecules to the reaction centers in photosynthesis. The energy transfer is described by a generalized transport equation or "master equation". The solution of this equation for the proposed model gives a relationship between the antennae interaction energy and the transfer rate. The results are shown to be in agreement with inter-antenna transfer rates calculated from experimental fluorescence lifetimes. Previous theories were based either on the F?rster mechanism, which is valid for very small interaction energies, or an exciton model valid for very large interactions, but experimental results seemed to indicate that the actual situation was intermediate between these two. The F?rster theory and the exciton model are limiting cases of the master equation.     

Adjuvant radiation therapy for adenocarcinoma of the rectum

The potential for electron transfer quenching of rose bengal triplet (3RB2-) to compete with energy transfer quenching by oxygen was evaluated. Rate constants for oxidative and reductive quenching were measured in buffered aqueous solution, acetonitrile and in small unilamellar liposomes using laser flash photolysis. Biologically relevant quenchers were used that varied widely in structure, reduction potential and charge. Radical ion yields (phi i) were measured by monitoring the absorption of the rose bengal semireduced (RB.3-) and semioxidized (RB.-) radicals. The results in solution were analyzed as a function of the free energy for electron transfer (delta G) calculated using the Weller equation including electrostatic terms. Exothermic oxidative quenching was about 10-fold faster than exothermic reductive quenching in aqueous solution. The quenching rate constants decreased as delta G approached zero in both aqueous and acetonitrile solution. Exceptions to these generalizations were observed that could be rationalized by specific steric or electrostatic effects or by a change in mechanism. The results suggest that electron transfer reactions with some potential quenchers in cells could compete with formation of singlet oxygen [O2(1 delta g)]. Values of phi i were generally greater for reductive quenching and, for oxidative quenching, greater in acetonitrile than in buffer. Electron transfer quenching of 3RB2- in liposomes, below the phase transition temperature was slower than in solution for both lipid-soluble and water-soluble quenchers indicating that these reactions may not compete with formation of O2(1 delta g) during cell photosensitization.     

Interaction of hemoglobin with red blood cell membranes as shown by a fluorescent chromophore

Hemoglobin quenching of the fluorescence intensity of 12-(9-anthroyl)stearic acid (AS) embedded in the red blood cell membrane occurs through an energy transfer mechanism and can be used to measure the binding of hemoglobin to the membrane. The binding of hemoglobin to red cell membranes was found to be reversible and electrostatic in nature. Using a theory of energy transfer based on F?rster formulation, the quantitative data for the binding were derived. The number of binding sites was found to be 1.4 +/- 0.2 X 10(6) molecules per cell and the binding constant was 0.85 X 10(8) M-1.     

The influence of cognitive bias on the perceived odor, irritation and health symptoms from chemical exposure

The distance between the beta-subunits of Na+/K+-ATPase isolated from pig dark red kidney medulla was determined by F?rster energy transfer. First, oligosaccharides of the beta-subunit were shown to be labelled with three fluorophores: Lucifer yellow (LY), Lissamine rhodamine B sulfonyl hydrazine (LRSH) and Cascade blue (CB). Further, LY and LRSH were used as the donor and the acceptor, respectively, for F?rster energy transfer studies to determine the localization of the beta-subunit in the native enzyme which is known to be formed as a tetramer (alphabeta)2. It was found that the beta-subunits in the functional enzyme complex in the membrane are not localized next to each other but are spatially separated. The distance between fluorophores covalently attached to the beta-subunits was found to be 5.1 nm. This conclusion was confirmed by measurements with another donor-acceptor pair CB-LY. The results also support the idea of a direct interaction of the beta-subunit with the extracellular part of the alpha-subunit. These interactions were modified in the presence of millimolar concentrations of magnesium ions. This indicates a crucial role of magnesium in extracellular interactions between the alpha and beta subunits.     

Eu3+激活的Li2Gd4（MoO4）7钼酸盐红色荧光体及其发光性质

由高温固相反应首次合成Li2(Gd1-xEux)4(MoO4)7(0相似文献   

Energy-dependent 63Ni-uptake by Alcaligenes eutrophus strains H1 and H16 (author's transl)

Kinetic studies of the uptake of 63Ni were undertaken with two strains of Alcaligenes eutrophus, known to require nickel ions for chemolithotrophic growth. Using carbon dioxide as sole carbon source, growth is stimulated by low concentrations of nickel with optimum concentration for growth stimulation at about 0.3 micron nickel. Higher nickel concentrations were inhibitory. Heterotrophic growth on fructose was not stimulated by nickel ions.--Upon transfer into phosphate buffer freed of heavy metal ions, autotrophically grown cells exhibited rapid uptake of 63Ni which was dependent upon the presence of hydrogen, oxygen and carbon dioxide. Within 60 min nickel was accumulated from the medium, reaching 280-fold concentration in the cells. The observed uptake exhibited a temperature optimum at about 29 degrees C and was markedly inhibited by metabolic inhibitors such as arsenite, iodoacetate, methylene-blue, sodium azide and sodium cyanide. Other heavy metal ions (Zn, Co, Mn and Cu) only slightly inhibited 63Ni-uptake. The efflux of 63Ni from the cells was stimulated by 58NiCl2 and by toluene. These data indicate that nickel ions are accumulated by an energy dependent mechanism in chemolithotrophically grown cells of these strains.     

Interface formation energy,bonding,energy band alignment in α-NaYF4 related core shell models:For future multi-layer core shell luminescence materials

To break through the bottle-neck of quantum yield in upconversion(UC) core-shell system, we elucidated that the energy transfer efficiency in core-shell system had an evident contribution from the charge transfer of interface with related to two factors:(1) band offsets and(2) binding energy area density. These two variables were determined by material intrinsic properties and core-shell thickness ratio. We further unraveled the mechanism of non-radiative energy transfer by charge transfer induced dipole at the interface, based on a quasi-classical derivation from F?rster type resonant energy transfer(FRET) model. With stable bonding across the interface, the contributions on energy transfer in both radiative and non-radiative energy transfer should also be accounted together in Auzel's energy transfer(ETU) model in core-shell system. Based on the discussion about interface bonding, band offsets, and formation energies, we figured out the significance of interface bonding induced gap states(IBIGS) that played a significant role for influencing the charge transfer and radiative type energy transfer. The interface band offsets were a key factor in dominating the non-radiative energy transfer, which was also correlated to core-shell thickness ratio. We found that the energy area density with related to core/shell thickness ratio followed the trend of Boltzman sigmoidal growth function. By the physical trend, this work contributed a reference how the multi-layered core-shell structure was formed starting from the very beginning within minimum size. A route was paved towards a systematic study of the interface to unveil the energy transfer mechanism in core-shell systems.     

Tunable emission,energy transfer and thermal stability of Ce3+, Tb3+ co-doped Na2BaCa(PO4)2 phosphors

A series of single Ce³⁺ doped and Ce³⁺ and Tb³⁺ co-doped Na₂BaCa(PO₄)₂ (NBCP) phosphors was synthesized by conventional solid-stated reaction method. The crystal structure, luminescence properties, thermal stability and energy transfer were carefully investigated. Ce³⁺ is inferred to substitute the Ba²⁺ site in NBCP lattice. The color-tunable emission from blue to green is observed by adjusting Tb³⁺ concentration among NBCP:0.03Ce³⁺,yTb³⁺ phosphors. The energy transfer behavior from Ce³⁺ to Tb³⁺ ions is both illustrated by co-doped PL spectra and decay curves. The energy transfer efficiency is as high as 91.5%. The mechanism of energy transfer is resonance type of dipole-dipole transition. In this work, the optimal phosphor exhibits the excellent thermal stability which keeps at 94.9% of that initial value at room temperature when temperature reaches to 150 °C. The Ce³⁺ and Tb³⁺ co-doped NBCP phosphor is a promising candidate for the application in the general lighting and display fields.     

Structural heat-resistant β-NiAl + γ′-Ni<Subscript>3</Subscript>Al alloys of the Ni–Al–Co system: I. Solidification and structure

When analyzing the ternary Ni–Al–M phase diagrams, where M is a group VI–VIII transition metal, we chose the Ni–Al–Co system, where the γ′ and γ phases are in equilibrium with the β phase, as a base for designing alloys with the following physicochemical properties: a moderate density (≤7.2 g/cm³) and satisfactory heat resistance at temperatures up to 1300°C. The structure formation in heterophase β + γ′ alloys during directional solidification is studied. It is found that, in contrast to cobalt-free β + γ′ alloys (where the γ′-Ni₃Al aluminide forms according to the peritectic reaction L + β ? γ′), the alloys with 8–10 at % Co studied in this work during directional solidification at 1370°C contain the degenerate eutectic L ? β + γ. The transition from the β + γ field to the β + γ′ + γ field occurs in the temperature range 1323–1334°C, and the γ′ phase then forms according to the reaction β + γ ? γ′.     

Mechanisms of nitroso compound-induced inhibition of superoxide generation in neutrophils: fluorescence quenching of perylene by nitroso-compounds in the membrane fractions of neutrophils

To investigate the mechanism of nitroso compound-induced inhibition of the respiratory burst in neutrophils, we studied fluorescence quenching of perylene by nitroso-compounds in the membrane fractions of neutrophils at 17, 27, and 37 degrees C and the reagent-induced inhibition of superoxide generation at 28 and 37 degrees C. With increasing temperature, the quenching of perylene fluorescence and inhibition of superoxide generation by nitrosobenzene (NB) were both diminished, while those by 2-nitrosotoluene (NT) were both enhanced. The temperature dependence of the inhibition constants and the quenching constants indicates that the binding of NB is exothermic (deltaH= -27 kJ/mol for inhibition and deltaH= -29 kJ/mol for quenching) and essentially enthalpy-driven. On the other hand, that of NT is endothermic (deltaH= +16 kJ/mol for inhibition and quenching) and essentially entropy-driven. Quenching studies of perylene fluorescence in synthetic vesicles made of endogenous polar lipids of neutrophils showed that the enthalpy changes of NB- and NT-binding with perylene in lipids were similar to each other. Moreover, their values were in good agreement with that of NT, but not of NB, in the membrane fractions, an assembly of proteins and lipids, of neutrophils. These results suggest that NB inhibits the activity by binding to proteins in the membrane, whereas inhibition by NT occurs through hydrophobic interaction with lipids and/or proteins.     

Possible nystatin-protein interaction in yeast plasma membrane vesicles in the presence of ergosterol. A F?rster energy transfer study

The F?rster energy transfer from tryptophan residues of membrane proteins to nystatin was measured in reconstituted yeast plasma membrane vesicles free of, or doped with, ergosterol. We wanted to elucidate whether the functional change of membrane transport proteins from H+ symporters to facilitators, observed in ergosterol-containing plasma membrane vesicles on addition of nystatin [Opekarová and Tanner (1994) FEBS Lett. 350, 46-50], is reflected in altered protein-nystatin relations within the membrane. Both frequency-domain and time-domain time-resolved fluorescence spectroscopy showed that in the presence of ergosterol nystatin is located much closer to membrane proteins than in its absence.     

Structure and luminescence properties of Sm~(3+) doped Y_2MoO_6 phosphor under near ultraviolet light excitation

A series of Sm~(3+) doped Y_2MoO_6 were prepared through high temperature solid state reaction technique. Their phase structures, morphologies and luminescence properties were investigated by X-ray diffraction(XRD), scanning electron microscopy(SEM) and photoluminescence spectrometry. The most intense absorption of Y_2MoO_6 host occurred at 367 nm. Energy transfer from host lattice to Sm~(3+) ions could be observed, and the schematic diagram of energy transfer was constructed. The critical energy transfer distance and energy transfer mechanism between Sm~(3+) ions were discussed in detail. Considering the high color purity and appropriate emission intensity, Sm~(3+) doped Y_2 MoO_6 could be a promising phosphor under near ultraviolet light excitation.     

Ni-Ga-Fe-Co铁磁形状记忆合金的磁性转变和马氏体相变

Ferromagnetic shape memory alloys (FSMAs) such as NiMnGa, FePd and FePt are attractive as a new magnetic actuator material. They show a large magnetic-field-induced strain of 3% - 9% due to the variant rearrangement. Recently, the present authors have reported that in the Ni-Ga-Fe alloy the martensitic transformationfrom the B2 and/or the L21 structures into a seven-layer or five-layer modulated structure occurs upon cooling. In this alloy system, however, it is impossible to obtain a martensite phase at RT with a Curie temperature (To) higher than 100℃. In this work, the effects of substitution of Co for Ni on the martensitic and magnetic transformations, crystal structures and phase equilibria in Ni-Ca-Fe alloys were studied. Ni-Ga-Fe-Co alloys were prepared by induction melting under an argon atmosphere. Small pieces of specimens were taken from the ingot and homogenized at 1433 K for 24 h followed by quenching in water. The obtained specimens were aged at 773 K for 24 h and then quenched. The compositions of each phase were determined by energy dispersion X-ray spectroscopy (El)X). The martensitic transformation temperatures and Tc were measured by differential scanning calorimetry (DSC) and vibrating sample magnetometer (VSM) measurement. The crystal structure of martensite phase was observed by X-ray diffractmeter (XRD) and transmission electron microscope (TEM). The Curie temperature Tc was increased with increasing Co content while the martensitic transformation temperature slightly decreased. In the Ni(54-x) Ga27 Fe19 Cox, Tc increases from 303 K to 408 K with increasing CO content from x=0 to x=6. The crystal structure of the martensite phase and the phase equiribria in the Ni-Fe-Ga-Co alloys will be also presented.     

Metal complexation reactions of quinolone antibiotics in a quadrupole ion trap

We have undertaken a systematic study of the nature of quinolone metal complexes formed by electrospray ionization and laser desorption/ion-molecule reactions to evaluate the analytical utility of metal complexation as an alternative to conventional ionization via protonation. Metal ionization with laser-desorbed copper and nickel ions results in addition products of the form (L + Cu+) and (L + Ni+), respectively, where L is the quinolone, whereas addition-elimination products of the form (L + Co(+)-28) are observed when cobalt is used. The elimination of CO in order to form this unusual latter product seems to be favored by the formation of a cyclized structure that is stabilized by intramolecular hydrogen bonding. The CAD patterns of the Ni+ complexes prove to be the most structurally informative, more so than the fragmentation patterns of the protonated quinolones. Quinolone-metal complexes of the type [MII(L-H+)-(dipy)]+, where M is either Cu, Co, or Ni and dipy is 2,2'-dipyridine, are generated by electrospray ionization of a methanolic solution containing a quinolone antibiotic, a transition metal ion salt, and an auxiliary diimine ligand. Upon collisional activation, the ESI-generated complexes dissociate predominantly by loss of CO2, which is also the most common fragmentation pathway for the metal complexes formed through laser desorption/ion-molecule reactions. However, there are fewer structurally diagnostic fragment ions in the CAD spectra of the ESI complexes relative to those of the LD complexes.     

Thermal expansion in the Ni−Cr−Al and Co−Cr−Al systems to 1200°C determined by high-temperature X-ray diffraction

The effect of temperature on the lattice parameters of phases in twelve nickel-chromium-aluminum (Ni?Cr?Al) alloys and nine cobalt-chromium-aluminum (Co?Cr?Al) alloys was determined using high temperature diffraction (HTXRD). The temperature range was from 25 to 1200°C. The data for each phase of each alloy were computer fit to an empirical thermal expansion equation developed in this study: \(LP_T = LP_{25^\circ C} (1 + R)^{(1 + T/273)^{1.5} } \) and a value forR was derived for each. Excellent fits were obtained for nearly all cases. A comparison ofR values revealed that for a given phase (ψ/ψ′, β and α in Ni?Cr?Al and αCo and β in Co?Cr?Al),R was independent of alloy composition. In the Ni?Cr?Al systemR for γ/γ′ was 19.2×10^?4,R for β was 19.9×10^?4 andR for αCr was 13.4×10^?4. In the Co?Cr?Al system theR value for αCo was 20.9×10^?4 and theR for β was 17.8×10^?4. Of all of the phases only the αCr in the Ni?Cr?Al system had anR sufficiently low to reduce to an unimportant level the stress generated from thermal expansion mismatch between Al₂O₃ and substrate or coating and substrate with either Ni?Al or Co?Al coatings on a γ/γ′-δ substrate.     

热处理工艺对5 mm 9Ni钢板性能的影响

研究了淬火+亚温淬火+回火(QLT)、淬火+回火(QT)、正火+正火+回火(NNT)3种工艺对5 mm9Ni钢板低温韧性的影响.结果 表明,采用NNT工艺,钢板低温韧性良好,逆变奥氏体含量8.0％;通过工艺试制,5mm 9Ni钢板,采用3.3mm厚度规格试样,-196℃冲击吸收能量≥40 J;采用2.5mm厚度规格试样...     

On the decomposition of β phase in some rapidly quenched titanium-eutectoid alloys

The decomposition of the β phase in rapidly quenched Ti-2.8 at. pct Co, Ti-5.4 at. pct Ni, Ti-4.5 at. pct, and 5.5 at. pct Cu alloys has been investigated by electron microscopy. During rapid quenching, two compctitive phase transformations, namely martensitic and eutectoid transformation, have occurred, and the region of eutectoid transformation is extended due to the high cooling rates involved. The β phase decomposed into nonlamellar eutectoid product (bainite) having a globular morphology in Ti-2.8 pct Co and Ti-4.5 pct Cu (hypoeutectoid) alloys. In the near-eutectoid Ti-5.5 pct Cu alloy, the decomposition occurred by a lamellar (pearlite) type, whereas in Ti-5.4 pct Ni (hypereutectoid), both morphologies were observed. The interfaces between the proeutectoid α and the intermetallic compound in the nonlamellar type as well as between the proeutectoid α and the pearlite were often found to be partially coherent. These findings are in agreement with the Lee and Aaronson model proposed recently for the evolution of bainite and pearlite structures during the solid-state transformations of some titanium-eutectoid alloys. The evolution of the Ti₂Cu phase during rapid quenching involved the formation of a metastable phase closely related to an “ω-type” phase before the equilibrium phase formed. Further, the lamellar intermetallic compound Ti₂Cu was found to evolve by a sympathetic nucleation process. Evidence is established for the sympathetic nucleation of the proeutectoid a crystals formed during rapid quenching.     

Cooperative energy transfer in Eu3+,Yb3+ codoped Y2O3 phosphor

Under 980 nm laser excitation,red emission(5D0-7FJ(J=0,1,2)) of Eu3+ was observed in cubic Y2O3 codoped with Eu3+ and Yb3+.The dependence of the upconverted emission on doping concentration and laser power was studied.Yb3+ emission around 1000 nm(2F5/2-2F7/2) was reported upon excitation of Eu3+ ions.The decay curves of 5DJ(J=0,2) emission of Eu3+ under excitation of 266 nm pulse laser were examined to investigate the Eu3+→Yb3+ energy transfer process.Cooperative energy transfer process was discussed as the possible mechanism for the visible up-conversion luminescence of Eu3+ and near-infrared down-conversion emission of Yb3+.