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Immunophenotypic analysis of peripheral blood leukocytes from patients with multiple sclerosis (MS) showed a profile reflecting a state of activation and differentiation of monocytes. A subset of CD16+ monocytes with high HLA-DR expression was more prominent in patients with MS than in healthy subjects. The presence of the inducible form of nitric oxide synthase (iNOS) in these differentiated and activated monocytes freshly obtained from patients with MS was demonstrated by immunocytochemistry and flow cytometry analysis with two different antibodies. Incubation of lymphomononuclear cells from healthy volunteers in the presence of an immunomodulating peptide (NVLGAPKKLNESQAV) led to stimulation and maturation of monocytes manifested by changes in phenotype and an increase in both iNOS mRNA and protein, as well as HLA-DR expression. In this case also iNOS was expressed mainly on subsets of CD16+ monocytes with high HLA-DR expression. NO produced by human monocytes seems to have a function in the upregulation of membrane HLA-DR. These results are suggestive of a role for monocytic iNOS in the autoimmune response underlying the pathogenesis of multiple sclerosis.

The structural and thermal properties of small carbon clusters (CN, N = 13, 20, and 32) are investigated by constant energy Molecular Dynamics simulations over a wide range of temperatures, i.e., from T = 0K to above the melting point of graphitic carbon. The Tersoff interatomic potential [6] is used to mimic the covalent bond between the carbon atoms in the cluster. We find that small carbon clusters start to fragment or to evaporate atoms or C2 or C3 units before fully developing a liquidlike phase. As a consequence, some relevant isomers (such as rings, bowls, hollow cages) are thermally isolated from each other i.e., there are no thermally activated isomerization transitions between them. Possible implications of our results on the growth mechanism of fullerenes are discussed.

Density functional theory has been used to study the electronic structure and binding of ${\mathrm{Na}}_{\mathit{N}}$ clusters (N\ensuremath{\le}30) encapsulated inside the large fullerene ${\mathrm{C}}_{240}$. One or more electrons are always transferred from the endohedral ${\mathrm{Na}}_{\mathit{N}}$ to the cage. The charge density distribution reveals that for small N the binding between ${\mathrm{Na}}_{\mathit{N}}$ and the fullerene is purely ionic, and that for N\ensuremath{\gtrsim}9 a covalent contribution to the bonding develops, enhanced by the expansion of the endohedral ${\mathrm{Na}}_{\mathit{N}}$. The evolution of the type of bonding with increasing N is analyzed by comparing the size variations of the binding energy and the ionization potential of the ${\mathrm{Na}}_{\mathit{N}}$ clusters. \textcopyright{} 1996 The American Physical Society.

Synthetic peptides with sequences present in extracellular matrix proteins are capable of causing the expression of the inducible form of nitric oxide synthase (iNOS), detected by immunocytochemistry, and the release of NO by human lymphomononuclear cells incubated in their presence. Active peptides are 15-mers containing a characteristic 2-6-11 motif in which the amino acid residue at position 2 is Leu, Ile, Val, Gly, Ala or Lys; the residue at position 6 is always Pro; and residue 11 is Glu or Asp. The induction of iNOS in human monocytes and macrophages could be involved in the cytotoxicity against tumor cell lines also elicited by these peptides.

Objetivo: Describir la dependencia a la nicotina y la preparacion para dejar de fumar en la poblacion fumadora. Metodos: Estudio transversal de una muestra representativa de la poblacion espanola ≥18 anos. La informacion se obtuvo mediante entrevistas telefonicas realizadas en junio y julio de 2006. Se estudio la dependencia a la nicotina mediante el test de Fagerstrom (FTND) y la preparacion para dejar de fumar de acuerdo a los estadios del cambio del modelo transteorico en una muestra de fumadores de cigarrillos. Resultados: El 22,5% de los participantes (IC 95%: 20,9-24,2%) fumaba cigarrillos. Su consumo medio fue de 14,4 cigarrillos diarios (desviacion estandar 9,15) y su puntuacion media en el FTND fue de 2,8, sin diferencias segun los estadios del cambio. El 64,3% (IC 95%: 60,3-68,2%) de los fumadores estaba en el estadio de precontemplacion, el 25,4% (IC 95%: 21,8-28,9%) en el de contemplacion y el 10,4% (IC 95%: 7,9-12,9%) en el estadio de preparacion, sin diferencias por sexo. Los fumadores mas dependientes a la nicotina (FTND≥6) tenian mayoritariamente estudios primarios, comenzaron a fumar a edad mas temprana y fumaban mas cigarrillos al dia. Conclusiones: Los fumadores presentan mayoritariamente un bajo nivel de dependencia a la nicotina y se encuentran en fase de precontemplacion. Los programas de deshabituacion deberian ir dirigidos a reducir el nivel de dependencia, ayudar a los fumadores a avanzar a traves de los estadios del cambio y, consecuentemente, disminuir la prevalencia de fumadores en la poblacion.

The structures of [{RhLL'(μ-X)}(2)] [LL' = cod, (CO)(2), (CO)(PPh(3)) or {P(OPh)(3)}(2); X = mt or taz], prepared from [{RhLL'(μ-Cl)}(2)] and HX in the presence of NEt(3), depend on the auxiliary ligands LL'. The head-to-tail arrangement of the two N,S-bridges is accompanied by a rhodium-eclipsed conformation for the majority but the most hindered complex, [{Rh[P(OPh)(3)](2)(μ-taz)}(2)], uniquely adopts a sulfur-eclipsed structure. The least hindered complex, [{Rh(CO)(2)(μ-mt)}(2)], shows intermolecular stacking of mt rings in the solid state. The complexes [{RhLL'(μ-X)}(2)] are chemically oxidised to trinuclear cations, [(RhLL')(3)(μ-X)(2)](+), most probably via reaction of one molecule of the dimer, in the sulfur-eclipsed form, with the fragment [RhLL'](+) formed by oxidative cleavage of a second.

The inflammation hypothesis of ageing suggests that molecular inflammation could be an underpinning of ageing and age-related diseases such as rheumatoid arthritis (RA). Besides, mitochondrial alterations may contribute to the progression of RA. In this study we investigated the relationship between mitochondrial dysfunction and the in vitro expression of cyclooxigenase-2 (COX-2), prostaglandin E2 (PGE2) and interleukin-8 (IL8) in normal human synoviocytes. Commonly used inhibitors to induce mitochondrial dysfunction were employed (antimycin A (AA) and oligomycin (OLI), inhibitors of complexes III and …

The reaction of potassium hydrotris(methimazolyl)borate {KTm = HB(mt)(3)} with [{Rh(cod)(mu-Cl)}(2)] gave [Rh(cod)Tm] while the complexes [Rh(CO)(PR(3))Tm] (R = Ph or NMe(2)) and [Rh{P(OPh)(3)}(2)Tm] were isolated from light-sensitive [Rh(CO)(2)Tm], prepared in situ from KTm and [{Rh(CO)(2)(mu-Cl)}(2)], and PR(3) or P(OPh)(3) under CO. The complexes [Rh(cod)Tm] and [Rh(CO)(PR(3))Tm] (R = Ph or NMe(2)) adopt kappa(3)-S(2)H structures in the solid state but in all cases rapid dynamic exchange processes render the three mt rings equivalent in solution. Oxidation of [Rh(CO)(PPh(3))Tm] with [Fe(eta-C(5)H(5))(2)][PF(6)] in the presence of NHPr(i)(2) gave a mixture containing two monocationic rhodaboratranes. One is assigned as [Rh(CO)(PPh(3)){B(mt)(3)}][PF(6)] on the basis of IR and NMR spectroscopy, with boron trans to the phosphine ligand. The second, structurally characterised as [Rh(PPh(3)){B(mt)(3)}][PF(6)], has boron trans to an empty coordination site, vacated by CO. Similar oxidation of [Rh(cod)Tm] gave small quantities of the boron-fluorinated bis(scorpionate) [Rh{FB(mt)(3)}(2)][PF(6)].

Novel medical and biological applications are driving increased interest in the fabrication of micropipette or micro-dispensers. Reduced volume samples and drug dosages are prime motivators in this effort. We have combined microfabrication technology with ion beam milling techniques to successfully produce cantilever-type polysilicon micro-dispensers with 3D enclosed microchannels. The microfabrication technology described here allows for the designing of nozzles with multiple shapes. The contribution of ion beam milling has had a large impact on the fabrication process and on further customizing shapes of nozzles and inlet ports. Functionalization tests were conducted to prove the viability of ion beam-fabricated micro-dispensers. Self-assembled monolayers were successfully formed when a gold surface was patterned with a thiol solution dispensed by the fabricated micro-dispensers.

The ground-state atomic and electronic distributions in ${\mathrm{Na}}_{\mathit{m}}$${\mathrm{Cs}}_{\mathit{n}}$ clusters with composition m=n and m=2n have been calculated by minimizing the total cluster energy using the density-functional formalism. The approximation is made by replacing the total external potential of the ions by its spherical average around the cluster center during the iterative process of solving the Kohn-Sham equations for each geometry tested. In the size range studied here (up to 90 atoms per cluster), the cluster is composed of well-separated homoatomic Na and Cs shells, the external one always being a Cs shell. We have also found that the cohesive energy goes rapidly to the bulk limit. An analysis of the geometries shows strong cluster reconstruction with increasing size. By comparing the geometry of pure ${\mathrm{Na}}_{\mathit{n}}$ with that of the ${\mathrm{Na}}_{\mathit{n}}$ core in ${\mathrm{Na}}_{\mathit{n}}$${\mathrm{Cs}}_{\mathit{n}}$ for clusters formed by only an inner Na layer and an outer Cs layer, we have observed that the ${\mathrm{Na}}_{\mathit{n}}$ core adopts a geometry different in most cases from that of the free ${\mathrm{Na}}_{\mathit{n}}$ cluster, and such that the number of faces of the polyhedron formed by the ${\mathrm{Na}}_{\mathit{n}}$ core is as close as possible to the number of external Cs atoms, in order to accomodate these Cs atoms on top of the faces of the polyhedron.

1. 1. Pyridoxal-5′-phosphate (PLP), a marker of primary amines, bound covalently to S-1 in an approximate ratio of 1:1. PLP was localized within the tryptic 25,000 mol. wt fragment. 2. 2. Fluorescein isothiocyanate (FITC), which is known to bind covalently to primary amino groups located at nucleotide binding sites, readily bound to S-1 in a 2:1 ratio. FITC was localized within the 20,000 and 50,000 mol. wt tryptic peptides, in a ratio of 1:1 in each one. 3. 3. These results are consistent with the existence of nucleotide binding sites on myosin different from those of the catalytic sites.

A theoretical investigation on the structure, stability, and thermal behaviors of the smallest polymeric units, the dimers, formed from substitutionally Si-doped fullerenes is presented. A density functional based nonorthogonal tight-binding model has been employed for describing the interatomic interactions. The study focuses on those polymeric structures which involve Si-Si or Si-C interfullerene bonds. The binding energy of the dimers increases with their Si content from about 0.25 eV in C(60)-C(60) to about 4.5 eV in C(58)Si(2)-C(58)Si(2). Moreover, the C(59)SiC(59) dimer, linked through the sharing of the Si atom between the two fullerenes, has been also considered. Upon heating, the dimers eventually fragment into their constituent fullerene units. The fragmentation temperature correlates with the strength of the interfullerene bonds. C(58)Si(2)-C(58)Si(2) exhibits a higher thermal stability (fragmentation temperature of approximately 500 K) than the pure carbon C(60)-C(60) dimer (with a fragmentation temperature of approximately 325 K). Given the higher structural and thermal stabilities of the Si-doped fullerene dimers, the authors propose the use of substitutionally Si-doped fullerenes as the basic units for constructing new fullerene-based polymers.

Articular cartilage is optimised for bearing mechanical loads. Chondrocytes are the only cells present in mature cartilage and are responsible for the synthesis and integrity of the extracellular matrix. Appropriate joint loads stimulate chondrocytes to maintain healthy cartilage with a concrete protein composition according to loading demands. In contrast, inappropriate loads alter the composition of cartilage, leading to osteoarthritis (OA). Matrix metalloproteinases (MMPs) are involved in degradation of cartilage matrix components and have been implicated in OA, but their role in loading response is unclear. With this study, we aimed to elucidate the role of MMP-1 and MMP-3 in cartilage composition in response to mechanical load and to analyse the differences in aggrecan and type II collagen content in articular cartilage from maximum- and minimum-weight-bearing regions of human healthy and OA hips. In parallel, we analyse the apoptosis of chondrocytes in maximal and minimal load areas. Because human femoral heads are subjected to different loads at defined sites, both areas were obtained from the same hip and subsequently evaluated for differences in aggrecan, type II collagen, MMP-1, and MMP-3 content (enzyme-linked immunosorbent assay) and gene expression (real-time polymerase chain reaction) and for chondrocyte apoptosis (flow cytometry, bcl-2 Western blot, and mitochondrial membrane potential analysis). The results showed that the load reduced the MMP-1 and MMP-3 synthesis (p non-loaded areas). Moreover, compared with normal cartilage, OA cartilage showed a 10- to 20-fold lower ratio of aggrecan to type II collagen, suggesting that the balance between the major structural proteins is crucial to the integrity and function of the tissue. Alternatively, no differences in apoptosis levels between loading areas were found – evidence that mechanical load regulates cartilage matrix composition but does not affect chondrocyte viability. The results suggest that MMPs play a key role in regulating the balance of structural proteins of the articular cartilage matrix according to local mechanical demands.

The adsorption of a Cs atom on planar (C6H6 and C24H12) and nonplanar (C20H10 and C21H9) carbon clusters has been studied using the density-functional theory, with the local-density approximation and atomic pseudopotentials. Binding energies as a function of separation have been calculated for several configurations of the Cs atom on the different substrates. The adsorption on sites above the center of carbon rings is more stable than adsorption on top of carbon atoms and C-C bonds. In the case of the curved clusters, adsorption on the concave side is preferred compared to the convex side. The Cs bonding is stronger on the nonplanar clusters. The strength of the binding energy depends on two effects: the magnitude of the highest occupied molecular orbital-lowest unoccupied molecular orbital (LUMO) energy gap of the substrate, and the energy of the valence state of Cs relative to the LUMO of the substrate. Due to a favorable relative position of those two energy levels, charge transfer occurs from Cs to the two nonplanar clusters, and this provides an ionic contribution to the bonding. The analysis of the electronic density redistribution and of the local Fukui functions helps in the interpretation of the charge transfer and the reactivity.

The effects of the nuclear interaction on the pion atomic wavefunction are considered by means of a distorsion factor. The definition and the calculation of this factor for inclusive capture processes is the subject of this work. The sensitivity to the optical potential and nuclear density parametrization is considered. Systematic results for 1s, 2p and 3d levels are given for A⩽40 nuclei, and a fit in terms of ZA 1 3 is also given.

Redox titration of F1-ATPase from rat liver mitochondria referred to the modification of the hydrolytic activity on Mg-ATP has resulted in a three-step pattern, with three distinct jumps of activity separated by clear plateaus. The measured potentials ranged from −400 mV to +400 mV and were obtained by the addition of dithionite and ferricyanide. Electron exchange was facilitated with a mixture of different redox mediators. At pH 7.4 the midpoint potentials were +210 mV, +40 mV and −230 mV. These three midpoint potentials were displaced towards more negative values by 2,4-dinitrophenol or by an increase of the pH of the medium. The titration curves were described by n=2 Nernst equations.

The hydrolytic activity of rat liver F 1 -ATPase was stimulated up to 60% by FAD concentrations as low as 10-10 M. Stimulations as high as 100% were obtained with similar concentrations of CoQ.

1. 1. The kinetics of the Ca 2+ -ATPase activity of chicken skeletal myosin has been found to be of a biphasic type. 2. 2. DNP and SCN − increased Ca 2+ -ATPase activity, whereas CN − and HCO 3 − acted as inhibitors in the concentration range used. 3. 3. Upon raising substrate concentration, activation and inhibition constants for those modifiers responded also with an elevation of their values. 4. 4. The results are consistent with a model in which substrate and anionic modifiers occupy the same non-hydrolytic regulatory sites.

Density functional theory is used to study the electronic and atomic structure of small clusters of Na, Mg, Al and Pb. We study the quantityEN−1–EN, which has relevance to the processes of cluster growth and evaporation (EN is the total energy of the cluster withN atoms). By comparing the results of the jellium model with those of a more realistic model (although still simple) we are able to appreciate “structural” effects beyond the “electronic-shell effects” which form the essence of the predictions of the jellium model. The calculations predict formation of atomic shells and appreciable reconstruction as the cluster grows.

Aunque esta ley es conocida principalmente por laregulacio´n del consumo en espacios pu´blicos cerrados, en especialla prohibicio´n total de fumar en el trabajo y la restriccio´n parcialen los establecimientos de restauracio´n, tambie´n abarca otrosaspectos de gran importancia para la prevencio´n del tabaquismo,como las limitaciones en la venta y la regulacio´n de la publicidad,la promocio´n y el patrocinio. Adema´s, un capi´tulo se articula entorno a las medidas de promocio´n y educacio´n sanitaria, asi´ comoa la facilitacio´n de la deshabituacio´n taba´quica.La ley tuvo, desde sus inicios, un importante apoyo social.Segu´n las encuestas del Centro de Investigaciones Sociolo´gicas,en 2005 el 77,2% de la poblacio´n consideraba muy positivaesta regulacio´n

ResumenObjetivoEvaluar el impacto de la Ley 28/2005 de medidas sanitarias frente al tabaquismo en la prevalencia de la exposición al humo ambiental del tabaco (HAT) en Barcelona.MétodosEstudio de evaluación antes-después mediante comparación de dos encuestas transversales. Las fuentes de datos fueron las Encuestas de Salud de Barcelona de 2000 y 2006. Se analizó la prevalencia de exposición al HAT en población adulta no fumadora según el ámbito de exposición (hogar, trabajo y tiempo libre) y las variables sociodemográficas.ResultadosLa exposición al HAT en no fumadores en el hogar y el trabajo disminuyó significativamente (p

Clinical studies focused on outcomes of umbilical cord blood transplantation (UCBT) for patients with chronic myelogenous leukemia (CML) in need of allogeneic stem cell transplantation and lacking an HLA-matched adult donor are limited. We analyzed the outcome of 26 adults with CML receiving single-unit UCBT from unrelated donors after myeloablative conditioning at a single institution. Conditioning regimens were based on combinations of thiotepa, busulfan, cyclophospamide or fludarabine, and antithymocyte globulin. At the time of transplantation, 7 patients (27%) were in first chronic phase (CP), 11 (42%) were in second CP, 2 (8%) were in accelerated phase (AP), and 6 (23%) were in blast crisis (BC). The cumulative incidence (CI) of myeloid engraftment was 88% at a median time of 22 days and was significantly better for patients receiving higher doses of CD34+ cells. The CI of acute graft-versus-host disease (GVHD) grade II-IV was 61%, that of acute GVHD grade III-IV was 39%, and that of chronic extensive GVHD was 60%. Treatment-related mortality (TRM) was 41% for patients undergoing UCBT while in first or second CP and 100% for patients in AP or BC (P < .01). After a median follow-up of 8 years, none of the patients relapsed, giving an overall disease-free survival (DFS) at 8 years of 41%. The DFS for patients undergoing UCBT while in any CP was 59%. These results demonstrate that UCBT from unrelated donors can be a curative treatment for a substantial number of patients with CML. Advances in supportive care and better selection of cord blood units and patients are needed to improve TRM.

The amino acid leucine causes an increase of collagen α1(I) synthesis in hepatic stellate cells through the activation of translational regulatory mechanisms and PI3K/Akt/mTOR and ERK signaling pathways. The aim of the present study was to evaluate the role played by reactive oxygen species on these effects. Intracellular reactive oxygen species levels were increased in hepatic stellate cells incubated with leucine 5 mM at early time points, and this effect was abolished by pretreatment with the antioxidant glutathione. Preincubation with glutathione also prevented 4E-BP1, eIF4E and Mnk-1 phosphorylation induced by leucine, as well as enhancement of procollagen α1(I) protein levels. Inhibitors for MEK-1 (PD98059), PI3K (wortmannin) or mTOR (rapamycin) did not affect leucine-induced reactive oxygen species production. However, preincubation with glutathione prevented ERK, Akt and mTOR phosphorylation caused by treatment with leucine. The mitochondrial electron chain inhibitor rotenone and the NADPH oxidase inhibitor apocynin prevented reactive oxygen species production caused by leucine. Leucine also induced an increased phosphorylation of IR/IGF-R that was abolished by pretreatment with either rotenone or apocynin. Therefore, leucine exerts on hepatic stellate cells a prooxidant action through NADPH oxidase and mitochondrial Reactive oxygen species production and these effects mediate the activation of IR/IGF-IR and signaling pathways, finally leading to changes in translational regulation of collagen synthesis.

“Ecstasy” (3,4-methylenedioxymethamphetamine, MDMA) has been shown to be hepatotoxic for human users, but molecular mechanisms involved in this effect remained poorly understood. MDMA-induced cell damage is related to programmed cell death in serotonergic and dopaminergic neurons. However, until now there has been no evidence of apoptosis induced by MDMA in liver cells. Here we demonstrate that exposure to MDMA caused apoptosis of freshly isolated rat hepatocytes and of a cell line of hepatic stellate cells (HSC), as shown by chromatin condensation of the nuclei and accumulation of oligonucleosomal fragments in the cytoplasm. In both cell types, apoptosis correlated with decreased levels of bcl-x L , release of cytochrome c from the mitochondria and activation of caspase 3. In HSC, but not in hepatocytes, MDMA induced poly(ADP-ribose)polymerase (PARP) proteolysis. These results suggest that apoptosis of liver cells could be involved in the hepatotoxicity of MDMA.

Objetivos: Describir los niveles de exposición al humo ambiental de tabaco (HAT) a los que está expuesta la población en diferentes espacios públicos en Barcelona. Material y método: La nicotina en fase vapor se midió mediante monitores pasivos que contenían un filtro de 37 mm de diámetro tratado con bisulfato sódico en su interior. Se tomaron muestras en colegios de primaria y secundaria, hospitales, centros de atención primaria, estaciones de tren, transportes metropolitanos, universidades, aeropuerto, restaurantes y discotecas. Resultados: Los centros de enseñanza (primaria y secundaria) y los centros sanitarios presentan los niveles de exposición al HAT más bajos y en todos ellos la concentración media es < 1 μg/m³. En transportes y universidades los valores medios encontrados fueron: 2,16 μg/m3 en las estaciones de tren, 3,30 μg/m3 en el metro, 4,30 μg/m3 en los aeropuertos y 4,97 μg/m3 en las universidades. Los restaurantes y las discotecas son los lugares en los que la concentración es más alta, con valores medios de 12,36 μg/m³ en los restaurantes y 130,65 μg/m3 en las discotecas. En el caso de los centros de enseñanza primaria y secundaria, en el aeropuerto, en el metro y en restaurantes y discotecas todas las muestras tomadas revelan presencia de HAT. Asimismo, se encontró presencia de HAT en el 90% de las muestras tomadas en las estaciones de tren y en el 96% de las muestras de universidades. En hospitales se revela presencia de HAT en un 79% de las muestras tomadas, y en el caso de centros de atención primaria, en el 58%. Conclusiones: Los resultados confirman que el tabaquismo pasivo es un problema de salud pública que merece una especial atención en nuestro medio y ponen de manifiesto la necesidad de reforzar la implantación y especialmente el cumplimiento de políticas sin humo en lugares públicos y de trabajo. Objectives: To describe levels of exposure to environmental tobacco smoke (ETS) in various public places in Barcelona (Spain). Material and method: Vapor-phase nicotine was measured with passive samplers containing a sodium bisulfate treated filter with a 37 mm diameter. The places sampled were primary and secondary schools, hospitals, primary care centers, train stations, subways, universities, airports, restaurants and discotheques. Results: Primary and secondary schools and health centers had the lowest levels of ETS exposure, with mean concentrations of less than 1 μg/m3. The mean values found in transport and universities were 2.16 μg/m3 in train stations, 3.30 μg/m3 in subways, 4.30 μg/m3 in airports and 4.97 μg/m3 in universities. The highest concentrations were found in restaurants and discotheques, with mean values of 12.36 μg/m3 in restaurants and 130.65 μg/m3 in discotheques. All samples taken from primary and secondary schools, airports, subways, restaurants and discotheques contained ETS. Likewise, 90% of the samples taken from train stations and 96% of those from universities contained ETS. Seventy-nine percent of the samples from hospitals and 58% of those from primary care centers contained ETS. Conclusions: The results confirm that passive smoking is an important public health problem in Spain and that greater efforts are needed to enforce smoke-free policies in public spaces and workplaces.

A spherical average pseudopotential method (SAPS) is used to investigate some properties of compound alkali clusters. The effect that the substitution of a Sodium atom by a Lithium atom in a Nan cluster has on the stabilities and geometries is studied for n ≤ 21. We have found that substitution is always energetically possible. On the other hand equiatomic Na n Cs n clusters are considered in the size range n ≤ 16. We find a strong segregation effect of the Cesium atoms towards the cluster surface. This agrees with what happens in liquid Na x Cs1−x alloys.

The effects of citrate, free ATP, and bicarbonate on the activity of isolated rat liver mitochondrial ATPase have been studied. Citrate behaved as a weak noncompetitive inhibitor; free ATP at low concentrations was found to be an activator, whereas at high concentrations behaved as an inhibitor. Citrate competed with free ATP. Neither citrate nor free ATP competed with bicarbonate. The results obtained suggest the existence of at least two catalytic sites with ATP hydrolyzing activity and at least three regulatory sites: one for bicarbonate, and two for free ATP, one with low and another with high affinity. Citrate would compete with free ATP for the same sites. The interaction of free ATP with the high affinity site activated the enzyme, whereas its interaction with the low affinity site would lead to an inhibition.