Utilizing first-principles calculations, we studied the electronic and optical properties of C24, C12X6Y6, and X12Y12 fullerenes (X?=?B, Al; Y?=?N, P). These fullerenes are energetically stable, as demonstrated by their negative cohesive energies. The energy gap of C24 may be tuned by doping, and the B12N12 fullerene was found to have the largest energy gap. All of the fullerenes had finite optical gaps, suggesting that they are optical semiconductors, and they strongly absorb UV radiation, so they could be used in UV light protection devices. They could also be used in solar cells and LEDs due to their low reflectivities.
PROSTAGLANDIN (PG) F2αhas antifertility effects in many species1–3 but there are conflicting suggestions as to its mechanism of action. For example, it may cause the degeneration of the corpus luteum by decreasing blood flow in the uteroovarian vein4; alternatively, its action may be due to a hypersecretion of luteinizing hormone (LH) by the pituitary3,5. I have investigated the effects of PGF2α, E2 and E1 on pregnancy in mice and examined the mechanism of action of PGF2α. 相似文献
Subunit α of the Escherichia coli F1FO ATP synthase has been produced, and its low-resolution structure has been determined. The monodispersity of α allowed the studies of nucleotide-binding and inhibitory effect of 4-Chloro-7-nitrobenzofurazan (NBD-Cl) to ATP/ADP-binding. Binding constants (Kd) of 1.6 μM of bound MgATP-ATTO-647N and 2.9 μM of MgADP-ATTO-647N have been determined from fluorescence correlation spectroscopy data. A concentration of 51 μM and 55 μM of NBD-Cl dropped the MgATP-ATTO-647N and MgADP-ATTO-647N binding capacity to 50% (IC50), respectively. In contrast, no effect was observed in the presence of N,N′-dicyclohexylcarbodiimide. As subunit α is the homologue of subunit B of the A1AO ATP synthase, the interaction of NBD-Cl with B of the A-ATP synthase from Methanosarcina mazei Gö1 has also been shown. The data reveal a reduction of nucleotide-binding of B due to NBD-Cl, resulting in IC50 values of 41 μM and 42 μM for MgATP-ATTO-647N and MgADP-ATTO-647N, respectively. 相似文献
The poor norepinephrine innervation and high density of Gi/o-coupled α2A- and α2C-adrenoceptors in the striatum and the dense striatal dopamine innervation have prompted the possibility that dopamine could be an effective adrenoceptor ligand. Nevertheless, the reported adrenoceptor agonistic properties of dopamine are still inconclusive. In this study, we analyzed the binding of norepinephrine, dopamine, and several compounds reported as selective dopamine D2-like receptor ligands, such as the D3 receptor agonist 7-OH-PIPAT and the D4 receptor agonist RO-105824, to α2-adrenoceptors in cortical and striatal tissue, which express α2A-adrenoceptors and both α2A- and α2C-adrenoceptors, respectively. The affinity of dopamine for α2-adrenoceptors was found to be similar to that for D1-like and D2-like receptors. Moreover, the exogenous dopamine receptor ligands also showed high affinity for α2A- and α2C-adrenoceptors. Their ability to activate Gi/o proteins through α2A- and α2C-adrenoceptors was also analyzed in transfected cells with bioluminescent resonance energy transfer techniques. The relative ligand potencies and efficacies were dependent on the Gi/o protein subtype. Furthermore, dopamine binding to α2-adrenoceptors was functional, inducing changes in dynamic mass redistribution, adenylyl cyclase activity, and ERK1/2 phosphorylation. Binding events were further studied with computer modeling of ligand docking. Docking of dopamine at α2A- and α2C-adrenoceptors was nearly identical to its binding to the crystallized D3 receptor. Therefore, we provide conclusive evidence that α2A- and α2C-adrenoceptors are functional receptors for norepinephrine, dopamine, and other previously assumed selective D2-like receptor ligands, which calls for revisiting previous studies with those ligands. 相似文献
The nucleation, ice crystal shapes and thermodynamic stability of polar stratospheric clouds particles are interesting concerns owing to their implication in the ozone layer destruction. Some of these particles are formed by conformers of H2O, HNO3, and H2SO4. We carried out calculations using density functional theory (DFT) to obtain optimized structures. Several stable trimers are achieved —divided in two groups, one with HNO3 moiety, second with H2SO4 moiety— after pre-optimization at B3LYP/6-31G and subsequently optimization at B3LYP/aug-cc-pVTZ level of theory. For both most stable conformers five H2O molecules are added to their optimized trimers to calculate hydrated geometries. The OH stretching harmonic frequencies are provided for all aggregates. The zero-point energy correction (ZEPC), relative electronic energies (?E), relative reaction Gibbs free energies ?(?G)k-relative, and cooling constant (Kcooling) are reported at three temperatures: 188 K, 195 K, and 210 K. Shapes given in our calculations are compared with various experimental shapes as well as comparisons with their thermo-stabilities.
Graphical Abstract Facet shapes and thermo-stabilities of H2SO4?HNO3 hydrates involved in polar stratospheric clouds. IR spectrum of WNS-1+5W structure and its circular facet
F0F1ATPsynthase is now known to be expressed as a plasma membrane receptor for several extracellular ligands. On hepatocytes,
ecto–F0F1ATPsynthase binds apoA–I and triggers HDL endocytosis concomitant with ATP hydrolysis. Considering that inhibitor protein
IF1 was shown to regulate the hydrolytic activity of ecto–F0F1ATPsynthase and to interact with calmodulin (CaM) in vitro, we investigated the subcellular distributions of IF1, calmodulin (CaM), OSCP and β subunits of F0F1ATPsynthase in HepG2 cells. Using immunofluorescence and Western blotting, we found that around 50% of total cellular IF1 is localized outside mitochondria, a relevant amount of which is associated to the plasma membrane where we also found Ca2+–CaM, OSCP and β. Confocal microscopy showed that IF1 colocalized with Ca2+–CaM on plasma membrane but not in mitochondria, suggesting that Ca2+–CaM may modulate the cell surface availability of IF1 and thus its ability to inhibit ATP hydrolysis by ecto–F0F1ATPsynthase. These observations support a hypothesis that the IF1–Ca2+–CaM complex, forming on plasma membrane, functions in the cellular regulation of HDL endocytosis by hepatocytes. 相似文献
INTRODUCTION: We hypothesize that adenosine and PGE(2) could have a complementary immunosuppressive effect that is mediated via common cAMP-PKA signaling. MATERIALS AND METHODS: To test this hypothesis, the effect of adenosine and PGE(2) on the cytotoxic activity and cytokine production of lymphokine activated killer (LAK) cells was investigated. RESULTS: PGE(2) and adenosine inhibited LAK cells cytotoxic activity and production of INF-gamma, GM-CSF and TNF-alpha. In combination they showed substantially higher inhibition than each modality used alone. Using agonists and antagonists specific for PGE(2) and adenosine receptors we found that cooperation of PGE(2) and adenosine in their inhibitory effects are mediated via EP(2) and A(2A) receptors, respectively. LAK cells have 35-fold higher expression of EP(2) than A(2A). Combined PGE(2) and adenosine treatment resulted in augmentation of cAMP production, PKA activity, CREB phosphorylation and inhibition of Akt phosphorylation. Wortmannin and LY294002 enhanced the suppressive effects of adenosine and PGE(2). In contrast, Rp-8-Br-cAMPS, an inhibitor of PKA type I blocked their immunosuppressive effects, suggesting that the inhibitory effects of PGE(2) and adenosine are mediated via common pathway with activation of cAMP-PKA and inhibition of Akt. CONCLUSION: In comparison to other immunosuppressive molecules (TGF-beta and IL-10), adenosine and PGE(2) are unique in their ability to inhibit the executive function of highly cytotoxic cells. High intratumor levels of adenosine and PGE(2) could protect tumor from immune-mediated destruction by inactivation of the tumor infiltrating functionally active immune cells. 相似文献
We investigated correlated µs-ms time scale motions of neighboring 13C′–15N and 13Cα–13Cβ nuclei in both protonated and perdeuterated samples of GB3. The techniques employed, NMR relaxation due to cross-correlated chemical shift modulations, specifically target concerted changes in the isotropic chemical shifts of the two nuclei associated with spatial fluctuations. Field-dependence of the relaxation rates permits identification of the parameters defining the chemical exchange rate constant under the assumption of a two-site exchange. The time scale of motions falls into the intermediate to fast regime (with respect to the chemical shift time scale, 100–400 s?1 range) for the 13C′–15N pairs and into the slow to intermediate regime for the 13Cα–13Cβ pairs (about 150 s?1). Comparison of the results obtained for protonated and deuterated GB3 suggests that deuteration has a tendency to reduce these slow scale correlated motions, especially for the 13Cα–13Cβ pairs. 相似文献
The structures and stabilities of eleven N13+ and N13– isomers have been investigated with second-order Møller–Plesset (MP2) and density functional theory (DFT) methods. Five N13+ isomers and six N13– isomers are all reasonable local minima on their potential energy hypersurfaces. The most stable N13+ cation is structure C-2 with C2v symmetry, which contains a pentazole ring and two N4 open chains. It is different from those of the N7+ and N9+ clusters, but similar to the N11+ cluster. Meanwhile, the most stable N13– structure A-2 is composed of a pentazole ring and a six-membered ring connected by two nitrogen atoms. It is not only different from those of the N7– and N9– clusters, but also from the N11– cluster. The decomposition pathways of structures C-2 and A-2 were investigated at the B3LYP/(aug)-cc-pVDZ level. From the barrier heights of the structures C-2 and A-2 decomposition processes, it is suggested that C-2 is difficult to observe experimentally and A-2 may be observed as a short-lived species.
Figure Optimized geometrical parameters of N13+ isomer C-2相似文献
This investigation generated rovibrational energies and spectroscopic constants for systems of CCl4 with Ng (Ng?=?He, Ne, Ar), O2, D2O and ND3 from scattering experimental data, and the results presented are of interest for microwave spectroscopy studies of small halogenated molecules. The rovibrational spectra were obtained through two different approaches (Dunham and DVR) within the improved Lennard Jones (ILJ) model. Spectra were also generated within ordinary Lennard Jones and deviations suggest that the ILJ model should be preferred due to interactions beyond dispersion forces presented in these systems. Data from the literature and additional high level quantum mechanical calculations presented in this work show that these systems should not be considered as van der Waals complexes due to halogen bonding (HB) interactions, and this is especially true for the CCl4–D2O and CCl4–ND3 complexes. The charge displacement from the latter systems are one order of magnitude higher than the values from literature for CCl4 and He, Ne, Ar and O2 systems, and show significant deviations between DFT and Hartree-Fock values not previously reported in the literature. 相似文献
Nine microalgal species from the classes Bacillariophyceae, Cryptophyceae, Prymnesiophyceae and Dinophyceae were isolated from Australian waters, cultured to stationary phase and analyzed for their lipid and fatty acid composition and yield. Five species (Pavlova pinguis, Heterocapsa niei, Proteomonas sulcata, Navicula jeffreyi and Thalassiosira pseudonana) produced high proportions of triacylglycerol (TAG: 22–57% total lipid). An unidentified Navicula-like diatom (CS-786), despite having a low TAG content, had the highest EPA yield (5.8 mg L−1), due to high biomass and a high relative proportion of EPA. Heterocapsa niei had the highest DHA yield (2.9 mg L−1), due to a high cellular lipid and DHA content (171 pg cell−1 and 13.7 pg cell−1, respectively) despite its relatively low biomass. The desirable PUFA composition and yield of both diatom CS-786 and H. niei make them potential candidates for optimization of biomass and PUFA production for use as live-feeds in aquaculture. In addition, H. niei may have potential as a source of DHA for other uses. Low proportions (< 1.2%) of 24:6(n−3) accompanied by trace proportions of 24:5(n−6) were detected in most strains, while 28:8(n−3) was found in dinoflagellates and also in the prymnesiophyte P. pinguis. All non-diatomaceous species contained 26:7(n−3) in minor quantities. This is the first time these unusual C24 and C26 PUFA have been reported in microalgae and the first report of C28 PUFA in a microalga other than dinoflagellates. Possible biosynthetic reasons why these might occur in stationary phase cultures are considered and the likely dietary transfer of these PUFA to higher aquatic life is discussed. 相似文献
Oestrogens and 1α,25(OH)2-vitamin D3 (1,25-D3) are steroids that can provide effects by binding to their receptors localised in the cytoplasm and in the nucleus or the plasma membrane respectively inducing genomic and non-genomic effects. As confirmed notably by invalidation of the genes, coding for their receptors as tested with mice with in vivo and in vitro treatments, oestrogens and 1,25-D3 are regulators of spermatogenesis. Moreover, some functions of ejaculated spermatozoa as viability, DNA integrity, motility, capacitation, acrosome reaction and fertilizing ability are targets for these hormones. The studies conducted on their mechanisms of action, even though not completely elicited, have allowed the demonstration of putative interactions between their signalling pathways that are worth examining more closely. The present review focuses on the elements regulated by oestrogens and 1,25-D3 in the testis and spermatozoa as well as the interactions between the signalling pathways of both hormones. 相似文献
A preliminary study on the interaction of G protein (guanine triphosphate binding pro- tein) β1γ2 subunits and their coupled components in cell signal transduction was conducted in vitro. The insect cell lines, Sf9 (Spodoptera frugiperda) and H5 (Trichoplusia ni) were used to express the recombinant protein Gβ1γ2. The cell membrane containing Gβ1γ2 was isolated through affinity chromatography column with Ni-NTA agarose by FPLC method, and the highly purified protein was obtained. The adenylyl cyclase 2 (AC2) activity assay showed that the purified Gβ1γ2 could significantly stimulate AC2 activity. The interaction of β1γ2 subunits of G protein with the cytoplasmic tail of various mammalian adenylyl cyclases was monitored by BIAcore technology using NTA sensor chip, which relies on the phenomenon of surface plasmon resonance (SPR). The experiments showed the direct binding of Gβ1γ2 to the cytoplasmic tail C2 domain of AC2. The specific binding domain of AC2 with Gβ1γ2 was the same as AC2 activity domain which was stimulated by β1γ2. 相似文献
To analyze the influence of the beta-subunit on the kinetic properties of GlyR channel currents, alpha(1)-subunits and alpha(1)beta-subunits were transiently expressed in HEK 293 cells. A piezo dimorph was used for fast application of glycine to outside-out patches. The rise time of activation was dose dependent for both receptors and decreased with increasing glycine concentrations. Subunit composition had no effect on the time course of activation. Coexpression of alpha(1)- and beta-subunits resulted in a significantly lower EC(50) and a reduced slope of the dose-response curve of glycine compared with expression of alpha(1)-subunits alone. For both receptor subtypes, the time course of desensitization was concentration dependent. Desensitization was best fitted with a single time constant at 10-30 micro M, with two at 0.1 mM, and at saturating concentrations (0.3-3 mM) with three time constants. Desensitization of homomeric alpha(1)-receptor channels was significantly slower than that of alpha(1)beta-receptor channels. The time course of current decay after the end of glycine pulses was tested at different pulse durations of 1 mM glycine. It was best fitted with two time constants for both alpha(1) and alpha(1)beta GlyR channels, and increased significantly with increasing pulse duration. 相似文献
The dihydrated potassium salt of the complex anion [VO(O2)NTA]2− (NTA = nitrilotriacetate anion, [N(CH2-COO)3]3−) was thoroughly characterized by electronic and vibrational (infrared and Raman) spectroscopies. The bioactivity of the complex
on the cell proliferation was tested on three cell lines in culture (UMR106 rat osteosarcoma-derived cells, Caco-2 derived
from a human colon adenocarcinoma, and RAW 264.7, a macrophage murine cell line). 相似文献
We designed nine endohedral dodecahedrane heterodimers H@C20Hn-C20Hn@M (M = Cu, Ag, and Au, n = 15, 18, and 19) that may act as single-molecule spin switches, and we predicted theoretically that the ground states of the dimmers shift from low-spin states (S = 0) to the high-spin states (S = 1) under an external electric field applied parallel or perpendicular to the molecular symmetry axes, consisting well with the analyses of Stark effect. Molecular orbitals analyses provide an intuitive insight into the spin crossover behavior. This study expands the application of endohedral chemistry and provides new molecules for designing single-molecule spin switch. 相似文献
Different subtypes of opioid receptors (OR) were activated in rats in vivo to study the activation effect on the heart’s resistance to ischemia and reperfusion. It has been established that administration of deltorphin II, a selective δ2-OR agonist, lowered the infarct size/area at risk index (IS/AAR) by 23%. Naltrexone, naloxone methiodide (an OR inhibitor not penetrating the blood-brain barrier (BBB)), and naltriben (δ2-antagonist) eliminated the cardioprotective effect of deltorphin II, while BNTX (a δ1-antagonist) produced no effect on the cardioprotective action of the δ2-agonist. The infarct-reducing effect of deltorphin II was eliminated by administration of chelerythrine (a protein kinase C (PKC) inhibitor), glibenclamide (a KATP-channels inhibitor), and 5-hydroxydecanoate (a mitochondrial KATP-channel blocker). Administration of other opioids did not reduce the IS/AAR index. It has been established that all the deltorphins manifest antiarrhythmic potency. Other opioids do not produce any effect on the incidence of arrhythmia occurrences. The antiarrhythmic effect of deltorphin II was eliminated by preliminary administration of naltrexone, naloxone methiodide, and naltriben, but BNTX did not affect the δ2-agonist’s anti-arrhythmic effect. The preliminary administration of chelerythrine, a PKC inhibitor, eliminated the δ2 agonist’s antiarrhythmic action. However, glibenclamide and 5-hydroxydecanoate did not alter the antiarrhythmic effect by deltorphin II. Therefore, activation of the peripheral δ2-ORs reduces the infarct size and prevents the onset of arrhythmias. The antiarrhythmic effect of the δ2-OR stimulation is mediated by activating PKC and opening the mitochondrial KATP-channels. PKC participates in the antiarrhythmic effect of the δ2-OR activation, but this effect does not depend on the condition of KATP-channels. 相似文献
A new metal complex, Fe(Sal2dienNO3·H2O) (where Sal is salicylaldehyde and dien is diethylenetriamine), has been synthesized and characterized. The interactions
between the Fe(III) complex and calf thymus DNA has been investigated using UV and fluorescence spectra, viscosity, thermal
denaturation, and molecular modeling. The cleavage reaction on plasmid DNA has been monitored by agarose gel electrophoresis.
The experimental results show that the mode of binding of the complex to DNA is classical intercalation and the complex can
cleave pBR322 DNA. 相似文献
Summary The frequency of calcium oscillation reveals the platelet activation status, however, the biological significance of the periodic calcium responses and methods of communication with other integrin-mediated signals are not clear. RGD-containing disintegrin rhodostomin coated substrates were employed to enhance platelet spreading and calcium oscillation through direct binding and clustering of the receptor integrin IIb3. The results showed that the activation of phosphatidylinositol 3-kinase (PI3-K) and internal calcium pathways were crucial for IIb3 outside-in signaling. PI3-K antagonists wortmannin and LY294002 inhibited disintegrin substrates and induced platelet spreading and calcium oscillation. At the same time, pretreatment of platelets with the microsomal calcium–ATPase inhibitor thapsigargin to deplete internal calcium stores severely impaired the calcium oscillation as well as PI3-K activation and spreading on disintegrin substrates. Because inhibition of one pathway could inhibit the other, our data indicates that PI3-K and calcium oscillation are synergistically operated and form a positive-feedback regulation in integrin IIb3-mediated outside-in signaling. 相似文献
Similar to σ-hole interactions, the π-hole interaction has attracted much attention in recent years. According to the positive electrostatic potentials above and below the surface of inorganic heterocyclic compounds S2N2 and three SN2P2 isomers (heterocyclic compounds 1–4), and the negative electrostatic potential outside the X atom of XH3 (X = N, P, As), S2N2/SN2P2?XH3 (X = N, P, As) complexes were constructed and optimized at the MP2/aug-cc-pVTZ level. The X atom of XH3 (X = N, P, As) is almost perpendicular to the ring of the heterocyclic compounds. The π-hole interaction energy becomes greater as the trend goes from 1?XH3 to 4?XH3. These π-hole interactions are weak and belong to “closed-shell” noncovalent interactions. According to the energy decomposition analysis, of the three attractive terms, the dispersion energy contributes more than the electrostatic energy. The polarization effect also plays an important role in the formation of π-hole complexes, with the contrasting phenomena of decreasing electronic density in the π-hole region and increasing electric density outside the X atom of XH3 (X = N, P, As).
Graphical abstract Computed density difference plots for the complexes 3?NH 3 (a 1), 3?PH 3 (b 1), 3?AsH 3 (c 1) and electron density shifts for the complexes 3?NH 3 (a 2), 3?PH 3 (b 2),3?AsH 3 (c 2) on the 0.001 a.u. contour