Nine minima were found on the intermolecular potential energy surface for the ternary system HNO3(CH3OH)2 at the MP2/aug-cc-pVDZ level of theory. The cooperative effect, which is a measure of the hydrogen-bonding strength, was probed in these nine conformations of HNO3…(CH3OH)2. The results are discussed here in terms of structures, energetics, infrared vibrational frequencies, and topological parameters. The cooperative effect was observed to be an important contributor to the total interaction energies of the cyclic conformers of HNO3…(CH3OH)2, meaning that it cannot be neglected in simulations in which the pair-additive potential is applied.
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
Mitochondrial production of H2O2 is low with NAD substrates (glutamate/pyruvate, 3 and 2 mM) (G/P) and increases over ten times upon further addition of succinate,
with the formation of a sigmoidal curve (semimaximal value at 290 μM, maximal H2O2 production at 600 μM succinate). Malate counteracts rapidly the succinate induced increased H2O2 release and moves the succinate dependent H2O2 production curve to the right. Nitric oxide (NO) and carbon monoxide (CO) are cytochrome c oxidase inhibitors which increase
mitochondrial ROS production. Cyanide (CN−) was used to mimic NO and CO. In the presence of G/P and succinate (300 μM), CN− progressively increased the H2O2 release rate, starting at 1.5 μM. The succinate dependent H2O2 production curve was moved to the left by 30 μM CN−. The Vmax was little modified. We conclude that succinate is the controller of mitochondrial H2O2 production, modulated by malate and CN−. We propose that succinate promotes an interaction between Complex II and Complex I, which activates O2− production. 相似文献
Oligonucleotide analogues were synthesized whose internucleoside linker contains an amide bond and a methylamino group (C3′-NH-CO-CH2-N(CH3)-C5′). Melting curves for duplexes formed by modified oligonucleotides and natural oligonucleotides complementary to them were measured, and the melting temperatures and thermodynamic parameters of duplex formation were calculated. The introduction of one modified dinucleoside linker into the oligonucleotide only slightly decreases the melting temperatures of these duplexes compared with unmodified ones. The CD spectra of modified duplexes were studied, and their spatial structures are discussed. 相似文献
The nature of M–M bonding and aromaticity of [M2(NHCHNH)3]2(μ-E)2 (E?=?O, S; M?=?Nb, Mo, Tc, Ru, Rh) was investigated using atoms in molecules (AIM) theory, electron localization function (ELF), natural bond orbital (NBO) and molecular orbital analysis. These analyses led to the following main conclusions: in [M2(NHCHNH)3]2(μ-E)2 (E?=?O, S; M?=?Nb, Mo, Tc, Ru, Rh), the Nb–Nb, Ru–Ru, and Rh–Rh bonds belong to “metallic” bonds, whereas Mo–Mo and Tc–Tc drifted toward the “dative” side; all these bonds are partially covalent in character. The Nb–Nb, Mo–Mo, and Tc–Tc bonds are stronger than Ru–Ru and Rh–Rh bonds. The M–M bonds in [M2(NHCHNH)3]2(μ-S)2 are stronger than those in [M2(NHCHNH)3]2(μ-O)2 for M?=?Nb, Mo, Tc, and Ru. The NICS(1)ZZ values show that all of the studied molecules, except [Ru2(NHCHNH)3]2(μ-O)2, are aromaticity molecules. O-bridged compounds have more aromaticity than S-bridged compounds.
Graphical AbstractLeft Molecular graph, and right electron localization function (ELF) isosurface of [M2(NHCHNH)3]2(μ-E)2(E?=?O, S; M?=?Nb, Mo, Tc, Ru, Rh)
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
Paramagnetic relaxation enhancements (PRE) present a powerful source of structural information in nuclear magnetic resonance (NMR) studies of proteins and protein–ligand complexes. In contrast to conventional PRE reagents that are covalently attached to the protein, the complex between gadolinium and three dipicolinic acid (DPA) molecules, [Gd(DPA)3]3?, can bind to proteins in a non-covalent yet site-specific manner. This offers straightforward access to PREs that can be scaled by using different ratios of [Gd(DPA)3]3? to protein, allowing quantitative distance measurements for nuclear spins within about 15 Å of the Gd3+ ion. Such data accurately define the metal position relative to the protein, greatly enhancing the interpretation of pseudocontact shifts induced by [Ln(DPA)3]3? complexes of paramagnetic lanthanide (Ln3+) ions other than gadolinium. As an example we studied the quaternary structure of the homodimeric GCN4 leucine zipper. 相似文献
Herein, we describe a general strategy for the facile synthesis of a multifunctional amino acid derivative bearing both fluorescent
and photolabile groups such as the lysine derivative NvocLys(CO(CH2)5NH–NBD)OCH2CN (1) that can be used as a biophysical tool for studying protein structure. The synthetic strategy involves functionalization
of the amine groups while the amino acid is attached to a solid support, followed by esterification of the carboxylic acid
in solution. The solid support protects the caboxylic acid, preventing a side reaction associated with the synthesis in solution
and obviating the need for chromatographic purification of several intermediates. This synthetic strategy can be used for
the preparation of a variety of amino acid derivatives with unusual α-amine and side chain functionalities. 相似文献
The interaction of the diastereomeric complexes Λ-[Ru(bpy)2(m-GHK)]Cl2 and Δ-[Ru(bpy)2(m-GHK)]Cl2 (bpy is 2,2′-bipyridine, GHK is glycine–l-histidine–l-lysine) with the deoxynucleotide duplex d(5′-CGCGATCGCG)2 was studied by means of 1H NMR spectroscopy. At a Δ-isomer to DNA ratio of 1:1, significant shifts for the metal complex are observed, whereas there is negligible effect on
the oligonucleotide protons and only one intermolecular nuclear Overhauser effect (NOE) is present at the 2D nuclear Overhauser
enhancement spectroscopy spectrum. The 1Η NMR spectrum at ratio 2:1 is characterized by a slight shift for the Δ-isomer’s bpy aromatic protons as well as significant shifts for the decanucleotide G4 H1′ and Η2″, A5 H2, G10 H1′, T6 NH and G2 NH protons. Furthermore, at ratio 2:1, 11 intermolecular NOEs are observed. The majority of the NOEs involve the sugar Η2′
and Η2″ protons sited in the major groove of the decanucleotide. Increasing the Δ-isomer to d(CGCGATCGCG)2 ratio to 5:1 results in noteworthy spectral changes. The Δ-isomer’s proton shifts are reduced, whereas significant shifts are observed for the decanucleotide protons, especially the
sugar protons, as well as for the exchangeable protons. Interaction is characterized by the presence of only one intermolecular
NOE. Furthermore, there is significant broadening of the imino proton signals as the ratio of the Δ-isomer to DΝΑ increases, which is attributed to the opening of the two strands of the duplex. The Λ-isomer, on the other hand, approaches the minor groove of the oligonucleotide and interacts only weakly, possibly by electrostatic
interactions. Photocleavage studies were also conducted with the plasmid pUC19 and a 158-bp restriction fragment, showing
that both diastereomers cleave DNA with similar efficiency, attacking mainly the guanines of the sequence probably by generating
active oxygen species.
Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users.
An erratum to this article can be found at 相似文献
The kinetics of rose bengal-sensitized photooxidation of tyrosine and several tyrosine-derivatives (tyr-D) named tyrosine methyl ester, tyrosine ethyl ester and tyrosine benzyl ester was studied in buffered pH 11 water, and buffered pH 11 micellar aqueous solutions of 0.01 M cetyltrimethylammonium chloride (CTAC) and 0.01 M-octylphenoxypolyethoxyethanol [triton X100 (TX100)]. Through time-resolved phosphorescence detection of singlet molecular oxygen (O(2)((1)Delta(g))) and polarographic determination of oxygen consumption, the respective bimolecular rate constants for reactive (k(r)) and overall (k(t)) quenching of the oxidative species by tyr-D were evaluated. Both rate constants behave in different fashion depending on the particular reaction medium. k(r)/k(t) values, increase in the sense CTAC相似文献
A novel S2O32? luminescent sensor (Cu2+-p-CPIP) was developed and the presence of S2O32? caused an obvious fluorescence enhancement at 420 nm upon excitation at 330 nm, which could be distinguished with the naked eye under a UV lamp. Remarkably, the compound exhibited excellent selective and sensitive response to S2O32? over other common anions with a micromolar limit of detection (0.442 μM) in DMSO/H2O (v/v, 1:1) buffer. The absorbance intensity and the color of Cu2+-p-CPIP solution changed gradually with the increase of S2O32? concentration. The proposed method was applied to the determination of S2O32? in milk samples and the recoveries were 97.5–105%. The preparation of Cu2+-p-CPIP exhibited the quick, simple and facile advantages. The results showed that Cu2+-p-CPIP can be a good candidate for simple, rapid and sensitive colorimetric detection of S2O32? in aqueous solution. 相似文献
Alkaline-earth metal complexes of the monoanionic form of the polyether ionophore monensin A were isolated for the first time
in solid state and were structurally characterized using various spectroscopic methods (IR, NMR, FAB-MS). The stoichiometric
reaction of monensic acid (MonH) with M2+ (M = Mg, Ca) in the presence of an organic base leads to the formation of mononuclear complexes of composition [M(Mon)2(H2O)2]. The structures of magnesium (1) and calcium (2) monensin complexes in the solid state were established by single crystal X-ray crystallography. The complexes crystallize
as [Mg(Mon)2(H2O)2]·5MeCN (1) and [Ca(Mon)2(H2O)2]·H2O·5MeCN (2) in the monoclinic P21 space group. The alkaline-earth metal ion is placed in a distorted octahedral environment, defined by two monensin anions
acting as bidentate ligands in the equatorial plane of the complex as well as by two water molecules occupying the axial positions
of the inner coordination sphere. The bactericidal activity of 1 and 2 was evaluated against aerobic Gram-positive microorganisms applying the double layer agar hole diffusion method. 相似文献
Prostaglandins (PGs) are lipid mediators that may play important roles in cancer, immunomodulation, and neurodegeneration. So, the quantitative analysis of PGs will therefore be important in order to understand the natural history of a range of diseases and may be used as a tool in the development of new biotherapeutics. However, such an analysis is problematic because of the small quantities of PGs present in the body. Here, we developed a matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-MS)-based analytical method for rapid and easy quantification of the ketone-containing PGs (15d-PGJ2etc.) as a targeted metabolomics platform. The chemical derivatization with Girard’s reagent P (GP) provided a good linearity (R2 > 0.99) between peak area and quantity of 15d-PGJ2 and highly improved sensitivity (limit of quantitation, LOQ: 1.25 pmol on a spot in MALDI plate). Finally, we utilized this method to directly characterize the interaction between peroxisome proliferatoractivated receptor gamma-ligand binding domain (PPARγ-LBD) and 15d-PGJ2. The 15d-PGJ2 was enriched by PPARγ-LBD and also the binding level of the ligand was dropped considerably by the treatment of PPARγ agonist such as rosiglitazone (about 0.61-fold reduction). Taken together, our MALDI-MS-based targeted metabolomics method for ketone-containing PGs may be applicable to elucidate the protein-metabolite interactions and to identify natural ligands for drug candidates. 相似文献
In experiments on rat brain slices using extracellular recording, we studied the effects of an agonist of β2 adrenoreceptors, metaproterenol (MPT), on reactions of pyramidal neurons of the hippocampal CA1 area induced by activation of GABAB receptors. Isolated application of an agonist of GABAB receptors, baclofen (10 μM), resulted in intense inhibition (by 50% or more during the 1st min of action) of orthodromic
field discharges (OFDs) in the pyramidal layer of the above-mentioned area of the hippocampus; the discharges were evoked
by electrical stimulation of Schaffer collaterals. On the 3rd to 4th min, OFDs were suppressed nearly completely. After washing
out from baclofen, the parameters of the evoked responses never completely restored to the initial level. In all cases, simultaneous
application of 150 μM MPT and 10 μM baclofen prevented full manifestation of the inhibitory effect of the latter agent on
OFDs of pyramidal neurons. The amplitude of evoked responses decreased, but the relative intensity of inhibition under these
conditions during 2-min-long application was significantly lower than that upon isolated action of baclofen. The recovery
of the amplitude of evoked responses in the course of washing out under conditions of parallel action of MPT was more rapid
and, in some cases, complete. Therefore, our experiments showed that GABAB-ergic inhibitory transmission in the rat hippocampal CA1 area in vitro can be suppressed significantly by the β2 adrenoreceptor agonist. 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
Sertoli cells were isolated from newborn calves and cultured in a medium supplemented with 0, 0.25, 0.50, 0.75, and 1.00 mg/L of sodium selenite to study their immune stimulatory effect, influence on cell’s viability, and expression of blood–testis barrier proteins (occludin, connexin-43, zonula occluden, E-cadherin) using quantitative PCR and western blot analyses. Results showed that medium supplemented with 0.50 mg/L of selenium significantly (P?<?0.05) promoted cell viability, upregulated toll-like receptor gene (TLR4), anti-inflammatory cytokines (IL-4, IL-10, TGFβ1), and expressions of blood–testis barrier proteins, and modulated expressions of pro-inflammatory cytokines (TNF-α, IL-1β, IFN-γ). Sertoli cells grown in culture medium supplemented with 0.25 mg/L of selenium significantly upregulated TLR4, IL-4, IL-10, TGFβ1, and blood–testis barrier proteins compared to the control group. Sodium selenite supplementation at 0.75 and 1.00 mg/L levels was cytotoxic and temporarily downregulated the expression of blood–testis barrier protein within 24 h after culture; however, commencing from 72 h post culture, increased cell viability and upregulation of expression of blood–testis barrier proteins were observed. In conclusion, the results of this study showed that selenium supplementation in the culture medium up to 0.50 mg/L concentration upregulates immune genes and blood–testis barrier constituent proteins of bovine Sertoli cells. 相似文献
In a quest to identify new ground-state triplet germylenes, the stabilities (singlet–triplet energy differences, ΔES–T) of 96 singlet (s) and triplet (t) M1-Ge-M2-M3 species were compared and contrasted at the B3LYP/6–311++G**, QCISD(T)/6–311++G**, and CCSD(T)/6–311++G** levels of theory (M1?=?H, Li, Na, K; M2?=?Be, Mg, Ca; M3?=?H, F, Cl, Br). Interestingly, F-substituent triplet germylenes (M3?=?F) appear to be more stable and linear than the corresponding Cl- or Br-substituent triplet germylenes (M3?=?Cl or Br). Triplets with M1?=?K (i.e., the K-Ge-M2-M3 series) seem to be more stable than the corresponding triplets with M1?=?H, Li, or Na. This can be attributed to the higher electropositivity of potassium. Triplet species with M3?=?Cl behave similarly to those with M3?=?Br. Conversely, triplets with M3?=?H show similar stabilities and linearities to those with M3?=?F. Singlet species of formulae K-Ge-Ca-Cl and K-Ge-Ca-Br form unexpected cyclic structures. Finally, the triplet germylenes M1-Ge-M2-M3 become more stable as the electropositivities of the α-substituents (M1 and M2) and the electronegativity of the β-substituent (M3) increase. 相似文献
The substitution reactions of H2GeLiF (G) with SiH3X (X = F, Cl, Br) were investigated using calculations performed at the QCISD/6-311++G (d, p)//B3LYP/6-311+G (d, p) level of theory. The results led to the following conclusions. (i) The substitutions are nucleophilic reactions. There are two substitution paths, I and II, which both lead to the germane H2GeFSiH3. The enantiomers of this germane are obtained via these two paths if an H in SiH3X is replaced with a different group or atom. (ii) Both substitution pathways show the same order of barrier heights (SiH3F > SiH3Cl > SiH3Br). The difference between the bond energies of Li–X and Si–X may explain the precedence among the substitution reactions of G with SiH3X. Path I has a lower activation barrier than path II, indicating that path I is more favorable. (iii) Comparison between the relevant insertion and substitution reactions shows that substitutions are more favorable and that the substitution product H2GeFSiH3 predominates over the insertion product. (iv) The substitution reactions of H2GeLiF with SiH3X are exothermic. 相似文献
We investigated the effect of mineral nitrogen forms on transfer of nitrogen (N) and zinc (Zn) from attached compartments to rhodes grass (Chloris gayana) colonised with arbuscular mycorrhizal fungi (AMF). After being pre-cultivated in substrates with adequate nutrient supply and either AMF inoculated (+AM) or left non-inoculated (?AM), rhodes grass was positioned adjacent to an outer compartment holding a similar substrate but applied with labelled nitrogen (15N) either as ammonium (NH4+) or nitrate (NO3?), and a high supply of Zn (150 mg kg?1 DS). Plant roots together with fungal mycelium were either allowed to explore the outer compartment (with root access) or only mycorrhizal hyphae were allowed (without root access). Within each access treatment, biomasses of rhodes grass were not significantly affected by AMF inoculation or N form. AMF contribution to plant 15N uptake was about double in NH4+ compared with NO3?-supplied treatments while the mycorrhizal influence on plant Zn uptake was insignificant. Without root access, the shoot 15N/Zn concentration ratio was up to ten-fold higher in +AM than –AM treatments and this ratio increase was clearly more pronounced in NH4+ than NO3?-supplied treatments. In conclusion, rhodes grass in symbiosis with the tested AMF acquired more N when supplied with ammonium. Moreover, there is clear indication that although the AMF have transported both nutrients (N and Zn), N was preferentially transferred as compared to Zn. We confirmed that, while rhodes grass is not able to prevent excessive Zn uptake via roots under conditions of high Zn, mycorrhiza is able to avoid excessive Zn supply to the host plant when the fungus alone has access to contaminated patches. 相似文献
Cleaving the abundant β-O-4 linkages in lignin is a key issue for producing value-added products by controlled lignin depolymerization. Herein, hydrothermally synthesized In2S3 nanoparticles were primarily used to photodegrade guaiacylglycerol-β-guaiacyl ether, a β-O-4 lignin model compound, under visible light irradiation. The as-synthesized In2S3 nanoparticles are found to be typical β-In2S3 nanocrystals of cubic phase and composed of large plate-like particles and small granular particles by using X-ray diffraction technique and field-emission scanning electron microscopy. The bandgap energy of the In2S3 nanoparticles is estimated to be 1.78 eV using an UV-visible diffuse reflectance spectroscopy. The photodegradation and structure variation of lignin model compound were evaluated by the variation of its UV-vis absorption spectrum, Fourier transform infrared spectrum, and X-ray photoelectron spectroscopy, while its degradation products were identified by using the gas chromatography-mass spectrometry. The results show that the as-synthesized In2S3 nanoparticles can photocatalytically break the β-O-4 linkage and oxidize the hydroxyl/methoxyl groups of lignin model compound under visible light irradiation although the lignin model compound is photo-resistant even under UV irradiation. The photodegradation products of lignin model compound consist of various aromatic monomers including value-added acetovanillone, vanillin, and coniferyl aldehyde. A possible pathway is proposed for photodegrading lignin model compound in the presence of the as-synthesized In2S3 nanoparticles under visible light irradiation. 相似文献
