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1.
The rhodium-catalysed hydroacylation of alkene is one of the most useful C–H bond activation processes. The C–C bond-forming reactions via C–H bond activation have extensively been the focus of study in the fields of organic and organometallic chemistry. In this work, density functional theory has been used to study Rh(I)-catalysed hydroacylation and hydrogenation of ethene with formic acid. All the intermediates and the transition states were optimised completely at the B3LYP/6-311++G(d,p) level (LANL2DZ(d) for Rh, P). Calculation results confirm that Rh(I)-catalysed hydroacylation of ethene is exothermic and the released Gibbs free energy is ? 60.39 kJ/mol. Rh(I)-catalysed hydrogenation of ethene is also exothermic and the released Gibbs free energy is ? 150.97 kJ/mol. Rh(I)-catalysed hydroacylation of ethene is the dominant reaction mode for Rh(I)-catalysed hydroacylation and hydrogenation of ethene with formic acid. In Rh(I)-catalysed hydroacylation of ethene, the H-transfer reaction is prior to the C–C bond-forming reaction. Therefore, the reaction mode ‘a’ (i.e. ca → M1 → TS1 → M2 → TS2a → M3a → TS3a → M4 → P1) is the dominant reaction pathway for Rh(I)-catalysed hydroacylation and hydrogenation of ethene. The theoretically predicted dominant product is propane acid. 相似文献
2.
Zhang JG Feng LN Shu YJ Zhang SW Zhang TL Yang L Wu M 《Journal of molecular modeling》2009,15(1):67-77
The tautomerism and intramolecular hydrogen shifts of 5-amino-tetrazole in the gas phase were studied in the present work.
The minimum energy path (MEP) information of 5-amino-tetrazole was obtained at the CCSD(T)/6–311G**//MP2/6–311G** level of
theory. The six possible tautomers of 1H, 4H-5-imino-tetrazole (a), 1H-5-amino-tetrazole (b), 2H-5-amino-tetrazole (c), 1H, 2H-5-imino-tetrazole (d), the mesoionic form (e) and 2H, 4H-5-imino-tetrazole (f) were investigated. Among these tautomers, there are 2 amino- forms, 3 imino- forms, and 1 mesoionic structure form. In all
the tautomers, 2-H form (c) is the energetically preferred one in the gas phase. In the imino- tautomers, the energy value of the compound d is similar as that of the compound f but it is higher than the energy value of the compound a. The potential energetic surface (PES) and kinetics for five reactions have been investigated. Reaction 2 (b→c) was hydrogen shifts only in which the 1-H and 2-H rearrangement. This means that the reaction 2 (b→c) is energetically favorable having an activation barrier of 45.66 kcal·mol−1 and the reaction energies (ΔE) is only 2.67 kcal·mol−1. However, the reaction energy barrier for tautomerism of reaction 1 (b→e) is 54.90 kcal·mol−1. Reaction 1 (b→a), reaction 3 (c→d), and reaction 5 (c→f) were amino- →imino- tautomerism reactions. The energy barriers of amino- →imino- tautomerism reactions required are 59.39,
65.57, 73.61 kcal·mol−1 respectively in the gas phase. The calculated values of rate constants using TST, TST/Eckart, CVT, CVT/SCT and CVT/ZCT methods
using the optimized geometries obtained at the MP2/6–311G** level of theory show the variational effects are small over the
whole temperature range, while tunneling effects are big in the lower temperature range for all tautomerism reactions.
Graphical Abstract Figure (DOC 45.0 KB) 相似文献
3.
Andreas Janshoff Claudia Steinem Manfred Sieber A. el Bayâ Marcus Alexander Schmidt H.-J. Galla 《European biophysics journal : EBJ》1997,26(3):261-270
The binding of cholera toxin, tetanus toxin and pertussis toxin to ganglioside containing solid supported membranes has been
investigated by quartz crystal microbalance measurements. The bilayers were prepared by fusion of phospholipid-vesicles on
a hydrophobic monolayer of octanethiol chemisorbed on one gold electrode placed on the 5 MHz AT-cut quartz crystal. The ability
of the gangliosides GM1, GM3, GD1a, GD1b, GT1b and asialo-GM1 to act as suitable receptors for the different toxins was tested by measuring the changes of quartz resonance frequencies.
To obtain the binding constants of each ligand-receptor-couple Langmuir-isotherms were successfully fitted to the experimental
adsorption isotherms. Cholera toxin shows a high affinity for GM1 (Ka = 1.8 ⋅ 108M–1), a lower one for asialo-GM1 (Ka = 1.0 ⋅ 107 M–1) and no affinity for GM3. The C-fragment of tetanus toxin binds to ganglioside GD1a, GD1b and GT1b containing membranes with similar affinity (Ka∼106 M–1), while no binding was observed with GM3. Pertussis toxin binds to membranes containing the ganglioside GD1a with a binding constant of Ka = 1.6 ⋅ 106 M–1, but only if large amounts (40 mol%) of GD1a are present. The maximum frequency shift caused by the protein adsorption depends strongly on the molecular structure of
the receptor. This is clearly demonstrated by an observed maximum frequency decrease of 99 Hz for the adsorption of the C-fragment
of tetanus toxin to GD1b. In contrast to this large frequency decrease, which was unexpectedly high with respect to Sauerbrey's equation, implying
pure mass loading, a maximum shift of only 28 Hz was detected after adsorption of the C-fragment of tetanus toxin to GD1a.
Received: 14 January 1997 / Accepted: 15 April 1997 相似文献
4.
Dhurairajan Senthilnathan Sundararajan Vaideeswaran Ponnambalam Venuvanalingam Gernot Frenking 《Journal of molecular modeling》2011,17(3):465-475
The antitumor activities of bent metallocenes [Cp–M–Cp]2+ (M = Ti, V, Nb, Mo) and complexes of them with guanine, adenine, thymine and cytosine nucleotides have been probed using
electronic structure calculations. DFT/BP86 calculations have revealed that the bent metallocene–nucleotide interaction strongly
depends on the stability of the hydrolyzed form of the bent metallocene dichloride [Cp2M]2+ species, and in turn the stability of the [Cp2M]2+ species strongly depends on the electronic structure of [Cp2M]2+. Detailed electronic structure and Walsh energy analyses have been carried out for the hydrolyzed forms of four [Cp–M–Cp]2+ (M = Ti, V, Nb, Mo) species to find out why the bent structure is unusually stable. Energy changes that occur during the
bending process in frontier molecular orbitals as well as the p(π)–d(π) overlap have been invoked to account for the anticipated antitumor activities of these species. The bonding situation
and the interactions in bent metallocene–nucleotide adducts were elucidated by fragment analysis. Of the four nucleotides
complexed with the four bent metallocenes, adenine and guanine show better binding abilities than the other two nucleotides.
Metallocenes of second-row transition metals exhibit better binding with pyrimidine-base nucleotides. In particular, the Lewis
acidic bent metallocenes interact strongly with nucleotides. The antitumor activity is directly related to the binding strength
of the bent metallocene with nucleotide adducts, and the computed interaction energy values correlate very well with the experimentally
observed antitumor activities. 相似文献
5.
Sandra Bolaño Maider Plaza Jesús Castro Luca Gonsalvi Alceo Macchioni 《Inorganica chimica acta》2010,363(3):509-516
A family of cationic and neutral highly water-soluble rhodium complexes [Cp∗Rh(PTA)3]Cl2 (1), [Cp∗RhCl2(THP)] (2), [Cp∗RhCl(THP)2]Cl (3), and [Cp∗RhCl(PTA)(THP)]Cl (4) have been synthesised and fully characterised [PTA = 1,3,5-triaza-7-phosphaadamantane; THP = tris(hydroxymethyl)phosphine]. Their water-solubility increases as the number of the phosphines coordinated to the metal centre is increased. The X-ray crystal structure of compound 2 was obtained and shows the presence of intermolecular hydrogen bonding. NMR speciation studies of [Cp∗RhCl2(PTA)] in deuterated water show the existence of several equilibria involving substitution processes in which the water molecules can substitute both chloride and PTA ligands. 相似文献
6.
Teresa Mancilla-Percino José Correa-Basurto José Trujillo-Ferrara Fernando R. Ramos-Morales Mario E. Acosta Hernández Jesús S. Cruz-Sánchez Margarita Saavedra-Vélez 《Journal of molecular modeling》2010,16(8):1377-1382
Two series of isoindolines 1(a–g) and 2(a–g) were found by docking calculations to be possible L-type Ca2+ channel (LCC) blockers. The theoretical 3-D model of the outer vestibule and the selective filter of the LCC was provided
by Professor Lipkind; this model consists of transmembrane segments S5 and S6 and P-loops contributed by each of four repeats
(I, II, III, and IV) of Cav 1.2. Therefore, two well-known LCC blockers, nifedipine 3 and (R)-ethosuccinimide 4 were also evaluated, and their binding sites on the LCC were identified and compared with those obtained for 1(a–g) and 2(a–g). Analysis of the results shows that the target compounds tested probably could be LCC blockers, since they interact with
or near the glutamic acid residues Glu393, Glu736, Glu1145 and Glu1446 (the EEEE locus), which belong to the LCC selectivity
region. The ∆G values for all of the Ca2+ channel ligands are between−10.78 and −3.67 (kcal mol−1), showing that LCC-1b, -1e and -1f complexes are more stable than the other compounds tested. Therefore, theoretically calculated dissociation constants K
d (μM) were obtained for all compounds. Comparing these values reveals that compounds 1b (0.0244 μM), 1e (0.0176 μM) and 1f (0.0125 μM) exhibit more affinity for the LCC than the other compounds. This screening shows that the two series of isoindolines
probably could act as LCC blockers. 相似文献
7.
Christopher D. Borman Colin G. Saysell A. G. Sykes 《Journal of biological inorganic chemistry》1997,2(4):480-487
Reactions (25 °C) of galactose oxidase, GOaseox from Fusarium NRRL 2903 with five different primary-alcohol-containing substrates RCH2OH:- D-galactose (I) and 2-deoxy-d-galactose (II) (monosaccharides); methyl-β-d-galactopyranoside (III) (glycoside);d-raffinose (IV) (trisaccharide); and dihydroxyacetone (V) have been studied in the presence of O2. The GOaseox state has a tyrosyl radical coordinated at a square-pyramidal CuII active site, and is a two-equivalent oxidant. Reactant concentrations were [GOaseox] (0.8–10 μM), RCH2OH (1.0–6.0 mM), and O2 (0.14–0.29 mM), with I=0.100 M (NaCl). The reactions, monitored at 450 nm by stopped-flow spectrophotometry, terminated with depletion of the O2. Each trace was fitted to the competing reactions GOaseox+RCH2 OH → GOaseredH2+RCHO (k
1), and GOaseredH2+O2→ GOaseox+H2O2 (k
2), with GOaseredH2 written as the doubly protonated two-electron-reduced CuI product. It was necessary to avoid auto-redox interconversion of GOaseox and GOasesemi . Information obtained at pH 7.5 indicates a 5 : 95 (ox : semi) "native" mix equilibration complete in ∼3 h. At pH >7.5,
rate constants 10–4 k
1 / M–1 s–1 for the reactions of GOaseox with (I) (1.19), (II) (1.07), (III) (1.29), (IV) (1.81), (V) (2.94) were determined. On decreasing the pH to 5.5, k
1 values decreased by factors of up to a half, and acid dissociation pK
as in the range 6.6–6.9 were obtained. UV-Vis spectrophotometric studies on GOaseox gave an independently determined pK
a of 6.7. No corresponding reactions of the Tyr495Phe variant were observed, and there are no similar UV-Vis absorbance changes
for this variant. The pK
a is therefore assigned to protonation of Tyr-495 which is a ligand to the Cu. The rate constant k
2 (1.01×107 M–1 s–1) is independent of pH in the range 5.5–9.0 investigated, suggesting that H+ (or H-atoms) for the O2 → H2O2 change are provided by the active site of GOasered . The CuI of GOasered is less extensively complexed, and a coordination number of three is likely.
Received: 4 February 1997 / Accepted: 16 May 1997 相似文献
8.
Theoretical studies of an unsymmetrical calix[4]-crown-5-N-azacrown-5 (1) in a fixed 1,3-alternate conformation and the complexes 1·K+(a), 1·K+(b), 1·K+(c) and 1·K+K+ were performed using density functional theory (DFT) at the B3LYP/6-31G* level. The fully optimized geometric structures
of the free macroligand and its 1:1 and 1:2 complexes, as obtained from DFT calculations, were used to perform natural bond
orbital (NBO) analysis. The two main types of driving force metal–ligand and cation–π interactions were investigated. NBO
analysis indicated that the stabilization interaction energies (E
2) for O…K+ and N…K+ are larger than the other intermolecular interactions in each complex. The significant increase in electron density in the
RY* or LP* orbitals of K+ results in strong host–guest interactions. In addition, the intermolecular interaction thermal energies (ΔE, ΔH, ΔG) were calculated by frequency analysis at the B3LYP/6-31G* level. For all structures, the most pronounced changes in the
geometric parameters upon interaction are observed in the calix[4]arene molecule. The results indicate that both the intermolecular
electrostatic interactions and the cation–π interactions between the metal ion and π orbitals of the two pairs that face the
inverted benzene rings play a significant role. 相似文献
9.
Park Y Zhang Z Laremore TN Li B Sim JS Im AR Ahn MY Kim YS Linhardt RJ 《Glycoconjugate journal》2008,25(9):863-877
Acharan sulfate content from African giant snail (Achatina fulica) was compared in eggs and snails of different ages. Acharan sulfate was not found in egg. Acharan sulfate disaccharide →4)-α-d-GlcNpAc (1→4)-α-l-IdoAp2S(1→, analyzed by SAX (strong-anion exchange)–HPLC was observed soon after hatching and increases as the snails grow.
Monosaccharide compositional analysis showed that mole % of glucosamine, a major monosaccharide of acharan sulfate, increased
with age while mole % of galactose decreased with age. These results suggest that galactans represent a major energy source
during development, while acharan sulfate appearing immediately after hatching, is essential for the snail growth. The structures
of neutral N-glycans released from eggs by peptide N-glycosidase F (PNGase F), were next elucidated using ESI-MS/MS, MALDI-MS/MS, enzyme digestion, and monosaccharide composition
analysis. Three types of neutral N-glycan structures were observed, truncated (Hex2–4-HexNAc2), high mannose (Hex5–9-HexNAc2), and complex (Hex3-HexNAc2–10) types. None showed core fucosylation. 相似文献
10.
Zhang L Liu HL Yang GH Huang XR Li Y Sun YB Sun CC 《Journal of molecular modeling》2011,17(12):3173-3181
A detailed doublet potential energy surface for the reaction of CH with CH3CCH is investigated at the B3LYP/6-311G(d,p) and G3B3 (single-point) levels. Various possible reaction pathways are probed.
It is shown that the reaction is initiated by the addition of CH to the terminal C atom of CH3CCH, forming CH3CCHCH 1 (1a,1b). Starting from 1 (1a,1b), the most feasible pathway is the ring closure of 1a to CH3–cCCHCH 2 followed by dissociation to P
3
(CH3–cCCCH+H), or a 2,3 H shift in 1a to form CH3CHCCH 3 followed by C–H bond cleavage to form P
5
(CH2CHCCH+H), or a 1,2 H-shift in 1 (1a, 1b) to form CH3CCCH2
4 followed by C–H bond fission to form P
6
(CH2CCCH2+H). Much less competitively, 1 (1a,1b) can undergo 3,4 H shift to form CH2CHCHCH 5. Subsequently, 5 can undergo either C–H bond cleavage to form P
5
(CH2CHCCH+H) or C–C bond cleavage to generate P
7
(C2H2+C2H3). Our calculated results may represent the first mechanistic study of the CH + CH3CCH reaction, and may thus lead to a deeper understanding of the title reaction. 相似文献
11.
The N-tosyl carbamates 4a–e, easily prepared starting from the Baylis–Hillman adducts 3a–e, underwent cyclization carried out with I2/NIS in the presence of NaH, to give the corresponding 2-oxo-1,3-oxazolidines 5a–e in good yield and total stereoselection when the substituent at C-5 is Ar. After the removal of tosyl group, followed by
the cleavage of the heterocyclic ring, the α-methyl-α-amino acids 8a,b and 10 were obtained in good yield as hydrochlorides. 相似文献
12.
In Escherichia coli, the F1FO ATP synthase b subunits house a conserved arginine in the tether domain at position 36 where the subunit emerges from the membrane. Previous
experiments showed that substitution of isoleucine or glutamate result in a loss of enzyme activity. Double mutants have been
constructed in an attempt to achieve an intragenic suppressor of the b
arg36→ile and the b
arg36→glu mutations. The b
arg36→ile mutation could not be suppressed. In contrast, the phenotypic defect resulting from the b
arg36→glu mutation was largely suppressed in the b
arg36→glu,glu39→arg double mutant. E. coli expressing the b
arg36→glu,glu39→arg subunit grew well on succinate-based medium. F1FO ATP synthase complexes were more efficiently assembled and ATP driven proton pumping activity was improved. The evidence
suggests that efficient coupling in F1FO ATP synthase is dependent upon a basic amino acid located at the base of the peripheral stalk. 相似文献
13.
Abstract From the carbolithiation of 6-bis-N,N-dimethylamino fulvene (3a) and different ortho-lithiated heterocycles (furan, thiophene and N-methylpyrrole), the corresponding lithium cyclopentadienide intermediate (4a–c) was formed. These three lithiated intermediates underwent a transmetallation reaction with TiCl4 resulting in bis-N,N-dimethylamino-functionalised titanocenes 5a–c. When these titanocenes were tested against LLC-PK cells, the IC50-values obtained were of 240, and 270 μM for titanocenes 5b and 5c, respectively. The most cytotoxic titanocene in this paper, 5a with an IC50-value of 36 μM was found to be approximately six times less cytotoxic than its mono-N,N-dimethylamino substituted analogue Titanocene C (IC50 = 5.5 μM) and almost ten times less cytotoxic than cisplatin, which showed an IC50-value of 3.3 μM, when tested on the LLC-PK cell line.
Graphical abstract Bis-(bis- (N,N-dimethylamino)-2-(N′-methylpyrrolyl)methylcyclopentadienyl) titanium (IV) dichloride, {η5-C5H4-CH[N(CH3)2]2[C5H3NCH3]}2TiCl2 was synthesised starting from 6-bis-(N,N-dimethylamino) fulvene and 2-N-methylpyrrolyl lithium. Herein, we present the synthesis and DFT structure of the titanocene and two further derivatives
followed by MTT-based cytotoxicity tests on pig kidney epithelial (LLC-PK) cells.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
14.
Campos PR 《Bulletin of mathematical biology》2004,66(3):473-486
We investigate the effect of deleterious mutations on the process of fixation of new advantageous mutants in an asexual population.
In particular we wish to study the dependence of the process on the strength of the deleterious mutations. We suppose the
existence of epistatic interaction between the genes. We study the model by means of branching process theory and also by
numerical simulations. Our results show the occurrence of two distinct regimes of behavior for the probability of fixation
of these variants. The occurrence of either regime depends on the ratio between the selective advantage of the beneficial
mutation s
b
and on the selective parameter for deleterious mutations s
b
. In the former, which takes place for s
b
/s
d
≲ 1, the probability of fixation increases with the epistasis parameter α, whereas for s
b
/s
d
≫ 1 the probability of fixation is a complex function of α and the mutation rate U. Surprisingly, we find that for the multiplicative landscape (α = 1) the probability of fixation P
fix is given by
where π (s
b
) is the probability of fixation for the two-allele model in the absence of mutations as calculated by Haldane (1927, Proc. Camb. Phil. Soc., 26, 220–230) and Kimura (1962, Genetics, 47, 713–719). 相似文献
15.
A series of crown ethers containing the azobenzene moiety incorporated into crowns of various sizes [Cr(O6), Cr(O7) and Cr(O8)] and their corresponding alkali metal cation (Li+, Na+, K+, Rb+) complexes have been studied theoretically. The density functional theory (DFT) method was employed to elucidate the stereochemical
structural natures and thermodynamic properties of all of the target molecules at the B3LYP/6-31 G(d) and LANL2DZ level for
the cation Rb+. The fully optimized geometries had real frequencies, thus indicating their minimum-energy status. In addition, the bond
lengths between the metal cation and oxygen atoms, atomic torsion angles and thermodynamic energies for complexes were studied.
Natural bond orbital (NBO) analysis was used to explore the origin of the internal forces and the intermolecular interactions
for the metal complexes. The calculated results show that the most significant interaction is that between the lone pair electrons
of electron-donating oxygens in the cis-forms of azobenzene crown ethers (cis-ACEs) and the LP* (1-center valence antibond lone pair) orbitals of the alkali-metal cations (Li+, Na+, K+ and Rb+). The electronic spectra for the cis-ACEs [cis-Cr(O6), cis-Cr(O7) and cis-Cr(O8)] are obtained by the time-dependent density functional theory (TDDFT) at the B3LYP/6-31 G(d) level. The spectra of the cis-isomers show broad π → π* (S0 → S2) absorption bands at 310–340 nm but weaker n → π* (S0 → S1) bands at 480–490 nm. The calculated results are in good agreement with the experimental results. 相似文献
16.
Ciesielski MJ Kozbor D Castanaro CA Barone TA Fenstermaker RA 《Cancer immunology, immunotherapy : CII》2008,57(12):1827-1835
Survivin is a tumor-associated antigen (TAA) that has significant potential for use as a cancer vaccine target. To identify
survivin epitopes that might serve as targets for CTL-mediated, anti-tumor responses, we evaluated a series of survivin peptides
with predicted binding to mouse H2-Kb and human HLA-A*0201 antigens in peptide-loaded dendritic cell (DC) vaccines. H2-Kb-positive, C57BL/6 mice were vaccinated using syngeneic, peptide-loaded DC2.4 cells. Splenocytes from vaccinated mice were
screened by flow cytometry for binding of dimeric H2-Kb:Ig to peptide-specific CD8+ T cells. Two survivin peptides (SVN57–64 and SVN82–89) generated specific CD8+ T cells. We chose to focus on the SVN57–64 peptide because that region of the molecule is 100% homologous to human survivin. A larger peptide (SVN53–67), containing multiple class I epitopes, and a potential class II ligand, was able to elicit both CD8+ CTL and CD4+ T cell
help. We tested the SVN53–67 15-mer peptide in a therapeutic model using a peptide-loaded DC vaccine in C57BL/6 mice with survivin-expressing GL261 cerebral
gliomas. This vaccine produced significant CTL responses and helper T cell-associated cytokine production, resulting in a
significant prolongation of survival. The SVN53–67 vaccine was significantly more effective than the SVN57–64 core epitope as a cancer vaccine, emphasizing the potential benefit of incorporating multiple class I epitopes and associated
cytokine support within a single peptide. 相似文献
17.
Syntheses of l-dopa 1a glucoside 10a,b and dl-dopa 1b glycosides 10–18 with d-glucose 2, d-galactose 3, d-mannose 4, d-fructose 5, d-arabinose 6, lactose 7, d-sorbitol 8 and d-mannitol 9 were carried out using amyloglucosidase from Rhizopus mold, β-glucosidase isolated from sweet almond and immobilized β-glucosidase. Invariably, l-dopa and dl-dopa gave low to good yields of glycosides 10–18 at 12–49% range and only mono glycosylated products were detected through glycosylation/arylation at the third or fourth
OH positions of l-dopa 1a and dl-dopa 1b. Amyloglucosidase showed selectivity with d-mannose 4 to give 4-O-C1β and d-sorbitol 8 to give 4-O-C6-O-arylated product. β-Glucosidase exhibited selectivity with d-mannose 4 to give 4-O-C1β and lactose 7 to give 4-O-C1β product. Immobilized β-glucosidase did not show any selectivity. Antioxidant and angiotensin converting enzyme inhibition
(ACE) activities of the glycosides were evaluated glycosides, out of which l-3-hydroxy-4-O-(β-d-galactopyranosyl-(1′→4)β-d-glucopyranosyl) phenylalanine 16 at 0.9 ± 0.05 mM and dl-3-hydroxy-4-O-(β-d-glucopyranosyl) phenylalanine 11b,c at 0.98 ± 0.05 mM showed the best IC50 values for antioxidant activity and dl-3-hydroxy-4-O-(6-d-sorbitol)phenylalanine 17 at 0.56 ± 0.03 mM, l-dopa-d-glucoside 10a,b at 1.1 ± 0.06 mM and dl-3-hydroxy-4-O-(d-glucopyranosyl)phenylalanine 11a-d at 1.2 ± 0.06 mM exhibited the best IC50 values for ACE inhibition.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
18.
E. A. Turovsky M. V. Turovskaya A. V. Berezhnov A. V. Tolmacheva N. P. Kaimachnikov L. P. Dolgacheva V. P. Zinchenko E. I. Maevskii V. V. Dynnik 《Biochemistry (Moscow) Supplemental Series A: Membrane and Cell Biology》2012,6(1):35-44
Experiments on cultured mouse adipocytes (9 days in vitro) using fluorescent microscopy have shown that activation of α1- and α2-adrenoceptors by norepinephrine (NE) or α2-adrenoreceptors by L-arginine evokes transient Ca2+ signals, while activation of m3-cholinoreceptors by acetylcholine (ACh) or betaine causes sustained or damped Ca2+ oscillations. The presence in the incubation medium of L-arginine at a low concentration (100–200 μM) is necessary for a vigorous manifestation of these effects, apparently due to
transition of protein kinase G (PKG) and phosphodiesterase V into an active state. In the presence of 1–10 mM L-arginine, the amplitude of the Ca2+ transient response to NE increases and signal duration decreases. ACh and NE upon a sequential addition mutually potentiate
their effects. Using an inhibitory analysis we show that the observed modes are related to the operation of a signaling pathway
with the participation of phosphatidylinositol 3-kinase (PI3K), protein kinase B (PKB), endothelial NO synthase (eNOS), cytoplasmic
guanylate cyclase (sGC), protein kinase G (PKG), ADP-ribosyl cyclase (CD38), and the ryanodine receptor (RyR). The formation
of several loops of positive feedbacks (PF) and negative feedbacks (NF) in the signaling system is possible: (i) short PF
loops due to Ca2+-induced Ca2+ release (CICR) from internal stores through the inositol trisphosphate receptor (IP3R) and RyR participating in the transient signal formation; (ii) long PF loop Ca2+ → eNOS → sGC → PKG → CD38 → RyR → Ca2+, which can provide necessary conditions for calcium oscillations arising from short PF loops (CICR); (iii) several NF loops
based on PKG-mediated inhibition of IP3R and activation of Ca2+-ATPases of sarco(endo)plasmic reticulum and of the plasma membrane providing a shutdown of signaling by the pathway phospholipase
C → IP3R → Ca2+ and limiting Ca2+ rise caused by the pathway PI3K → PKB → eNOS → sGC → PKG → CD38 → RyR → Ca2+. Convergence of signaling pathways that involve α1-, α2-, and m3-receptors and then Gβγ-subunits of Gq and Gq proteins acting on PI3Kγ can provide activation of cytoplasmic PKG, which plays a key role in producing transient responses,
in activation of Ca2+ removal and generation of [Ca2+]i oscillations. PKG inhibition (implemented here by KT5823 application) in the presence of any agonist results in rupture of
NF loops controlling Ca2+ transporting systems activity that leads to uncontrolled [Ca2+]i rise and cell death. 相似文献
19.
Priya R Tadwal VS Roessle MW Gayen S Hunke C Peng WC Torres J Grüber G 《Journal of bioenergetics and biomembranes》2008,40(4):245-255
The first low resolution solution structure of the soluble domain of subunit b (b
22–156) of the Escherichia coli F1FO ATPsynthase was determined from small-angle X-ray scattering data. The dimeric protein has a boomerang-like shape with a
total length of 16.2 ± 0.3 nm. Fluorescence correlation spectroscopy (FCS) shows that the protein binds effectively to the
subunit δ, confirming their described neighborhood. Using the recombinant C-terminal domain (δ91–177) of subunit δ and the C-terminal peptides of subunit b, b
120–140 and b
140–156, FCS titration experiments were performed to assign the segments involved in δ–b assembly. These data identify the very C-terminal tail b
140–156 to interact with δ91–177. The novel 3D structure of this peptide has been determined by NMR spectroscopy. The molecule adopts a stable helix formation
in solution with a flexible tail between amino acid 140 to 145. 相似文献
20.
Chen GT Yang M Song Y Lu ZQ Zhang JQ Huang HL Wu LJ Guo DA 《Applied microbiology and biotechnology》2008,77(6):1345-1350
Preparative-scale fermentation of ginsenoside Rb1 (1) with Acremonium strictum AS 3.2058 gave three new compounds, 12β-hydroxydammar-3-one-20 (S)-O-β-d-glucopyranoside (7), 12β, 25-dihydroxydammar-(E)-20(22)-ene-3-O-β-d-glucopyranosyl-(1→2)-β-d-glucopyranoside (8), and 12β, 20 (R), 25-trihydroxydammar-3-O-β-d-glucopyranosyl-(1→2)-β-d-glucopyranoside (9), along with five known compounds, ginsenoside Rd (2), gypenoside XVII (3), ginsenoside Rg3 (4), ginsenoside F2 (5), and compound K (6). The structural elucidation of these metabolites was based primarily on one- and two-dimensional nuclear magnetic resonance
and high-resolution electron spray ionization mass spectra analyses. Among these compounds, 2–6 are also the metabolites of ginsenoside Rb1 in mammals. This result demonstrated that microbial culture parallels mammalian metabolism; therefore, A. strictum might be a useful tool for generating mammalian metabolites of related analogs of ginsenosides for complete structural identification
and for further use in pharmaceutical research in this series of compounds. In addition, the biotransformation kinetics was
also investigated. 相似文献