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1.
A model of growth and substrate utilization for ferrous-iron-oxidizing bacteria attached to the disks of a rotating biological contactor was developed and tested. The model describes attached bacterial growth as a saturation function in which the rate of substrate utilization is determined by a maximum substrate oxidation rate constant (P), a half-saturation constant (Ks), and the concentration of substrate within the rotating biological contactor (S1). The maximum oxidation rate constant was proportional to flow rate, and the substrate concentration in the reactor varied with influent substrate concentration (S0). The model allowed the prediction of metabolic constants and included terms for both constant and growth-rate-dependent maintenance energies. Estimates for metabolic constants of the attached population of acidophilic, chemolithotrophic, iron-oxidizing bacteria limited by ferrous iron were: maximum specific growth rate (μmax), 1.14 h−1; half-saturation constant (Ks) for ferrous iron, 54.9 mg/liter; constant maintenance energy coefficient (m1), 0.154 h−1; growth-rate-dependent maintenance energy coefficient (m′), 0.07 h−1; maximum yield (Yg), 0.063 mg of organic nitrogen per mg of Fe(II) oxidized. 相似文献
2.
Dahmane Ouazia 《Analytical biochemistry》2010,398(1):45-563
α-Methylacyl-coenzyme A racemase (AMACR) catalyzes the epimerization of (2R)- and (2S)-methyl branched fatty acyl-coenzyme A (CoA) thioesters. AMACR is a biomarker for prostate cancer and a putative target for the development of therapeutic agents directed against the disease. To facilitate development of AMACR inhibitors, a continuous circular dichroism (CD)-based assay has been developed. The open reading frame encoding AMACR from Mycobacterium tuberculosis (MCR) was subcloned into a pET15b vector, and the enzyme was overexpressed and purified using metal ion affinity chromatography. The rates of MCR-catalyzed epimerization of either (2R)- or (2S)-ibuprofenoyl-CoA were determined by following the change in ellipticity at 279 nm in the presence of octyl-β-d-glucopyranoside (0.2%). MCR exhibited slightly higher affinity for (2R)-ibuprofenoyl-CoA (Km = 48 ± 5 μM, kcat = 291 ± 30 s−1), but turned over (2S)-ibuprofenoyl-CoA (Km = 86 ± 6 μM, kcat = 450 ± 14 s−1) slightly faster. MCR expressed as a fusion protein bearing an N-terminal His6-tag had a catalytic efficiency (kcat/Km) that was reduced 22% and 47% in the 2S → 2R and 2R → 2S directions, respectively, relative to untagged enzyme. The continuous CD-based assay offers an economical and efficient alternative method to the labor-intensive, fixed-time assays currently used to measure AMACR activity. 相似文献
3.
Small-scale hydrological variation determines landscape CO2 fluxes in the high Arctic 总被引:2,自引:0,他引:2
We explored the influence of small-scale spatial variation in soil moisture on CO2 fluxes in the high Arctic. Of five sites forming a hydrological gradient, CO2 was emitted from the three driest sites and only the wettest site was a net sink of CO2. Soil moisture was a good predictor of net ecosystem exchange (NEE). Higher gross ecosystem photosynthesis (GEP) was linked
to higher bryophyte biomass and activity in response to the moisture conditions. Ecosystem respiration (R
e) rates increased with soil moisture until the soil became anaerobic and then R
e decreased. At well-drained sites R
e was driven by GEP, suggesting substrate and moisture limitation of soil respiration. We propose that spatial variability
in soil moisture is a primary driver of NEE. 相似文献
4.
The reaction of (COD)PdCl2 (COD = 1,5-cyclooctadiene) with (3-Py)2SiR1R2 (3-Py = 3-pyridyl; R1 = Ph, R2 = Ph (m-pdps); R1 = Ph, R2 = Me (m-pmps)) in acetone affords single crystals consisting of cyclodimers, [PdCl2((3-Py)2SiR1R2)]2, whereas the same reaction in a mixture of dichloromethane and ethanol yields amorphous spheres consisting of cyclotrimers, [PdCl2((3-Py)2SiR1R2)]3. In a boiling chloroform solution, the cyclodimers are completely converted to cyclotrimers. These cyclotrimers, in the 10−60 °C range, are partly returned to cyclodimers. By contrast, the reaction of (COD)PdCl2 with (3-Py)2SiR1R2 (R1 = Bu, R2 = Me (m-pbms); R1 = dodecyl, R2 = Me (m-pddms)) yields amorphous spheres consisting of cyclotrimers irrespective of solvents. Both [PdCl2(m-pbms)]3 and [PdCl2(m-pddms)]3 are initially cyclotrimers in chloroform, but they exist as a mixture of cyclodimers and cyclotrimers in solution in the 10−60 °C range. The metallacycles tend to form cyclodimers in the order m-pdps > m-pmps > m-pbms > m-pddms. The equilibrium between cyclodimers and the cyclotrimers is sensitive to solvent, temperature, and concentration as well as molecular structure. 相似文献
5.
Sharma P Chauhan PS Dutt P Amina M Suri KA Gupta BD Suri OP Dhar KL Sharma D Gupta V Satti NK 《Steroids》2011,76(4):358-364
A new steroidal sapogenin molecule 1 having unique characteristics, 21-nor and unusual C19 carboxylic acid has been isolated from the roots of Asparagus racemosus. On the basis of chemical evidence, extensive spectroscopic analysis including two dimensional (2D) NMR and X-ray studies of single crystal, the structure of 1 was determined as (1S,2R,3S,8S,9S,10S,13S,14S,16S,17R,22R,25R)-21-nor-18β,27α-dimethyl-1β,2β,3β-trihydroxy-25-spirost-4-en-19β-oic acid. 1 crystallizes in monoclinic space group P21 with a = 9.295(2), b = 11.238(2), c = 11.376(2) Å; β = 91.993(4)°, Z = 2, Dcal = 1.344 Mg/m3. The structure was solved by direct methods and refined by full-matrix least-squares procedure to a final R-value of 0.0561 for 4064 observed reflections. 1 was tested against the type of immune responses generated during treatment in normal and immune-suppressed animals and detailed biological activity evaluation suggests it to be a potent immunostimulator. 相似文献
6.
Yolanda Pérez Isabel Sierra Mariano Fajardo Isabel del Hierro 《Inorganica chimica acta》2007,360(2):607-618
In view of the wide applicability and versatility of titanium based Lewis acids in selective organic synthesis including asymmetric synthesis, we have synthesized a family of mono and polyatomic titanium derivatives. The polymetallic complexes prepared are bridged by pyridimine, quinone and triazine based ligands. The synthesis of [{Ti(O-i-Pr)3(Oddbf)}2] (1), [Ti(O-i-Pr)2(Oddbf)2] (2), [{Ti(O-i-Pr)2(Oddbf)(OMent)}2] (3) (ddbfO = 2,3-dihydro-2,2-dimethyl-benzofuranoxo; MentO = (1R,2S,5R)-(−)-menthoxo), [{Ti(O-i-Pr)3(OMenpy)}2] (4), [Ti(O-i-Pr)2(OMenpy)2] (5) (MenpyO = (1S,2S,5R)-(−)-menthoxo-pyridine); [{(Ti(OR)3)2L}n] (RO = isopropoxo, (1R,2S,5R)-(−)-menthoxo) (6-11) and [{(Ti(O-i-Pr)3)3L}n] (12) was accomplished from a Lewis acid such as Ti(O-i-Pr)4, [{Ti(O-i-Pr)3(OMent)}2] or [Ti(OMent)4] and chelating ligands (ddbfOH = 2,3-dihydro-2,2-dimethyl-benzofuranol; MenpyOH = (1R,2S,5R)-(−)-5-methyl-2-isopropyl-1-(2′-pyridinyl)cyclohexan-1-ol; LH2 = 4,6-dihydroxy-2,5-diphenyl-pyrimidine, 2,4-dihydroxy-5,6-dimethyl-pyrimidine, 5,8-dihydroxy-1,4-napthoquinone, 2,5-dihydroxy-1,4-benzoquinone and LH3 = cyanuric acid) that provide a rigid framework for the metal centre. The molecular structure of 5 has been determined by single crystal X-ray diffraction studies. 相似文献
7.
Roderick C. Jones Michael G. Gardiner Vicki-Anne Tolhurst 《Inorganica chimica acta》2010,363(1):77-295
Ligands containing the 2-organochalcogenomethylpyridine motif with substituents in the 4- or 6-position of the pyridyl ring, R4,R6-pyCH2ER1 [R4 = R6 = H, ER1 = SMe (1), SeMe (2), SPh (6), SePh (7); R4 = Me, R6 = H, ER1 = SMe (3), SPh (8), SePh (9); R4 = H, R6 = Me, ER1 = SMe (4), SPh (10), SePh (11); R4 = H, R6 = Ph, ER1 = SMe (5), SPh (12), SePh (13)] are obtained on the reaction of R4,R6-pyMe with LiBun followed by R1EER1. On reaction with PdCl2(NCMe)2, the ligands with a 6-phenyl substituent form cyclopalladated species PdCl{6-(o-C6H4)pyCH2ER1-C,N,E} (5a, 12a, 13a) with the structure of 13a (ER1 = SePh) confirmed by X-ray crystallography; other ligands form complexes of stoichiometry PdCl2(R4,R6-pyCH2ER1). Complexes with R6 = H are monomeric with N,E-bidentate configurations, confirmed by structural analysis for 3a (R4 = Me, ER1 = SMe), 7a (R4 = H, ER1 = SePh) and 9a (R4 = Me, ER1 = SePh). Two of the 6-methyl substituted complexes examined by X-ray crystallography are oligomeric with trans-PdCl2(N,E) motifs and bridging ligands, trimeric [PdCl2(μ-6-MepyCH2SPh-N,S)]3 (10a) and dimeric [PdCl2(μ-6-MepyCH2SePh-N,Se)]2 (11a). This behaviour is attributed to avoidance of the Me···Cl interaction that would occur in the cis-bidentate configuration if the pyridyl plane had the same orientation with respect to the coordination plane as observed for 3a, 7a and 9a [dihedral angles 8.0(2)-16.8(2)°]. When examined as precatalysts for the Mizoroki-Heck reaction of n-butyl acrylate with aryl halides in N,N-dimethylacetamide at 120 °C, the complexes exhibit the anticipated trends in yield (ArI > ArBr > ArCl, higher yield for electron withdrawing substituents in 4-RC6H4Br and 4-RC6H4Cl). The most active precatalysts are PdCl2(R4-pyCH2SMe-N,S) (R = H (1a), Me (3a)); complexes of the selenium containing ligands exhibit very low activity. For closely related ligands, the changes SMe to SPh, 6-H to 6-Me, and 6-H to 6-Ph lead to lower activity, consistent with involvement of both the pyridyl and chalcogen donors in reactions involving aryl bromides. The precatalyst PdCl2(pyCH2SMe-N,S) (1a) exhibits higher activity for the reaction of aryl chlorides in Bun4NCl at 120 °C as a solvent under non-aqueous ionic liquid (NAIL) conditions. 相似文献
8.
Functional role of biomolecules viz., carbohydrates and proteins on acidogenic biohydrogen (H2) production was studied through the treatment of canteen based composite food waste. The performance was evaluated in an anaerobic sequencing batch reactor (AnSBR) at pH 6 with five variable organic loading conditions (OLR1, 0.854; OLR2, 1.69; OLR3, 3.38; OLR4, 6.54 and OLR5, 9.85 kg COD/m3-day). Experimental data depicted the feasibility of H2 production from the stabilization of food waste and was found to depend on the substrate load. Among the five loading conditions studied, OLR4 documented maximum H2 production (69.95 mmol), while higher substrate degradation (3.99 kg COD/m3-day) was observed with OLR5. Specific hydrogen yield (SHY) vary with the removal of different biomolecules and was found to decrease with increase in the OLR. Maximum SHY was observed with hexose removal at OLR1 (139.24 mol/kg HexoseR at 24 h), followed by pentoses (OLR1, 108.26 mol/kg PentoseR at 48 h), proteins (OLR1, 109.71 mol/kg ProteinR at 48 h) and total carbohydrates (OLR1, 58.31 mol/kg CHOR at 24 h). Proteins present in wastewater helped to maintain the buffering capacity but also enhanced the H2 production by supplying readily available organic nitrogen to the consortia. Along with carbohydrates and proteins, total solids also registered good removal. 相似文献
9.
A static granular bed reactor (SGBR) was used to treat swine wastewater at 24 and 16 °C. At 24 °C, the organic loading rate (OLR) was 0.7-5.4 kg COD/m3 day and the average chemical oxygen demand (COD) removal efficiency was 88.5%, respectively. Meanwhile, at 16 °C, the OLR was 1.6-4.0 kg COD/m3 day and the average COD removal efficiency was 68.0%, respectively. The SGBR acted as a bioreactor as well as a biofilter. After backwashing, the recovery of COD removal was not a function of an OLR but recovery time, while that of TSS removal was not a function of either recovery time or the OLR. The maximum substrate utilization rate (kmax) ratio was 1.89 between 24 and 16 °C, and the half velocity constant (Ks) ratio was 1.22, and the maximum specific growth rate (μmax) ratio was 4.71. In addition, the temperature-activity coefficient in this study was determined to be 1.09. 相似文献
10.
The kinetic, thermodynamic and isotherm modeling studies were carried out on adsorptive removal of Victoria blue (VB) dye using activated carbon, Ba/alginate and modified carbon/Ba/alginate polymer beads. The feasibility of sorption process was determined by varying the experimental parameters viz., dye concentration (4–20 mg L−1), contact time (10–90 min), pH (3–10), adsorbent dose (0.5–2.5 g) and temperature (303–343 K). Freundlich and Langmuir isotherms were determined and ascertained with the dimensionless separation factor (RL). Lagergren's pseudo-first order, pseudo-second order and intraparticle diffusion model equations were used to analyze the kinetics of the adsorption process. The thermodynamic consistency of adsorption was found with Gibbs free energy (ΔG°), changes in enthalpy (ΔH°) and entropy (ΔS°) were calculated using the Van’t Hoff plot. The polymer beads were characterized using Fourier Transform Infrared Spectroscopy (FTIR) and their morphology was determined by scanning electron microscopy (SEM). 相似文献
11.
Process of inorganic nitrogen transformation and design of kinetics model in the biological aerated filter reactor 总被引:3,自引:0,他引:3
As one of the plug-flow reactors, biological aerated filter (BAF) reactor was divided into four sampling sectors to understand the characteristics of elemental nitrogen transformation during the reaction process, and then the different characteristics of elemental nitrogen transformation caused by different NH3-N loadings, biological quantities and activities in each section were obtained. The results showed that the total transformation ratio in the nitrifying reactor was more than 90% in the absence of any organic carbon resource, at the same time, more than 65% NH3-N in the influent were nitrified at the filter height of 70 cm below under the conditions of the influent runoff 9-19 L/h, the gas-water ratio 4-5:1, the dissolved oxygen 3.0-5.8 mg/L and the NH3-N load 0.28-0.48 kg NH3-N/m3 d. On the base of the Eckenfelder mode, the kinetics equation of the NH3-N transformation along the reactor was Se = S0 exp(−0.0134D/L1.2612). 相似文献
12.
Biological kinetic (bio-kinetic) study of the anaerobic stabilization pond treatment of palm oil mill effluent (POME) was carried out in a laboratory anaerobic bench scale reactor (ABSR). The reactor was operated at different feed flow-rates of 0.63, 0.76, 0.95, 1.27, 1.9 and 3.8 l of raw POME for a day. Chemical oxygen demand (COD) as influent substrates was selected for bio-kinetic study. The investigation showed that the growth yield (YG), specific biomass decay (b), maximum specific biomass growth rate (μmax), saturation constant (Ks) and critical retention time (Θc) were in the range of 0.990 g VSS/g CODremoved day, 0.024 day−1, 0.524 day−1, 203.433 g COD l−1 and 1.908 day, respectively. 相似文献
13.
Rong-Hua Zhang Jin-Mei Yang G. Michael Blackburnb Zhao-Hui Zhou 《Inorganica chimica acta》2009,362(8):2643-144
Reactions of zinc(II) ion with racemic malic acid (C4H6O5 = H3mal) result in the isolation of four new zinc(II) malato complexes: (NH4)[Zn(R-H2mal)3] · H2O (1), trans-[Zn(R-H2mal)(S-H2mal)(H2O)2] · 2H2O (2), (NH4)2[Zn(R-Hmal)(S-Hmal)] · 2H2O (3), and [Zn2(R-Hmal)(S-Hmal)(H2O)4]n · 2nH2O (4). Three R-malic acids in 1 act as bidentate ligands via their alcoholic and the central carboxy groups with Zn(II) ion, leaving the terminal carboxylic acid groups free. The R- and S-malates of 2 coordinate in a bidentate manner with zinc ion in trans-form. In 3, Zn(II) ion is coordinated by R- and S-malates in a tridentate fashion via their alcoholic and two carboxy groups. Complex 4 forms a two-dimensional layered structure through the links of a new dimeric unit [Zn2(R-Hmal)(S-Hmal)(H2O)4] with one of the oxygen atoms from the terminal carboxy group of malate ligand. The coordination of malates depends on pH variation, on Zn:malate ratio, and also on temperature. Tridentate chelation of malate in 3 is found between pH 4.5-9.0. The soluble monomeric species 1-3 have been investigated using 13C NMR spectra by long-time acquisition. The solution NMR spectra indicate that zinc malate complexes dissociate in H2O (D2O). Obvious downfield shifts of the central carboxy carbon atoms in 1-3 are observed compared with those of free malate, which indicate that these zinc malate complexes dissociate in aqueous solution. 相似文献
14.
Glauber S.F. da SilvaHumberto Giusti Luiz G.S. BrancoMogens L. Glass 《Journal of thermal biology》2011,36(8):521-526
The control of pulmonary ventilation in South American lungfish Lepidosiren paradoxa is poorly understood. Interactions between temperature and hypoxia are particularly relevant due to large seasonal variations of its habitat. Therefore, we tested the hypothesis that the ventilatory responses to aerial hypoxia of Lepidosiren are highly dependent on ambient temperature. We used a pneumotachograph to measure pulmonary ventilation (VE), tidal volume (VT) and respiratory frequency (fR) during normoxic (21% O2) and hypoxic (12%, 10% and 7% O2) conditions at two temperatures (25 and 35 °C). Blood gases, arterial PO2 (PaO2), arterial PCO2 (PaCO2) and arterial pH (pHa) were also evaluated. At 25 °C, VE increased significantly at 10% and 7% hypoxic levels when compared to the control value (21% O2). At 35 °C, all hypoxic levels elicited a significant increase of VE relative to control values. VE is augmented mostly by increases of respiratory frequency (fR), and there were significant interactions (p<0.001) between aerial hypoxia and temperature. PaCO2 increased from ∼22 mmHg (normoxic value at 25 °C) to ∼32 mmHg (normoxic value at 35 °C). Concomitantly, the pHa decreased from 7.51 (25 °C) to 7.38 (35 °C). Hypoxia-induced hyperventilation caused a reduction in PaCO2 and an increase in pHa, which were more pronounced at 35 °C than at 25 °C, reflecting an increased hyperventilation under the high temperature. In conclusion, the magnitude of ventilatory response is highly temperature-dependent in L. paradoxa, which is important for an animal experiencing large seasonal variations. 相似文献
15.
S. Venkata Mohan G. MohanakrishnaR. Kannaiah Goud P.N. Sarma 《Bioresource technology》2009,100(12):3061-3068
Vegetable based market waste was evaluated as a fermentable substrate for hydrogen (H2) production with simultaneous stabilization by dark-fermentation process using selectively enriched acidogenic mixed consortia under acidophilic microenvironment. Experiments were performed at different substrate/organic loading conditions in concurrence with two types of feed compositions (with and without pulp). Study depicted the feasibility of H2 production from vegetable waste stabilization process. H2 production was found to be dependent on the concentration of the substrate and composition. Higher H2 production and substrate degradation were observed in experiments performed without pulp (23.96 mmol/day (30.0 kg COD/m3); 13.96 mol/kg CODR (4.8 kg COD/m3)) than with pulp (22.46 mmol/day (32.0 kg COD/m3); 12.24 mol/kg CODR (4.4 kg COD/m3)). Generation of higher concentrations of acetic acid and butyric acid was observed in experiments performed without pulp. Data enveloping analysis (DEA) was employed to study the combined process efficiency of system by integrating H2 production and substrate degradation. 相似文献
16.
The repellent activity of the essential oil of the catmint plant, Nepeta cataria (Lamiaceae), and the main iridoid compounds (4aS,7S,7aR) and (4aS,7S,7aS)-nepetalactone, was assessed against (i) major Afro-tropical pathogen vector mosquitoes, i.e. the malaria mosquito, Anopheles gambiae s.s. and the Southern house mosquito, Culex quinquefasciatus, using a World Health Organisation (WHO)-approved topical application bioassay (ii) the brown ear tick, Rhipicephalus appendiculatus, using a climbing repellency assay, and (iii) the red poultry mite, Dermanyssus gallinae, using field trapping experiments. Gas chromatography (GC) and coupled GC-mass spectrometry (GC-MS) analysis of two N. cataria chemotypes (A and B) used in the repellency assays showed that (4aS,7S,7aR) and (4aS,7S,7aS)-nepetalactone were present in different proportions, with one of the oils (from chemotype A) being dominated by the (4aS,7S,7aR) isomer (91.95% by GC), and the other oil (from chemotype B) containing the two (4aS,7S,7aR) and (4aS,7S,7aS) isomers in 16.98% and 69.83% (by GC), respectively. The sesquiterpene hydrocarbon (E)-(1R,9S)-caryophyllene was identified as the only other major component in the oils (8.05% and 13.19% by GC, respectively). Using the topical application bioassay, the oils showed high repellent activity (chemotype A RD50 = 0.081 mg cm−2 and chemotype B RD50 = 0.091 mg cm−2) for An. gambiae comparable with the synthetic repellent DEET (RD50 = 0.12 mg cm−2), whilst for Cx. quinquefasciatus, lower repellent activity was recorded (chemotype A RD50 = 0.34 mg cm−2 and chemotype B RD50 = 0.074 mg cm−2). Further repellency testing against An. gambiae using the purified (4aS,7S,7aR) and (4aS,7S,7aS)-nepetalactone isomers revealed overall lower repellent activity, compared to the chemotype A and B oils. Testing of binary mixtures of the (4aS,7S,7aR) and (4aS,7S,7aS) isomers across a range of ratios, but all at the same overall dose (0.1 mg), revealed not only a synergistic effect between the two, but also a surprising ratio-dependent effect, with lower activity for the pure isomers and equivalent or near-equivalent mixtures, but higher activity for non-equivalent ratios. Furthermore, a binary mixture of (4aS,7S,7aR) and (4aS,7S,7aS) isomers, in a ratio equivalent to that found in chemotype B oil, was less repellent than the oil itself, when tested at two doses equivalent to 0.1 and 0.01 mg chemotype B oil. The three-component blend including (E)-(1R,9S)-caryophyllene at the level found in chemotype B oil had the same activity as chemotype B oil. In a tick climbing repellency assay using R. appendiculatus, the oils showed high repellent activity comparable with data for other repellent essential oils (chemotype A RD50 = 0.005 mg and chemotype B RD50 = 0.0012 mg). In field trapping assays with D. gallinae, addition of the chemotype A and B oils, and a combination of the two, to traps pre-conditioned with D. gallinae, all resulted in a significant reduction of D. gallinae trap capture. In summary, these data suggest that although the nepetalactone isomers have the potential to be used in human and livestock protection against major pathogen vectors, intact, i.e. unfractionated, Nepeta spp. oils offer potentially greater protection, due to the presence of both nepetalactone isomers and other components such as (E)-(1R,9S)-caryophyllene. 相似文献
17.
Max Keller Melanie Kaske Tobias Holzammer Günther Bernhardt Armin Buschauer 《Bioorganic & medicinal chemistry》2013,21(21):6303-6322
The structurally related peptides neuropeptide Y (NPY), peptide YY (PYY) and pancreatic polypeptide (PP) are endogenous agonists of the NPY receptor (YR) family, which in humans comprises four functionally expressed subtypes, designated Y1R, Y2R, Y4R and Y5R. Nonpeptide antagonists with high affinity and selectivity have been described for the Y1R, Y2R and Y5R, but such compounds are still lacking for the Y4R. In this work, the structures of the high affinity selective (R)-argininamide-type Y1R antagonists BIBP3226 and BIBO3304 were linked via the guanidine or urea moieties to give homo-dimeric argininamides with linker lengths ranging from 31 to 41 atoms. Interestingly, the twin compounds proved to be by far less selective for the Y1R than the R-configured monovalent parent compounds. The decrease in selectivity ratio was most pronounced for Y1R versus Y4R subtype, resulting in comparable affinities of bivalent ligands for Y1R and Y4R (e.g. UR-MK177 ((R,R)-49): Ki = 230 nM (Y1R) and 290 nM (Y4R)). With a Ki value of 130 nM and a Kb value of 20 nM, UR-MK188 ((R,R)-51) was superior to all Y4R antagonists known to date. The S,S-configured optical antipodes of UR-MK177 and UR-MK188 (UR-MEK381 ((S,S)-49) and UR-MEK388 ((S,S)-51)) were synthesized to investigate the stereochemical discrimination by the different receptor subtypes. Whereas preference for R,R-configured argininamides was characteristic of the Y1R, stereochemical discrimination by the Y4R was not observed. This may pave the way to selective Y4R antagonists. 相似文献
18.
Hyuck Hee Lee Young Soo Gyoung Kyung-Eun Lee Soon W. Lee 《Inorganica chimica acta》2011,378(1):174-185
Bis(azido)bis(phosphine)-Pd(II) and -Pt(II) complexes, [M(N3)2L2] {L = PMe3, PEt3, PMe2Ph, dppe = 1,2-bis(diphenylphosphino)ethane}, underwent 1,3-dipolar cycloaddition with organic chiral isothiocyanates (R∗-NCS: R∗ = (S)-(+)-1-phenylethyl, (R)-(−)-1-phenylethyl, (±)-1-phenylethyl, (S)-(+)-1-indanyl) to give the corresponding tetrazole-thiolato Pd(II) and Pt(II) complexes, trans-[M{S[CN4(R∗)]}2L2] or [M{S[CN4(R∗)]}2(dppe)]. Spectroscopic (IR and NMR) and X-ray structural analyses of the products showed that the absolute configuration of the starting organic isothiocyanates is retained throughout the reaction. Further treatments of the isolated tetrazole-thiolato complexes with electrophiles such as HCl or benzoyl chloride produced heterocyclic compounds containing a tetrazole thione or a tetrazolyl sulfide group. In addition, organic tetrazole thiones, [S = {CN4H(R∗)}] containing a chiral moiety, were prepared from NaN3 and R∗-NCS in the presence of water. 相似文献
19.
An early step in the morphogenesis of the double-stranded DNA (dsDNA) bacteriophage HK97 is the assembly of a precursor shell (prohead I) from 420 copies of a 384-residue subunit (gp5). Although formation of prohead I requires direct participation of gp5 residues 2-103 (Δ-domain), this domain is eliminated by viral protease prior to subsequent shell maturation and DNA packaging. The prohead I Δ-domain is thought to resemble a phage scaffolding protein, by virtue of its highly α-helical secondary structure and a tertiary fold that projects inward from the interior surface of the shell. Here, we employ factor analysis of temperature-dependent Raman spectra to characterize the thermostability of the Δ-domain secondary structure and to quantify the thermodynamic parameters of Δ-domain unfolding. The results are compared for the Δ-domain within the prohead I architecture (in situ) and for a recombinantly expressed 111-residue peptide (in vitro). We find that the α-helicity (∼ 70%), median melting temperature (Tm = 58 °C), enthalpy (ΔHm = 50 ± 5 kcal mol− 1), entropy (ΔSm = 150 ± 10 cal mol− 1 K− 1), and average cooperative melting unit (〈nc〉 ∼ 3.5) of the in situ Δ-domain are altered in vitro, indicating specific interdomain interactions within prohead I. Thus, the in vitro Δ-domain, despite an enhanced helical secondary structure (∼ 90% α-helix), exhibits diminished thermostability (Tm = 40 °C; ΔHm = 27 ± 2 kcal mol− 1; ΔSm = 86 ± 6 cal mol− 1 K− 1) and noncooperative unfolding (〈nc〉 ∼ 1) vis-à-vis the in situ Δ-domain. Temperature-dependent Raman markers of subunit side chains, particularly those of Phe and Trp residues, also confirm different local interactions for the in situ and in vitro Δ-domains. The present results clarify the key role of the gp5 Δ-domain in prohead I architecture by providing direct evidence of domain structure stabilization and interdomain interactions within the assembled shell. 相似文献
20.
Key questions remain about the regulation and limits of cardiac function in fish challenged with elevated temperature, and to what extent sex differences influence cardiac performance. In this study, we investigated the in vivo relationship between heart rate (fH), stroke volume (SV), and cardiac output (Q) in quiescent, sexually immature rainbow trout (Oncorhynchus mykiss Walbaum) when challenged with: (1) an acute increase in water temperature from 14 to 24 °C at 2 °C h−1 and (2) a 50% reduction in fH at 24 °C, achieved through the incremental administration of zatebradine hydrochloride (total dose 2 mg kg body mass−1). There were no statistically significant (P<0.05) sex differences in cardiovascular function as temperature was raised to 24 °C. In males (N=10) and females (N=9), fH increased in a linear fashion with water temperature (from ∼60 beats min−1 at 14 °C to ∼125 beats min−1 at 24 °C; Q10=2.1), SV was largely unchanged, and systemic blood pressure (PDA) increased only slightly (by approx. 0.5 kPa) because the potential effect of increased Q on PDA was mostly offset by a 35% decrease in systemic vascular resistance (Rsys). At 24 °C, zatebradine treatment halved fH in both sexes, and yet Q was maintained at pre-treatment levels due to a doubling of SV. Overall, these results: (1) indicate that the in vivo cardiovascular response of quiescent, immature, male and female trout to elevated temperature is similar and (2) challenge the current dogma about how temperature affects cardiac function in fishes. Specifically, unlike previous in vitro or in situ studies, our data demonstrate that fish are capable of maintaining or even increasing SV at high temperatures. This suggests that aspects of cardiac control favor an increase in fH as temperatures rise, or that increases in cardiac output to meet the fish’s metabolic demands at high temperatures are met solely through an increase in fH because tachycardia is a requisite (unavoidable) physiological response. 相似文献