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1.
The charged, electroactive bipyridine‐helicene‐ruthenium(III) complex [ 4 ] . +,PF6? has been prepared from 3‐(2‐pyridyl)‐4‐aza[6]helicene and a Ru‐bis‐(β‐diketonato)‐bis‐acetonitrile precursor (β‐diketonato: 2,2,6,6‐tetramethyl‐3,5‐heptanedionato). Its chiroptical properties (electronic circular dichroism and optical rotation) were studied both experimentally and theoretically and suggest the presence of 2 diastereoisomers, namely (P,Δ)‐ and (P,Λ)‐[ 4 ] . +,PF6? (denoted jointly as (P,Δ*)‐[ 4 ] . +,PF6?) and their mirror‐images (M,Λ)‐ and (M,Δ)‐[ 4 ] . +,PF6? ((M,Δ*)‐[ 4 ] . +,PF6?). The electrochemical reduction of (P,Δ*)‐[ 4 ] . +,PF6? to neutral complex (P,Δ*)‐ 4 was performed and revealed strong changes in the UV‐vis and electronic circular dichroism spectra. A reversible redox‐triggered chiroptical switching process was then achieved.  相似文献   

2.
Measurements of primary production by phytoplankton in four fish ponds over a period of one year revealed a distinct spatial variation in rate. The ponds were used for polyculture, monoculture, or a traditional system of fish culture. The rates of gross photosynthesis were highly correlated with temperature, free CO2, oxygen, inorganic nitrogen (NH4+, NO2, and NO3) and PO4-P. It was shown by step-wise multiple regression analysis that in the polyculture pond with a predominantly autotrophic metabolism, gross photosynthesis was the most significant factor correlated with fish growth. In another polyculture system in which the metabolism was mainly hetero-trophic, the influence of the photosynthesis rate was slight.  相似文献   

3.
4.
Phosphoramido acid esters (CH3)2NP(O)X(p-OC6H4-CH3) (containing P-Cl (1), P-O (2), P-F (3), P-CN (5), and P-N (4,6) bonds, X for 2, 4 and 6 is OCH3, (C2H5)2N and morpholin) have been synthesized to investigate the structure-activity study of AChE enzyme inhibition, through the parameters logP, δ31P and IC50. After their characterization by 31P, 31P{1H}, 13C, 1H NMR, IR and mass spectroscopy, the parameters logP and δ31P (31P chemical shift in NMR) were used to evaluated the lipophilicity and electronical properties. The ability of compounds to inhibit human AChE was predicted by PASS software (version 1.193), and experimentally evaluated by a modified Ellman's assay.  相似文献   

5.
The LiLa(MoO4)2:Sm3+ and LiLa(MoO4)2:Sm3+,Bi3+ phosphors were prepared using the citric-acid-fueled combustion method and the influence of concentrations of Bi3+ dopant on LiLa(MoO4)2:Sm3+ red luminescence was investigated. The LiLa(MoO4)2:Sm3+ and LiLa(MoO4)2:Sm3+,Bi3+ samples matched well with the scheelite structure and I41/a space group and did not detect structural changes. Under an excitation of 403 nm, the prepared LiLa(MoO4)2:Sm3+,Bi3+ phosphor was excited and produced orange-red emission. When compared with the LiLa(MoO4)2:Sm3+ phosphor, the LiLa(MoO4)2:Sm3+,Bi3+ phosphor exhibited enhanced fluorescence intensity because the Bi3+ dopant ions are doped as a sensitizer. The optimal doping concentrations of Sm3+ and Bi3+ were 5 and 1 mol%, respectively. Furthermore, the energy transfer from Bi3+ to Sm3+ is effective (3P14K11/2). Subsequently, the electrons in an unstable excited state were transferred to a stable ground state (4G5/26H5/2, 6H7/2, 6H9/2). The Commission Internationale de L'Eclairage (CIE) chromaticity coordinates of the optimized LiLa(MoO4)2:Sm3+,Bi3+ phosphor were situated in the orange-red region. The luminescence of the LiLa(MoO4)2:Sm3+,Bi3+ phosphor generated under near-ultraviolet (UV) irradiation could be used to produce a warm white light, indicating its possible applications in white light-emitting diodes.  相似文献   

6.
A single chiral cyclic α,α‐disubstituted amino acid, (3S,4S)‐1‐amino‐(3,4‐dimethoxy)cyclopentanecarboxylic acid [(S,S)‐Ac5cdOM], was placed at the N‐terminal or C‐terminal positions of achiral α‐aminoisobutyric acid (Aib) peptide segments. The IR and 1H NMR spectra indicated that the dominant conformations of two peptides Cbz‐[(S,S)‐Ac5cdOM]‐(Aib)4‐OEt ( 1) and Cbz‐(Aib)4‐[(S,S)‐Ac5cdOM]‐OMe (2) in solution were helical structures. X‐ray crystallographic analysis of 1 and 2 revealed that a left‐handed (M) 310‐helical structure was present in 1 and that a right‐handed (P) 310‐helical structure was present in 2 in their crystalline states. Copyright © 2010 European Peptide Society and John Wiley & Sons, Ltd.  相似文献   

7.
Microevolutionary trends in the dentition of the Red fox (Vulpes vulpes)   总被引:1,自引:1,他引:0  
Microevolutionary trends in dental traits were studied in a Polish population of the Red fox, Vulpes vulpes (Linnaeus, 1758). Changes in qualitative and quantitative traits over a 70‐year interval were analysed in 1453 museum specimens collected between 1927 and 1996. Over that period, there were qualitative trends towards increasing complication of occlusal crown surface in posterior premolars (i.e. P4, P3, P4) and I3. Other cheek teeth did not undergo directional change. Changes in trait correlations were assessed using samples from the 1960s and 1990s. The correlations between C1–C1 and M1–M2 increased, while correlation values in the incisor region (I1–I2, I1–I1, I1–I2, I3–I2), carnassial region (P4–M1, P4–M1 and M1–M1) and in P2–P1 decreased. These changes may be related to increasing dietary opportunism of the Red fox during the 20th century.  相似文献   

8.
The present study attempts to assess the potential of artificial substrates to enhance fish production in inland saline groundwater ponds through periphyton production. Grey mullet, Mugil cephalus, was cultured for 100 days in ponds with substrate (treatment ponds) and without substrate (control ponds). To enhance the surface area, bamboo poles were used as substrate. The periphyton population, pigment concentration and hydrobiological characteristics of pond water were monitored. The studies revealed little difference in most of the water quality parameters observed in the two treatments. However, turbidity (27.0 ± 0.1–35.0 ± 0.1 Nephalo Turbidity Unit (NTU)), chlorophyll ‘a’ (6.6 ± 0.6–7.6 ± 0.6 μg L?1), plankton population (phytoplankton 8.4 × 103–9.4 ×103 numbers L?1; zooplankton 4.0 × 103–5.1 × 103 numbers L?1) and NH4–N (2.0 ± 0.2–2.3 ± 0.1 mg L?1) were high in the treatment with no additional substrate; however, in the treatment with substrate the total Kjeldahl nitrogen (9.8 ± 0.8–10.8 ± 0.7 mg L?1) and o‐PO4 (0.1 ± 0.01–0.1 mg L?1) remained significantly (P < 0.05) higher. Highest periphyton biomass in terms of dry matter (DM) (0.8 ± 0.01–1.4 ±0.01 mg cm?2), ash free DM (0.4 ± 0.0–0.6 ± 0.01 mg cm?2), chlorophyll ‘a’ (3.1 ± 0.2–8.1 ± 0.8 μg cm?2) and pheophytin ‘a’ (1.9 ± 0.4–3.9 ± 0.5 μg cm?2) was observed at 50 cm depth in ponds provided with additional substrate. Fifteen plankton genera showing periphytic affinity colonized the bamboo substrates. Fish growth (mean fish weight 524.3 ± 8.7 g and SGR 2.5 ± 0.1) was significantly (P < 0.05) higher in ponds provided with additional substrate compared with control ponds (387.2 ± 6.0). Length–weight relationship (LWR) (W = cLn) also showed that the exponential value (‘n’) of length was high in substrate‐supported ponds (n = 2.36) in comparison with controls (n = 1.09). These studies suggest that a periphyton‐supported aquaculture system can be used successfully for the culture of herbivorous brackishwater fish species like M. cephalus in inland saline groundwaters and thus could contribute to the development of sound and sustainable aquaculture technology.  相似文献   

9.
Slavtcheva  T.  Dimitrova  V. 《Photosynthetica》2001,39(1):29-33
Net photosynthetic rate (P N) and dark respiration rate (R D) were measured in Vitis vinifera L. cvs. Dimiat 4/24 (23rd subculture), Dimiat 4/38 (22nd subculture), and Italian Riesling 3/47 (22nd subculture) on days 3, 2, and 1 (1st series) before transfer from the in vitro culture and on days 14, 15, 16 (2nd series) and 28, 29, 30 (3rd series) after the transfer. P N of in vitro and ex vitro plants was strongly affected by irradiance. P N and R D of in vitro plantlets were lower and transpiration rate (E) was higher compared to those of ex vitro plantlets. P N, R D, and E changed in the course of acclimation.  相似文献   

10.
Tropospheric ozone (O3) decreases photosynthesis, growth, and yield of crop plants, while elevated carbon dioxide (CO2) has the opposite effect. The net photosynthetic rate (P N), dark respiration rate (R D), and ascorbic acid content of rice leaves were examined under combinations of O3 (0, 0.1, or 0.3 cm3 m−3, expressed as O0, O0.1, O0.3, respectively) and CO2 (400 or 800 cm3 m−3, expressed as C400 or C800, respectively). The P N declined immediately after O3 fumigation, and was larger under O0.3 than under O0.1. When C800 was combined with the O3, P N was unaffected by O0.1 and there was an approximately 20 % decrease when the rice leaves were exposed to O0.3 for 3 h. The depression of stomatal conductance (g s) observed under O0.1 was accelerated by C800, and that under O0.3 did not change because the decline under O0.3 was too large. Excluding the stomatal effect, the mesophyll P N was suppressed only by O0.3, but was substantially ameliorated when C800 was combined. Ozone fumigation boosted the R D value, whereas C800 suppressed it. An appreciable reduction of ascorbic acid occurred when the leaves were fumigated with O0.3, but the reduction was partially ameliorated by C800. The degree of visible leaf symptoms coincided with the effect of the interaction between O3 and CO2 on P N. The amelioration of O3 injury by elevated CO2 was largely attributed to the restriction of O3 intake by the leaves with stomatal closure, and partly to the maintenance of the scavenge system for reactive oxygen species that entered the leaf mesophyll, as well as the promotion of the P N.  相似文献   

11.
Abstract: [3H]Ryanodine binding to, as well as functions of, ryanodine receptor intracellular Ca2+ release channel complexes are modulated by several adenosine-based compounds. In this study, we determined the effects of endogenous compounds termed diadenosine polyphosphates (ApnAs; n = 2–6 phosphate groups) on [3H]ryanodine binding to membranes prepared from rat brain and skeletal and cardiac muscle. Under low ionic strength buffer conditions, [3H]ryanodine binding to brain membranes was significantly increased by 171% with 333 µMP1,P5-di(adenosine-5′) pentaphosphate (Ap5A) and by 209% with the same concentration of the metabolism-resistant ATP analogue βγ-methyleneadenosine 5′-triphosphate (AMP-PCP) compared with control values for [3H]ryanodine binding of 9.6 ± 1.8 fmol/mg of protein. Dose-related increases in [3H]ryanodine binding were observed for all five ApnAs tested [P1,P2-di(adenosine-5′) pyrophosphate (Ap2A), P1,P3-di(adenosine-5′) triphosphate (Ap3A), P1,P4-di(adenosine-5′) tetraphosphate (Ap4A), Ap5A, and P1,P6-di(adenosine-5′) hexaphosphate (Ap6A)] as well as AMP-PCP; oxidized salts of ApnAs stimulated [3H]ryanodine binding to a greater degree than did nonoxidized ApnAs. The apparent rank order for the capacity of these agents to increase [3H]-ryanodine binding was oxidized Ap4A = oxidized Ap5A > oxidized Ap3A > Ap6A > AMP-PCP > Ap5A > Ap2A. Addition of the approximate EC50 dose of oxidized Ap4A (37 µM) increased the affinity (KD) of ryanodine receptors from 34 ± 7 to 12 ± 2 nM; the apparent binding site density (Bmax) was not significantly different from control values of 107 ± 33 fmol/mg of protein. Increases in [3H]-ryanodine binding by either oxidized Ap4A or nonoxidized Ap5A were not further enhanced by coincubation with AMP-PCP, which suggests a similar site of action for the ApnAs and AMP-PCP. [3H]Ryanodine binding to skeletal and cardiac muscle membranes was enhanced by addition of oxidized Ap4A, Ap5A, and AMP-PCP. Oxidized Ap4A increased the specific binding by ninefold in skeletal muscle and by threefold in cardiac muscle. These results suggest that ApnAs, at physiologically relevant concentrations, may serve as endogenous modulators of ryanodine receptor-gated Ca2+ release channels.  相似文献   

12.
The copper(II), nickel(II) and silver(I) complexes of the pentadentate 17-membered macrocycle 1, 12, 15-triaza-3, 4:9, 10-dibenzo-5,8-dithiacycloheptadecane (L1) have been prepared as perchlorates and characterized by X-ray crystallography. The N3S2 ligand uses all donor atoms for complexation. The copper coordination is square pyramidal with one sulfur atom in the axial site. Ni(II) displays an octahedral coordination by an interaction with a water molecule. The Ag(I) coordination is best described as a distorted pentagonal bipyramid. In [CuL1]2+ the 1, 4, 7-triazaheptane fragment of L1 is meridionally coordinated, but facially in [NiL1(H2O)]2+ and intermediate in [AgL1](ClO4). Crystal data for [CuL1](ClO4)2: monoclinic, space group P21/n, a = 13.153(8), b = 11.951(5), c = 17.880(8)Å, β = 110.29(4)°, Z = 4, R = 0.086 for 2732 independent reflections with I 2σ(I); [NiL1(H2O)](ClO4)2: monoclinic, P21/a, a = 10.771(2), b= 16.157(2), c = 15.286(2) Å, β =93.08(1)°, Z = 4, R = 0.085 for 1464 independent reflections with I 2σ(I); [AgL1](ClO4): monoclinic, P21/n, a = 12.708(9), b = 9.483(7), c = 19.569(13) Å, β= 103.95(6)°, Z = 4, R = 0.039 for 3600 independent reflections with I 2σ(I).  相似文献   

13.
Pervez  H.  Ashraf  M.  Makhdum  M.I. 《Photosynthetica》2004,42(2):251-255
The effects of potassium nutrition [0, 6.25, 12.50, 25.00 g(K) m–2 of K2SO4 or KCl] on gas exchange characteristics and water relations in four cultivars (CIM-448, CIM-1100, Karishma, S-12) of cotton were assessed under an arid environment. Net photosynthetic rate (P N) and transpiration rate (E) increased with increased K supply. The leaf pressure potential (p) increased significantly by the addition of 25.00 g(K) m–2 compared to zero K level. The water use efficiency (P N/E) was improved by 24.6 % under the highest K dose compared to zero K. There were positive correlations (0.99**, 0.98**, 0.95**, 0.97**) between K-doses and P N, E, p, and P N/E, respectively.  相似文献   

14.
Testicular and ovarian fragments of the protogynous Pacific wrasse Haliochoeres trimaculatus were incubated in vitro with [3H]pregnenolone ([3H]P5), [3H]17‐hydroxyprogesterone ([3H]17OHP4), non‐radioactive (nr) 17β‐oestradiol (nrE2) or nrP5 to identify the major gonadal steroidogenic pathways and steroid products in females and in the two male variants of this species, the terminal phase (TP) and initial phase (IP) males. Both testis and ovarian tissues exhibited 7 hydroxylase activity resulting in the formation of 7α‐hydroxypregnenolone (7OHP5) from [3H]P5, and many HPLC peaks were identified as products of testicular (c. 29) and ovarian (c. 23) steroidogenesis, and only c. 50% of these metabolites co‐eluted with authentic reference standards; only very small amounts of conjugated steroid were synthesized from any of the precursors. [3H]P5 was converted by testis mainly to 7αOHP5, and two unknown steroids, whereas [3H]17OHP4 metabolism gave rise to [3H]17,20β‐dihydroxy‐4‐pregnen‐3‐one (DHP), 11‐ketotestosterone (11KT), and two unknown steroids. For ovarian tissues, [3H]17OHP4 and [3H]P5 were metabolized to form E2, oestrone (E1), androstenedione (A4), 20α‐ and 20β‐dihydroprogesterone (20αDHP and 20βDHP), 7αOHP5 (from [3H]P5) and a major unknown. The HPLC steroid profiles for testis incubations for IP and TP males were similar, however, the steroidogenic response of the testis of TP males to human chorionic gonadotrophin, in vitro (determined by hormone assay), was significantly higher than that of IP males.  相似文献   

15.
The first successful enantioseparation of representative O,O‐diphenyl‐N‐arylthioureidoalkylphosphonates, (±)‐Ptc‐ValP(OPh)2 & (±)‐Ptc‐LeuP(OPh)2 and thiourylenedi(isobutyl phosphonate), Tcm[ValP(OPh)2]2 on analytical and semipreparative scale was achieved by high‐performance liquid chromatography using polysaccharide‐based chiral stationary phases (CPs). Atc‐AAP(OPh)2 was obtained using modified tricomponent condensations of the corresponding aldehydes, N‐arylthiourea and triphenyl phosphite whereas Tcm[ValP(OPh)2]2 by the condensations of aldehydes, thiourea, and triphenyl phosphite. The prepared, racemic (±)‐Atc‐AAP(OPh)2 [(±)‐Ptc‐ValP(OPh)2, (±)‐Ptc‐LeuP(OPh)2, (±)‐Ptc‐PglyP(OPh)2 and (±)‐Ntc‐PglyP(OPh)2] and racemic (±)‐Tcm[AAP(OPh)2]2 [(±)‐Tcm[NvaP(OPh)2]2 & (±)‐Tcm[ValP(OPh)2]2] were adequately characterized and used for chromatographic separations on high‐performance liquid chromatography–chiral stationary phases. The best results were obtained for (±)‐Ptc‐ValP(OPh)2, (±)‐Ptc‐LeuP(OPh)2 and (±)‐Tcm[ValP(OPh)2]2.  相似文献   

16.
Regester KJ  Lips KR  Whiles MR 《Oecologia》2006,147(2):303-314
Breeding adults and metamorphosing larval amphibians transfer energy between freshwater and terrestrial ecosystems during seasonal migrations and emergences, although rarely has this been quantified. We intensively sampled ambystomatid salamander assemblages (Ambystoma opacum,A. maculatum, and A. tigrinum) in five forested ponds in southern Illinois to quantify energy flow associated with egg deposition, larval production, and emergence of metamorphosed larvae. Oviposition by female salamanders added 7.0–761.4 g ash-free dry mass (AFDM) year−1 to ponds (up to 5.5 g AFDM m−2 year−1). Larval production ranged from 0.4 to 7.4 g AFDM m−2 year−1 among populations in three ponds that did not dry during larval development, with as much as 7.9 g AFDM m−2 year−1 produced by an entire assemblage. Mean larval biomass during cohort production intervals in these three ponds ranged from 0.1 to 2.3 g AFDM m−2 and annual P/B (production/biomass) ranged from 4 to 21 for individual taxa. Emergent biomass averaged 10% (range=2–35%) of larval production; larval mortality within ponds accounted for the difference. Hydroperiod and intraguild predation limited larval production in some ponds, but emerging metamorphs exported an average of 70.0±33.9 g AFDM year−1 (range=21.0–135.2 g AFDM year−1) from ponds to surrounding forest. For the three ponds where larvae survived to metamorphosis, salamander assemblages provided an average net flux of 349.5±140.8 g AFDM year−1 into pond habitats. Among all ponds, net flux into ponds was highest for the largest pond and decreased for smaller ponds with higher perimeter to surface area ratios (r 2 =0.94, P<0.05, n=5). These results are important in understanding the multiple functional roles of salamanders and the impact of amphibian population declines on ecosystems. Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users.  相似文献   

17.
A series of new monophosphates of 1-[2-(phosphonomethoxy)alkyl]thymines, such as PMPTp, 3-MeO-PMPTp, HPMPTp, and FPMPTp, were synthesized and tested for their ability to inhibit human thymidine phosphorylase. Kinetic measurements of enzyme activity were performed using thymidine and inorganic phosphate as the substrates. The data show that some monophosphates provide a considerable increase of the multisubstrate inhibitory effect. The highest inhibitory potency was found with (R)-FPMPTp 4c (K i dT = 4.09 ± 0.47 μM, K i(Pi) = 2.13 ± 0.29 μM) and (R) 3-MeO-PMPTp 4d (K i dT = 5.78 ± 0.71 μM, K i(Pi) = 2.71 ± 0.37 μM).  相似文献   

18.
Summary Analysis of regularly collected samples of soil and water from Makhana (Euryale ferox) growing ponds indicated that pH of soil and water were established near neutrality and C/N of soil near ten. Bicarbonate dominated soil extract while chloride dominated standing water. During grand growth period (March to June), Ca2++Mg2+, NH 4 + K+ increased while Na+ increased during decay of the plant (July to September) both in soil and plants. The soil had high contents of micro-nutrients, K and P. S.A.R. of soil was 3 to 4 times that of water. Free energy of exchange indicated stability and spontaneity.  相似文献   

19.
Net photosynthetic rate (P N) of tobacco plants grown with NH4-N as the only N source was the lowest all the times, while P N grown only with NO3-N was the greatest until 22nd day, and P N grown with both NO3-N and NH4-N (1 : 1) was the greatest. Maximal photochemical efficiency of photosystem 2 (PS2), Fv/Fm, and actual quantum yield of PS2 under actinic irradiation (ΦPS2) in plants grown with only NH4-N were greatest at early stage and then decreased and were smaller than those of other treatments. Photochemical quenching coefficient (qP) and non-photochemical quenching coefficient (qNP) in the NH4-N plants were the greatest at all times. Hence excessive NH4-N can decrease not only photochemical efficiency but also the efficiency of utilization of photon energy absorbed by pigments for photosynthesis. Therefore, excessive NH4-N is a hindrance to photosynthesis of flue-cured tobacco. On the other hand, tobacco cultured with an appropriate mixture of NO3-N with NH4-N can sufficiently utilize photon energy and increase the efficiency of energy transformation.  相似文献   

20.
The determination of growth constant of Aspergillus niger were obtained for semisolid cultures on cassava flour, Manihot esculenta, as a sole carbon source. As a consequence, a technique was developed that consisted of the use of a packed-bed microfermentor with a working volume of 16 cm3. The bed consisted of gelatinized and granulated cassava flour containing mineral nutrients and mold spores. The carbon dioxide produced during the respiration was drawn off with a current of air and then absorbed in a solution of sodium hydroxide. The absorption of CO2, P, was correlated with the specific growth rate μ, by means of the equation P=Keμt, where t is time and K is a constant. Ammonium nitrogen was used as a limiting substrate and its concentration was varied from 0.039 to 2.5% in dry base. The maximum growth rate, μmax, and the saturation constant, Ks, were 0.31 hr?1 and 0.065 mmol (NH4)2SO4/g total dry solids. Substrate inhibition was presented and the constant ki gave a value of 1.5 mmol (NH4)2SO4/g total dry solids. The proposed method is highly recommended for the evaluation of the semisolid fermentation of molds and for strictly aerobic bacteria and yeasts. It can be used especially in the evaluation of the growth of microorganisms on peanut shells, coffee residues, sugar cane bagasse, and other agricultural wastes.  相似文献   

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