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1.
van Tonder EC Mahlatji MD Malan SF Liebenberg W Caira MR Song M de Villiers MM 《AAPS PharmSciTech》2004,5(1):86-95
The purpose of the study was to characterize the physicochemical, structural, and spectral properties of the 1∶1 niclosamide
and methanol, diethyl ether, dimethyl sulfoxide, N,N' dimethylformamide, and tetrahydrofuran solvates and the 2∶1 niclosamide
and tetraethylene glycol hemisolvate prepared by recrystallization from these organic solvents. Structural, spectral, and
thermal analysis results confirmed the presence of the solvents and differences in the structural properties of these solvates.
In addition, differences in the activation energy of desolvation, batch solution calorimetry, and the aqueous solubility at
25°C, 24 hours, showed the stability of the solvates to be in the order: anhydrate > diethyl ether solvate > tetraethylene
glycol hemisolvate > methanol solvate > dimethyl sulfoxide solvate > N,N' dimethylformamide solvate. The intrinsic and powder
dissolution rates of the solvates were in the order: anhydrate > diethyl ether solvate > tetraethylene glycol hemisolvate
> N,N' dimethylformamide solvate > methanol solvate > dimethyl sulfoxide solvate. Although these nonaqueous solvates had higher
solubility and dissolution rates than the monohydrous forms, they were unstable in aqueous media and rapidly transformed to
one of the monohydrous forms. 相似文献
2.
Calibration of the Minolta SPAD-502 leaf chlorophyll meter 总被引:24,自引:0,他引:24
Use of leaf meters to provide an instantaneous assessment of leaf chlorophyll has become common, but calibration of meter output into direct units of leaf chlorophyll concentration has been difficult and an understanding of the relationship between these two parameters has remained elusive. We examined the correlation of soybean (Glycine max) and maize (Zea mays L.) leaf chlorophyll concentration, as measured by organic extraction and spectrophotometric analysis, with output (M) of the Minolta SPAD-502 leaf chlorophyll meter. The relationship is non-linear and can be described by the equation chlorophyll (mol m–2)=10(M0.265), r
2=0.94. Use of such an exponential equation is theoretically justified and forces a more appropriate fit to a limited data set than polynomial equations. The exact relationship will vary from meter to meter, but will be similar and can be readily determined by empirical methods. The ability to rapidly determine leaf chlorophyll concentrations by use of the calibration method reported herein should be useful in studies on photosynthesis and crop physiology.Abbreviations Chl-
chlorophyll
- M-
SPAD-502 meter value 相似文献
3.
Protoplasts were isolated at high yields from actively growing callus and cell suspensions of cotyledons and needles of mature trees. The best protoplast growth response was obtained from cell suspensions of cotyledon and needle callus. Lower protoplast yields were obtained directly from young needles of flushing buds on explants from mature shoots (30-year-old trees) growing in vitro. In all cases, the first divisions, promoted by dimethyl sulfoxide, were observed in 10–45% of the protoplasts by 7–10 days. After 25–30 days, colonies of 8–10 cells were established. Browning of protoplast-derived cell cultures was observed within 40–45 days (cotyledons) and 20–25 days (mature tree sources).Abbreviations BA
N6-Benzyladenine
- DCR
Douglas-fir cotyledon revised medium
- 2,4-D
2,4-dichlorophenoxyacetic acid
- DMSO
dimethyl sulfoxide
- FDA
Fluorescein diacetate
- Mes
2-(N-morpholino) ethanesulfonic acid
- NAA
-naphthaleneacetic acid 相似文献
4.
Karavaev V. A. Baulin A. M. Gordienko T. V. Dovyd'kov S. A. Tikhonov A. N. 《Russian Journal of Plant Physiology》2001,48(1):38-44
The content of chlorophyll, the rate of O2 evolution, the slow phase of fluorescence induction, and photoinduced changes in the intensity of electron paramagnetic resonance (EPR) signal I from the reaction center of photosystem I (P+700) were studied in leaves of Vicia faba L. grown in 10–7–10–3 M aqueous solutions of CdCl2, SnCl2, CuCl2, and MgCl2. At low concentrations of heavy metal (Cd, Sn, and Cu) chlorides, the content of chlorophyll per fresh weight decreased. However, the rate of O2 evolution calculated per chlorophyll basis, O2/(t chlorophyll), increased. High concentrations of heavy metals significantly suppressed plant development and inhibited photosynthetic O2 evolution. In contrast, plant treatment with MgCl2 (10–5–10–3 M) resulted in an increase in the content of chlorophyll and a stimulation of leaf photosynthetic activity. A positive correlation between the F
M/F
T ratio and O2/(t chlorophyll) (r = 0.89, P > 0.999) was found. We observed a negative correlation between the values of P/P
0 of EPR signal I (white/far-red light) and O2/(tchlorophyll) (r = –0.89, P > 0.999). The data obtained indicate nonspecific and nonmonotone changes in the photosynthetic apparatus of plants treated with heavy metals: low concentrations of heavy metals (10–7–10–6 M) stimulated photosynthetic activity, whereas high concentrations (10–4–10–3 M) suppressed it. 相似文献
5.
Experimental support for the use of fluid aqueous organic solvent systems and subzero temperatures in mechanistic studies of -galactosidase is presented. The enzyme was stable and retained catalytic activity and structural integrity in 50% aqueous dimethyl sulfoxide and 60% aqueous methanol at 0°C; at lower temperatures higher concentrations of cosolvent may be successfully used. The effects of dimethyl sulfoxide on the catalytic and structural properties of the enzyme were investigated in detail. For the -galactoside-catalyzed h ydrolysis ofo-nitrophenyl--D-galactoside the value ofk
cat decreased in a linear manner with increasing cosolvent concentration, whereasK
m increased exponentially. The decrease ink
cat paralleled the decrease in water concentration, consistent with rate-limiting hydrolysis of a galactosylenzyme intermediate. The increase inK
m is attributed to less favorable partitioning of the substrate to the active site in the cryosolvent compared to aqueous solution. ThepH*-rate profile for this reaction at 0°C in 50% dimethyl sulfoxide was similar to that in aqueous solution, withpK*1=5.8 andpK*2=8.0. Linear Arrhenius plots, with energies of activation of 13.9 and 16.0 kcal mol–1, respectively, were obtained for the -galactosidase-catalyzed hydrolysis ofo-nitrophenyl- andp-nitrophenyl--D-galactosides in 50% dimethyl sulfoxide at temperatures to –57°C. Examination of the intrinsic fluorescence and ultraviolet spectra of the enzyme as a function of increasing cosolvent concentration showed no evidence for structural perturbation up to and including 50% dimethyl sulfoxide at 0°C. We conclude that these cryosolvent systems are suitable for mechanistic investigations of -galactosidase, in particular for trapping intermediates at subzero temperatures. 相似文献
6.
The formation of Triton X-100–silicotungstic acid complex was studied. Quantitative turbidimetric determination of the detergent based on this process was suggested. This method allows us to determine the complex formation at any wavelength in the range from 350 (350 =15600 cm–1 M–1) to 600 nm (600 = 9090 cm–1 M–1). The calibration curve for Triton X-100 recorded at 350 nm is linear in the concentration range of 0 to 30 g/ml. A sigmoid calibration curve was observed at longer wavelengths. A linear fragment of the calibration curve recorded at 600 nm was found at a concentration of Triton X-100 of about 5 g/ml. The complex nature of calibration curves can be explained by the heterogeneity of the complex dispersion. 相似文献
7.
Stefan Falk Jerry W. Leverenz Göran Samuelsson Gunnar Öquist 《Photosynthesis research》1992,31(1):31-40
The effects of a 60 min exposure to photosynthetic photon flux densities ranging from 300 to 2200 mol m–2s–1 on the photosynthetic light response curve and on PS II heterogeneity as reflected in chlorophyll a fluorescence were investigated using the unicellular green alga Chlamydomonas reinhardtii. It was established that exposure to high light acts at three different regulatory or inhibitory levels; 1) regulation occurs from 300 to 780 mol m–2s–1 where total amount of PS II centers and the shape of the light response curve is not significantly changed, 2) a first photoinhibitory range above 780 up to 1600 mol m–2s–1 where a progressive inhibition of the quantum yield and the rate of bending (convexity) of the light response curve can be related to the loss of QB-reducing centers and 3) a second photoinhibitory range above 1600 mol m–2s–1 where the rate of light saturated photosynthesis also decreases and convexity reaches zero. This was related to a particularly large decrease in PS II centers and a large increase in spill-over in energy to PS I.Abbreviations Chl
chlorophyll
- DCMU
3,(3,4-dichlorophenyl)-1,1-dimethylurea
- FM
maximal fluorescence yield
- Fpl
intermediate fluorescence yield plateau level
- F0
non-variable fluorescence yield
- Fv
total variable fluorescence yield (FM-F0)
-
initial slope to the light response curve, used as an estimate of initial quantum yield
-
convexity (rate of bending) of the light response curve of photosynthesis
- LHC
light-harvesting complex
- Pmax
maximum rate of photosynthesis
- PQ
plastoquinone
- Q
photosynthetically active photon flux density (400–700 nm, mol m–2s–1)
- PS
photosystem
- QA and QB
primary and secondary quinone electron acceptor of PS II 相似文献
8.
Frederico Pereira Brandini 《Hydrobiologia》1990,196(2):111-148
The physical and chemical environment, and the phytoplankton primary production of southeastern Brazil were studied in relation to the general oceanographic structure during two research cruises (winter and summer). In each cruise, a total of 91 stations were occupied. Data were collected on the spatial distribution of nutrients, phytoplankton biomass and photosynthetic capacity over the coastal, shelf and oceanic areas off São Paulo, Paraná and Santa Catarina States.During wintertime, the mixing processes between tropical warm waters of the Brazil Current and subantarctic waters of the Malvinas Current formed strong environmental gradients. The drainings of Rio de La Plata and Lagoa dos Patos are transported northwards by coastal currents, enriching the shelf waters off Santa Catarina State with inorganic nutrients and consequently increasing the chlorophyll a to the highest concentrations (> 3.5 mg m –3) measured during the two cruises. In slope waters chlorophyll values were always low (0.05–0.45 mg m –3). The chlorophyll within the euphotic layer varied from 8.8–36.7 and 1.2–18.5 mg m–2 during winter and summer, respectively.The surface photosynthetic rates during winter and summer cruises ranged respectively from 0.21–9.17 and 0.66–19.60 mgC/mgChl.a/h. The mean rates were higher in nearshore waters and decreased seaward.The thermal structure of the water column affected the vertical distribution of chlorophyll a and photosynthesis within the euphotic zone; During unstratified periods (winter) they were uniformly distributed but the occurrence of subsurface peaks of chlorophyll and strong photosynthetic inhibition of low light adapted cells in deeper layers are associated to the seasonal thermocline. Occasionally, upwelling of deep waters from shelf break enriched the deeper euphotic layers in offshore areas. Intensive upwelling was observed off Paranagua Bay (Parana State) and the mechanisms of its formation are discussed. 相似文献
9.
The solid-state conformation of the first N-protected ornithine derivative has been established by X-ray analysis. The hydrochloride of N-(9-fluorenyl)methoxycarbonyl-L-ornithine crystallises as diethyl ether solvate. The backbone (0, , , 1) torsion angles are (174.9°, –84.0°, 145.9°, –171.0°). The conformation of the urethane amide bond is trans. The ornithine aliphatic side chain adopts preferred fully extended conformation which is stabilised by the hydrogen bonding of the –NH3
+ group to the diethyl ether molecule, carboxyl group and Cl- anions. 相似文献
10.
Masayuki Katayama Ching Tsang Hou Norman C. Chen Takako Hirota Toshiko Kiribuchi Saburo Funahashi 《Bioscience, biotechnology, and biochemistry》2013,77(9):1661-1667
A procedure for fractional determination of soybean sterols is presented. Sterols in lipid extracts were fractionated into four classes, fatty acid esters, the free form, acylated glucosides and non-acylated glucosides, by Florisil column chromatography. Sterol contents in the four classes were determined colorimetrically with ferric chloride-perchloric acid reagent. Before the colorimetry, the fatty acid ester fraction was hydrolyzed with ethanolic KOH, and the sterol was isolated as tomatinide. The free sterol fraction was directly treated with tomatine solution. The tomatinides were dissociated with dimethyl sulfoxide. To avoid the contamination of pigments from the acylated glucoside fraction, the second Florisil column was rinsed with diethyl ether between the elution with the first solvent (0 to 50% diethyl ether in n-heхane) and that with the second solvent (0 to 30% methanol in diethyl ether). 相似文献
11.
A. Ghulam M. Kouach A. Racadot A. Boersma M. C. Vantyghem G. Briand 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1999,727(1-2)
An original method based upon high-performance liquid chromatography coupled to electrospray ionization mass spectrometry has been developed for corticosterone (B) quantification in human serum. After extraction by diethyl ether using triamcinolone (T) as an internal standard, solutes are separated on a C18 microbore column (250×1.0 mm, I.D.), using acetonitrile–water–formic acid (40:59.9:0.1, v/v/v) as the mobile phase (flow-rate 40 μl/min). Detection is performed on an API 1 single quadrupole mass spectrometer equipped with a ESI interface and operated in positive ionization mode. Corticosterone quantifications were realized by computing peak area ratios (B/T) of the serum extracts analyzed in SIM mode (m/z 347 and m/z 395 for B and T, respectively), and comparing them with the calibration curve (r=0.998). 相似文献
12.
The distribution of three phytoplanktonic size fractions was studied in an eutrophic lake. Size fractionation experiments were performed using cell enumeration by inverted microscopy and chlorophyll a estimation. The results were also compared with the ATP content in the analysed algal fractions.The (1–12 µm) fraction represented only on average 5 % of the total biomass, when estimated by the cell enumeration method, but made up 26 % of the total chlorophyll a and 33 % of the total ATP. This discrepancy confirms that cell enumeration with an inverted microscope seriously underestimates the nanoplankton biomass.The (12–45 µm) fraction made up to 50% of the total biomass regardless the method of analysis used. The chlorophyll a and biovolume estimation in this fraction were positively correlated.The contribution of algal species with large cell size (45–160 µm) to the total algal biomass was higher (39%) when based on their biovolume estimation than when on the chlorophyll a (27%). The low ATP contribution of this fraction (17%) may be attributable to high percentage of dead cells. 相似文献
13.
Severely yellowed ten-year-old spruce trees growing in the Vosges Mountains on an acidic soil were fertilised with Magnesium lime during the spring of 1990. The effects of this treatment were assessed 18 months later. A very significant improvement of the mineral status of the trees was detected, with increasing Mg contents in the needles, and as a consequence, reduced yellowing and improved chlorophyll content. Only slight differences with control trees were observed for height increase. Effects of this improved nutrition on photosynthesis were tested measuring net CO2 assimilation rates and chlorophyll a fluorescence. Light-saturated net assimilation rates of current-year needles were high, reaching 5.3 mol m–2 s–1 on a total needle area basis. The improvement in chlorophyll and Mg content had no significant effect on net assimilation rates or on any parameter describing photochemical functions of both current-and previous-year needles. Despite the strong inter-individual variability in needle chlorophyll and Mg contents (ranging from 0.2 to 0.8 mg g–1 fresh weight, and 0.05 to 0.5 mg g-1 dry weight respectively), photochemical efficiency of PS II under limiting irradiance only decreased significantly on older needles displaying Mg contents below 0.1 mg g–1. It is concluded from these results that spruce trees exhibit a high degree of plasticity with regard to Mg deficiency on acidic soils, and that improved Mg nutrition and increased chlorophyll content do not necessarily improve photosynthesis and height growth.Abbreviations A
light-saturated net CO2 assimilation rate (mol m–2 s–1)
- gw
light-saturated needle conductance to water vapour (mmol m–2 s–1)
- wp and wm
pre-dawn and mid-day needle water potential (MPa)
-
osmotic potential of sap expressed from needles (MPa)
- PFD
photosynthetic photon flux density (mol m–2 s–1)
- Fv/Fm
photochemical efficiency of PS II after 20 min dark adaptation
- F/Fm
'
photochemical efficiency of PS II reaction centres after 10 min at a PFD of 220 mol m–2 s–1 相似文献
14.
Samples of the phytoplankton in a freshwater lake, Lake Liddell, New South Wales (Lat: 32° 22 S, Long. 150° 1 E) were collected every 4 weeks between October 1987 and November 1988. Chlorophyll a concentrations ranged from 1.8 g 1–1 to 9.1 g 1–1 and were positively correlated with the following nutrient parameters: total and nett mass additions of nitrate/nitrite-N and total-N, total additions of Kjeldahl-N, and nett mass addition N-P ratios. There was no correlation between lake nutrient concentrations and chlorophyll a. Factors other than nutrient concentrations appeared to be effecting chlorophyll a concentrations as summer levels were low despite nutrient concentrations being at a maximum. In spring and summer the phytoplankton was dominated by chlorophytes, with dinoflagellates and diatoms most abundant in autumn. During winter cyanobacteria were the most abundant. The relative abundance of chlorophytes was positively correlated with in lake nitrate/nitrite-N concentrations whereas the relative abundance of cyanobacteria was negatively correlated with this parameter. Based on chlorophyll a concentrations and the phytoplankton flora Lake Liddell can be classified as mesotrophic. 相似文献
15.
S. Wanwimolruk 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1991,572(1-2)
A sensitive high-performance liquid chromatographic (HPLC) method for the quantitation of famotidine in human plasma is described. Clopamide was used as the internal standard. Plasma samples were extracted with diethyl ether to eliminate endogenous interferences. Plasma samples were then extracted at alkaline pH with ethyl acetate. Famotidine and the internal standard were readily extracted into the organic solvent. After evaporation of ethyl acetate, the residue was analysed by HPLC. The chromatographic separation was accomplished with an isocratic mobile phase consisting of acetonitrile—water (12:88, v/v) containing 20 mM disodium hydrogenphosphate and 50 mM sodium dodecyl sulphate, adjusted to pH 3. The HPLC microbore column was packed with 5 μm ODS Hypersil. Using ultraviolet detection at 267 nm, the detection limit for plasma famotidine was 5 ng/ml. The calibration curve was linear over the concentration range 5–500 ng/ml. The inter- and intra-assay coefficients of variation were found to be less than 10%. Applicability of the method was demonstrated by a bioavailability/pharmacokinetic study in normal volunteers who received 80 mg famotidine orally. 相似文献
16.
Chlorophyll (Chl) a and Chl b absorbances were determined in extracts from leaves of Citrus aurantium L. using the solvents diethyl ether (100 %), buffered 80 % aqueous acetone, and N,N-dimethyl formamide (DMF) (99.83 %). The respective standard deviations () and coefficients of variability (CV) were used to establish the errors obtained when using impure solvents. Buffered 80 % aqueous acetone gave an error of 2.1 % for Chl a and 7.1 % for Chl b, while DMF gave errors of 3.5 and 6.7 %, respectively. For current Chl determination we propose a non-abrasive method, which extracts 15 leaf discs (diameter 6 mm) with 10 cm3 of buffered 80 % aqueous acetone or DMF in hermetically sealed flasks during 24 h in darkness at 4 °C. 相似文献
17.
Max M. Tilzer 《Hydrobiologia》1988,162(2):163-171
In meseutrophic Lake Constance mean euphotic phytoplankton chlorophyll concentrations vary about 100-fold over the year. Concomitant fluctuations in euphotic depth (Zeu) and Secchi depth (Zs) are related to each other in a non-linear fashion that as a rough approximation can be expressed by Zeu 5 Zs.Secchi depth is to a great extent a function of beam attenuation of light which depends on the inherent optical properties of the water and is highly sensitive to light scattering from particles. Euphotic depth, by contrast, is a function of the vertical light attenuation coefficient which also depends on absorption and scattering, but is less sensitive to the latter than beam attenuation. Algal cells both absorb and scatter light and therefore influence Secchi depth and euphotic depth, however, in different fashions.Whenever the lake is clear due to scarce phytoplankton, scattering is small and beam attenuation only exceeds vertical light attenuation by a relatively small factor. As a consequence, the ratio of euphotic depth to Secchi depth is small (1.5–2.5). When the lake is turbid due to high algal density, enhanced scattering from algal cells and detrital particles causes beam attenuation to rise more than vertical light attenuation, thus leading to high ratios of euphotic depth to Secchi depth (3–5). The relatively close relationships between Secchi depth and chlorophyll in Lake Constance are due to (1) high influence of chlorophyll concentration on water transparency, (2) co-variation of phytoplankton and other suspended particles, and (3) limited variation of cellular chlorophyll contents. 相似文献
18.
Yves Claude Guillaume Eric Peyrin Joelle Millet 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1999,735(2):289
A high-performance liquid chromatographic method for the determination of bifonazole in dimethyl sulfoxide solvent was developed to study its penetration into sheephoof. The analytical method was linear over the concentration range studied, i.e., from 0.1 mg/ml to 1 mg/ml. The relative standard deviation was less than 2%. The data obtained showed that complex forming with β-cyclodextrin greatly improved the penetration of bifonazole. 相似文献
19.
This study was conducted to analyse vertical dynamics of phytoplankton distribution in Shira Lake during the summer stratification regime. From late June to September phytoplankton in Shira Lake were stratified with the maximum in the lower part of the thermocline, at a depth of 8–12 m, with a chlorophyll concentration up to 23 g and biomass up to 5 mg l–1. Maxima of chlorophyll and biomass of cyanobacteria and green algae were in different layers. From June to September a major part of chlorophyll a was in green algae, while under ice – in cyanobacteria. The variable fluorescence proves high photosynthetic activity of algae in the depth assemblage. Epifluorescent analysis disclosed that additional light-harvesting pigments were better developed in cells from the depth maximum. The maximum of gross primary production calculated from fluorescence corresponded to the depth maximum of phytoplankton. Primary production over a season was 2.7 gO2 m–2. Formation mechanisms of the depth maximum of phytoplankton are discussed in this paper. 相似文献
20.
Three shallow, lowland lochs (lakes) in the Tayside region of Scotland, experiencing the same climatic regime, were found to be dimictic lakes showing similar clinograde oxygen distributions in summer. Land use differences in their catchments were shown to result in estimated total nutrient surface loadings from 0.3 to 32 g m–2 a–1 phosphorus and from 4 to 240 g m–2 a–1 nitrogen. The major ions in the lochs were calcium and carbonate, but with elevated sulphate levels in all three lochs and an increase in sodium, chloride and sulphate in Forfar loch, which was affected by sewage effluent. Conductivity and total alkalinity showed marked increases with greater intensity of land use, from 64 to 439 µS cm–1 and 0.5–3 meq l–1 Maximum winter loch concentrations of soluble reactive phosphorus ranged from 60 to just under 5 000 mg m–3 and of inorganic nitrogen from 500 to 10500 mg m–3. Maximum chlorophyll a ranged from 20 to 250 mg m–3 and comparisons indicated that above winter levels of 5000 mg m–3 N and 500 mg m–3 P, the nutrient-chlorophyll relationships did not hold. Predictions of nutrient input, from land use categories and soil losses of N and P derived from other north temperate areas, were shown to be comparable with inputs calculated from loch measurements. Models predicting loch concentrations of phosphorus from inputs were comparable with measured concentrations, but predictions of chlorophyll and transparency became less accurate with higher nutrient levels. The lochs were mesotrophic (the Lowes), eutrophic (Balgavies) and hypertrophic (Forfar) under the several classification systems used. The implications of their nutrient status for lake management are discussed and the value of studying this unique lake series in a similar physical environment but with considerable chemical differences is considered. 相似文献