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1.
Analysis of gas exchange in seedlings of Acer saccharum: integration of field and laboratory studies
In the field, photosynthesis of Acer saccharum seedlings was rarely light saturated, even though light saturation occurs at about 100 mol quanta m-2 s-1 photosynthetic photon flux density (PPFD). PPFD during more than 75% of the daylight period was 50 mol m-2 s-1 or less. At these low PPFD's there is a marked interaction of PPFD with the initial slope (CE) of the CO2 response. At PPFD-saturation CE was 0.018 mol m-2 s-1/(l/l). The apparent quantum efficiency (incident PPFD) at saturating CO2 was 0.05–0.08 mol/mol.
and PPFD-saturated CO2 exchange was 6–8 mol m-2 s-1. The ratio of internal CO2 concentration to external (C
i
/C
a
) was 0.7 to 0.8 except during sunflecks when it decreased to 0.5. The decrease in C
i
/C
a
during sunflecks was the result of the slow response of stomates to increased PPFD compared to the response of net photosynthesis. An empirical model, which included the above parameters was used to simulate the measured CO2 exchange rate for portions of two days. Parameter values for the model were determined in experiments separate from the daily time courses being sumulated. Analysis of the field data, partly through the use of simulations, indicate that the elimination of sunflecks would reduce net carbon gain by 5–10%.List of symbols
A
measured photosynthetic rate under any set of conditions (mol m-2 s-1)
-
A
m
(atm)
measured photosynthetic rate at saturating PPFD, 350 l/l CO2 and 21% (v/v) O2 (mol m-2 s-1)
-
C
constant in equation of Smith (1937, 1938)
-
C
a
CO2 concentration in the air (l/l)
-
C
i
CO2 concentration in the intercellular air space (l/l)
-
C
i
/*
C
i
corrected for CO2 compensation point, i.e., C
i
-I
*, (l/l)
- CE
initial slope of the CO2 response of photosynthesis (mol m-2 s-1/(l/l))
- CEM
CE at PPFD saturation
-
E
transpiration rate (mmol m-2 s-1)
-
F
predicted photosynthetic rate (mol m-2 s-1)
-
G
leaf conductance to H2O (mol m-2 s-1)
-
I
photosynthetic photon flux density (mol m-2 s-1)
-
N
number of data points
-
P
m
predicted photosynthetic rate at saturating CO2 and given PPFD (mol m-2 s-1)
-
P
ml
predicted photosynthetic rate at saturating CO2 and PPFD (mol m-2 s-1)
-
R
d
residual respiratory rate (mol m-2 s-1)
-
T
a
air temperature (°C)
-
T
l
leaf temperature (°C)
-
V
reaction velocity in equation of Smith (1937, 1938)
-
V
max
saturated reaction velocity in equation of Smith (1937, 1938)
- VPA
vapor pressure of water in the air (mbar/bar)
- VPD
vapor pressure difference between leaf and air (mbar/bar)
-
X
substrate concentration in equation of Smith (1937, 1938)
-
initial slope of the PPFD response of photosynthesis at saturating CO2 (mol CO2/mol quanta)
- (atm)
initial slope of the PPFD response of photosynthesis at 340 l/l CO2 and 21% (v/v) O2 (mol CO2/mol quanta)
-
I
*
CO2 compensation point after correction for residual respiration (l/l)
-
PPFD compensation point (mol m-2 s-1) 相似文献
2.
We investigated the carbon dynamics and budget in a grassland of Miscanthus sinensis, which is widely distributed in Japan, over a 2-year period (2000–2001). Plant biomass began to increase from May and peaked in September, then decreased towards the end of the growing season (October). Soil respiration rates also exhibited seasonal fluctuations that reflected seasonal changes in soil temperature and root respiration. The contribution of root respiration to total soil respiration was 22–41% in spring and summer, but increased to 52–53% in September. To determine the net ecosystem production (carbon budget), we estimated annual net primary production, soil respiration, and root respiration. Net primary production was 1207 and 1140gCm–2 in 2000 and 2001, respectively. Annual soil respiration was 1387gCm–2 in 2000 and 1408gCm–2 in 2001; root respiration was 649 and 695gCm–2 in 2000 and 2001, respectively. Moreover, some of the carbon fixed as net production (457–459gCm–2) is removed by mowing in autumn in this grassland. Therefore, the annual carbon budget was estimated to be –56gCm–2 in 2000 and – 100gCm–2 in 2001. These results suggest that the Miscanthus sinensis grassland in Japan can act as a source of CO2. 相似文献
3.
D. S. Dimitrov 《The Journal of membrane biology》1984,78(1):53-60
Summary A simple viscoelastic film model is presented, which predicts a breakdown electric potential having a dependence on the electric pulse length which approximates the available experimental data for the electric breakdown of lipid bilayers and cell membranes (summarized in the reviews of U. Zimmermann and J. Vienken, 1982,J. Membrane Biol.
67:165 and U. Zimmermann, 1982,Biochim. Biophys. Acta
694:227). The basic result is a formula for the time of membrane breakdown (up to the formation of pores): =(/C)/(
m
2
0
2
U
4/24Gh
3+T
2/Gh–1), where is a proportionality coefficient approximately equal to ln(h/20),h being the membrane thickness and 0 the amplitude of the initial membrane surface shape fluctuation ( is usually of the order of unity), represents the membrane shear viscosity,G the membranes shear elasticity modules,
m
the membrane relative permittivity, 0=8.85×10–12
Fm,U the electric potential across the membrane, the membrane surface tension andT the membrane tension. This formula predicts a critical potentialU
c
;U
c
=(24Gh
3/
m
2
0
2
)1/4 (for = andT=0). It is proposed that the time course of the electric field-induced membrane breakdown can be divided into three stages: (i) growth of the membrane surface fluctuations, (ii) molecular rearrangements leading to membrane discontinuities, and (iii) expansion of the pores, resulting in the mechanical breakdown of the membrane. 相似文献
4.
The passive membrane properties of the tangential cells in the fly lobula plate (CH, HS, and VS cells, Fig. 1) were determined by combining compartmental modeling and current injection experiments. As a prerequisite, we built a digital base of the cells by 3D-reconstructing individual tangential cells from cobalt-stained material including both CH cells (VCH and DCH cells), all three HS cells (HSN, HSE, and HSS cells) and most members of the VS cell family (Figs. 2, 3). In a first series of experiments, hyperpolarizing and depolarizing currents were injected to determine steady-state I-V curves (Fig. 4). At potentials more negative than resting, a linear relationship holds, whereas at potentials more positive than resting, an outward rectification is observed. Therefore, in all subsequent experiments, when a sinusoidal current of variable frequency was injected, a negative DC current was superimposed to keep the neurons in a hyperpolarized state. The resulting amplitude and phase spectra revealed an average steady-state input resistance of 4 to 5 M and a cut-off frequency between 40 and 80 Hz (Fig. 5). To determine the passive membrane parameters R
m
(specific membrane resistance), R
i
(specific internal resistivity), and C
m
(specific membrane capacitance), the experiments were repeated in computer simulations on compartmental models of the cells (Fig. 6). Good fits between experimental and simulation data were obtained for the following values: R
m
= 2.5 kcm2, R
i
= 60 cm, and C
m
= 1.5 F/cm2 for CH cells; R
m
= 2.0 kcm2, R
i
= 40 cm, and C
m
= 0.9 F/cm2 for HS cells; R
m
= 2.0 kcm2, R
i
= 40 cm, and C
m
= 0.8 F/cm2 for VS cells. An error analysis of the fitting procedure revealed an area of confidence in the R
m
-R
i
plane within which the R
m
-R
i
value pairs are still compatible with the experimental data given the statistical fluctuations inherent in the experiments (Figs. 7, 8). We also investigated whether there exist characteristic differences between different members of the same cell class and how much the exact placement of the electrode (within ±100 m along the axon) influences the result of the simulation (Fig. 9). The membrane parameters were further examined by injection of a hyperpolarizing current pulse (Fig. 10). The resulting compartmental models (Fig. 11) based on the passive membrane parameters determined in this way form the basis of forthcoming studies on dendritic integration and signal propagation in the fly tangential cells (Haag et al., 1997; Haag and Borst, 1997). 相似文献
5.
F. X. Malcata 《Bioprocess and biosystems engineering》1994,11(1):23-28
The balance equations pertaining to the modelling of batch reactors performing an enzyme-catalyzed reaction in the presence of enzyme deactivation are developed. The functional form of the solution for the general situation where both the rate of the enzyme-catalyzed reaction and the rate of enzyme deactivation are dependent on the substrate concentration is obtained, as well as the condition that applies if a maximum conversion of substrate is sought. Finally, two examples of practical interest are explored to emphasize the usefulness of the analysis presented.List of Symbols
C
E mol/m3
concentration of active enzyme
-
C
E,O mol/m3
initial concentration of active enzyme
-
C
S mol/m3
concentration of substrate
-
C
S,O mol/m3
initial concentration of substrate
-
C
S,min mol/m3
minimum value for the concentration of substrate
-
k 1/s
first order rate constant associated with conversion of enzyme/substrate complex into product
-
k
1 1/s
first order deactivation constant of enzyme (or free enzyme)
-
k
2 1/s
first order deactivation constant of enzyme in enzyme/substrate complex form
-
K
m mol/m3
Michaelis-Menten constant
-
p mol/(m3s)
time derivative of C
S
-
q mol/m3
auxiliary variable
-
t s
time elapsed after reactor startup
Greek Symbols
1/s
univariate function expressing the dependence of the rate of enzyme deactivation on C
S
-
mol/m3
dummy variable of integration
-
mol/m3
dummy variable of integration
-
1/s
univariate function expressing the dependence of the rate of substrate depletion on C
S
-
m3/(mol s)
derivative of with respect to C
S 相似文献
6.
M. Diaz A. Haag-Kerwer R. Wingfield E. Ball E. Olivares T. E. E. Grams H. Ziegler U. Lüttge 《Trees - Structure and Function》1996,10(6):351-358
Samples of the Clusiaceae generaClusia, Oedematopus andDystovomita were collected at various sites and different altitudes in northern and south-western Venezuela. Analyses of stable isotopes of carbon and hydrogen and of leaf-nitrogen levels were performed on the dried samples. Correlations among these variables, i.e. carbon isotope discrimination (), hydrogen isotope ratio (D) and N-levels, and with altitude were assessed. In the samples, where values of above 15 indicate predominant performance of C3 photosynthesis, there were slight tendencies of increasing , D and N-levels with increasing altitude and of increasing with increasing N. Although these correlations taken separately were not statistically significant, they support each other and indicate increasing transpiration and increased leaf-nutrient supply at increasing altitude. Performance of crassulacean acid metabolism (CAM) in species ofClusia appears to be restricted to altitudes below 1500 m a.s.l. There was a significant negative correlation of with altitude in the samples, where values of below 10 indicated predominant performance of CAM. This suggests that phases II and IV of CAM are progressively suppressed towards the upper altitudinal limit of CAM inClusia in northern Venezuela. It is concluded that among the large number of environmental factors and combinations thereof, which determine the expression of CAM inClusia and trigger C3-CAM transitions in C3/CAM intermediate species, low availability of water is the most important. 相似文献
7.
The uptake of the aminoacid biosynthesis inhibitor, used as the broad-spectrum herbicide ingredient, glyphosate (N-[phosphonomethyl]-glycine) was investigated in E. coli as a model to study mechanisms of cell resistance to antimetabolites as drugs and pesticides. Unlike the glyphosate-degrading Arthrobacter sp. strain for which the first successful measurement of glyphosate uptake and its inhibition by orthophosphate was reported [15], E. coli K-12 cannot take up this inhibitor either in the presence of orthophosphate, or after a prolonged starvation for it. However, cells made competent after an overnight cold CaCl2 exposure followed by dimethyl sulfoxide (DMSO) treatment could take up this compound (K
m for glyphosate uptake, 274 M). Neither amino acids, belonging to a single transport system, nor orthophosphate gave essential inhibition of glyphosate uptake by these cells. 相似文献
8.
Nichola J. K. Hole Edmundo Lamoyi Masanori Komatsu Nagaradona Harindranath Glendowlyn O. Young-Cooper Rose G. Mage 《Immunogenetics》1988,28(2):99-107
In order to investigate linkage, we used serum allotypes of the two rabbit C
isotypes and restriction fragment length polymorphisms (RFLPs) of the genes for V
, C
, and T-cell receptor C
. The inheritance of these genetic markers was studied through backcross and F2 matings. Southern analysis and hybridization of genomic DNA with a C probe detected a 5 kb Pst I fragment linked to expression of the K2bas1 allotype and the presence of the 1b
bas gene and a 6.6 kb Pst I fragment linked to the expression of the K1b9 allotype, the presence of the 2
bas2 gene and lack of expression of the K2bas1 allotype. A V probe detected a 1.3 kb Eco RI fragment linked to the presence of the 1b
bas gene and expression of the K2bas1 allotype. In contrast, the 9 or 14 kb Eco RI RFLP (C
a or C
b) detected with a Tcr
chain probe segregated independently from C allotypes and RFLPs. It has previously been found that C and C
are also unlinked in man, whereas in the mouse they are linked at a distance of 8 centimorgans. 相似文献
9.
Evidence for two modes of Ca2+ entry following muscarinic stimulation of a human salivary epithelial cell line 总被引:1,自引:0,他引:1
Xinjun He Xiaozai Wu R. James Turner Bruce J. Baum 《The Journal of membrane biology》1990,115(2):159-166
Summary We have investigated muscarinic receptor-operated Ca2+ mobilization in a salivary epithelial cell line, HSG-PA, using an experimental approach which allows independent evaluation of intracellular Ca2+ release and extracellular Ca2+ entry. The carbachol (Cch) dose response of intracellular Ca2+ release indicates the involvement of a single, relatively low-affinity, muscarinic receptor site (K
0.510 or 30 m, depending on the method for [Ca2+]
i
determination). However, similar data for Ca2+ entry indicate the involvement of two Cch sites, one consistent with that associated with Ca2+ release and a second higher affinity site withK
0.52.5 m. In addition, the Ca2+ entry response observed at lower concentrations of Cch (2.5 m) was completely inhibited by membrane depolarization induced with high K+ (>55mm) or gramicidin D (1 m), while membrane depolarization had little or no effect on Ca2+ entry induced by 100 m Cch. Another muscarinic agonist, oxotremorine-M (100 m; Oxo-M), like Cch, also induced an increase in the [Ca2+]
i
of HSG-PA cells (from 72±2 to 104±5nm). This response was profoundly blocked (75%) by the inorganic Ca2+ channel blocker La3+ (25–50 m) suggesting that Oxo-M primarily mobilizes Ca2+ in these cells by increasing Ca2+ entry. Organic Ca2+ channel blockers (verapamil or diltiazem at 10 m, nifedipine at 1 m), had no effect on this response. The Oxo-M induced Ca2+ mobilization response, like that observed at lower doses of Cch, was markedly inhibited (70–90%) by membrane depolarization (high K+ or gramicidin D). At 100 m Cch the formation of inositol trisphosphate (IP3) was increased 55% above basal levels. A low concentration of carbachol (1 m) elicited a smaller change in IP3 formation (25%), similar to that seen with 100 m Oxo-M (20%). Taken together, these results suggest that there are two modes of muscarinic receptor-induced Ca2+ entry in HSG-PA cells. One is associated with IP3 formation and intracellular Ca2+ release and is independent of membrane potential; the other is less dependent on IP3 formation and intracellular Ca2+ release and is modulated by membrane potential. This latter pathway may exhibit voltage-dependent gating. 相似文献
10.
Gating of retinal rod cation channel by different nucleotides: Comparative study of unitary currents
Summary Single channels are observed after incorporation of native vesicles from bovine rod outer segment membranes into planar lipid bilayers. The activity of a single channel in the presence of cGMP is compared to that induced by the analog 8-bromo-cGMP and by cAMP. At +80 mV, K
0.5 is about 3 m for 8Br-cGMP, 18 m for cGMP and 740 m for cAMP. In cAMP, the amplitude of the current is smaller than in cGMP or 8Br-cGMP and depends on the filter cut-off frequency. The open/closed transition rates of the channel are slightly slower with 8Br-cGMP than with cGMP while they are 5 to 10 times faster with cAMP. Addition of Ni2+ ions to either cGMP or cAMP increases the open probability: the open/closed transition rates and amplitude of the current in cAMP are then comparable to those in cGMP. A dual effect of the addition of cAMP on the cGMPor 8Br-cGMP dependent activity previously reported (Furman, R.E., Tanaka, J.C. 1989. Biochemistry
28:2785–2788) is observed with a single channel: addition of subthreshold cAMP concentrations to cGMP (or to 8Br-cGMP) markedly increases P
o; addition of cAMP concentrations higher than about 70 m progressively accelerates the kinetics and reduces the amplitude to values observed in cAMP alone. The results are discussed in relation with the model previously proposed to account for the existence of four current levels (Ildefonse, M., Bennett, N. 1991. J. Membrane Biol.
123:133–147). 相似文献
11.
The cellular basis of internode elongation was studied in intact deep-water rice plants (Oryza sativa L. cv. Habiganj Aman II) and in isolated stem sections. In intact plants, growth was stimulated by submergence in water and by ethylene treatment. In isolated sections, growth was enhanced by submergence, by ethylene, and by exposure of the tissue to an atmosphere of 3% O2, 91% N2 and 6% CO2 or 3% O2, 91% N2, 6% CO2 and 1 l l-1 C2H4 (by vol.). Under all these conditions, growth was localized in the intercalary meristem at the bases of the internodes. Autoradiography of [3H]thymidine-labeled tissue showed activation of cell division and longitudinal expansion of the intercalary meristem. Increased production of new cells and their subsequent elongation thus form the basis for the growth response to submergence and ethylene treatment in deep-water rice plants. 相似文献
12.
Summary Fathead minnows, Pimephales promelas, and yellow perch, Perca flavescens, were transferred from moderately soft Lake Superior water (hardness 45mg/l as CaCO3) to very soft diluted Lake Superior water (hardness 4.5mg/l). Sulfuric acid was added in some treatments by means of a multichannel diluter. In very soft water, chloride cells proliferated in the gills, especially in the epithelium of the secondary lamellae. When exposed to acid, chloride cells were damaged and less abundant in the secondary lamellae, and blood osmolality was reduced at pH 5.0 (x = 188 mOsm/kg, 9 days exposure; normal 280 mOsm/kg) for the minnows and pH 4.1 (x = 218 mOsm/kg, 58 days exposure; normal 329 mOsm/kg) for the perch. Certain chloride cells which form gland-like clusters in the primary lamellae of perch gills showed little damage even at pH 4.1. The present study supports the view that chloride cells proliferate in very soft fresh water to help maintain ionic balances, and that damage to these cells in acidified soft water may be related to diminished ionoregulatory capacity. The greater acid tolerance of chloride cells of, and the higher blood osmolality maintained by, perch could help to explain the greater tolerance of this species to low pH. In some cases, a species' ability to acclimate to very soft water and acidified soft water may depend upon the number, distribution, and physiology of its chloride cells. 相似文献
13.
Continuous penicillin G hydrolysis in an electro-membrane reactor with immobilized penicillin G acylase 总被引:1,自引:0,他引:1
Penicillin G (2%, w/v in phosphate buffer, pH 8) was hydrolysed in a flow-through, miniature electro-membrane reactor with the penicillin G acylase immobilized in 5% (w/v) polyacrylamide (diam. 10 mm, thickness 2.6 mm, enzyme activity 24 U ml–1). The conversion of penicillin G increased from 0.15 to almost 0.5 when the electric current applied to the reactor was changed from –600 to +600 A/m2 with a substrate residency of 1 h.
Symbols and abbreviations
c
j
p & concentration of component j in product stream (M) c
j
s & concentration of component j in substrate stream (M) c
s
o & substrate concentration at reactor inlet (M) C
j
p=c
j
p/c
S
0 & scaled concentration of component j in product stream C
j
s=c
j
s/c
S
0 & scaled concentration of component j in substrate stream i & electric current density (A/m2) j & reaction component, j P, Q or S P & main reaction product (6-aminopenicillanic acid) PGA & penicillin G acylase Q & side reaction product (phenylacetic acid) S & substrate (penicillin G) Y
s=C
P
s+C
P
p & substrate conversion & mean residence time of substrate and product streams in reactor (h) =C
Q
s+C
Q
p+C
S
s+C
S
s & check-sum of scaled concentrations =C
P
p/(C
P
s+C
P
p) & separation factor of 6-aminopenicillanic acid (0 1) 相似文献
14.
H. Beving L. E. G. Eriksson C. L. Davey D. B. Kell 《European biophysics journal : EBJ》1994,23(3):207-215
The dielectric properties of human erythrocytes (red blood cells) suspended in whole blood and in isotonic media at various volume fractions (haematocrits) have been studied in the frequency range 0.2–10 MHz, in which the so-called-dispersion due to the Maxwell-Wagner effect is known to occur. The capacitance and conductance at 25 °C were measured by an instrument interfaced to a computer. The rectangular sample cavity (1 ml volume) contained four pure gold electrode pins, and the sample could be circulated by a roller pump. The frequency-dependence of the permittivity and conductivity were fitted by non-linear least squares regression. Corrections were applied for non-linearity in the dielectric increment at high haematocrit, and for electrode polarisation when diluting the blood in saline. Data were interpreted in terms of a simple equivalent resistor-capacitor circuit. From the measured haematological values the specific membrane capacitance (Cm) and the conductivities internal and external to the cells (i and o respectively) were estimated. The conductivities behaved in a predictable manner with a mean of 0.458 S · m–1 (s.d. ± 0.044) for i, whereas the value of Cm (and indeed the actual capacitance of the suspension) was dependent on the amount of plasma present. Hence, in stationary normal (anticoagulated) whole blood samples, Cm was as high as 2.98 F · cm–2 (s.d. ± 0.40), in contrast to about 0.9 F · cm–2 in blood diluted more than two-fold (to less than 20% hct) in isotonic media. The high value remained when the diluent was plasma. The Cm value returned to a high value when washed erythrocytes were reconstituted with plasma, provided that this was present at above a critical or threshold concentration of about 30 vol % in the medium, irrespective of the haematocrit in the range studied (15–44%). The Cm remained low in serum. When added to washed cells in saline, purified fibrinogen had no effect. However, high Cm values were obtained by fibrinogen supplementation to serum and diluted plasma. Applying moderate flow to whole blood approximately halved its high Cm value in an exponential manner with flow rate, whilst the Cm of washed cells (31–67% hct) slightly increased, and converged to the value for whole blood under flow. We interpret the highapparent Cm value in stationary samples to be a result of rapid cell aggregation in the presence of plasma, where rouleaux formation takes place before visible sedimentation sets in. 相似文献
15.
Hydrodynamic characteristics of two-phase inverse fluidized bed 总被引:1,自引:0,他引:1
Hydrodynamic characteristics of a new mode of liquid-solid fluidization, termed as inverse fluidization in which low density floating particles are fluidized with downward flow of liquid, are experimentally investigated. The experiments are carried out with low density particles (<534 kg/m3) which allow high liquid throughputs in the system. During the operation, three regimes, namely, packed, semi-fluidization and fully fluidization are encountered. Empirical correlations are proposed to predict the pressure drop in each regime. A computational procedure is developed to simulate the variation of pressure drop with liquid velocity.List of Symbols
Ar
modified Archimedes number, d
p
3
(–
s)g/2
-
d
p
particle diameter, mm
-
f
friction factor (eq. 2)
-
g
acceleration due to gravity, m/s2
- H
total bed height, m
-
H
c
height of the column, m
- Hf
height of fluidized bed, m
- H0
height of initial bed, m
- Hp
height of the packed bed, m
- (p)
pressure drop across the bed, N/m2
- (p)
f
pressure drop across fluidized bed section, N/m2
- (p)
p
pressure drop across the packed bed section, N/m2
- (p)
sf
total pressure drop in semifluidization regime, N/m2
- Re
Reynolds number, d
pU
1/
- Rem
modified Reynolds number, d
pU
1/(1–
p)
-
U
1
superficial liquid velocity, m/s
- Umf
minimum fluidization velocity, m/s
- Uosf
onset fluidization velocity, m/s
Greek Letters
f
voidage of fluidized bed
- p
voidage of packed bed
-
liquid viscosity, kg/ms
-
liquid density, kg/m3
-
s
particle density, kg/m3 相似文献
16.
Mikkola R Andersson MA Grigoriev P Teplova VV Saris NE Rainey FA Salkinoja-Salonen MS 《Archives of microbiology》2004,181(4):314-323
Fungicidic Bacillus amyloliquefaciens strains isolated from the indoor environment of moisture-damaged buildings contained heat-stable, methanol-soluble substances that inhibited motility of boar spermatozoa within 15 min of exposure and killed feline lung cells in high dilution in 1 day. Boar sperm cells lost motility, cellular ATP, and NADH upon contact to the bacterial extract (0.2 g dry wt/ml). Two bioactive substances were purified from biomass of the fungicidal isolates. One partially characterized substance, 1,197 Da, was moderately hydrophobic and contained leucine, proline, serine, aspartic acid, glutamic acid and tyrosine, in addition to chromophore(s) absorbing at 365 nm. In boar sperm and human neural cells (Paju), the compound depolarized the transmembrane potentials of mitochondria (m) and the plasma membrane (p) after a 20-min exposure and formed cation-selective channels in lipid membranes, with a selectivity K+:Na+:Ca2+ of 26:15:3.5. The other substance was identified as a plasma-membrane-damaging lipopeptide surfactin. Plate-grown biomass of indoor Bacillus amyloliquefaciens contained ca. 7% of dry weight of the two substances, 1,197 Da and surfactin, in a ratio of 1:6 (w:w). The in vitro observed simultaneous collapse of both cytosolic and mitochondrial ATP in the affected mammalian cell, induced by the 1,197-Da cation channel, suggests potential health risks for occupants of buildings contaminated with such toxins.Abbreviations RP-HPLC Reversed-phase high-performance liquid chromatography - BLM Black lipid membrane - DAD Diode-array detector - m Mitochondrial membrane potential - p Plasma membrane potential - JC-1 5,5,6,6-Tetrachloro-1,1,3,3-tetraethylbenz-imidazolo carbocyanine iodide - AM Calcein acetoxymethyl ester - PI Propidium iodide - MALDI-TOF-MS Matrix-assisted laser desorption ionization time-of-flight mass spectrometry - ESI-IT-MS Electrospray ionization ion trap mass spectrometry - EC50 Endpoint concentration which caused 50% change in the viability parameters - FCCP Carbonyl cyanide 4-trifluoromethoxyphenylhydrazone 相似文献
17.
Interrelationships Between Nitrogen Supply and Photosynthetic Parameters in Vicia faba L. 总被引:2,自引:2,他引:0
We determined for Vicia faba L the influence of nitrogen uptake and accumulation on the values of photon saturated net photosynthetic rate (P
Nmax), quantum yield efficiency (), intercellular CO2 concentration (C
i), and carboxylation efficiency (C
e). As leaf nitrogen content (NL) increased, the converged onto a maximum asymptotic value of 0.0664±0.0049 mol(CO2) mol(quantum)–1. Also, as NL increased the C
i value fell to an asymptotic minimum of 115.80±1.59 mol mol–1, and C
e converged onto a maximum asymptotic value of 1.645±0.054 mol(CO2) m–2 s–1 Pa–1 and declined to zero at a NL-intercept equal to 0.596±0.096 g(N) m–2. fell to zero for an NL-intercept of 0.660±0.052 g(N) m–2. As NL increased, the value of P
Nmax converged onto a maximum asymptotic value of 33.400±2.563 mol(CO2) m–2 s–1. P
N fell to zero for an NL-intercept of 0.710±0.035 g(N) m–2. Under variable daily meteorological conditions the values for NL, specific leaf area (L), root mass fraction (Rf), P
Nmax, and remained constant for a given N supply. A monotonic decline in the steady-state value of Rf occurred with increasing N supply. L increased with increasing N supply or with increasing NL. 相似文献
18.
In this paper we use a dynamical systems approach to prove the existence of a unique critical value c
* of the speed c for which the degenerate density-dependent diffusion equation u
ct
= [D(u)u
x
]
x
+ g(u) has: 1. no travelling wave solutions for 0 < c < c
*, 2. a travelling wave solution u(x, t) = (x - c
*
t) of sharp type satisfying (– ) = 1, () = 0 *; '(*–) = – c
*/D'(0), '(*+) = 0 and 3. a continuum of travelling wave solutions of monotone decreasing front type for each c > c
*. These fronts satisfy the boundary conditions (– ) = 1, '(– ) = (+ ) = '(+ ) = 0. We illustrate our analytical results with some numerical solutions. 相似文献
19.
Verification studies of a simplified model for the removal of dichloromethane from waste gases using a biological trickling filter 总被引:5,自引:0,他引:5
The removal of dichloromethane from waste gases in a biological trickling filter was studied experimentally as well as theoretically within the concentration range of 0–10,000 ppm. A stable dichloromethane elimination performance was achieved during two years of operation, while the start-up of the system only amounted to several weeks at constant inlet concentrations. The trickling filter system was operated co-currently as well as counter-currently.However, experimental and theoretical results revealed that the relative flow direction of the mobile phases did not significantly affect the elimination performance. Moreover, it was found that the gas-liquid mass-transfer resistance in the trickling filter bed applied was negligible, which leaves the biological process inside the biofilm to be the rate limiting step.A simplified model was developed, the Uniform-Concentration-Model, which showed to predict the filter performance close to the numerical solutions of the model equations. This model gives an analytical expression for the degree of conversion and can thus be easily applied in practice.The dichloromethane eliminating performance of the trickling filter described in this paper, is reflected by a maximum dichloromethane elimination capacity EC
max=157 g/(m3 · h) and a critical liquid concentration C
lcr=45 g/m3 at a superficial liquid velocity of 3.6 m/h, inpendent of the gas velocity and temperature.List of Symbols
a
s
m2/m3
specific area
-
a
w
m2/m3
specific wetted area
-
A m2
cross-sectional area
-
C
g
g/m3
gas phase concentration
-
C
go
g/m3
inlet gas phase concentration
-
C
gocr
g/m3
critical gas phase concentration
-
C
g
*
Cg/Cgo dimensionless gas concentration
-
C
l
g/m3
liquid concentration
-
C
lcr
g/m3
critical liquid concentration
-
C
lcr
*
mClcr/Cgo dimensionless critical concentration
-
c
li
g/m3
substrate concentration at liquid-biofilm interface
-
C
l
*
mCl/Cgo dimensionless liquid concentration
-
C
o
g/m3
oxygen concentration inside the biofilm
-
C
oi
g/m3
oxygen concentration at liquid-biofilm interface
- Cs g/m3
substrate concentration inside the biofilm
-
C
si
g/m3
substrate concentration at liquid-biofilm interface
-
D
eff
m2/h
effective diffusion coefficient in the biofilm
-
D
o
m2/h
effective diffusion coefficient for oxygen in the biolayer
-
E
mug/ul extraction factor
-
E
act kJ/mol
activation energy for the biological reaction
-
EC g/(m3· h)
K
o
a
w
: elimination capacity, or the amount of substrate degraded per unit of reactor volume and time
-
EC
max g/(m3 · h)
K
o
aw: maximum elimination capacity
-
f
degree of conversion
-
h m
coordinate in height
-
H m
height of the packed bed
-
K
0 g/(m3 · h)
maxXb/Y zeroth order reaction defined per unit of biofilm volume
-
k
og
m/h
overall gas phase mass transfer coefficient
-
K
*
dimensionless constant given by Eq. (A.5)
-
K
l
*
dimensionless constant given by Eq. (A.6)
-
K
2
*
dimensionless constant given by Eq. (A.6)
-
m
C
g
/Cl gas liquid distribution coefficient
-
N g/(m2 · h)
liquid-biofilm interfacial flux of substrate
-
N
og
kogawH/ug number of gas phase transfer units
-
N
r
ko aw H/ug Cgo number of reaction units
-
OL g/(m3· h)
u
g
C
go
/H organic load
-
r
s
g/(m3 ·h)
zeroth order substrate degradation rate given by Eq. (1)
-
R
s
g/(g TSS ·h)
specific activity
-
T K
absolute temperature
-
u
g
m/h
superficial gas velocity
-
u
t
m/h
superficial liquid velocity
-
X
b
g TSS/m3
biomass concentration inside biofilm
-
X
s
g TSS/m3
liquid suspended biomass concentration
-
x m
coordinate inside the biofilm
-
Y g TSS/(gDCM)
yield coefficient
Greek Symbols
dimensionless parameter given by Eq. (2)
-
m
averaged biofilm thickness
-
biofilm effectiveness factor given by Eqs. (7a)–(7c)
-
m
penetration depth of substrate into the biofilm
-
max
d–1
microbiological maximum growth rate
-
v
o
stoichiometric utilization coefficient for oxygen
-
v
s
stoichiometric utilization coefficient for substrate
-
dimensionless height in the filter bed
-
h
H/u
g
superficial gas phase contact time
-
o
(K
0
/DC
ii
)1/2
-
o
C
o
/C
oi
dimensionless oxygen concentration inside the biofilm
-
s
C
s
/C
si
dimensionless substrate concentration inside the biofilm
Experimental results, verifying the model presented will be discussed Part II (to be published in Vol. 6, No. 4) 相似文献
20.
Zyakun A. M. Kosheleva I. A. Zakharchenko V. N. Kudryavtseva A. I. Peshenko V. A. Filonov A. E. Boronin A. M. 《Microbiology》2003,72(5):592-596
The study deals with a comparative analysis of the relative abundances of the carbon isotopes 12C and 13C in the metabolites and biomass of the Burkholderia sp. BS3702 and Pseudomonas putida BS202-p strains capable of utilizing aliphatic (n-hexadecane) and aromatic (naphthalene) hydrocarbons as sources of carbon and energy. The isotope compositions of the carbon dioxide, biomass, and exometabolites produced during the growth of Burkholderia sp. BS3702 on n-hexadecane (13C = –44.6 ± 0.2) were characterized by the values of 13CCO
2 = –50.2 ± 0.4, 13Cbiom = –46.6 ± 0.4, and 13Cexo = –41.5 ± 0.4, respectively. The isotope compositions of the carbon dioxide, biomass, and exometabolites produced during the growth of the same bacterial strain on naphthalene (13C = –21 ± 0.4) were characterized by the isotope effects 13CCO
2 = –24.1 ± 0.4, 13Cbiom = –19.2 ± 0.4, and 13Cexo = –19.1 ± 0.4, respectively. The possibility of using the isotope composition of metabolic carbon dioxide for the rapid monitoring of the microbial degradation of petroleum hydrocarbons in the environment is discussed. 相似文献