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1.
Biotransformation of cephalosporin C (CPS-C) to 7-aminocephalosporanic acid (7-ACA) was carried out with coimmobilized permeabilized cells of Trigonopsis variabilis and Pseudomonas species entrapped in Ca-pectate gel beads. Good aeration and stirring during the process was assured. The analysis of this complicated biochemical process in a heterogeneous system was based on the identification of individual effects (internal diffusion, reaction) running simultaneously. A spectrophotometric method was proposed for the determination of 7-(-ketoadipyl amido) cephalosporanic acid (CO-GL-7-ACA) and 7-ACA. The reaction-diffusion model containing dimensionless partial differential equations was solved by using the orthogonal collocation method. A good agreement between experimental values and values predicted by the mathematical model was obtained. Numerical simulations were performed on the basis of following the two assumptions:- several times higher activity of both cells,- hydrogen peroxide was continuously supplied in the bioreactor.List of Symbols
A m2
surface of the bead
-
c
i
mol/dm3
concentration of component in the bead and/or in the solution
-
c
i0
mol/dm3
initial concentration of component in the solution
-
c
l0
mol/dm3
initial concentration of CPS-C in the solution
-
C
jl
orthogonal collocation weights of the first derivation
-
D
ei
m2/s
effective diffusion coefficient of the components
-
D
jl
orthogonal collocation weights of the second derivation
-
k
5 dm3/(mol · s)
kinetic parameter of non-enzyme reaction
-
K
inh
mol/dm3
inhibition parameter for the first enzyme reaction
-
K
i
dimensionless Michaelis constant for the first and second enzyme reaction, defined in Eq. (7)
-
K
l
dimensionless inhibition parameter for the first enzyme reaction, defined in Eq. (7)
-
K
mi
mol/dm3
Michaelis constant for the first and second enzyme reaction
-
n
number of beads
-
P(
i
)
symbol of dimensionless reaction rate, defined in Eq. (13)
-
r m
radial coordinate inside the bead
-
R m
radius of the bead
-
R(c
i
) mol/(dm3 · s)
symbol for reaction rate, defined in Eq. (6)
-
t s
time
-
V
max mol/(dm3 · s)
max. reaction rate for the first and second enzyme reaction
-
V
L
dm3
volume of solution excluding the space occupied by beads
-
voidage in batch bioreactor
-
P
porosity of the bead
- i
dimensionless effective diffusion coefficient of the components, defined in Eq. (7)
-
dimensionless time, defined in Eq. (7)
-
mi
Thiele modulus, defined in Eq. (7)
-
i
dimensionless concentration, defined in Eq. (7)
-
dimensionless radial position inside the bead, defined in Eq. (7)
-
l0
initial dimension concentration of CPS-C, defined in Eq. (9), (10)
-
i0
initial dimension concentration of component, defined in Eq. (9), (10)
The authors wish to thank Dr. P. Gemeiner of Slovak Academy of Sciences for rendering of pectate gel. This work is supported by Ministry of Education (Grant No. 1/990 935/93). 相似文献
2.
The stability and, consequently, the lifetime of immobilized enzymes (IME) are important factors in practical applications of IME, especially so far as design and operation of the enzyme reactors are concerned. In this paper a model is presented which describes the effect of intraparticle diffusion on time stability behaviour of IME, and which has been verified experimentally by the two-substrate enzymic reaction. As a model reaction the ethanol oxidation catalysed by immobilized yeast alcohol dehydrogenase was chosen. The reaction was performed in the batch-recycle reactor at 303 K and pH-value 8.9, under the conditions of high ethanol concentration and low coenzyme (NAD+) concentration, so that NAD+ was the limiting substrate. The values of the apparent and intrinsic deactivation constant as well as the apparent relative lifetime of the enzyme were calculated.The results show that the diffusional resistance influences the time stability of the IME catalyst and that IME appears to be more stabilized under the larger diffusion resistance.List of Symbols
C
A, CB, CE mol · m–3
concentration of coenzyme NAD+, ethanol and enzyme, respectively
-
C
p mol · m3
concentration of reaction product NADH
-
d
p mm
particle diameter
-
D
eff m2 · s–1
effective volume diffusivity of NAD+ within porous matrix
-
k
d s–1
intrinsic deactivation constant
-
K
A, KA, KB mol · m–3
kinetic constant defined by Eq. (1)
-
K
A
x
mol · m–3
kinetic constant defined by Eq. (5)
-
r
A mol · m–3 · s–1
intrinsic reaction rate
-
R m
particle radius
-
R
v mol · m–3 · s–1
observed reaction rate per unit volume of immobilized enzyme
-
t
E s
enzyme deactivation time
-
t
r s
reaction time
-
V mol · m–3 · s–1
maximum reaction rate in Eq. (1)
-
V
x mol · m–3 · s–1
parameter defined by Eq. (4)
-
V
f m3
total volume of fluid in reactor
-
w
s kg
mass of immobilized enzyme bed
-
factor defined by Eqs. (19) and (20)
-
kg · m–3
density of immobilized enzyme bed
-
unstableness factor
-
effectiveness factor
-
Thiele modulus
-
relative half-lifetime of immobilized enzyme
Index
o
values obtained with fresh immobilized enzyme 相似文献
3.
A pilot scale airlift reactor with multiple net draft tubes was developed to improve oxygen transfer in the reactor. The reactor was 0.29 m in diameter and 2 m height. A steadystate sulfite oxidation method was applied to determine an overall volumetric mass transfer coefficient. Oxygen transfer of the proposed airlift reactor can be 60–100% higher than that of bubble columns under the same operating conditions.List of Symbols
C
* mol·dm–3
saturated concentration of dissolved oxygen
-
C
L
mol·dm–3
bulk concentration of dissolved oxygen
-
G mol/min
nitrogen flow rate
-
k
L
a hr–1
the volumetric gas-liquid mass transfer coefficient
-
Mo
2
g/mol
molecular weight of oxygen
- OTR g/min
the oxygen transfer rate
-
U
g
cm/s
superficial air velocity
-
V
L
dm3
volume of the liquid phase
- in
oxygen mole ratio in the inlet gas
- out
oxygen mole ratio in the outlet gas 相似文献
4.
Measurement of the light response of photosynthetic CO2 uptake is often used as an implement in ecophysiological studies. A method is described to calculate photosynthetic parameters, such as the maximum rate of whole electron transport and dissimilative respiration in the light, from the light response of CO2 uptake. Examples of the light-response curves of flag leaves and ears of wheat (Triticum aestivum cv. ARKAS) are shown.Abbreviations and symbols A
net photosynthesis rate
-
D
1
rate of dissimilative respiration occurring in the light
-
f
loss factor
-
I
incident PPFD
-
I
effective absorbed PPFD
-
J
rate of whole electron transport
-
J
m
maximum rate of whole electron transport
-
p
c
intercellular CO2 partial pressure
- PPFD
photosynthetic photon flux density
-
q
effectivity factor for the use of light (electrons/quanta)
-
absorption coefficient
-
I
*
CO2 compensation point in the absence of dissimilative respiration (bar)
-
II
conversion factor for calculation of CO2 uptake from the rate of whole electron transport
-
convexity factor
Gas-exchange rates relate to the projective area and are given in mol·m-2·s-1. Electron-transport rates are given in mol electrons·m-2·s-1; PPFD is given in mol quanta·m-2·s-1. 相似文献
5.
The effectiveness of using micro-gel bead-immobilized cells for aerobic processes was investigated. Glutamine production by Corynebacterium glutamicum, 9703-T, cells was used as an example. The cells were immobilized in Sr-alginate micro-gel beads 500 m in diameter and used for fermentation processes in a stirred tank reactor with a modified impeller at 400 min–1. Continuous production of glutamine was carried out for more than 220 h in this reactor and no gel breakage was observed. As a result of the high oxygen transfer capacity of this system, the glutamine yield from glucose was more than three times higher, while the organic acid accumulation was more than 24 times lower than those obtained with 3.0 mm-gel bead-immobilized cells in an airlift fermentor under similar experimental conditions. During the continuous fermentations there was evolution and proliferation of non-glutamine producing strains which led to a gradual decrease in the productivity of the systems. Although a modified production medium which suppresses cell growth during the production phase was effective in maintaining the productivity, the stability of the whole system was shortened due to high cell deactivation rate in such a medium.List of Symbols
C kg/m3
glutamine concentration
-
C
A
mol/m
3
local oxygen concentration inside the gel beads
-
C
AS
mol/m
3
oxygen concentration at the surface of the gel beads
-
De m2/h
effective diffusion coefficient of oxygen in the gel bead
-
DO mol/m3
dissolved oxygen concentration
-
F dm3/h
medium flow rate
-
K h–1
glutamine decomposition rate constant
-
Km mol/m3
Michaelis Menten constant
-
QO
2max
mol/(kg · h)
maximum specific respiration rate
-
R m
radius of the gel beads
-
r m
radial distance
-
t h
time
-
V
C
dm
3
volume of the gel beads
-
V
L
dm
3
liquid volume in the reactor
-
Vm mol/(m3 · h)
maximum respiration rate
-
X kg/m3
cell concentration
-
x
r/R
-
y
C
A
/CAS
- h–1
cell deactivation rate constant
-
Thiele modulus defined by R(Vm/De Km)
1/2
-
C
AS
/Km
-
C
kg/(m3-gel · h)
specific glutamine formation rate
-
c
dm3-gel/dm3
V
C
/V
L
相似文献
6.
Desana Li >sková José Ruiz Ordóñez Alexander Lux Alfredo Piñeyro López 《Plant Cell, Tissue and Organ Culture》1994,36(3):339-343
Isolated embryos ofKarwinskia humboldtiana were cultured in vitro. The growth of embryos and development to plantlets on woody plant medium supplemented with indole-3-acetic acid 6.10-2 mol l–1, gibberellic acid (GA3) 3.10-2 mol l–1, and 6-benzylaminopurine (BA) 2 mol l–1 was obtained. Multiplication of shoots and rooting of excised shoots has been achieved. Callus formation on modified Murashige-Skoog medium supplemented with 1-naphthaleneacetic acid 10 mol l–1, GA3 14 mol l–1, and kinetin 5 mol l–1 on hypocotyls, or on root cultures on medium supplemented with 2.4-dichlorophenoxyacetic acid 10 mol l–1 and BA 10 mol l–1 was induced.Abbreviations BA
6-benzylaminopurine
- 2,4-d
2,4-dichlorophenoxyacetic acid
- GA3
gibberellic acid
- IAA
indole-3-acetic acid
- NAA
1-naphthaleneacetic acid
- TEM
transmission electron microscopy 相似文献
7.
In C4 grasses belonging to the NADP-malic enzyme-type subgroup, malate is considered to be the predominant C4 acid metabolized during C4 photosynthesis, and the bundle sheath cell chloroplasts contain very little photosystem-II (PSII) activity. The present studies showed that Flaveria bidentis (L.), an NADP-malic enzyme-type C4 dicotyledon, had substantial PSII activity in bundle sheath cells and that malate and aspartate apparently contributed about equally to the transfer of CO2 to bundle sheath cells. Preparations of bundle sheath cells and chloroplasts isolated from these cells evolved O2 at rates between 1.5 and 2 mol · min–1 · mg–1 chlorophyll (Chl) in the light in response to adding either 3-phosphoglycerate plus HCO
3
–
or aspartate plus 2-oxoglutarate. Rates of more than 2 mol O2 · min–1 · mg–1 Chl were recorded for cells provided with both sets of these substrates. With bundle sheath cell preparations the maximum rates of light-dependent CO2 fixation and malate decarboxylation to pyruvate recorded were about 1.7 mol · min–1 · mg–1 Chl. Compared with NADP-malic enzyme-type grass species, F. bidentis bundle sheath cells contained much higher activities of NADP-malate dehydrogenase and of aspartate and alanine aminotransferases. Time-course and pulse-chase studies following the kinetics of radiolabelling of the C-4 carboxyl of C4 acids from 14CO2 indicated that the photosynthetically active pool of malate was about twice the size of the aspartate pool. However, there was strong evidence for a rapid flux of carbon through both these pools. Possible routes of aspartate metabolism and the relationship between this metabolism and PSII activity in bundle sheath cells are considered.Abbreviations DHAP
dihydroxyacetone phosphate
- NADP-ME(-type)
NADP-malic enzyme (type)
- NADP-MDH
NADP-malate dehydrogenase
- OAA
oxaloacetic acid
- 2-OG
2-oxoglutarate
- PEP
phosphoenolpyruvate
- PGA
3-phosphoglycerate
- Pi
orthophosphate
- Ru5P
ribulose 5-phosphate 相似文献
8.
Summary In this paper the behaviour of the down-flow stationary fixed film digesters is studied at laboratory and bench scale. Several organic loading rates are applied to the reactors in order to examine the support surface behaviour. Specific support surfaces of about 50 m2/m3 void volume seems to be optimal. A set of experiments carried out in a continuous stirred reactor is used to fit the kinetic constants of the Chen and Hashimoto's model. The model is then used to assess its applicability to the DSFF digesters. The results show that its application, is possible as a first approximation.Nomenclature B0
Ultimate methane yield (m3 CH4/Kg VS)
- B
Specific methane production (m3 CH4/Kg VS)
- CSTR
Continuous stirred tank reactor
- DSFF
Down-flow Stationary Fixed Film
- HRT
Hydraulic retention time (days)
- K
Kinetic constant of the Chen and Hashimoto model (dimensionless)
- S
Biodegradable substrate concentration (g/l)
- SLR
Superficial loading rate (Kg VS/m2·d)
- SSS
Specific support surface (m2 support surface/m3 digester void volume)
- S0
Initial substrate concentration (g/l)
- VS
Volatile solids (g/l)
- VFA
Volatile Fatty Acids (mg/dm3)
-
Microorganisms specific growth (day-1)
- m
Kinetic constant of Chen and Hashimoto's model (day-1)
-
Retention time (days)
- m
Minimum retention time to avoid microorganisms washout (days) 相似文献
9.
P. Pärt C. M. Wood 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1996,166(1):37-45
Using primary cultures of gill pavement cells from freshwater rainbow trout, a method is described for achieving confluent monolayers of the cells on glass coverslips. A continuous record of intracellular pH was obtained by loading the cells with the pH-sensitive flourescent dye 2,7-bis(2-carboxyethyl)-5(6)-carboxyfluorescein and mounting the coverslips in the flowthrough cuvette of a spectrofluorimeter. Experiments were performed in HEPES-buffered media nominally free of HCO3. Resting intracellular pH (7.43 at extracellular pH=7.70) was insensitive to the removal of Cl– or the application of 4-acetamido-4-isothiocyanatostilbene-2,2-disulfonic acid (0.1 mmol·l–1), but fell by about 0.3 units when Na+ was removed or in the presence of amiloride (0.2 mmol·l–1). Exposure to elevated ammonia (ammonia prepulse; 30 mmol·l–1 as NH4Cl for 6–9 min) produced an increase in intracellular pH (to about 8.1) followed by a slow decay, and washout of the pulse caused intracellular pH to fall to about 6.5. Intracellular non-HCO
3
–
buffer capacity was about 13.4 slykes. Rapid recovery of intracellular pH from intracellular acidosis induced by ammonia prepulse was inhibited more than 80% in Na+-free conditions or in the presence of amiloride (0.2 mmol·l–1). Neither bafilomycin A1 (3 mol·l–1) nor Cl removal altered the intracellular pH recovery rate. The K
m for Na+ of the intracellular pH recovery mechanism was 8.3 mmol·l–1, and the rate constant at V
max was 0.008·s–1 (equivalent to 5.60 mmol H+·l–1 cell water·min–1), which was achieved at external Na+ levels from 25 to 140 mmol·l–1. We conclude that intracellular pH in cultured gill pavement cells in HEPES-buffered, HCO
3
–
-free media, both at rest and during acidosis, is regulated by a Na+/H+ antiport and not by anion-dependent mechanisms or a vacuolar H+-ATPase.Abbreviations
BCECF
2,7-bis(2-carboxyethyl)-5(6)-carboxy-fluorescein
-
BCECF/AM
2,7-bis(2-carboxyethyl)-5(6)-carboxy-fluorescein, acetoxymethylester
-
Cholin-Cl
choline chloride
-
DMSO
dimethyl sulfoxide
-
EDTA
ethylene diamine tetra-acetic acid
-
FBS
foetal bovine serum
-
H
+
-ATPase
Proton-dependent adenosine triphosphatase
-
HEPES
N-[2-hydroxyethyl]piperazine-N[2-ethanesulfonic acid]
-
pH
i
intracellular pH
-
pH
e
extracellular pH
-
PBS
phosphate-buffered saline
-
SITS
4-acetamido-4-isothiocyanatostilbene-2,2-disulfonic acid 相似文献
10.
A. Converti G. Fiorito M. Del Borghi G. Ferraiolo 《Bioprocess and biosystems engineering》1991,7(4):165-170
The present paper deals with the study of the kinetics and thermodynamics of batch enzymic hydrolysis of multisubstrate media in the presence of more than one glucanase. A kinetic model, similar to the one proposed for competitive inhibition, is presented to describe the competition between two substrates, tri- and tetrasaccharides, for the same enzyme, glucoamylase. A literature research on the most recurrent values of the Michaelis-Menten constant also shows a linear relationship between this parameter and the molecular weight of the sugar substrate for a given glucanase.List of Symbols
a dimensionless
empirical parameter in Eq. (1)
-
b dimensionless
empirical parameter in Eq. (1)
-
B dimensionless
empirical parameter in Eq. (6)
-
E kg/m3
enzyme concentration
-
E
a
kcal/mol
activation energy
-
kc kg/m3
competition constant
-
k
M
kg/m3
Michaelis-Menten constant
-
MW kg·10–3
molecular weight
-
r mol/(min·kg)
specific hydrolysis rate of glucoamylase
-
R cal/(°K·mol)
ideal gas constant
-
S kg/m3
substrate concentration
-
T °K
absolute temperature
-
v kg/(m3·h)
hydrolysis rate of glucoamylase
Indices 1
values referring to trisaccharides
- 2
values referring to tetrasaccharides
- 0
starting values
- max
maximum values 相似文献
11.
The distribution of the F420-reactive and F420-nonreactive hydrogenases from the methylotrophic Methanosarcina strain Gö1 indicated a membrane association of the F420-nonreactive enzyme. The membrane-bound F420-nonreactive hydrogenase was purified 42-fold to electrophoretic homogeneity with a yield of 26.7%. The enzyme had a specific activity of 359 mol H2 oxidized · min-1 · mg protein-1. The purification procedure involved dispersion of the membrane fraction with the detergent Chaps followed by anion exchange, hydrophobic and hydroxylapatite chromatography. The aerobically prepared enzyme had to be reactivated anaerobically. Maximal activity was observed at 80°C. The molecular mass as determined by native gel electrophoresis and gel filtration was 77000 and 79000, respectively. SDS gel electrophoresis revealed two polypeptides with molecular masses of 60000 and 40000 indicating a 1:1 stoichiometry. The purified enzyme contained 13.3 mol S2-, 15.1 mol Fe and 0.8 mol Ni/mol enzyme. Flavins were not detected. The amino acid sequence of the N-termini of the subunits showed a higher degree of homology to cubacterial uptake-hydrogenases than to F420-dependent hydrogenases from other methanogenic bacteria. The physiological function of the F420-nonreactive hydrogenase from Methanosarcina strain Gö1 is discussed.Abbreviations
transmembrane electrochemical gradient of H-
- CoM-SH
2-mercaptoethanesulfonate
- F420
(N-l-lactyl--l-glutamyl)-l-glutamic acid phospodiester of 7,8-didemethyl-8-hydroxy-5-deazariboflavin-5-phosphate
- F420H2
reduced F420
- HTP-SH
7-mercaptoheptanoylthreonine phosphate
-
Mb.
Methanobacterium
- PMSF
phenylmethyl-sulfonylfluoride
- Cl3AcOH
trichloroacetic acid 相似文献
12.
The possibility of solving the mass balances to a multiplicity of substrates within a CSTR in the presence of a chemical reaction following Michaelis-Menten kinetics using the assumption that the discrete distribution of said substrates is well approximated by an equivalent continuous distribution on the molecular weight is explored. The applicability of such reasoning is tested with a convenient numerical example. In addition to providing the limiting behavior of the discrete formulation as the number of homologous substrates increases, the continuous formulation yields in general simpler functional forms for the final distribution of substrates than the discrete counterpart due to the recursive nature of the solution in the latter case.List of Symbols
C{N. M} mol/m3
concentration of substrate containing N monomer residues each with molecular weight M
-
{N, M}
normalized value of C{N. M}
-
C
{M} mol/m3 da
concentration of substrate of molecular weight M
-
in
normalized value of C
{M} at the i-th iteration of a finite difference method
-
{M}
normalized value of C
{M}
-
C
0{N.M} mol/m3
inlet concentration of substrate containing N monomer residues each with molecular weight M
-
{N ·M}
normalized value of C0{N. M}
-
0
i
normalized value of C
0
{M} at the i-th iteration of a finite difference method
-
C
0
{M} mol/m3
da initial concentration of substrate of molecular weight M
-
C
tot mol/m3
(constant) overall concentration of substrates (discrete model)
-
C
tot
mol/m3
(constant) overall concentration of substrates (continuous model)
-
D
deviation of the continuous approach relative to the discrete approach
-
i
dummy integer variable
-
I
arbitrary integration constant
-
j
dummy integer variable
-
k
dummy integer variable
-
K
m
mol/m3
Michaëlis-Menten constant for the substrates
-
l
dummy integer variable
-
M da
molecular weight of substrate
-
M
normalized value of M
-
M
da
maximum molecular weight of a reacting substrate
-
N
number of monomer residues of a reacting substrate
-
N
maximum number of monomer residues of a reacting substrate
-
N
total number of increments for the finite difference method
-
Q m3/s
volumetric flow rate of liquid through the reactor
-
S
inert product molecule
-
S
i
substrate containing i monomer residues
-
V m3
volume of the reactor
-
v
max mol/m3 s
reaction rate under saturating conditions of the enzyme active site with substrate
-
v
max{N. M} mol/m3 s
reaction rate under saturating conditions of the enzyme active site with substrate containing N monomer residues with molecular weight M
-
max{N · M}
dimensionless value of vmax{N. M} (discrete model)
-
max{M}
dimensionless value of v
max
{M} (continuous model)
-
mol/m3 s
molecular weight-averaged value of vmax (discrete model)
-
mol.da/m3s
molecular weight-averaged value of vmax (continuous model)
-
v
max
{M} mol.da/m3s
reaction rate under saturating conditions of the enzyme active site with substrate with molecular weight M
-
max
{M}
dimensionless value of vmax{M}
-
max, (i)
dimensionless value of vmax{M} at the i-th iteration of a finite difference method
-
v
max
mol/m3 s
reference constant value of v
max
Greek Symbols
dimensionless operating parameter (discrete distribution)
-
dimensionless operating parameter (continuous distribution)
-
M da
(average) molecular weight of a monomeric subunit
-
M
selected increment for the finite difference method
-
auxiliary corrective factor (discrete model) 相似文献
13.
A model is developed, allowing estimation of the share of inelastic interparticle collisions in total energy dissipation for stirred suspensions. The model is restricted to equal-sized, rigid, spherical particles of the same density as the surrounding Newtonian fluid. A number of simplifying assumptions had to be made in developing the model. According to the developed model, the share of collisions in energy dissipation is small.List of Symbols
b
parameter in velocity distribution function (Eq. (28))
-
c
K
factor in Kolmogoroff spectrum law (Eq. (20))
-
D
t(r
p
) m2/s
characteristic dispersivity at particle radius scale (Eq. (13))
-
E(k, t) m3/s2
energy spectrum as function of k and t (Eq. (16))
-
E
K
(k) m3/s2
energy spectrum as function of k in Kolmogoroff-region (Eq. (20))
-
E
p
dimensionless mean kinetic energy of a colliding particle (Eq. (36))
-
E
cp
dimensionless kinetic energy exchange in a collision (Eq. (37))
-
G(x, s)
dimensionless energy spectrum as function of x and s (Eq. (16))
-
G
B(x)
dimensionless energy spectrum as function of x for boundary region (Eq. (29))
-
G
K(x)
dimensionless energy spectrum as function of x for Kolmogoroff-region (Eq. (21))
-
g m/s2
gravitational acceleration
-
I
cp
dimensionless collision intensity per particle (Eq. (38))
-
I
cv
dimensionless volumetric collision intensity (Eq. (39))
-
k l/m
reciprocal of length scale of velocity fluctuations (Eq. (17))
-
K
dimensionless viscosity (Eq. (13))
-
n(2)
dimensionless particle collision rate (Eq. (12))
-
n(r) l/s
particle exchange rate as function of distance from observatory particle center (Eq. (7))
-
r m
vector describing position relative to observatory particle center (Eq. (2))
-
r m
scalar distance to observatory particle center (Eq. (3))
-
r
pm
particle radius (Eq. (1))
-
s
dimensionless time (Eq. (10))
-
SC kg/ms3
Severity of collision (Eq. (1))
-
t s
time (Eq. (2))
-
u(r, t) m/s
velocity vector as function of position vector and time (Eq. (2))
-
u(r, t) m/s
magnitude of velocity vector as function of position vector and time (Eq. (3))
-
u
r(r, t) m/s
radial component of velocity vector as function of position vector and time (Eq. (3))
-
u
r
(r, t) m/s
magnitude of radial component of velocity vector as function of position vector and time (Eq. (3))
-
u
(r, t) m/s
latitudinal component of velocity vector as function of position vector and time (Eq. (3))
-
u
(r, t) m/s
magnitude of latitudinal component of velocity vector as function of position vector and time (Eq. (3))
-
u
(r, t) m/s
longitudinal component of velocity vector as function of position vector and time (Eq. (3))
-
u
(r, t) m/s
magnitude of longitudinal component of velocity vector as function of position vector and time (Eq. (3))
-
u
gsm/s
superficial gas velocity
-
u(r) m/s
root mean square velocity as function of distance from observatory particle center (Eq. (3))
-
ur(r) m/s
root mean square radial velocity component as function of distance from observatory particle center (Eq. (4))
-
u (r) m/s
root mean square latitudinal velocity component as function of distance from observatory particle center (Eq. (4))
-
u (r) m/s
Root mean square longitudinal velocity component as function of distance from observatory particle center (Eq. (4))
-
w(x)
dimensionless root mean square velocity as function of dimensionless distance from observatory particle center (Eq. (11))
-
V
pm3
particle volume (Eq. (36))
-
w(2)
dimensionless root mean square collision velocity (Eq. (34))
-
w
*
parameter in boundary layer velocity equation (Eq. (24))
-
x
dimensionless distance to particle center (Eq. (9))
-
x
*
value of x where G
Band G
K-curves touch (Eq. (32))
-
x
K
dimensionless micro-scale (Kolmogoroff-scale) of turbulence (Eq. (15))
-
volumetric particle hold-up
-
m2/s3
energy dissipation per unit of mass
-
m2/s
kinematic viscosity
-
kg/m3
density
-
(r) m3/s
fluid-exchange rate as function of distance to observatory particle center
-
Latitudinal co-ordinate (Eq. (5))
-
Longitudinal co-ordinate (Eq. (5)) 相似文献
14.
Exchange of CO2 and O2 and chlorophyll fluorescence were measured in the presence of 360 1 · 1–1 CO2 in nitrogen in Helianthus annuss L. leaves which had been preconditioned in the dark or at a photon flux density (PFD) of 24 mol · m–2 · s–1 either in 21 or 0% O2. An initial light-dependent O2 outburst of 6 mol · m–2 was measured after aerobic dark incubation. It was attributed to the reduction of electron carriers, predominantly plastoquinone. The maximum initial rate of O2 evolution at PFD 8000 mol · m–2 · s–1 was 170 mol · m–2 · s–2 or about four times the steady CO2-and light-saturated rate of photosynthesis. Fluorescence measurements showed that the rate was still acceptor-limited. Fast O2 evolution ceased after electron carriers were reduced in the dark-adapted leaf, but continued for a short time at the lower rate of 62 mol · m–2 · s–1 in the light-adapted leaf. The data are interpreted to show that enzymes involved in 3-phosphoglycerate reduction are dark-inhibited, but were fully active in low light. In a dark-adapted leaf, respiratory CO2 evolution continued under nitrogen; it was partially inhibited by illumination. Prolonged exposure of a leaf to anaerobic conditions caused reducing equivalents to accumulate. This was shown by a slowly increasing chlorophyll fluorescence yield which indicated the reduction of the PSII acceptor QA in the dark. When the leaf was illuminated, no O2 evolution was detected from short light pulses, although transient O2 production was appreciable during longer light pulses. This indicates that an electron donor (pool size about 2–3 e/PSII reaction center) became reduced in the dark and the first photons were used to oxidise this donor instead of water.Abbreviations Chl
chlorophyll
- CRC
carbon reduction cycle
- GAPDH
NADP-glyceraldehyde-phosphate dehydrogenase
- PFD
photon flux density
- PGA
3-phosphoglycerate
- RuBP
ribulose bisphosphate
- TCA
tricarboxylic acid cycle
To whom correspondence should be addressedThis work received support by the Estonian Academy of Sciences, the Gottfried-Wilhelm-Leibniz Program of the Deutsche For-schungsgemeinschaft and the Sonderforschungsbereich 251 of the University of Würzburg. 相似文献
15.
Inhibition of auxin-stimulated growth of pea stem segments by a specific nonasaccharide of xyloglucan 总被引:3,自引:0,他引:3
Hemicellulose extracted from cell walls of suspension-cultured rose (Rosa Paul's Scarlet) cells was digested with cellulase from Trichoderma viride. The quantitatively major oligosaccharide products, a nonasaccharide and a heptasaccharide derived from xyloglucan, were purified by gel permeation chromatography. The nonasaccharide was found to inhibit the 2,4-dichlorophenoxy-acetic-acid-induced elongation of etiolated pea (Pisum sativum) stem segments. This confirms an earlier report (York et al., 1984, Plant Physiol. 75, 295–297). The inhibition of elongation by the nonasaccharide showed a maximum at around 10-9M with higher and lower concentrations being less effective. The heptasaccharide did not significantly inhibit elongation at 10-7–10-10M and also did not affect the inhibition caused by the nonasaccharide when co-incubated with the latter.Abbreviations 2,4-D
2,4-dichlorophenoxyacetic acid
- XG
xyloglucan
- XG7
xyloglucan heptasaccharide (Glc4·Xyl3)
- XG9
xyloglucan nonasaccharide (Glc4·Xyl3·Gal·Fuc) 相似文献
16.
Changes in carp myosin ATPase induced by temperature acclimation 总被引:8,自引:0,他引:8
G. C. Hwang S. Watabe K. Hashimoto 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1990,160(3):233-239
Summary Myosins were isolated from dorsal ordinary muscles of carp acclimated to 10°C and 30°C for a minimum of 5 weeks and examined for their ATPase activities. Ca2+-ATPase activity was different between myosins from cold-and warm-acclimated carp, especially at KCl concentrations ranging from 0.1 to 0.2 M, when measured at pH 7.0. The highest activity was 0.32 mol Pi·min-1·mg-1 at 0.2 M KCl for cold-acclimated carp and 0.47 mol Pi·min-1·mg-1 at 0.1 M KCl for warm-acclimated fish. The pH-dependency of Ca2+-ATPase activity at 0.5 M KCl for both carp was, however, similar exhibiting two maxima around 0.3 mol Pi·min-1·mg-1 at pH 6 and 0.4 mol Pi·min-1·mg-1 at pH 9. K+(EDTA)-ATPase activity at pH 7.0 neither exhibited differences between both myosins. It increased with increasing KCl concentration showing the highest value of about 0.4 mol Pi·min-1·mg-1 at 0.6–0.7 M KCl. Actin-activated myosin Mg2+-ATPase activity was markedly different between cold-and warm-acclimated carp. The maximum initial velocity was 0.53 mol Pi·min-1·mg-1 myosin at pH 7.0 and 0.05 M KCl for cold-acclimated carp, which was 1.6 times as high as that for warm-acclimated carp. These differences were in good agreement with those obtained with myofibrillar Mg2+-ATPase activity between both carp. No differences were, however, observed in myosin affinity to actin. Differences in myosin properties between cold- and warm-acclimated carp were further evidenced by its thermal stability. The inactivation rate constant of myosin Ca2+-ATPase was 25·10-4·s-1 at 30°C and pH 7.0 for cold-acclimated carp, which was about 4 times as high as that for warm-acclimated carp. Light chain composition did not differ between both carp myosins. The differences in a primary structure of the heavy chain subunit was, however, clearly demonstrated between both myosins by peptide mapping.Abbreviations
ATPase
adenosine 5-triphosphatase
-
DTNB 5,5
dithio-bis-2-nitrobenzoic acid
-
DTT
dithiothreitol
-
EGTA
ethyleneglycol bis (-aminoethylether)-N,N,N,N-tetraacetic acid
-
K
D
inactivation rate constant
-
SDS
sodium dodecyl sulfate
-
SDS-PAGE
SDS-polyacrylamide gel electrophoresis 相似文献
17.
Photoinhibition of photosynthesis represents a mechanism for the long-term regulation of photosystem II 总被引:19,自引:0,他引:19
The obligate shade plant, Tradescantia albiflora Kunth grown at 50 mol photons · m–2 s–1 and Pisum sativum L. acclimated to two photon fluence rates, 50 and 300 mol · m–2 · s–1, were exposed to photoinhibitory light conditions of 1700 mol · m–2 · s–1 for 4 h at 22° C. Photosynthesis was assayed by measurement of CO2-saturated O2 evolution, and photosystem II (PSII) was assayed using modulated chlorophyll fluorescence and flash-yield determinations of functional reaction centres. Tradescantia was most sensitive to photoinhibition, while pea grown at 300 mol · m–2 · s–1 was most resistant, with pea grown at 50 mol · m–2 · s–1 showing an intermediate sensitivity. A very good correlation was found between the decrease of functional PSII reaction centres and both the inhibition of photosynthesis and PSII photochemistry. Photoinhibition caused a decline in the maximum quantum yield for PSII electron transport as determined by the product of photochemical quenching (qp) and the yield of open PSII reaction centres as given by the steady-state fluorescence ratio, FvFm, according to Genty et al. (1989, Biochim. Biophys. Acta 990, 81–92). The decrease in the quantum yield for PSII electron transport was fully accounted for by a decrease in FvFm, since qp at a given photon fluence rate was similar for photoinhibited and noninhibited plants. Under lightsaturating conditions, the quantum yield of PSII electron transport was similar in photoinhibited and noninhibited plants. The data give support for the view that photoinhibition of the reaction centres of PSII represents a stable, long-term, down-regulation of photochemistry, which occurs in plants under sustained high-light conditions, and replaces part of the regulation usually exerted by the transthylakoid pH gradient. Furthermore, by investigating the susceptibility of differently lightacclimated sun and shade species to photoinhibition in relation to qp, i.e. the fraction of open-to-closed PSII reaction centres, we also show that irrespective of light acclimation, plants become susceptible to photoinhibition when the majority of their PSII reaction centres are still open (i.e. primary quinone acceptor oxidized). Photoinhibition appears to be an unavoidable consequence of PSII function when light causes sustained closure of more than 40% of PSII reaction centres.Abbreviations Fo and Fo
minimal fluorescence when all PSII reaction centres are open in darkness and steady-state light, respectively
- Fm and Fm
maximal fluorescence when all PSII reaction centres are closed in darkand light-acclimated leaves, respectively
- Fv
variable fluorescence
- (Fm-Fo)
under steady-state light con-ditions
- Fs
steady-state fluorescence in light
- QA
the primary,stable quinone acceptor of PSII
- qNe
non-photochemical quench-ing of fluorescence due to high energy state
- (pH); qNi
non-photochemical quenching of fluorescence due to photoinhibition
- qp
photochemical quenching of fluorescence
To whom correspondence should be addressedThis work was supported by the Swedish Natural Science Research Council (G.Ö.) and the award of a National Research Fellowship to J.M.A and W.S.C. We thank Dr. Paul Kriedemann, Division of Forestry and Forest Products, CSIRO, Canberra, Australia, for helpful discussions. 相似文献
18.
W. -M. Weber B. Dannenmaier W. Clauss 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1993,163(2):153-159
The dorsal skin of the leech Hirudo medicinalis was used for electrophysiological measurements performed in Ussing chambers. The leech skin is a tight epithelium (transepithelial resistance = 10.5±0.5 k· cm-2) with an initial short-circuit current of 29.0±2.9 A·cm-2. Removal of Na+ from the apical bath medium reduced short-circuit current about 55%. Ouabain (50mol·l-1) added to the basolateral solution, depressed the short-circuit current completely. The Na+ current saturated at a concentration of 90 mmol Na+·l-1 in the apical solution (K
M=11.2±1.8 mmol·l-1). Amiloride (100 mol·l-1) on the apical side inhibited ca. 40% of the Na+ current and indicated the presence of Na+ channels. The dependence of Na+ current on the amiloride concentration followed Michaclis-Menten kinetics (K
i=2.9±0.4 mol·l-1). The amiloride analogue benzamil had a higher affinity to the Na+ channel (K
i=0.7±0.2 mol·l-1). Thus, Na+ channels in leech integument are less sensitive to amiloride than channels known from vertebrate epithelia. With 20 mmol Na+·l-1 in the mucosal solution the tissue showed an optimum amiloride-inhibitable current, and the amiloride-sensitive current under this condition was 86.8±2.3% of total short-circuit current. Higher Na+ concentrations lead to a decrease in amiloride-blockade short-circuit current. Sitmulation of the tissue with cyclic adenosine monophosphate (100 mol·l-1) and isobutylmethylxanthine (1 mmol·l-1) nearly doubled short-circuit current and increased amiloride-sensitive Na+ currents by 50%. By current fluctuation analysis we estimated single Na+ channel current (2.7±0.9 pA) and Na+ channel density (3.6±0.6 channels·m-2) under control conditions. After cyclic adenosine monophosphate stimulation Na+ channel density increased to 5.4±1.1 channels·m-2, whereas single Na+ channel current showed no significant change (1.9±0.2 pA). These data present a detailed investigation of an invertebrate epithelial Na+ channel, and show the similarities and differences to vertebrate Na+ channels. Whereas the channel properties are different from the classical vertebrate Na+ channel, the regulation by cyclic adenosine monophosphate seems similar. Stimulation of Na+ uptake by cyclic adenosine monophosphate is mediated by an increasing number of Na+ channels.Abbreviations
slope of the background noise component
- ADH
antidiuretic hormone
- cAMP
cyclic adenosine monophosphate
-
f
frequency
-
f
c
coner frequency of the Lorentzian noise component
- Hepes
N-hydroxyethylpiperazine-N-ethanesulphonic acid
- BMX
isobutyl-methylxanthine
-
i
Na
single Na+ channel current
-
I
Na
max, maximal inhibitable Na+ current
-
I
SC
short circuit current
-
K
i
half maximal blocker concentration
-
K
M
Michaelis constandard error of the mean
-
S
(f)
power density of the Lorentzian noise component
-
S
0
plateau value of the Lorentzian noise component
- TMA
tetramethylammonium
- Trizma
TRIS-hydroxymethyl-amino-methane
-
V
max
maximal reaction velocity
-
V
T
transepithelial potential
-
K
half maximal blocker concentration 相似文献
19.
Jonas Collén Miguel Jiménez Del Rio Guillermo García-Reina Marianne Pedersén 《Planta》1995,196(2):225-230
Production of hydrogen peroxide has been found in Ulva rigida (Chlorophyta). The formation of H2O2 was light dependent with a production of 1.2 mol·g FW–1·h–1 in sea water (pH 8.2) at an irradiance of 700 mol photons m–2·s–1. The excretion was also pH dependent: in pH 6.5 the production was not detectable (< 5 nmol·g FW–1·h–1) but at pH 9.0 the production was 5.0 mol·g FW–1·h–1. The production of H2O2 was totally inhibited by 3-(3,4-dichlorophenyl)-1,1 dimethylurea (DCMU). The ability of U. rigida growing in tanks (7501) under a natural light regime to excrete H2O2 was checked and found to be seven times higher at 08.00 hours than other times of the day. The H2O2 concentration in the cultivation tank (density: 2 g FW·l–1) reached the highest value (3 M) at 11.00 hours. Photosynthesis was not influenced by H2O2 formation. The H2O2 is suggested to come from the Mehler reaction (pseudocyclic photophosphorylation). With an oxygen evolution of 120 mmol·g FW–1·h–1 at pH 8.2 and 90 mmol·g FW–1·h–1 at pH 9.0, 0.5% and 2.7% of the electrons were used for extracellular H2O2 production. The H2O2 production is sufficiently high to be of physiological and ecological significance, and is suggested to be a part of the defence against epi and endophytes.Abbreviations ACL
artificial, continuous light
- DCMU
3-(3,4-dichlorophenyl)-1,1-dimethylurea
- GNL
greenhouse
- LDC
Luminol-dependent chemiluminescence
- SOD
Superoxide dismutase
This investigation was supported by SAREC (Swedish Agency for Research Cooperation with Developing Countries), Hierta-Retzius Foundation, Marianne and Marcus Wallenberg Foundation, the Swedish Environmental Protection Board, and CICYT Spain. 相似文献
20.
Epidermal peels of Valerianella locusta were acid-treated for 1 h at pH 3.9 to kill all cells other than guard cells. These guard-cell preparations were used to explore the steady-state one-way fluxes and the cytoplasmic and vacuolar contents of abscisic acid (ABA). The method of compartmental analysis has been applied. The intracellular ABA concentrations were surprisingly high. At an external pH of 5.8 the cytoplasm contained 1.28 mmol·dm-3 of ABA, twice of the amount which accumulated in the vacuoles (0.57 mmol·dm-3). The fluxes of ABA at the plasmalemma (oc=oc=0.43 fmol · cell –1 · h –1) were higher than those at the tonoplast (cv=vc=0.12 fmol · cell –1 · h –1). Moderate stress (0.1 and 0.3 mol·dm-3 sorbitol in the medium) caused a change in the kinetics of ABA movement. The rate constants of the fluxes from the cytoplasm into the vacuole (cv) and into the apoplast (co) were increased while the rate constant of the flux from the vacuoles into the cytoplasm (vc) was decreased. As a consequence the amount of ABA sequestered in the vacuole remained unchanged; the cytoplasmic ABA content, however, was reduced to only 20% of that found in the control treatments (no sorbitol in the medium). Under moderate stress, one Valerianella guard cell released rapidly about 0.36 fmol·cell-1 to its direct cell-wall space. This surprising result is discussed in regard to rapid stomatal closure under reduced water supply.Abbreviations ABA
abscisic acid
- FC
fusicoccin 相似文献