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821.
Camillo Branca Vincenzo Plazzi Marina Vitto Fabrizio Bordi Donatella Serafini Fracassini Nello Bagni 《Phytochemistry》1975,14(12):2545-2550
The 1,2-benzisothiazol-3-yl-acetic and -3-yl-butyric acids and their ethyl esters, amides and nitriles are generally active in the split pea stem test, induce an increase in both length and fresh weight of pea internodes, inhibit the development of pea roots, and, with some exceptions (1,2-benzisothiazol-3-yl-butyric amide and nitrile), induce the production of ethylene by pea segments. Moreover they stimulate cell multiplication and raise the degree of hydration of Helianthus tuberosus explants grown in vitro. These activities are often similar or sometimes higher than those of IAA. By contrast, the 1,2-benzisothiazole derivatives having a side chain with an odd number of carbon atoms (-3-yl-carboxylic and propionic acids, amides, ethyl esters and nitriles) are inactive or show a far lower activity. 相似文献
822.
823.
Guido Greco Jr. Donatella Albanesi Maria Cantarella Liliana Gianfreda Rosaria Palescandolo Vincenzo Scardi 《Applied microbiology and biotechnology》1979,8(4):249-261
Summary An ultrafiltration membrane enzymatic reactor is used in connection with different reacting systems.The experimental conditions are such that the enzyme, which operates at fairly high concentration levels because of the concentration polarization phenomena taking place in the reactor, is still in soluble form.The analysis of the system unsteady-state response enables the identification of the mechanism of enzyme deactivation and the extraction of the kinetic parameters of both the deactivation and the main reaction.The stabilizing effect observed in connection with enzyme entrapment within an inert gel deposited onto the U.F. membrane active surface is also discussed.List of Symbols A
U.F. membrane cross sectional area cm2
- CE
Enzyme concentration mg/ml
- CEI
Enzyme concentration at the active membrane surface mg/ml
- CE
Mean enzyme concentration mg/ml
- c
s
o
Substrate concentration in the feed m moles/ml
- c
s
u
Substrate concentration in the outlet m moles/ml
- DE
Enzyme diffusivity cm2/s
- Km
michaelis constant mM
- k2
Kinetic constant of the enzymatic reaction m moles/mg s
- kd
Kinetic constant of the enzyme deactivation reaction s–1
- No
Initial amount of active enzyme mg
- N(t)
Active enzyme amount at reaction time t mg
- Q
Flow rate ml/s
- r
Rate of the main reaction m moles/ml s
- t
Reaction time s
- t*
Reaction time at which product concentration in the outlet is within ± 2% of the steady-state value s
- v
Fluid velocity cm/s
- V
Cell volume ml
- VB
Volume within which 99% of the enzyme fed is contained at the steady-state ml
- VS
Volume within which 99% of the total substrate concentration drop occurs at the steady-state ml
- x
Distance upstream the membrane measured from the membrane surface cm 相似文献
824.
We report on the effects that the presence of ethylene glycol or glycerol has on the oxygen affinity of hemoglobin. We attribute these effects to an altered equilibrium between T and R quaternary conformations of hemoglobin and separate them into bulk-electrostatic and non-bulk-electrostatic contributions to the standard free-energy difference between the R and T states. 相似文献
825.