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Revision as of 05:59, 15 April 2018
The definition of nitrogen fixation
•What is nitrogen fixation?
Nitrogen → ammonia (NH3) or other molecules available to living organisms.
What is nitrogen fixation for?
-global food supply
-reduce the use of chemical nitrogen fertilizers
Nitrogen fixation is essential for life.
The methods of nitrogem fixation
Nitrogen cycle
•Nitrogen fixation:
—N2 → plants by bacteria
•Nitrification:
—ammonium → nitrite → nitrate
—Absorbed by plants
•Denitrification:
—Release N to atmosphere
Haber-Bosch process
N2 + 3H2 → 2NH3(ΔH° = −91.8 kJ)
High temperature
High pressure
Need too much energy
Biological nitrogen fixation
Mild reaction conditions
Relatively inexpensive
High efficiency
Environmentally friendly
The choose of nitrogenase
Molybdenum
(MoFe)-dependent
Vanadium
(VFe)-dependent
Iron-only
(FeFe)-dependent
MoFe has been studied extensively
Nitrogen Fixation Gene Cluster
The minimal nif genes required for nitrogen fixation.
General principle of biological nitrogen fixation
01 Hydrolysis of ATP | 03 MoFe protein forming complexes with low-potential donor | |
Chemical energy (ATP)→Solar energy |
||
02 Electron transfer | 04 Reduce N2 to NH3 |
01 Receive light signals | 03 MoFe protein forming complexes with low-potential donor | |
02 Electron transfer | 04 Reduce N2 to NH3 |
The characteristics of whole-cell
The property and advantage of whole-cells
•Fast proliferation to enable large-scale application
•Good portability to permit on-site monitoring
•Inexpensive and easy to preserve
• Intracellular cascade reactions to amplify signals
• Excellent specificity, sensitivity and stability