1980; Maxwell et al. 1998; Ruuska et al. 2000). Fig. 4 Selleckchem KU 57788 Gas exchange measurements of intact leaves can be studied in MIMS cuvettes. The sealed chamber contains a leaf disk and is purged with N2 before addition of 2% 12CO2 and 20% 18O2. The upper figure shows the raw signals (in Volt) at m/z = 32 for photosynthetic water splitting, m/z = 36 for oxygen uptake pathways that include oxygenation reaction from Rubisco and terminal oxidase reaction in respiration. The m/z = 44 shows rates of CO2 uptake. The lower part of this figure depicts absolute rates of respiration and photosynthesis. The initial dark period determines net rates of 18O2 uptake and CO2 generation from respiration. At the arrow illumination commences and there
is net generation of 16O2, a net CO2 uptake and slightly increased 18O2 uptake. After a few minutes the total [CO2] in the chamber begins to fall and Rubisco oxygenase reactions increase, as seen by the dramatic increase in 18O2 uptake. For more details see (Canvin et al. 1980; Maxwell et al. 1998) Liquid-phase find protocol measurements of photosynthesis in solution (i.e., algae, chloroplasts) are equivalent in concept to leaf gas exchange (Badger and Andrews 1982; Espie et al. 1988; Hanson et al. 2003), except that there are different solubilities of the gases which alter measurement sensitivities. Thus, O2 is
measured with greater sensitivity while CO2 may be less sensitive due to the fact that CO2 equilibrates O-methylated flavonoid with hydrogencarbonate (formerly check details termed bicarbonate) in solution and CO2 may be only a small fraction of the total inorganic carbon used for photosynthesis. The ratio of CO2/hydrogen carbonate will depend on the pH of the assay reaction and will decrease at alkaline pH. Liquid-phase measurements are particularly useful for studying aquatic photosynthesis, since for such systems there are no other techniques which allow for detailed examinations of both CO2 and O2 fluxes associated with photosynthesis (Badger et al. 1994; Palmqvist et al. 1994; Woodger et al. 2005; Rost et al. 2006). Carbonic anhydrase
The carbonic anhydrase (CA) enzymes (EC 4.2.1.1) are vital for plant and animal metabolism as they equilibrate CO2 concentrations in solution with hydrogencarbonate. The catalyzed CA reaction is extremely rapid and involves a number of enzymatic intermediates and rapid proton equilibration steps (Gibbons and Edsall 1963; Lindskog and Coleman 1973; Silverman and Lindskog 1988). However, the overall reaction can be described in simplified form as a single rate determining hydration/dehydration reaction; i.e. $$ \textCO_2 \, + \,\textH_2 \textO\,\undersetk_2 \oversetk_1 \longleftrightarrow\,\textHCO_3^ – \, + \,\textH^ + $$ (8)Using a MIMS approach, the forward hydration rate k 1 and reverse dehydration rate k 2 can be determined (Hillier et al. 2006; McConnell et al. 2007), or an expression of reaction rate based on the change in enrichment, i.e., 18α from Eq.