Solvation
of CO<sub>2</sub> in Water: Effect of RuBP
on CO<sub>2</sub> Concentration in Bundle Sheath of C<sub>4</sub> Plants
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Abstract
An understanding of the temperature-dependence
of solubility of
carbon dioxide (CO<sub>2</sub>) in water is important for many industrial
processes. Voluminous work has been done by both quantum chemical
methods and molecular dynamics (MD) simulations on the interaction
between CO<sub>2</sub> and water, but a quantitative evaluation of
solubility remains elusive. In this work, we have approached the problem
by considering quantum chemically calculated total energies and thermal
energies, and incorporating the effects of mixing, hydrogen bonding,
and phonon modes. An overall equation relating the calculated free
energy and entropy of mixing with the gas-solution equilibrium constant
has been derived. This equation has been iteratively solved to obtain
the solubility as functions of temperature and dielectric constant.
The calculated solubility versus temperature plot excellently matches
the observed plot. Solubility has been shown to increase with dielectric
constant, for example, by addition of electrolytes. We have also found
that at the experimentally reported concentration of enzyme RuBP in
bundle sheath cells of chloroplast in C<sub>4</sub> green plants,
the concentration of CO<sub>2</sub> can effectively increase by as
much as a factor of 7.1β38.5. This stands in agreement with
the observed effective rise in concentration by as much as 10 times