Definition: Standard transformed Gibbs energy change for a reaction written in terms of biochemical reactants. Usage: Delta-G is represented as a 5-tuple of delta-G'0, temperature, ionic strength , pH, and pMg . A conversion in BioPAX may have multiple Delta-G values, representing different measurements for delta-G'0 obtained under the different experimental conditions.
Source:http://www.biopax.org/release/biopax-level3.owl#DeltaG