PD L1 FAQ

• Should-I always represent reversible reactions as two separate processes?
• Can-we represent reversible interactions with a single association or dissociation glyphs?
• Were should consumption edges of an association process meet?

Should-I always represent reversible reactions as two separate processes?

No. A reversible process can be represented by a single Process Node if this process is not modulated. The following process, representing the transition of a channel between open and closed state, is correct:

However, the following reversible reaction is modulated by two simple chemicals. One cannot understand which direction is modulated by each simple chemical. It is incorrect.

On the contrary, the following diagram is valid because the two directions are represented and the modulations are unambiguous.

Can-we represent reversible interactions with a single association or dissociation glyphs?

No. A dissociation glyph represents only the ... dissociation, while the association glyph represents only the association process. The following is incorrect:

A reversible interaction must therefore be represented by separate association and dissociation processes. The following is correct:

If there are no modulations on the association or dissociation, a reversible interaction can be represented by a regular process node, as follows:

Were should consumption edges of an association process meet?

The consumption edges should always meet in a single point outside the symbol representing a process. This rule applies for association as well. The point can be on the perimeter of the association symbol (center) or away from it (right).