Table 1.

Example of Agent-Associated Reactions: Receptor-Ligand Binding, Trafficking, and Intracellular Signaling

Description	Equation
Diffusing Molecule – [L] (M)	$\frac{d[L]}{dt}=k_{\mathit{synth}}-(\rho /N_{AV})(k_f[L][Y_1]+k_r[Y_2])$
Free Molecule – [Y1] (#/cell)	$\frac{d[Y_1]}{dt}=-k_f[L][Y_1]+k_r[Y_2]+k_{\mathit{rec}}[Y_3]$
Bound Receptor – [Y2] (#/cell)	$\frac{d[Y_2]}{dt}=k_f[L][Y_1]-k_r[Y_2]-k_{\mathit{int}}[Y_2]$
Internalized Receptor – [Y3] (#/cell)	$\frac{d[Y_3]}{dt}=k_{\mathit{int}}[Y_2]-k_{\mathit{rec}}[Y_3]$
Signaling Molecule – [Y4] (#/cell)	$\frac{d[Y_4]}{dt}=k_{\mathit{sig}}[Y_3]-k_{\mathit{dec}}[Y_4]$
Response Factor – [Y5] (#/cell)	$\frac{d[Y_5]}{dt}=k_{\mathit{resp}}[Y_4]-k_d[Y_5]$

k_f – association rate constant (1/M*s), k_r – dissociation rate constant (1/s), k_int – internalization rate constant (1/s), k_rec – recycling rate constant (1/s), k_synth – synthesis rate constant (#/cell*s), k_sig – signaling rate constant (1/s), k_dec – signal decay rate constant (1/s), k_resp – signal response rate constant (1/s), k_d – response decay rate constant (1/s), ρ (cells/L), N_AV – Avogadro’s constant (#/mol)