Parameter	Description	Value	Intuition for value	Reference
${\lambda }_N$	Nodal source production rate	8e-6 μM/sec	~3 Nodal ligand molecules/min per cell	-
DN	Free Nodal diffusion rate	30 μm2/sec	MSD of ~ 650 μm after 2 hr	Müller et al., 2012
k1	Nodal-Receptor association rate	10/ μM*sec	Mean time to capture of ~ 2 s at initial Oep concentration	De Crescenzo et al., 2003
k-1	Nodal-Receptor dissociation rate	6.25e-4/sec	Mean time to dissociation of 25 min	De Crescenzo et al., 2003
k2	Nodal-Receptor complex internalization rate	1.7e-3/sec	Mean time to internalization of 10 min	Jullien and Gurdon, 2005
k3	Receptor production rate	1.6e-5 μM/sec	Approximately 0.7 molecules/sec produced by a cell of 10 μm diameter	-
k-R	Receptor degradation rate (ligand independent)	2.7e-4/sec	Average lifetime of 1 hr	-
N(x,t = 0)	Free ligand initial condition	0 μM for all x	Embryo starts out with no Nodal.	-
R(x,t = 0)	Free receptor initial condition	0.06 μM for all x	Approximately 2900 molecules for a cell of 10 μm diameter	Dyson and Gurdon, 1998
C(x,t = 0)	Nodal-Receptor complex initial condition	0 μM for all x	Embryo starts out with no receptor-ligand complexes.	-