A Small Point Missed...

When mass measurement are apart from the gravitational constant $G_o$,

$q_e=\cfrac{1}{9.029022e26}=1.107540e-27=m_e$

is also the elementary gravitational mass, $m_e$.

$m_e*77=\cfrac{1}{9.029022e26}*77=8.5281e-26$

$m_e*38=\cfrac{1}{9.029022e26}*38=4.2087e-26$

and with the maximum attractive force, considering shielding,

$\left\lfloor\cfrac{77}{2}\right\rfloor=\left\lfloor38.5\right\rfloor=39$

$m_e*39=\cfrac{1}{9.029022e26}*39=4.3194e-26$

We could be talking about the atomic mass constant or the neutron rest mass.  A proton as an elementary charge particle does not experience a force in a gravitational field and have no gravitational mass.  But it has inertia under an electric field.