\[M_{-\kappa,\mu}\left(4\kappa x\right)=\frac{2\Gamma\left(2\mu+1\right)}{\kappa%
^{\mu-\frac{1}{2}}}\left(\frac{x\zeta}{1+x}\right)^{\frac{1}{4}}I_{2\mu}\left(%
4\kappa\zeta^{\frac{1}{2}}\right){\left(1+O\left(\kappa^{-1}\right)\right)},\]