\(\Delta \sigma^i_{RC}\) is the effect of ring current on the chemical shielding. Usually this is only significant for proton shift and is thus only calculated for the H\(\alpha\) and amide protons. The ring current is calculated by a simple point-dipole model equation \[\Delta \sigma^i_{RC}=iB\frac{1-3 \cos^2(\theta)}{r^3}\] The model depends on the parameters \(i\), which is the side-chain-specific ring-current intensity relative to benzene, \(B\), which is a constant in the model, and the vector \(\mathbf{r}\), which is the vector from the proton to the center of the aromatic ring. \(\theta\) is the angle between \(\mathbf{r}\) and the vector normal to the aromatic ring system. The cut-off for calculating ring current is 8 Å in Procs15 and the value for \(i\) and \(B\) are taken from \cite{Christensen_2011}.