(Similar analyses of the other subsets presented in the SI.) The chiral SFG response of these two subsets is shown in Figure (purple). We chose these two subsets because they represent well the range of line shapes encountered when calculating the chiral response of various groups of water molecules around LK7b. The first hydration shell response is relatively simple (Figure , left), whereas the N-H-bound water molecules produce a more complicated line shape (Figure , right). We first calculated the symmetric and asymmetric stretch chiral SFG responses (Figure ), as detailed above. We then fit the signals (black solid lines, Figure ) with the residuals of the fitting shown above Figure (yellow solid lines). The signal of the first hydration shell subset is fit with a single pair of peaks (left, dashed lines, Figure ) and the signal of the water subset hydrogen-bonded to N-H groups is fit with two pairs (right, dashed lines, Figure ). We chose to fit the spectra with a minimal number of pairs to avoid overfitting.