The frequency distribution of OH stretches around LK7b is composed of two component peaks (the first and second columns, Figure ), whereas the distribution around LE7b is composed of three component peaks (the third column, Figure ), including an emergent peak at a very high frequency (3684 cm -1 ). This peak is most likely due to water molecules interacting weakly with the protein, perhaps with one OH group facing the air. We presume that such molecules also exist in the LK7b system. However, because the protein-hydration shell interactions are more stable in the LK7b system relative to the LE7b system, as shown previously, these water molecules may contribute relatively less to the total aqueous response. It is important to note that a water molecule need not be strongly hydrogen-bonded to the protein to be part of a stable chiral hydration structure. The low frequencies in the frequency distribution around LK7b may correspond partially to water molecules that are geometrically constrained by the stable protein structure and as a result form strong hydrogen bonds with other water molecules in the first hydration shell. Hence, chiral SFG is not only a reporter of hydrogen bond strength in the first hydration shell, but also of the geometric, collective order of water molecules around the chiral biomolecular scaffolds.