In the cell, Ras GTPases function as membrane-bound molecular switches for a variety of cell signaling pathways. Ras isoforms have long been of interest because of the connection between amino acid mutations and tumorigenesis. Much research focused on Ras has used truncated, solubilized constructs, which exclude the membrane-binding domain and therefore ignore the effects of membrane binding on Ras function. Since the membrane is a highly charged surface, it could have a significant impact on the electrostatic environment at or near the protein-protein interface. Here, we use a thiocyanate probe chemically inserted into the Ras-binding domain of RalGDS to investigate the effect of membrane binding at the Ras active site. Changes in the electric field caused by the membrane were measured by the probe as vibrational energy shifts in the infrared (IR) spectrum. For a selection of mutants which caused large shifts at this interface on the soluble H-Ras construct, binding to a 30% phosphatidylserine (PS)/70% phosphatidylcholine (PC) nanodisc caused reduced shifts compared to the solubilized counterparts. Additionally, the vibrational probe bonded to the wildtype (WT) Ras construct demonstrated a shift of 0.7 cm