Protein hydration water: Focus on low density and high density local structures upon cooling

•Local structures were studied in protein hydration water through order parameters.•Contributions of low- and high-density liquids were found in protein hydration water.•Hydration water has higher fraction of high-density structures than bulk water.•Hydration water is mostly high-density in the range 300-200 K as per the q-parameter•In hydration water low-density features prevail below 220 K as per the V4 parameter