NME1 and neoplasm: Using 1-pHis and 3-pHis antibodies, tumor tissues were found to have persistent histidine phosphorylation of multiple proteins, including NME1/2, using fresh tumor samples as well as tumor samples that had been flash frozen in liquid nitrogen up to 30 min after removal, although the intensity of histidine phosphorylation clearly diminishes with longer time intervals prior to freezing (Figure 3A,B).