title: Structural changes at the heme induced by freezing hemoglobin.
abstract: A dramatic change occurs in the vibrational properties of the iron-histidine bond, trans to the oxygen binding site, on freezing deoxyhemoglobin. The large, quaternary structure-dependent differences in the shape and frequency of the iron-histidine mode observed in resonance Raman scattering measurements above freezing ae significantly diminished by the freezing event and the scattering intensity increases substantially. On further reduction in temperature to 10 K this broad line becomes narrow and shifts to a higher frequency. These data implicate dynamical processes and protein interaction with water as contributors to the quaternary structure dependence of the iron-histidine bond and thus reflect on the role of that bond in the energetics of cooperative ligand binding.
mesh_terms: D000494:Allosteric Regulation; D005615:Freezing; D006418:Heme; D006441:Hemoglobin A; D006639:Histidine; D006801:Humans; D009038:Motion; D011487:Protein Conformation; D013059:Spectrum Analysis, Raman; D014867:Water
chemical_list: D014867:Water; D006418:Heme; D006639:Histidine; D006441:Hemoglobin A