Thermal-induced force release in oxyhemoglobin.
Oxygen is released to living tissues via conformational changes of hemoglobin from R-state (oxyhemoglobin) to T-state (desoxyhemoglobin). The detailed mechanism of this process is not yet fully understood. We have carried out micromechanical experiments on oxyhemoglobin crystals to determine the behavior of the Young's modulus and the internal friction for temperatures between 20 °C and 70 °C. We have found that around 49 °C oxyhemoglobin crystal samples undergo a sudden and strong increase of their Young's modulus, accompanied by a sudden decrease of the internal friction. This sudden mechanical change (and the ensuing force release) takes place in a partially unfolded state and precedes the full denaturation transition at higher temperatures. After this transformation, the hemoglobin crystals have the same mechanical properties as their initial state at room temperatures. We conjecture that it can be relevant for explaining the oxygen-releasing function of native oxyhemoglobin when the temperature is increased, e.g. due to active sport. The effect is specific for the quaternary structure of hemoglobin, and is absent for myoglobin with only one peptide sequence.
1] Institute of Physics, Academia Sinica, Nankang, Taipei 11529, Taiwan [2] Yerevan Physics Institute, Alikhanian Brothers St. 2, Yerevan 375036, Armenia.
S G
SG
Gevorkian
1] Laboratoire de Physique Statistique et Systèmes Complexes, ISMANS, 44 ave. Bartholdi, 72000 Le Mans, France [2] Yerevan Physics Institute, Alikhanian Brothers St. 2, Yerevan 375036, Armenia.
A E
AE
Allahverdyan
Institute of Fine Organic Chemistry, 26 Azatutian ave., Yerevan 0014, Armenia.
D S
DS
Gevorgyan
1] Institute of Physics, Academia Sinica, Nankang, Taipei 11529, Taiwan [2] National Center for Theoretical Sciences, National Tsing Hua University, Hsinchu 30013, Taiwan.
Chin-Kun
CK
Hu
D000465:Algorithms; D000818:Animals; D018360:Crystallography, X-Ray; D055119:Elastic Modulus; D006736:Horses; D006801:Humans; D010108:Oxyhemoglobins / Q000737:chemistry* / Q000378:metabolism; D017434:Protein Structure, Tertiary; D013696:Temperature
D010108:Oxyhemoglobins