Hemoglobin's cooperativity
Hemoglobin's cooperativity means that in one molecule of deoxyhemoglobin with 4 heme mechanisms,
after one oxygen molecule coordinates to one molecule of deoxyhemoglobin, the reaction rate of the next oxygen molecule accelerates,
and the chain accelerations of the reaction rate continue untill four oxygen molecules coordinate,
and after one oxygen molecule dissociates from one molecule of oxyhemoglobin,
the reaction rate of the next oxygen molecule accelerates,
and the chain accelerations of the reaction rate continue untill four oxygen molecules dissociate.
Great expense and time are consumed to study interesting hemoglobin's cooperativity.
There is a theory that the conformational change that occurs between the planarity and non-planarity of the polyphyllin ring becomes an mechanism of informational transmission .
In addition, a model of concerted all-or-none in which symmetry is conserved has been suggested.
Since the Gibbs energy value is a quantity of state, it will be constant regardless of the route by choosing the state of the beginning and the state of the end.
Still, hemoglobin's cooperativity is a concept that includes intermediates, so intermediates on the reaction path should be discussed.
Thermodynamics dominance and kinetic dominance of chemical reactions do not always coincide.
Since the redox reactions of hemoglobin are extremely similar reactions including its intermediates, their relationship of dominances has been presumed to be strongly correlated.
In other words, it is possileto predict the reaction rate dominance relationship from the thermodynamic dominance relationship.
The hemoglobin's cooperativity that appears as a result of reaction rate dominance is estemated from the point of view of thermodynamics dominance.
See fig-7.
Read the colored area from top to bottom.
The longer it is in the vertical direction, the greater the decrease in Gibbs energy value.
The intermediates that are lower parts of the colored area contribute significantly to the reduction of Gibbs energy value.
It's comprehensible that no sooner has one oxygen molecule begun to react than four oxygen molecules react in both the capillaries of the alveoli and the ends of tssues of the body.
All figures show relative relationships.
Please note that they don't have any meanings as absolute values.
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Reference:
Physical Chemistry for the Bioscience Written by Raymond Chang Translated by Iwasawa Yasuhiro, Kitagawa Teizou, Hamaguchi Hiroo TOKYOKAGAKUDOJIN Co., Ltd.
ENTROPY AND THE SECOND LAW Written by ARIEH BEN-NAIM Translated by Ono Yoshiyuki Maruzen-publishing Co.,Lid
Direct observation of ligand binding processes to hemoglobin
RIKEN Japan's flagship institute for natural science research.
Adachi Shinnichi Jou Noritsugu
https://www.riken.jp/medialibrary/riken/pr/press/2003/20030609_1/20030609_1.pdf
Elucidation of the cooperative oxygen binding function of hemoglobin by heme electron theory
Yamamoto Yasuhiko(Tsukuba University) Tai Hulin(Tsukuba University)
https://core.ac.uk/download/pdf/56655512.pdf
Mechanism of heme-heme interaction of hemoglobin
Morimoto Hideki (Osaka University) Imai Kiyohiro (Osaka University)
Study of the mechanism of cooperarive effect of hemoglobin by protein engineering
Contribution of Specific Hydroen Bonds in Fouth-Order Structural Transtion
Ishimori Koichiro, Morishima Akira, Imai Kiyohiro, Fushitani Kenzo, Miyazaki Gentaro, Wada Yoshinao, Shin D, Tame J, Pegnier J, Nagai K
Kyoto University, Osaka University, Osaka Prefectural Maternal and Child Medical Center, MRC.Lab. of Mol. Biol.
https://www.jstage.jst.go.jp/article/biophys1961/29/supplement/29_supplement_S45/_pdf
https://www.jstage.jst.go.jp/article/biophys/41/2/41_2_74/_pdf/-char/ja
