Hemoglobin senses body temperature.
When aspirating human red blood cells (RBCs) into 1.3 mum pipettes (DeltaP = -2.3 kPa), a transition from blocking the pipette below a critical temperature T(c) = 36.3 +/- 0.3 degrees C to passing it above the T(c) occurred (micropipette passage transition). With a 1.1 mum pipette no passage was seen which enabled RBC volume measurements also above T(c). With increasing temperature RBCs lost volume significantly faster below than above a T(c) = 36.4 +/- 0.7 (volume transition). Colloid osmotic pressure (COP) measurements of RBCs in autologous plasma (25 degrees C < or = T < or = 39.5 degrees C) showed a T (c) at 37.1 +/- 0.2 degrees C above which the COP rapidly decreased (COP transition). In NMR T(1)-relaxation time measurements, the T(1) of RBCs in autologous plasma changed from a linear (r = 0.99) increment below T(c) = 37 +/- 1 degrees C at a rate of 0.023 s/K into zero slope above T(c) (RBC T(1) transition).


CONCLUSIONS
An amorphous hemoglobin-water gel formed in the spherical trail, the residual partial sphere of the aspirated RBC. At T(c), a sudden fluidization of the gel occurs. All changes mentioned above happen at a distinct T(c) close to body temperature. The T(c) is moved +0.8 degrees C to higher temperatures when a D(2)O buffer is used. We suggest a mechanism similar to a "glass transition" or a "colloidal phase transition". At T(c), the stabilizing Hb bound water molecules reach a threshold number enabling a partial Hb unfolding. Thus, Hb senses body temperature which must be inscribed in the primary structure of hemoglobin and possibly other proteins.
Artmann
G M
GM
Division Juelich, Aachen University of Applied Sciences, Juelich, Germany. artmann@fh-aachen.de
Digel
Ilya
I
Zerlin
K F
KF
Maggakis-Kelemen
Ch
Ch
Linder
Pt
P
Porst
D
D
Kayser
P
P
Stadler
A M
AM
Dikta
G
G
Temiz Artmann
A
A
D001831:Body Temperature; D004911:Erythrocyte Volume; D006454:Hemoglobins / Q000737:chemistry* / Q000378:metabolism*; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D009997:Osmotic Pressure; D044367:Phase Transition; D013696:Temperature; D014867:Water / Q000378:metabolism
D006454:Hemoglobins; D014867:Water