TY - JOUR
T1 - The molecular mechanism of the temperature enhancement of proton magnetic relaxation rates in methaemoprotein solutions
AU - Vuk-Pavlović, S.
AU - Benko, B.
AU - maričić, S.
N1 - Funding Information:
This work was carried out under the FL480 con- tract No. 02-004-l between the N.I.H. (USA) and The Institute of Biology, University of Zagreb, with the partial support of the Research Fund of the S.R. Croatia. B.B. and S-V.-P thank the latter Fund and the Institute of Biology for postgraduate scholarships. The authors are indebted to Drs. R. Huber and H. Formanek for the invaluable donation of fine single crystals of Chironomus thummi haemoglobin. We are grateful to Dr. G. Lahajnar for his critical remarks at a stage in this study, which prompted our experiments with different marker molecules. We thank Mrs. V_ BraEika for her continuous, excellent technical cooperation, and Mrs. L. Tomi&, MSc., for recording the high resotution control spectra, at the Institute “Rudjer BoSkoviC’, Zagreb, and Dr. D. &rman, Medical Faculty, University of Zagreb, for allowing us to use his Iaboratory for liophyliza-tion.
PY - 1974/12
Y1 - 1974/12
N2 - The mechanism of water exchange between the haem-pocket and bulk solvent in aqueous methaemopiotein solutions was firmly substantiated by using the aliphatic protons of certain lower alcohols in an otherwise deuterated solution for measuring the incremental relaxation rates resulting from their magnetic interaction with the haem-iron. The fast-exchange condition was established for solutions of horse fluorometmyoglobin, human A fluoromethaemoglobin and Chironomus thummi aquomethaemoglobin. The distances between the exchangeable protons and the haem-iron obtained from these PMR measurements concur with the presence of the fluoride ion, while for Chironomus aquomethaemoglobin this distance is also much larger than that resulting from the location of the 6th site Water molecule. The latter finding is the first clear-cut evidence that the exchanging protons belong to the next neighbour water molecule, a previously advanced hypothesis. The exchanging water molecule may thus serve as a natural probe for comparing the haem-pocket conformational state(s) under different conditions or in various haemoproteins.
AB - The mechanism of water exchange between the haem-pocket and bulk solvent in aqueous methaemopiotein solutions was firmly substantiated by using the aliphatic protons of certain lower alcohols in an otherwise deuterated solution for measuring the incremental relaxation rates resulting from their magnetic interaction with the haem-iron. The fast-exchange condition was established for solutions of horse fluorometmyoglobin, human A fluoromethaemoglobin and Chironomus thummi aquomethaemoglobin. The distances between the exchangeable protons and the haem-iron obtained from these PMR measurements concur with the presence of the fluoride ion, while for Chironomus aquomethaemoglobin this distance is also much larger than that resulting from the location of the 6th site Water molecule. The latter finding is the first clear-cut evidence that the exchanging protons belong to the next neighbour water molecule, a previously advanced hypothesis. The exchanging water molecule may thus serve as a natural probe for comparing the haem-pocket conformational state(s) under different conditions or in various haemoproteins.
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U2 - 10.1016/0301-4622(74)80063-3
DO - 10.1016/0301-4622(74)80063-3
M3 - Article
C2 - 4441599
AN - SCOPUS:0016272864
VL - 2
SP - 359
EP - 368
JO - Biophysical Chemistry
JF - Biophysical Chemistry
SN - 0301-4622
IS - 4
ER -