Aza-crown-capped porphyrin models of myoglobin: Studies of the steric interactions of gas binding

James P. Collman; Paul C. Herrmann; Lei Fu; Todd A. Eberspacher; Michael Eubanks; Bernard Boitrel; Pascal Hayoz; Xumu Zhang; John I. Brauman; Victor W. Day

doi:10.1021/ja963945i

Aza-crown-capped porphyrin models of myoglobin: Studies of the steric interactions of gas binding

James P. Collman^*, Paul C. Herrmann, Lei Fu, Todd A. Eberspacher, Michael Eubanks, Bernard Boitrel, Pascal Hayoz, Xumu Zhang, John I. Brauman, Victor W. Day

^*Corresponding author for this work

Stanford University

Research output: Contribution to journal › Article › peer-review

72 Citations (Scopus)

Abstract

A series of myoglobin active site analogues (1-6) has been synthesized and characterized. These synthetic models differ in their cavity dimensions, and have been designed to demonstrate the effects of steric factors on O₂ and CO binding affinities. Quantitative gas titrations were employed to measure these affinities, yielding M values that are strikingly lower than those reported for hemoglobin and myoglobin. The 1,4,7-triazacyclononane-capped porphyrin 1 has about 1200 times the CO affinity but only about 10 times the O₂ affinity of the cyclam-capped porphyrin 2, suggesting a more open gas binding cavity for 1. The cavity dimensions and conformation of 2 were determined by single-crystal X-ray structural analysis of the Zn analogue 7. This paper unequivocally demonstrates that steric effects can control the ratio of O₂/CO binding constants.

Original language	English
Pages (from-to)	3481-3489
Number of pages	9
Journal	Journal of the American Chemical Society
Volume	119
Issue number	15
DOIs	https://doi.org/10.1021/ja963945i
Publication status	Published - 1997
Externally published	Yes

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title = "Aza-crown-capped porphyrin models of myoglobin: Studies of the steric interactions of gas binding",

abstract = "A series of myoglobin active site analogues (1-6) has been synthesized and characterized. These synthetic models differ in their cavity dimensions, and have been designed to demonstrate the effects of steric factors on O2 and CO binding affinities. Quantitative gas titrations were employed to measure these affinities, yielding M values that are strikingly lower than those reported for hemoglobin and myoglobin. The 1,4,7-triazacyclononane-capped porphyrin 1 has about 1200 times the CO affinity but only about 10 times the O2 affinity of the cyclam-capped porphyrin 2, suggesting a more open gas binding cavity for 1. The cavity dimensions and conformation of 2 were determined by single-crystal X-ray structural analysis of the Zn analogue 7. This paper unequivocally demonstrates that steric effects can control the ratio of O2/CO binding constants.",

author = "Collman, {James P.} and Herrmann, {Paul C.} and Lei Fu and Eberspacher, {Todd A.} and Michael Eubanks and Bernard Boitrel and Pascal Hayoz and Xumu Zhang and Brauman, {John I.} and Day, {Victor W.}",

year = "1997",

doi = "10.1021/ja963945i",

language = "English",

volume = "119",

pages = "3481--3489",

journal = "Journal of the American Chemical Society",

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T1 - Aza-crown-capped porphyrin models of myoglobin

T2 - Studies of the steric interactions of gas binding

AU - Collman, James P.

AU - Herrmann, Paul C.

AU - Fu, Lei

AU - Eberspacher, Todd A.

AU - Eubanks, Michael

AU - Boitrel, Bernard

AU - Hayoz, Pascal

AU - Zhang, Xumu

AU - Brauman, John I.

AU - Day, Victor W.

PY - 1997

Y1 - 1997

N2 - A series of myoglobin active site analogues (1-6) has been synthesized and characterized. These synthetic models differ in their cavity dimensions, and have been designed to demonstrate the effects of steric factors on O2 and CO binding affinities. Quantitative gas titrations were employed to measure these affinities, yielding M values that are strikingly lower than those reported for hemoglobin and myoglobin. The 1,4,7-triazacyclononane-capped porphyrin 1 has about 1200 times the CO affinity but only about 10 times the O2 affinity of the cyclam-capped porphyrin 2, suggesting a more open gas binding cavity for 1. The cavity dimensions and conformation of 2 were determined by single-crystal X-ray structural analysis of the Zn analogue 7. This paper unequivocally demonstrates that steric effects can control the ratio of O2/CO binding constants.

AB - A series of myoglobin active site analogues (1-6) has been synthesized and characterized. These synthetic models differ in their cavity dimensions, and have been designed to demonstrate the effects of steric factors on O2 and CO binding affinities. Quantitative gas titrations were employed to measure these affinities, yielding M values that are strikingly lower than those reported for hemoglobin and myoglobin. The 1,4,7-triazacyclononane-capped porphyrin 1 has about 1200 times the CO affinity but only about 10 times the O2 affinity of the cyclam-capped porphyrin 2, suggesting a more open gas binding cavity for 1. The cavity dimensions and conformation of 2 were determined by single-crystal X-ray structural analysis of the Zn analogue 7. This paper unequivocally demonstrates that steric effects can control the ratio of O2/CO binding constants.

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DO - 10.1021/ja963945i

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JO - Journal of the American Chemical Society

JF - Journal of the American Chemical Society

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ER -

Aza-crown-capped porphyrin models of myoglobin: Studies of the steric interactions of gas binding

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