Laser Flash Spectroscopy of Zinc/Ruthenium Myoglobins: An Investigation of Distance and Medium Effects on Photoinduced Long-Range Intraprotein Electron Transfers
An experimental investigation of the distance dependence of long-range intramolecular electron transfer in ruthenium-modified zinc myoglobins has been performed. The zinc/ruthenium-modified metalloproteins were prepared by substitution of zinc-mesoporphyrin IX diacid (ZnP) into four previously chara...
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ftcaltechdiss:oai:thesis.library.caltech.edu:11439 2023-09-05T13:23:34+02:00 Laser Flash Spectroscopy of Zinc/Ruthenium Myoglobins: An Investigation of Distance and Medium Effects on Photoinduced Long-Range Intraprotein Electron Transfers Axup, Andrew William 1987 application/pdf https://thesis.library.caltech.edu/11439/ https://thesis.library.caltech.edu/11439/2/Axup_AW_1987.pdf https://resolver.caltech.edu/CaltechTHESIS:04052019-103258317 en eng https://thesis.library.caltech.edu/11439/2/Axup_AW_1987.pdf Axup, Andrew William (1987) Laser Flash Spectroscopy of Zinc/Ruthenium Myoglobins: An Investigation of Distance and Medium Effects on Photoinduced Long-Range Intraprotein Electron Transfers. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/1a3m-hb31. https://resolver.caltech.edu/CaltechTHESIS:04052019-103258317 <https://resolver.caltech.edu/CaltechTHESIS:04052019-103258317> other Thesis NonPeerReviewed 1987 ftcaltechdiss https://doi.org/10.7907/1a3m-hb31 2023-08-14T17:29:59Z An experimental investigation of the distance dependence of long-range intramolecular electron transfer in ruthenium-modified zinc myoglobins has been performed. The zinc/ruthenium-modified metalloproteins were prepared by substitution of zinc-mesoporphyrin IX diacid (ZnP) into four previously characterized pentaammineruthenium(III) (a 5 Ru) derivatives of sperm whale myoglobin (Mb). The derivatives are a 5 Ru(His-48)Mb, a 5 Ru(His-12)Mb, a 5 Ru(His-116)Mb, and a 5 Ru(His-81)Mb. Pulsed laser excitation of the zinc myoglobin produces the long-lived and highly reducing triplet excited state ( 3 ZnP * ). Electron transfer from this triplet to the ruthenium, 3 znP * -Ru 3+ → ZnP + -Ru 2+ (ΔE° ≅ 0.8 V), was measured by time-resolved transient absorption techniques. The observed electron-transfer rates are 7.0 x 10 4 , 100, 89, and 85 s -1 for the His-48, -12, -116, and -81 derivatives, respectively, at 25°C The electron-transfer distances were evaluated using computer modelling in which rotation about the C α -C β bond of the imidazole side chain in the ruthenium-modified histidines is restricted by nonbonded repulsions with atoms at the protein surface. Recent crystallographic results for a 5 Ru(His-48)Mb indicate that the histidine has considerable rotational flexibility. The estimated accessible distances, both heme edge to inner coordination sphere ligand (e-e) and metal-to-metal (m-m), are as follows. For the His-48 derivative, the e-e range is 13.4-16.6 Å and the m-m range is 18.6-24.1 Å; His-12 ranges are 22.1-22.4 Å and 28.8-30.4 Å; His-116 ranges are 18.9-20.4 Å and 23.1-27.8 Å; and His-81 ranges are 19.0-19.4 Å and 26.3-26.9 Å. In addition, the orientation angles (θ) of the electron-transfer pathways with relation to the heme plane at a position of closest approach are 25° (His-48), 20° (His-12), 35° (His-116), and 25° (His-81). Fitting the rate data to an exponential distance dependence yields the expression k et = 8 x 10 9 exp(-β(R-4)) s -1 , where β = 1.2 Å -1 and R - 4 ≥ 0 (R is the minimum e-e distance ... Thesis Sperm whale CaltechTHESIS (California Institute of Technology |
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Open Polar |
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CaltechTHESIS (California Institute of Technology |
op_collection_id |
ftcaltechdiss |
language |
English |
description |
An experimental investigation of the distance dependence of long-range intramolecular electron transfer in ruthenium-modified zinc myoglobins has been performed. The zinc/ruthenium-modified metalloproteins were prepared by substitution of zinc-mesoporphyrin IX diacid (ZnP) into four previously characterized pentaammineruthenium(III) (a 5 Ru) derivatives of sperm whale myoglobin (Mb). The derivatives are a 5 Ru(His-48)Mb, a 5 Ru(His-12)Mb, a 5 Ru(His-116)Mb, and a 5 Ru(His-81)Mb. Pulsed laser excitation of the zinc myoglobin produces the long-lived and highly reducing triplet excited state ( 3 ZnP * ). Electron transfer from this triplet to the ruthenium, 3 znP * -Ru 3+ → ZnP + -Ru 2+ (ΔE° ≅ 0.8 V), was measured by time-resolved transient absorption techniques. The observed electron-transfer rates are 7.0 x 10 4 , 100, 89, and 85 s -1 for the His-48, -12, -116, and -81 derivatives, respectively, at 25°C The electron-transfer distances were evaluated using computer modelling in which rotation about the C α -C β bond of the imidazole side chain in the ruthenium-modified histidines is restricted by nonbonded repulsions with atoms at the protein surface. Recent crystallographic results for a 5 Ru(His-48)Mb indicate that the histidine has considerable rotational flexibility. The estimated accessible distances, both heme edge to inner coordination sphere ligand (e-e) and metal-to-metal (m-m), are as follows. For the His-48 derivative, the e-e range is 13.4-16.6 Å and the m-m range is 18.6-24.1 Å; His-12 ranges are 22.1-22.4 Å and 28.8-30.4 Å; His-116 ranges are 18.9-20.4 Å and 23.1-27.8 Å; and His-81 ranges are 19.0-19.4 Å and 26.3-26.9 Å. In addition, the orientation angles (θ) of the electron-transfer pathways with relation to the heme plane at a position of closest approach are 25° (His-48), 20° (His-12), 35° (His-116), and 25° (His-81). Fitting the rate data to an exponential distance dependence yields the expression k et = 8 x 10 9 exp(-β(R-4)) s -1 , where β = 1.2 Å -1 and R - 4 ≥ 0 (R is the minimum e-e distance ... |
format |
Thesis |
author |
Axup, Andrew William |
spellingShingle |
Axup, Andrew William Laser Flash Spectroscopy of Zinc/Ruthenium Myoglobins: An Investigation of Distance and Medium Effects on Photoinduced Long-Range Intraprotein Electron Transfers |
author_facet |
Axup, Andrew William |
author_sort |
Axup, Andrew William |
title |
Laser Flash Spectroscopy of Zinc/Ruthenium Myoglobins: An Investigation of Distance and Medium Effects on Photoinduced Long-Range Intraprotein Electron Transfers |
title_short |
Laser Flash Spectroscopy of Zinc/Ruthenium Myoglobins: An Investigation of Distance and Medium Effects on Photoinduced Long-Range Intraprotein Electron Transfers |
title_full |
Laser Flash Spectroscopy of Zinc/Ruthenium Myoglobins: An Investigation of Distance and Medium Effects on Photoinduced Long-Range Intraprotein Electron Transfers |
title_fullStr |
Laser Flash Spectroscopy of Zinc/Ruthenium Myoglobins: An Investigation of Distance and Medium Effects on Photoinduced Long-Range Intraprotein Electron Transfers |
title_full_unstemmed |
Laser Flash Spectroscopy of Zinc/Ruthenium Myoglobins: An Investigation of Distance and Medium Effects on Photoinduced Long-Range Intraprotein Electron Transfers |
title_sort |
laser flash spectroscopy of zinc/ruthenium myoglobins: an investigation of distance and medium effects on photoinduced long-range intraprotein electron transfers |
publishDate |
1987 |
url |
https://thesis.library.caltech.edu/11439/ https://thesis.library.caltech.edu/11439/2/Axup_AW_1987.pdf https://resolver.caltech.edu/CaltechTHESIS:04052019-103258317 |
genre |
Sperm whale |
genre_facet |
Sperm whale |
op_relation |
https://thesis.library.caltech.edu/11439/2/Axup_AW_1987.pdf Axup, Andrew William (1987) Laser Flash Spectroscopy of Zinc/Ruthenium Myoglobins: An Investigation of Distance and Medium Effects on Photoinduced Long-Range Intraprotein Electron Transfers. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/1a3m-hb31. https://resolver.caltech.edu/CaltechTHESIS:04052019-103258317 <https://resolver.caltech.edu/CaltechTHESIS:04052019-103258317> |
op_rights |
other |
op_doi |
https://doi.org/10.7907/1a3m-hb31 |
_version_ |
1776204160042008576 |