Transient and Time‐resolved Optical Studies of Photolyzed Carbonmonoxy Hemoglobin and Myoglobin

Ew, Findsen; Mr, Ondrias

doi:10.1111/php.1990.51.6.741

Cited by 13 publications

(11 citation statements)

References 60 publications

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“…Finally, the low photolysis yield within the 10-ns probe pulse at pH = 9.70 might result from more rapid heme-ligand recombination instead of changes in instrinsic yield. Similar behavior is seen in cytochrome c and b5 (Jongeward et al, 1988) and accounts for a large portion of the difference in net quantum yield between 02 and CO photolysis in globins (Rousseau & Friedman, 1988;Findsen & Ondrias, 1990, and references therein). The present data cannot exclude this possibility.…”

Section: Discussionmentioning

confidence: 58%

Formation and photolability of low-spin ferrous cytochrome c peroxidase at alkaline pH

Wang¹,

Boldt²,

Ondrias³

1992

Biochemistry

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The ferrous form of native cytochrome c peroxidase (CCP) is known to undergo a reversible transition when titrated over the pH range of 7.00-9.70. This transition produces a conversion from a pentacoordinate high-spin to a hexacoordinate low-spin heme active site and is clearly apparent in the heme optical absorption spectra. Here, we report the characterization of this transition and its effect upon the local heme environment using various optical spectroscopies. The formation of hexacoordinate low-spin heme is interpreted to involve the binding of His-52 at the distal site after the perturbation of the extensive H-bonded network within and around the heme pocket of CCP(II) at alkaline pH. Interestingly, CD investigations of CCP(II) in the far-UV and Soret regions indicate the dissappearance of a single high-spin species and the existence of at least two low-spin species of CCP(II) as the pH is raised above 7.90. Furthermore, transient resonance Raman experiments demonstrate that the hexacoordinate low-spin species can be photolyzed within 10-ns laser pulses, producing a species similar to the low-pH (high-spin) form of CCP(II) at alkaline pH. However, the extent of photolysis is quite pH dependent, with a maximum photodissociation yield at pH = 8.50.

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Section: Discussionmentioning

confidence: 58%

Formation and photolability of low-spin ferrous cytochrome c peroxidase at alkaline pH

Wang¹,

Boldt²,

Ondrias³

1992

Biochemistry

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“…(NO)Cat111 + fa/ -Cat111 + NO (22) The transient spectrum decays uniformly in the wavelength region studied according to first-order kinetics in the presence of excess NO. No permanent photoproduct was detected after laser photolysis of (NO)Cat111.…”

Section: «Cyr»)[no]mentioning

confidence: 99%

Photochemistry of nitric oxide adducts of water-soluble iron(III) porphyrin and ferrihemoproteins studied by nanosecond laser photolysis

Hoshino¹,

Ozawa²,

Seki³

et al. 1993

J. Am. Chem. Soc.

297

301

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Water-soluble iron( 111) porphyrin and ferrihemoproteins (methemoglobin, metmyoglobin, oxidized cytochrome c, and catalase) associate with N O to yield the nitric oxide adducts. The equilibrium constants for association of ferrihemoproteins and N O are 1 order of magnitude larger than that of the water-soluble iron(II1) porphyrin which is free from protein, suggesting that the proteins offset the forward and backward reaction rates in the equilibrium reactions. Nanosecond laser photolysis studies of the nitric oxide adducts of metmyoglobin, oxidized cytochrome c, and catalase, (NO)MblI1, (NO)CytlI1, and (NO)CatlI1, have been carried out. The transient detected after laser flash photolysis of (NO)CatlI1 is identified as Cat"'. However, the transients observed for (NO)MblI1 and (NO)CytlI1 at 50 ns after laser pulsing are ascribed to MVI,, and Cytrrl,,, respectively, with the absorption spectra different from those of uncomplexed MblI1 and Cyt"'. In particular, the absorption spectrum of Cyt1Irtr markedly differs from that of the uncomplexed Cyt"'. The species MVrrtr and Cytrllt, are found to change to MblI1 and CytlI1, respectively, within a few microseconds. The quantum yields for the photodissociation of NO from nitric oxide adducts of ferrihemoproteins are 1 order of magnitude less than that from the N O adduct of the water-soluble iron(II1) porphyrin, probably due to fast geminate recombination reaction of N O and ferrihemoprotein in a heme pocket. The photochemistry of the nitric oxide adducts of hemoproteins and water-soluble iron(I1) porphyrin is also described on the basis of laser phosolysis studies.

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“…[1][2][3][4] Even after such extensive study, controversy remains as to the factors that control this conceptually simple reaction. A clear result, however, is that the rebinding of diatomic ligands can be strongly coupled to motions of the protein.…”

Section: Introductionmentioning

confidence: 98%

“…The recombination of small diatomic ligands with the heme prosthetic group in myoglobin (Mb) following photolysis has served as a model reaction for the study of protein dynamics for many decades. − Even after such extensive study, controversy remains as to the factors that control this conceptually simple reaction. A clear result, however, is that the rebinding of diatomic ligands can be strongly coupled to motions of the protein.…”

Section: Introductionmentioning

confidence: 99%

Dependence of NO Recombination Dynamics in Horse Myoglobin on Solution Glycerol Content

et al. 1999

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The recombination dynamics of NO with horse heart myoglobin (Mb) following photolysis with a 570 nm excitation pulse were measured by time-resolved absorption with 250 fs temporal resolution. These measurements were carried out in room-temperature solutions in which the glycerol concentration was varied from 0 to 90% (w/v). The recombination of NO is nonsingle exponential in all cases, but becomes faster as the glycerol concentration is increased. The interpretation of these results is aided by a maximum entropy analysis to determine a distribution of rate processes consistent with the data. This analysis suggests that in buffer there are two dominant rate processes for NO recombination on the subnanosecond time scale, one at ≈10 ps and one at ≈200 ps. The dominant effect of increasing glycerol content is to increase the amplitude of the fast process, with no corresponding significant change in rate, and to decrease the amplitude of the slow process, but with a corresponding increase in rate. These results are consistent with a photodissociation process in which photolyzed NO partitions immediately between two distinct populations, one of which has a rapid and the other of which has a slower recombination. The rate of the rapid recombination is independent of glycerol concentration, and therefore decoupled from any protein relaxation process influenced by glycerol, while that of the slower recombination increases at higher glycerol concentration. Further, the partitioning between these two populations also depends on glycerol content, with the relative amplitude of the faster recombination process increasing as the glycerol content is increased. Interpretation of these observations in terms of ligand trajectories following photodissociation, and possible connections of these results with both infrared and crystallographic studies of photodissociated MbCO are discussed.

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Transient and Time‐resolved Optical Studies of Photolyzed Carbonmonoxy Hemoglobin and Myoglobin

Cited by 13 publications

References 60 publications

Formation and photolability of low-spin ferrous cytochrome c peroxidase at alkaline pH

Formation and photolability of low-spin ferrous cytochrome c peroxidase at alkaline pH

Photochemistry of nitric oxide adducts of water-soluble iron(III) porphyrin and ferrihemoproteins studied by nanosecond laser photolysis

Dependence of NO Recombination Dynamics in Horse Myoglobin on Solution Glycerol Content

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