Measurement of magnetic circular dichroism (MCD) on a nanosecond timescale

Goldbeck, Robert A.; Dawes, Timothy D.; Milder, Steven J.; Lewis, James W.; Kliger, David S.

doi:10.1016/s0009-2614(89)87228-8

Cited by 18 publications

(23 citation statements)

References 13 publications

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“…In a parallel kinetics study (6 By using TRIR, we have determined kL1 to be 4.7 x 105 so1 (1). These results reveal that CuB, in addition to its established electron transfer role, functions as a "ligand shuttle" in transporting CO (and plausibly other exogenous ligands including 02) to and from the heme of cyt a3.…”

mentioning

confidence: 81%

Nature and functional implications of the cytochrome a3 transients after photodissociation of CO-cytochrome oxidase.

Woodruff

Einarsdóttir

Dyer

et al. 1991

Proc. Natl. Acad. Sci. U.S.A.

114

117

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Time-resolved electronic absorption, infrared, resonance Raman, and magnetic circular dichroism spectroscopies are applied to characterization of the intermediate that is formed within 20 ps after photodissociation of CO from cytochrome a3 in reduced cytochrome oxidase. This intermediate decays with the same half-life (1l is) as the postphotodissociation Cu'-CO species previously observed by time-resolved infrared. The transient UV/visible spectra, kinetics, infrared, and Raman evidence suggest that an endogenous ligand is transferred from CUB to Fe,3 when CO binds to CUB, forming a cytochrome a3 species with axial ligation that differs from the reduced unliganded enzyme. The timeresolved magnetic circular dichroism results suggest that this transient is high-spin and, therefore, five-coordinate. Thus we infer that the ligand from CUB binds on the distal side of cytochrome a3 and displaces the proximal histidine imidazole. This remarkable mechanistic feature is an additional aspect of the previously proposed "ligand-shuttle" activity of the CuB/Fe,3 pair. We speculate as to the identity ofthe ligand that is transferred between CUB and Fe,13 and suggest that the ligand shuttle may play a functional role in redox-linked proton translocation by the enzyme.In a recent time-resolved infrared (TRIR) study (1) of the events after photodissociation of CO from cytochrome (cyt) a3 of reduced beef heart cytochrome oxidase (CcO), we reported conclusive evidence that photodissociated CO binds quantitatively to CuB at room temperature prior to equilibrating with solution. In a parallel kinetics study (6.E., P. M.

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mentioning

confidence: 81%

Nature and functional implications of the cytochrome a3 transients after photodissociation of CO-cytochrome oxidase.

Woodruff

Einarsdóttir

Dyer

et al. 1991

Proc. Natl. Acad. Sci. U.S.A.

114

117

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“…Such time resolution was achieved in the 1980s when the TRCD technique advanced to measurements on the nanosecond and picosecond time scales [33, 34]. Although initially designed with single wavelength detection [33], nanosecond TRCD spectroscopy in this laboratory has evolved to include multichannel detection [35], other nanosecond polarization methods (TRMCD [16], ultrasensitive time-resolved LD (TRLD) [36], time-resolved optical rotatory dispersion (ORD) (TRORD) [37] and time-resolved magnetic optical rotatory dispersion (MORD) (TRMORD) [38, 39]), extension of the measurements from the visible into the far-UV region [40], faster time resolution (~10 ns) [41], and most recently, it has been coupled with a T-jump trigger [42]. Thus, since the mid-1980s, most submillisecond polarization experiments on biomolecules have been performed with the nanosecond time-resolved methods that were developed in this laboratory.…”

Section: Circular Dichroism a Short Time-resolved Historymentioning

confidence: 99%

“…The power of the CD method is extended with the addition of a magnet to the TRCD configuration [15]. This time-resolved MCD (TRMCD) method is a sensitive probe of structural features that perturb the electronic states of an MCD active chromophore [16]. TRMCD spectroscopy has been applied to the studies of the axial ligation, spin, and oxidation states of the heme iron atom in functional studies of hemoglobin, myoglobin, and cytochrome c oxidase [17–20] and in folding studies of cytochrome c [15, 21], and more recently has been used to probe the dynamics of the tryptophan residue in hemoglobin [22].…”

Section: Introductionmentioning

confidence: 99%

Nanosecond time-resolved polarization spectroscopies: Tools for probing protein reaction mechanisms

Chen

Goldbeck

Kliger

2010

Methods

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Polarization methods, introduced in the 1800's, offered one of the earliest ways to examine protein structure. Since then, many other structure-sensitive probes have been developed, but circular dichroism (CD) remains a powerful technique because of its versatility and the specificity of protein structural information that can be explored. With improvements in time-resolution, from millisecond to picosecond CD measurements, it has proven to be an important tool for studying the mechanism of folding and function in many biomolecules. For example, nanosecond time-resolved CD (TRCD) studies of the sub-microsecond events of reduced cytochrome c folding have provided direct experimental evidence of kinetic heterogeneity, which is an inherent property of the diffusional nature of early folding dynamics on the energy landscape. In addition, TRCD has been applied to the study of many biochemical processes, such as ligand rebinding in hemoglobin and myoglobin and signaling state formation in photoactive yellow protein and prototropin 1 LOV2. The basic approach to TRCD has also been extended to include a repertoire of nanosecond polarization spectroscopies: optical rotatory dispersion (ORD), magnetic CD and ORD, and linear dichroism. This article will discuss the details of the polarization methods used in this laboratory, as well as the coupling of timeresolved ORD with the temperature-jump trigger so that protein folding can be studied in a larger number of proteins.

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“…For example, in heme proteins such structural features include the axial ligation, spin, and oxidation states of the heme iron atom, all of which can strongly affect the MCD of the heme spectral bands. Since the first nanosecond time-resolved MCD (TRMCD) measurements were reported for the lowest excited triplet state of zinc tetraphenylporphine [19], the TRMCD method has been applied largely to the study of photodissociation intermediates of heme protein-ligand complexes (e.g., cytochrome aa 3 , cytochrome ba 3 , cytochrome c 3 , myoglobin and hemoglobin) and, more recently, to the protein folding problem in cytochrome c [20, 21]. In heme proteins, the MCD spectra in the Soret and visible regions are particularly sensitive to the oxidation and ligation state of the heme iron.…”

Section: Nanosecond Optical Spectroscopymentioning

confidence: 99%

Probing Early Events in Ferrous Cytochrome c Folding with Time- Resolved Natural and Magnetic Circular Dichroism Spectroscopies.

Chen¹,

Goldbeck²,

Kliger³

2009

CPPS

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Measurement of magnetic circular dichroism (MCD) on a nanosecond timescale

Cited by 18 publications

References 13 publications

Nature and functional implications of the cytochrome a3 transients after photodissociation of CO-cytochrome oxidase.

Nature and functional implications of the cytochrome a3 transients after photodissociation of CO-cytochrome oxidase.

Nanosecond time-resolved polarization spectroscopies: Tools for probing protein reaction mechanisms

Probing Early Events in Ferrous Cytochrome c Folding with Time- Resolved Natural and Magnetic Circular Dichroism Spectroscopies.

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