Vibrational Relaxation of the CO Stretch Vibration in Hemoglobin-CO, Myoglobin-CO, and Protoheme-CO

Owrutsky, Jeffrey C.; Li, M.; Locke, B.; Hochstrasser, Robin M.

doi:10.1021/j100013a064

Cited by 80 publications

(86 citation statements)

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“…1, the difference between two consecutive transitions, vϩ2,vϩ1 Ϫ vϩ1,v ϭ Ϫ2 e 0 , is equal to Ϫ25 cm Ϫ1 , in good agreement with the value previously measured in the perturbative regime on the transition v ϭ 1 3 v ϭ 2 using either pump-probe spectroscopy (13) or vibrational echo beats (14). This anharmonicity corresponds to e Ϸ 0.63%.…”

Section: Resultssupporting

confidence: 89%

Coherent vibrational climbing in carboxyhemoglobin

Ventalon

Fraser

Vos

et al. 2004

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

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We demonstrate vibrational climbing in the CO stretch of carboxyhemoglobin pumped by midinfrared chirped ultrashort pulses. By use of spectrally resolved pump-probe measurements, we directly observed the induced absorption lines caused by excited vibrational populations up to v ‫؍‬ 6. In some cases, we also observed stimulated emission, providing direct evidence of vibrational population inversion. This study provides important spectroscopic parameters on the CO stretch in the strong-field regime, such as transition frequencies and dephasing times up to the v ‫؍‬ 6 to v ‫؍‬ 7 vibrational transition. We measured equally spaced vibrational transitions, in agreement with the energy levels of a Morse potential up to v ‫؍‬ 6. It is interesting that the integral of the differential absorption spectra was observed to deviate far from zero, in contrast to what one would expect from a simple onedimensional Morse model assuming a linear dependence of dipole moment with bond length.T he recent availability of ultrashort and intense midinfrared pulses in a compact setup (1) provides a convenient means for controlling the nuclear motion of molecules (2). With infrared pulses, only vibrational transitions are addressed while the molecule remains in its electronic ground state during the entire interaction. This makes such an approach particularly suited to complex systems such as proteins. Another fascinating possibility opened up by infrared vibrational control is the prospect of exploring the potential energy surface far from the harmonic region up to the transition state of intraprotein reactions.Coherent vibrational climbing consists of exciting a molecular vibration with an ultrashort midinfrared pulse, the broadband spectrum of which encompasses several vibrational transitions of the molecule. Indeed, these transition frequencies become smaller and smaller while climbing the ladder because of the molecular anharmonicity. Therefore, the climbing efficiency can be increased dramatically when using a negatively chirped pulse so that its high-frequency components, resonant with the lower transitions of the ladder, precede its low-frequency components, resonant with the upper transitions of the ladder. Coherent vibrational climbing can be viewed also as a rapid adiabatic passage leading to efficient excitation of the upper vibrational states, with an efficiency that in theory can be close to 100% because of the coherent nature of the interaction. Vibrational climbing has been demonstrated in small molecules, such as W(CO) 6 (3-5), NO (6), CO adsorbed on a Ru (001) surface (7), Cr(CO) 6 (8), Mo(CO) 6 (5), Fe(CO) 5 (5), and CH 2 N 2 (9). In this article, we report on the demonstration of coherent vibrational climbing in a biological system, carboxyhemoglobin (HbCO). This system was chosen rather than carboxymyoglobin, in which different CO-bound configurations result in an inhomogeneous broadening of the absorption line (10). Experimental MethodsThe 800-nm pulses produced by a titanium͞sapphire regenerative amplifier (Hurrican...

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Section: Resultssupporting

confidence: 89%

Coherent vibrational climbing in carboxyhemoglobin

Ventalon

Fraser

Vos

et al. 2004

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

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“…Interaction with the solvent also influences the vibrational cooling rate, although to a lesser extent. [13] For MbCO a two-stage cooling process was predicted, with an initial fast cooling rate (decay constant 1-4 ps) that was found to be in good agreement with experimental values (time constant 2 ps). [8] The subsequent, slower cooling phase consists of two sub-components, a faster component with time constant 7.5 ps, followed by a slower component with time constant 20 ps.…”

Section: Structural Origin Of Spectroscopic Substatessupporting

confidence: 74%

“…Infrared pump-probe measurements of solvated MbCO, HbCO and a protoheme system find ultrafast (picosecond timescale) cooling rates for the vibrationally excited CO ligand. [13,14] The CO relaxation time of MbCO was found to be T 1 = 17 ps, significantly faster than is typical for metal carbonyls [16] such as W(CO) 6 in CCl 4 (T 1 = 800 ±200 ps). The relaxation time decreases with molecular complexity, as a result of the increased number of internal vibrational modes available for coupling.…”

Section: Structural Origin Of Spectroscopic Substatesmentioning

confidence: 86%

“…Most commonly used force fields are based on harmonic functions for bonded interactions (bonds r and valence angles q) and periodic functions for torsions f to describe the total energy as a function of geometry. [12] A number of studies analyzing the process of heme and CO ligand cooling, [4,5,8,13,14] as well as assigning the key vibrational modes of Fe in the MbCO vibrational spectrum [15] have been carried out. For an overview of the system see Fig.…”

Section: Structural Origin Of Spectroscopic Substatesmentioning

confidence: 99%

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Computational Spectroscopy and Reaction Dynamics

Cazade

Lütz²,

Lee³

et al. 2011

Chimia

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Physico- and bio-chemical processes on the femto- to picosecond time scale are ideally suited to be investigated with all-atom simulations. They include, amongst others, vibrational relaxation, ligand migration in sterically demanding environments (proteins, ices), or vibrational spectra. By comparing with experimental data, the results can be used to obtain an understanding of the mechanisms underlying the observations. Furthermore, most of these processes are sensitive to the intermolecular interactions. Therefore, detailed refinement of such interaction potentials is possible. Keywords: Computational spectroscopy · Molecular dynamics simulations · Reaction dynamicsThe classification of fast and ultrafast time scales in atoms and molecules depends to some extent on the process and property considered. For example, the electronic degrees of freedom change on considerably more rapid time scales than the nuclear motions. This is the basis of the Born-Oppenheimer approximation which is valid in many cases. In proteins, on the other hand, vibrations are much more rapid than changes in the secondary structure. Typical time scales for electronic motion in molecules are attoseconds, whereas vibrations are associated with femto-and pico-second time scales. In the following, ultrafast time scales in molecular systems -which are at the focus of the NCCR Molecular and Ultrafast Science and Technology (MUST) -will be associated with atto-to picosecond processes.Understanding ultrafast processes in molecular systems requires multi-faceted approaches, including experiment, theory and computation. A typical example is the vibrational relaxation of a solvated diatomic molecule, e.g. cyanide (CN − ) in water. [1,2] Although time scales of vibrational relaxation can be reliably measured using modern laser techniques, understanding the relaxation mechanism in molecular detail is much more difficult as it includes coupling and energy transfer to solvent modes. Another example is allostery which is the regulation of a protein by binding a small molecule at the allosteric site. An allosteric activator will enhance the activity of the protein. The most widely known but still incompletely understood allosteric protein is hemoglobin. Here, four binding sites for the ligand (O 2 ) exist. Binding of the first O 2 molecule increases the protein's affinity for binding the second O 2 molecule, etc. However, the molecular details underlying the enhanced affinity for subsequent O 2 ligands is still unexplained. Finally, one purpose of high-resolution spectroscopy is to understand the bonding pattern and geometrical details of a molecule by recording and analyzing spectroscopic signatures. As the size of the molecule grows, directly determining the structure of the molecule from the spectroscopic data becomes increasingly difficult. Even more difficult is the situation in proteins where spectroscopic features of small probe molecules such as CO or NO can be recorded but the splitting patterns of the vibrational spectra are difficult ...

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“…In that study, both chemical bonding and surrounding solvent were found to influence the vibrational relaxation time of the carbonyl. In addition to this seminal work, there have been several experimental probes of CO relaxation when bound to model heme compounds and heme proteins (9)(10)(11).…”

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confidence: 99%

Vibrational population relaxation of carbon monoxide in the heme pocket of photolyzed carbonmonoxy myoglobin: Comparison of time-resolved mid-IR absorbance experiments and molecular dynamics simulations

Sagnella

Straub

Jackson

et al. 1999

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

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The vibrational energy relaxation of carbon monoxide in the heme pocket of sperm whale myoglobin was studied by using molecular dynamics simulation and normal mode analysis methods. Molecular dynamics trajectories of solvated myoglobin were run at 300 K for both the ␦-and -tautomers of the distal His-64. Vibrational population relaxation times of 335 ؎ 115 ps for the ␦-tautomer and 640 ؎ 185 ps for the -tautomer were estimated by using the Landau-Teller model. Normal mode analysis was used to identify those protein residues that act as the primary ''doorway'' modes in the vibrational relaxation of the oscillator. Although the CO relaxation rates in both the -and ␦-tautomers are similar in magnitude, the simulations predict that the vibrational relaxation of the CO is faster in the ␦-tautomer with the distal His playing an important role in the energy relaxation mechanism. Time-resolved mid-IR absorbance measurements were performed on photolyzed carbonmonoxy hemoglobin (Hb 13 CO). From these measurements, a T1 time of 600 ؎ 150 ps was determined. The simulation and experimental estimates are compared and discussed. Since the pioneering efforts of Landau and Teller (1), the problem of vibrational energy redistribution has attracted much theoretical attention (2-6). With the advent of ultrafast time-resolved IR spectroscopy, there is renewed interest in this problem as researchers can now probe directly the lifetimes of specific vibrational modes and, therefore, explore mechanisms of vibrational relaxation (7). In particular, the vibrational relaxation of metal carbonyl compounds has received considerable attention with CO population relaxation times (T 1 ) found to range from the picosecond to nanosecond time scales, depending on the metal carbonyl and its surroundings (8). In that study, both chemical bonding and surrounding solvent were found to influence the vibrational relaxation time of the carbonyl. In addition to this seminal work, there have been several experimental probes of CO relaxation when bound to model heme compounds and heme proteins (9-11).The vibrational relaxation of bound CO in heme proteins was found to be very fast (Ϸ20 ps) compared to other CO ligated compounds. In addition, Fayer and coworkers found that (i) the T 1 population relaxation time for the carbonyl ligand stretch is largely independent of temperature from 20 to 300 K (12); (ii) the vibrational lifetimes vary among different vibrational substates of the same protein (13); (iii) changes in the vibrational lifetime of bound CO are highly correlated with a change in the vibrational frequency of CO (13); and (iv) intermolecular transfer of vibrational energy is relatively unimportant in the relaxation process of bound CO (13).Vibrational relaxation tends to be more efficient through strong covalent interactions, yet there is only one such interaction between the CO and the heme. To explain the fast relaxation of bound CO in heme proteins, it has been suggested that the manifold of vibrational states within the heme is responsible.The...

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Vibrational Relaxation of the CO Stretch Vibration in Hemoglobin-CO, Myoglobin-CO, and Protoheme-CO

Cited by 80 publications

References 3 publications

Coherent vibrational climbing in carboxyhemoglobin

Coherent vibrational climbing in carboxyhemoglobin

Computational Spectroscopy and Reaction Dynamics

Vibrational population relaxation of carbon monoxide in the heme pocket of photolyzed carbonmonoxy myoglobin: Comparison of time-resolved mid-IR absorbance experiments and molecular dynamics simulations

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