Red‐band resonance raman spectroscopy of chlorophyll cofactors in photosynthetic proteins

Lutz, Marc

doi:10.1002/bspy.350010503

Cited by 20 publications

(51 citation statements)

References 67 publications

(22 reference statements)

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“…Spectra obtained with the two techniques show good general agreement (10,45,46,47); so it is of interest to compare the results of the present work with those from resonance Raman investigations.…”

Section: Discussionmentioning

confidence: 66%

Low frequency vibrational modes in proteins: Changes induced by point-mutations in the protein-cofactor matrix of bacterial reaction centers

Rischel

Spiedel

Ridge

et al. 1998

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

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As a step toward understanding their functional role, the low frequency vibrational motions (<300 cm ؊1 ) that are coupled to optical excitation of the primary donor bacteriochlorophyll cofactors in the reaction center from Rhodobacter sphaeroides were investigated. The pattern of hydrogen-bonding interaction between these bacteriochlorophylls and the surrounding protein was altered in several ways by mutation of single amino acids. The spectrum of low frequency vibrational modes identified by femtosecond coherence spectroscopy varied strongly between the different reaction center complexes, including between different mutants where the pattern of hydrogen bonds was the same. It is argued that these variations are primarily due to changes in the nature of the individual modes, rather than to changes in the charge distribution in the electronic states involved in the optical excitation. Pronounced effects of point mutations on the low frequency vibrational modes active in a proteincofactor system have not been reported previously. The changes in frequency observed indicate a strong involvement of the protein in these nuclear motions and demonstrate that the protein matrix can increase or decrease the f luctuations of the cofactor along specific directions.Any fundamental description of a biological process must ultimately encompass an account of small and possibly large scale changes in the nuclear geometry of the participating molecules. In particular, a central element in the determination of reaction efficiencies is the structure and accessibility of the transition state, which is the highest point on the free energy barrier that opposes changes in nuclear geometry as the system moves from reactant to product state. For proteins, atoms are most easily displaced along the ''soft'' directionsthe delocalized, low frequency modes-and the study of such motion during a reaction is therefore of particular interest.In recent years, a new aspect of low frequency motion has been revealed by the observation of coherent nuclear motion, persisting on the picosecond (ps) timescale following impulsive optical excitation, and manifested as oscillations in the transient optical properties of the protein cofactors. The discovery of this phenomenon in a variety of protein-cofactor systems, including the bacterial reaction center (RC) (1, 2), bacteriorhodopsin (3), and heme proteins (4), implies that ultrafast biological processes can occur on a timescale that is faster than vibrational relaxation (5). Therefore the possibility of coherent (in addition to thermal) motion along the reaction coordinate must be included in any complete description of a reaction. In addition, the measurement of oscillations by using femtosecond (fs) transient spectroscopy provides a new and convenient method for probing the spectrum of low frequency, nuclear vibrations that are set in motion by a physiological trigger. This study is aimed at assessing the factors that influence the character of such nuclear motions, by exploiting the possibil...

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Section: Discussionmentioning

confidence: 66%

Low frequency vibrational modes in proteins: Changes induced by point-mutations in the protein-cofactor matrix of bacterial reaction centers

Rischel

Spiedel

Ridge

et al. 1998

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

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“…It has been suggested that acquisition of SERR spectra with both red and blue excitation may facilitate complete characterization of the complicated vibrational spectra of these large pigment structures. 3, 4 We present here an application of this method which reveals good sensitivity of the technique to minor structural differences between closely related members of a family of compounds, the chl a allomers (Fig. 1).…”

Section: Introductionmentioning

confidence: 99%

Surface-enhanced resonance Raman spectroscopic identification of chlorophyll a allomers

Woolley¹,

Keely²,

Hester³

1997

J. Chem. Soc., Perkin Trans. 2

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“…Resonance Raman (RR) spectroscopy provides a convenient and direct method for probing both the ground- and excited-state properties of chromophores via the characteristics of the RR frequencies and intensities, respectively . To date, RR spectroscopic methods have been used to investigate a variety of photosynthetic pigments, both in isolated form and in protein systems . The majority of these studies have focused on the high-frequency (1000−1750 cm -1 ) region of the spectrum which contains bands due to ring-skeletal and carbonyl stretching vibrations of the macrocycle. − These vibrational data have been used to assess the conformation of the (bacterio)chlorophyll rings, the ligation state of the Mg(II) ion, and the extent of hydrogen bonding to the carbonyl substituents on the rings.…”

Section: Introductionmentioning

confidence: 99%

Q_y-Excitation Resonance Raman Spectra of Chlorophyll a and Related Complexes. Normal Mode Characteristics of the Low-Frequency Vibrations

1997

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Q y -excitation resonance Raman (RR) spectra are reported for film aggregates of chlorophyll (Chl) a and a series of related complexes. The latter include Mg(II) octaethylporphyrin (MgOEP), Mg(II) trans-octaethylchlorin (MgOEC), methyl-9-desoxomesopyrochlorophyllide (DMPChl) a, and methylpyrochlorophyllide (MPChl) a. These complexes represent a series in which the structural complexities of Chl a (saturated pyrrole ring, isocyclic ring, C9-keto group, C2-vinyl group, and C10-carbomethoxy group) are systematically added to the basic tetrapyrrole architecture. On the basis of comparison of the RR scattering characteristics of the different complexes and the predictions of semiempirical normal coordinate calculations, a self-consistent set of vibrational assignments has been developed for all the RR active modes in the low-frequency regime (100−1000 cm-1). The studies indicate that the low-frequency vibrations encompass a diverse set of motions that include both the ring skeleton and peripheral substituent groups. However, modes in the very low-frequency regime (<250 cm-1) are primarily due to deformations of the substituent groups. Collectively, the normal mode characteristics of Chl a and the other Mg(II) complexes provide insights into the nature of the vibrational modes that are coupled to the photophysically important, lowest energy excited states of natural photosynthetic assemblies.

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Red‐band resonance raman spectroscopy of chlorophyll cofactors in photosynthetic proteins

Cited by 20 publications

References 67 publications

Low frequency vibrational modes in proteins: Changes induced by point-mutations in the protein-cofactor matrix of bacterial reaction centers

Low frequency vibrational modes in proteins: Changes induced by point-mutations in the protein-cofactor matrix of bacterial reaction centers

Surface-enhanced resonance Raman spectroscopic identification of chlorophyll a allomers

Q_y-Excitation Resonance Raman Spectra of Chlorophyll a and Related Complexes. Normal Mode Characteristics of the Low-Frequency Vibrations

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Red‐band resonance raman spectroscopy of chlorophyll cofactors in photosynthetic proteins

Cited by 20 publications

References 67 publications

Low frequency vibrational modes in proteins: Changes induced by point-mutations in the protein-cofactor matrix of bacterial reaction centers

Low frequency vibrational modes in proteins: Changes induced by point-mutations in the protein-cofactor matrix of bacterial reaction centers

Surface-enhanced resonance Raman spectroscopic identification of chlorophyll a allomers

Qy-Excitation Resonance Raman Spectra of Chlorophyll a and Related Complexes. Normal Mode Characteristics of the Low-Frequency Vibrations

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Q_y-Excitation Resonance Raman Spectra of Chlorophyll a and Related Complexes. Normal Mode Characteristics of the Low-Frequency Vibrations