A comparative pressure tuning hole burning study of protoporphyrin IX in myoglobin and in a glassy host

Gafert, J.; Friedrich, J.; Parak, F.

doi:10.1063/1.465210

Cited by 29 publications

(29 citation statements)

References 40 publications

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“…Hence, the chromophore is indeed a probe of the protein. This is an important statement: it implies, for instance, that inhomogeneous line broadening in chromoproteins is due to conformational substates; it confirms in a direct way that the properties measured in optical experiments-for instance, the compressibility (28)(29)(30) hAv = -fAi0E.…”

mentioning

confidence: 67%

Stark-effect experiments on photochemical holes in chromoproteins: protoporphyrin IX-substituted myoglobin.

Gafert¹,

Friedrich²,

Parak³

1995

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

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We performed comparative Stark-effect experiments on spectral holes in a protein and a glass sample. The protein was protoporphyrin IX-substituted myoglobin in a glycerol/water solvent. The glass sample was a protoporphyrin IX-doped mixture of dimethylformamide/glycerol. As expected, in both cases the spectral holes varied linearly with the electric field. Yet, whereas in the protein the holes showed a clear splitting, they showed no splitting in the glass sample, irrespective of the chosen polarization of the laser. In both samples the hole broadened in the applied field. The magnitude of the broadening was about the same in both cases. The following conclusions were drawn. The absence of a splitting in the glass signals an effective global inversion symmetry of the chromophore, despite its low symmetry group. The dipole moment changes are random. In the protein the inversion symmetry is broken through the spatial correlation of the protein building blocks, leading to a molecular frame-fixed dipole moment difference and, hence, to the observed splitting. Despite these symmetry-breaking properties, the local structural randomness is of the same magnitude in the glass and in the protein, as is obvious from the broadening. The distinct difference in the Stark pattern shows that the range of the relevant chromophore interactions is confined to typical dimensions of the protein.The characterization of the solid state of proteins is not straightforward. Proteins do not fit into the usual categories of solid-state phases. They have many "in-between" properties. At sufficiently high temperatures, say above 200 K, they show a behavior in between those of liquids and crystals (1-10). At sufficiently low temperatures their properties are in between those of crystals and glasses. For instance, their specific heat at low temperature is glass-like (11,12), their dielectric as well as ultra-sound absorption is glass-like (11), and many of their optical as well as their Mossbauer properties are glass-like (2, 4, 5, 13-18). On the other hand, their x-ray diffraction pattern is well resolved and crystal-like (19). Yet, even the x-ray diffraction reveals glass-like properties when the DebyeWaller factor is analyzed (20, 21): the mean-square displacement (x2) averaged over the atoms of an amino acid residue varies along the backbone and, as the absolute temperature goes to zero, shows large deviations from the usual zero-point vibrational amplitudes. These findings show that there is an additional structural uncertainty in the positions of the protein building blocks which arises from a broad distribution of conformational substructures.In this paper we will show by using hole-burning Stark spectroscopy (22-27) that, on the one hand, the randomness in the structure of a protein is comparable to the randomness of a glass. Yet, on the other hand, there is a high spatial correlation in the protein which leads to a very specific Stark pattern. From this specific pattern we will draw an important conclusion as to the range of t...

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confidence: 67%

Stark-effect experiments on photochemical holes in chromoproteins: protoporphyrin IX-substituted myoglobin.

Gafert¹,

Friedrich²,

Parak³

1995

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

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“…With eq 4 it is possible to measure κ by a purely optical experiment: [12][13][14][15][16][17] As S p /∆p is plotted as a function of burn frequency ν b , one gets a straight line with slope 2κ. 32 As to the broadening of the holes under pressure, it arises from the fact that in disordered solids such as glasses, polymers, and also proteins, the probe lattice configurations are highly degenerate.…”

Section: Introductionmentioning

confidence: 99%

Hole-Burning Spectroscopy of Proteins in External Fields: Human Serum Albumin Complexed with the Hypericinate Ion

Köhler¹,

Gafert²,

Friedrich³

et al. 1996

J. Phys. Chem.

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We investigated human serum albumin complexed with the hypericinate ion by using optical hole-burning techniques. The response of the burned-in holes to external pressure variations and electric fields was measured as a function of burn frequency within the inhomogeneous band. The results for the protein-dye complex were compared with the respective behavior of the dye in a host glass. In addition, the spectral properties of the serum albumin hypericinate complex in an electric field were compared with the respective properties of protoporphyrin substituted myoglobin. On the basis of our results we concluded that there must be two stereoisomers with a relative weight of about 50%. Further, the binding site in human serum albumin seems to be quite shallow. The dye is not shielded from the host glass, contrary to the respective behavior of protoporphyrin-substituted myoglobin.

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“…In the present case, the interaction between a polar solute and a polar solvent leads to additional ''electrostatic'' solvent shifts of dipolar nature. 12,21 This type of solvent shift, which may be red-or blue-shift, nevertheless results in the same dependence in the bulk density as the dispersive shift. Also the shift of spectral holes under pressure ͑up to 2.50 MPa͒ may be accounted for by solvent shift theory.…”

Section: Discussionmentioning

confidence: 90%

“…Also the shift of spectral holes under pressure ͑up to 2.50 MPa͒ may be accounted for by solvent shift theory. 21,22 The linear shift of a J-band under pressure may be explained simplistically by dye-to-dye distance changes in the aggregate and, hence, changes of dipole-dipole coupling of the London force type. Enhancement of dipolar interaction under pressure is a most plausible scenario which leads to a linear dependence of redshift with P. Indeed, at the end of this section, we will use this idea in an attempt to extract J from our data.…”

Section: Discussionmentioning

confidence: 99%

High pressure investigation of absorption spectra of J-aggregates

Lindrum

Chan

1996

The Journal of Chemical Physics

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The spectral shift of J-bands under high pressure up to 60 kbar has been investigated for J-aggregates of different cyanine dyes. Under conditions where no J-band can be observed at normal pressure, J-aggregates are formed at higher pressure. A red shift of absorption upon increasing pressure was found with a linear dependence of line position on pressure. The results can be explained by a change of dipolar coupling of monomer molecules in the aggregate due to decreasing center-to-center distances. The different pressure slopes of various aggregates are interpreted from their different aggregate structures. The monomer absorption is also red-shifted under pressure, but the pressure dependence is quite different and can be described by a solvent shift. From the linear dependence, the dipole-dipole coupling energy J can be determined with a simple theory. The general applicability and limitations of this method are discussed.

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A comparative pressure tuning hole burning study of protoporphyrin IX in myoglobin and in a glassy host

Cited by 29 publications

References 40 publications

Stark-effect experiments on photochemical holes in chromoproteins: protoporphyrin IX-substituted myoglobin.

Stark-effect experiments on photochemical holes in chromoproteins: protoporphyrin IX-substituted myoglobin.

Hole-Burning Spectroscopy of Proteins in External Fields: Human Serum Albumin Complexed with the Hypericinate Ion

High pressure investigation of absorption spectra of J-aggregates

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