Ultrafast Fluorescence Dynamics of Tryptophan in the Proteins Monellin and IIA<sup>Glc</sup>

Xu, Jianhua; Toptygin, Dmitri; Graver, Karen J.; Albertini, Rebecca A.; Savtchenko, Regina; Meadow, Norman D.; Roseman, Saul; Callis, Patrik R.; Brand, Ludwig; Knutson, Jay R.

doi:10.1021/ja055746h

Cited by 59 publications

(80 citation statements)

References 46 publications

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“…These obtained lifetimes correlate with neighboring chemical identities (46), separation distances, and observed f luorescence intensities and were used in the data analyses above. It should be noted that although changes in intensities and lifetimes ref lect quenching, these quenching dynamics are on the nanosecond time scale, and the blue-side emission wavelengths are more sensitive to solvation, which is typically on the picosecond time scale (11,47).…”

Section: Methodsmentioning

confidence: 99%

Protein surface hydration mapped by site-specific mutations

Kao

Zhang

et al. 2006

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

143

214

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Water motion at protein surfaces is fundamental to protein structure, stability, dynamics, and function. By using intrinsic tryptophans as local optical probes, and with femtosecond resolution, it is possible to probe surface-water motions in the hydration layer. Here, we report our studies of local hydration dynamics at the surface of the enzyme Staphylococcus nuclease using site-specific mutations. From these studies of the WT and four related mutants, which change local charge distribution and structure, we are able to ascertain the contribution to solvation by protein side chains as relatively insignificant. We determined the time scales of hydration to be 3-5 ps and 100 -150 ps. The former is the result of local librational͞rotational motions of water near the surface; the latter is a direct measure of surface hydration assisted by fluctuations of the protein. Experimentally, these hydration dynamics of the WT and the four mutants are also consistent with results of the total dynamic Stokes shifts and fluorescence emission maxima and are correlated with their local charge distribution and structure. We discuss the role of protein fluctuation on the time scale of labile hydration and suggest reexamination of recent molecular dynamics simulations.protein hydration ͉ femtosecond dynamics ͉ protein fluctuation ͉ selective mutation F rom the laboratories of the senior authors of this study (A.H.Z. and D.Z.) (1-11), there has been a series of reports regarding the time and length scales of the water layer around protein surfaces. These studies were for proteins subtilisin Carlsberg (2), monellin (3), phospholipase A 2 (5), melittin (9), and human serum albumin (8, 10). A theoretical model was developed to take into account the exchange with bulk water (4, 12), and the dynamics are consistent with molecular dynamics (MD) simulations of residence times (13-16) on time scales from femtoseconds to picoseconds. Earlier NMR studies have reported hydration dynamics (residence times) in the subnanosecond regime (17-20), but, more recently, a claim has been made that water motions at protein surfaces are ultrafast compared with bulk water, only slowing down by a factor of two to three (21,22). This Ͻ10-ps range would imply that the observed long-time hydration dynamics in tens of picoseconds are due to protein side-chain relaxation (22, 23). In our earlier studies (6), we addressed in detail this issue and the reasons for dominance of hydration dynamics. To quantify the contribution of sidechain motions to total solvation on the time scale of hydration, we must carefully alter the local structure while maintaining the same tryptophan site.In this contribution, we report the effect of mutation (four mutants on three site selections and the WT) on hydration of the enzyme Staphylococcus nuclease (SNase). Fig. 1 shows the x-ray structure of the protein, consisting of three ␣-helices and a five-stranded ␤-barrel with a total of 149 amino acids (24). The only single tryptophan residue (W140) has one edge exposed to the surface ...

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Section: Methodsmentioning

confidence: 99%

Protein surface hydration mapped by site-specific mutations

Kao

Zhang

et al. 2006

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

143

214

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“…A very fast libration was already observed in tryptophan analogs 27 that may still be operative in proteins and peptides, since tryptophan, while constrained by backbone connections, can still have molecular reorientation dominated by the "pocket" around the indole ring. We have begun femtosecond anisotropy analyses in proteins [28][29][30] with these effects in mind. The two conformations of perylene studied: butterfly and twisted.…”

Section: Discussionmentioning

confidence: 99%

Molecular Dynamics Simulations of Perylene and Tetracene Librations: Comparison With Femtosecond Upconversion Data

Rosales

et al. 2008

J. Phys. Chem. A

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In a prior manuscript by Xu et al. [Xu, J.; Shen, X.; Knutson, J. R. J. Phys. Chem. A 2003, 107, 8383], time-resolved fluorescence emission anisotropy measurements were performed on perylene and tetracene in hexadecane using an upconversion technique with ~100 fs resolution. The anisotropy transients contained previously unseen decay terms of ~300 fs. In perylene, their amplitude corresponded to the "r o defect" that has gathered interest over decades. We ascribed this term to a predominantly in-plane libration. In this manuscript, we present molecular dynamics simulations for the motions of perylene and tetracene using the CHARMm molecular dynamics program (version c29b2). Both rotational correlation functions contain subpicosecond decay terms that resemble experimental anisotropy decays. It was suggested that the r o defect might arise from excited-state distortions of perylene, so we conducted quantum mechanical calculations to show that such distortion does not significantly displace the oscillators. We compare the case of perylene, with a strongly allowed singlet emission transition, to that of the weakly allowed tetracene transition. In perylene, motion alone can explain subpicosecond anisotropy decay, while tetracene decay also contains vibrational coupling terms, as previously reported by Sarkar et al. [Sarkar, N.;Takeuchi, S.; Tahara, T. J. Phys. Chem. A 1999, 103, 4808].

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“…The unique (~16 ps) component (green squares) has a significant positive amplitude even above 390 nm (Fig. 8.7), and the spectral shape is not significantly narrowed (Xu et al, 2006). Normal solvent relaxation on the 16 ps timescale should have resulted in a positive/ negative DAS, or at least a narrowed and blue-shifted DAS without a significant positive amplitude near 400 nm.…”

Section: Ultrafast Fluorescence Dynamics Of Proteinsmentioning

confidence: 97%

“…Trp in the "sweet protein" monellin, however, cannot be fit without another ultrafast component. Figure 8.6A gives subpicosecond resolution fluorescence decays (20 ps full range) at three representative wavelengths for the protein monellin solution (black lines) and Trp solution (red lines) (Xu et al, 2006). The data in this figure were offset and peak normalized for easy comparison.…”

Section: Ultrafast Fluorescence Dynamics Of Proteinsmentioning

confidence: 99%

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Chapter 8 Ultrafast Fluorescence Spectroscopy via Upconversion

Knutson

2008

Fluorescence Spectroscopy

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This chapter reviews basic concepts of nonlinear fluorescence upconversion, a technique whose temporal resolution is essentially limited only by the pulse width of the ultrafast laser. Design aspects for upconversion spectrophotofluorometers are discussed, and a recently developed system is described. We discuss applications in biophysics, particularly the measurement of time-resolved fluorescence spectra of proteins (with subpicosecond time resolution). Application of this technique to biophysical problems such as dynamics of tryptophan, peptides, proteins, and nucleic acids is reviewed.

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Ultrafast Fluorescence Dynamics of Tryptophan in the Proteins Monellin and IIA^Glc

Cited by 59 publications

References 46 publications

Protein surface hydration mapped by site-specific mutations

Protein surface hydration mapped by site-specific mutations

Molecular Dynamics Simulations of Perylene and Tetracene Librations: Comparison With Femtosecond Upconversion Data

Chapter 8 Ultrafast Fluorescence Spectroscopy via Upconversion

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Ultrafast Fluorescence Dynamics of Tryptophan in the Proteins Monellin and IIAGlc

Cited by 59 publications

References 46 publications

Protein surface hydration mapped by site-specific mutations

Protein surface hydration mapped by site-specific mutations

Molecular Dynamics Simulations of Perylene and Tetracene Librations: Comparison With Femtosecond Upconversion Data

Chapter 8 Ultrafast Fluorescence Spectroscopy via Upconversion

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Ultrafast Fluorescence Dynamics of Tryptophan in the Proteins Monellin and IIA^Glc