Demonstration of a pulsed photoelectron spectrometer on mass-selected negative ions: O−, O2−, and O4−

Posey, Lynmarie A.; DeLuca, Michael J.; Johnson, Mark A.

doi:10.1016/0009-2614(86)80539-5

Cited by 160 publications

(103 citation statements)

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“…The resulting photoelectrons were analyzed in our apparatus (32) by using a magnetic bottle photoelectron spectrometer. The powerful methodology of mass selection͞electron detachment provided the needed resolution of species and state (33)(34)(35)(36), whereas the pump-probe femtosecond chemistry configuration allowed for the temporal resolution.…”

Section: Methodsmentioning

confidence: 99%

Primary steps of the photoactive yellow protein: Isolated chromophore dynamics and protein directed function

Lee

Zewail

2006

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

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The cycle of the photoactive yellow protein (PYP) has been extensively studied, but the dynamics of the isolated chromophore responsible for transduction is unknown. Here, we present realtime observation of the dynamics of the negatively charged chromophore and detection of intermediates along the path of transto-cis isomerization using femtosecond mass selection͞electron detachment techniques. The results show that the role of the protein environment is not in the first step of double-bond twisting (barrier crossing) but in directing efficient conversion to the cisstructure and in impeding radical formation within the protein.femtobiology ͉ transduction ͉ molecular dynamics ͉ photoelectron spectroscopy P hotoactive yellow protein (PYP) is a water-soluble photoreceptor found in Halorhodospira halophila and related halophilic bacterial species (1). The chromophore responsible for perception of light and phototactic response is a deprotonated trans-4-hydroxycinnamic acid (also known as p-coumaric acid) covalently linked to a cysteine residue of the protein via a thioester bond (Fig. 1). Light absorption of the PYP chromophore leads to the initiation of a complex photocycle involving several intermediates. With a variety of biophysical techniques (2-5), it is concluded that the first intermediate (I 0 ) in the photocycle is formed within a few picoseconds, with the chromophore changing to the cis configuration, in a trans-to-cis isomerization process (7-11). The intermediates at longer times have been trapped and identified by x-ray crystallography (12, 13).The critical change of the chromophore in the primary process of isomerization is accompanied or followed by several other processes: proton transfer, protein conformational change, solvation, and disruption of hydrogen-bonding. This complexity can be reduced if the chromophore in its true anionic, not neutral, structure can be studied free of perturbations. With model compounds, the solvent effect can be assessed by studying them in the solution phase (14-18). However, the nature of intramolecular change and the timescales involved are still unknown. It is, therefore, desirable to study the primary isomerization dynamics of the PYP chromophore in isolation, especially in view of the fact that the mechanism for forming the first intermediate (I 0 ) is debatable (2). A gas-phase spectroscopic study has already been reported (19), but it was for the neutral molecule, not the anion structure in the protein.In this work, we report direct observation of the dynamics of the isolated PYP anionic chromophore. To disentangle the role of protein binding and distant torsions, we preserved the central structure involved in the isomerization about the double bond but use the CH 3 group for termination (see Fig. 1). The chromophore, hereafter called P, is excited with a femtosecond pulse from its ground state, the dark state in the protein, to the trans configuration using the mass-selected ions. For probing we use another femtosecond pulse to photodetach and resolve the phot...

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Section: Methodsmentioning

confidence: 99%

Primary steps of the photoactive yellow protein: Isolated chromophore dynamics and protein directed function

Lee

Zewail

2006

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

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“…More than one decade later, other groups incorporated this technique into their experiments. Additional concepts, such as time-of-flight mass separators, supersonic molecular beams, and laser desorption (Posey et al, 1986;Ganteför et al, 1988;Hugh et al, 1989;Hoe et al, 1990;Taylor et al, 1992;Cha et al, 1992) opened new options to study systems that were hardly accessible before, such as larger molecules, and atomic and molecular clusters. Finally, the development of the zero-kinetic-energy photoelectron spectroscopy (ZEKE) for anions (Kitsopoulos et al, 1989;Ganteför et al, 1990;Drechsler et al, 1994b) based on the cation 4 neutral ZEKE method (Müller-Dethlefs et al, 1984a;) allowed one to push the energy resolution to the magic limit of 1 cm Ϫ1 .…”

mentioning

confidence: 98%

Negative ions, mass selection, and photoelectrons

Boesl

Knott

1998

Mass Spectrom. Rev.

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“…This is the instrumental resolution function used in the simulations of Sections IV and V. Figure 2 shows a schematic of the negative ion photoelectron spectrometer used in these studies.28 A similar instrument is described by Posey et al 29 Because many of the AHB-anions of interest have high electron binding energies (3.80eV for IHI-, 4.27eV for BrHBr-), a pulsed UV laser is the most appropriate photodetachment light source, and the entire instrument is based on pulsed technology. An excellent review of pulsed methods in ion spectroscopy is provided by Johnson and Lit~eberger,~' and several components of our instruments are described in more detail therein.…”

mentioning

confidence: 99%

Transition State Spectroscopy of Bimolecular Reactions Using Negative Ion Photodetachment

Metz¹,

Bradforth²,

Neumark³

1991

Advances in Chemical Physics

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Demonstration of a pulsed photoelectron spectrometer on mass-selected negative ions: O−, O2−, and O4−

Cited by 160 publications

References 21 publications

Primary steps of the photoactive yellow protein: Isolated chromophore dynamics and protein directed function

Primary steps of the photoactive yellow protein: Isolated chromophore dynamics and protein directed function

Negative ions, mass selection, and photoelectrons

Transition State Spectroscopy of Bimolecular Reactions Using Negative Ion Photodetachment

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