&lt;title&gt;Laser spectroscopy of ultrafast processes in organic radicals&lt;/title&gt;

Borisevich, N. A.; Lysak, N. A.; Melnichuk, S. V.; Tikhomirov, S. A.; Tolstorozhev, G. B.

doi:10.1117/12.131854

Cited by 3 publications

(11 citation statements)

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“…100 fs time resolution of the instrument. The transients compare well with typical absorbance spectra of p-aminophenylthiyl radicals and p-tolylthiyl radicals, 1,49,50 showing that fast photocleavage of the disulfide bond has taken place. From the observed transient absorbance 51 we estimated a disulfide bond dissociation quantum yield of 0.10 ( 0.04 at a delay time of 0.5 ps for peptide 2.…”

Section: Resultssupporting

confidence: 52%

“…This behavior is similar to that observed for p-aminophenylthiyl radicals after photolysis of bis(paminophenyl) disulfide in acetonitrile, 2 which was attributed to dielectric and vibrational relaxation. Part of the shift is believed to arise from an internal charge separation between the amino group and the sulfur atom, 1 as is discussed further below. On a longer time scale, the width of the absorbance band (fwhm) increases from 115 nm at 50 ps to 130 nm at 3.5 ns without any significant shift of the position of the maximum (Figure 1B).…”

Section: Resultsmentioning

confidence: 99%

“…The bondbreaking step is known to occur on the femtosecond time scale from studies with model compounds. [1][2][3] After dissociation the radicals may undergo recombination to form the original disulfide. For model disulfides that are not constrained by the peptide the recombination has a geminate phase that is kinetically distinct from the diffusion-controlled bimolecular recombination.…”

Section: Introductionmentioning

confidence: 99%

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Peptide Conformational Dynamics and Vibrational Stark Effects Following Photoinitiated Disulfide Cleavage

et al. 1997

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Photoinitiation of relaxation of two peptides (labeled 1 and 2) and spectroscopic studies of the ensuing dynamics have led to new information about peptide conformational dynamics. Following photolysis of the aryl disulfide chromophore that constrains a peptide to be distorted from its equilibrium form, the S−S bond is broken in <200 fs, and the liberated thiyl radicals either undergo geminate recombination or diffuse apart to allow the peptides to change conformation. From anisotropy measurements, overall peptide rotation is on the time scale of 600 ps. At an even earlier time (ca. 100 ps), transient IR measurements show a bleaching of the amide I‘ region, arising from a vibrational Stark effect produced upon ring opening of peptide 2. We did not detect any significant shift in the amide I‘ region up to 2 ns, suggesting no significant helix formation in this time domain. Thiyl radicals arising from peptide 2 recombine with a power law rate over the time range from picoseconds to microseconds signaling an unusual type of scaled kinetics.

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Section: Resultssupporting

confidence: 52%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Peptide Conformational Dynamics and Vibrational Stark Effects Following Photoinitiated Disulfide Cleavage

et al. 1997

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“…Excitation at 260 nm dissociated the disulfide bond and the absorption of the resulting p-aminophenylthiyl radicals was monitored at 550 nm. [25,29,33] The time evolution of the radical absorption on photodissociation of 1, 3 and 4 in acetonitrile is shown in Figure 3. When the cross-linking reagents 6, 8 and 10 were photolysed, the thiyl radicals that were generated reacted with the maleimide moieties, which complicated the analysis of these systems.…”

Section: Resultsmentioning

confidence: 99%

“…For example, thiyl radicals generated after photolysis of diphenyl disulfide recombine significantly faster than thiyl radicals generated after photolysis of bis(p-aminophenyl) disulfide. [21,24,25] The quantum yield of photocleavage is also solvent dependent; more p-aminophenyl thiyl radical is generated in polar solvents compared with nonpolar solvents. [26] The two competing processes which determine the quantum yield of photocleavage are geminate recombination and the escape of the radical pair from the solvent cage ( Figure 1).…”

Section: Resultsmentioning

confidence: 99%

Synthesis and Photochemistry of a New Class of Photocleavable Protein Cross‐linking Reagents

Milanesi

Reid

Beddard

et al. 2004

Chemistry A European J

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A new series of photocleavable protein cross-linking reagents based on bis(maleimide) derivatives of diaryl disulfides have been synthesised. They have been functionalised with cysteine and transient absorption spectra for the photolysis reaction have been recorded by using the pump-probe technique with a time resolution of 100 femtoseconds. Photolysis of the disulfide bond yields the corresponding thiyl radicals in less than a picosecond. There is a significant amount of geminate recombination, but some of the radicals escape the solvent cage and the quantum yield for photocleavage is 30 % in water.

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Theoretical Insight into the Photodegradation of a Disulfide Bridged Cyclic Tetrapeptide in Solution and Subsequent Fast Unfolding−Refolding Events

et al. 2010

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We report the photoinduced peptide bond (C-N) of an amide unit and S-S bond fission mechanisms of the cyclic tetrapeptide [cyclo(Boc-Cys-Pro-Aib-Cys-OMe)] in methanol solvent by using high-level CASSCF/CASPT2/Amber quantum mechanical/molecular mechanical (QM/MM) calculations. The subsequent energy transport and unfolding-refolding events are characterized by using a semiempirical QM/MM molecular dynamics (MD) simulation methodology that is developed in the present work. In the case of high-energy excitation with <193 nm light, the tetrapeptide molecule in the (1)n pi* surface overcomes two barriers with approximately 10.0 kcal/mol, respectively, and uses energy consumption for breaking the hydrogen bond as well as the N-C bond in the amide unit, ultimately leading to the ground state via a conical intersection of CI (S(NP)/S(0)) by structural changes of an increased N-C distance and a O-C-C angle in the amide unit (a two-dimensional model of the reaction coordinates). Following this point, relaxation to a hot molecule with its original structure in the ground state is the predominant decay channel. A large amount of heat (approximately 110.0 kcal/mol) is initially accumulated in the region of the targeted point of the photoexcitation, and more than 60% of the heat is rapidly dissipated into the solvent on the femtosecond time scale. The relatively slower propagation of heat along the peptide backbone reaches a phase of equilibration within 3 ps. A 300 nm photon of light initiates the relaxation along the repulsive S(sigma sigma)((1)sigma sigma*) state and this decays to the CI (S(sigma sigma)/S(0)) in concomitance with the separation of the disulfide bond. Once cysteinyl radicals are generated, the polar solvent of methanol molecules rapidly diffuses around the radicals, forming a solvent cage and reducing the possibility of close contact in a physical sense. The fast unfolding-refolding event is triggered by S-S bond fission and powered by dramatic thermal motion of the methanol solvent that benefits from heat dissipation. The beta-turn opening (unfolding) can be achieved in about 120 ps without the inclusion of the time associated with the photochemical steps and eventually relaxes to a 3(10)-helix structural architecture (refolding) within 200 ps.

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<title>Laser spectroscopy of ultrafast processes in organic radicals</title>

Cited by 3 publications

References 0 publications

Peptide Conformational Dynamics and Vibrational Stark Effects Following Photoinitiated Disulfide Cleavage

Peptide Conformational Dynamics and Vibrational Stark Effects Following Photoinitiated Disulfide Cleavage

Synthesis and Photochemistry of a New Class of Photocleavable Protein Cross‐linking Reagents

Theoretical Insight into the Photodegradation of a Disulfide Bridged Cyclic Tetrapeptide in Solution and Subsequent Fast Unfolding−Refolding Events

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