On the Intensity and Time Dependence of Product Yields in Biphotonic Processes.

Moan, Johan Emelian; Eriksson, Sven O.; Andresen, Arne F.

doi:10.3891/acta.chem.scand.26-4177

Cited by 5 publications

(4 citation statements)

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“…1973a) or pulsed laser photolysis (Bent and Hayon, 1975a;Lachish et al, 1976) several authors showed that a biphotonic mechanism applies also in this case. At the same time, the formalism of consecutive biphotonic processes via metastable states was analysed by a number of authors (Pilloff and Albrecht, 1968;Moan and Steen, 1971;Moan, 1972;Lachish et al, 1976). It was shown that if proportionality between the yield and I" (where I is the light flux through the probe cell) is obtained in an experiment, it may bc that the process is really related to I", where m > n. This argument was used by various authors in order to explain values of n < 2 obtained on systems, including phenolic compounds, where biphotonic processes were assumed to occur.…”

Section: Mol-'mentioning

confidence: 99%

“…This is easily done under conditions of flash excitation. The interpretation of the results is, however, less easy, since the yield-intensity relationship obtained reflects not only the photolysis mechanism itself, but also the relative magnitude of the formation rates of the intermediate and the final state, and ground state depletion (Moan and Steen, 1971;Moan, 1972;Lachish et al, 1976). Furthermore, flash conditions are characterized by light intensities higher by several orders of magnitude than those which may be taken as typical for "biological conditions".…”

Section: Introductionmentioning

confidence: 99%

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Pathways for Formation of Hydrated Electrons From Excited Phenol and Related Compounds

Grabner

Köhler

Zechner

et al. 1977

Photochem & Photobiology

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Abstract. The dependence of primary photophysical and photochemical processes, especially of electron photoejection, in phenol and related compounds in aqueous solution on excitation intensity and excitation energy is examined. Theoretical and experimental evidence is presented for the possibility of three pathways for electron ejection: (1) A monophotonic pathway via the fluorescent state, which most probably does not involve the lowest triplet state; (2) a monophotonic pathway requiring higher excitation energies, which takes place in competition with internal conversion to the fluorescent state; and (3) a consecutive biphotonic pathway in which the lowest triplet state absorbs the second photon, and which can become predominant at high intensities, e.g. under flash conditions. It is shown that this model reconciles apparently conflicting results published in the literature.

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Section: Mol-'mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Pathways for Formation of Hydrated Electrons From Excited Phenol and Related Compounds

Grabner

Köhler

Zechner

et al. 1977

Photochem & Photobiology

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“…No significant difference in the yield of the cleavage was observed, which would have suggested a biphotonic process. However, the linear light intensity dependency of the yields observed is not strict evidence for a monophotonic process . The wavelength dependence was studied between λ = 240 and 295 nm.…”

Section: Resultsmentioning

confidence: 97%

“…However, the linear light intensity dependency of the yields observed is not strict evidence for a monophotonic process. 29 The wavelength dependence was studied between λ = 240 and 295 nm. First, we tested whether wavelengths with λ < 240 nm from the RPR-2537Å lamps contributed to the cleavage.…”

Section: ■ Resultsmentioning

confidence: 99%

Photodegradation of Human Growth Hormone: A Novel Backbone Cleavage between Glu-88 and Pro-89

Steinmann

Wang

et al. 2013

Mol. Pharmaceutics

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The exposure of protein pharmaceuticals to light can cause loss of potency, oxidation, structural changes and aggregation. To elucidate the chemical pathways of photodegradation, we irradiated human growth hormone (hGH) at λ = 254 nm, λ ≈ 265-340 nm, and λ ≈ 295-340 nm (using the spectral cutoff of borosilicate glass) and analyzed the products by mass spectrometry. By means of LC-MS/MS analysis, we observed an unusual peptide backbone cleavage between Glu-88 and Pro-89. The crystal structure of hGH indicates that these residues are in proximity to Trp-86, which likely mediates this backbone cleavage. The two cleavage fragments observed by MS/MS analysis indicate the loss of CO from the amide bond and replacement of the Glu-C(═ O)Pro bond with a Glu-H bond, accompanied by double bond formation on proline. The reaction is oxygen-independent and likely involves hydrogen transfer to the Cα of Glu-88. To probe the influence of the protein fold, we irradiated hGH in its unfolded state, in 1:1 (v/v) acetonitrile/water, and also the isolated tryptic peptide Ile-78-Arg-90, which contains the Glu-88-Pro-89 sequence. In both cases, the cleavage between Glu-88 and Pro-89 was largely suppressed, while other cleavage pathways became dominant, notably between Gln-84 and Ser-85, as well as Ser-85 and Trp-86.

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Kinetics of nonlinear photoreactions in dye solutions

Mikhailov¹,

Rylkov²

1981

J Appl Spectrosc

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On the Intensity and Time Dependence of Product Yields in Biphotonic Processes.

Cited by 5 publications

References 0 publications

Pathways for Formation of Hydrated Electrons From Excited Phenol and Related Compounds

Pathways for Formation of Hydrated Electrons From Excited Phenol and Related Compounds

Photodegradation of Human Growth Hormone: A Novel Backbone Cleavage between Glu-88 and Pro-89

Kinetics of nonlinear photoreactions in dye solutions

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