Photoionization of Indole, N‐Methylindole and Tryptophan In Aqueous Solution upon Excitation at 193 nm

McGimpsey, W. Grant; Görner, Helmut

doi:10.1111/j.1751-1097.1996.tb03097.x

Cited by 27 publications

(37 citation statements)

References 46 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The latter spectrum has max at 570 nm and is consistent with the reported spectrum for the tryptophan radical cation that deprotonates with a rate constant of 1 ϫ 10 6 M Ϫ1 s Ϫ1 in neutral aqueous solution (37,38). The spectrum measured in neutral solution is in good agreement with the spectrum of the tryptophan radical with max at 520 nm (37,38). Spectra measured after reaction of 6,7-DMC •ϩ with tyrosine are also consistent with an electron transfer reaction as shown in Fig.…”

Section: Reactivity Of Psoralen and Coumarin Radical Cationssupporting

confidence: 87%

“…3 shows spectra obtained after reaction of 6,7-DMC •ϩ with tryptophan in aqueous buffer (a, pH 7) and in the presence of 5% trifluoroacetic acid (b). The latter spectrum has max at 570 nm and is consistent with the reported spectrum for the tryptophan radical cation that deprotonates with a rate constant of 1 ϫ 10 6 M Ϫ1 s Ϫ1 in neutral aqueous solution (37,38). The spectrum measured in neutral solution is in good agreement with the spectrum of the tryptophan radical with max at 520 nm (37,38).…”

Section: Reactivity Of Psoralen and Coumarin Radical Cationssupporting

confidence: 87%

See 1 more Smart Citation

Reactions of Psoralen Radical Cations with Biological Substrates†¶

Wood¹,

Mnyusiwalla²,

Chen³

et al. 2007

Photochemistry and Photobiology

View full text Add to dashboard Cite

The reactions of several psoralen and coumarin radical cations with biological substrates such as nucleotides, amino acids and alkenes that serve as models for unsaturated fatty acids have been examined. The radical cations were generated by laser photoionization of the parent psoralen or coumarin in aqueous buffer in most cases. Easily oxidized substrates such as tyrosine, tryptophan and guanosine monophosphate react with the 8-methoxypsoralen and several methoxy-substituted coumarin radical cations with rate constants in excess of 2 ؋ 10 9 M Ϫ1 s Ϫ1 . In each case reaction occurs via electron transfer, as demonstrated by the observation of quencher-derived radical cations or radicals by transient absorption spectroscopy. For other substrates such as histidine, methionine and adenosine monophosphate the measured rate constants are significantly slower and vary with the oxidation potential of both the parent psoralen or coumarin and the quencher, again indicative of electron transfer reactivity. Most of the alkenes studied also react with the psoralen or coumarin radical cations via electron transfer, although there is some evidence for addition for linoleic acid. Product studies carried out using both lamp and laser irradiation in the presence of deoxyguanosine as a radical cation trap lead to the formation of characteristic base-derived Type-I (electron transfer) products. This lends support to our previous hypothesis that photoionization occurs via a monophotonic process and is thus relevant to conditions used in clinical phototherapeutic applications of psoralens. The results demonstrate the relevance of electron transfer chemistry to the use of psoralens and related compounds as photoactivated drugs.

show abstract

Section: Reactivity Of Psoralen and Coumarin Radical Cationssupporting

confidence: 87%

Section: Reactivity Of Psoralen and Coumarin Radical Cationssupporting

confidence: 87%

Reactions of Psoralen Radical Cations with Biological Substrates†¶

Wood¹,

Mnyusiwalla²,

Chen³

et al. 2007

Photochemistry and Photobiology

View full text Add to dashboard Cite

show abstract

“…3B). The intensity decrease is the result of non-radiative processes such as intersystem crossing and photo-ionisation competing with fluorescence [48][49][50][51][52]. This is also observed for the other two amino acids.…”

Section: Resultsmentioning

confidence: 68%

A rapid, sensitive and economical assessment of monoclonal antibody conformational stability by intrinsic tryptophan fluorescence spectroscopy

Garidel

Hegyi

Bassarab

et al. 2008

Biotechnology Journal

102

View full text Add to dashboard Cite

Steady-state intrinsic tryptophan fluorescence spectroscopy is used as a rapid, robust and economic way for screening the thermal protein conformational stability in various formulations used during the early biotechnology development phase. The most important parameters affecting protein stability in a liquid formulation, e. g. during the initial purification steps or preformulation development, are the pH of the solution, ionic strength, presence of excipients and combinations thereof. A well-defined protocol is presented for the investigation of the thermal conformational stability of proteins. This allows the determination of the denaturation temperature as a function of solution conditions. Using intrinsic tryptophan fluorescence spectroscopy for monitoring the denaturation and folding of proteins, it is crucial to understand the influence of different formulation parameters on the intrinsic fluorescence probes of proteins. Therefore, we have re-evaluated and re-assessed the influence of temperature, pH, ionic strength, buffer composition on the emission spectra of tryptophan, phenylalanine and tyrosine to correctly analyse and evaluate the data obtained from thermal-induced protein denaturation as a function of the solution parameters mentioned above. The results of this study are a prerequisite for using this method as a screening assay for analysing the conformational stability of proteins in solution. The data obtained from intrinsic protein fluorescence spectroscopy are compared to data derived from calorimetry. The advantage, challenges and applicability using intrinsic tryptophan fluorescence spectroscopy as a routine development method in pharmaceutical biotechnology are discussed.

show abstract

“…Hence, ET from T will be higher than U. Redox potential (E ox ) value of T is less than U so this is also responsible for a better ET from T than U. Again, this methyl group has also the capability of acting as a better hydrogen donor in T. The methyl group possesses three additional hydrogen atoms, which can be transferred during HA [20,21]. So, the extent of HA will be higher for T too.…”

Section: Resultsmentioning

confidence: 93%