Structure of Urocanic Acid Photodimers

Anglin, J. H.; Batten, W. H.

doi:10.1111/j.1751-1097.1970.tb05995.x

Cited by 16 publications

(10 citation statements)

References 7 publications

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“…Serious doubt, however, has recently been raised about this hypothesis because of the much greater efficiency (by a factor of -~ 3) in the production of UCA in fur-bearing animals than in humans (40). Photochemically, UCA has the following properties: (a) a UV-dependent trans ~ cis isomerization (47), (b) a capability of forming photodimers (48), and (c) a capability to bind to DNA in a UV-dependent manner (49). Isomerization to the cis isomer produces a more water-soluble form.…”

Section: Discussionmentioning

confidence: 99%

Mechanism of immune suppression by ultraviolet irradiation in vivo. I. Evidence for the existence of a unique photoreceptor in skin and its role in photoimmunology.

Fabo¹,

Noonan²

1983

The Journal of Experimental Medicine

507

278

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UV irradiation of mice causes a systemic immune alteration that can be detected either by suppression of the immunologic rejection of UV-induced tumors, or by suppression of contact hypersensitivity (CHS). Suppression of these two immunologic responses has similar photobiologic characteristics and in both cases is associated with the generation of antigen-specific suppressor T cells. To identify whether a specific photoreceptor for this effect exists, the relative wavelength effectiveness (action spectrum) was determined for the UV-induced suppression of CHS. Narrow bands of UV (half bandwidth 3 nm) were used at 10 wavelengths from 250 to 320 nm to obtain dose-response curves. Irradiation with each of these bands of UV caused dose-dependent immunosuppression of CHS, but with differing effectiveness. Immunosuppression was clearly separable from the generation of gross skin damage and inflammation. Further, immunosuppression by the most effective wavelength (270 nm) was associated with the generation of antigen-specific suppressor cells. The action spectrum derived from the dose-response curves has a maximum between 260 and 270 nm, a shoulder at 280-290 nm, and declines steadily to approximately 3% of maximum at 320 nm. The finding of such a clearly defined wavelength dependence implies the presence of a specific photoreceptor for this effect. Removing the stratum corneum by tape stripping before UV irradiation prevented the suppression of CHS using 254-nm radiation, suggesting the photoreceptor is superficially located in the skin. A number of epidermal compounds with absorption spectra similar to the action spectrum are discussed and evaluated with respect to their potential for being the photoreceptor. Based on (a) the close fit of its absorption spectrum to the action spectrum, (b) its superficial location in the stratum corneum, and (c) its photochemical properties, the hypothesis is advanced that the photoreceptor for systemic UV-induced immunosuppression of contact hypersensitivity may be urocanic acid. As such, it may also play a role in UV-induced carcinogenesis via the production of tumor-specific suppressor cells.

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Section: Discussionmentioning

confidence: 99%

Mechanism of immune suppression by ultraviolet irradiation in vivo. I. Evidence for the existence of a unique photoreceptor in skin and its role in photoimmunology.

Fabo¹,

Noonan²

1983

The Journal of Experimental Medicine

507

278

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“…When absorbed ultraviolet light, trans ‐urocanic acid is converted in vivo to the cis isomer and acts as an endogenous sunscreen or photoprotectant against UV‐induced DNA damage . Similarly, UV irradiation in solution results in a mixture of cis and trans isomers, whereas irradiation of crystalline urocanic acid produces no photochemical change . While the direct [2+2]‐photodimerization of urocanic acid itself has never been achieved, its derivatives were found to be capable of undergoing this transformation in solution or in the solid state .…”

Section: Methodsmentioning

confidence: 99%

“…Similarly, UV irradiation in solution results in a mixture of cis and trans isomers, whereas irradiation of crystalline urocanic acid produces no photochemical change . While the direct [2+2]‐photodimerization of urocanic acid itself has never been achieved, its derivatives were found to be capable of undergoing this transformation in solution or in the solid state . A rapid screening of some acid additives mentioned in Table under our conditions of mixing/stirring irradiation led once again to the identification of oxalic as the unique suitable additive to provide exclusively β‐truxinic type dimer β59 in 80 % conversion after 7 d of irradiation (Scheme ).…”

Section: Methodsmentioning

confidence: 99%

[2+2] Photodimerization of Stilbazoles Promoted by Oxalic Acid in Suspension

Nguyễn

Nguyen

Retailleau

2020

Chemistry A European J

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In this study, a very simple technique to perform efficiently photodimerization of some vinylpyridines is reported. By irradiating a stirred mixture of several stilbazoles with solid oxalic acid dihydrate dispersed in a nonpolar (i.e., cyclohexane) or moderately polar (benzene, dichloromethane, dioxane) solvent, the corresponding dimeric cyclobutane adducts were obtained in high yields and excellent regio‐ and stereoselectivities. The strategy could also be applied successfully to oily, waxy, or even insoluble stilbazoles. Moreover, the oxalic acid loading could be lowered to substoichiometric amounts. When further optimizations were needed, our strategy was found to be highly flexible to identify other oligocarboxylic acids as alternative additives to improve, or even overturn, the regioselectivity. Oxalic acid and other oligocarboxylic acids were found to be capable of orienting more than 50 stilbazoles toward photodimerization under these conditions.

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“…There are ample precedents for the excited state of DMT to react through photocycloaddition, both to another DMT molecule (73) as well as to other olefins (127,128). However, the UA excited state is also known to photodimerize, albeit only in the solid state (50). A ground-state complex of UA and DMT is evident from the hyperchromicity observed at 320 nm in the absorption spectrum of the two reactants (69).…”

Section: Mechanistic Studies Related To the Binding Of Ua To Dnamentioning

confidence: 99%