7699-35-6Relevant articles and documents
Primary processes of the electronic excited states of trans-urocanic acid
Li,Hanson,Simon
, p. 969 - 972 (1997)
The primary photoreactivity of the excited states of trans-urocanic acid (t-UA) is investigated by ultrafast transient-absorption spectroscopy. Fundamentally different photophysics were observed when t-UA is excited at 266 nm, near the peak of the absorption spectrum, and 306 nm, in the red tail of the absorption spectrum. The data support the conclusion that the wavelength-dependent photophysics of t-UA is due to the presence of two different closely spaced electronic states. Excitation at 266 nm populates a ππ* state that is localized on the imidazole ring. The transient data following photoexcitation of t-UA at 266 nm in both a pH 5.6 and a pH 7.2 solution are similar, even though the protonation state of the tertiary nitrogen on the imidazole ring is different at these two pH values. The data therefore support that the photophysics at pH 5.6 and pH 7.2 must involve a common excited state. Steady-state excitation spectra suggest that a proton transfer process from t-UA to the solvent occurs following the excitation at 266 nm at pH 5.6, which generates an electronically excited singlet state of the deprotonated molecule. This state is directly accessed by the 266 nm excitation of t-UA at pH 7.2. The population in this singlet state decays by intersystem crossing with a rate constant of 1.4 × 1011 s-1. Isomerization is not believed to occur from this triplet state. Excitation of t-UA at 306 nm populates an entirely different state, which leads to isomerization. From the observed ground state repopulation dynamics, the minimum rate for the excited state isomerization is 1.2 × 1010 s-1.
cis-Urocanic acid induces mast cell degranulation and release of preformed TNF-α: A possible mechanism linking UVB and cis-urocanic acid to immunosuppression of contact hypersensitivity
Wille, John J.,Kydonieus, Agis F.,Murphy, George F.
, p. 18 - 27 (1999)
The search for effective inhibitors of transdermal drug-induced contact sensitization was directed to dermal mast-cell-degranulating agents (MCDA). Human skin organ cultures were employed to test whether cis-urocanic acid (C-UA) and other potential MCDAs cause mast cell degranulation. These were then tested for their ability to inhibit the induction phase of the contact hypersensitivity reaction (CHR). C-UA at 1 μg/ml significantly depleted mast cell chymase, whereas trans-urocanic acid (T-UA) was relatively ineffective. C-UA, but not T-UA, induced local effects of liberated mast cell TNF-α, as detected by E-selectin expression on the micro-vascular dermal endothelium. C-UA significantly reduced (> 70%) the ear swelling response in Balb/c mice, when applied 24 h prior to application of a sensitizing amount of dinitrochlorobenzene (DNCB), and induced a prolonged (> 3 weeks) state of immune tolerance (> 40%). Similar effects on local immunosuppression of CHR were observed with topical chloroquine and capsaicin, while cromolyn, a mast cell membrane stabilizer, was unable to inhibit DNCB-induced CHR. It is suggested that MCDAs may interfere with downstream events associated with accessory cell function.
Concerning the photodiastereomerization and protic equilibria of urocanic acid and its complex with human serum albumin
Schwarzinger, Bettina,Falk, Heinz
, p. 1297 - 1304 (2004)
Photodiastereomerization of urocanic acid and its human serum albumin complex (its binding constant was estimated to amount 4.1·10 -4dm3·mol-1) was investigated. It was found that although the photodiastereomerization rates were similar, the photoequilibrium positions differed significantly ((E):(Z) = 33:77 for free urocanic acid, and 50:50 for the complex). This is thought to be due to a different stabilization of the corresponding orthogonal excited states. The thermal barrier of diastereomerization was estimated to amount to more than 250 kJ·mol-1 making it a very unlikely process under physiological and photodiastereomerization conditions. The various prototropic species of the two diastereomers at various pH values were analyzed by means of a mathematical model and from these results a novel photoinduced pH-jump methodology allowing for fast, persistent, diffusion controlled, and bidirectional jumps is proposed. Springer-Verlag 2004.
A Nitrogen-15 Nuclear Magnetic Resonance Study of the Acid-Base and Tautomeric Equilibria of 4-Substituted Imidazoles and Its Relevance to the Catalytic Mechanism of α-Lytic Protease
Roberts, John D.,Yu, Chun,Flanagan, Cynthia,Birdseye, Theresa R.
, p. 3945 - 3949 (1982)
The pH dependence of the 15NMR shifts of histamine, imidazole-4-propionic acid, imidazole-4-acetic acid, trans- and cis-urocanic acid, and endo-cis-3-(4-imidazoyl)bicyclohept-5-ene-2-carboxylic acid has been determined at the natural-abundance level of 15N.The chemical-shift changes permit calculation of pKa values for the acidic species present as well as reasonably accurate positions of the N1(H)N3(H) tautomeric equilibria for those species having unprotonated imidazole rings.The 15N shifts of cis-urocanic acid and endo-cis-3-(4-imidazoyl)bicyclohept-5-ene-2-carboxylic acid demonstrate that carboxylate-N3(H) hydrogen-bonding interactions can cause the N3(H) tautomers to be substantially more stable than the N1(H) tautomers.The unusual positions of these tautomeric equilibria are quite similar to that found for the histidine of the catalytic triad of α-lytic protease.
Diffusion of E and Z urocanic amphiphiles through skin and their insertion in a membrane model
Sirieix-Plenet,Ader,Miquel,Mavon,Lauth-de Viguerie
, p. 425 - 433 (2002)
The incorporation of synthetic urocanic amphiphiles into a membrane model is described. A monomolecular film of dipalmitoyl phosphatidylcholine (DPPC) and cholesterol was formed at the air-water interface and used as a model. In parallel, diffusion of these derivatives through the skin was studied using rat skin on flow-through diffusion cells. The flux and the cumulative amount were determined. Although the structure and the composition of the DPPC/cholesterol monolayer differed greatly from multilayers of epidermal lipids, the results obtained in the incorporation and diffusion studies were similar. The structure of the urocanic amphiphiles was very close, but the membranes led to the following flux or insertion classification: Ester E > Ester Z ? Amide E. From the results obtained and for simplicity, the technique of Langmuir monolayers seems to be highly suited to the primary screening of amphiphilic compounds. Copyright
THE USE OF UROCANIC ACID BEING ABLE TO ACIDIFY THE CELL CYTOPLASM AND FOR PREVENTING OR HALTING CELLULAR PROLIFERATION IN A PERSON
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Page/Page column 6-7, (2008/06/13)
This invention relates to the use of urocanic acid or another pharmaceutically acceptable agent being able to acidify the cell cytoplasm, for the manufacture of a pharmaceutical composition useful for causing inhibition or halting of transformed or non-transformed cell proliferation in a person or an animal, wherein an effective amount of said agent is administered in an essentially non-dissociated form to the person or animal. This invention also concerns the use of said agent as an enhancer for other therapeutically active agents. The invention also concerns a pharmaceutical composition.
