Deciphering the protonation and tautomeric equilibria of firefly oxyluciferin by molecular engineering and multivariate curve resolution

Rębarz, Mateusz; Kukovec, Boris-Marko; Maltsev, Oleg V.; Ruckebusch, Cyril; Hintermann, Lukas; Naumov, Panče; Sliwa, Michel

doi:10.1039/c3sc50715g

Cited by 63 publications

(167 citation statements)

References 38 publications

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“…[21][22][23] It was also found that the ground-state enolate!enol dianion has a pK a of 9.10. [23] The absorption spectrum of firefly oxyluciferin in water has a band at approximately 380 nm at acidic/ neutral pH, and a band at approximately 420 nm at basic pH. [22,26] The emission spectrum is characterized by a peak at approximately 550 nm at acidic/neutral pH, and a peak at ap-A theoretical analysis of the enol-based photoacidity of oxyluciferin in water is presented.…”

Section: Introductionmentioning

confidence: 95%

Theoretical Study of the Nontraditional Enol‐Based Photoacidity of Firefly Oxyluciferin

Silva

2014

ChemPhysChem

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A theoretical analysis of the enol-based photoacidity of oxyluciferin in water is presented. The basis for this phenomenon is found to be the hydrogen-bonding network that involves the conjugated photobase of oxyluciferin. The hydrogen-bonding network involving the enolate thiazole moiety is stronger than that of the benzothiazole phenolate moiety. Therefore, enolate oxyluciferin should be stabilized versus the phenolate anion. This difference in strength is attributed to the fact that the thiazole moiety has more potential hydrogen-bond acceptors near the proton donor atom than the benzothiazole moiety. Moreover, the phenol-based excited-state proton transfer leads to a decrease in the hydrogen-bond acceptor potential of the thiazole atoms. The ground-state enol-based acidity of oxyluciferin is also studied. This phenomenon can be explained by stabilization of the enolate anion through strengthening of a bond between water and the nitrogen atom of the thiazole ring, in an enol-based proton-transfer-dependent way.

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Section: Introductionmentioning

confidence: 95%

Theoretical Study of the Nontraditional Enol‐Based Photoacidity of Firefly Oxyluciferin

Silva

2014

ChemPhysChem

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“…94 or derived from calculated and experimental data. All calculations were carried out at the ωB97X-D/6-31+G(d,p) level of theory using a hybrid cluster-continuum model including 11 explicit water molecules.…”

Section: 94mentioning

confidence: 99%

Computational Studies of Photobiological Keto-Enol Reactions and Chromophores

Falklöf¹

2015

Linköping Studies in Science and Technology. Dissertations

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This thesis presents computational chemistry studies of keto-enol reactions and chromophores of photobiological significance.The first part of the thesis is concerned with two protein-bound chromophores that, depending on the chemical conditions, can exist in a number of different ketonic and enolic forms. The first chromophore is astaxanthin, which occurs in the protein complex responsible for the deep-blue color of lobster carapace. By investigating how different forms of astaxanthin absorb UV-vis radiation of different wavelengths, a model is presented that explains the origin of the dramatic color change from deep-blue to red upon cooking of live lobsters.The second chromophore is the oxyluciferin light emitter of fireflies, which is formed in the catalytic center of the enzyme firefly luciferase. To date, there is no consensus regarding which of the possible ketonic and enolic forms is the key contributor to the light emission. In the thesis, the intrinsic tendency of oxyluciferin to prefer one particular form over other possible forms is established through calculation of keto-enol and acid-base excited-state equilibrium constants in aqueous solution.The second part of the thesis is concerned with two families of biological photoreceptors: the blue-light-absorbing LOV-domain proteins and the red-lightabsorbing phytochromes. Based on the ambient light environment, these proteins regulate physiological and developmental processes by switching between inactive and active conformations. In both families, the conversion of the inactive into the active conformation is triggered by a chemical reaction of the respective chromophore.The LOV-domain proteins bind a flavin chromophore and regulate processes such as chloroplast relocation and phototropism in plants. An important step in the activation of these photoreceptors is a singlet-triplet transition between two electronically excited states of the flavin chromophore. In the thesis, this transition is used as a prototype example for illustrating, for the first time, the ability of first-principles methods to calculate rate constants of inter-excited state phosphorescence events.Phytochromes, in turn, bind bilin chromophores and are active in the regulation of processes like seed germination and flowering time in plants. Following two systematic studies identifying the best way to model the UV-vis absorption iii iv and fluorescence spectra of these photoreceptors, it is demonstrated that steric interactions between the chromophore and the apoprotein play a decisive role for how phytochromes are activated by light. Populärvetenskaplig sammanfattningSolljusär en förutsättning för liv på jorden. Växter använder solljus som energikälla för att kunna bilda näring till sig själva ochäven syre till andra organismer. Iögonen hos människor och djur finns specialdesignade celler som omvandlar ljus till elektriska impulser, som sedan tolkas till en bild av syncentrat i hjärnan. Djur har utvecklat mekanismer för att med hjälp av ljus kunna kamouflera sig, locka till s...

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“…[41] or derived from calculated and experimental data. All calculations were carried out at the ωB97X-D/6-31+G(d,p) level of theory using a hybrid cluster-continuum model including Starting by comparing keto-OxyLH 2 with enol-OxyLH 2 (reaction I in Fig.…”

Section: Paper IIImentioning

confidence: 99%

Photochemical properties of phytochrome and firefly luciferase chromophores: A theoretical study

Falklöf¹

2014

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This licentiate thesis presents computational chemistry studies on photochemical properties of phytochrome and firefly luciferase chromophores.Phytochromes are bilin-containing proteins that based on the ambient light environment regulate a number of physiological and developmental processes in bacteria, cyanobacteria, fungi and plants. From the viewpoint of computational modeling, however, only a few studies have been devoted to these systems. In this thesis, two systematic studies comparing calculated and experimental UV-vis spectra of bilin chromophores in protein and solution environments are presented. The first study focuses on how hybrid quantum mechanics/molecular mechanics methods are best applied to calculate absorption spectra of a bacteriophytochrome. The second study, in turn, investigates the performance of a number of quantum chemical methods in calculating absorption and emission spectra of sterically locked bilin chromophores.Firefly luciferase catalyzes a chemical reaction in which the electronically excited oxyluciferin is formed and subsequently emits light. Depending on the conditions, oxyluciferin can exist in a number of different chemical forms. To date, there is no consensus regarding which of these that most significantly contributes to the light emission. In this thesis, the most probable form of the light emitter is predicted by calculating excited-state pK E and pK a values, in aqueous solution, of the various equilibrium reactions relevant for the oxyluciferin system.iii iv

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Deciphering the protonation and tautomeric equilibria of firefly oxyluciferin by molecular engineering and multivariate curve resolution

Cited by 63 publications

References 38 publications

Theoretical Study of the Nontraditional Enol‐Based Photoacidity of Firefly Oxyluciferin

Theoretical Study of the Nontraditional Enol‐Based Photoacidity of Firefly Oxyluciferin

Computational Studies of Photobiological Keto-Enol Reactions and Chromophores

Photochemical properties of phytochrome and firefly luciferase chromophores: A theoretical study

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