Bioluminescence - The Vibrant Glow of Nature and its Chemical Mechanisms

Bioluminescence, the mesmerizing natural phenomenon where living organisms produce light through chemical reactions, has long captivated scientists and laypersons alike, offering a rich tapestry of insights into biological function, ecology, evolution as well as the underlying chemistry. This comprehensive introductory review systematically explores the phenomenon of bioluminescence, addressing its historical context, geographic dispersion, and ecological significance with a focus on their chemical mechanisms. Our examination begins with terrestrial bioluminescence, discussing organisms from different habitats. We analyze thefireflies of Central Europe's meadows and the fungi in the Atlantic rainforest of Brazil. Additionally, we inspect bioluminescent species in New Zealand, specifically river-dwelling snails and mosquito larvae found in Waitomo Caves. Our exploration concludes in the Siberian Steppes, highlighting the area's luminescent insects and annelids. Transitioning to the marine realm, the second part of this review examines marine bioluminescent organisms. We explore this phenomenon in deep-sea jellyfish and their role in the ecosystem. We then move to Toyama Bay, Japan, where seasonal bioluminescence of dinoflagellates and ostracods present a unique case study. We also delve into the bacterial world, discussing how bioluminescent bacteria contribute to symbiotic relationships. For each organism, we contextualize its bioluminescence, providing details about its discovery, ecological function, and geographical distribution. A special focus lies on the examination of the underlying chemical mechanisms that enables these biological light displays. Concluding this review, we present a series of practical bioluminescence and chemiluminescence experiments, providing a resource for educational demonstrations and student research projects. Our goal with this review is to provide a summary of bioluminescence across the diverse ecological contexts, contributing to the broader understanding of this unique biological phenomenon and its chemical mechanisms serving researchers new to the field, educators and students alike.

Research on the Interaction Mechanism and Structural Changes in Human Serum Albumin with Hispidin Using Spectroscopy and Molecular Docking

The interaction between human serum albumin (HSA) and hispidin, a polyketide abundantly present in both edible and therapeutic mushrooms, was explored through multispectral methods, hydrophobic probe assays, location competition trials, and molecular docking simulations. The results of fluorescence quenching analysis showed that hispidin quenched the fluorescence of HSA by binding to it via a static mechanism. The binding of hispidin and HSA was validated further by synchronous fluorescence, three-dimensional fluorescence, and UV/vis spectroscopy analysis. The apparent binding constant (Ka) at different temperatures, the binding site number (n), the quenching constants (Ksv), the dimolecular quenching rate constants (Kq), and the thermodynamic parameters (∆G, ∆H, and ∆S) were calculated. Among these parameters, ∆H and ∆S were determined to be 98.75 kJ/mol and 426.29 J/(mol·K), respectively, both exhibiting positive values. This observation suggested a predominant contribution of hydrophobic forces in the interaction between hispidin and HSA. By employing detergents (SDS and urea) and hydrophobic probes (ANS), it became feasible to quantify alterations in Ka and surface hydrophobicity, respectively. These measurements confirmed the pivotal role of hydrophobic forces in steering the interaction between hispidin and HSA. Site competition experiments showed that there was an interaction between hispidin and HSA molecules at site I, which situates the IIA domains of HSA, which was further confirmed by the molecular docking simulation.

Cloning and Expression Analysis of Bioluminescence Genes in Omphalotus guepiniiformis Reveal Stress-Dependent Regulation of Bioluminescence

Bioluminescence is a type of chemiluminescence that arises from a luciferase-catalyzed oxidation reaction of luciferin. Molecular biology and comparative genomics have recently elucidated the genes involved in fungal bioluminescence and the evolutionary history of their clusters. However, most studies on fungal bioluminescence have been limited to observing the changes in light intensity under various conditions. To understand the molecular basis of bioluminescent responses in Omphalotus guepiniiformis under different environmental conditions, we cloned and sequenced the genes of hispidin synthase, hispidin-3-hydroxylase, and luciferase enzymes, which are pivotal in the fungal bioluminescence pathway. Each gene showed high sequence similarity to that of other luminous fungal species. Furthermore, we investigated their transcriptional changes in response to abiotic stresses. Wound stress enhanced the bioluminescence intensity by increasing the expression of bioluminescence pathway genes, while temperature stress suppressed the bioluminescence intensity via the non-transcriptional pathway. Our data suggested that O. guepiniiformis regulates bioluminescence to respond differentially to specific environmental stresses. To our knowledge, this is the first study on fungal bioluminescence at the gene expression level. Further studies are required to address the biological and ecological meaning of different bioluminescence responses in changing environments, and O. quepiniiformis could be a potential model species.

Transcriptome Analysis Reveals the Putative Polyketide Synthase Gene Involved in Hispidin Biosynthesis in Sanghuangporus sanghuang

Hispidin is an important styrylpyrone produced by Sanghuangporus sanghuang. To analyze hispidin biosynthesis in S. sanghuang, the transcriptomes of hispidin-producing and non-producing S. sanghuang were determined by Illumina sequencing. Five PKSs were identified using genome annotation. Comparative analysis with the reference transcriptome showed that two PKSs (ShPKS3 and ShPKS4) had low expression levels in four types of media. The gene expression pattern of only ShPKS1 was consistent with the yield variation of hispidin. The combined analyses of gene expression with qPCR and hispidin detection by liquid chromatography-mass spectrometry coupled with ion-trap and time-of-flight technologies (LCMS-IT-TOF) showed that ShPKS1 was involved in hispidin biosynthesis in S. sanghuang. ShPKS1 is a partially reducing PKS gene with extra AMP and ACP domains before the KS domain. The domain architecture of ShPKS1 was AMP-ACP-KS-AT-DH-KR-ACP-ACP. Phylogenetic analysis shows that ShPKS1 and other PKS genes from Hymenochaetaceae form a unique monophyletic clade closely related to the clade containing Agaricales hispidin synthase. Taken together, our data indicate that ShPKS1 is a novel PKS of S. sanghuang involved in hispidin biosynthesis.

A new discovery of the bioluminescent terrestrial snail genus Phuphania (Gastropoda: Dyakiidae)

The mysterious world of the bioluminescent molluscs in terrestrial ecosystems is mesmerizing, but Quantula striata was previously the only terrestrial mollusc known to be luminescent. Here, we document the new discovery of bioluminescence in four land snails, namely Phuphania crossei, P. globosa, P. carinata, and P. costata. Our observations establish clearly that these four species of Phuphania produce a continuous greenish light from the light-emitting cells located within the mantle and the foot, and that its bright luminescence is intracellular and is not due to any luminous secretion. Although both Quantula and Phuphania can produce a green light, the luminescence patterns are different. The luminescence displayed by Quantula is rhythmical blinking or flashing, while Phuphania glows continuously. In addition, the bioluminescence in Q. weinkauffiana is confirmed, which is similar to that in the related species, Q. striata.

The Luminous Fungi of Japan

Luminous fungi have long attracted public attention in Japan, from old folklore and fiction to current tourism, children's toys, games, and picture books. At present, 25 species of luminous fungi have been discovered in Japan, which correspond to approximately one-fourth of the globally recognized species. This species richness is arguably due to the abundant presence of mycophiles looking to find new mushroom species and a tradition of night-time activities, such as firefly watching, in Japan. Bioluminescence, a field of bioscience focused on luminous organisms, has long been studied by many Japanese researchers, including the biochemistry and chemistry of luminous fungi. A Japanese Nobel Prize winner, Osamu Shimomura (1928-2018), primarily focused on the bioluminescence system of luminous fungi in the latter part of his life, and total elucidation of the mechanism was finally accomplished by an international research team with representatives from Russia, Brazil, and Japan in 2018. In this review, we focused on multiple aspects related to luminous fungi of Japan, including myth, taxonomy, and modern sciences.

A novel mushroom (Auricularia polytricha) glycoprotein protects against lead-induced hepatoxicity, promotes lead adsorption, inhibits organ accumulation of lead, upregulates detoxifying proteins, and enhances immunoregulation in rats

Introduction

Lead is a ubiquitous environmental and industrial pollutant. Its nonbiodegradable toxicity induces a plethora of human diseases. A novel bioactive glycoprotein containing 1.15% carbohydrate, with the ability of adsorbing lead and effecting detoxification, has been purified from Auricularia polytricha and designated as APL. Besides, its mechanisms related to regulation of hepatic metabolic derangements at the proteome level were analyzed in this study.

Methods

Chromatographic techniques were utilized to purify APL in the current study. For investigating the protective effects of APL, Sprague-Dawley rats were given daily intraperitoneal injections of lead acetate for establishment of an animal model, and different dosages of APL were gastrically irrigated for study of protection from lead detoxification. Liver samples were prepared for proteomic analyses to explore the detoxification mechanisms.

Results and discussion

The detoxifying glycoprotein APL displayed unique molecular properties with molecular weight of 252-kDa, was isolated from fruiting bodies of the edible fungus A. polytricha. The serum concentrations of lead and the liver function biomarkers aspartate and alanine aminotransferases were significantly (p<0.05) improved after APL treatment, as well as following treatment with the positive control EDTA (300 mg/kg body weight). Likewise, results on lead residue showed that the clearance ratios of the liver and kidneys were respectively 44.5% and 18.1% at the dosage of APL 160 mg/kg, which was even better than the corresponding data for EDTA. Proteomics disclosed that 351 proteins were differentially expressed following lead exposure and the expression levels of 41 proteins enriched in pathways mainly involved in cell detoxification and immune regulation were normalized after treatment with APL-H. The results signify that APL ameliorates lead-induced hepatic injury by positive regulation of immune processing, and suggest that APL can be applied as a therapeutic intervention of lead poisoning in clinical practice. This report represents the first demonstration of the protective action of a novel mushroom protein on lead-elicited hepatic toxicity.

Resources of Iranian agarics (Basidiomycota) with an outlook on their antioxidant potential

Agaric fungi are an important group of macromycetes with diverse ecological and functional properties, yet are poorly studied in many parts of the world. Here, we comprehensively analyzed 558 agaric species in Iran to reveal their resources of edible and poisonous species as well as their ecological guilds and luminescence potential. We also made a thorough survey of the antioxidant activity of the species. Phylogenetic relationships were reconstructed based on nuclear ribosomal LSU and ITS sequences. Our results reveal that agarics of Iran comprise about 189 edible, 128 poisonous, 254 soil saprotrophic, 172 ectomycorrhizal, 146 wood-inhabiting, 18 leaf/litter-inhabiting, 9 parasitic, and 19 luminescent species. Twenty percent of the Iranian agaric species possess antioxidant activity, phylogenetically distributed in four orders and 21 agaric families. About 5% of the antioxidant species can be considered strong antioxidants, many of which are also edible and could be utilized to develop functional foods. This is the first study combining phylogeny and antioxidant potential of agaric mushrooms in a large scale, and the obtained results would guide the selection of agaric taxa to be examined in the future for taxonomic revisions, biotechnological applications, and applied phylogeny studies.

Cultivation of Inonotus hispidus in Stirred Tank and Wave Bag Bioreactors to Produce the Natural Colorant Hispidin

Hispidin (6-(3,4-dihydroxystyrl)-4-hydroxy-2-pyrone) production in submerged cultured mycelia of the basidiomycete Inonotus hispidus was doubled in shake flasks through irradiation with white light. The daily addition of 1 mM hydrogen peroxide as a chemical stressor and a repeated supplementation of the shake flask cultures with 2 mM caffeic acid, a biogenetic precursor, further increased the hispidin synthesis. These cultivation conditions were combined and applied to parallel fermentation trials on the 4 L scale using a classical stirred tank bioreactor and a wave bag bioreactor. No significant differences in biomass yield and colorant production were observed. The hispidin concentration in both bioreactors reached 5.5 g·L−1, the highest ever published. Textile dyeing with hispidin was successful, but impeded by its limited light stability in comparison to industrial dyes. However, following the idea of sustainability and the flawless toxicity profile, applications in natural cosmetics, other daily implements, or even therapeutics appear promising.

Finding the Light Emission Stimulator of Neonothopanus nambi Basidiomycete and Studying Its Properties

A stimulator of light emission of the fungus was found in an aqueous extract from mycelium of the luminous basidiomycete Neonothopanus nambi after its treatment with β-glucosidase. The addition of the extract to the luminous mycelium increases the level of light emission from several times to 1.5 orders of magnitude or more. The luminescence stimulator is a low-molecular-weight thermostable compound: it is detected in the permeate after filtering the extract through a 10-kDa cutoff membrane and it retains the stimulating effect after heat treatment at 100°C for 5 min. In the absorption spectrum of the aqueous sample of the stimulator, two main peaks are observed in the shortwave region (205 and 260 nm) and a shoulder in the range of 350-370 nm can be seen. The luminescence stimulator exhibits blue fluorescence with an emission maximum at 440 nm when excited at 360 nm. It was established that the luminescence-stimulating component is not a substrate (or its precursor) of the luminescent system of the N. nambi fungus.

Luciferins Under Construction: A Review of Known Biosynthetic Pathways

Bioluminescence, or the ability of a living organism to generate visible light, occurs as a result of biochemical reaction where enzyme, known as a luciferase, catalyzes the oxidation of a small-molecule substrate, known as luciferin. This advantageous trait has independently evolved dozens of times, with current estimates ranging from the most conservative 40, based on the biochemical diversity found across bioluminescence systems (Haddock et al., 2010) to 100, taking into account the physiological mechanisms involved in the behavioral control of light production across a wide range of taxa (Davis et al., 2016; Verdes and Gruber, 2017; Bessho-Uehara et al., 2020a; Lau and Oakley, 2021). Chemical structures of ten biochemically unrelated luciferins and several luciferase gene families have been described; however, a full biochemical pathway leading to light emission has been elucidated only for two: bacterial and fungal bioluminescence systems. Although the recent years have been marked by extraordinary discoveries and promising breakthroughs in understanding the molecular basis of multiple bioluminescence systems, the mechanisms of luciferin biosynthesis for many organisms remain almost entirely unknown. This article seeks to provide a succinct overview of currently known luciferins’ biosynthetic pathways.

RNA-Seq analysis of the blue light-emitting Orfelia fultoni (Diptera: Keroplatidae) suggest photoecological adaptations at the molecular level

Bioluminescence in Diptera is found in the Keroplatidae family, within Arachnocampininae and Keroplatinae subfamilies, with reported occurrences in Oceania, Eurasia, and Americas. Larvae of Orfelia fultoni, which inhabit stream banks in the Appalachian Mountains, emit the bluest bioluminescence among insects, using it for prey attraction, similarly to Arachnocampa spp. Although bioluminescence has a similar prey attraction function, the systems of Arachonocampininae and Keroplatinae subfamilies are morphologically/biochemically distinct, indicating different evolutionary origins. To identify the possible coding genes associated with physiological control, ecological adaptations, and origin/evolution of bioluminescence in the Keroplatinae subfamily, we performed the RNA-Seq analysis of O. fultoni larvae during day and night and compared it with the transcriptomes of Arachnocampa luminosa, and reanalyzed the previously published proteomic data of O. fultoni against the RNA-Seq dataset. The abundance of chaperones/heat-shock and hexamerin gene products at night and in luciferase enriched fractions supports their possible association and participation in bioluminescence. The low diversity of copies/families of opsins indicate a simpler visual system in O. fultoni. Noteworthy, gene products associated with silk protein biosynthesis in Orfelia were more similar to Lepidoptera than to the Arachnocampa, indicating that, similarly to the bioluminescent systems, at some point, the biochemical apparatus for web construction may have evolved independently in Orfelia and Arachnocampa.

Glowing plants can light up the night sky? A review

Luminescence, a physical phenomenon that producing cool light in vivo, has been found in bacteria, fungi, and animals but not yet in terrestrial higher plants. Through genetic engineering, it is feasible to introduce luminescence systems into living plant cells as biomarkers. Recently, some plants transformed with luminescent systems can glimmer in darkness, which can be observed by our naked eyes and provides a novel lighting resource. In this review, we summarized the bioassay development of luminescence in plant cells, followed by exampling the successful cases of glowing plants transformed with diverse luminescent systems. The potential key factors to design or optimize a glowing plant were also discussed. Our review is useful for the creation of the optimized glowing plants, which can be used not only in scientific research, but also as promising substitutes of artificial light sources in the future.

Screening for proteins related to the biosynthesis of hispidin and its derivatives in Phellinus igniarius using iTRAQ proteomic analysis

Background

Hispidin (HIP) and its derivatives, a class of natural fungal metabolites, possess complex chemical structures with extensive pharmacological activities. Phellinus igniarius, the most common source of HIP, can be used as both medicine and food. However, the biosynthetic pathway of HIP in P. igniarius remains unclear and we have a limited understanding of the regulatory mechanisms related to HIP. In this work, we sought to illustrate a biosynthesis system for hispidin and its derivatives at the protein level.

Results

We found that tricetolatone (TL) is a key biosynthetic precursor in the biosynthetic pathway of hispidin and that its addition led to increased production of hispidin and various hispidin derivatives. Based on the changes in the concentrations of precursors and intermediates, key timepoints in the biosynthetic process were identified. We used isobaric tags for relative and absolute quantification (iTRAQ) to study dynamic changes of related proteins in vitro. The 270 differentially expressed proteins were determined by GO enrichment analysis to be primarily related to energy metabolism, oxidative phosphorylation, and environmental stress responses after TL supplementation. The differentially expressed proteins were related to ATP synthase, NAD binding protein, oxidoreductase, and other elements associated with electron transfer and dehydrogenation reactions during the biosynthesis of hispidin and its derivatives. Multiple reaction monitoring (MRM) technology was used to selectively verify the iTRAQ results, leading us to screen 11 proteins that were predicted to be related to the biosynthesis pathways.

Conclution

These findings help to clarify the molecular mechanism of biosynthesis of hispidin and its derivatives and may serve as a foundation for future strategies to identify new hispidin derivatives.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-021-02134-0.

Multi-level convergence of complex traits and the evolution of bioluminescence

Evolutionary convergence provides natural opportunities to investigate how, when, and why novel traits evolve. Many convergent traits are complex, highlighting the importance of explicitly considering convergence at different levels of biological organization, or 'multi-level convergent evolution'. To investigate multi-level convergent evolution, we propose a holistic and hierarchical framework that emphasizes breaking down traits into several functional modules. We begin by identifying long-standing questions on the origins of complexity and the diverse evolutionary processes underlying phenotypic convergence to discuss how they can be addressed by examining convergent systems. We argue that bioluminescence, a complex trait that evolved dozens of times through either novel mechanisms or conserved toolkits, is particularly well suited for these studies. We present an updated estimate of at least 94 independent origins of bioluminescence across the tree of life, which we calculated by reviewing and summarizing all estimates of independent origins. Then, we use our framework to review the biology, chemistry, and evolution of bioluminescence, and for each biological level identify questions that arise from our systematic review. We focus on luminous organisms that use the shared luciferin substrates coelenterazine or vargulin to produce light because these organisms convergently evolved bioluminescent proteins that use the same luciferins to produce bioluminescence. Evolutionary convergence does not necessarily extend across biological levels, as exemplified by cases of conservation and disparity in biological functions, organs, cells, and molecules associated with bioluminescence systems. Investigating differences across bioluminescent organisms will address fundamental questions on predictability and contingency in convergent evolution. Lastly, we highlight unexplored areas of bioluminescence research and advances in sequencing and chemical techniques useful for developing bioluminescence as a model system for studying multi-level convergent evolution.

Fungal Light Emitter: Understanding Its Chemical Nature and pH-Dependent Emission in Water Solution

Fungal bioluminescence is a fascinating natural process, standing out for the continuous conversion of chemical energy into light. The structure of fungal oxyluciferin (light emitter) was proposed in 2017, being different and more complex than other oxyluciferins. The complexity of fungal oxyluciferin arises from diverse equilibria such as keto/enol tautomerization or deprotonation equilibria of four titratable groups. For this reason, still some crucial details of its structure remain unexplored. To obtain further structural information, a combined experimental and computational study of natural and three synthetic fungal oxyluciferin analogues has been performed. Here, we state the most stable chemical form of fungal oxyluciferin regarding its keto and enol tautomers, in the ground and excited states. We propose the (3Z,5E)-6-(3,4-dihydroxyphenyl)-4-hydroxy-2-oxohexa-3,5-dienoic acid form as the light emitter (fluorescent state) in water solution. Moreover, we show that chemical modifications on fungal oxyluciferin can affect the relative stability of the conformers. Furthermore, we show the clear effect of pH on emission. General conclusions about the role of these titratable groups in emission modulation have been drawn, such as the key role of dihydroxyphenyl deprotonation. This study is key to further analyze the properties of fungal bioluminescence and propose novel synthetic analogues.

Two forms of substrate for the bioluminescent reaction in three species of basidiomycetes

The luminescent response of the enzymatic system of Armillaria borealis on the cold and hot extracts from cell-free culture liquids of Inonotus obliquus, Pholiota sp. and A. borealis was examined. The greatest influence on the light emission produced by the luminescent system of A. borealis was provided by the temperature at which the probes were prepared for assay. Boiling a culture liquid on water bath for a few minutes promoted a multifold increase in the luminescence. The results of luminescence assay suggest that the substance involved in the bioluminescent reaction in higher fungi is presented in culture liquids and mycelia in two forms. In one form, it is ready to interact with the enzymatic system and in the second form, it becomes accessible for the reaction after heat treatment. The pool of thermoactivated substance was found to be much large than the amount of the ready accessible one. We suggest that predecessors of hispidin, which is fungal luciferin precursor, are responsible for this phenomenon. They are not involved in bioluminescence at their original state and are converted into the substrate under the influence of high temperature.

Bioluminescence expression during the transition from mycelium to mushroom in three North American Armillaria and Desarmillaria species

Unlike most bioluminescent fungi, mycelia of Armillaria and Desarmillaria are constitutively bioluminescent while mature mushrooms are not. The absence of the luciferin, 3-hydroxyhispidin, and its precursor hispidin in mature mushrooms have been proposed to explain the lack of bioluminescence from Armillaria mushrooms. Using three North American species, A. gallica, A. mellea and D. tabescens (syn., Armillaria tabescens), we documented a decline in luminescence of ten fold during the transition from mycelia to, immature mushrooms (i.e., pins) for the two Armillaria species. As pins matured, luminescence declined by an additional two or three orders of magnitude. Lower initial luminescence of D. tabescens mycelia declined to negligible levels during mushroom development. Further, light production was localized in the gills and lower stipe of A. mellea mushrooms. The decline in luminescence during mushroom formation was reversed by addition of hispidin to stipe or gills which significantly enhanced luminescence by one and three orders of magnitude, respectively. We conclude that the modulation of Armillaria and Desarmillaria luminescence is achieved by luciferin availability early in mushroom development. However, since the temporal regulation of bioluminescence differs between Armillaria species and other genera, we conclude that bioluminescence in Armillaria is under unique selective pressures.

Trans-3-hydroxyhispidin is not an actual bioluminescence substrate in pileus gills of the luminous fungus Mycena chlorophos

Mycena chlorophos is a species of molecular oxygen-dependent bioluminescent fungus, and its pileus gills emit bright green light. The chemical mechanisms underlying this bioluminescence phenomenon are not yet understood. An enzyme (luciferase) producing light from trans-3-hydroxyhispidin is present in M. chlorophos pileus gills. However, it is unclear whether trans-3-hydroxyhispidin is an actual bioluminescence substrate (luciferin) in the natural bioluminescence of M. chlorophos. In the present study, this question is resolved. It was clearly demonstrated that the trans-3-hydroxyhispidin analog trans-3-hydroxybisnoryangonin significantly inhibited the artificial luminescence induced by the addition of trans-3-hydroxyhispidin to living pileus gills but did not inhibit natural bioluminescence in living pileus gills. This inhibition was due to the reaction of trans-3-hydroxybisnoryangonin with luciferase for trans-3-hydroxyhispidin. Even though trans-4-aminocinnamic acid is known to inhibit natural bioluminescence in living pileus gills, in the present study, trans-4-aminocinnamic acid did not influence the artificial luminescence via trans-3-hydroxyhispidin in the presence of luciferase for trans-3-hydroxyhispidin. These inconsistencies between the natural bioluminescence and the artificial luminescence of trans-3-hydroxyhispidin indicate that trans-3-hydroxyhispidin is not an actual luciferin in natural bioluminescence. Trans-3,4-dihydroxycinnamic acid is generally known to be an intermediate in trans-3-hydroxyhispidin biosynthesis. The artificial luminescence induced by the addition of trans-3,4-dihydroxycinnamic acid to living pileus gills was not inhibited by trans-3-hydroxybisnoryangonin. Therefore, trans-3,4-dihydroxycinnamic acid does not contribute to the luminescence involving trans-3-hydroxyhispidin in living pileus gills.

A bioluminescent system of fungi: prospects for application in medical research

Bioluminescence is chemical oxidation of a small luciferin molecule by air catalyzed by luciferase and accompanied by the emission of photons in the visible spectrum. This reaction is used in bioluminescent bioimaging, the method for the visualization of organism’s interior. Bioimaging is a popular tool used in medical research. However, it has an unfortunate drawback: it requires introduction of external luciferin to the system before every experiment. In this work we discuss a possibility of developing an autonomous luminescent system in eukaryotes based on the bioluminescent system of higher fungi.

Chemi- and Bioluminescence of Cyclic Peroxides

Bioluminescence is a phenomenon that has fascinated mankind for centuries. Today the phenomenon and its sibling, chemiluminescence, have impacted society with a number of useful applications in fields like analytical chemistry and medicine, just to mention two. In this review, a molecular-orbital perspective is adopted to explain the chemistry behind chemiexcitation in both chemi- and bioluminescence. First, the uncatalyzed thermal dissociation of 1,2-dioxetane is presented and analyzed to explain, for example, the preference for triplet excited product states and increased yield with larger nonreactive substituents. The catalyzed fragmentation reaction and related details are then exemplified with substituted 1,2-dioxetanone species. In particular, the preference for singlet excited product states in that case is explained. The review also examines the diversity of specific solutions both in Nature and in artificial systems and the difficulties in identifying the emitting species and unraveling the color modulation process. The related subject of excited-state chemistry without light absorption is finally discussed. The content of this review should be an inspiration to human design of new molecular systems expressing unique light-emitting properties. An appendix describing the state-of-the-art experimental and theoretical methods used to study the phenomena serves as a complement.