Module 5 Milestone Rough Draft - Kristen Brown

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Brown 1 Kristen Brown Doreena Patrick CHM-101-Q2828 11/13/2023 Milestone 5 Rough Draft Luciferin The term ‘Luciferin’ derives from the Latin word Lucifer, which translates into “Light- Bearer.” This is the perfect way to describe this bioluminescent compound that so often goes unappreciated, mostly due to the creepy crawlies the compound is often found in. Luciferins are organic compounds that vary in chemical structure. The luciferin compound found in fireflies is different from what is found in luminescent bacteria (Britannica, 2010). This key aspect highlights the diversity and complexity of organic compounds. Luciferin is a fascinating compound that can help illustrate several key concepts in chemistry, particularly in the fields of organic chemistry, biochemistry, and physical chemistry. Bioluminescence is often revered as a wonder of the world, and rightfully so. The type of luciferin I will be identifying is firefly luciferin (C 11 H 8 N 2 O 3 S 2 ). Luciferin is the light omitting compound found in fireflies. To get a bioluminescent reaction, an enzyme found in the firefly, called luciferase, bonds together with the substrate (luciferin) and oxygen, creating the bioluminescent reaction humans can physically see. Luciferase acts as the catalyst or accelerator to the reaction (Shimomura, O., & Yampolsky, I. L., 2019, page 5). The luciferin- luciferase reaction can be classified as a redox reaction since it involves the transfer of electrons

Brown 2 between luciferin and oxygen. Most bioluminescence is created by oxygen reactions (Haddock, S. H., Moline, M. A., & Case, J. F., 2010, page 5). When air (oxygen) goes into the firefly’s body, it reacts with the organic compound luciferin. This causes luciferin to oxidize and form oxyluciferin, and releases energy in the process. At this point, the reaction is sped up by the enzyme known as luciferase. As a result, this transformation produces an excited state that releases a photon of light right before decaying into its ground state. The chemical reaction takes place in two steps. The first: luciferin + ATP → luciferyl adenylate + PP i . Then finally the second reaction: luciferyl adenylate + O 2 → oxyluciferin + AMP + light. Here, luciferin and ATP are the reactants, luciferase is the catalyst, and oxyluciferin, AMP, and light are the products. Bioluminescence is produced during an exothermic chemical reaction. In an exothermic reaction, the excess energy is released to the environment. This is often in the form of heat. However, the excess energy for fireflies is light. Safety considerations for handling luciferase and luciferin include the avoidance of raising up dust and breathing the dust. Adequate ventilation is needed to handle the compound. Luciferase can function in two different pathways which include a bioluminescence pathway and a CoA- ligase pathway. In both pathways, luciferase initially catalyzes an adenylation reaction with MgATP. However, in the CoA-ligase pathway, CoA can displace AMP to form luciferyl CoA. This alternate reaction illustrates the versatility of the luciferase enzyme. To break down the bioluminescence reaction even further, bioluminescent reactions involving luciferin-luciferase are a chemiluminescent process, where chemical energy is converted into light energy. This conversion can be understood in terms of the principles of quantum mechanics and the behavior of electrons in molecules. This reaction is an example of an enzyme-catalyzed reaction, which is a fundamental concept in biochemistry. Luciferins require

Brown 3 ATP (adenosine triphosphate) for light emission, which ties into the central role of ATP in energy transfer within cells. Firefly luciferases have been used extensively in biotechnology and are of significant economic importance due to their use in scientific research and medicine regarding imaging microscopy. It is used in vivo imaging, allowing for non-invasive detection of images and in molecular imaging, illustrating the principle of energy flow from chemical potential energy (in the form of ATP) to light energy. The compound is harvested specifically for this purpose, contributing to its economic value. The molecular description of luciferin is very simple as compared to most other complex compounds. There is not much that goes into firefly luciferin’s existence, but it also is something that scientists are still trying to explain, which further gives it a veil of mystery. Here are the things that are known: it is known that the weight of firefly luciferin is 280.32 g/mol, with a density of 1.8 g/cm 3 , and a boiling point of approximately 473.8°C at 760 mmHg. Its constituent elements consist of carbon, hydrogen, nitrogen, oxygen, and sulfur. Luciferin- Luciferase produces cold light at 490 nm. In some cases, the color of luminescence is altered by an energy transfer to fluorescent protein that interacts with the luciferase (Lee et al., 2019). Firefly luciferin, like many organic compounds, contains covalent bonds. A firefly luciferin molecule includes single and double bonds, as well as aromatic systems in its benzothiazole and thiazoline rings (Shimomura, O., & Yampolsky, I. L., 2019, page 8). Due to Bioluminescence is produced during an exothermic chemical reaction. In an exothermic reaction, the excess energy is released to the environment. This is often in the form of heat. However, the excess energy for fireflies is light. Firefly luciferin has many varying aspects to it, due to the specific structure of the molecule itself. The polarity of firefly luciferin, much like the fluorescence, is one of those

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Brown 4 specific aspects. However, it does contain polar functional groups, which includes a carboxylic acid group, contributing to its overall polarity. Solubility of luciferin is the same principle, differing by the specific form of the compound. With that being said, the potassium salt of firefly luciferin is soluble up to 60 mg/ml, while the sodium salt is soluble up to 100 mg/ml. The free acid form of firefly luciferin is not soluble in water, but it is soluble in methanol at 10 mg/ml and in DMSO (Dimethyl Sulfoxide) at 50 mg/ml. The reactivity of firefly luciferin is specific to the enzyme luciferase. This specificity is crucial for the bioluminescent reaction to occur. If a similar compound were more or less reactive, it could potentially alter the rate or efficiency of the bioluminescent reaction. For example, some luciferin analogues produce luminescence in different wavelengths and allow for the parallel detection of different target molecules. The usage of luciferin does not change significantly in different physical states or when mixed with other compounds at different concentrations. However, the solubility of luciferin can affect its availability for the bioluminescent reaction. Changes in reaction temperature could potentially affect the rate of the bioluminescent reaction. Lower temperatures result in slower flash rates, and extreme temperatures could potentially denature the luciferase enzyme, making the reaction unsafe, too slow, or unstable. The relatively small molecular size of luciferin allows it to easily diffuse through biological membranes, which is crucial for its role in bioluminescence. If a similar compound had a larger molecular weight, it might not be able to diffuse as easily, which could potentially limit its range of uses.

Brown 5 Works Cited Britannica, T. Editors of Encyclopaedia (2010, August 18). luciferin. Encyclopedia Britannica. https://www.britannica.com/science/luciferin Haddock, S. H., Moline, M. A., & Case, J. F. (2010). Bioluminescence in the sea. Annual Review of Marine Science, 2, 443-493. https://www.researchgate.net/publication/49667852_Bioluminescence_in_the_Sea Shimomura, O., & Yampolsky, I. L. (2019). Bioluminescence: Chemical Principles and Methods. World Scientific. https://worldscientific.com/doi/pdf/10.1142/9789813277113_0001 Lee, J., Müller, F., & Visser, A. J. W. G. (2019). The Sensitized Bioluminescence Mechanism of Bacterial Luciferase. Photochemistry and photobiology, 95(3), 679–704. https://pubmed.ncbi.nlm.nih.gov/30485901/