Theoretical Study Of Multicolour Bioluminescence

With the development of the natural science, and the deep investigation innature, from deep sea to land, bioluminescence phenomenon has attracted theattention of both biologists and chemists. In these bioluminescence species, jellyfishand firefly are the most well-known and studied, and their research results areapplied in many areas. More and more application demands inspire scientists todeeply understand their bioluminescence mechanism and bioluminescenceproperties.The main researches are summarized as follows:1. The Dynamics Simulation and Quantum Calculation Investigation aboutLuminescence Mechanism of CoelenteramideThe dynamics simulation and quantum chemical calculation are employed toinvestigate spectrum properties of deprotonation process of coelenteramide and twofinal states neutral state and phenolate anion. According to the calculation results,theoretical evidence supporting the luminescence mechanism hypothesis is proposedin a significant bioluminescence process. In vivo of marine bioluminescentorganisms, if the protein motion provides the conditions for the deprotonation ofcoelenteramide in some protein molecules, the phenolate anion is completelydeprotonated coelenteramide as an emitter in these protein molecules and emitsfluorescence assigned to the lower energy peak. And another emitter which thecondition of deprotonation does not meet, the fluorescence is produced by the neutralstate of coelenteramide and assigned to the higher energy peak. The energydifference decreases gradually when the proton of coelenteramide graduallyapproaches to His22. For phenolate anion and neutral state, electronic clouddistributions between their each frontier molecular orbitals HOMO and LUMO havehigh overlapping volume. The molecular electrostatic potential indicates that for phenolate anion, the oxygen atom after deprotonation has greater electron densitywhich is good for formation hydrogen bonds with amino acids in the environment.2. The Effect of Micro-Environment on Luminescence of Aequorin: TheRole of Amino Acids and Explicit Water Molecules on Spectroscopic Propertiesof CoelenteramideDespite the fact that the luminescence reaction mechanism of aequorin has beenintensively investigated, details in luminescence such as the effect of importantamino acids residues and explicit water molecules on spectroscopic properties ofcoelenteramide remain unclear. In this work, the effect of amino acids residuesHis16, Tyr82, Trp86, Phe113, Trp129, Tyr132, explicit water molecules Wat505andWat405on the spectral properties of CLM-has been studied by CAM-B3LYP, TDM06L and TD CAM-B3LYP methods hydrophobic environment and aqueoussolution. In hydrophobic environment, the amino acids or water molecules have nosignificant effect on the absorption. Trp86moves close to CLM-changes thehydrogen bond network, and thus, the spectral properties is significantly affected bythe hydrogen bonds between His16H++Trp86+Tyr82and CLM-. The hydrogenbonds between Trp86, Tyr82and CLM-upshift the excited energy and help emissionspectra shift to blue region. Therefore, it is concluded that His16H++Trp86+Tyr82modify the emission spectra. The molecular electrostatic potential indicated that thegreater electron density is located at the oxygen atom of6-p-hydroxyphenyl group ofCLM-, and it is in favor of formation hydrogen bond with His16H++Trp86+Tyr82. Itis a critical condition for the modification of emission spectra. It is hoped that theresults can help to understand the interactions between emitter and amino acids inthe micro environment, and the spectral tuning of bioluminescence by mutation ofamino acids of aequorin.3. Theoretical Study of the Electronic Spectral Property of FireflyOxyluciferin AnaloguesIn this paper, a series of firefly oxyLuciferin analogues are designed, in which theN and S atoms of benzothiazole of firefly oxyluciferin are substituted by other atoms. In aqueous solution and virtual protein environment, the absorption and emissionspectrum were calculated by TD B3LYP/6-31+G (d). The results of the calculationindicated that the absorption spectra of complexes with the O atom at X1-site shift tothe blue than that with the S atom, while the ones of complexes which the S atom isreplaced by the N atom shift to the red. The six complexes have similar orbitaldistribution, the overlapping volume between HOMO and LUMO is higher. Thatbenefits to maintain high fluorescence efficiency. Deprotonation can enhance the πorbital component of benzene fragment and make emission spectra shift to red. Thuselectronic transition probability can be improved. Replaced by different atoms at X1and X2, the emission spectra can be adjusted to move to long wave up to44nm andmove to short wave up to41nm (in virtual protein environment). The emissionwavelength range of six complexes is wide. So they can be used in biological imagingas new potential chemical luminescent material.4. TD DFT investigation of fluorescence properties of luciferin andoxyluciferin analogs bearing an amino groupChemical origin of high chemiluminescence efficiency of firefly luciferin remainsan intriguing subject. Developing more efficient fluorescent marked compounds based onthe firefly luciferin is in full swing for application in gene expression and gene regulation,and imaging of live tissues fields. Thus, a series of luciferin analogues bearing an aminogroup of aminoluciferin (AL), quinolylaminoluciferin (QAL), naphthylaminoluciferin(NAL), coumarylaminoluciferin (CAL) and anthrylaminoluciferin (AAL),pyrenylaminoluciferin (PAL) and corresponding keto form oxides were studied in this work,and the ground and excited state properties of them have been calculated by using timedependent density functional (TD DFT)methods in the gas phase, dimethylsulfoxide(DMSO)solution and hydrophobic environment. The results suggested that replacingaminobenzothiazole moiety of firefly luciferin with the larger rigid moieties, theabsorption spectra shift to the blue. Bio-heterojunction concept was employed toexplain the higher degree of spatial overlap of corresponding orbitals for CAOL,AAOL and PAOL, an important factor to be of beneficial to enhance flurorescence efficiency. In order to further explain the high flurorescence efficiency of CAOL, theprocess of nonradiative decay is also investigated. Comparing the energy difference ofthe corresponding singlet and triplet excited states in intersystem crossing and internalconversion, the reasons is qualitatively explained for the high flurorescence efficiencyof CAOL. The investigation result for their emission spectra suggested that theemission maximum of AAOL is similar to firefly in nature. The influence ofsubstituent on fluorescent emission was discussed.