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Wang R, Ma D, Kong X, Peng F, Cao X, Zhao Y, Lu C, Shi W. Metastable Supramolecular Assembly of Simple Monomers Enabled by Confinement: Towards Aqueous Phase Room Temperature Phosphorescence. Angew Chem Int Ed Engl 2024; 63:e202409162. [PMID: 38860443 DOI: 10.1002/anie.202409162] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2024] [Accepted: 06/10/2024] [Indexed: 06/12/2024]
Abstract
The application of supramolecular assembly (SA) with room temperature phosphorescence (RTP) in aqueous phase has the potential to revolutionize numerous fields. However, using simple molecules with crystalline RTP to construct SA with aqueous phase RTP is hardly possible from the standpoint of forces. The reason lies in that the transition from crystal to SA involves a structure transformation from highly stable to more dynamic state, leading to increased non-radiative deactivation pathways and silent RTP signal. Here, with the benefit of the confinement from the layered double hydroxide (LDH), various simple molecules (benzene derivatives) can successfully form metastable SA with aqueous phase RTP. The maximum of RTP lifetime and efficiency can reach 654.87 ms and 5.02 %, respectively. Mechanistic studies reveal the LDH energy trap can strengthen the intermolecular interaction, providing the prerequisite for the existence of metastable SA and appearance of aqueous phase RTP. The universality of this strategy will usher exploration into other multifunctional monomer, facilitating the development of SAs with aqueous phase RTP.
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Affiliation(s)
- Ruixing Wang
- State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, 15 Beisanhuan East Road, P. Box 98, 100029, Beijing, P. R. China
| | - Da Ma
- State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, 15 Beisanhuan East Road, P. Box 98, 100029, Beijing, P. R. China
| | - Xianggui Kong
- State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, 15 Beisanhuan East Road, P. Box 98, 100029, Beijing, P. R. China
| | - Feifei Peng
- State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, 15 Beisanhuan East Road, P. Box 98, 100029, Beijing, P. R. China
| | - Xiaoqing Cao
- State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, 15 Beisanhuan East Road, P. Box 98, 100029, Beijing, P. R. China
| | - Yufei Zhao
- State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, 15 Beisanhuan East Road, P. Box 98, 100029, Beijing, P. R. China
| | - Chao Lu
- State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, 15 Beisanhuan East Road, P. Box 98, 100029, Beijing, P. R. China
| | - Wenying Shi
- State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, 15 Beisanhuan East Road, P. Box 98, 100029, Beijing, P. R. China
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Vinod K, Jadhav SD, Hariharan M. Room Temperature Phosphorescence in Crystalline Iodinated Eumelanin Monomer. Chemistry 2024; 30:e202400499. [PMID: 38502668 DOI: 10.1002/chem.202400499] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2024] [Revised: 03/01/2024] [Accepted: 03/19/2024] [Indexed: 03/21/2024]
Abstract
We report the room temperature phosphorescence upon iodination on a crystalline eumelanin monomer with shielded hydroxyl moieties, ethyl 5,6-dimethoxyindole-2-carboxylate (DMICE). Ultrafast intersystem crossing (ISC) is observed in the iodinated (IDMICE) as well as brominated (BDMICE) analogues of the eumelanin monomer derivative in solution. The triplet quantum yields (φT) and intersystem crossing rates (kISC) of the halogenated eumelanin derivatives areφ T B D M I C E ${{\phi{} }_{T}^{BDMICE}}$ =25.4±1.1 %;k I S C B D M I C E ${{k}_{ISC}^{BDMICE}}$ =1.95×109 s-1 andφ T I D M I C E ${{\phi{} }_{T}^{IDMICE}}$ =59.1±1.6 %;k I S C I D M I C E = ${{k}_{ISC}^{IDMICE}=}$ 1.36×1010 s-1, as monitored using transient absorption spectroscopy. Theoretical calculations based on nuclear ensemble method reveal that computed kISC and spin-orbit coupling matrix elements for eumelanin derivatives are larger for IDMICE relative to BDMICE. The halogen and π-π interactions, with distinct excitonic coupling and higher ISC rate promote phosphorescence in IDMICE molecular crystals. Accessing triplet excited states and resultant photoluminescence through structural modification of eumelanin scaffolds paves way for exploring the versatility of eumelanin-inspired molecules as bio-functional materials.
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Affiliation(s)
- Kavya Vinod
- School of Chemistry, Indian Institute of Science Education and Research Thiruvananthapuram (IISER TVM), Maruthamala P.O., Vithura, Thiruvananthapuram, 695551, Kerala, India
| | - Sohan D Jadhav
- School of Chemistry, Indian Institute of Science Education and Research Thiruvananthapuram (IISER TVM), Maruthamala P.O., Vithura, Thiruvananthapuram, 695551, Kerala, India
| | - Mahesh Hariharan
- School of Chemistry, Indian Institute of Science Education and Research Thiruvananthapuram (IISER TVM), Maruthamala P.O., Vithura, Thiruvananthapuram, 695551, Kerala, India
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Kumar G, Kellogg M, Dey S, Oliver TAA, Bradforth SE. Unraveling the Photoionization Dynamics of Indole in Aqueous and Ethanol Solutions. J Phys Chem B 2024; 128:4158-4170. [PMID: 38655896 DOI: 10.1021/acs.jpcb.4c01223] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/26/2024]
Abstract
The photoionization dynamics of indole, the ultraviolet-B chromophore of tryptophan, were explored in water and ethanol using ultrafast transient absorption spectroscopy with 292, 268, and 200 nm excitation. By studying the femtosecond-to-nanosecond dynamics of indole in two different solvents, a new photophysical model has been generated that explains many previously unsolved facets of indole's complex solution phase photochemistry. Photoionization is only an active pathway for indole in aqueous solution, leading to a reduction in the fluorescence quantum yield in water-rich environments, which is frequently used in biophysical experiments as a key signature of the protein-folded state. Photoionization of indole in aqueous solution was observed for all three pump wavelengths but via two different mechanisms. For 200 nm excitation, electrons are ballistically ejected directly into the bulk solvent. Conversely, 292 and 268 nm excitation populates an admixture of two 1ππ* states, which form a dynamic equilibrium with a tightly bound indole cation and electron-ion pair. The ion pair dissociates on a nanosecond time scale, generating separated solvated electrons and indole cations. The charged species serve as important precursors to triplet indole production and greatly enhance the overall intersystem crossing rate. Our proposed photophysical model for indole in aqueous solution is the most appropriate for describing photoinduced dynamics of tryptophan in polypeptide sequences; tryptophan in aqueous pH 7 solution is zwitterionic, unlike in peptides, and resultantly has a competitive excited state proton transfer pathway that quenches the tryptophan fluorescence.
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Affiliation(s)
- Gaurav Kumar
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Michael Kellogg
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Shivalee Dey
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Thomas A A Oliver
- School of Chemistry, Cantock's Close, University of Bristol, Bristol BS8 1TS, U.K
| | - Stephen E Bradforth
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
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Chavez J, Ceresa L, Kitchner E, Pham D, Gryczynski Z, Gryczynski I. Room temperature phosphorescence of 2-aminopyridine with direct triplet state excitation. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2023; 295:122640. [PMID: 36958243 DOI: 10.1016/j.saa.2023.122640] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/24/2022] [Revised: 03/05/2023] [Accepted: 03/14/2023] [Indexed: 06/18/2023]
Abstract
Phosphorescence emission at room temperature has been observed from 2-Aminopyridyne (2APi) embedded in poly (vinyl alcohol) (PVA) films. The gated emission with UV excitation at 305 nm results in a residual delayed fluorescence at around 350 nm and a broad phosphorescence spectrum with a maximum of around 500 nm. The phosphorescence excitation spectrum of 2APi - doped PVA film differs from the absorption spectrum in the long-wavelength part, showing a band at about 400-450 nm. The phosphorescence spectrum measured with a blue (420 nm) excitation closely resembles the spectrum measured with 305 nm excitation. Whereas the phosphorescence anisotropy measured with UV excitation is low and negative, with the blue excitation, the anisotropy is high and positive. The phosphorescence lifetimes (a fraction of a millisecond) are similar for UV and blue excitations. Both phosphorescence emissions with either UV or blue excitation strongly depend on temperature.
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Affiliation(s)
- Jose Chavez
- Department of Physics and Astronomy, Texas Christian University, Fort Worth, TX 76129, United States.
| | - Luca Ceresa
- Department of Physics and Astronomy, Texas Christian University, Fort Worth, TX 76129, United States
| | - Emma Kitchner
- Department of Physics and Astronomy, Texas Christian University, Fort Worth, TX 76129, United States
| | - Danh Pham
- Department of Physics and Astronomy, Texas Christian University, Fort Worth, TX 76129, United States
| | - Zygmunt Gryczynski
- Department of Physics and Astronomy, Texas Christian University, Fort Worth, TX 76129, United States
| | - Ignacy Gryczynski
- Department of Physics and Astronomy, Texas Christian University, Fort Worth, TX 76129, United States
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Wang HJ, Liu Y, Yu B, Song SQ, Zheng YX, Liu K, Chen P, Wang H, Jiang J, Li TY. A Configurationally Confined Thermally Activated Delayed Fluorescent Two-Coordinate Cu I Complex for Efficient Blue Electroluminescence. Angew Chem Int Ed Engl 2023; 62:e202217195. [PMID: 36542446 DOI: 10.1002/anie.202217195] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2022] [Revised: 12/20/2022] [Accepted: 12/21/2022] [Indexed: 12/24/2022]
Abstract
Thermally activated delayed fluorescence (TADF) from linear two-coordinate coinage metal complexes is sensitive to the geometric arrangement of the ligands. Herein we realize the tuning of configuration from coplanar to orthogonal gradually by variation of substituents. In a complex with confined twist configuration, its blue emission peaking at 458 nm presents a high ΦPL of 0.74 and a short τTADF of 1.9 μs, which indicates a fast enough kr,TADF of 3.9×105 s-1 and a depressed knr of 1.4×105 s-1 . Such outstanding luminescent properties are attributed to the proper overlap of HOMO and LUMO on CuI d orbitals that guarantees not only small ΔEST but also sufficient transition oscillator strength for fast k r , S 1 ${{k}_{{\rm r},{{\rm S}}_{1}}}$ . Vacuum-deposited blue OLEDs with either doped or host-free emissive layer present external quantum efficiencies over 20 % and 10 %, respectively, demonstrating the practicality of the configurationally confined strategy for efficient linear CuI TADF emitters.
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Affiliation(s)
- Hai-Jie Wang
- School of Chemistry and Biological Engineering, Department of Chemistry, University of Science and Technology Beijing, 30 Xueyuan Road, Beijing, 100083, China
| | - Yuan Liu
- Key Laboratory of the Ministry of Education for Optoelectronic Measurement Technology and Instrument, Beijing Information Science & Technology University, Beijing, 100192, China
| | - Baoqiu Yu
- School of Chemistry and Biological Engineering, Department of Chemistry, University of Science and Technology Beijing, 30 Xueyuan Road, Beijing, 100083, China
| | - Shi-Quan Song
- School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210023, China
| | - You-Xuan Zheng
- School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210023, China
| | - Kanglei Liu
- School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing, 100081, China
| | - Pangkuan Chen
- School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing, 100081, China
| | - Hailong Wang
- School of Chemistry and Biological Engineering, Department of Chemistry, University of Science and Technology Beijing, 30 Xueyuan Road, Beijing, 100083, China
| | - Jianzhuang Jiang
- School of Chemistry and Biological Engineering, Department of Chemistry, University of Science and Technology Beijing, 30 Xueyuan Road, Beijing, 100083, China
| | - Tian-Yi Li
- School of Chemistry and Biological Engineering, Department of Chemistry, University of Science and Technology Beijing, 30 Xueyuan Road, Beijing, 100083, China
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Morshedi M, Nolden O, Janke P, Haselbach W, Schmitt M, Gilch P. The photophysics of 2-cyanoindole probed by femtosecond spectroscopy. Photochem Photobiol Sci 2022; 22:745-759. [PMID: 36495408 DOI: 10.1007/s43630-022-00348-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2022] [Accepted: 11/24/2022] [Indexed: 12/14/2022]
Abstract
AbstractThe photophysics of 2-cyanoindole (2-CI) in solution (water, 2,2,2-trifluoroethanol, acetonitrile‚ and tetrahydrofuran) was investigated by steady-state as well as time resolved fluorescence and absorption spectroscopy. The fluorescence quantum yield of 2-cyanoindole is strongly sensitive to the solvent. In water the quantum yield is as low as 4.4 × 10–4. In tetrahydrofuran, it amounts to a yield of 0.057. For 2-CI dissolved in water, a bi-exponential fluorescence decay with time constants of ∼1 ps and ∼8 ps is observed. For short wavelength excitation (266 nm) the initial fluorescence anisotropy is close to zero. For excitation with 310 nm it amounts to 0.2. In water, femtosecond transient absorption reveals that the fluorescence decay is solely due to internal conversion to the ground state. In aprotic solvents, the fluorescence decay takes much longer (acetonitrile: ∼900 ps, tetrahydrofuran: ∼2.6 ns) and intersystem crossing contributes.
Graphical abstract
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Rivera JJ, Trinh C, Kim JE. Photoinduced Electron Transfer from the Tryptophan Triplet State in Zn-Azurin. ACS PHYSICAL CHEMISTRY AU 2022; 3:63-73. [PMID: 36718260 PMCID: PMC9881450 DOI: 10.1021/acsphyschemau.2c00042] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Revised: 10/18/2022] [Accepted: 10/19/2022] [Indexed: 11/30/2022]
Abstract
Tryptophan is one of few residues that participates in biological electron transfer reactions. Upon substitution of the native Cu2+ center with Zn2+ in the blue-copper protein azurin, a long-lived tryptophan neutral radical can be photogenerated. We report the following quantum yield values for Zn-substituted azurin in the presence of the electron acceptor Cu(II)-azurin: formation of the tryptophan neutral radical (Φrad), electron transfer (ΦET), fluorescence (Φfluo), and phosphorescence (Φphos), as well as the efficiency of proton transfer of the cation radical (ΦPT). Increasing the concentration of the electron acceptor increased Φrad and ΦET values and decreased Φphos without affecting Φfluo. At all concentrations of the acceptor, the value of ΦPT was nearly unity. These observations indicate that the phosphorescent triplet state is the parent state of electron transfer and that nearly all electron transfer events lead to proton loss. Similar results regarding the parent state were obtained with a different electron acceptor, [Co(NH3)5Cl]2+; however, Stern-Volmer graphs revealed that [Co(NH3)5Cl]2+ was a more effective phosphorescence quencher (K SV = 230 000 M-1) compared to Cu(II)-azurin (K SV = 88 000 M-1). Competition experiments in the presence of both [Co(NH3)5Cl]2+ and Cu(II)-azurin suggested that [Co(NH3)5Cl]2+ is the preferred electron acceptor. Implications of these results in terms of quenching mechanisms are discussed.
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8
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Chavez J, Ceresa L, Kimball J, Kitchner E, Gryczynski Z, Gryczynski I. Room temperature luminescence of 5-chloroindole. J Mol Liq 2022. [DOI: 10.1016/j.molliq.2022.119482] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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9
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Guðmundsson KE, Marteinsdóttir G, Kristbergsson K, Kvaran Á. Melatonin photoreactivity: phosphorescence formation and quenching processes. CHEMICAL PAPERS 2022. [DOI: 10.1007/s11696-022-02222-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
AbstractStudies of melatonin photoreactivity in water solutions: An effect of an external heavy atom I− on UV/Vis absorption, fluorescence and phosphorescence spectra is explored. The data allowed determination of relevant energetics for the system.The heavy atom effect (HAE) of I− on melatonin is clearly found to induce an intersystem crossing from the lowest energy singlet state to the lowest energy triplet state (T1) by a state mixing. Lifetime for the first excited triplet states of melatonin in association with I− and quenching rates for halomethanes (CH2X2, CHX3, CY4, X = Cl, Br, Y = Cl) are determined from Time-Correlated Single-Photon Counting decay curves for the phosphorescence. Dramatic alterations in quenching rate constants with quenchers as CH2X2 < CHX3 < CX4 and Cl < Br are attributed to energy transfer from an I−…Me*(T1) complex to low-lying electronic states of the halomethanes followed by dissociation to form R and X fragments. Relevance of the melatonin photoreactivity to photosensitizer properties in organic media is discussed.
Graphical abstract
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Chavez JL, Ceresa L, Reeks JM, Strzhemechny Y, Kimball J, Kitchner E, Gryczynski Z, Gryczynski I. Direct Excitation of Tryptophan Phosphorescence. A New Method for Triplet States Investigation. Methods Appl Fluoresc 2022; 10. [PMID: 35042210 DOI: 10.1088/2050-6120/ac4c9a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Accepted: 01/18/2022] [Indexed: 11/12/2022]
Abstract
We studied room temperature phosphorescence of tryptophan (TRP) embedded in poly (vinyl alcohol) films. With UV (285 nm) excitation, the phosphorescence spectrum of tryptophan appears at about 460 nm. We also observed the TRP phosphorescence with blue light excitation at 410 nm, well outside of the S0→S1 absorption. This excitation reaches the triplet state of tryptophan directly without the involvement of the singlet excited state. The phosphorescence lifetime of tryptophan is in the sub-millisecond range. The long-wavelength direct excitation to the triplet state results in high phosphorescence anisotropy which can be useful in macromolecule dynamics study via time-resolved phosphorescence.
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Affiliation(s)
- Jose Luis Chavez
- Department of Physics & Astronomy, Texas Christian University, 2995 S. University Dr., Fort Worth, 76129, UNITED STATES
| | - Luca Ceresa
- Department of Physics and Astronomy, Texas Christian University, 2995 S. University Dr., Fort Worth, Texas, 76129, UNITED STATES
| | - John M Reeks
- Department of Physics & Astronomy, Texas Christian University, 2995 S. University Dr., Fort Worth, 76129, UNITED STATES
| | - Yuri Strzhemechny
- Department of Physics and Astronomy, Texas Christian University, College of Science & Engineering, TCU Box 298840, Fort Worth, TX 76129, USA, Fort Worth, Texas, 76129, UNITED STATES
| | - Joe Kimball
- Department of Physics and Astronomy, Texas Christian University, 2995 S. University Dr., Fort Worth, Texas, 76129, UNITED STATES
| | - Emma Kitchner
- Department of Physics and Astronomy, Texas Christian University, 2995 S. University Dr., Fort Worth, Texas, 76129, UNITED STATES
| | - Zygmunt Gryczynski
- Department of Physics and Astronomy, Texas Christian University, 2995 S. University Dr., Fort Worth, Texas, 76129, UNITED STATES
| | - Ignacy Gryczynski
- Department of Physics & Astronomy, Texas Christian University, 2995 S. University Dr., Fort Worth, 76129, UNITED STATES
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Weigl P, Schadt D, Weißheit S, Thiele CM, Walther T, Blochowicz T. Triplet state solvation dynamics: extending the accessible timescale by using indole as local probe. Phys Chem Chem Phys 2021; 23:683-693. [PMID: 33336668 DOI: 10.1039/d0cp05240j] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Triplet state solvation dynamics (TSD) is a truly local measurement technique, where a dye molecule is dissolved as a probe at low concentration in a solvent. Depending on the dye molecule, local information on mechanical or dielectric solvation can be obtained. So far, this method has mainly been used to investigate topics such as fundamentals of glassy dynamics and confinement effects. Based on the procedure presented in [P. Weigl et al., Z. Phys. Chem., 2018, 232, 1017-1039] in the present contribution two new TSD probes, namely indole and its derivative cbz-tryptophan, are identified and characterized in detail. In particular, their longer phosphorescence lifetime allows for a significant extension of the timescale of local mechanical and dipolar solvation measurements. In combination with previously used dyes a measurement window of up to five orders of magnitude in time can be covered. Furthermore, we show that in cbz-tryptophan the indole unit is the phosphorescence center, while the rest of the molecule only slightly contributes to the solvation response function. The detailed understanding of these two new TSD probes presented in this work, will allow in depth investigations of solvation and the corresponding dynamics also for biologically relevant systems in the future.
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Affiliation(s)
- Peter Weigl
- Institute for Condensed Matter Physics, Technical University of Darmstadt, 64289 Darmstadt, Germany.
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Chavez J, Ceresa L, Kitchner E, Kimball J, Shtoyko T, Fudala R, Borejdo J, Gryczynski Z, Gryczynski I. On the possibility of direct triplet state excitation of indole. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2020; 208:111897. [PMID: 32447191 DOI: 10.1016/j.jphotobiol.2020.111897] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/27/2019] [Revised: 02/26/2020] [Accepted: 05/13/2020] [Indexed: 11/18/2022]
Abstract
We studied the luminescence properties of indole in poly (vinyl alcohol) (PVA) film. The indole molecules are effectively immobilized in this polymer film and display both fluorescence and phosphorescence emission at room temperature. We noticed that the phosphorescence of indole in PVA film can be effectively excited at a longer wavelength than its typical singlet to triplet population route involving intersystem crossing. The maximum of the phosphorescence excitation is about 410 nm which corresponds to the energy of indole's triplet state. Interestingly, the phosphorescence anisotropy excited with the longer wavelength (405 nm) is positive and reaches a value of about 0.25 in contrast to the phosphorescence anisotropy excited within the indole singlet absorption spectrum (290 nm), which is negative. Very different temperature dependences have been observed for fluorescence and phosphorescence of indole in PVA film. While fluorescence depends minimally, the phosphorescence decreases with temperature dramatically. The fluorescence lifetime was measured to be a single component 4.78 ns while the intensity weighted average phosphorescence lifetime with 290 nm and 405 nm excitations were 6.57 and 5.62 ms, respectively. We believe that the possibility of the excitation of indole phosphorescence in the blue region of visible light and its high anisotropy opens a new avenue for future protein studies.
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Affiliation(s)
- Jose Chavez
- Department of Physics and Astronomy, Texas Christian University, Fort Worth, TX 76129, USA
| | - Luca Ceresa
- Department of Physics and Astronomy, Texas Christian University, Fort Worth, TX 76129, USA
| | - Emma Kitchner
- Department of Physics and Astronomy, Texas Christian University, Fort Worth, TX 76129, USA
| | - Joseph Kimball
- Department of Physics and Astronomy, Texas Christian University, Fort Worth, TX 76129, USA.
| | - Tanya Shtoyko
- Department of Chemistry and Biochemistry, The University of Texas at Tyler, Tyler, TX 75799, USA
| | - Rafal Fudala
- Department of Microbiology, Immunology, and Genetics, Center for Fluorescence Technologies and Nanomedicine, University of North Texas Health Science Center, Fort Worth, TX 76107, USA
| | - Julian Borejdo
- Department of Microbiology, Immunology, and Genetics, Center for Fluorescence Technologies and Nanomedicine, University of North Texas Health Science Center, Fort Worth, TX 76107, USA
| | - Zygmunt Gryczynski
- Department of Physics and Astronomy, Texas Christian University, Fort Worth, TX 76129, USA; Department of Microbiology, Immunology, and Genetics, Center for Fluorescence Technologies and Nanomedicine, University of North Texas Health Science Center, Fort Worth, TX 76107, USA
| | - Ignacy Gryczynski
- Department of Microbiology, Immunology, and Genetics, Center for Fluorescence Technologies and Nanomedicine, University of North Texas Health Science Center, Fort Worth, TX 76107, USA
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Draganski AR, Friedman JM, Ludescher RD. Solvent-Slaved Dynamic Processes Observed by Tryptophan Phosphorescence of Human Serum Albumin. Biophys J 2017; 112:881-891. [PMID: 28297647 DOI: 10.1016/j.bpj.2016.12.048] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2016] [Revised: 12/16/2016] [Accepted: 12/23/2016] [Indexed: 10/20/2022] Open
Abstract
Despite extensive experimental and computational efforts to understand the nature of the hierarchy of protein fluctuations and the modulating role of the protein hydration shell, a detailed microscopic description of the dynamics of the protein-solvent system has yet to be achieved. By using single tryptophan protein phosphorescence, we follow site-specific internal protein dynamics over a broad temperature range and demonstrate three independent dynamic processes. Process I is seen at temperatures below the bulk solvent Tg, has low activation energy, and is likely due to fast vibrations that may be enabled by water mobility on the protein surface. Process II is observed above 170 K, with activation energy typical of β relaxations in a glass; it has the same temperature dependence as fluctuations of hydration shell waters. Process III is observed at T > 200 K; it has super-Arrhenius temperature dependence and closely follows the primary relaxation of the bulk. The fluorescence of pyranine bound to the protein reports on the mobility of water in the hydration shell; it reveals a shift in emission spectra with increasing temperature, indicative of a changing H-bond network at the surface of the protein. These results support a model of solvent-slaved protein dynamics.
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Affiliation(s)
- Andrew R Draganski
- Department of Food Science, Rutgers University, New Brunswick, New Jersey
| | - Joel M Friedman
- Department of Physiology and Biophysics, Albert Einstein College of Medicine, Bronx, New York.
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Hevekerl H, Tornmalm J, Widengren J. Fluorescence-based characterization of non-fluorescent transient states of tryptophan - prospects for protein conformation and interaction studies. Sci Rep 2016; 6:35052. [PMID: 27748381 PMCID: PMC5066179 DOI: 10.1038/srep35052] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2016] [Accepted: 09/15/2016] [Indexed: 02/02/2023] Open
Abstract
Tryptophan fluorescence is extensively used for label-free protein characterization. Here, we show that by analyzing how the average tryptophan fluorescence intensity varies with excitation modulation, kinetics of tryptophan dark transient states can be determined in a simple, robust and reliable manner. Thereby, highly environment-, protein conformation- and interaction-sensitive information can be recorded, inaccessible via traditional protein fluorescence readouts. For verification, tryptophan transient state kinetics were determined under different environmental conditions, and compared to literature data. Conformational changes in a spider silk protein were monitored via the triplet state kinetics of its tryptophan residues, reflecting their exposure to an air-saturated aqueous solution. Moreover, tryptophan fluorescence anti-bunching was discovered, reflecting local pH and buffer conditions, previously observed only by ultrasensitive measurements in highly fluorescent photo-acids. Taken together, the presented approach, broadly applicable under biologically relevant conditions, has the potential to become a standard biophysical approach for protein conformation, interaction and microenvironment studies.
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Affiliation(s)
- Heike Hevekerl
- Royal Institute of Technology (KTH), Dept Applied Physics, Experimental Biomolecular Physics, Albanova Univ Center, 106 91 Stockholm, Sweden
| | - Johan Tornmalm
- Royal Institute of Technology (KTH), Dept Applied Physics, Experimental Biomolecular Physics, Albanova Univ Center, 106 91 Stockholm, Sweden
| | - Jerker Widengren
- Royal Institute of Technology (KTH), Dept Applied Physics, Experimental Biomolecular Physics, Albanova Univ Center, 106 91 Stockholm, Sweden
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15
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16
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Influence of glycerol on the molecular mobility, oxygen permeability and microstructure of amorphous zein films. Food Hydrocoll 2015. [DOI: 10.1016/j.foodhyd.2014.09.002] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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17
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Kowalska-Baron A, Gałęcki K, Wysocki S. Room temperature phosphorescence study on the structural flexibility of single tryptophan containing proteins. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2015; 134:380-387. [PMID: 25025310 DOI: 10.1016/j.saa.2014.06.122] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2014] [Revised: 05/28/2014] [Accepted: 06/21/2014] [Indexed: 06/03/2023]
Abstract
In this study, we have undertaken efforts to find correlation between phosphorescence lifetimes of single tryptophan containing proteins and some structural indicators of protein flexibility/rigidity, such as the degree of tryptophan burial or its exposure to solvent, protein secondary and tertiary structure of the region of localization of tryptophan as well as B factors for tryptophan residue and its immediate surroundings. Bearing in mind that, apart from effective local viscosity of the protein/solvent matrix, the other factor that concur in determining room temperature tryptophan phosphorescence (RTTP) lifetime in proteins is the extent of intramolecular quenching by His, Cys, Tyr and Trp side chains, the crystallographic structures derived from the Brookhaven Protein Data Bank were also analyzed concentrating on the presence of potentially quenching amino acid side chains in the close proximity of the indole chromophore. The obtained results indicated that, in most cases, the phosphorescence lifetimes of tryptophan containing proteins studied tend to correlate with the above mentioned structural indicators of protein rigidity/flexibility. This correlation is expected to provide guidelines for the future development of phosphorescence lifetime-based method for the prediction of structural flexibility of proteins, which is directly linked to their biological function.
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Affiliation(s)
- Agnieszka Kowalska-Baron
- Institute of General Food Chemistry, Faculty of Biotechnology and Food Sciences, Technical University of Lodz, ul. Stefanowskiego 4/10, 90-924 Lodz, Poland.
| | - Krystian Gałęcki
- Institute of General Food Chemistry, Faculty of Biotechnology and Food Sciences, Technical University of Lodz, ul. Stefanowskiego 4/10, 90-924 Lodz, Poland
| | - Stanisław Wysocki
- Institute of General Food Chemistry, Faculty of Biotechnology and Food Sciences, Technical University of Lodz, ul. Stefanowskiego 4/10, 90-924 Lodz, Poland
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18
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Kowalska-Baron A, Gałęcki K, Rożniakowski K, Kolesińska B, Kamiński ZJ, Wysocki S. Heavy atom induced phosphorescence study on the influence of internal structural factors on the photophysics of tryptophan in aqueous solutions. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2014; 128:830-837. [PMID: 24704600 DOI: 10.1016/j.saa.2014.02.168] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2013] [Revised: 02/14/2014] [Accepted: 02/24/2014] [Indexed: 06/03/2023]
Abstract
In this study the effect of alanyl residue insertion into tryptophan and to some extent the effect of peptide bond on the photophysics of tryptophan chromophore has been studied. The photophysical parameters crucial in triplet state decay mechanism of aqueous AW, WA and AWA peptides have been determined applying our previously proposed methodology based on the heavy atom effect and compared with the previously reported values for tryptophan (Kowalska-Baron et al., 2012). The obtained results clearly indicated that the presence of alanyl residue and the peptide bond results in the changes in the fluorescence and phosphorescence decay kinetics of tryptophan. The fluorescence decays of the oligopeptides studied at pH 7 were biexponential. The longer lifetime component of WA arises from anionic form of this dipeptide, while the shorter one may be assigned to the zwitterionic form of WA. The observed invariance of the lifetimes of anionic and zwitterionic forms of WA throughout the pH studied supports the idea that these two components of WA fluorescence decay correspond to nearly independent species, possibly interconverting but at a rate slower than the fluorescence decay rates. Comparing the determined phosphorescence spectra of the oligopeptides studied with that of tryptophan, a slight blue-shift and more evident red-shift was observed in the spectrum of AW and WA, respectively. On the basis of the results of the phosphorescence measurements performed at pH 10, the 170 μs lifetime of WA, observed even at pH 7, may be assigned to the anionic form of the compound. It may be suggested that at pH 7 during the excited triplet state lifetime of WA there is a shift in the equilibrium towards the anionic form of this dipeptide. In the case of AW and AWA at pH 7 the obtained monoexponential decay kinetics, most probably, arise from zwitterionic forms of these peptides. The determined triplet quantum yield of AWA is slightly lower than that of tryptophan, while the quantum yield of AW is twofold lower than that of tryptophan. The highest value of the determined triplet quantum yield of WA confirms the presence of anionic form of this dipeptide at pH 7.
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Affiliation(s)
- Agnieszka Kowalska-Baron
- Institute of General Food Chemistry, Faculty of Biotechnology and Food Sciences, Technical University of Lodz, ul. Stefanowskiego 4/10, 90-924 Lodz, Poland.
| | - Krystian Gałęcki
- Institute of General Food Chemistry, Faculty of Biotechnology and Food Sciences, Technical University of Lodz, ul. Stefanowskiego 4/10, 90-924 Lodz, Poland
| | - Kamil Rożniakowski
- Institute of Organic Chemistry, Technical University of Lodz, Lodz, Poland
| | - Beata Kolesińska
- Institute of Organic Chemistry, Technical University of Lodz, Lodz, Poland
| | | | - Stanisław Wysocki
- Institute of General Food Chemistry, Faculty of Biotechnology and Food Sciences, Technical University of Lodz, ul. Stefanowskiego 4/10, 90-924 Lodz, Poland
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19
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Sagoo K, Hirsch R, Johnston P, McLoskey D, Hungerford G. Pre-denaturing transitions in human serum albumin probed using time-resolved phosphorescence. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2014; 124:611-617. [PMID: 24509539 DOI: 10.1016/j.saa.2014.01.073] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2013] [Revised: 01/07/2014] [Accepted: 01/10/2014] [Indexed: 06/03/2023]
Abstract
The investigation of protein dynamics has long been of interest, since protein interactions and functions can be determined by their structure and changes in conformation. Although fluorescence, occurring on the nanosecond timescale, from intrinsic fluorescent amino acids has been extensively used, in order to fully access conformational changes longer timescales are required. Phosphorescence enables processes on the microsecond to second timescale to be accessed. However, at room temperature this emission can be weak and non trivial to measure. It requires the removal of oxygen - a common triplet state quencher and appropriate instrumentation. In this work we make use of a chemical deoxygenator to study room temperature phosphorescence from tryptophan in human serum albumin excited using a pulsed UV light emitting diode. This is extended to monitor the phosphorescence emission upon increasing temperature, allowing pre-denaturing transitions to be observed. Time-resolved data are analysed, both as the sum of exponential decays and using a distribution analysis based on non extensive decay kinetics. These results are compared to a fluorescence study and both the average lifetime and contribution of the different emitting components were found to give more dramatic changes on the phosphorescence timescale.
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Affiliation(s)
- Kulwinder Sagoo
- HORIBA Jobin Yvon IBH Ltd., 45 Finnieston Street, Glasgow G3 8JU, UK
| | - Richard Hirsch
- HORIBA Jobin Yvon IBH Ltd., 45 Finnieston Street, Glasgow G3 8JU, UK
| | - Pamela Johnston
- HORIBA Jobin Yvon IBH Ltd., 45 Finnieston Street, Glasgow G3 8JU, UK
| | - David McLoskey
- HORIBA Jobin Yvon IBH Ltd., 45 Finnieston Street, Glasgow G3 8JU, UK
| | - Graham Hungerford
- HORIBA Jobin Yvon IBH Ltd., 45 Finnieston Street, Glasgow G3 8JU, UK.
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20
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Liang J, Corradini MG, Ludescher RD. Influence of antioxidant structure on local molecular mobility in amorphous sucrose. Carbohydr Res 2014; 383:14-20. [PMID: 24239605 DOI: 10.1016/j.carres.2013.10.014] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2013] [Revised: 10/16/2013] [Accepted: 10/19/2013] [Indexed: 11/27/2022]
Abstract
The effect of the antioxidants gallic acid and methyl, propyl, and octyl gallate on the molecular mobility and hydrogen bond network in amorphous sucrose was studied. Solid amorphous sucrose films with and without the addition of antioxidants at a mole ratio of 1:5 (antioxidant/sucrose) were cast from solution onto quartz slides. Local molecular mobility from 0 to 70°C was measured using tryptophan amino acid as a luminescent probe dispersed in the films. Phosphorescence from the tryptophan probe provides spectroscopic characteristics-emission spectrum and lifetime-that are sensitive to changes in molecular mobility induced by the addition of antioxidants. Local molecular mobility detected by tryptophan increased in the following order: sucrose<sucrose-octyl gallate<sucrose-propyl gallate⩽sucrose-methyl gallate⩽sucrose-gallic acid. The antioxidants also modulated the activation energy for matrix motions that quench the tryptophan phosphorescence in a structure-dependent manner. IR measurements as a function of temperature indicated that hydrogen bond strength in these amorphous films followed a rank order (sucrose-methyl gallate>sucrose-gallic acid>sucrose-propyl gallate>sucrose>sucrose-octyl gallate) that was nearly the reverse of that seen in matrix mobility. Analysis of the differential effects of the antioxidants suggests that the presence of the hydroxyl benzoyl head group increased matrix molecular mobility and hydrogen bond strength while the saturated carbon chain decreased mobility and bond strength. The influence of the carboxyl group on matrix properties was comparable to that of the formyloxy group. These results indicate that the addition of specific functional ingredients such as antioxidants may significantly affect the physical properties and consequently functional properties of amorphous edible films in ways that might condition their use. The observed changes are closely related to the chemical structure of the added species.
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Affiliation(s)
- Jun Liang
- Department of Food Science, Rutgers, The State University of New Jersey, 65 Dudley Road, New Brunswick, NJ 08901, United States
| | - Maria G Corradini
- Department of Food Science, Rutgers, The State University of New Jersey, 65 Dudley Road, New Brunswick, NJ 08901, United States
| | - Richard D Ludescher
- Department of Food Science, Rutgers, The State University of New Jersey, 65 Dudley Road, New Brunswick, NJ 08901, United States.
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21
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Kowalska-Baron A, Gałęcki K, Wysocki S. Photophysics of indole-2-carboxylic acid (I2C) and indole-5-carboxylic acid (I5C): heavy atom effect. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2013; 116:183-195. [PMID: 23933843 DOI: 10.1016/j.saa.2013.07.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2013] [Accepted: 07/03/2013] [Indexed: 06/02/2023]
Abstract
In this study the effect of carboxylic group substitution in the 2 and 5 position of indole ring on the photophysics of the parent indole chromophore has been studied. The photophysical parameters crucial in triplet state decay mechanism of aqueous indole-2-carboxylic acid (I2C) and indole-5-carboxylic acid (I5C) have been determined applying our previously proposed methodology based on the heavy atom effect and fluorescence and phosphorescence decay kinetics [Kowalska-Baron et al., 2012]. The determined time-resolved phosphorescence spectra of I2C and I5C are red-shifted as compared to that of the parent indole. This red-shift was especially evident in the case of I2C and may indicate the possibility of hydrogen bonded complex formation incorporating carbonyl CO, the NH group of I2C and, possibly, surrounding water molecules. The possibility of the excited state charge transfer process and the subsequent electronic charge redistribution in such a hydrogen bonded complex may also be postulated. The resulting stabilization of the I2C triplet state is manifested by its relatively long phosphorescence lifetime in aqueous solution (912 μs). The relatively short phosphorescence lifetime of I5C (56 μs) may be the consequence of more effective ground-state quenching of I5 C triplet state. This hypothesis may be strengthened by the significantly larger value of the determined rate constant of I5C triplet state quenching by its ground-state (4.4 × 10(8)M(-1)s(-1)) as compared to that for indole (6.8 × 10(7)M(-1)s(-1)) and I2C (2.3 × 10(7)M(-1)s(-1)). The determined bimolecular rate constant for triplet state quenching by iodide [Formula: see text] is equal to 1 × 10(4)M(-1)s(-1); 6 × 10(3)M(-1)s(-1) and 2.7 × 10(4)M(-1)s(-1) for indole, I2 C and I5 C, respectively. In order to obtain a better insight into iodide quenching of I2C and I5C triplet states in aqueous solution, the temperature dependence of the bimolecular rate constants for iodide quenching of the triplet states has been expressed in Arrhenius form. The linearity of the obtained Arrhenius plots clearly indicated the existence of one temperature-dependent non-radiative process for the de-excitation of I2C and I5C triplet state in the presence of iodide. This process may be attributed to the solute-quenching by iodide and, most probably, proceeds via reversibly formed exciplex. The activation energies obtained from linear Arrhenius plots (1.89 kcal/mol for I5 C; 2.55 kcal/mol for I2 C) are smaller as compared to that for diffusion controlled reactions in aqueous solution (about 4 kcal/mol), which may indicate the great importance of the electrostatic interactions between solute and iodide ions in lowering the energy barrier needed for the formation of the triplet-quencher complex. Based on the theoretical predictions (at the DFT(CAM-B3LYP)/6-31+G(d,p) level of theory) and careful analysis of the obtained FTIR spectra it may be concluded that in the solid state I2 C and I5 C molecules form associates by intermolecular NH · · · OC and OH · · · OC hydrogen bonding interactions, whereas the existence of intramolecular NH · · · OC interactions in the solid state of I2C and I5C is highly unlikely.
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Affiliation(s)
- Agnieszka Kowalska-Baron
- Institute of General Food Chemistry, Faculty of Biotechnology and Food Sciences, Technical University of Lodz, ul. Stefanowskiego 4/10, 90-924 Lodz, Poland.
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22
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Kowalska-Baron A, Gałęcki K, Wysocki S. Temperature study of indole, tryptophan and N-acetyl-L-tryptophanamide (NATA) triplet-state quenching by iodide in aqueous solution. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2013; 111:42-48. [PMID: 23602958 DOI: 10.1016/j.saa.2013.03.086] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2013] [Revised: 03/01/2013] [Accepted: 03/16/2013] [Indexed: 06/02/2023]
Abstract
In this study, the temperature dependence of the measured phosphorescence lifetimes of aqueous indole, tryptophan and N-acetyl-L-tryptophanamide (NATA) between 6 and 55 °C in the absence and in the presence of iodide, a suitable intersystem crossing enhancer, has been determined. The obtained results suggest the existence of one process for the temperature-dependent, non-radiative deactivation of triplet states of the aqueous indoles in the absence of iodide. This process may be associated with the high sensitivity of indole triplet state lifetime to the subtle changes in the local viscosity of the surrounding aqueous environment or may be attributed to diffusional quenching by solvent molecules and/or by possible impurities present in water. However, the steep decrease in the measured phosphorescence lifetimes of indole and tryptophan with temperature suggests that diffusion-mediated quenching processes are not prevailing. Upon increasing concentration of iodide (up to 0.1 M), the obtained Arrhenius plots for the deactivation rate (1/τph) of the triplet states of the studied indoles were linear, which provided strong support for the hypothesis of the existence of one temperature dependent non-radiative process for the de-excitation of indoles triplet state. Our results showed that this process is attributed to the diffusion-controlled solute-quenching by iodide and, most probably, proceeds via reversibly formed exciplex. At concentration of iodide higher than 0.1M highly curved Arrhenius plots were obtained, which may indicate a change in the rate determining step with a change in temperature. This change most probably is associated with a transition from diffusion-controlled exciplex formation followed by rate-determining exciplex deactivation at high temperature.
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Affiliation(s)
- Agnieszka Kowalska-Baron
- Institute of General Food Chemistry, Faculty of Biotechnology and Food Sciences, Technical University of Lodz, ul. Stefanowskiego 4/10, 90-924 Lodz, Poland.
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23
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Effect of temperature on molecular mobility, oxygen permeability, and dynamic site heterogeneity in amorphous α-lactalbumin films. Food Hydrocoll 2013. [DOI: 10.1016/j.foodhyd.2012.11.010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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24
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Kowalska-Baron A, Chan M, Gałęcki K, Wysocki S. Photophysics of indole, tryptophan and N-acetyl-L-tryptophanamide (NATA): heavy atom effect. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2012; 98:282-289. [PMID: 22964241 DOI: 10.1016/j.saa.2012.08.017] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2012] [Revised: 06/28/2012] [Accepted: 08/09/2012] [Indexed: 06/01/2023]
Abstract
Previously reported flash photolysis studies showed that the triplet state lifetime of aqueous indoles is μs long (12.5 μs for tryptophan [10]), while other recently reported phosphorescence lifetimes of aqueous indoles, determined from photon counting phosphorescence techniques, vary from μs (approximately 40 μs [11]) to ms (5 ms for indole [12]). This study was motivated to explain the discrepancy regarding the intrinsic triplet state lifetime of aqueous indole and its derivatives: tryptophan and N-acetyl-L-tryptophanamide (NATA). For this purpose, a new methodology based on both fluorescence and phosphorescence decay kinetics incorporating the heavy atom effect have been applied in order to determine some quantitative parameters of the photophysics of indole and its derivatives. Additionally, we have also determined the triplet state lifetimes of the studied indoles using flash photolysis in which contributions from both a first order component and a second order component (from triplet-triplet annihilation) have been taken into account in the triplet state depopulation. The measured phosphorescence lifetime of the indoles examined measures between the values reported by Fischer and Strambini and is consistent with the triplet state lifetime determined from flash photolysis. We hope that the results obtained in this paper would be helpful for deriving structural and dynamical information from phosphorescence data of tryptophan residues in proteins.
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Affiliation(s)
- Agnieszka Kowalska-Baron
- Institute of General Food Chemistry, Faculty of Biotechnology and Food Sciences, Technical University of Lodz, ul. Stefanowskiego 4/10, 90-924 Lodz, Poland.
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25
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Tiwari R, Ludescher RD. Molecular mobility in a homologous series of amorphous solid glucose oligomers. Food Chem 2012. [DOI: 10.1016/j.foodchem.2011.12.011] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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26
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You Y, Ludescher RD. Effect of starch on the molecular mobility of amorphous sucrose. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2011; 59:3340-3347. [PMID: 21381746 DOI: 10.1021/jf1041432] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Molecular mobility in amorphous solid biomaterials is modulated by the composition and environment (primarily temperature). Phosphorescence of the triplet probe erythrosin B was used to generate a mobility map within amorphous sucrose films doped with starch ranging from 0.001 to 0.1 g starch/g sucrose. Data on the emission energy and lifetime of erythrosin B in sucrose and sucrose-starch films over the temperature range from 5 to 100 °C indicates that starch influences the molecular mobility as well as dynamic site heterogeneity of amorphous sucrose in a dose-dependent manner. At a starch/sucrose weight (wt) ratio below 0.005, both emission energy and lifetime decreased, and both the dipolar relaxation rate and nonradiative quenching rate k(TS0) increased, indicating that starch increased the matrix molecular mobility. At a ratio above 0.005, both emission energy and lifetime increased, and the dipolar relaxation rate and nonradiative quenching rate decreased, indicating that starch decreased the matrix mobility both in the glass and in the melt. The mobility showed a minimum value at a ratio of 0.01. The interactions existing in the sucrose-starch matrix are considered as the determining factor to influence the molecular mobility of sucrose-starch mixtures. Changes in the distribution of emission energies (emission bandwidth) and lifetimes indicated that starch increased the spectral heterogeneity at high contents while showing insignificant change or a slight decrease in the heterogeneity at low starch contents. These data illustrate the complex effects of a polymer with mainly linear structure and flexible conformation on the mobility of an amorphous, hydrogen bonded sugar matrix.
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Affiliation(s)
- Yumin You
- Department of Food Science, Rutgers, The State University of New Jersey, 65 Dudley Road, New Brunswick, New Jersey 08901-8520, United States
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27
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28
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You Y, Ludescher RD. The Effect of Molecular Size on Molecular Mobility in Amorphous Oligosaccharides. FOOD BIOPHYS 2010. [DOI: 10.1007/s11483-010-9148-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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29
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Tiwari RS, Ludescher RD. Vanillin Phosphorescence as a Probe of Molecular Mobility in Amorphous Sucrose. J Fluoresc 2009; 20:125-33. [DOI: 10.1007/s10895-009-0530-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2009] [Accepted: 08/07/2009] [Indexed: 10/20/2022]
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30
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Gauden M, Pezzella A, Panzella L, Napolitano A, d’Ischia M, Sundström V. Ultrafast Excited State Dynamics of 5,6-Dihydroxyindole, A Key Eumelanin Building Block: Nonradiative Decay Mechanism. J Phys Chem B 2009; 113:12575-80. [DOI: 10.1021/jp903190k] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Magdalena Gauden
- Department of Chemical Physics, Lund University, Box 124, S 22100 Lund, Sweden, and Department of Organic Chemistry and Biochemistry, University of Naples Federico II, Naples, Italy
| | - Alessandro Pezzella
- Department of Chemical Physics, Lund University, Box 124, S 22100 Lund, Sweden, and Department of Organic Chemistry and Biochemistry, University of Naples Federico II, Naples, Italy
| | - Lucia Panzella
- Department of Chemical Physics, Lund University, Box 124, S 22100 Lund, Sweden, and Department of Organic Chemistry and Biochemistry, University of Naples Federico II, Naples, Italy
| | - Alessandra Napolitano
- Department of Chemical Physics, Lund University, Box 124, S 22100 Lund, Sweden, and Department of Organic Chemistry and Biochemistry, University of Naples Federico II, Naples, Italy
| | - Marco d’Ischia
- Department of Chemical Physics, Lund University, Box 124, S 22100 Lund, Sweden, and Department of Organic Chemistry and Biochemistry, University of Naples Federico II, Naples, Italy
| | - Villy Sundström
- Department of Chemical Physics, Lund University, Box 124, S 22100 Lund, Sweden, and Department of Organic Chemistry and Biochemistry, University of Naples Federico II, Naples, Italy
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31
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Borisevich N, Sukhodola A, Tolstorozhev G. Mechanisms of the delayed luminescence of N-methylindole and indole in the gas phase. Chem Phys 2008. [DOI: 10.1016/j.chemphys.2008.09.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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32
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Effect of gelatin on molecular mobility in amorphous sucrose detected by erythrosin B phosphorescence. Carbohydr Res 2008; 343:2657-66. [DOI: 10.1016/j.carres.2008.08.009] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2008] [Revised: 07/22/2008] [Accepted: 08/07/2008] [Indexed: 11/22/2022]
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33
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You Y, Ludescher RD. The effect of salts on molecular mobility in amorphous sucrose monitored by erythrosin B phosphorescence. Carbohydr Res 2008; 343:2641-9. [DOI: 10.1016/j.carres.2008.06.008] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2008] [Revised: 06/03/2008] [Accepted: 06/06/2008] [Indexed: 11/28/2022]
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34
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Sundaresan KV, Ludescher RD. Molecular mobility and oxygen permeability in amorphous β-lactoglobulin films. Food Hydrocoll 2008. [DOI: 10.1016/j.foodhyd.2006.12.004] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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35
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You Y, Ludescher RD. The effect of sodium chloride on molecular mobility in amorphous sucrose detected by phosphorescence from the triplet probe erythrosin B. Carbohydr Res 2008; 343:350-63. [DOI: 10.1016/j.carres.2007.11.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2007] [Revised: 11/02/2007] [Accepted: 11/06/2007] [Indexed: 11/25/2022]
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36
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The Effect of Glycerol on Molecular Mobility in Amorphous Sucrose Detected by Phosphorescence of Erythrosin B. FOOD BIOPHYS 2007. [DOI: 10.1007/s11483-007-9030-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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37
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Strambini GB, Kerwin BA, Mason BD, Gonnelli M. The Triplet-state Lifetime of Indole Derivatives in Aqueous Solution¶. Photochem Photobiol 2007. [DOI: 10.1111/j.1751-1097.2004.tb00115.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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38
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Wei Y, Dong C, Liu D, Shuang S, Huie CW. Enantioselective Quenching of Room-Temperature Phosphorescence Lifetimes of Proteins: Bovine and Human Serum Albumins. Biomacromolecules 2007; 8:761-4. [PMID: 17274655 DOI: 10.1021/bm0610121] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Enantioselective quenching of the room-temperature phosphorescence (RTP) lifetime of proteins was demonstrated due to the effects of various external chiral quenching agents. In the absence of quenchers, the RTP lifetimes for bovine serum albumin (BSA) and human serum albumin (HSA) were found to be 5.0 +/- 0.2 and 4.0 +/- 0.1 ms, respectively. The addition of various chiral quenchers (three pairs of binaphthols and two pairs of beta-blockers) into the deoxygenated sample solutions containing BSA and HSA reduced their RTP lifetimes significantly, i.e., from ca. 4-5 ms (in the absence) to an average lifetime of ca. 1-2 ms (in the presence) of the chiral quenchers. For the R and S enantiomers examined, marked differences in RTP lifetimes were observed, i.e., ranging from ca. 20-29% for the binaphthols to ca.14-16% for the beta-blockers. Such findings could lead to a better understanding of the relationship between chirality, dynamics/conformational changes, and biological functions of proteins.
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Affiliation(s)
- Yanli Wei
- Research Center of Environmental Science and Engineering, College of Chemistry and Chemical Engineering, Shanxi University, Taiyuan, 030006, People's Republic of China
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Shirke S, You Y, Ludescher RD. Molecular mobility and dynamic site heterogeneity in amorphous lactose and lactitol from erythrosin B phosphorescence. Biophys Chem 2006; 123:122-33. [PMID: 16730879 DOI: 10.1016/j.bpc.2006.05.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2006] [Revised: 05/03/2006] [Accepted: 05/04/2006] [Indexed: 11/29/2022]
Abstract
We have used phosphorescence from erythrosin B to characterize the molecular mobility and dynamic heterogeneity in dry films of amorphous lactose and lactitol from -25 to 120 degrees C. The phosphorescence emission spectra red-shifted and broadened with temperature in both sugars, indicating that both the rate of dipolar relaxation and the extent of inhomogeneous broadening increased dramatically at higher temperature. Phosphorescence intensity decays were well fit using a stretched exponential decay model; the rate constant for non-radiative quenching due to collisions with the matrix was calculated from the lifetimes. Arrhenius plots of this rate were non-linear, increasing very gradually at low and dramatically at high temperatures in both sugars. The rate of quenching was significantly lower in a 1:1 (wt/wt) mixture of lactose/lactitol in both the glass and the melt, providing strong evidence that specific interactions within the mixture lowered the matrix mobility. The lifetimes varied systematically with emission wavelength in both matrixes; analysis of the temperature dependence indicated that the activation energy for non-radiative quenching of the triplet state varied somewhat with emission wavelength. Time-resolved emission spectra collected as a function of delay time following pulsed excitation exhibited significant shifts to higher energy as a function of time. These data support a photophysical model in which erythrosin B molecules are distributed among matrix sites that vary such that blue-emitting sites with slower rates of matrix dipolar relaxation also have slower rates of molecular collisions. The amorphous matrixes of lactose and lactitol in both the glass and the melt state are thus characterized by dynamic site heterogeneity in which different sites vary in terms of their overall molecular mobility.
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Affiliation(s)
- Sonali Shirke
- Department of Food Science, Rutgers, The State University of New Jersey, New Brunswick, NJ 08901-8520, USA
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You Y, Ludescher RD. Phosphorescence of erythrosin B as a robust probe of molecular mobility in amorphous solid sucrose. APPLIED SPECTROSCOPY 2006; 60:813-9. [PMID: 16854271 DOI: 10.1366/000370206777887107] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Luminescence from the triplet probe erythrosin B (tetra-iodo fluorescein, Ery B) provides spectroscopic characteristics such as lifetime and emission energy that are sensitive to molecular mobility of the local environment in amorphous solids. This study investigated how variations in the local concentration of Ery B free acid as well as the presence of the dispersing solvent affect the spectroscopic measurements of solid matrix properties (the free acid of Ery B is poorly soluble in water and thus must be introduced via an organic solvent). The emission energy of Ery B from 5 to 100 degrees C in thin films of amorphous sucrose at various probe and solvent (N,N-dimethyl formamide, DMF) concentrations was determined using excitation at 500 nm and emission over the range 520-750 nm. The emission lifetime was determined over the same temperature range using a stretched exponential analysis of intensity decays collected using excitation at 530 nm and emission at 680 nm. Variations in the probe/sucrose mole ratio (concentration) over the range from 0.5 to 10 x 10(-4) and 10-fold variations in the amount of DMF used to disperse the probe did not affect the emission energy, the shape of the emission spectra, or the measured lifetimes of Ery B in amorphous sucrose. These results thus indicate that erythrosin B introduced into amorphous solids can provide a robust measure of the intrinsic mobility of the solid matrix that is relatively insensitive to final probe concentration or presence of residual solvent.
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Affiliation(s)
- Yumin You
- Department of Food Science, Rutgers, The State University of New Jersey, 65 Dudley Road, New Brunswick, New Jersey 08901-8520, USA
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Shirke S, Ludescher RD. Molecular mobility and the glass transition in amorphous glucose, maltose, and maltotriose. Carbohydr Res 2005; 340:2654-60. [PMID: 16182264 DOI: 10.1016/j.carres.2005.08.016] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2005] [Accepted: 08/10/2005] [Indexed: 10/25/2022]
Abstract
We have used measurements of the phosphorescence intensity decay of the triplet probe erythrosin B, dispersed in amorphous glucose, maltose, and maltotriose at probe:sugar mole ratios of approximately 1:10(4), to monitor the molecular mobility of the sugar matrix in the glass and melt around the glass-transition temperature (Tg). Intensity decays were well fit using a stretched-exponential decay model in which the Kohlrausch-Williams-Watts lifetime tau and the stretching exponent beta are the physically meaningful parameters. When normalized to the glass-transition temperature, the erythrosin lifetime decreased in the order glucose>maltose>maltotriose. Analysis of the lifetime provided an estimate of the collisional quenching constant for deexcitation of the triplet state (kTS0); kTS0 increased in the order glucose<maltose<maltotriose over the range of T-Tg from about -40 to 50 degrees C. Although approximately constant in the glass, the magnitude of beta decreased around Tg in the order glucose>maltose>maltotriose, indicating that the lifetime heterogeneity increased in the order glucose<maltose<maltotriose. These data demonstrate that both the average rate of matrix molecular mobility and the width of the distribution of matrix mobility rates around the glass transition increase with an increase in the molecular size of the sugar in this homologous series.
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Affiliation(s)
- Sonali Shirke
- Department of Food Science, Rutgers, The State University of New Jersey, 65 Dudley Road, New Brunswick, NJ 08901-8520, USA
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Shirke S, Ludescher RD. Dynamic site heterogeneity in amorphous maltose and maltitol from spectral heterogeneity in erythrosin B phosphorescence. Carbohydr Res 2005; 340:2661-9. [PMID: 16212949 DOI: 10.1016/j.carres.2005.08.015] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2005] [Accepted: 08/10/2005] [Indexed: 10/25/2022]
Abstract
We have used phosphorescence from erythrosin B (tetraiodofluorescein) dispersed in thin films of either maltose or maltitol to investigate the physical properties of these amorphous pure sugar matrixes. Intensity decays collected as a function of emission wavelength over the range from 640 to 720 nm were analyzed using a stretched exponential kinetic model in which the lifetime (tau) and the stretching exponent (beta) were the physically relevant parameters. The lifetimes varied systematically with emission wavelength in both matrixes. Analysis of the temperature dependence of the lifetime at each wavelength provided an estimate of the activation energy for nonradiative quenching of the triplet state; the activation energy also varied with emission wavelength. In addition, time-resolved emission spectra exhibited a blue shift with time following excitation. These data support a photophysical model in which probes are distributed among sites that vary in terms of overall molecular mobility and in which sites with lower rates of dipolar relaxation also have lower rates of collisional quenching of the erythrosin triplet state. The amorphous matrix of both maltose and maltitol in both the glass and the melt state is thus characterized by dynamic site heterogeneity in which different sites vary in terms of their overall molecular mobility.
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Affiliation(s)
- Sonali Shirke
- Department of Food Science, Rutgers, The State University of New Jersey, New Brunswick, NJ 08901-8520, USA
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Shirke S, Takhistov P, Ludescher RD. Molecular Mobility in Amorphous Maltose and Maltitol from Phosphorescence of Erythrosin B. J Phys Chem B 2005; 109:16119-26. [PMID: 16853048 DOI: 10.1021/jp0521050] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We have used phosphorescence from erythrosin B (tetraiodofluorescein) dispersed in amorphous thin films of maltose and maltitol at mole ratios of 0.8:10(4) dye:sugar to monitor the molecular mobility of these matrixes over the temperature range from -25 to over 110 degrees C. Analysis of the emission peak frequency and bandwidth (full width at half-maximum) and time-resolved intensity decay parameters provided information about thermally activated modes of matrix mobility that enhanced the rate of dipolar relaxation around the triplet state and the rate of intersystem crossing to the ground state (k(TS0)). Detectable dipolar relaxation began in the glassy state about 50 degrees C below T(g) in both maltose and maltitol; the relaxation rate, however, while 3-4 orders of magnitude slower than literature values for the beta relaxation determined from dielectric relaxation, had an activation energy only 2-fold smaller. Dipolar relaxation was further enhanced in the melt above T(g); the dipolar relaxation rates in the melt scaled nearly exactly with rates for the alpha relaxation determined from dielectric relaxation. Intensity decays were well fit using a stretched exponential decay function in which the lifetime (tau) and the stretching exponent (beta) were the physically significant parameters. In maltose, the magnitude of k(TS0) was essentially constant in the glass and increased dramatically at the T(g); in maltitol k(TS0) increased moderately at T(g) = -50 degrees C and more dramatically in the melt at T(g) = +20 degrees C. The value of k(TS0) in maltose:maltitol mixtures was significantly smaller than that seen in pure maltose and maltitol, suggesting that specific interactions decreased the mobility of the mixed sugar matrix; this phenomenon was comparable to the antiplasticization seen in mixtures of small molecule plasticizers with synthetic polymers and starch. The extent of inhomogeneous broadening and dynamic heterogeneity were essentially constant in the glass and increased dramatically in maltose and more gradually in maltitol at the glass transition.
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Affiliation(s)
- Sonali Shirke
- Department of Food Science, Rutgers, The State University of New Jersey, New Brunswick, New Jersey 08901-8520, USA
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Buscaglia M, Kubelka J, Eaton WA, Hofrichter J. Determination of ultrafast protein folding rates from loop formation dynamics. J Mol Biol 2005; 347:657-64. [PMID: 15755457 DOI: 10.1016/j.jmb.2005.01.057] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2004] [Revised: 01/21/2005] [Accepted: 01/24/2005] [Indexed: 11/20/2022]
Abstract
Quenching of the triplet state of tryptophan by contact with cysteine can be used to measure the kinetics of loop formation in unfolded proteins. Here we show that cysteine quenching dynamics also provide a novel method for measuring folding rates when the exchange between folded and unfolded states is faster than the unquenched triplet lifetime (approximately 100 micros). We use this technique to investigate folding/unfolding kinetics of the 35 residue headpiece subdomain of the protein villin, which contains a single tryptophan residue and was engineered to contain a cysteine residue at the N terminus. At intermediate concentrations of denaturant the time-course of the triplet decay consists of two relaxations, the rates and amplitudes of which reveal the fast kinetics for folding and unfolding of this protein. The folding rates extracted using a simple kinetic model are close to those reported previously from laser-induced temperature-jump experiments that employ the change in tryptophan fluorescence as a probe. However, the results differ significantly from those reported from dynamic NMR line shape analysis on a variant with methionine at the N terminus, an issue that remains to be resolved. The analysis of the triplet quenching kinetics also shows that the quenching rates in the unfolded state increase with decreasing denaturant concentration, indicating a compaction of the unfolded protein.
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Affiliation(s)
- Marco Buscaglia
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Building 5, Bethesda, MD 20892-0520, USA
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Dad S, Bisby R, Clark I, Parker A. Identification and reactivity of the triplet excited state of 5-hydroxytryptophan. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY. B, BIOLOGY 2005; 78:245-51. [PMID: 15708522 PMCID: PMC1890304 DOI: 10.1016/j.jphotobiol.2004.11.013] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2004] [Revised: 11/22/2004] [Accepted: 11/22/2004] [Indexed: 11/28/2022]
Abstract
Both the neurotransmitter serotonin and the unnatural amino acid 5-hydroxytryptophan (5HT), contain the 5-hydroxyindole chromophore. The photochemistry of 5HT is being investigated in relation to the multiphoton excitation of this chromophore to produce a characteristic photoproduct with green fluorescence ('hyperluminescence'). Laser flash photolysis (308 nm) of 5HT in aqueous solution at neutral pH produces both the neutral 5-indoloxyl radical (lambda(max) 400-420 nm) and another transient absorption with lambda(max) 480 nm and lifetime of 2 micros in deaerated solutions. Based on quenching by oxygen and beta-carotene, the species at 480 nm is identified as the triplet excited state of 5HT. In acidic solution a new oxygen-insensitive intermediate with lambda(max) 460 is assigned to the radical cation of 5HT. Time-resolved measurements of luminescence at 1270 nm have shown that the triplet state of 5HT is able to react with oxygen to form singlet excited oxygen (1O2*) with a quantum yield of approximately 0.1. However, 5HT has also been found to be an effective quencher of singlet oxygen with a second order rate constant of 1.3 x 10(8) dm3 mol(-1) s(-1). The results are discussed in the light of recent observations on the multiphoton-excited photochemistry of serotonin.
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Affiliation(s)
- S. Dad
- Biosciences Research Institute, University of Salford, Salford M5 4WT, UK
| | - R.H. Bisby
- Biosciences Research Institute, University of Salford, Salford M5 4WT, UK
| | - I.P. Clark
- Lasers for Science Facility, CCLRC Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 0QX, UK
| | - A.W. Parker
- Lasers for Science Facility, CCLRC Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 0QX, UK
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Dashnau JL, Zelent B, Vanderkooi JM. Tryptophan interactions with glycerol/water and trehalose/sucrose cryosolvents: infrared and fluorescence spectroscopy and ab initio calculations. Biophys Chem 2004; 114:71-83. [PMID: 15792863 DOI: 10.1016/j.bpc.2004.10.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2004] [Revised: 10/13/2004] [Accepted: 10/14/2004] [Indexed: 10/26/2022]
Abstract
In order to correlate how the solvent affects emission properties of tryptophan, the fluorescence and phosphorescence emission spectra of tryptophan and indole model compounds were compared for solid sugar glass (trehalose/sucrose) matrix and glycerol/water solution and under the same conditions, these matrices were examined by infrared spectroscopy. Temperature was varied from 290 to 12 K. In sugar glass, the fluorescence and phosphorescence emission spectra are constant over this temperature range and the fluorescence remains red shifted; these results are consistent with the static interaction of OH groups with tryptophan in the sugar glass. In sugar glass containing water, the water retains mobility over the entire temperature range as indicated by the HOH infrared bending frequency. The fluorescence of tryptophan in glycerol/water shifts to the blue as temperature decreases and the frequency change of the absorption of the HOH bend mode is larger than in the sugar glass. These results suggest rearrangement of glycerol and water molecules over the entire temperature change. Shifts in the fluorescence emission maximum of indole and tryptophan were relatively larger than shifts for the phosphorescence emission-as expected for the relatively smaller excited triplet state dipole for tryptophan. The fluorescence emission of tryptophan in glycerol/water at low temperature has maxima at 312, 313, and 316 nm at pH 1.4, 7.0, and 10.6, respectively. The spectral shifts are interpreted to be an indication of a charge, or Stark phenomena, effect on the excited state molecule, as supported by ab initio calculations. To check whether the amino acid remains charged over the temperature range, the infrared spectrum of alanine was monitored over the entire range of temperature. The ratio of infrared absorption characteristic of carboxylate/carbonyl was constant in glycerol/water and sugar glass, which indicates that the charge was retained. Tryptophan buried in proteins, namely calcium parvalbumin from cod and aldolase from rabbit, showed temperature profiles of the fluorescence spectra that were largely independent of the solvent (glycerol/water or sugar glass) and temperature whereas the fluorescence and phosphorescence yields were dependent. The results demonstrate how the rich information found in tryptophan luminescence can provide information on the dipolar nature and dynamics of the matrix.
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Affiliation(s)
- Jennifer L Dashnau
- Johnson Research Foundation, Department of Biochemistry and Biophysics, School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
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Simon-Lukasik KV, Ludescher RD. Erythrosin B phosphorescence as a probe of oxygen diffusion in amorphous gelatin films. Food Hydrocoll 2004. [DOI: 10.1016/j.foodhyd.2003.09.006] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Tsentalovich YP, Snytnikova OA, Sagdeev RZ. Properties of excited states of aqueous tryptophan. J Photochem Photobiol A Chem 2004. [DOI: 10.1016/s1010-6030(03)00376-9] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Andersen JU, Cederquist H, Forster JS, Huber BA, Hvelplund P, Jensen J, Liu B, Manil B, Maunoury L, Brøndsted Nielsen S, Pedersen UV, Rangama J, Schmidt HT, Tomita S, Zettergren H. Photodissociation of protonated amino acids and peptides in an ion storage ring. Determination of Arrhenius parameters in the high-temperature limit. Phys Chem Chem Phys 2004. [DOI: 10.1039/b316845j] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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