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Slavova S, Antonov L. Azaindolizine proton cranes attached to 7-hydroxyquinoline and 3-hydroxypyridine: a comparative theoretical study. Phys Chem Chem Phys 2024; 26:7177-7189. [PMID: 38349360 DOI: 10.1039/d3cp04635d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/23/2024]
Abstract
Theoretical design of several proton cranes, based on 7-hydroxyquinoline and 3-hydroxypyridine as proton-transfer frames, has been attempted using ground and excited-state density functional theory (DFT) calculations in various environments. Imidazo[1,2-a]pyridine, pyrazolo[1,5-a]pyridine and benzimidazole were considered as proton crane units. The proton crane action requires the existence of a single enol-like form in the ground state, which under excitation goes to the end keto-like one through a series of consecutive excited-state intramolecular proton transfers (ESIPT) and twisting steps with the participation of a crane unit, resulting in a long-range intramolecular proton transfer. The results suggest that 3-hydroxypyridine is not suitable for a proton-transfer frame and 8-(imidazo[1,2-a]pyridin-2-yl)quinolin-7-ol and 8-(pyrazolo[1,5-a]pyridin-2-yl)quinolin-7-ol behave as non-conjugated proton cranes, instead of tautomeric re-arrangement in the latter, which was thought to be possible.
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Affiliation(s)
- Sofia Slavova
- Institute of Electronics, Bulgarian Academy of Sciences, 1784 Sofia, Bulgaria.
- Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
| | - Liudmil Antonov
- Institute of Electronics, Bulgarian Academy of Sciences, 1784 Sofia, Bulgaria.
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2
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Nijil S, Felicitus S, Kini S. Fluorometric investigation of boric acid-pyridoxal 5′ phosphate interaction: A turn-on-fluorescence assay for the detection of boric acid in water bodies and fetal bovine serum. Microchem J 2023; 194:109254. [DOI: 10.1016/j.microc.2023.109254] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2023]
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3
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García MJ, Kamaid A, Malacrida L. Label-free fluorescence microscopy: revisiting the opportunities with autofluorescent molecules and harmonic generations as biosensors and biomarkers for quantitative biology. Biophys Rev 2023; 15:709-719. [PMID: 37681086 PMCID: PMC10480099 DOI: 10.1007/s12551-023-01083-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2023] [Accepted: 06/19/2023] [Indexed: 09/09/2023] Open
Abstract
Over the past decade, the utilization of advanced fluorescence microscopy technologies has presented numerous opportunities to study or re-investigate autofluorescent molecules and harmonic generation signals as molecular biomarkers and biosensors for in vivo cell and tissue studies. The label-free approaches benefit from the endogenous fluorescent molecules within the cell and take advantage of their spectroscopy properties to address biological questions. Harmonic generation can be used as a tool to identify the occurrence of fibrillar or lipid deposits in tissues, by using second and third-harmonic generation microscopy. Combining autofluorescence with novel techniques and tools such as fluorescence lifetime imaging microscopy (FLIM) and hyperspectral imaging (HSI) with model-free analysis of phasor plots has revolutionized the understanding of molecular processes such as cellular metabolism. These tools provide quantitative information that is often hidden under classical intensity-based microscopy. In this short review, we aim to illustrate how some of these technologies and techniques may enable investigation without the need to add a foreign fluorescence molecule that can modify or affect the results. We address some of the most important autofluorescence molecules and their spectroscopic properties to illustrate the potential of these combined tools. We discuss using them as biomarkers and biosensors and, under the lens of this new technology, identify some of the challenges and potentials for future advances in the field.
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Affiliation(s)
- María José García
- Departamento de Fisiopatología, Hospital de Clínicas, Facultad de Medicina, Universidad de La República, Montevideo, Uruguay
- Advanced Bioimaging Unit, Institut Pasteur de Montevideo & Universidad de la República, Montevideo, Uruguay
| | - Andrés Kamaid
- Advanced Bioimaging Unit, Institut Pasteur de Montevideo & Universidad de la República, Montevideo, Uruguay
| | - Leonel Malacrida
- Departamento de Fisiopatología, Hospital de Clínicas, Facultad de Medicina, Universidad de La República, Montevideo, Uruguay
- Advanced Bioimaging Unit, Institut Pasteur de Montevideo & Universidad de la República, Montevideo, Uruguay
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Wu T, Liao J, Xiang F, Yu J, Gao Y, Liu L, Ye S, Li H, Shi K, Zheng W. Short-wavelength excitation two-photon intravital microscopy of endogenous fluorophores. BIOMEDICAL OPTICS EXPRESS 2023; 14:3380-3396. [PMID: 37497479 PMCID: PMC10368027 DOI: 10.1364/boe.493015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2023] [Revised: 05/21/2023] [Accepted: 05/22/2023] [Indexed: 07/28/2023]
Abstract
The noninvasive two-photon excitation autofluorescence imaging of cellular and subcellular structure and dynamics in live tissue could provide critical in vivo information for biomedical studies. However, the two-photon microscopy of short-wavelength endogenous fluorophores, such as tryptophan and hemoglobin, is extremely limited due to the lack of suitable imaging techniques. In this study, we developed a short-wavelength excitation time- and spectrum-resolved two-photon microscopy system. A 520-nm femtosecond fiber laser was used as the excitation source, and a time-correlated single-photon counting module connected with a spectrograph was used to provide time- and spectrum-resolved detection capability. The system was specially designed for measuring ultraviolet and violet-blue fluorescence signals and thus was very suitable for imaging short-wavelength endogenous fluorophores. Using the system, we systematically compared the fluorescence spectra and fluorescence lifetimes of short-wavelength endogenous fluorophores, including the fluorescent molecules tyrosine, tryptophan, serotonin (5-HT), niacin (vitamin B3), pyridoxine (vitamin B6), and NADH and the protein group (keratin, elastin, and hemoglobin). Then, high-resolution three-dimensional (3D) label-free imaging of different biological tissues, including rat esophageal tissue, rat oral cheek tissue, and mouse ear skin, was performed in vivo or ex vivo. Finally, we conducted time-lapse imaging of leukocyte migration in the lipopolysaccharide injection immunization model and a mechanical trauma immunization model. The results indicate that the system can specifically characterize short-wavelength endogenous fluorophores and provide noninvasive label-free 3D visualization of fine structures and dynamics in biological systems. The microscopy system developed here can empower more flexible imaging of endogenous fluorophores and provide a novel method for the 3D monitoring of biological events in their native environment.
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Affiliation(s)
- Ting Wu
- Research Center for Biomedical Optics and Molecular Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
- University of Chinese Academy of Sciences, No.19(A) Yuquan Road, Shijingshan District, Beijing 100049, China
- Shenzhen Key Laboratory for Molecular Imaging, Guangdong Provincial Key Laboratory of Biomedical Optical Imaging Technology, Shenzhen Institute of Advanced Technology, Shenzhen 518055, China
| | - Jiuling Liao
- Research Center for Biomedical Optics and Molecular Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
- Shenzhen Key Laboratory for Molecular Imaging, Guangdong Provincial Key Laboratory of Biomedical Optical Imaging Technology, Shenzhen Institute of Advanced Technology, Shenzhen 518055, China
| | - Feng Xiang
- Research Center for Biomedical Optics and Molecular Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
- Shenzhen Key Laboratory for Molecular Imaging, Guangdong Provincial Key Laboratory of Biomedical Optical Imaging Technology, Shenzhen Institute of Advanced Technology, Shenzhen 518055, China
| | - Jia Yu
- Research Center for Biomedical Optics and Molecular Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
- Shenzhen Key Laboratory for Molecular Imaging, Guangdong Provincial Key Laboratory of Biomedical Optical Imaging Technology, Shenzhen Institute of Advanced Technology, Shenzhen 518055, China
| | - Yufeng Gao
- Research Center for Biomedical Optics and Molecular Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
- Shenzhen Key Laboratory for Molecular Imaging, Guangdong Provincial Key Laboratory of Biomedical Optical Imaging Technology, Shenzhen Institute of Advanced Technology, Shenzhen 518055, China
| | - Lina Liu
- Research Center for Biomedical Optics and Molecular Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
- Shenzhen Key Laboratory for Molecular Imaging, Guangdong Provincial Key Laboratory of Biomedical Optical Imaging Technology, Shenzhen Institute of Advanced Technology, Shenzhen 518055, China
| | - Shiwei Ye
- Research Center for Biomedical Optics and Molecular Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
- Shenzhen Key Laboratory for Molecular Imaging, Guangdong Provincial Key Laboratory of Biomedical Optical Imaging Technology, Shenzhen Institute of Advanced Technology, Shenzhen 518055, China
| | - Hui Li
- Research Center for Biomedical Optics and Molecular Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
- Shenzhen Key Laboratory for Molecular Imaging, Guangdong Provincial Key Laboratory of Biomedical Optical Imaging Technology, Shenzhen Institute of Advanced Technology, Shenzhen 518055, China
| | - Kebin Shi
- State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-optoelectronics, School of Physics, Peking University, Beijing 100871, China
- National Biomedical Imaging Center, Peking University, Beijing 100871, China
| | - Wei Zheng
- Research Center for Biomedical Optics and Molecular Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
- Shenzhen Key Laboratory for Molecular Imaging, Guangdong Provincial Key Laboratory of Biomedical Optical Imaging Technology, Shenzhen Institute of Advanced Technology, Shenzhen 518055, China
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Pale, Djiedeu N, Lissouck D, Mbogning WF, Issac A, Owono LC, Kenfack CA. Impact of temperature and sunlight exposition on locally brewed beers composition revealed by fluorescence spectroscopy coupled with chemometric methods. J Food Sci 2021; 86:5175-5187. [PMID: 34778971 DOI: 10.1111/1750-3841.15962] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2021] [Revised: 10/06/2021] [Accepted: 10/08/2021] [Indexed: 11/28/2022]
Abstract
Fluorescence excitation-emission matrix (EEM) and synchronous scanning fluorescence (SF), coupled with parallel factor (PARAFAC) analysis, principal component analysis (PCA) and Linear discriminant analysis (LDA) methods were used to differentiate 49 lager beer samples and monitor the effects of temperature and sunlight exposition on their composition. EEMs were decomposed into independent fluorescent components. The beer samples were characterized by the presence of excitation/emission (exc/em) peaks at 290/350, 315/345, 340/410, 375/455, 360/420, 400/460, and 437/525 nm, which were ascribed, according to the known beer fluorescent components, respectively to aromatic amino acids, vitamin B6 (pyridoxal), vitamin B6 (pyridoxic acids), vitamin B3, iso-α-acids, vitamin B1, and vitamin B2. The variation of the relative concentration of iso-α-acids in the different beer brands presented the same trend with that of their relative IBU, thus revealing the potency of our method in the assessment of beer bitterness. The impact of temperature and sunlight was assessed by separately monitoring the modifications of the EEMs after 5 h exposition to 40°C temperature and sunlight respectively. Noticeably a variation of the peaks intensity of the iso-α-acids, carbonyl and polyphenols compounds were observed, accompanied by a decrease of the alcohol content, thus indicating beer aging. This method can be useful for the identification and monitoring of beer state during the technological production cycle and storage. PRACTICAL APPLICATION: The present work demonstrates the potency of the fluorescence technique used together with chemometric methods to give valuable information on beer bitterness. Development of rapid quantitative methods for beer bitterness assessment is of great importance for brewing industries.
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Affiliation(s)
- Pale
- Laboratoire Optique et Applications, Centre de Physique Atomique Moléculaire et Optique Quantique, Faculté des Sciences, Université de Douala, Douala, Littoral, 237, Cameroon
| | - Nicodème Djiedeu
- Laboratoire Optique et Applications, Centre de Physique Atomique Moléculaire et Optique Quantique, Faculté des Sciences, Université de Douala, Douala, Littoral, 237, Cameroon
| | - Daniel Lissouck
- Laboratoire Optique et Applications, Centre de Physique Atomique Moléculaire et Optique Quantique, Faculté des Sciences, Université de Douala, Douala, Littoral, 237, Cameroon.,Department of Renewable Energy, Higher Technical teachers' Training College, University of Buea, Kumba, Sud-west, 237, Cameroon
| | - William Feudjio Mbogning
- Laboratoire Optique et Applications, Centre de Physique Atomique Moléculaire et Optique Quantique, Faculté des Sciences, Université de Douala, Douala, Littoral, 237, Cameroon
| | - Adoum Issac
- Département de physique, Faculté des Sciences Exactes et Appliquées, Université de N'Djaména, N'Djaména, N'Djamena, 235, Chad
| | - Luc Calvin Owono
- Département de Physique, Ecole Normale Supérieure de Yaoundé, Université de Yaoundé I, Yaoundé, Centre, 237, Cameroon
| | - Cyril Assongo Kenfack
- Laboratoire Optique et Applications, Centre de Physique Atomique Moléculaire et Optique Quantique, Faculté des Sciences, Université de Douala, Douala, Littoral, 237, Cameroon
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D-Cycloserine destruction by alanine racemase and the limit of irreversible inhibition. Nat Chem Biol 2020; 16:686-694. [PMID: 32203411 PMCID: PMC7246083 DOI: 10.1038/s41589-020-0498-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2019] [Accepted: 02/06/2020] [Indexed: 11/08/2022]
Abstract
The broad-spectrum antibiotic D-cycloserine (DCS) is a key component of regimens used to treat multi- and extensively drug-resistant tuberculosis. DCS, a structural analog of D-alanine, binds to and inactivates two essential enzymes involved in peptidoglycan biosynthesis, alanine racemase (Alr) and D-Ala:D-Ala ligase. Inactivation of Alr is thought to proceed via a mechanism-based irreversible route, forming an adduct with the pyridoxal 5'-phosphate cofactor, leading to bacterial death. Inconsistent with this hypothesis, Mycobacterium tuberculosis Alr activity can be detected after exposure to clinically relevant DCS concentrations. To address this paradox, we investigated the chemical mechanism of Alr inhibition by DCS. Inhibition of M. tuberculosis Alr and other Alrs is reversible, mechanistically revealed by a previously unidentified DCS-adduct hydrolysis. Dissociation and subsequent rearrangement to a stable substituted oxime explains Alr reactivation in the cellular milieu. This knowledge provides a novel route for discovery of improved Alr inhibitors against M. tuberculosis and other bacteria.
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8
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Efficient separation of mannan–protein mixtures by ionic liquid aqueous two-phase system, comparison with lectin affinity purification. Int J Biol Macromol 2017; 98:314-318. [DOI: 10.1016/j.ijbiomac.2017.02.001] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2016] [Revised: 01/12/2017] [Accepted: 02/01/2017] [Indexed: 01/04/2023]
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Abstract
According to the World Health Organization (WHO), infants should be exclusively breastfed for the first six months of life. However, there is insufficient information about the concentration of nutrients in human milk. For some nutrients, including B-vitamins, maternal intake affects their concentration in human milk but the extent to which inadequate maternal diets affect milk B-vitamin content is poorly documented. Little is known about infant requirements for B-vitamins; recommendations are generally set as Adequate Intakes (AI) calculated on the basis of the mean volume of milk (0.78 L/day) consumed by infants exclusively fed with human milk from well-nourished mothers during the first six months, and the concentration of each vitamin in milk based on reported values. Methods used for analyzing B-vitamins, commonly microbiological, radioisotope dilution or more recently chromatographic, coupled with UV, fluorometric and MS detection, have rarely been validated for the complex human milk matrix. Thus the validity, accuracy, and sensitivity of analytical methods is important for understanding infant requirements for these nutrients, the maternal intakes needed to support adequate concentrations in breast milk. This review summarizes current knowledge on methods used for analyzing the B-vitamins thiamin, riboflavin, niacin, vitamin B-6 and pantothenic acid, vitamin B-12, folate, biotin, and choline in human milk, their chemical and physical properties, the different forms and changes in concentration during lactation, and the effects of deficiency on the infant.
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Affiliation(s)
| | - Lindsay H Allen
- a USDA, ARS Western Human Nutrition Research Center , Davis , California , USA
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Schießl IM, Castrop H. Deep insights: intravital imaging with two-photon microscopy. Pflugers Arch 2016; 468:1505-16. [PMID: 27352273 DOI: 10.1007/s00424-016-1832-7] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2016] [Accepted: 04/26/2016] [Indexed: 01/03/2023]
Abstract
Intravital multiphoton microscopy is widely used to assess the structure and function of organs in live animals. Although different tissues vary in their accessibility for intravital multiphoton imaging, considerable progress has been made in the imaging quality of all tissues due to substantial technical improvements in the relevant imaging components, such as optics, excitation laser, detectors, and signal analysis software. In this review, we provide an overview of the technical background of intravital multiphoton microscopy. Then, we note a few seminal findings that were made through the use of multiphoton microscopy. Finally, we address the technical limitations of the method and provide an outlook for how these limitations may be overcome through future technical developments.
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Affiliation(s)
- Ina Maria Schießl
- Institute of Physiology, University of Regensburg, Universitätsstr. 31, 93040, Regensburg, Germany.
| | - Hayo Castrop
- Institute of Physiology, University of Regensburg, Universitätsstr. 31, 93040, Regensburg, Germany
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11
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Wang Y, Yin H, Shi Y, Jin M, Ding D. Ground-state and excited-state multiple proton transfer via a hydrogen-bonded water wire for 3-hydroxypyridine. NEW J CHEM 2014. [DOI: 10.1039/c4nj00458b] [Citation(s) in RCA: 75] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The multiple proton transfer reactions of 3-hydroxypyridine-(H2O)3 have been demonstrated, and a perfect proton transfer cycle has been revealed in the ground and excited states.
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Affiliation(s)
- Ye Wang
- Institute of Atomic and Molecular Physics
- Jilin University
- Changchun 130012, China
| | - Hang Yin
- Institute of Atomic and Molecular Physics
- Jilin University
- Changchun 130012, China
| | - Ying Shi
- Institute of Atomic and Molecular Physics
- Jilin University
- Changchun 130012, China
| | - Mingxing Jin
- Institute of Atomic and Molecular Physics
- Jilin University
- Changchun 130012, China
| | - Dajun Ding
- Institute of Atomic and Molecular Physics
- Jilin University
- Changchun 130012, China
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Akdag A, Havlas Z, Michl J. Search for a small chromophore with efficient singlet fission: biradicaloid heterocycles. J Am Chem Soc 2012; 134:14624-31. [PMID: 22876879 DOI: 10.1021/ja3063327] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Of the five small biradicaloid heterocycles whose S(1), S(2), T(1), and T(2) adiabatic excitation energies were examined by the CASPT2/ANO-L-VTZP method, two have been found to meet the state energy criterion for efficient singlet fission and are recommended to the attention of synthetic chemists and photophysicists.
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Affiliation(s)
- Akin Akdag
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, 16110 Prague 2, Flemingovo nám. 2, Czech Republic
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Hill MP, Carroll EC, Vang MC, Addington TA, Toney MD, Larsen DS. Light-enhanced catalysis by pyridoxal phosphate-dependent aspartate aminotransferase. J Am Chem Soc 2010; 132:16953-61. [PMID: 21058708 PMCID: PMC3021986 DOI: 10.1021/ja107054x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The mechanisms of pyridoxal 5'-phosphate (PLP)-dependent enzymes require substrates to form covalent "external aldimine" intermediates, which absorb light strongly between 410 and 430 nm. Aspartate aminotransferase (AAT) is a prototypical PLP-dependent enzyme that catalyzes the reversible interconversion of aspartate and α-ketoglutarate with oxalacetate and glutamate. From kinetic isotope effects studies, it is known that deprotonation of the aspartate external aldimine C(α)-H bond to give a carbanionic quinonoid intermediate is partially rate limiting in the thermal AAT reaction. We show that excitation of the 430-nm external aldimine absorption band increases the steady-state catalytic activity of AAT, which is attributed to the photoenhancement of C(α)-H deprotonation on the basis of studies with Schiff bases in solution. Blue light (250 mW) illumination gives an observed 2.3-fold rate enhancement for WT AAT activity, a 530-fold enhancement for the inactive K258A mutant, and a 58600-fold enhancement for the PLP-Asp Schiff base in water. These different levels of enhancement correlate with the intrinsic reactivities of the C(α)-H bond in the different environments, with the less reactive Schiff bases exhibiting greater enhancement. Time-resolved spectroscopy, ranging from femtoseconds to minutes, was used to investigate the nature of the photoactivation of C(α)-H bond cleavage in PLP-amino acid Schiff bases both in water and bound to AAT. Unlike the thermal pathway, the photoactivation pathway involves a triplet state with a C(α)-H pK(a) that is estimated to be between 11 and 19 units lower than the ground state for the PLP-Val Schiff base in water.
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Affiliation(s)
- Melissa P. Hill
- Department of Chemistry, University of California, Davis, One Shields Avenue, Davis, CA 95616
| | - Elizabeth C. Carroll
- Department of Chemistry, University of California, Davis, One Shields Avenue, Davis, CA 95616
| | - Mai C. Vang
- Department of Chemistry, University of California, Davis, One Shields Avenue, Davis, CA 95616
| | - Trevor A. Addington
- Department of Chemistry, University of California, Davis, One Shields Avenue, Davis, CA 95616
| | - Michael D. Toney
- Department of Chemistry, University of California, Davis, One Shields Avenue, Davis, CA 95616
| | - Delmar S. Larsen
- Department of Chemistry, University of California, Davis, One Shields Avenue, Davis, CA 95616
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15
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Bueno C, Pavez P, Salazar R, Encinas MV. Photophysics and photochemical studies of the vitamin B6 group and related derivatives. Photochem Photobiol 2009; 86:39-46. [PMID: 19930123 DOI: 10.1111/j.1751-1097.2009.00643.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The photophysics and photochemical properties of vitamin B6 constituents and analogs were studied as function of pH and solvent. The pK of the phenolic oxygen and the pyridine ring nitrogen depends on the electron donor-acceptor ability of the 4-substituent, and agrees with the calculated proton affinity. For all studied compounds, the fluorescence properties showed that the phenolic oxygen is 8 units more acidic in the lowest singlet excited state than in the ground state. The pyridine N-atom is slightly more basic in the excited state. At pH of biological significance, pH 6-8, pyridoxamine and 4-pyridoxic acid are the more efficient chromophores with higher fluorescence yield and longer lifetime. Spectroscopic studies showed that the tautomeric equilibrium depends on the nature of the 4-substituent. The quenching of the singlet excited state of pyridoxamine and 4-pyridoxic acid by amino acids, free or in a peptide, and DNA bases at pH 7 was studied by time-resolved fluorescence techniques. The quenching rate constants are well correlated with the redox properties of the pyridoxinic compound and amino acids, and are related to the free energy change in the electron transfer process. Guanosine and pyrimidine bases also are efficient quenchers, involving an electron transfer reaction.
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Affiliation(s)
- Claudia Bueno
- Facultad de Química y Biología, Universidad de Santiago de Chile, Santiago, Chile
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Cañada-Cañada F, Espinosa-Mansilla A, Peña AMDL, Girón AJ, González-Gómez D. Determination of danofloxacin in milk combining second-order calibration and standard addition method using excitation–emission fluorescence data. Food Chem 2009. [DOI: 10.1016/j.foodchem.2008.08.032] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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17
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Hill MP, Carroll EC, Toney MD, Larsen DS. Rapid photodynamics of vitamin B6 coenzyme pyridoxal 5'-phosphate and its Schiff bases in solution. J Phys Chem B 2008; 112:5867-73. [PMID: 18416573 DOI: 10.1021/jp7117345] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The active form of vitamin B6, pyridoxal 5'-phosphate (PLP), is an important cofactor for numerous enzymes in amine and amino acid metabolism. Presented here is the first femtosecond transient absorption study of free PLP and two Schiff bases, PLP-valine and PLP-alpha-aminoisobutyric acid (AIB), in solution. Photoexcitation of free PLP leads to efficient triplet formation with an internal conversion rate that increases with increasing pH. The measured excited-state kinetics of the PLP-valine Schiff base exhibits a dramatic deuterium dependence as a result of excited-state proton transfer (ESPT) of the Calpha hydrogen in the amino acid substrate. This is consistent with formation of the key reaction carbanionic intermediate (quinonoid), which is resonance stabilized by the electron-deficient, conjugated pi system of the Schiff base/pyridine ring. The transient absorption signals of the PLP-Schiff base with alpha-methylalanine (2-aminoisobutyric acid), which does not have a Calpha proton, lack an observable deuterium effect, verifying ESPT formation of the quinonoid intermediate. In contrast to previous studies, no dependence on the excitation wavelength of the femtosecond kinetics is observed with PLP or PLP-valine, which suggests that a rapid (<250 fs) tautomerization occurs between the enolimine (absorbing at 330 nm) and ketoenamine (absorbing at 410 nm) tautomers in solution.
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Affiliation(s)
- Melissa P Hill
- Department of Chemistry, University of California, Davis, One Shields Avenue, Davis, California 95616, USA
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19
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Sharif S, Huot MC, Tolstoy PM, Toney MD, Jonsson KHM, Limbach HH. 15N nuclear magnetic resonance studies of acid-base properties of pyridoxal-5'-phosphate aldimines in aqueous solution. J Phys Chem B 2007; 111:3869-76. [PMID: 17388551 DOI: 10.1021/jp067334g] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
By use of 15N NMR spectroscopy, we have measured the pKa values of the aldimines 15N-(pyridoxyl-5'-phosphate-idine)-methylamine (2a), N-(pyridoxyl-5'-phosphate-15N-idine)-methylamine (2b), and 15N-(pyridoxyl-idine)-methylamine (3). These aldimines model the cofactor pyridoxal-5'-phosphate (PLP, 1) in a variety of PLP-dependent enzymes. The acid-base properties of the aldimines differ substantially from those of the free cofactor in the aldehyde form 1a or in the hydrated form 1b, which were also investigated using 15N NMR for comparison. All compounds contain three protonation sites, the pyridine ring, the phenol group, and the side chain phosphate (1, 2) or hydroxyl group (3). In agreement with the literature, 1a exhibits one of several pKas at 2.9 and 1b at 4.2. The 15N chemical shifts indicate that the corresponding deprotonation occurs partially in the pyridine and partially in the phenolic site, which compete for the remaining proton. The equilibrium constant of this ring-phenolate tautomerism was measured to be 0.40 for 1a and 0.06 for 1b. The tautomerism is essentially unaltered above pH 6.1, where the phosphate group is deprotonated to the dianion. This means that the pyridine ring is more basic than the phenolate group. Pyridine nitrogen deprotonation occurs at 8.2 for 1a and at 8.7 for 1b. By contrast, above pH 4 the phosphate site of 2 is deprotonated, while the pyridine ring pKa is 5.8. The Schiff base nitrogen does not deprotonate below pH 11.4. When the phosphate group is removed, the pKa of the Schiff base nitrogen decreases to 10.5. The phenol site cannot compete for the proton of the Schiff base nitrogen and is present in the entire pH range as a phenolate, preferentially hydrogen bonded to the solvent. The intrinsic 15N chemical shifts provide information about the hydrogen bond structures of the protonated and unprotonated species involved. Evidence is presented that the intramolecular OHN hydrogen bond of PLP aldimines is broken in aqueous solution. The coupling between the inter- and intramolecular OHN hydrogen bonds is also lost in this environment. The pyridine ring of the PLP aldimines is not protonated in aqueous solution near neutral pH. The basicity of the aldimine nitrogens would be even lower without the doubly negatively charged phosphate group. Protonation of both the Schiff base and pyridine nitrogens has been discussed as a prerequisite for catalytic activity, and the implications of the present findings for PLP catalysis are discussed.
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Affiliation(s)
- Shasad Sharif
- Institut für Chemie und Biochemie, Takustrasse 3, Freie Universität Berlin, D-14195 Berlin, Germany
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Durán Merás I, Espinosa-Mansilla A, Rodríguez DA. Complexation study of cinalukast and montelukast with cyclodextrines. J Pharm Biomed Anal 2007; 43:1025-32. [PMID: 17118608 DOI: 10.1016/j.jpba.2006.10.007] [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: 06/05/2006] [Revised: 10/02/2006] [Accepted: 10/04/2006] [Indexed: 11/27/2022]
Abstract
A fluorimetric study on the spectral characteristics of two antileukotrienes, cinalukast and montelukast, has been performed. Ionization constants of both of them have been photometrically calculated. Cinalukast pK(a) in ethanol:water 50:50 (v/v) medium resulted to be 2.2+/-0.1. Because the spectral characteristics of montelukast are widely affected by the solvent nature, pK(a) was estimated in two different ethanol:water media, 70:30 (v/v) and 10:90 (v/v) and the values calculated were pK(a)=2.9+/-0.1, and pK(a1)=2.0+/-0.1 and pK(a2)=6.5+/-0.1, respectively. It has been proven that the fluorescence of both, cinalukast and montelukast, is significantly intensified in the presence of cyclodextrins (CyDs). The host-guest complexation processes between cinalukast and alpha-CyD or heptakis-(2,6-di-O-methyl)-beta-cyclodextrin (DIMEB) and between montelukast and DIMEB have been investigated by fluorescence spectroscopy. A 1:1 stoichiometric ratio was established for the three studied inclusion complexes. The changes produced on the fluorescence of cinalukast or montelukast, when they are included on the hydrophobic CyD cavity are used to calculate their association constants by a non-linear regression method. Semiempirical MO calculations using AM1 method were performed in order to characterize the studied inclusion complexes. A new method for cinalukast determination in human serum, based on the fluorescence of the complex cinalukast-DIMEB exhibiting limit of detection of 7.95 ng mL(-1) has been proposed with satisfactory results. Adequate recovery values between 95 and 103% were calculated at five different concentration levels.
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Affiliation(s)
- I Durán Merás
- Department of Analytical Chemistry, University of Extremadura, 06071 Badajoz, Spain.
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Counts KG, Wong I, Oliveira MA. Investigating the Geminal Diamine Intermediate of Yersinia pestis Arginine Decarboxylase with Substrate, Product, and Inhibitors Using Single Wavelength Stopped-Flow Spectroscopy. Biochemistry 2006; 46:379-86. [PMID: 17209548 DOI: 10.1021/bi061260h] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The reaction mechanism of Yersinia pestis arginine decarboxylase has been investigated using a series of substrate, product, and inhibitors. Using single wavelength stopped-flow spectroscopy, novel mechanistic features were noted in the presence of the product, agmatine. By focusing on the excitation and emission wavelengths of the geminal diamine intermediate, we were able to monitor the formation and decay of two different geminal diamine species. Experiments revealed that the enzyme exists in two different conformational states--one that binds ligand and one that does not. The on and off rates for the conversion between the two conformational states was determined to be 390 s-1 and 880 s-1, respectively. The KD for agmatine binding was 6 mM. In addition, experiments revealed a pH-dependent conversion between two states of the enzyme. The deprotonated form of the enzyme binds ligand more slowly than the protonated form. The rates for the formation of the geminal diamine and external aldimine in this pathway were determined to be 25 and 4 s-1, respectively. There is also a slow interconversion between the protonated and deprotonated enzymes that has a pKa of approximately 8.0. Finally, the formation of the geminal diamine was determined to be Mg2+-dependent.
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Affiliation(s)
- Korie G Counts
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, Lexington, USA
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López-fernández MA, Gómez-hens A, Pérez-bendito D. Kinetic Fluorimetric Determination of Traces of Nickel by its Catalytic Effect on the Oxidation of Pyridoxal Hydrazone by Potassium Peroxidisulphate. ANAL LETT 2006. [DOI: 10.1080/00032718408065298] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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23
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Rubio S, Gómez-Hens A, Valcárcel M. Spectrofluorimetric Determination of Nitrite with Pyridoxal-5-Phosphate-2-Pyridylhydrazone. ANAL LETT 2006. [DOI: 10.1080/00032718408069092] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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24
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Dogra S. Spectral characteristics of 2-hydroxynicotinic acid: effects of solvent and acid or base concentrations. J Mol Struct 2005. [DOI: 10.1016/j.molstruc.2004.10.060] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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26
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Dogra S. Spectral characteristics of 2-(2′-hydroxy-3′-pyridyl)benzimidazole: effects of solvents and acid or base concentrations. J Mol Struct 2005. [DOI: 10.1016/j.molstruc.2004.08.025] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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27
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Balamurali M, Dogra S. Photophysics of 2-(6′-hydroxy-3′-pyridyl)benzimidazole: effect of solvents and acid–base concentrations. J Mol Struct 2004. [DOI: 10.1016/j.molstruc.2004.03.053] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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28
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Del Vado MAG, Rodríguez Cardona AF, Echevarría GR, Santos Blanco JG, Zumel CL, Blanco FG. Determination of the rate of formation of the schiff bases of pyridoxal 5′-phosphate with polyallylamine. INT J CHEM KINET 2004. [DOI: 10.1002/kin.550270910] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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29
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Allen MW, Unruh JR, Slaughter BD, Pyszczynski SJ, Hellwig TR, Kamerzell TJ, Johnson CK. Spectroscopy and Photophysics of Indoline and Indoline-2-Carboxylic Acid. J Phys Chem A 2003. [DOI: 10.1021/jp027813p] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Michael W. Allen
- University of Kansas, Department of Chemistry, 1251 Wescoe Hall Drive, Lawrence, Kansas 66045
| | - Jay R. Unruh
- University of Kansas, Department of Chemistry, 1251 Wescoe Hall Drive, Lawrence, Kansas 66045
| | - Brian D. Slaughter
- University of Kansas, Department of Chemistry, 1251 Wescoe Hall Drive, Lawrence, Kansas 66045
| | - Sarah J. Pyszczynski
- University of Kansas, Department of Chemistry, 1251 Wescoe Hall Drive, Lawrence, Kansas 66045
| | - Thaddaus R. Hellwig
- University of Kansas, Department of Chemistry, 1251 Wescoe Hall Drive, Lawrence, Kansas 66045
| | - Tim J. Kamerzell
- University of Kansas, Department of Chemistry, 1251 Wescoe Hall Drive, Lawrence, Kansas 66045
| | - Carey K. Johnson
- University of Kansas, Department of Chemistry, 1251 Wescoe Hall Drive, Lawrence, Kansas 66045
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Zipfel WR, Williams RM, Christie R, Nikitin AY, Hyman BT, Webb WW. Live tissue intrinsic emission microscopy using multiphoton-excited native fluorescence and second harmonic generation. Proc Natl Acad Sci U S A 2003; 100:7075-80. [PMID: 12756303 PMCID: PMC165832 DOI: 10.1073/pnas.0832308100] [Citation(s) in RCA: 1067] [Impact Index Per Article: 50.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Multicolor nonlinear microscopy of living tissue using two- and three-photon-excited intrinsic fluorescence combined with second harmonic generation by supermolecular structures produces images with the resolution and detail of standard histology without the use of exogenous stains. Imaging of intrinsic indicators within tissue, such as nicotinamide adenine dinucleotide, retinol, indoleamines, and collagen provides crucial information for physiology and pathology. The efficient application of multiphoton microscopy to intrinsic imaging requires knowledge of the nonlinear optical properties of specific cell and tissue components. Here we compile and demonstrate applications involving a range of intrinsic molecules and molecular assemblies that enable direct visualization of tissue morphology, cell metabolism, and disease states such as Alzheimer's disease and cancer.
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Affiliation(s)
- Warren R Zipfel
- Department of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853, USA
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31
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Metzler DE, Metzler CM, Sauke DJ. Light and Life. Biochemistry 2001. [DOI: 10.1016/b978-012492543-4/50026-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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32
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Durán Merás I, Galeano Díaz T, Salinas López F, Rodríguez Cacéres MI. Determination of piromidic acid residues in trout muscle tissue and in urine by liquid chromatography with post-column modification of pH and fluorimetric detection. JOURNAL OF CHROMATOGRAPHY. B, BIOMEDICAL SCIENCES AND APPLICATIONS 1998; 718:135-41. [PMID: 9832370 DOI: 10.1016/s0378-4347(98)00332-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
A rapid high-performance liquid chromatographic method has been developed to determine piromidic acid in trout muscle tissue and in urine, in the presence of nalidixic, 7-hydroxymethylnalidixic, oxolinic and pipemidic acids and cinoxacin. A Nova-Pak C18 column was used with acetonitrile-4x10(-4) M oxalic acid (40:60, v/v) as the mobile phase. A post-column change of pH was made with NaOH. Fluorimetric detection at 456 nm (lambda ex 275 nm) was used. The instrumental detection limit was 5.91 ng/ml, based on height of peak. Pretreatment of the urine samples was not necessary and fish samples were extracted with sodium hydroxide solutions and cleaned by means of an extraction with chloroform. Detection limit was 147 ng/ml for urine and 5.91 ng/g for trout muscle. Good separation without interference from any other components was obtained. Recovery was better than 87% in urine and better than 72% in trout muscle tissue.
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Affiliation(s)
- I Durán Merás
- Department of Analytical Chemistry, University of Extremadura, Badajoz, Spain
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33
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Echevarria GR, Catalán J, Bianco FG. Photophysical Study of Pyridoxal 5'-Phosphate and Its Schiff Base with n-Hexylamine. Photochem Photobiol 1997. [DOI: 10.1111/j.1751-1097.1997.tb03229.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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34
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Drakopoulos AI, Ioannou PC. Spectrofluorimetric study of the acid–base equilibria and complexation behavior of the fluoroquinolone antibiotics ofloxacin, norfloxacin, ciprofloxacin and pefloxacin in aqueous solution. Anal Chim Acta 1997. [DOI: 10.1016/s0003-2670(97)00465-0] [Citation(s) in RCA: 93] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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35
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Interconvertible of a vitamin B6 coenzyme analog derived from pyridoxal 5′-phosphate and rhodanine. Tetrahedron 1996. [DOI: 10.1016/0040-4020(96)00917-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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36
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Abstract
The interaction of light within tissue has been used to recognize disease since the mid-1800s. The recent developments of small light sources, detectors, and fiber optic probes provide opportunities to quantitatively measure these interactions, which yield information for diagnosis at the biochemical, structural, or (patho)physiological level within intact tissues. However, because of the strong scattering properties of tissues, the reemitted optical signal is often influenced by changes in biochemistry (as detected by these spectroscopic approaches) and by physiological and pathophysiological changes in tissue scattering. One challenge of biomedical optics is to uncouple the signals influenced by biochemistry, which themselves provide specificity for identifying diseased states, from those influenced by tissue scattering, which are typically unspecific to a pathology. In this review, we describe optical interactions pursued for biomedical applications (fluorescence, fluorescence lifetime, phosphorescence, and Raman from cells, cultures, and tissues) and then provide a descriptive framework for light interaction based upon tissue absorption and scattering properties. Finally, we review important endogenous and exogenous biological chromophores and describe current work to employ these signals for detection and diagnosis of disease.
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Affiliation(s)
- R Richards-Kortum
- Biomedical Engineering Program, University of Texas at Austin 78712, USA
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37
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Photometric and fluorimetric study of the acid-base behavior of 2,2'-diquinolyl and 2,2',2″-terpyridyl. J Fluoresc 1996; 6:97-102. [PMID: 24227083 DOI: 10.1007/bf00732048] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/1994] [Accepted: 05/02/1996] [Indexed: 10/26/2022]
Abstract
A photometric and fluorimetric study of the acid-base behavior of 2,2'-diquinolyl and 2,2',2″-terpyridyl was performed. In sulfuric acid medium, the doubly charged 2,2'-diquinolynium ion undergoes the first dissociation atH 0=0.20±0.09, as determined by fluorimetry (λex=336 nm, λem=424 nm). Photometric titration is less accurate because of the overlapping of the absorption spectra. The second dissociation constant of 2,2'-diquinolyl was determined by fluorimetric titration (λex=336 nm, λem=420 nm), obtaining a value of 3.67±0.03. The triply charged 2,2',2″-terpyridyl molecule was found to undergo the first dissociation atH 0=-7.17±0.04, as determined by fluorimetric titration (λex=316 nm, λem=350 nm), in aqueous sulfuric acid medium. Photometric titration (λ=335 nm) was performed in the presence of 6.5% ethanol because of the low solubility of the compound in water. In this ethanolic∶water medium, a value of the dissociation constant atH 0=-7.39±0.03 was calculated. The second dissociation constant was determined to be 2.81±0.12 by photometric titration at 285 nm, and values of 4.03±0.26 and 4.16±0.20 were found for the third dissociation constant by photometric titrations at 320 and 295 nm, in 10% ethanol, in close agreement with previously reported values. The fluorimetric titration profile obtained by exciting at 274 nm and measuring the fluorescence emission at 350 nm, in the zone betweenH 0=-3 and pH=10, is complicated by the several equilibria involved.
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Pineda T, Lopez-Cozar M, Sevilla J, Blazquez M. Electrochemical reduction of the final product of vitamin B-6 catabolism: a spectroscopic characterization of the reduced products of 4-pyridoxic acid. J Electroanal Chem (Lausanne) 1996. [DOI: 10.1016/0022-0728(95)04217-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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39
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Vázquez Segura MA, Donoso J, Muñoz F, García Blanco F, García del Vado MA, Echevarría G. Photophysical study of the Schiff bases of 5'-deoxypyridoxal and n-hexylamine in cationic micelles. Photochem Photobiol 1994; 60:399-404. [PMID: 7800712 DOI: 10.1111/j.1751-1097.1994.tb05123.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The absorption and fluorescence spectra of the Schiff bases formed between 5'-deoxypyridoxal and n-hexylamine in aqueous media containing different concentrations of the cationic surfactant hexadecyltrimethylammonium bromide were recorded at 25 degrees C. The quantum yields of fluorescence of the different zwitterionic and enol forms of the chemical species of the Schiff bases occurring in media of pH 4.5-8.5 were determined. Also, the fluorescence quenching resulting from the presence of the surfactant and that of iodide ion were analyzed. From the results obtained it follows that the zwitterionic forms do not interact with the cationic surfactant, whereas the enol forms do interact with it.
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Affiliation(s)
- M A Vázquez Segura
- Department of Chemistry, Faculty of Sciences, University of the Balearic Islands, Palma de Mallorca, Spain
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40
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Simultaneous determination of naproxen and its desmethyl metabolite in human serum by second-derivative synchronous fluorescence spectrometry. Anal Chim Acta 1994. [DOI: 10.1016/0003-2670(94)80037-5] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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41
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Determination of the rates of formation and hydrolysis of the Schiff bases formed by pyridoxal and poly-l-lysine. ACTA ACUST UNITED AC 1994. [DOI: 10.1016/0304-5102(93)e0236-a] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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42
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Durán-Merás I, de la Peña AM, Salinas F, Cáceres IR. Spectrofluorimetric determination of nalidixic acid based on host–guest complexation with γ-cyclodextrin. Analyst 1994. [DOI: 10.1039/an9941901215] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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43
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Segura MAV, Donoso J, Muñoz F, Piérola INÉSF, Blanco FG, Echevarria GR. SOLVENT EFFECTS ON THE TAUTOMERIZATION OF 5'-DEOXYPYRIDOXAL. A PHOTOPHYSICAL STUDY. Photochem Photobiol 1993. [DOI: 10.1111/j.1751-1097.1993.tb02950.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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44
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Sevilla JM, Blazquez M, Dominguez M, García-Blanco F. A study of the Schiff base formed between pyridoxal-5′-phosphate and poly-L-lysine of low polymerization degree. ACTA ACUST UNITED AC 1992. [DOI: 10.1039/p29920000921] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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45
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Vázquez MA, Muñoz F, Donoso J, García Blanco F. Spectroscopic study of the Schiff bases of dodecylamine with pyridoxal 5'-phosphate and 5'-deoxypyridoxal. A model for the Schiff bases of pyridoxal 5'-phosphate in biological systems. Biochem J 1991; 279 ( Pt 3):759-67. [PMID: 1953669 PMCID: PMC1151511 DOI: 10.1042/bj2790759] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
We recorded the absorption spectra of the Schiff bases of pyridoxal 5'-phosphate (PLP) and 5'-deoxypyridoxal (DPL) with dodecylamine (DOD) at different pH values. By applying deconvolution techniques to the spectra and analysing their different components we found that the above-mentioned Schiff bases in aqueous solutions of pH 7 adopted a conformation in which the pyridine ring is embedded in a very hydrophobic medium from which water is virtually completely excluded. This conformation in the same as that adopted by PLP when it acts as coenzyme for some enzymes such as glycogen phosphorylase. The experimental results obtained also show such a conformation to be highly favoured but sensitive to the protonation of the pyridine nitrogen, which makes the aromatic ring more readily accessible to the solvent.
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Affiliation(s)
- M A Vázquez
- Departmento de Química, Facultad de Ciencias, Universitad de las Islas Baleares, Palma de Mallorca, Spain
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Vázquez M, Muñoz F, Donoso J, Blanco F. Amino acid catalytic effect on the transamination reaction between pyridoxal 5′-phosphate and L-serine. ACTA ACUST UNITED AC 1991. [DOI: 10.1016/0304-5102(91)80064-a] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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47
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Ledbetter JW, Lindroth JR, Martin SM. The Fourier transforms of the laser-induced absorption decay from glycogen phosphorylase and DOPA decarboxylase. Biophys Chem 1988; 31:259-67. [PMID: 3233299 DOI: 10.1016/0301-4622(88)80031-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Fourier analysis of the laser-induced absorption decay curves of 3,4-dihydroxyphenylalanine (DOPA) decarboxylase and glycogen phosphorylase demonstrates a powerful technique in the analysis of complicated decay behavior. Phosphorylase which uses the pyridoxal 5'-phosphate cofactor in an unknown manner exhibits over weak absorption an intense decay while decarboxylase demonstrates only weak absorption. Fourier analysis of the decay curves clearly shows that phosphorylase has an intense absorption decay in the midst of three weaker ones and that decarboxylase only has three weak decays. This conclusion justifies the isolation and use of the intense decay of phosphorylase as an observable in the study of protein dynamics at the active site about the cofactor. The decay has demonstrated a movement of positive charge to substrate in the mechanism of phosphorylation of glycogen units.
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Affiliation(s)
- J W Ledbetter
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston 29425
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48
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Sulfadoxine. ACTA ACUST UNITED AC 1988. [DOI: 10.1016/s0099-5428(08)60226-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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50
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