title: Origin of tryptophan fluorescence lifetimes part 1. Fluorescence lifetimes origin of tryptophan free in solution.
abstract: Fluorescence intensity decays of L-tryptophan free in polar, hydrophobic and mixture of polar-hydrophobic solvents were recorded along the emission spectrum (310-410 nm). Analysis of the data show that emission of tryptophan occurs with two lifetimes in 100% polar and hydrophobic environments. The values of the two lifetimes are not the same in both environments while their populations (pre-exponentials values) are identical. Fluorescence lifetimes and pre-exponentials values do not change with the excitation wavelength and thus are independent of excitation energy. Our results indicate that tryptophan emission occurs from two specific sub-structures existing in the excited state. These sub-structures differ from those present in the ground states and characterize an internal property and/or organization of the tryptophan structure in the excited state. By sub-substructure, we mean here tryptophan backbone and its electronic cloud. In ethanol, three fluorescence lifetimes were measured; two lifetimes are very close to those observed in water (0.4-0.5 ns and 2-4 ns). Presence of a third lifetime for tryptophan in ethanol results from the interaction of both hydrophobic and hydrophilic dipoles or chemical functions of ethanol with the fluorophore.
authors.affiliation: Laboratoire de Biophysique Moléculaire, Université de Lille 1. Sciences et Technologies, Bâtiment C6, 59655, Villeneuve d'Ascq Cédex, France, Jihad-Rene.Albani@univ-lille1.fr.
authors.forename: J R
authors.initials: JR
authors.lastname: Albani
mesh_terms: D005453:Fluorescence; D057927:Hydrophobic and Hydrophilic Interactions; D012996:Solutions; D013997:Time Factors; D014364:Tryptophan / Q000737:chemistry*
chemical_list: D012996:Solutions; D014364:Tryptophan
references.citation: Methods Enzymol. 1972;26:498-578
references.pmid: 4680723
references.citation: J Protein Chem. 1996 Oct;15(7):607-19
references.pmid: 8968952
references.citation: J Phys Chem B. 2007 Mar 15;111(10):2610-20
references.pmid: 17300189
references.citation: Biochim Biophys Acta. 1976 Apr 14;427(2):663-78
references.pmid: 5134
references.citation: Biophys J. 1997 Apr;72(4):1800-11
references.pmid: 9083684
references.citation: J Fluoresc. 2008 Jan;18(1):75-85
references.pmid: 17899333
references.citation: Biochemistry. 1991 May 28;30(21):5184-95
references.pmid: 2036384
references.citation: Methods Enzymol. 1979;61:378-425
references.pmid: 481233
references.citation: J Fluoresc. 2010 Sep;20(5):973-83
references.pmid: 20352304
references.citation: J Am Chem Soc. 2006 Apr 19;128(15):5142-52
references.pmid: 16608350
references.citation: J Fluoresc. 2009 Nov;19(6):1061-71
references.pmid: 19533308
references.citation: Photochem Photobiol. 2003 Jul;78(1):15-22
references.pmid: 12929743
references.citation: Photochem Photobiol Sci. 2004 Apr;3(4):348-59
references.pmid: 15052363
references.citation: J Fluoresc. 2009 May;19(3):399-408
references.pmid: 18855127
references.citation: J Pharm Biomed Anal. 2009 Sep 8;50(2):107-16
references.pmid: 19473803
references.citation: Biophys J. 1994 Nov;67(5):2013-23
references.pmid: 7858139
references.citation: J Fluoresc. 2007 Jul;17(4):406-17
references.pmid: 17458686