Fluorescence lifetimes: fundamentals and interpretations

Abstract

Fluorescence measurements have been an established mainstay of photosynthesis experiments for many decades. Because in the photosynthesis literature the basics of excited states and their fates are not usually described, we have presented here an easily understandable text for biology students in the style of a chapter in a text book. In this review we give an educational overview of fundamental physical principles of fluorescence, with emphasis on the temporal response of emission. Escape from the excited state of a molecule is a dynamic event, and the fluorescence emission is in direct kinetic competition with several other pathways of de-excitation. It is essentially through a kinetic competition between all the pathways of de-excitation that we gain information about the fluorescent sample on the molecular scale. A simple probability allegory is presented that illustrates the basic ideas that are important for understanding and interpreting most fluorescence experiments. We also briefly point out challenges that confront the experimenter when interpreting time-resolved fluorescence responses.

Spectroscopic studies of protein folding: Linear and nonlinear methods

“…Modulation of the fluorescence intensity of a fluorophore of interest by another molecular moiety (or quencher) through various mechanisms73 has been widely used as a means to measure the proximity of the fluorophore to the quencher. For protein molecules, such modulations have been used to report on conformations and conformational changes as a function of various physical variables (e.g., time, temperature, or denaturant concentration).…”

Chlorophyll Fluorescence in Plant Biology

“…Molecules remain at a low energy level or the ground electronic singlet state (S o ) or the lowest vibrational level at room temperature (Noomnarm and Clegg, 2009). On absorption of a photon, the molecule is excited from S o to the first electronic excited singlet state S 1 within < 10-15 s -1 (Figure 1).…”

Princípios fundamentais e modelos de transferência de energia inter e intramolecular

“…15 Por exemplo, se um doador apresenta baixo tempo de vida de fluorescência e uma baixa taxa de transferência singleto excitado-tripleto então é mais provável que este doador apresente fluorescência ao invés de fosforescência ou de transferência de energia para um receptor. 16 O primeiro tratamento teórico, baseado na física clássica, para transferência de energia entre moléculas em solução foi desenvolvido por Perrin, que conjecturou que a energia é transferida de uma molécula para outra através da interação entre os dipolos de oscilação das moléculas envolvidas, e estimou que a transferência de energia poderia ocorrer a distâncias de até λ/2π, onde λ é o comprimento de onda do campo elétrico oscilante.…”