Quenching of Chlorophyll Fluorescence by Nitrobenzene

Abstract

Abstract—Nitrobenzene quenching of chlorophyll fluorescence in ethanol has been investigated. Steady state relative quantum yields have been measured and fluorescence decay rates were determined using both nanosecond photon counting and picosecond pulses from a mode‐locked Nd3+ glass laser. The fluorescence decay is described by 1(t)=I0 exp (‐t/τ−At1/2) the form predicted for decay governed by the kinetics of the continuum model of diffusion controlled reactions. From the parameters of the fluorescence decay, the encounter distance is 5–7 A° the mutual diffusion coefficient is 0.62 × 10‐‐5 cm2s‐1± 12%. Some of the fluorescence quenching is also attributed to static quenching by a nitrobenzene‐chlorophyll, ground‐state complex. The equilibrium constant for formation of this ground‐state complex was determined to be 4.1 M‐1. The combined dynamic and static quenching model allows calculation of quantum yields of fluorescence in good agreement with the experimentally determined quantum yields.

Picosecond spectroscopy: applications in biochemistry. Part II: applications

“…This relation is frequently found to give closer agreement with experimental decays than the exponential law in very fast kinetic studies and is predicted theoretically for the early stages of time-dependent diffusion processes and for Forster-type energy transfer to a random array (Beddard et at., 1978). Its significance in photosynthetic antennae must await more precise kinetic measurements as well as better information on the structure of these systems.…”

Development of Protein‐Labeling Probes with a Redesigned Fluorogenic Switch Based on Intramolecular Association for No‐Wash Live‐Cell Imaging

“…A more important feature is that nitrobenzene associates with fluorophores, including fluorescein, and thereby quenches the fluorescence 9. 14 Furthermore, this quenching mechanism can be utilized as a general strategy for the design of turn‐on fluorescence probes. It is envisioned that the fluorescein of the probe loses its fluorescence by the association with nitrobenzene, and this association inhibits the unwanted interaction between the ligand and fluorophore moieties, thereby leading to rapid protein labeling (Scheme ).…”

CHARGE TRANSFER COMPLEXES OF PHEOPHYTIN a WITH NITROAROMATICS. ELECTRON TRANSFER FROM EXCITED SINGLET OF PHEOPHYTIN a TO NITROAROMATICS

“…It is found that all nitroaromatics employed in the present study function as efficient quenchers. Moreover, it may be noticed that acceptors which exhibit larger K values quench the fluorescence strongly (larger K,, values) (Beddard et al, 1978). The possible kinetic scheme for the quenching mechanism can be written as…”

“…It has been known for some time that Chl forms CT complexes with quinones and nitroaromatics where the pigment essentially functions as a donor and quinones and nitroaromatics as acceptors (Connolly. 1981;Beddard et al, 1978;Seely, 1978). The fluorescence quenching studies of Chl by these a c c e p t o r s is d o c u m e n t e d ( N a t a r a j a n a n d Blankenship.…”