The extent of quenching depends on the nature of the quencher molecule (fluorophore or non-fluorophore), the type of interaction, and the wavelength of energy that is emitted by the fluor. Fluorescence Quenching and Fluorescence Resonance Energy Transfer. As said in the section on the Stokes shift, fluorescence is a very sensitive method for studying the local environment around the fluorophore. In this review, the experimental set-up and functional characteristics of single-wavelength and broad-band femtosecond upconversion spectrophotofluorometers developed in our laboratory are described. Quenching of 2 -aminopurine fluorescence in DNA is dominated by distance-dependent electron transfer from 2 -aminopurine to guanosine [2]. 4 Dynamic quenching is described by the Stern-Volmer mechanism and results by collisions of the excited state molecule with the quencher. In addition to the processes described above, apparent quenching can occur due to the optical properties of the sample. Seidel et al. It may occur due to various factors like pH, temperature, viscosity, complex formation. When this complex absorbs light, it immediately returns to the fundamental state without emitting any photons. Fluorescence quenching can also take place by the formation at the ground state of a non-fluorescent complex. We discuss applications of this technique to biophysical problems, such as ultrafast fluorescence quenching and solvation dynamics of tryptophan, peptides, proteins, reduced … This type of complex is called static quenching and it can be described with the following equations: Since thioamide analogs of the natural amino acids can be synthetically incorporated into peptides, they can function as minimally-perturbing probes of protein/peptide interactions. Methods of fluorescent quenching include fluorescence resonance energy transfer (FRET), collision quenching and contact quenching, which are diagrammed below. Rational design of novel photoinduced electron transfer type fluorescent probes for sodium cation. This may occur due to various factors like pH, concentration, temperature, viscosity, presence of oxygen, heavy metals or, specific chemical substances etc. TYPES OF QUENCHING Concentration quenching: At low concentration linearity is observed. The order of quenching efficiency is G