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Photophysics in Motionally constrained Bioenvironment: Interactions of Norharmane with Bovine Serum Albumin ¶
Author(s) -
Mallick Arabinda,
Chattopadhyay Nitin
Publication year - 2005
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.2005.tb00202.x
Subject(s) - bovine serum albumin , chemistry , aqueous solution , cationic polymerization , fluorescence , denaturation (fissile materials) , biophysics , photochemistry , chromatography , organic chemistry , nuclear chemistry , physics , quantum mechanics , biology
Steady‐state photophysics of norharmane (NHM), a bioactive alkaloid, has been studied in the presence of a model transport protein, bovine serum albumin (BSA). The emission spectrum undergoes a remarkable change upon addition of BSA to the aqueous solution of NHM in buffer. Addition of BSA leads to a marked increase in the fluorescence anisotropy of the neutral species of NHM, although the fluorescence anisotropy for the cationic species is almost invariant to BSA addition, suggesting that the neutral species is located in a motionally restricted environment of BSA, whereas the cationic species remains in the bulk aqueous phase. The binding constant (K) and free energy change (ΔG) for the probe‐protein binding have been calculated from the fluorescence data. Light has been thrown on the action of urea on protein‐bound NHM. The denaturation study suggests that the protein, in its native form, binds with NHM. Polarity of the microenvironment around the probe has been determined from a comparison of the fluorescence properties of the two prototropic species of NHM in water‐dioxane mixture with varying composition.