Photophysics in Motionally Constrained Bioenvironment: Interaction of Norharmane with Bovine Serum Albumin¶

Abstract

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 (DeltaG) 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.

Fluorescence resonance energy transfer from tryptophan in human serum albumin to a bioactive indoloquinolizine system

“…are by now well established as bioactive molecules. [12][13][14][15][16] The single-step synthesis of 3-acetyl-4-oxo-6,7-dihydro-12H indolo-[2,3-a] quinolizine (AODIQ) from 1-methyl-3,4-dihydro-β-carboline leads to the assumption that the molecule should have biological activity. 17 Through a series of experiments we have already established that the fluorophore molecule serves as an excellent fluorescent probe for biological systems.…”

7-Hydroxy-4-methyl-8-(4′-methylpiperazine-1′-yl)methyl coumarin: An efficient probe for fluorescence resonance energy transfer to a bioactive indoloquinolizine system

“…One important consequence of energy transfer is photosensitization, a classic example of which is photosynthesis [24]. Moreover, FRET plays a key role in PDT of cancer [24,25] and is extensively used to study the structure, conformation, spatial distribution and assembly of complex proteins [26]. Since FRET causes a number of important biological phenomena [23], much interest lies in FRET studies between two potent bioactive molecules in vitro.…”

Photophysical studies of PET based acridinedione dyes with globular protein: Bovine serum albumin

“…Literature involving the interaction of probe or drug with BSA reveals the significance of the binding sites in BSA [18,26,32,[43][44][45][46][47]. BSA, which contains a large hydrophobic interior, is the most preferred site for the binding of fluorescent probes.…”

“…The importance of fluorescence technique on the probe-protein interaction has been elucidated from the studies on the interaction of eosin and erythrosine dyes [2,3,22], coumarin derivatives [4,23], 1-anilino-8-napthalenesulfonate (ANS) [24,25] norharmane [26], 3-hydroxy flavones [27], 11 (dansylamino) undecanoicacid (DAUDA) [28], 4-[2 0 -dimethylaminonaphthahoyl] cyclohexanecarboxylicacid (DANCA) [29], 9-(n-decanyl) acridone [30], 1-dimethyl-aminonapthalene-5-sulfonylchloride (dansyl-Cl) [28,31], 8-amino-2-[(2-amino-5methylphenoxy)methyl]-6-methoxyquinoline-N,N,N',N'-tetraaceticacid tetrapotassium salt (Quin-2) [23].…”