Binding Interaction of a Biological Photosensitizer with Serum Albumins:  A Biophysical Study

Abstract

A photophysical study on the binding interaction of an efficient cancer cell photosensitizer, norharmane (NHM), with model transport proteins, bovine serum albumin (BSA) and human serum albumin (HSA), has been performed using a combination of steady-state and time-resolved fluorescence techniques. The emission profile undergoes a remarkable change upon addition of the proteins to the buffered aqueous solution of the photosensitizer. The polarity-dependent prototropic transformation is responsible for the remarkable sensitivity of this biological fluorophore to the protein environments. A marked increase in the fluorescence anisotropy in the proteinous environments indicates that the albumin proteins introduce motional restriction on the drug molecule. Light has been thrown on the denaturing action of urea on the probe-bound protein. The probable binding site of the drug in proteins has also been assessed from the combination of denaturation study, micropolarity measurement, and fluorescence resonance energy transfer (FRET) study. The present study suggests that the stability of serum albumins is enhanced upon binding with the drug.

Chemically Induced Unfolding of Bovine Serum Albumin by Urea and Sodium Dodecyl Sulfate: A Spectral Study with the Polarity‐Sensitive Charge‐Transfer Fluorescent Probe (E)‐3‐(4‐Methylaminophenyl)acrylic Acid Methyl Ester

“…Similar blue shifts have been reported previously for other systems. [2][3][4][5] This pronounced blue shift is due to movement of the probe from the polar protic aqueous environment to a more hydrophobic, less polar protein interior when it binds to BSA. The increase in intensity of the CT band with increasing protein concentration accompanying the blue shift of the CT band is also indicative of increasing hydrophobicity of the microenvironment near the loScheme 1.…”

“…Such intramolecular charge-transfer (ICT) molecules with similar polarity-sensitive red-shifted CT emission bands have been used as good fluorescent probes for probing the interactions between probes and proteins and also the unfolding processes of the latter. [2][3][4][5] In this study, steady-state spectroscopy was used to investigate the binding interaction of BSA with MAPAME. The changes in the position of the ICT emission band of MAPAME as it binds to BSA or when the bound BSA is denatured on addition of urea, as well as the accompanying anisotropy changes and the red-edge excitation shifts that occur under these conditions, were studied.…”

The effects of photodynamic treatment with new methylene blue N on the Candida albicans proteome

“…Also, others have shown that histidine residues buried deep inside the protein structure are not photooxidazible (KENKARE and RICHARDS 1966). Different photosensitizer binding affinities have been shown for human and bovine serum albumins (CHAKRABARTY et al 2007). Given that these proteins share around 80% homology, it is evident that different proteins could greatly diverge in their ability to bind the photosensitizer.…”

Photoactive assemblies of organic compounds and biomolecules: drug–protein supramolecular systems

“…105 properties to HSA and BSA have recently been addressed. 106,107 In neutral aqueous solution, NOR and HAR present two absorption maxima corresponding to the neutral (~348 nm) and protonated (~370 nm) species. 108 The …”