Stereo-Selectivity of Human Serum Albumin to Enantiomeric and Isoelectronic Pollutants Dissected by Spectroscopy, Calorimetry and Bioinformatics

Abstract

1–naphthol (1N), 2–naphthol (2N) and 8–quinolinol (8H) are general water pollutants. 1N and 2N are the configurational enantiomers and 8H is isoelectronic to 1N and 2N. These pollutants when ingested are transported in the blood by proteins like human serum albumin (HSA). Binding of these pollutants to HSA has been explored to elucidate the specific selectivity of molecular recognition by this multiligand binding protein. The association constants (Kb) of these pollutants to HSA were moderate (104–105 M−1). The proximity of the ligands to HSA is also revealed by their average binding distance, r, which is estimated to be in the range of 4.39–5.37 nm. The binding free energy (ΔG) in each case remains effectively the same for each site because of enthalpy–entropy compensation (EEC). The difference observed between ΔCp exp and ΔCp calc are suggested to be caused by binding–induced flexibility changes in the HSA. Efforts are also made to elaborate the differences observed in binding isotherms obtained through multiple approaches of calorimetry, spectroscopy and bioinformatics. We suggest that difference in dissociation constants of pollutants by calorimetry, spectroscopic and computational approaches could correspond to occurrence of different set of populations of pollutants having different molecular characteristics in ground state and excited state. Furthermore, our observation of enhanced binding of pollutants (2N and 8H) in the presence of hemin signifies that ligands like hemin may enhance the storage period of these pollutants in blood that may even facilitate the ill effects of these pollutants.

Antimicrobial activity of various ethanolic plant extracts against pathogenic multi drug resistant Candida spp.

“…Although the phytochemical analysis of these compound has been done but further studies are required to pin point the active compounds. Other workers have also observed higher zones of inhibition with ethanolic extract of Azadirachta and trigonella, which supports our observations [37,38]. Our findings are in agreement of other workers [39,40].…”

Probing the Interaction of a Therapeutic Flavonoid, Pinostrobin with Human Serum Albumin: Multiple Spectroscopic and Molecular Modeling Investigations

“…The reliability of R 0 and r values calculation was evident from the satisfying criteria of 0.5 R 0 < r <2 R 0 [16]. Furthermore, the value of r was within the range, 2–8 nm indicating high probability of energy transfer between PS and HSA [31]. Additionally, the larger value of r compared to R 0 also supported the static quenching mechanism observed for PS–HSA interaction [32].…”

Calorimetric and spectroscopic binding studies of amoxicillin with human serum albumin

“…However, among them contribution of tryptophan is maximum [28,29]. The intrinsic fluorescence of HSA excited at 295 nm is mainly contributed by the Trp residue alone, because the Phe residue has a very low quantum yield and the fluorescence of Tyr is almost totally quenched when it is ionized or nearby to an amino group, a carboxyl group or a Trp [30].…”