Spectroscopic investigation of water‐soluble alloyed QDs with bovine serum albumin

Abstract

We present here a systematic investigation on the interaction between a water-soluble alloyed semiconductor quantum dot and bovine serum albumin using various spectroscopic techniques i.e. fluorescence quenching, resonance light scattering and synchronous fluorescence spectroscopy. The analysis of fluorescence spectrum and fluorescence intensity indicates that the intrinsic fluorescence of bovine serum albumin (BSA) gets quenched by both static and dynamic quenching mechanism. The Stern-Volmer quenching constants, energy transfer efficiency parameters, binding parameters and corresponding thermodynamic parameters (ΔH , ΔS and ΔG ) have been evaluated by using van 't Hoff equation at different temperatures. A positive entropy change with a positive enthalpy change was observed suggesting that the binding process was an entropy-driven, endothermic process associated with the hydrophobic effect. The intermolecular distance (r) between donor (BSA) and acceptor (CdSeS/ZnS quantum dots) was estimated according to Förster's theory of non-radiative energy transfer. The synchronous fluorescence spectra revealed a blue shift in the emission maxima of tryptophan which is indicative of increasing hydrophobicity. Negative ΔG values implied that the binding process was spontaneous. It was found that hydrophobic forces played a role in the quenching process. Copyright © 2016 John Wiley & Sons, Ltd.

Comprehensive study of interaction between biocompatible PEG‐InP/ZnS QDs and bovine serum albumin

“…Further, we have used the following simplified Equation () to calculate the Förster distance ( R 0 ) in angstrom between Trp and QDs where n is the refractive index of the medium, κ 2 is orientation factor (2/3 for randomly oriented dipoles) and Q D is the quantum yield of the donor BSA protein (i.e. 0.118). Förster distance is the separation between the surfaces of donor and the acceptor which corresponds to separation between donor and acceptor when the energy transfer efficiency ( E T ) is equal to 50%.…”

Interaction and energy transfer studies between bovine serum albumin and CdTe quantum dots conjugates: CdTe QDs as energy acceptor probes

“…Δ H o and Δ S o presented in Table were calculated by using the slope and intercept values from Figure . According to the enthalpy and entropy changes, the model of interaction between QD and biomolecules can be summarized as follows: in general (i) if Δ H o > 0 and Δ S o > 0, association processes are triggered by hydrophobic interactions between proteins and ligands; (ii) if Δ H o < 0 and Δ S o < 0 the processes are triggered by hydrogen bonding and van der Waal's forces; and (iii) Δ H o < 0 and Δ S o > 0 indicate electrostatic interaction …”

“…Thus it was concluded that hydrophobic forces play a major role in the binding interaction between BSA and QDs. Hydrophobic interactions are important for the folding of proteins because this keeps a protein alive and biologically active during the interaction …”

“…ΔH o and ΔS o presented in Table 1 were calculated by using the slope and intercept values from interaction. [3,39,40] Gibbs free energy (ΔG o ) was estimated from the following equa-…”

“…Hydrophobic interactions are important for the folding of proteins because this keeps a protein alive and biologically active during the interaction. [3,40] 3.3 | Fluorescence resonance energy transfer (FRET)…”