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Updated: Feb 15, 2026

Production and Targeting of Monovalent Quantum Dots
Published on: October 23, 2014
Study on the Interaction of Functionalized Doped Graphene Quantum Dots by S-Allylcysteine and Serum Albumin Using
Parizad Mohammadnejad1,2, Fatemeh Aslani1, Beheshteh Sohrabi1
1Department of Chemistry, Surface Chemistry Research Laboratory, Iran University of Science and Technology, 16846-13114 Tehran, Iran.
Abstract:
This study investigates the interaction mechanisms between human serum albumin (HSA) and two structurally distinct ligands S-allyl-cysteine (SAC) and S, N-co-doped graphene quantum dots functionalized by S-allyl-cysteine (DGQD/SAC) using multispectroscopic and computational approaches. Steady-state and time-resolved fluorescence measurements revealed distinct quenching mechanisms: SAC exhibited static quenching through ground-state complex formation (KSV = 2 × 10-4 ppm1 at 298 K) with preserved HSA conformation (Δα-helix < 10%), while DGQD/SAC showed dynamic-dominated quenching (KSV = 0.2648 ppm-1 at 298 K and Kq = 26.48 × 106 ppm-1s-1) accompanied by partial protein unfolding (15% α-helix reduction). Förster resonance energy transfer (FRET) analysis confirmed donor-acceptor distances of 2.85 nm for HSA-DGQD/SAC, within optimal range for energy transfer (0.5R0< r < 1.5R0). Circular dichroism (CD) spectra demonstrated SAC's localized binding at Sudlow's site I, whereas N, S-GQD/SAC induced tertiary structure perturbations. Thermodynamic profiling revealed entropy-driven binding for both ligands (ΔS > 0), with SAC showing temperature-enhanced affinity (Ka increased from 1.2474 to 1.9902 ppm-1, 298-318 K). These findings provide critical insights for designing HSA-based delivery systems, highlighting SAC's structural preservation advantages and DGQD/SAC's tunable interfacial interactions.
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