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Interaction of cisplatin with human serum albumin. Drug binding mode and protein secondary structure
1Department of Chemistry-Biology, University of Québec at Trois-Rivières, Canada.
Abstract:
Cis-diamminedichloroplatinum(II) (cisplatin) is an antitumor drug, which forms intrastrand cross-links DNA adducts. Protein interaction with cisplatin-DNA complexes induces DNA bending and biopolymer structural changes. This study is designed to examined the interaction of cisplatin with human serum albumin (HSA) in aqueous solution at physiological pH with drug concentrations of 0.0001 mM to 0.1 mM, and HSA (fatty acid free) concentration of 2% w/v. Absorption spectra and Fourier transform infrared (FTIR) spectroscopy with its self-deconvolution and second derivative resolution enhancement, as well as curve-fitting procedures, were used to determine the drug binding mode, drug binding constant and the protein secondary structure in aqueous solution. Spectroscopic evidence showed that at low drug concentration (0.0001 mM), minor cisplatin-protein interaction occurs, while at higher drug content (0.001 mM), major Pt-HSA complexation takes place via protein C=O, C-N and S-H donor groups with overall binding constant K = 8.52 x 10(2) M-1. At high drug concentration, cisplatin binding results in major protein secondary structural changes from that of the alpha-helix 55% (free HSA) to 45% and beta-sheet 22% (free HSA) to 32%, in the cisplatin-HSA complexes. The observed spectral changes indicate a partial unfolding of the protein structure, in the presence of cisplatin at high drug concentrations.
Insights
Cisplatin, an antitumor drug, interacts with human serum albumin (HSA), altering its structure. High concentrations of cisplatin cause significant changes in HSA secondary structure, indicating partial protein unfolding.
Area of Science:
- Biochemistry
- Chemical Biology
- Pharmacology
Background:
- Cisplatin is a crucial platinum-based chemotherapy agent.
- Cisplatin exerts its antitumor effects by forming DNA adducts.
- Protein interactions with cisplatin-DNA complexes can alter DNA structure.
Purpose of the Study:
- To investigate the interaction between cisplatin and human serum albumin (HSA).
- To determine the binding mode, constant, and effect on protein secondary structure.
Main Methods:
- Absorption spectroscopy.
- Fourier transform infrared (FTIR) spectroscopy with deconvolution and curve-fitting.
- Analysis of protein secondary structure changes.
Main Results:
- Cisplatin binds to HSA primarily through C=O, C-N, and S-H donor groups.
- The overall binding constant (K) for cisplatin-HSA complexation is 8.52 x 10^2 M^-1.
- High cisplatin concentrations induced significant changes in HSA secondary structure, decreasing alpha-helix content and increasing beta-sheet content, suggesting partial unfolding.
Conclusions:
- Cisplatin interacts with HSA, with binding affinity increasing at higher drug concentrations.
- Cisplatin binding leads to alterations in the secondary structure of HSA, indicating a partial unfolding of the protein.