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Updated: Dec 14, 2025
An In Vitro Single-Molecule Imaging Assay for the Analysis of Cap-Dependent Translation Kinetics
Published on: September 15, 2020
Transplatin ineffectiveness against cancer from a molecular perspective: A single-molecule force-spectroscopy study
L Oliveira1, J M Caquito1, M S Rocha1
1Departamento de Física, Universidade Federal de Viçosa. Viçosa, Minas Gerais, Brazil.
Abstract:
By performing single-molecule force spectroscopy with optical tweezers, we have characterized the interaction between the platinum-based compound transplatin and the DNA molecule, establishing a critical comparison with its isomer cisplatin. While transplatin is ineffective against tumor cells, its isomer is one of the most used drugs in current chemotherapies, and a molecular study on this difference performed at the single-molecule level was lacking until the present work. Our experiments show that transplatin binds DNA under low chloride concentrations (a situation usually found inside many cells) with an equilibrium association binding constant about four orders of magnitude lower than cisplatin. In addition, we have found that, at saturation, transplatin binds preferentially forming interstrand cross links and monoadducts, a situation very different from cisplatin, which forms preferentially intrastrand cross links. Such differences explain the ineffectiveness of transplatin in killing tumor cells. From a physical point of view, the present study advances in using the mechanical properties of the DNA molecule as sensors to evaluate the therapeutic efficiency of drugs.
Insights
Transplatin, unlike its chemotherapy drug isomer cisplatin, poorly binds DNA due to weaker interactions. This study reveals transplatin forms different DNA adducts, explaining its ineffectiveness against tumor cells.
Area of Science:
- Biophysics
- Molecular Biology
- Chemical Biology
Background:
- Cisplatin is a widely used chemotherapy drug, while its isomer transplatin is ineffective against cancer.
- A single-molecule level understanding of the interaction differences between these platinum compounds and DNA was previously lacking.
Purpose of the Study:
- To characterize the DNA interaction of transplatin at the single-molecule level using optical tweezers.
- To critically compare the DNA binding of transplatin with that of cisplatin.
Main Methods:
- Single-molecule force spectroscopy utilizing optical tweezers.
- Characterization of DNA-platinum compound interactions under varying chloride concentrations.
Main Results:
- Transplatin exhibits an equilibrium association binding constant four orders of magnitude lower than cisplatin under low chloride conditions.
- At saturation, transplatin preferentially forms interstrand cross-links and monoadducts, contrasting with cisplatin's preferential intrastrand cross-links.
Conclusions:
- The distinct DNA binding modes and weaker affinity of transplatin explain its ineffectiveness as a chemotherapeutic agent.
- The study demonstrates the utility of DNA's mechanical properties as sensors for evaluating drug efficacy.
