Isothermal titration calorimetry (ITC) is a biophysical technique for measuring the formation and dissociation of molecular complexes and has become an invaluable tool in many branches of science from cell biology to food chemistry. By measuring the heat absorbed or released during bond formation, ITC provides accurate, rapid, and label-free measurement of the thermodynamics of molecular interactions. In this review, we survey the recent literature reporting the use of ITC and have highlighted a number of interesting studies that provide a flavour of the diverse systems to which ITC can be applied. These include measurements of protein-protein and protein-membrane interactions required for macromolecular assembly, analysis of enzyme kinetics, experimental validation of molecular dynamics simulations, and even in manufacturing applications such as food science. Some highlights include studies of the biological complex formed by Staphylococcus aureus enterotoxin C3 and the murine T-cell receptor, the mechanism of membrane association of the Parkinson's disease-associated protein α-synuclein, and the role of non-specific tannin-protein interactions in the quality of different beverages. Recent developments in automation are overcoming limitations on throughput imposed by previous manual procedures and promise to greatly extend usefulness of ITC in the future. We also attempt to impart some practical advice for getting the most out of ITC data for those researchers less familiar with the method.

Applications of isothermal titration calorimetry in pure and applied research--survey of the literature from 2010.

The affinity of metal ions for DNA is logical considering that the structure of DNA includes a phosphate backbone with a net-negative charge, a deoxyribose sugar with O atoms, and purine and pyrimidine bases that contain O and N atoms. DNA-metal ion interactions encompass a large area of research that ranges from the most fundamental characterization of DNA-metal ion binding to the role of DNA-bound metal ions in disease and human health. Alternative DNA base pairing mediated by metal binding is also being investigated and manipulated for applications in logic gates, molecular machines, and nanotechnology. This review highlights recent work aimed at understanding interactions of redox-active metal ions with DNA that provides a better understanding of the mechanisms by which various types of oxidative DNA damage (strand breakage and base modifications) occur. Antioxidants that mitigate oxidative DNA damage by coordinating metal ions that produce reactive oxygen species are addressed, as well as recent work on the effect of DNA-metal ion interactions and the efficacy of quinolone-based antibacterial drugs. Recent advances in metal-mediated base pairing that triggers conformational changes in DNA structure for use as selective metal ion sensors and novel nanotechnology applications are also included.

DNA-bound metal ions: recent developments.

Comparative studies on DNA-binding and in vitro antitumor activity of enantiomeric ruthenium(II) complexes.

Ligupurpuroside A is a glycoside extracted from Ku-Ding tea. As extracts from Ku-Ding tea exhibit anti-inflammatory property, we hypothesize that Ligupurpuroside A may be an active compound which inhibits trypsin activity during the anti-inflammatory process. The mechanism and nature of inhibition of trypsin by Ligupurpuroside A have been studied by multi-spectroscopic method, enzyme-activity assay and molecular docking. Enzyme activity assay reveals that Ligupurpuroside A significantly inhibits the activity of trypsin through a competitive manner with an IC50 value of 3.08 × 10−3 mol L−1. Fluorescence titration together with thermodynamic analysis indicate that a Ligupurpuroside A-trypsin complex is formed, and that hydrophobic force and hydrogen bonding are the main forces stabilizing the complex. UV-vis absorption, synchronous fluorescence and circular dichroism spectra show that the interaction between Ligupurpuroside A and trypsin induces conformational changes of trypsin with a decrease in the contents of α-helix and β-sheet. Finally, molecular docking further suggests that Ligupurpuroside A molecule binds within the active pocket of trypsin via hydrophobic force and hydrogen bond. Results from this study of the interaction of trypsin with its natural inhibitor should be useful to minimize the antinutritional effects and make full use of tea extracts in the food industry, and be also helpful to the design of the drugs for the diseases related to overexpression of trypsin.

Mechanism and Nature of Inhibition of Trypsin by Ligupurpuroside A, a Ku-Ding Tea Extract, Studied by Spectroscopic and Docking Methods

New ruthenium complexes containing enantiopure 2,6-bis[4′(R)-phenyloxazolin-2′-il-pyridine] ((R,R)-Ph-pybox), 2,6-bis[4′(S)-isopropyloxazolin-2′-il-pyridine] ((S,S)-iPr-pybox) or 2,6-bis[4′(R)-isopropyloxazolin-2′-il-pyridine] ((R,R)-iPr-pybox) and water soluble 1,3,5-triaza-7-phosphaadamantane (PTA) or N-substituted PTA phosphanes have been synthesized in high yields and fully characterized. The interactions of these compounds with plasmidic DNA and their cytotoxic activity against the human cervical cancer HeLa cell line are reported, pointing out for the first time the different behaviour of ruthenium enantiomers affecting the cell cycle in HeLa tumor cells.

Xiao-Juan Chen

Papers

Studies on thermodynamic nature of steroselectivity for ruthenium(II) polypyridyl complex binding to DNA