[Show abstract][Hide abstract] ABSTRACT: Counterions are required for RNA folding, and divalent metal ions such as Mg(2+) are often critical. To dissect the role of counterions, we have compared global and local folding of wild-type and mutant variants of P4-P6 RNA derived from the Tetrahymena group I ribozyme in monovalent and in divalent metal ions. A remarkably simple picture of the folding thermodynamics emerges. The equilibrium folding pathway in monovalent ions displays two phases. In the first phase, RNA molecules that are initially in an extended conformation enforced by charge-charge repulsion are relaxed by electrostatic screening to a state with increased flexibility but without formation of long-range tertiary contacts. At higher concentrations of monovalent ions, a state that is nearly identical to the native folded state in the presence of Mg(2+) is formed, with tertiary contacts that involve base and backbone interactions but without the subset of interactions that involve specific divalent metal ion-binding sites. The folding model derived from these and previous results provides a robust framework for understanding the equilibrium and kinetic folding of RNA.
[Show abstract][Hide abstract] ABSTRACT: The emergence of a relatively new technique resulting from a combination of frontal affinity chromatography coupled with MS detection (FAC-MS) has extended the capabilities of MS in drug discovery and development. Its application in a broad range of biological systems, together with its label-free operation, relatively high throughput, ability to rank ligands and determine Kd, makes FAC-MS a universal tool enabling convenient and efficient screening in the identification of new potential drug leads. Here we will highlight FAC-MS screening studies and discuss where it can be applied in evaluating multiple protein-binding sites, protein-protein interactions and inactive proteins, and also in determining selectivity.
Drug Discovery Today 04/2005; 10(6):409-16. DOI:10.1016/S1359-6446(04)03360-4 · 6.69 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A new method that utilizes matrix-assisted laser desorption/ionization (MALDI) mass spectrometry and exploits the hydrogen/deuterium (H/D) exchange properties of proteins was developed for measuring the thermodynamic properties of protein-ligand complexes in solution. Dissociation constants (Kd values) determined by the method for five model protein-ligand complexes that included those with small molecules, nucleic acids, peptides, and other proteins were generally in good agreement with Kd values measured by conventional methods. Important experimental advantages of the described method over existing methods include: the ability to make measurements in a high-throughput and automated fashion, the ability to make measurements using only picomole quantitities of protein, and the ability to analyze either purified or unpurified protein-ligand complexes.
Journal of the American Chemical Society 10/2002; 124(35):10256-7. DOI:10.1021/ja0251266 · 12.11 Impact Factor
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