Structural insights into the interactions of <i>xpt</i> riboswitch with novel guanine analogues: a molecular dynamics simulation study

<div><p>Ligand recognition in purine riboswitches is a complex process requiring different levels of conformational changes. Recent efforts in the area of purine riboswitch research have focused on ligand analogue binding studies. In the case of the guanine xanthine phosphoribosyl transferase (<i>xpt</i>) riboswitch, synthetic analogues that resemble guanine have the potential to tightly bind and subsequently influence the genetic expression of <i>xpt</i> mRNA in prokaryotes. We have carried out 25 ns Molecular Dynamics (MD) simulation studies of the aptamer domain of the <i>xpt</i> G-riboswitch in four different states: guanine riboswitch in free form, riboswitch bound with its cognate ligand guanine, and with two guanine analogues SJ1 and SJ2. Our work reveals novel interactions of SJ1 and SJ2 ligands with the binding core residues of the riboswitch. The ligands proposed in this work bind to the riboswitch with greater overall stability and lower root mean square deviations and fluctuations compared to guanine ligand. Reporter gene assay data demonstrate that the ligand analogues, upon binding to the RNA, lower the genetic expression of the guanine riboswitch. Our work has important implications for future ligand design and binding studies in the exciting field of riboswitches.</p></div

Acetylcholinesterase and Aβ Aggregation Inhibition by Heterometallic Ruthenium(II)–Platinum(II) Polypyridyl Complexes

Two heteronuclear ruthenium­(II)–platinum­(II) complexes [Ru­(bpy)₂(BPIMBp)­PtCl₂]²⁺ (<b>3</b>) and [Ru­(phen)₂(BPIMBp)­PtCl₂]²⁺ (<b>4</b>), where bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline, and BPIMBp = 1,4′-bis­[(2-pyridin-2-yl)-1H-imidazol-1-ylmethyl]-1,1′-biphenyl, have been designed and synthesized from their mononuclear precursors [Ru­(bpy)₂(BPIMBp)]²⁺ (<b>1)</b> and [Ru­(phen)₂(BPIMBp)]²⁺ (<b>2</b>) as multitarget molecules for Alzheimer’s disease (AD). The inclusion of the cis-PtCl₂ moiety facilitates the covalent interaction of Ru­(II) polypyridyl complexes with amyloid β (Aβ) peptide. These multifunctional complexes act as inhibitors of acetylcholinesterase (AChE), Aβ aggregation, and Cu-induced oxidative stress and protect neuronal cells against Aβ-toxicity. The study highlights the design of metal based anti-Alzheimer’s disease (AD) systems