Abstract Hydrogen bonding is a complex phenomenon that is a resultant of many energy components like the electrostatic, dispersive, covalent, charge cloud overlap repulsion etc, nature of hydrogen bon Show more
Abstract Hydrogen bonding is a complex phenomenon that is a resultant of many energy components like the electrostatic, dispersive, covalent, charge cloud overlap repulsion etc, nature of hydrogen bond (H-bond) depends on which of these components play a dominant role. Low barrier hydrogen bond (LBHB) constitutes a special category of hydrogen bonds characterized by near delocalization of proton between donor and acceptor groups of the H- bond unlike an ordinary hydrogen bond (OHB) having proton clearly localized near the donor group. The significance of LBHBs in macromolecular interactions has been highly controversial, despite may attempts the existence and potential importance of protein LBHBs remains debatable. In order to answer questions like whether or not a distinct class of LBHBs exists and if they do exist under what conditions they are formed and how do they behave differently from OHBs, a detailed study of H-bonding in Diglycine Perchlorate (DGPCl) crystal containing five unique hydrogen bonded glycinium-glycine pairs is undertaken. All O-H–O bonds of DGPCl are between the carboxyl (-COOH) and carboxylate (-COO−) groups with slightly different electron distributions resulting in observable variations in the H-bond geometries, this is an indication of varying strength of these short strong H-bonds. It is found that LBHB nature of the five O-H—O bonds between glycinium-glycine pairs (P1-P5) varies as P1 < P4 < P2 < P3 < P5. This study gives an experimental evidence of the existence of LBHBs and demonstrates that the behaviour of LBHBs is very different from that of strong OHBs. Show less
Platinum-based anticancer drugs represented by cisplatin play important roles in the treatment of various solid tumors. However, their applications are largely compromised by drug resistance and side Show more
Platinum-based anticancer drugs represented by cisplatin play important roles in the treatment of various solid tumors. However, their applications are largely compromised by drug resistance and side effects. Much effort has been made to circumvent the drug resistance and general toxicity of these drugs. Among multifarious designs, monofunctional platinum(II) complexes with a general formula of [Pt(3A)Cl] + (A: Ammonia or amine) stand out as a class of “non-traditional” anticancer agents hopeful to overcome the defects of current platinum drugs. This review aims to summarize the development of monofunctional platinum(II) complexes in recent years. They are classified into four categories: fluorescent complexes, photoactive complexes, targeted complexes, and miscellaneous complexes. The intention behind the designs is either to visualize the cellular distribution, or to reduce the side effects, or to improve the tumor selectivity, or inhibit the cancer cells through non-DNA targets. The information provided by this review may inspire researchers to conceive more innovative complexes with potent efficacy to shake off the drawbacks of platinum anticancer drugs. Show less