Platinum(II)-Based Optical Probes for Imaging Quadruplex DNA Structures via Phosphorescence Lifetime Imaging Microscopy

G-quadruplex DNA is a non-canonical structure that forms in guanine-rich regions of the genome. There is increasing evidence showing that G-quadruplexes have important biological functions, and therefore molecular tools to visualise these structures are important. Herein we report on a series of new cyclometallated platinum(II) complexes which, upon binding to G-quadruplex DNA, display an increase in their phosphorescence, acting as switch-on probes. More importantly, upon binding to G-quadruplexes they display a selective and distinct lengthening of their emission lifetime. We show that this effect can be used to selectively visualise these structures in cells using Phosphorescence Lifetime Imaging Microscopy (PLIM).     

Syntheses,Characterization, and DNA Binding Studies of a Series of Copper(II), Nickel(II), Platinum(II) and Zinc(II) Complexes Derived from Schiff Base Ligands

Three series of metal salophen complexes derived from Zn²⁺, Cu²⁺, Pt²⁺ and Ni²⁺ have been synthesized and their interaction with quadruplex DNA has been evaluated. The compounds differ on the number of ethyl piperidine substituents. They have been characterized by ¹H NMR, IR and UV-visible spectroscopies and by HR-mass spectrometry. Their luminescent properties have been also evaluated and we can observe that, as expected, Zn²⁺ and Pt²⁺ complexes are those displaying more interesting luminescence with an emission band red-shifted with respect to the corresponding uncoordinated ligand. DNA interactions with G4 and duplex DNA were evaluated by FRET melting assays (for the Zn²⁺, Cu²⁺ and Ni²⁺ complexes) and by emission titrations (for one Pt²⁺ complex) which indicated that the disubstituted compounds 2-Ni and 2-Pt are the only ones that display good affinity for G4 DNA structures.     

Quantum statistical mechanics of closed‐ring molecular chains

A model for a closed‐ring unhindered three‐dimensional macromolecular chain, based on Quantum Mechanics, is presented. Upon starting from an exact non‐relativistic Hamiltonian operator, we integrate out all electronic degrees of freedom, in the Born‐Oppenheimer framework, giving rise to an effective vibro‐rotational Hamiltonian for the chain. Then, assuming a harmonic oscillator‐like vibrational potential between nearest‐neighbour atoms, the integration of the atomic radial degrees of freedom is carried in the limit of high frequencies. Thus, all bond lengths become fixed, including the one which makes the chain to become a closed ring. This formulation leads to a specific Hamiltonian for the remaining angular variables of the closed‐ring chain, and constitutes an alternative in comparison with standard Gaussian models, which do not. Use is made of a variational inequality by Peierls to find an approximate quantum partition function for the angular variables of the system. We then proceed to obtain approximately another representation for the angular partition function in the classical limit. Several features of the classical partition function are discussed.     

Computational Excavation Analysis of a Single Cutting Tool using a Hypoplastic Constitutive Model

We propose a computational model for the numerical analysis of the dynamic interaction between a single excavation tool and the surrounding soil. An incremental non-linear (hypoplastic) constitutive model is employed to capture the complex response of soft soils. Large displacements and deformations are handled by an Updated Lagrangian formulation, the particle finite element method (PFEM). (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)