Miguel Vázquez López’s research while affiliated with University of Santiago de Compostela and other places

Supramolecular helical polymers and helicates are two well-known and structurally different families of materials that share the same chiral axial motif, the helix. In this work, we describe how it is possible to design a molecule capable of folding in water into either of these two supramolecular entities. To do that we prepared a C3 symmetric benzene-1,3,5-triyltrimethanamine (BTMA) core conjugated to three peptide sequences, i.e. H-Arg-βAla-Bpy-βAla-Bpy-NH2 (BTMA-1). This molecule comprises all the structural requirements to self-assembly in water either into a chiral supramolecular helical polymer or into a chiral discrete helicate in the absence/presence of CoII ions in the aqueous media. We demonstrated that the discrete CoII peptide helicate folded can recognize DNA three-way junctions with high affinity and selectivity against canonical DNA and, moreover, that this recognition process can be operated from both the preformed discrete chiral peptide helicate and the chiral supramolecular helical polymer. Finally, we also proved that the labile CoII peptide helicate can be oxidized in situ in water to generate the corresponding kinetically inert CoIII derivative, which also possess selective 3WJ recognition capabilities. This study opens a new scenario in the biological applications of chiral supramolecular helical polymers, demonstrating that can be maintained inactively dispersed in water with time and further transformed into discrete bioactive molecules by an external stimulus.

We have synthesized two bipyridyl-based oligocationic cyclopeptides through solid phase peptide synthetic methods (SPPS) and studied their metal-binding, redox and biological properties in the presence of copper(II) ions in water media by several techniques. Remarkably, the studies performed indicate that, while the free cyclopeptides exhibit quite low or at most discrete cytotoxic properties, their Cu(II) derivatives show very high cytotoxic effects (an order of activity higher than cisplatin!) against different cancer cells lines, and, importantly, that the reason for this activity is that they can efficiently generate ROS within the cellular environment

By deprotonating Btp-derived ligands, precise control over counterions in the outer-coordination sphere is achieved in both neutral and charged anisotropic Co II complexes exhibiting field-induced single-ion magnetism.

The use of copper-based artificial nucleases as potential anticancer agents has been hampered by their poor selectivity in the oxidative DNA cleavage process. An alternative strategy to solve this problem is to design systems capable of selectively damaging noncanonical DNA structures that play crucial roles in the cell cycle. We designed an oligocationic CuII peptide helicate that selectively binds and cleaves DNA three-way junctions (3WJs) and induces oxidative DNA damage via a ROS-mediated pathway both in vitro and in cellulo, specifically at DNA replication foci of the cell nucleus, where this DNA structure is transiently generated. To our knowledge, this is the first example of a targeted chemical nuclease that can discriminate with high selectivity 3WJs from other forms of DNA both in vitro and in mammalian cells. Since the DNA replication process is deregulated in cancer cells, this approach may pave the way for the development of a new class of anticancer agents based on copper-based artificial nucleases.

The development of compounds that can selectively bind with non-canonical DNA structures has expanded in recent years. Junction DNA, including three-way junctions (3WJs) and four-way Holliday junctions (HJs), offer an intriguing target for developmental therapeutics as both 3WJs and HJs are involved in DNA replication and repair processes. However, there are a limited number of assays available for the analysis of junction DNA binding. Here, we describe the design and execution of multiplex fluorescent polyacrylamide gel electrophoresis (PAGE) and microscale thermophoresis (MST) assays that enable evaluation of junction-binding compounds. Two well characterised junction-binding compounds-a C6 linked bis-acridine ligand and an iron(II)-bound peptide helicate, which recognise HJs and 3WJs, respectively-were employed as probes for both MST and PAGE experiments. The multiplex PAGE assay expands beyond previously reported fluorescent PAGE as it combines four individual fluorophores that can be combined to visualise single-strands, pseudo-duplexes, and junction DNA present during 3WJ and HJ formation. The use of MST to identify the binding affinity of junction binding agents is, to our knowledge, first reported example of this technique. The combined use of PAGE and MST provides complementary results for the visualisation of 3WJ and HJ formation and the direct binding affinity (Kd and EC50) of these agents. These assays can be used to aid the discovery and design of new therapeutics targeting non-canonical nucleic acid structures.

G-Quadruplex DNA structures have attracted increasing attention due to their biological roles and potential as targets for the development of new drugs. While most guanine-rich sequences in the genome have the potential to form monomeric G-quadruplexes, certain sequences have enough guanine-tracks to give rise to multimeric quadruplexes. One of these sequences is the human telomere where tandem repeats of TTAGGG can lead to the formation of two or more adjacent G-quadruplexes. Herein we report on the modular synthesis via click chemistry of dimeric metal-salphen complexes (with NiII and PtII) bridged by either polyether or peptide linkers. We show by circular dichroism (CD) spectroscopy that they generally have higher selectivity for dimeric vs monomeric G-quadruplexes. The emissive properties of the PtII-salphen dimeric complexes have been used to study their interactions with monomeric and dimeric G-quadruplexes in vitro as well as to study their cellular uptake and localization.

We describe a new approach to target non-canonical DNA 3-Way Junctions (3WJs) that relies on the cooperative and sequence-selective recognition of A/T-rich duplex DNA branches by three AT-Hook peptides attached to a three-fold symmetric and fluorogenic 1,3,5-tristyrylbenzene core.

Self-assembled proteins are privileged building blocks for the bottom-up organization of matter at the nanoscale. However, since most proteins are very large, they have to be produced by recombinant expression, which is less versatile and flexible than chemical synthesis. Here, we show that we can bridge the potential of proteins for nanofabrication with the simplicity and versatility of solid-phase peptide synthesis by relying on the self-assembly of the viral protein gp23.1, a small 50-residue protein that oligomerizes in solution to form a stable toroidal hexamer. We report the chemical synthesis and basic biophysical characterization of a gp23.1 mutant and show that its self-assembled hexamer templates the formation of highly monodisperse luminescent gold nanoclusters of about 1.3 nm inside its central cavity. This work demonstrates the versatility of this small self-assembled ring protein for a variety of nanotechnological applications.