Lights and shadows in the challenge of binding acyclovir, a synthetic purine-like nucleoside with antiviral activity, at an apical-distal coordination site in copper(II)-polyamine chelates

Remission of HPV-Related Diseases by Antivirals for Herpesvirus: Clinical Cases and a Literature Review

Epidemiological studies have shown that HPV-related diseases are the most prevalent sexually transmitted infections. In this context, this report will present various clinical cases demonstrating the effectiveness of Acyclovir (ACV) or its prodrug Valaciclovir (VCV), both acyclic guanosine analogs commonly used for the treatment of HHV-1 and HHV-2, for the treatment of HPV-related diseases. The report shows the remission of five cases of penile condyloma and a case of remission in a woman affected by cervical and vaginal condylomas and a vulvar giant condyloma acuminate of Buschke and Lowenstein. The literature review shows that ACV is effective in treating skin warts when administered orally, topically, and intralesionally, suggesting its therapeutic potential in other diseases associated with HPV. ACV was also used successfully as an adjuvant therapy for juvenile and adult forms of laryngeal papillomatosis, also known as recurrent respiratory papillomatosis, prolonging the patient's symptom-free periods. Although the prevention of HPV infections is certainly achieved with the HPV vaccine, ACV and VCV have shown to be effective even against genotypes not included in the current vaccine and can be helpful for those problematic clinical cases involving unvaccinated individuals, immunocompromised patients, people who live with HIV, or non-responders to the vaccine. We and others concluded that randomized clinical trials are necessary to determine the efficacy of ACV and VCV for HPV-related diseases.

Aqua(1,4,7,10-tetraazacyclododecane)zinc(II) bis(perchlorate)

The cationic Zn^II part of aqua­(1,4,7,10-tetra­aza­cyclo­dodeca­ne)zinc(II) diperchlorate, [Zn(C₈H₂₀N₄)H₂O](ClO₄)₂, exhibits a slightly distorted square-pyramidal coordination environment with a water mol­ecule in the apical position.

The cationic Zn^II part of aqua­(1,4,7,10-tetra­aza­cyclo­dodeca­ne)zinc(II) bis­(perchlorate), [Zn(C₈H₂₀N₄)(H₂O)](ClO₄)₂, exhibits a slightly distorted square-pyramidal coordination environment with a water mol­ecule in the apical position. In the crystal, the macrocyclic ring alternates between two conformations with equal occupancies. Two of the three perchlorate anions are situated about a twofold rotation axis, and one of them shows disorder of the O atoms with occupancies of 0.62 (7) and 0.38 (7). In the crystal, the complexes are connected by inter­molecular hydrogen bonding via the perchlorate anions.

Deciphering the H-Bonding Preference on Nucleoside Molecular Recognition through Model Copper(II) Compounds

The synthetic nucleoside acyclovir is considered an outstanding model of the natural nucleoside guanosine. With the purpose of deepening on the influence and nature of non-covalent interactions regarding molecular recognition patterns, three novel Cu(II) complexes, involving acyclovir (acv) and the ligand receptor N-(2-hydroxyethyl)ethylenediamine (hen), have been synthesized and thoroughly characterized. The three novel compounds introduce none, one or two acyclovir molecules, respectively. Molecular recognition has been evaluated using single crystal X-ray diffraction. Furthermore, theoretical calculations and other physical methods such as thermogravimetric analysis, infrared and UV-Vis spectroscopy, electron paramagnetic resonance and magnetic measurements have been used. Theoretical calculations are in line with experimental results, supporting the relevance of the [metal-N7(acv) + H-bond] molecular recognition pattern. It was also shown that (hen)O-H group is used as preferred H-donor when it is found within the basal coordination plane, since the higher polarity of the terminal (hen)O-H versus the N-H group favours its implication. Otherwise, when (hen)O-H occupies the distal coordination site, (hen)N-H groups can take over.

The role of coordination compounds in virus research. Different approaches and trends

This article aims to provide an overview of the studies focused on using coordination compounds as antiviral agents against different types of viruses. We present various strategies so far used to this end. This article is divided into two sections. The first collects the series of designed antiviral drugs based on coordination compounds. This approach has been developed for many years, starting from the 70s with the discovery of cis-platin (cis-DDP). It has been mainly focused on studying the synergistic effect of a wide variety of new compounds obtained by combining metal ions with organic antiviral ligands. Then, we collect various strategies analyzing the coordination compounds interacting with viruses using different processes such as wrapping viruses, rapid detection of RNA or DNA virus, or nanocarriers. These recent and novel insights help to study viruses from other points of view, allowing to measure their physical and chemical properties. We also highlight a section in which the issue of viruses from a disinfection viewpoint is addressed, using coordination compounds as a tool able to control the release of antiviral and biocide agents. This is an emerging and promising field but this approach is actually little developed. We finally provide a section with a general conclusion and perspectives.

Heterotrimetallic Cyanide-Bridged 3d-4d-5d Frameworks Based on a Photomagnetic Secondary Building Unit

The rational design of coordination frameworks combining more than two different metal ions using a self-assembly approach is challenging because it rarely offers sufficient control over the building blocks at the actual self-assembly stage. In this work, we present a successful two-step strategy toward heterotrimetallic coordination frameworks by employing a new bimetallic [(NC)₇Mo^IV-CN-Pt^IV(NH₃)₄-NC-Mo^IV(CN)₇]^4– secondary building unit (SBU). This anionic moiety has been isolated and characterized as a simple salt with an organic dppipH₂²⁺ cation (dppipH₂)₂[(NC)₇Mo^IV-CN-Pt^IV(NH₃)₄-NC-Mo^IV(CN)₇]·15H₂O (1) (dppip = 1,4-di(4-pyridinyl)piperazine). The salt presents a second-order phase transition related to cation conformational change around 250 K and a photomagnetic effect after irradiation with 450 nm light at 10 K. When combined with aqueous solutions of Mn^II or Cu^II complexes, it forms either a one-dimensional chain [Mn^II(dpop)][Mn^II(dpop)(H₂O)][(NC)₇Mo^IV-CN-Pt^IV(NH₃)₄-NC-Mo^IV(CN)₇]·36H₂O (2) (dpop = 2,13-dimethyl-3,6,9,12,18-pentaazabicyclo-[12.3.1]octadeca-1(18),2,12,14,16-pentaene) or a photomagnetic two-dimensional honeycomb network [Cu^II(cyclam)]₂[(NC)₇Mo^IV-CN-Pt^IV(NH₃)₄-NC-Mo^IV(CN)₇]·40.89H₂O (3) (cyclam = 1,4,8,11-tetraazacyclotetradecane), both characterized by very large cavities in their structure filled with solvent molecules. Both 2 and 3 incorporate three different transition-metal ions and constitute a new family of 3d-4d-5d coordination frameworks. Moreover, compound 3 inherits the photomagnetic properties of the MoPtMo SBU.

A photomagnetic secondary building unit (SBU) Mo^IVPt^IVMo^IV was employed to design and synthesize new heterotrimetallic coordination polymers in a two-step approach, resulting in Mn^II₂Mo^IV₂Pt^IV coordination chains and Cu^II₂Mo^IV₂Pt^IV honeycomb coordination layers.

Dual use of colorimetric sensor and selective copper removal from aqueous media with novel p(HEMA-co-TACYC) hydrogels: Cyclen derivative as both monomer and crosslinker

Within the scope of this study, p(2-hydroxyethyl methacrylate-co-tetraacrylic cyclen) (p(HEMA-co-TACYC)) hydrogels were synthesized for the first time in the literature using a tetraacrylic cyclen (TACYC) as both functional monomer and crosslinker. The hydrogels designed especially for Cu²⁺ ions showed colorimetric sensor behavior selective for Cu²⁺ ions in all aqueous media (deionized, tap, river and sea water) and in metal ion mixtures. The p(HEMA-co-TACYC) hydrogels forming a stable complex with Cu²⁺ ions simultaneously showed properties of being a good adsorbent material. The hydrogels have reuse capacity as both sensor and adsorbent material. Changing the amount of TACYC in the hydrogel structure changes the maximum adsorption capacity for Cu²⁺ ions. The Langmuir and Freundlich adsorption constants for Cu²⁺ ion adsorption of the hydrogels, acting as selective adsorbent in all aqueous media and metal ion mixtures, were determined.

Anion–Cation Recognition Pattern, Thermal Stability and DFT-Calculations in the Crystal Structure of H2dap[Cd(HEDTA)(H2O)] Salt (H2dap = H2(N3,N7)-2,6-Diaminopurinium Cation)

The proton transfer between equimolar amounts of [Cd(H2EDTA)(H2O)] and 2,6-diaminopurine (Hdap) yielded crystals of the out-of-sphere metal complex H2(N3,N7)dap[Cd(HEDTA)(H2O)]·H2O (1) that was studied by single-crystal X-ray diffraction, thermogravimetry, FT-IR spectroscopy, density functional theory (DFT) and quantum theory of “atoms-in-molecules” (QTAIM) methods. The crystal was mainly dominated by H-bonds, favored by the observed tautomer of the 2,6-diaminopurinium(1+) cation. Each chelate anion was H-bonded to three neighboring cations; two of them were also connected by a symmetry-related anti-parallel π,π-staking interaction. Our results are in clear contrast with that previously reported for H2(N1,N9)ade [Cu(HEDTA)(H2O)]·2H2O (EGOWIG in Cambridge Structural Database (CSD), Hade = adenine), in which H-bonds and π,π-stacking played relevant roles in the anion–cation interaction and the recognition between two pairs of ions, respectively. Factors contributing in such remarkable differences are discussed on the basis of the additional presence of the exocyclic 2-amino group in 2,6-diaminopurinium(1+) ion.

Cu(II)-Based Paramagnetic Probe to Study RNA-Protein Interactions by NMR

Paramagnetic NMR techniques allow for studying three-dimensional structures of RNA-protein complexes. In particular, paramagnetic relaxation enhancement (PRE) data can provide valuable information about long-range distances between different structural components. For PRE NMR experiments, oligonucleotides are typically spin-labeled using nitroxide reagents. The current work describes an alternative approach involving a Cu(II) cyclen-based probe that can be covalently attached to an RNA strand in the vicinity of the protein's binding site using "click" chemistry. The approach has been applied to study binding of HIV-1 nucleocapsid protein 7 (NCp7) to a model RNA pentanucleotide, 5'-ACGCU-3'. Coordination of the paramagnetic metal to glutamic acid residue of NCp7 reduced flexibility of the probe, thus simplifying interpretation of the PRE data. NMR experiments showed attenuation of signal intensities from protein residues localized in proximity to the paramagnetic probe as the result of RNA-protein interactions. The extent of the attenuation was related to the probe's proximity allowing us to construct the protein's contact surface map.

Crystal structure of (perchlorato-κO)(1,4,7,10-tetra-aza-cyclo-dodecane-κ4N)copper(II) perchlorate

The crystal structure of the title salt, [Cu(ClO4)(C8H20N4)]ClO4, is reported. The CuII ion exhibits a square-pyramidal geometry and is coordinated by the four N atoms of the neutral 1,4,7,10-tetra-aza-cyclo-dodecane (cyclen) ligand and an O atom from one perchlorate anion, with the second perchlorate ion hydrogen-bonded to one of the amine N atoms of the cyclen ligand. Additional N-H⋯O hydrogen bonds between the amine H atoms and the coordinating and non-coordinating perchlorate groups create a three-dimensional network structure. Crystals were grown from a concentrated methanol solution at ambient temperature, resulting in no co-crystallization of solvent.