Membrane-Associated Nucleobase-Functionalized β-Peptides (β-PNAs) Affecting Membrane Support and Lipid Composition

Scrutinizing the interaction between metribuzin with glutathione reductase 2 from Arabidopsis thaliana: insight into the molecular toxicity in agriculture

As one of the triazine herbicides with widespread usage in agriculture, metribuzin exerted nonnegligible hazardous effects on plants via excessive accumulation of reactive oxygen species and destruction of antioxidant enzymes, but the underlying harmful mechanism of metribuzin-induced oxidative damage to plants has never been exploited. Here, Arabidopsis thaliana glutathione reductase 2 (AtGR2) was employed as the biomarker to evaluate the adverse impacts of metribuzin on plants. The fluorescence intensity of AtGR2 was decreased based on the static quenching mechanism with the prediction of a single binding site toward metribuzin, and the complex formation was presumed to be mainly impelled by hydrogen bonding and van der Waals forces from the negative ΔH and ΔS. In addition, the loosened and unfolded skeleton of AtGR2 along with the increased hydrophilicity around the tryptophan residues were investigated. Besides, the glutathione reductase activity of AtGR2 was also destroyed due to structural and conformational changes. At last, the severe inhibiting growth of Arabidopsis seedling roots was discovered under metribuzin exposure. Hence, the evaluation of the molecular interaction mechanism of AtGR2 with metribuzin will establish valuable assessments of the toxic effects of metribuzin on plants.

Willardiine and Its Synthetic Analogues: Biological Aspects and Implications in Peptide Chemistry of This Nucleobase Amino Acid

Willardiine is a nonprotein amino acid containing uracil, and thus classified as nucleobase amino acid or nucleoamino acid, that together with isowillardiine forms the family of uracilylalanines isolated more than six decades ago in higher plants. Willardiine acts as a partial agonist of ionotropic glutamate receptors and more in particular it agonizes the non-N-methyl-D-aspartate (non-NMDA) receptors of L-glutamate: ie. the α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) and kainate receptors. Several analogues and derivatives of willardiine have been synthesised in the laboratory in the last decades and these compounds show different binding affinities for the non-NMDA receptors. More in detail, the willardiine analogues have been employed not only in the investigation of the structure of AMPA and kainate receptors, but also to evaluate the effects of receptor activation in the various brain regions. Remarkably, there are a number of neurological diseases determined by alterations in glutamate signaling, and thus, ligands for AMPA and kainate receptors deserve attention as potential neurodrugs. In fact, similar to willardiine its analogues often act as agonists of AMPA and kainate receptors. A particular importance should be recognized to willardiine and its thymine-based analogue AlaT also in the peptide chemistry field. In fact, besides the naturally-occurring short nucleopeptides isolated from plant sources, there are different examples in which this class of nucleoamino acids was investigated for nucleopeptide development. The applications are various ranging from the realization of nucleopeptide/DNA chimeras for diagnostic applications, and nucleoamino acid derivatization of proteins for facilitating protein-nucleic acid interaction, to nucleopeptide-nucleopeptide molecular recognition for nanotechnological applications. All the above aspects on both chemistry and biotechnological applications of willardine/willardine-analogues and nucleopeptide will be reviewed in this work.

From Prebiotic Chemistry to Supramolecular Biomedical Materials: Exploring the Properties of Self-Assembling Nucleobase-Containing Peptides

Peptides and their synthetic analogs are a class of molecules with enormous relevance as therapeutics for their ability to interact with biomacromolecules like nucleic acids and proteins, potentially interfering with biological pathways often involved in the onset and progression of pathologies of high social impact. Nucleobase-bearing peptides (nucleopeptides) and pseudopeptides (PNAs) offer further interesting possibilities related to their nucleobase-decorated nature for diagnostic and therapeutic applications, thanks to their reported ability to target complementary DNA and RNA strands. In addition, these chimeric compounds are endowed with intriguing self-assembling properties, which are at the heart of their investigation as self-replicating materials in prebiotic chemistry, as well as their application as constituents of innovative drug delivery systems and, more generally, as novel nanomaterials to be employed in biomedicine. Herein we describe the properties of nucleopeptides, PNAs and related supramolecular systems, and summarize some of the most relevant applications of these systems.

Assessments on the molecular toxic mechanisms of fipronil and neonicotinoids with glutathione transferase Phi8

As the most widely used pesticides, fipronils and neonicotinoids exhibit harmful effects to many species including crops mainly via the oxidative damages. However, the potential toxic mechanisms of these pesticides to plants remain unclear. In this work, glutathione S-transferase Phi8 was employed as the biomarker to assess the adverse oxidative effects of these two kinds of pesticides. The structural changes and binding characteristics of AtGSTF8 with the pesticides were investigated by multispectral techniques and the latest generation neonicotinoid dinotefuran exhibited the most evident effects on the structure of AtGSTF8. Then dinotefuran displayed weak binding ability to AtGSTF8 comparing with fipronil and clothianidin based on the bio-layer interferometry technique. Besides, the glutathione S-transferase activities of AtGSTF8 were decreased upon binding with these two kinds of pesticides but dinotefuran displayed minor effect on the enzyme activity. At last, dinotefuran and clothianidin were presumed to locate on the molecular surface of AtGSTF8, while fipronil was predicted to insert into the cavity of AtGSTF8 which was adjacent to the active G-site based on the molecular docking results. The molecular investigations on the toxic mechanisms would help to evaluate the harmful effects of these two kinds of prevalent pesticides to plants.

Membrane-Associated Nucleobase-Functionalized β-Peptides (β-PNAs) Affecting Membrane Support and Lipid Composition

Protein-membrane interactions are essential to maintain membrane integrity and control membrane morphology and composition. Cytoskeletal proteins in particular are known to interact to a high degree with lipid bilayers and to line the cytoplasmic side of the plasma membrane with an extensive network structure. In order to gain a better mechanistical understanding of the protein-membrane interplay and possible membrane signaling, we started to develop a model system based on β-peptide nucleic acids (β-PNAs). These β-peptides are known to form stable hydrogen-bonded aggregates due to their helical secondary structure, which serve to pre-organize the attached nucleobases. After optimization of the β-PNA solid-phase peptide synthesis and validation of helix formation, the ability of the novel β-PNAs to dimerize and interact with lipid bilayers was investigated by both fluorescence and circular dichroism spectroscopy. It was shown that duplex formation occurs rapidly and with high specificity and could also be detected on the surfaces of the lipid bilayers. Hereby, the potential of a β-PNA-based peptide system to mimic membrane-associated protein networks could be demonstrated.