Real-Time Analysis of Polyphenol-Protein Interactions by Surface Plasmon Resonance Using Surface-Bound Polyphenols

Systemic Convergent Multitarget Interactions of Plant Polyphenols Revealed by Affinity-Based Protein Profiling of Bone Cells Using C-Glucosidic Vescal(ag)in-Bearing Chemoproteomic Probes

The ellagitannins vescalagin and vescalin, known as actin-dependent inhibitors of osteoclastic bone resorption, were mounted onto chemical probes to explore their interactions with bone cell proteins by means of affinity-based chemoproteomics and bioinformatics. The chemical reactivity of the pyrogallol units of these polyphenols toward oxidation into electrophilic ortho-quinones was exploited using NaIO4 to promote the covalent capture of target proteins, notably those expressed at lower abundance and those interacting with polyphenols at low-to-moderate levels of affinity. Different assays revealed the multitarget nature of both ellagitannins, with 100-370 statistically significant proteins captured by their corresponding probes. A much higher number of proteins were captured from osteoclasts than from osteoblasts. Bioinformatic analyses unveiled a preference for the capture of proteins having phosphorylated ligands and GTPase regulators and enabled the identification of 33 potential target proteins with systemic relevance to osteoclast differentiation and activity, as well as to the regulation of actin dynamics.

The controllable patterning of tannic acid on DNA origami

Tannic acid-based patterning is crucial for its applications in bioengineering, including multifunctional coatings, biosensors, and biochips. However, tannic acid (TA) patterning is challenging owing to the rapid polymerization kinetics of tannins and their strong adhesion towards most surfaces or objects. Herein, we report a strategy for controllable TA nanopatterning based on DNA origami templates. Protruding clustered ssDNA (pcDNA) from DNA origami tiles served as indexes for the selective deposition of TA due to the high flexibility of ssDNA and exposed aromatic bases, which provide active sites for TA-DNA interactions. Next, by exploiting the pH-sensitive degradation of TA polymers, controllable 'erasing' and 'rewriting' of TA nanopatterns were performed. Finally, combining the high adhesion and selective deposition, the TA polymers as a glue modified on the edges of origami tiles directed the reversible association/disassociation of origami multimers. Our strategy provides a simple approach for the controllable nanopatterning of TA, enabling its unique properties to tailor surface patterns for applications in materials science and biomedicine.

Synthesis of Flavonol-Bearing Probes for Chemoproteomic and Bioinformatic Analyses of Asteraceae Petals in Search of Novel Flavonoid Enzymes

This study aimed at searching for the enzymes that are responsible for the higher hydroxylation of flavonols serving as UV-honey guides for pollinating insects on the petals of Asteraceae flowers. To achieve this aim, an affinity-based chemical proteomic approach was developed by relying on the use of quercetin-bearing biotinylated probes, which were thus designed and synthesized to selectively and covalently capture relevant flavonoid enzymes. Proteomic and bioinformatic analyses of proteins captured from petal microsomes of two Asteraceae species (Rudbeckia hirta and Tagetes erecta) revealed the presence of two flavonol 6-hydroxylases and several additional not fully characterized proteins as candidates for the identification of novel flavonol 8-hydroxylases, as well as relevant flavonol methyl- and glycosyltransferases. Generally speaking, this substrate-based proteome profiling methodology constitutes a powerful tool for the search for unknown (flavonoid) enzymes in plant protein extracts.

Electrochemical detection of kinase by converting homogeneous analysis into heterogeneous assay through avidin-biotin interaction

In the classical heterogeneous electrochemical assay, phosphorylation of peptide substrate is usually performed on the solid-liquid surface. However, immobilization of probe on the solid surface may limit the interaction between the reaction site of probe and the active center of kinase due to the steric hindrance effect. In this work, we proposed a heterogeneous electrochemical method for kinase detection, in which the probe is immobilization-free during the phosphorylation reaction. A biotinylated peptide was used as the kinase substrate. After phosphorylation, the biotinylated phosphopeptide was captured by the neutravidin (NA)-modified electrode through the avidin-biotin interaction. The phosphate groups on the electrode surface were then recognized by the conjugates preformed between biotinylated Phos-tag™ (Bio-tag-Phos) and ferrocene (Fc)-capped NA-modified gold nanoparticle (Fc-AuNP-NA). The method integrates the advantages of homogeneous reaction and heterogeneous detection with high simplicity, sensitivity and specificity. The strategy can be applied to design other heterogeneous biosensors without the immobilization of probe during the enzyme catalyzed reaction.