Carboxylato-Pillar[6]arene-Based Fluorescent Indicator Displacement Assays for Caffeine Sensing

In the present work, we have developed a new indicator displacement system based on pillararene for anionic water-soluble carboxylato pillar [6] arene (WP6) and aromatic fluorescent dye safranine T (ST). A large fluorescence enhancement and colour change of ST were observed after complexation with electron-rich cavity in WP6 because of host-guest twisted intramolecular charge-transfer interactions. The constructed pillararene-indicator displacement system can be applied for caffeine selective detection in water.

Binding methylarginines and methyllysines as free amino acids: a comparative study of multiple supramolecular host classes

Methylated free amino acids are an important class of targets for host-guest chemistry that have recognition properties distinct from those of methylated peptides and proteins. We present comparative binding studies for three different host classes that are each studied with multiple methylated arginines and lysines to determine fundamental structure-function relationships. The hosts studied are all anionic and include three calixarenes, two acyclic cucurbiturils, and two cleft-like hosts. We determined the binding association constants for a panel of methylated amino acids using indicator displacement assays. The calixarene hosts show weak binding that favours the higher methylation states, with the strongest binding observed for trimethyllysine. The acyclic cucurbiturils display stronger binding to the methylated amino acids, and some unique patterns of selectivity. The cleft-like hosts follow two different trends, one shallow host following similar trends to the calixarenes, and the other more closed host binding certain less-methylated amino acids stronger than their per-methylated counterparts. Molecular modeling sheds some light on the different preferences of different hosts. The results identify hosts with selectivities that will be useful for certain biomedical applications. The overall selectivity patterns are explained by a common framework that considers the topology, depth of binding pockets, and functional group participation across all host classes.

Enzyvitands: versatile evolvable colorimetric chembioreceptors

Designing the perfect sensor is the dream of any chemist. Since decades, a wide diversity of synthetic receptors targeting analytes has been explored in chemistry. Their chemical optimization is hard and with no guarantee of success. In this context, we propose a fast and self assembling colorimetric bio-chemical receptor coined Enzyvitand. It consists only of commercial chemicals. It relies on the reunification of combinatorial chemistry , first and second coordination spheres interactions and indicators displacement assays. All harbored within a protein cavity. The sensor is highly modular, cheap and evolvable. Thanks to its solved X-ray structure, we rationally designed it for the selectiv naked-eye recognition of dopamine over other neutrotransmitters through second coordination sphere. Hence, our sensor imitates a biological receptor for the recognition of neurotransmitters. Finally, it works in complex samples such as urine. Its immediate high versatility and evolvability is valuable for the selective detection of a wide assortment of analytes from small molecules up to micro-organisms. For the future, we anticipate new biotechnological or immunotherapeutic applications of our synthetic oligomer.

Ditopic Aza-Scorpiand Ligands Interact Selectively with ds-RNA and Modulate the Interaction Upon Formation of Zn2+ Complexes

Nucleic acids are essential biomolecules in living systems and represent one of the main targets of chemists, biophysics, biologists, and nanotechnologists. New small molecules are continuously developed to target the duplex (ds) structure of DNA and, most recently, RNA to be used as therapeutics and/or biological tools. Stimuli-triggered systems can promote and hamper the interaction to biomolecules through external stimuli such as light and metal coordination. In this work, we report on the interaction with ds-DNA and ds-RNA of two aza-macrocycles able to coordinate Zn2+ metal ions and form binuclear complexes. The interaction of the aza-macrocycles and the Zn2+ metal complexes with duplex DNA and RNA was studied using UV thermal and fluorescence indicator displacement assays in combination with theoretical studies. Both ligands show a high affinity for ds-DNA/RNA and selectivity for ds-RNA. The ability to interact with these duplexes is blocked upon Zn2+ coordination, which was confirmed by the low variation in the melting temperature and poor displacement of the fluorescent dye from the ds-DNA/RNA. Cell viability assays show a decrease in the cytotoxicity of the metal complexes in comparison with the free ligands, which can be associated with the observed binding to the nucleic acids.

Enzyvitands: evolvable biosynthetic and colorimetric chalices

<div><div><div><p>Designing the perfect sensor is the dream of any chemist. Since decades, a wide diversity of chemosensors targeting analytes has been explored in chemistry. Their chemical optimization is hard and with no guarantee of success. In this context, we propose a fast and easy-to-assemble colorimetric bio-chemical receptor coined Enzyvitand. It consists only of commercial chemicals. It relies on the reunification of combinatorial chemistry, first and second coordination spheres interactions and indicators displacement assays. All harbored within a protein cavity. The sensor is highly modular, cheap and evolvable. Thanks to its solved X-ray structure, we rationally designed it for the naked-eye recognition of dopamine. Hence, our sensor imitates a biological receptor for the recognition of neurotransmitters. Its immediate high versatility and evolvability is valuable for the selective detection of a wide assortment of analytes from small molecules up to micro-organisms. For the future, we anticipate new biotechnological or immunotherapeutic applications of our bio-sensor.</p></div></div></div>

Oral probiotic activities and biosafety of Lactobacillus gasseri HHuMIN D

Background Lactobacillus spp. have been researched worldwide and are used in probiotics, but due to difficulties with laboratory cultivation of and experimentation on oral microorganisms, there are few reports of Lactobacillus spp. being isolated from the oral cavity and tested against oral pathogens. This research sought to isolate and determine the safety and inhibitory capabilities of a Lactobacillus culture taken from the human body. Results One organism was isolated, named “L. gasseri HHuMIN D”, and evaluated for safety. A 5% dilution of L. gasseri HHuMIN D culture supernatant exhibited 88.8% inhibition against halitosis-producing anaerobic microorganisms and the organism itself exhibited powerful inhibitory effects on the growth of 11 oral bacteria. Hydrogen peroxide production reached 802 μmol/L after 12 h and gradually diminished until 24 h, it efficiently aggregated with P. catoniae and S. sanguinis, and it completely suppressed S. mutans-manufactured artificial dental plaque. L. gasseri HHuMIN D’s KB cell adhesion capacity was 4.41 cells per cell, and the cell adhesion of F. nucleatum and S. mutans diminished strongly in protection and displacement assays. Conclusion These results suggest that L. gasseri HHuMIN D is a safe, bioactive, lactobacterial food ingredient, starter culture, and/or probiotic microorganism for human oral health.

Revisiting the interaction of heme with hemopexin

In hemolytic disorders, erythrocyte lysis results in massive release of hemoglobin and, subsequently, toxic heme. Hemopexin is the major protective factor against heme toxicity in human blood and currently considered for therapeutic use. It has been widely accepted that hemopexin binds heme with extraordinarily high affinity of <1 pM in a 1:1 ratio. However, several lines of evidence point to a higher stoichiometry and lower affinity than determined 50 years ago. Here, we re-analyzed these data. SPR and UV/Vis spectroscopy were used to monitor the interaction of heme with the human protein. The heme-binding sites of hemopexin were characterized using hemopexin-derived peptide models and competitive displacement assays. We obtained a K D value of 0.32 ± 0.04 nM and the ratio for the interaction was determined to be 1:1 at low heme concentrations and at least 2:1 (heme:hemopexin) at high concentrations. We were able to identify two yet unknown potential heme-binding sites on hemopexin. Furthermore, molecular modelling with a newly created homology model of human hemopexin suggested a possible recruiting mechanism by which heme could consecutively bind several histidine residues on its way into the binding pocket. Our findings have direct implications for the potential administration of hemopexin in hemolytic disorders.

Indicator displacement assays (IDAs): the past, present and future

Indicator displacement assays (IDAs) offer a unique and innovative approach to molecular sensing. This Tutorial review discusses the basic concepts of each IDA strategy and illustrates their use in sensing applications.

Binding site exchange kinetics revealed through efficient spin–spin dephasing of hyperpolarized 129Xe

Localized detection of hyperpolarized, exchanging Xe spins enables quantitative insights at unprecedented sensitivity for characterizing chemical exchange kinetics in various contexts such as host–guest interactions and displacement assays.