Ruiyong Wang

Crystal structure of NLRC4 reveals its autoinhibition mechanism.

Keeping the Inflammasome in Check Nucleotide-binding and oligomerization domain (NOD)–like receptors (NLRs) play an important role in the detection of pathogens by cells of the innate immune system. For several NLR family members, activation results in relief from autoinhibition, oligomerization, and the recruitment of signaling components that together make up the inflammasome, a large multiprotein complex. The inflammasome protects the host by inducing cell death and cytokine secretion. The specific molecular mechanisms that regulate NLR activation and inhibition, however, are not well understood. Hu et al. (p. 172, published online 13 June) report the crystal structure of autoinhibited NLR family member NLRC4, which reveals the domains that are critical for interaction with adenosine diphosphate to keep NLRC4 in its inactive state and the domains that mediate oligomerization of the protein upon activation. Adenosine diphosphate binding to the NOD-like receptor keeps it inactive in the absence of ligands. Nucleotide-binding and oligomerization domain–like receptor (NLR) proteins oligomerize into multiprotein complexes termed inflammasomes when activated. Their autoinhibition mechanism remains poorly defined. Here, we report the crystal structure of mouse NLRC4 in a closed form. The adenosine diphosphate–mediated interaction between the central nucleotide-binding domain (NBD) and the winged-helix domain (WHD) was critical for stabilizing the closed conformation of NLRC4. The helical domain HD2 repressively contacted a conserved and functionally important α-helix of the NBD. The C-terminal leucine-rich repeat (LRR) domain is positioned to sterically occlude one side of the NBD domain and consequently sequester NLRC4 in a monomeric state. Disruption of ADP-mediated NBD-WHD or NBD-HD2/NBD-LRR interactions resulted in constitutive activation of NLRC4. Together, our data reveal the NBD-organized cooperative autoinhibition mechanism of NLRC4 and provide insight into its activation.

Spectroscopic study on the interaction of Trypsin with Bicyclol and analogs

The interactions between Trypsin and Bicyclol or analogs (Bifendate, I, II and III) were investigated by spectrophotometric methods. It was found that Bicyclol or analogs had strong ability to quench the intrinsic fluorescence of Trypsin by a static quenching procedure. The binding constants were obtained at three temperatures. The thermodynamics parameters reveal that the hydrophobic and electrostatic interactions play an important role in the interaction. Results showed that the microenvironments of tryptophan residue of Trypsin were disturbed by the analogs. Results indicated that Bifendate was the strongest quencher among five compounds.

Investigation of the interaction between five alkaloids and human hemoglobin by fluorescence spectroscopy and molecular modeling.

This work studied the interaction of human hemoglobin (HHb) with aminophylline, acefylline, caffeine, theophylline and diprophylline systematically by UV-vis absorption spectroscopy and fluorescence spectroscopy in combination with molecular modeling. Five alkaloids caused the fluorescence quenching of HHb by the formation of alkaloids-HHb complex. The binding constants and thermodynamic parameters were obtained. The hydrophobic and electrostatic interactions were the predominant intermolecular forces to stabilize these complexes. Results of thermodynamic analysis and molecular modeling showed that aminophylline was the strongest quencher and diprophylline was the weakest quencher.

Investigation of the Binding Between Pepsin and Nucleoside Analogs by Spectroscopy and Molecular Simulation

In this paper, the interactions of pepsin with CYD (cytidine) or nucleoside analogs, including FNC (2′-deoxy-2′-β-fluoro-4′-azidocytidine) and CMP (cytidine monophosphate), were investigated by fluorescence, UV–visible absorption and synchronous fluorescence spectroscopy under mimic physiological conditions. The results indicated that FNC (CYD/CMP) caused the fluorescence quenching by the formation of complex. The binding constants and thermo-dynamic parameters at three different temperatures were obtained. The hydrophobic and electrostatic interactions were the predominant intermolecular forces to stabilize the complex. The F atom in FNC might weaken the binding of nucleoside analog to pepsin. Results showed that CYD was the strongest quencher and bound to pepsin with higher affinity.

Influence of the methyl position on the binding of 5-epi-taiwaniaquinone G to HSA investigated by spectrofluorimetry and molecular modeling

The interactions between human serum albumin (HSA) and 5-epi-taiwaniaquinone G (G2) or its isomeride (G1) was investigated by fluorescence, UV–visible absorption, resonance light scattering, synchronous fluorescence spectroscopy and 3D spectroscopy under mimic physiological conditions in combination with molecular modeling. The results revealed that G1 and G2 caused the fluorescence quenching of HSA by the formation of G1-HSA and G2-HSA complex, respectively. The binding constants and thermodynamic parameters at three different temperatures were obtained. Hydrophobic and electrostatic interactions played a role in the binding process of HSA and G1. Van der Waals force and hydrogen bond interaction played a role in the binding process of HSA and G2. Results showed that G2 was the stronger quencher and the position of methyl influenced the binding process between HSA and G1 (G2).

Study of the Binding between Camptothecin Analogs and FTO by Spectroscopy and Molecular Docking

In this work, the interaction between camptothecin (CPT) analogs and fat mass and obesity associated (FTO) was investigated using spectroscopy and molecular docking. From the experimental results, it was found that the CPT analogs caused the fluorescence quenching of FTO through a static quenching procedure. The binding constants and thermodynamic parameters at three different temperatures, the number of binding sites were obtained, which suggested that the hydrophobic interaction and electrostatic force played major role in the reaction between CPT analogs and FTO. Results revealed that 10-hydroxycamptothecin was the strongest quencher.

Characterization of the interaction of FTO protein with thioglycolic acid capped CdTe quantum dots and its analytical application

CdTe quantum dots (QDs) were synthesized in aqueous solution using thioglycolic acid (TGA) as stabilizing agents. The interaction between TGA-CdTe QDs and fat mass and obesity-associated (FTO) protein was investigated by fluorescence, UV-visible absorption, synchronous fluorescence and three-dimensional fluorescence spectroscopy. Results revealed that TGA-CdTe QDs could strongly quench the intrinsic fluorescence of FTO protein with a static quenching procedure. Both the van der Waals and hydrogen bonding played a major role in stabilizing the complex. The binding constant and thermodynamic parameters at different temperatures were obtained. In addition, we found that the fluorescence intensity of QDs was significantly enhanced by the addition of FTO protein. Based on this, a sensitive method for detecting FTO protein was obtained in the linear range of 5.52×10(-9)-6.62×10(-7) mol L(-1) with the detection limit of 1.14×10(-9) mol L(-1). The influences of factors on the interaction between FTO protein and TGA-CdTe QDs were studied.

Influence of the Ring Size on the Binding Ability of FTO Investigated by Fluorescence Spectroscopy

The fat mass and obesity associated protein (FTO) is a potential target for anti-obesity medicines. In this paper, we have synthesized two potential inhibitors for FTO, three-member-ring compound (W3) and four-member-ring compound (W4). The interactions of fat mass and obesity-associated (FTO) protein with W3 (or W4) have been studied by spectral method. Results show the intrinsic fluorescence is quenched by the W3 (or W4). The thermodynamics parameters indicate hydrophobic interaction play a major role in the interactions. The results of synchronous fluorescence spectra demonstrate that the microenvironments of Trp residue of FTO are disturbed by W3 and W4. Results showed that W3 are stronger quenchers and bind to FTO with the higher affinity than W4. The influence of molecular structure on the binding aspects has been investigated.

Spectrofluorometric Determination of Iron II Based on the Fluorescence Quenching of Cadmium/Tellurium Quantum Dots

ABSTRACT Water-soluble and stable CdTe quantum dots were synthesized in aqueous solution with thioglycolic acid as the stabilizer. A spectrofluorometric method for the determination of iron (II) has been developed based on quenching of the fluorescence of CdTe quantum dots by iron (II) in aqueous solutions. It can perform an accurate and simple determination of iron (II) concentration in water samples. Under optimum conditions, the quenched fluorescence intensity increased linearly with the concentration of iron (II) ranging from 5.0 × 10−8 to 4.0 × 10−6 mol/L with a correlation coefficient R = 0.9969. The limit of detection for iron (II) was found to be 1.2 × 10−8 mol/L. As an application, the proposed method was successfully applied to the analysis of iron (II) in water samples, and the results were satisfactory.

Investigation of the interaction between FTO and 3-substituted 2-aminochromones by spectroscopy and molecular modeling

The fat mass and obesity-associated protein is a potential target for anti-obesity medicines. In the present work, the interaction between our synthesized 3-substituted 2-aminochromones and fat mass and obesity-associated protein were investigated using fluorescence spectroscopy, ultraviolet–visible spectroscopy and molecular modeling approach. Fluorescence spectroscopy showed that the fluorescence of fat mass and obesity-associated protein can be quenched by these compounds with a static quenching procedure. In addition, the thermodynamic parameters obtained from the fluorescence data showed that the hydrophobic force played a major role in stabilizing the complexes. Ultraviolet–visible spectroscopy, synchronous fluorescence spectroscopy and three-dimensional fluorescence spectroscopy indicated that these compounds can induce some conformational changes of fat mass and obesity-associated protein.