Exploration of surface plasmon resonance for yam tyrosinase characterization

Biosensor-based active ingredient recognition system for screening TNF-α inhibitors from lotus leaves

Erhuangquzhi granules (EQG) have been clinically proven to be effective in nonalcoholic steatohepatitis (NASH) treatment. However, the active components and molecular mechanisms remain unknown. This study aimed to screen active components targeting tumor necrosis factor α (TNF-α) in EQG for the treatment of NASH by a surface plasmon resonance (SPR) biosensor-based active ingredient recognition system (SPR-AIRS). The amine-coupling method was used to immobilize recombinant TNF-α protein on an SPR chip, the specificity of the TNF-α-immobilized chip was validated, and nine medicinal herbs in EQG were prescreened. Nuciferine (NF), lirinidine (ID), and O-nornuciferine (NNF) from lotus leaves were found and identified as TNF-α ligands by UPLC‒MS/MS, and the affinity constants of NF, ID, and NNF to TNF-α were determined by SPR experiments (Kd = 61.19, 31.02, and 20.71 µM, respectively). NF, ID, and NNF inhibited TNF-α-induced apoptosis in L929 cells, the levels of secreted IL-6 and IL-1β were reduced, and the phosphorylation of IKKβ and IκB was inhibited in lipopolysaccharide (LPS)-stimulated RAW264.7 cells. In conclusion, a class of new active small-molecule TNF-α inhibitors was discovered, which also provides a valuable reference for the material basis and mechanism of EQG action in NASH treatment.

Kinetic and thermodynamic study of c-Met interaction with single chain fragment variable (scFv) antibodies using phage based surface plasmon resonance

Mesenchymal epithelial transition factor (c-Met) has been recently regarded as an attractive target for the treatment of cancer. Our previous study showed that c-Met-specific single chain fragment variables (scFvs) can be considered as a promising therapy for cancer, however, their molecular interaction with c-Met protein have not been assessed. Accordingly, in the current study we aim to evaluate the kinetic and thermodynamic properties of c-Met interaction with these scFvs as anticancer agents by means of surface plasmon resonance (SPR) technique. Phage-scFvs were immobilized on the 11-mercaptoundecanoic acid gold chips after carboxylic groups activation by N-ethyl-N-(3-diethylaminopropyl) carbodiimide/N-hydroxysuccinimide and, then the c-Met binding to each scFvs (ES1, ES2, and ES3) at different concentrations (ranging from 20 to 665 μM) was explored. Kinetic studies revealed that ES1 has the highest affinity (K_D = 3.36 × 10^-8) toward its target at 25°C. Calculation of thermodynamic parameters also showed positive values for enthalpy and entropy changes, which was representative of hydrophobic forces between c-Met and ES1. Furthermore, the positive value of Gibbs free energy indicated that c-Met binding to ES1 was enthalpy-driven. Taken together, we concluded that produced ES1 can be applied as promising scFv-based therapy for diagnosis or targeting of c-Met in various cancers.

The Binding Affinity of Small Molecules with Yam Tyrosinase (Catechol Oxidase): A Biophysical Study

Yam tyrosinase has become an economically essential enzyme due to its ease of purification and abundant availability of yam tubers. However, an efficient biochemical and biophysical characterization of yam tyrosinase has not been reported. In the present study, the interaction of yam (Amorphophallus paeoniifolius) tyrosinase was studied with molecules such as crocin (Crocus sativus), hydroquinone, and kojic acid. Surface plasmon resonance (SPR), fluorescence spectroscopy, and circular dichroism techniques were employed to determine the binding affinities and the changes in secondary and tertiary structures of yam tyrosinase in the presence of four relevant small molecules. Hydroquinone and crocin exhibited very low binding affinities of 0.24 M and 0.0017 M. Due to their apparent weak interactions, competition experiments were used to determine more precisely the binding affinities. Structure-function interrelationships can be correlated in great detail by this study, and the results can be compared with other available tyrosinases.

Comparative biophysical characterization: A screening tool for acetylcholinesterase inhibitors

Among neurodegenerative diseases, Alzheimer’s disease (AD) is one of the most grievous disease. The oldest cholinergic hypothesis is used to elevate the level of cognitive impairment and acetylcholinesterase (AChE) comprises the major targeted enzyme in AD. Thus, acetylcholinesterase inhibitors (AChEI) constitutes the essential remedy for the treatment of AD. The study aims to evaluate the interactions between natural molecules and AChE by Surface Plasmon Resonance (SPR). The molecules like alkaloids, polyphenols and substrates of AChE have been considered for the study with a major emphasis on affinity and kinetics. To better understand the activity of small molecules, the investigation is supported by both experimental and theoretical approach such as fluorescence, Circular Dichroism (CD) and molecular docking studies. Amongst the screened ones tannic acid showed promising results compared with others. The methodology followed here have highlighted many molecules with a higher affinity towards AChE and these findings may take lead molecules generated in preclinical studies to treat neurodegenerative diseases. Additionally, we suggest a unique signature for the heterogeneous analyte model using competitive experiments for analyzing simultanous interactions of both the analytes.

Five individual polyphenols as tyrosinase inhibitors: Inhibitory activity, synergistic effect, action mechanism, and molecular docking

Polyphenols can inhibit the enzymatic browning in food, but their indistinct synergistic effect and conformational change have limited their applications. In this paper, the mixture of quercetin, cinnamic acid and ferulic acid (Group 11, K_I = 0.239 mM) possessed a higher inhibition ability than quercetin (K_I = 0.361 mM), which could promote the spontaneous binding process. The final Group 11-tyrosinase complex is more stable, and the hydrophobic effect is the major driving force during the binding process. Moreover, there is not a direct relationship between the destruction of secondary structures and catalytic activity of tyrosinase. The interaction between ferulic acid and tyrosinase could destroy the secondary structures of enzyme but it had little impact on the tyrosinase activity. Molecular docking suggested that three polyphenols from Group 11 have synergistic effect on tyrosinase. This study provides new perspectives about the development of tyrosinase inhibitors in food products.