Interaction between Silver Nanoparticles and Two Dehydrogenases: Role of Thiol Groups

Abstract

Widely used silver nanoparticles (AgNPs) are readily accessible to biological fluids and then surrounded by proteins. However, interactions between AgNPs and proteins are poorly understood. Two dehydrogenases, glyceraldehyde‐3‐phosphate dehydrogenase (GAPDH) and malate dehydrogenase (MDH), are chosen to investigate these interactions. Ag bound to thiol groups of these enzymes significantly decreases the number of free thiols available. Dose‐dependent inhibition of enzyme activities is observed in both AgNPs and Ag+ treatments. Based on the concentration required to inhibit 50% activity, GAPDH and MDH are 24–30 fold more sensitive to Ag+ than to AgNPs suggesting that the measured 4.2% Ag+ containing AgNPs can be responsible for the enzymes inhibition. GAPDH, with a thiol group in its active site, is more sensitive to Ag than MDH, displaying many thiol groups but none in its active site, suggesting that thiol groups at the active site strongly determines the sensitivity of enzymes toward AgNPs. In contrast, the dramatic changes of circular dichroism spectra show that the global secondary structure of MDH under AgNPs treatment is more altered than that of GAPDH. In summary, this study shows that the thiol groups and their location on these dehydrogenases are crucial for the AgNPs effects.

Biologically rapid synthesized silver nanoparticles from aqueous Eucalyptus camaldulensis leaf extract: Effects on hyphal growth, hydrolytic enzymes, and biofilm formation in Candida albicans

“…Bio‐AgNPs from E. citriodora leaf extract inhibited biofilms in C. albicans due to the alteration of membrane surface charges of pathogenic fungi following the exposure to the nanoparticles, leading to membrane disruption (Paosen et al, 2019). The release of Ag + from AgNPs was demonstrated to react with the thiol group of protein portion, generally presented in microbial enzymes, such as glyceraldehyde‐3‐phosphate dehydrogenase and malate dehydrogenase, resulting in pathogen inactivation (Jiang et al, 2019). Other workers demonstrated that AgNPs synthesized using S. cumini seed extract reduced Candida biofilm because the nanoparticles could anchor onto the cell surface and penetrate into the cytoplasm causing morphological damages (Jalal et al, 2019).…”

Emerging trends in clinical implications of bio-conjugated silver nanoparticles in drug delivery

“…However, a preliminary surface modification of the nanoparticle with thiol group source serving molecules such as 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-N- [ Other AgNP stabilizing and capping moieties that afford a thiol functionality to the AgNPs for their further bio-conjugation include alkylthiols: HS(CH2)nCH3 (n=11); thioalkyl acids: HS(CH2)nCH3 (n = 10); thioalkyl amines: HS(CH2)nNH2 (n=2); and thioalkyl-PEG-R (R = H, CH3, CH2COOH, NH2) [87]. Besides, the strong covalent/ dative linkages and surface adsorption, thiol group also interacts directly with the AgNPs surface through considerable electrostatic interactions between the sulfur atom and the nanoparticle [88]. Furthermore, the thiol-containing biomolecules such as cysteine, cysteamine, homocysteine, glutathione that interact with the nanoparticle surface by non-covalent electrostatic interactions through their 'S' atom under acidic conditions assist in the colloidal stabilization of AgNPs and essentially, serve as linker molecules for tethering AgNPs to the biomolecule of interest [89,90].…”

Molecular‐Level Contact of Graphene/Silver Nanowires through Simultaneous Dispersion for a Highly Stable Wearable Electrothermal Heater

“…A robust freestanding film (FSF) was easily manufactured from the PSSLGS solution by vacuum filtration because of the molecular‐level contacts (e.g., disulfide–silver, graphene–silver, and π–π interactions) (Figure 1). [ 23,24 ] After filtration, the PSSLGS residue formed on the nylon filter coagulated upon immersion in acetone. The resulting PSSLGS FSF was highly flexible and easily folded and unfolded (Figure S14a, Supporting Information).…”

“…Hence, mixing AgNWs with graphene may reduce their contact resistance as graphene acts as a heat spreader to prevent the breakage of AgNWs at high temperatures. However, because AgNWs and graphene tend to significantly aggregate owing to mutual interactions, [ 22–27 ] the poor dispersion of AgNWs and graphene may prevent heat dissipation and may lead to AgNW breakage during Joule heating. Therefore, molecular‐level contact between AgNWs and graphene is required to stabilize the conducting hybrid network system.…”