Investigation of the binding interactions of Bisdemethoxycurcumin, Diacetylcurcumin and Diacetylbisdemethoxycurcumin with bovine α-lactalbumin by experimental and theoretical analysis

Myricetin and morin hydrate inhibit amyloid fibril formation of bovine α-lactalbumin (BLA)

Amyloid fibrils are self-assembled aggregates of proteins and peptides that can lead to a broad range of diseases called amyloidosis. So far, no definitive and approved treatment to target directly amyloid fibrils has been introduced. Nevertheless, the search for small molecules with ability to inhibit and suppress fibril formation is an active and promising area of the research. Herein, the binding interactions and inhibitory effects of myricetin and morin hydrate on the in vitro fibrillation of bovine α-lactalbumin (BLA) have been investigated. The intrinsic fluorescence of BLA was quenched by myricetin and morin hydrate through combination of the static and dynamic quenching along with non-radiative Förster energy transfer mechanisms. The binding of these two flavonoids to BLA were not accompanied by major alteration in the conformation of BLA as evidenced by CD studies. The results of the fluorescence quenching analyses indicated almost the same binding affinities of myricetin and morin hydrate toward BLA (Kb ~ 106 M-1). However, the results of thioflavin T (ThT) assays showed that myricetin is a stronger inhibitor against BLA fibrillation compared to morin hydrate.

Interaction of gallium, indium and vanadyl diacetylcurcumin complexes with lysozyme: mechanistic aspects and evaluation of antiamyloidogenic activity

Diacetylcurcumin as a derivative of curcumin is a strong nitric oxide (NO) and O2-.anion scavenger. One strategy to improve stability of curcumin and its derivatives is complexation with metal. In this study, the binding interactions of gallium diacetylcurcumin (Ga(DAC)3), indium diacetylcurcumin (In(DAC)3), and vanadyl diacetylcurcumin (VO(DAC)2) with hen egg white lysozyme (HEWL) have been investigated. The results of fluorescence quenching analyses revealed that In(DAC)3 and VO(DAC)2 have higher binding affinities than Ga(DAC)3 towards HEWL. The interactions of these metal complexes were not accompanied by considerable conformational changes in the tertiary structure of HEWL. Furthermore, the inhibitory effects of these complexes on the amyloid fibrillation of HEWL were confirmed by the thioflavin T fluorescence assays. The kinetic curves of the fibrillation process illustrated that VO(DAC)2 has the highest inhibitory activity and In(DAC)3 has a significant delaying effect on the formation of amyloid fibrils of HEWL.

Flavor-food ingredient interactions in fortified or reformulated novel food: Binding behaviors, manipulation strategies, sensory impacts, and future trends in delicious and healthy food design

With consumers gaining prominent awareness of health and well-being, a diverse range of fortified or reformulated novel food is developed to achieve personalized or tailored nutrition using protein, carbohydrates, or fat as building blocks. Flavor property is a critical factor in the acceptability and marketability of fortified or reformulated food. Major food ingredients are able to interact with flavor compounds, leading to a significant change in flavor release from the food matrix and, ultimately, altering flavor perception. Although many efforts have been made to elucidate how food matrix components change flavor binding capacities, the influences on flavor perception and their implications for the innovation of fortified or reformulated novel food have not been systematically summarized up to now. Thus, this review provides detailed knowledge about the binding behaviors of flavors to major food ingredients, as well as their influences on flavor retention, release, and perception. Practical approaches for manipulating these interactions and the resulting flavor quality are also reviewed, from the scope of their intrinsic and extrinsic influencing factors with technologies available, which is helpful for future food innovation. Evaluation of food-ingredient interactions using real food matrices while considering multisensory flavor perception is also prospected, to well motivate food industries to investigate new strategies for tasteful and healthy food design in response to consumers' unwillingness to compromise on flavor for health.

In silico and in vitro studies of novel derivatives of tyrosol and raspberry ketone as the mushroom tyrosinase inhibitors

Tyrosinase is the key enzyme for melanin biosynthesis. Overproduction and deposition of this pigment cause different problems in various industries including agriculture and food. Finding safe tyrosinase inhibitors thus attracts great research interest. The goal of this study is evaluation of inhibitory potencies of some novel synthetic derivatives of tyrosol and raspberry ketone on diphenolase activity of mushroom tyrosinase. The ligands inhibited enzyme activity and compound 4-(2-(4-(hydroxymethyl)-2-methyl-1,3-dioxolan-2-yl)ethyl)phenol (1d) exhibited the most inhibitory potency (77% inhibition, IC₅₀ = 0.32 µmol L^-1) via the mixed inhibition mode. This compound was also safe according to the results of in vitro analyses. The enzyme-ligands interactions were theoretically and experimentally investigated using molecular docking and fluorescence quenching approaches, respectively. Modes of quenching and related parameters were also determined and molecular docking data showed that the ligands bind to important sites of the enzyme. These compounds, especially 1d, can be suggested as efficient candidates for further investigations.

Molecular dynamics simulation of metal free structure of Lmb, a laminin-binding adhesin of Streptococcus agalactiae: metal removal and its structural implications

Metal-binding receptors are one of the extracellular components of ATP-binding cassette transporters that are essential for regulation of metal homeostasis in bacteria. Laminin-binding adhesin (Lmb) of Streptococcus agalactiae falls under this class of solute binding proteins. It binds to zinc with a high affinity. Crystal structure of Lmb solved previously by our group reveals that the zinc is tetrahedrally coordinated by three histidines and a glutamate at the interdomain cleft. Lmb contains a long disordered loop close to the metal-binding site whose precise function is unknown. Several experimental attempts to produce apo-Lmb failed and this prompted us to carry out in silico studies to analyse the structural importance of the metal in Lmb. Here, we present the results of the molecular dynamics (MD) simulation studies of native, apo-(metal removed) and the long loop truncated Lmb models along with a homologous protein, TroA from Treponema pallidum that was taken up for validating the MD results of Lmb. Absence of a metal results in significant structural changes in Lmb, particularly at the metal-binding pocket and with the long loop, although the overall fold is retained. This study thus revealed that the Lmb can exist in different conformational states with subtle differences in the overall fold based on the presence or absence of the metal. This could be functionally important for a putative metal uptake and release and also for the adhesive function of Lmb in recognizing laminin, which contains a high number of zinc finger motifs.