Interactions of Phenolic Compounds with Ovalbumin

Food Chemistry, 2012

Polyphenols are responsible for the major organoleptic characteristics of plant-derived foods and beverages. Here, we investigated the binding of several polyphenols to bovine serum albumin (BSA) at pH 7.5 and 25°C: catechins [(À)-epigallocatechin-3-gallate, (À)-epigallocatechin, (À)-epicatechin-3-gallate], flavones (kaempferol, kaempferol-3-glucoside, quercetin, naringenin) and hydroxycinnamic acids (rosmarinic acid, caffeic acid, p-coumaric acid). Fluorescence emission spectrometry and molecular docking were applied to compare experimentally determined binding parameters with molecular modelling. Among these polyphenols, (À)-epicatechin-3-gallate showed the highest Stern-Volmer modified quenching constant, followed by (À)-epigallocatechin-3-gallate. Similarly, (À)-epicatechin-3-gallate had the highest effect on the Circular Dichroic spectrum of BSA, while the changes induced by other polyphenols were negligible. Molecular docking predicted high binding energies for (À)-epicatechin-3-gallate and (À)-epigallocatechin-3-gallate for the binding site on BSA near Trp213. Our data reveal that the polyphenol structures significantly affect the binding process: the binding affinity generally decreases with glycosylation and reduced numbers of hydroxyl groups on the second aromatic ring.

Food Hydrocolloids, 2020

Oleuropein (OLE) is the major phenolic compound of olive leaves, known for its numerous health benefits. α-lactalbumin (ALA) is a milk protein constituting almost 20% of whey proteins with a high nutritional value owing to its essential amino acids. In this study, binding properties of OLE to ALA was explored by fourier transform infrared (FTIR) spectroscopy, fluorescent spectroscopy, dynamic light scattering, circular dichroism (CD) spectroscopy and molecular docking. The experimental results revealed a decrease in the fluorescence units due to binding process with fluorescent residues, especially with Trp104 which was then confirmed by CD spectroscopy and FTIR data and molecular docking. Also, the increase of OLE content resulted in the formation of a stable complex with a zeta potential near À 15 mV. The size of the complex decreased after addition of more OLE to the protein which was attributed to the formation of hydrogen bonds and folding of protein structure. Moreover, molecular docking indicated that hydrogen bonding plays a crucial role in the formation of OLE-ALA complexes including amide groups of Asn44 and Asn56 with the hydroxy groups of OLE. These findings indicated that ALA may be an ideal nanocarrier to load OLE for further applications in food and pharmaceutical fields.

Biointerface Research in Applied Chemistry, 2020

In this work is reported the study of the interaction between ovalbumin protein (OVA) and N-Phthaloyl gamma-aminobutyric acid derivative (NPG). The ovalbumin is a kind of globular protein present in chicken eggs, as part of serpins globular family proteins present in many biological systems and natural environment; is commonly used in the food industry and the pharmaceutical field as an alternative material for microencapsulation of water-soluble drugs. However, this egg protein has discrete binding sites for ligands as occur in their homologs in mammalian. Association constants and thermodynamic parameters for the interaction of OVA with PNG were determined by linear and 2D fluorescence techniques, zeta-potential, acoustic densimetry, molecular modeling (docking), and molecular dynamics simulations in water as solvent at physiological pH. Fluorescence quenching of the internal fluorophore (tryptophan/tyrosine) in the range of temperature 296.15 K - 308.15 K resulted in values for t...

In 1936, Rusznyák and Szent-Györgyi first drew attention to the therapeutically beneficial role of dietary flavonoids, which are the most common group of polyphenols ubiquitously present in plant based food and beverages. Recent years have witnessed a renascence of interest on these nutraceuticals, which, because of their high potency and low systemic toxicity, are gradually emerging as promising alternatives to conventional therapeutic drugs. There is a mounting evidence that various proteins frequently serve as targets for therapeutically important flavonoids. In this article we present perspectives exemplifying the growing potential of fluorescence spectroscopy as an exquisitely sensitive tool for noninvasive sensing of protein-flavonoid interactions at physiologically relevant concentrations, via measurements of steady state emission parameters as well as decay kinetics studies of the intrinsic fluorescence of the target (protein) and/or ligand (flavonoid). Especially, we highlight novel applications of the remarkably environment sensitive 'two color' fluorescence exhibited by many important flavonoids, which permits multiparametric and ratiometric measurements. To consolidate findings obtained via fluorescence spectroscopy, use of other relevant experimental biophysical techniques and molecular modeling have proved to be valuable and are also discussed here. Such complementary studies provide additional insights regarding the thermodynamics and conformational aspects of the protein-flavonoid interactions, together with details, at atomistic level, of the dominant noncovalent interactions involved in the docking of different flavonoids to their target proteins.

The structural thermodynamic and functional aspects of ovalbumin of chicken egg, unfolding induced by urea and βME(β-mercaptoethanol) has been studied at pH 7.0. Ovalbumin belongs to the Serpin class of protein. We have shown that the transition from native to denatured induced by urea and βME passes through essential unfolding of the protein. The phenomenon of denaturation of ovalbumin has been studied in terms in λ max , fluorescence intensity, change in Gibbs free energy at zero denaturant concentration, ∆G D (H 2 O) using the LEM (Linear Extrapolation Method). The fluorescence intensity (specially tryptophan fluorescence intensity) should be a minimum (10%) decrease on addition of 1M urea and maximum (97.7%) decrease on addition of 1N βME and 9M urea mixture in ovalbumin. Intensity quenching due to environmental change (or substantial conformational change) The chemical deaturation leading to exposure of tyrosine residues was studied with UV-difference spectroscopy as function of concentration of urea and βME. The study showed that ovalbumin was highly denatured in presence of urea and βME. The UV-difference spectra were evaluated to calculate Gibbs free energy change, ∆G D (H 2 O), using the linear extrapolation method, which reflects the stability difference between native and denatured species The study should that ovalbumin was highly denatured in presence of urea and βME due to disruption of hydrogen bonds as well as intra-and interchain disulfide bonds indicating the flexibility of ovalbumin increase on addition of βME, so it becomes susceptible to digestion.

Journal of Agricultural and Food Chemistry, 1993

The interactions between phospholipids and protein have been studied by nuclear magnetic resonance and circular dichroism techniques. Egg phosphatidylcholine (PC) did not affect the protein structure of ovalbumin (OA). However, lysophosphatidylcholine (LPC) changed the conformation of OA to increase the a-helix and to reduce the &sheet content by interaction with the protein. The heat stability of OA was enhanced by coupling with LPC and linoleic acid. The results of 31P and I3C NMR spectra and T2* relaxation times of the complexes showed that the molecular motion of acyl chain and glycerol carbons of LPC was restricted by interaction with the protein. The motion of the headgroup, however, remained unaffected. These results indicated that LPC bound to the protein through hydrophobic interaction and led to conformational change of protein structure. It is therefore suggested that the heat stability of emulsion composed of the complexes was closely correlated with its protein structure and the dynamic state of the complexes.

Current Drug Metabolism, 2013

In 1936, Rusznyák and Szent-Györgyi first drew attention to the therapeutically beneficial role of dietary flavonoids, which are the most common group of polyphenols ubiquitously present in plant based food and beverages. Recent years have witnessed a renascence of interest on these nutraceuticals, which, because of their high potency and low systemic toxicity, are gradually emerging as promising alternatives to conventional therapeutic drugs. There is a mounting evidence that various proteins frequently serve as targets for therapeutically important flavonoids. In this article we present perspectives exemplifying the growing potential of fluorescence spectroscopy as an exquisitely sensitive tool for noninvasive sensing of protein-flavonoid interactions at physiologically relevant concentrations, via measurements of steady state emission parameters as well as decay kinetics studies of the intrinsic fluorescence of the target (protein) and/or ligand (flavonoid). Especially, we highlight novel applications of the remarkably environment sensitive 'two color' fluorescence exhibited by many important flavonoids, which permits multiparametric and ratiometric measurements. To consolidate findings obtained via fluorescence spectroscopy, use of other relevant experimental biophysical techniques and molecular modeling have proved to be valuable and are also discussed here. Such complementary studies provide additional insights regarding the thermodynamics and conformational aspects of the protein-flavonoid interactions, together with details, at atomistic level, of the dominant noncovalent interactions involved in the docking of different flavonoids to their target proteins.

2017

Herausgegeben von Gunter Schöbel und der Europäischen Vereinigung zur Förderung der Experimentellen Archäologie.

University of Central Florida Masters Thesis, 2020

A large focus of Mississippian period archaeological research concerns itself with the role groups have played in the long distance social exchange networks prevalent across the Mississippian World. The Mill Cove Complex, a Mississippian period (A.D. 900-1250) village and dual sand mound burial complex situated on the periphery of the Mississippian World in Jacksonville, Florida is one such case. The St. Johns II people living at the Mill Cove Complex had connections deep into the Mississippian southeast reaching all the way to Cahokia. Understanding the role of these unique people within the large social networks requires an examination of all archaeological material recovered from the site. The lithic assemblage from modern excavations (1999 – present) is the final missing component in building this understanding. This lithic typology, based upon macroscopic and geochemical analysis, provides the final foundational set of data required for future research necessary to gain a more complete view of the St. Johns II people and their role in Mississippian long distance social exchange. It lends insight into local community practices as well, highlighting the importance of lithic raw material in ritual use, illustrating direct connections with Cahokia based upon the presence of projectile points from the American Bottom, and demonstrating the resourcefulness of a people who overcame a lack of raw material within their geographic area through the maintenance of social networks and conservative use and maximization of procured stone resources.

2008

La presente obra ha sido editada con subvención del MEC.