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Title:   Author  item
                                            SIRK, TIMOTHY - Virginia Polytechnic Institution & State Universityitem
                                            BROWN, EUGENE - Virginia Polytechnic Institution & State Universityitem
                                            Friedman, Mendelitem
                                            SUM, AMEDEU - Colorado School Of Mines
  Submitted to: Journal of Agricultural and Food Chemistry
                                    Publication Type: Peer Reviewed Journal
                                    Publication Acceptance Date: 6/17/2009
                                    Publication  Date: 7/2/2009
                                    Citation: Sirk, T.W., Brown, E., Friedman, M., Sum, A. 2009. Molecular binding of catechins to biomembranes:Relationship to biolgical activity. Journal of Agricultural and Food Chemistry. 57:6720-6728.Interpretive Summary: Catechins (flavonoids), which are present in many widely-consumed foods such as apples, berries, chocolate, grapes, olives, and teas, are reported to be associated with a large number of beneficial health effects, including antimicrobial activities.  Previously we reported that tea catechins inactivated foodborne pathogens such as Bacillus cereus   and E. coli O157:H7 in liquids and in ground beef.  One mechanism by which catechins operate at the cellular-molecular level involves interaction with components of cell membranes leading to prevention of binding of bioactive molecules such as enzymes to receptor sites and/or disruption of cell membranes resulting in leakage of cell components followed by cell death. Large differences in biological activities of structurally different catechins may to be due to differences in relative affinities to lipid and glycoprotein layers of cell membranes.  To provide additional insights about the possible interactions of catechins with components of cell membranes, we are collaborating with colleagues at the Departments of Chemical and Mechanical Engineering, Virginia Polytechnic Institute and State University, Blacksburg, Virginia  and the Department of Chemical Engineering, Colorado School of Mines, Golden, Colorado on biophysical interactions of structurally different tea catechins with lipid bilayers (model cell membranes) by means of molecular dynamics simulations with the aid of complex mathematical tools.  The results of the present study reinforce and complement our previous study published in the Journal of Agricultural Food Chemistry, Volume 57, pages 7750-7758, 2008.  The results of both studies indicate that hydrogen bonding of phenolic hydroxyl groups of catechins to lipid bilayers of cell membranes may govern the mechanism of antimicrobial and other beneficial effects of catechins.  The described findings help us understand how catechins inhibit pathogenic bacteria, bacterial toxins, and cancer cells.
                                Technical Abstract: Molecular dynamics simulations were used to study the interactions of four catechins commonly found in tea with lipid bilayers of cell membranes.  Experimental studies in the literature have shown that catechins are linked to beneficial health effects, specifically as they are related to interactions with the cell membrane in acting as antibacterial and anticarcinogenic agents.  To better understand the molecular interaction of catechins with membranes, simulations experiments were performed using complex mathematical tools with four individual catechin molecules [epicatechin (EC), epigallocatechin (EGC), epicatechin-gallate (ECG), and epigallocatechin-gallate (EGCG)] interacting with the 1-palmitoyl-2-oleoyl phosphatidylcholine (POPC) lipid bilayer.  The simulations show that catechins possess a strong affinity for the lipid bilayer, causing some to be absorbed into the bilayer.  Following absorption, an expansion of the bilayer occurs due to the increased spacing of the lipid headgroups.  The molecular structure and aggregated condition of the catechins were observed to significantly influence their absorption into the bilayer, as well as their ability to form hydrogen bonds with the lipid headgroups.  Insight into these molecular interactions helps us to distinguish the structure-function relation of the catechins with lipid bilayers, and provides a foundation for a better understanding of the role of catechins in biological processes and the mechanisms that govern their bio-activity.


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