Fluorescent probe were used to evaluate the effects of catechin on the structural parameters (annular lipid fluidity, transbilayer lateral and rotational mobility and protein clustering) of the Porphyromonas gingivalis outer membrane (OPGs). An experimental procedure was used on the basis of selective quenching of 1,6-diphenyl-1,3,5-hexatriene (DPH) and 1,3-di(1-pyrenyl)propane (Py-3-Py) by trinitrophenyl groups and radiationless energy transfer from the tryptophans of membrane proteins to Py-3-Py and DPH. Catechin increased the bulk lateral and rotational mobility, annular lipid fluidity of OPGs lipid bilayers, and had greater fluidizing efficacy on the outer monolayer than the inner monolayer. It also caused membrane proteins to cluster. Based on these effects of catechin on OPGs, the antibacterial and antiviral actions of catechin can be partially explained.

Ⅰ. INTRODUCTION
Ⅱ. MATERIALS AND METHODS
    1. Matarials
    2. Bacterial growth conditions
    3. Isolation of outer membrane
    4. TNBS Labelling
    5. Effect of Catechin on the Structure of theIndividual Monolayers of OPGs: SelectiveQuenching of Py-3-Py
    6. Determination of Annular Lipid Fluidity in OPGs
    7. Determination of Protein Distribution in theOPGs Llipid Bilayer
    8. Effect of Catechin on the Rotational Mobilityof Bulk OPGs
    9. Effect of Catechin on the Separate Monolayersof OPGs: Selective Quenching of DPH
    10. Fluorescence Measurements
Ⅲ. RESULTS
    1. Effects of Catechin on the Rate and Rangeof Lateral Mobility in Bulk Bilayer OPGs
    2. Effects of Catechin on the Range and Rateof Transbilayer Asymmetric Lateral Mobilityof OPGs Monolayers
    3. Effects of Catechin on Annular Lipid Fluidityin the OPGs Lipid Bilayer
    4. Effects of Catechin on Protein Distribution inOPGs−
    5. Effects of Catechin on the Range ofRotational Mobility of Bulk Bilayer OPGs
    6. Effects of Catechin on the Range ofTransbilayer Asymmetric Rotational Mobilityof OPGs Monolayers
Ⅳ. DISCUSSION
ACKNOWLEDGMENTS

• 성기수(부산대학교 치의학전문대학원 치과약리학교실) | Ki-Soo Seong (Department of Dental Pharmacology, Pusan National University School of Dentistry)
• 김태영(부산대학교 치의학전문대학원 치과약리학교실) | Tae-Young Kim (Department of Dental Pharmacology, Pusan National University School of Dentistry)
• 주지민(부산대학교 치의학전문대학원 치과약리학교실, 부산대학교 치의생명과학연구소, 부산대학교 치의생명과학 교육연구팀) | Ji-Min Ju (Department of Dental Pharmacology, Pusan National University School of Dentistry, Dental and Life Science Institute, School of Dentistry, Pusan National University, Education and Research Team for Life Science on Dentistry, Pusan National University )
• 김다솔(부산대학교 치의학전문대학원 치과약리학교실, 부산대학교 치의생명과학연구소) | Da-Sol Kim (Department of Dental Pharmacology, Pusan National University School of Dentistry, Dental and Life Science Institute, School of Dentistry, Pusan National University)
• 장혜옥(부산대학교 치의학전문대학원 치과약리학교실, 부산대학교 치의생명과학연구소, 부산대학교 치의생명과학 교육연구팀) | Hye-Ock Jang (Department of Dental Pharmacology, Pusan National University School of Dentistry, Dental and Life Science Institute, School of Dentistry, Pusan National University, Education and Research Team for Life Science on Dentistry, Pusan National University ) Corresponding author