title: Characterization of associated proteins and phospholipids in natural rubber latex.
abstract: Non-rubber components present in natural rubber (NR) latex, such as proteins and phospholipids, are presumed to be distributed in the serum fraction as well as surrounding the rubber particle surface. The phospholipid-protein layers covering the rubber particle surface are especially interesting due to their ability to enhance the colloidal stability of NR latex. In this study, we have characterized the components surrounding the NR particle surface and investigated their role in the colloidal stability of NR particles. Proteins from the cream fraction were proteolytically removed from the NR latex and compare to those from the serum fractions using SDS-polyacrylamide gel electrophoresis revealing that both fractions contained similar proteins in certain molecular weights such as 14.5, 25 and 27 kDa. Phospholipids removed from latex by treatment with NaOH were analyzed using (1)H-NMR spectroscopy and several major signals were assignable to -(CH(2))(n)-, -CH(2)OP, -CH(2)OC═O and -OCH(2)CH(2)NH-. These signals are important evidence that indicates phospholipids associate with the rubber chain. The colloidal behavior of rubber lattices before and after removal of protein-lipid membrane was evaluated by zeta potential analysis and scanning electron microscope (SEM). The lowest zeta potential value of NR particles was observed at pH 10, consequently leading to the highest stability of rubber particles. Additionally, SEM micrographs clearly displayed a gray ring near the particle surface corresponding to the protein-lipid membrane layer.
authors.affiliation: Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Mahidol University, Rama VI Rd., Phayathai, Bangkok 10400, Thailand.
authors.forename: Jitlada
authors.initials: J
authors.lastname: Sansatsadeekul
authors.forename: Jitladda
authors.initials: J
authors.lastname: Sakdapipanich
authors.forename: Porntip
authors.initials: P
authors.lastname: Rojruthai
mesh_terms: D004591:Electrophoresis, Polyacrylamide Gel; D005227:Fatty Acids / Q000737:chemistry; D008401:Gas Chromatography-Mass Spectrometry; D006863:Hydrogen-Ion Concentration; D007840:Latex / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008855:Microscopy, Electron, Scanning; D008970:Molecular Weight; D010316:Particle Size; D010743:Phospholipids / Q000737:chemistry*; D010940:Plant Proteins / Q000737:chemistry*; D012408:Rubber / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D005227:Fatty Acids; D007840:Latex; D010743:Phospholipids; D010940:Plant Proteins; D012408:Rubber