Characterization of associated proteins and phospholipids in natural rubber latex.

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.

[1]  K. Cornish,et al.  Microstructure of Purified Rubber Particles , 2000, International Journal of Plant Sciences.

[2]  J. Jacob,et al.  Phospholipid composition of the membrane of lutoids from Hevea brasiliensis latex , 1976 .

[3]  H. Hasma,et al.  Composition of lipids in latex of Hevea brasiliensis clone RRIM 501 [Malaysia] , 1986 .

[4]  J. Sakdapipanich,et al.  Characterization of fatty acids linked to natural rubber—role of linked fatty acids on crystallization of the rubber , 2000 .

[5]  H. Mantsch,et al.  High-pressure infrared spectroscopic evidence of water binding sites in 1,2-diacyl phospholipids , 1988 .

[6]  M. Cereijido,et al.  Introduction to the study of biological membranes , 1970 .

[7]  Adya P. Singh,et al.  Simple and Rapid Methods for SEM Observation and TEM Immunolabeling of Rubber Particles , 2003, The journal of histochemistry and cytochemistry : official journal of the Histochemistry Society.

[8]  W. Bowler.  Electrophoretic Mobility Study of Fresh Hevea Latex , 1953 .

[9]  X. Baur,et al.  Isolation and identification of hevein as a major IgE-binding polypeptide in Hevea latex. , 1997, The Journal of allergy and clinical immunology.

[10]  E. Fukusaki,et al.  Structural characterization of alpha-terminal group of natural rubber. 1. Decomposition of branch-points by lipase and phosphatase treatments. , 2005, Biomacromolecules.

[11]  K. Shiba,et al.  Initiation of biosynthesis in cis polyisoprenes , 1995 .

[12]  T. Kondo,et al.  Approximate analytic expression for the electrophoretic mobility of colloidal particles with surface-charge layers , 1989 .

[13]  D. Beezhold,et al.  IgE epitope analysis of the hevein preprotein; a major latex allergen , 1997, Clinical and experimental immunology.

[14]  K. Ute,et al.  Structural characterization of alpha-terminal group of natural rubber. 2. Decomposition of branch-points by phospholipase and chemical treatments. , 2005, Biomacromolecules.

[15]  A. Galston,et al.  The physiology and biochemistry of rubber formation in plants , 1947, The Botanical Review.

[16]  J. Carreau,et al.  Adaptation of a macro-scale method to the micro-scale for fatty acid methyl transesterification of biological lipid extracts , 1978 .

[17]  J. Sakdapipanich,et al.  Highly-Purified Natural Rubber by Saponification of Latex: Analysis of Residual Proteins in Saponified Natural Rubber , 2008 .