Abstract
BackgroundThere have been many attempts to develop new materials with stability and high affinity towards immunoglobulins. Some of glycolipids such as gangliosides exhibit a high affinity toward immunoglobulins. However, it is considerably difficult to develop these glycolipids into the practical separation ligand due to their limited amounts. We thus focused our attention on the feasible use of "mannosylerythritol lipid A", a yeast glycolipid biosurfactant, as an alternative ligand for immunoglobulins, and undertook the investigation on the binding between mannosylerythritol lipid A (MEL-A) and human immunoglobulin G (HIgG).ResultsIn ELISA assay, MEL-A showed nearly the same binding affinity towards HIgG as that of bovine ganglioside GM1. Fab of human IgG was considered to play a more important role than Fc in the binding of HIgG by MEL-A. The bound amount of HIgG increased depending on the attached amount of MEL-A onto poly (2-hydroxyethyl methacrylate) (polyHEMA) beads, whereas the amount of human serum albumin slightly decreased. Binding-amount and -selectivity of HIgG towards MEL-A were influenced by salt species, salt concentration and pH in the buffer solution. The composite of MEL-A and polyHEMA, exhibited a significant binding constant of 1.43 × 106 (M-1) for HIgG, which is approximately 4-fold greater than that of protein A reported.ConclusionsMEL-A shows high binding-affinity towards HIgG, and this is considered to be due to "multivalent effect" based on the binding molar ratio. This is the first report on the binding of a natural human antibody towards a yeast glycolipid.
Highlights
There have been many attempts to develop new materials with stability and high affinity towards immunoglobulins
We describe for the first time that the yeast glycolipid shows a significant binding affinity towards a natural polyclonal human immunoglobulin G (HIgG)
Binding affinity of mannosylerythritol lipid A (MEL-A) toward HIgG GM1, which is a glycosphingolipid having one sialic acid, exhibits binding affinity towards IgG [9,10,11], and the sialic acid consisting of acetyl and glycerol groups plays an important role in carbohydrate-protein interactions [8,23,24,25]
Summary
There have been many attempts to develop new materials with stability and high affinity towards immunoglobulins. There have been many attempts to develop new materials possessing a stability and high affinity towards immunoglobulins, due to the high cost of protein-A or -G most commonly used as an affinity ligand for the proteins [4] Glycolipids such as gangliosides and glycosphingolipids carry out vital functions BMC Biotechnology 2001, 1:5 http://www.biomedcentral.com/1472-6750/1/5 recognition and cell proliferation) in biomembranes through protein-carbohydrate interactions [5,6] Some of these glycolipids exhibit a high affinity toward glycoproteins as a result of "multivalent or cluster effect" and are focused on as a new affinity ligand for immunoglobulins [7,8]. The possibility of developing these membrane glycolipids into the ligand, is far from straightforward due to their limited amounts and heterogeneity [13]
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