Evaluation of beta-lactoglobulin as a stationary phase in high-performance liquid chromatography and as a buffer additive in capillary electrophoresis: observation of a surprising lack of stereoselectivity.
Previous studies have reported that alpha1-acid glycoprotein is quite similar in amino acid sequence and disulfide bond arrangements to members of a group of proteins which include beta-lactoglobulin (BLG). Since generally homologous proteins retain some similarity in function at the molecular level, we decided to evaluate the enantioselective properties of BLG as an high-performance liquid chromatographic chiral stationary phase (HPLC-CSP), and as an additive in capillary electrophoresis (CE). Two columns with differences in internal diameter and method of immobilisation on epoxide silica were prepared. Chiral acidic, basic and uncharged drugs were chromatographed and mobile phase parameters, namely pH and type of organic modifier, were varied in order to test the column performance. The CE approach has some advantages in that there is no need for immobilisation and only a small amount of protein is required. BLG was therefore tested as a CE buffer additive, using the same analytes as in the HPLC study. Although one would expect that a protein would display some enantioselectivity, BLG did not show any enantioselectivity whatsoever in either system; the protein has fairly weak interaction with the majority of the test solutes, as indicated by both techniques.
Department of Pharmaceutical Chemistry, University of Pavia, Italy.
G
G
Massolini
E
E
De Lorenzi
D K
DK
Lloyd
A M
AM
McGann
G
G
Caccialanza
D000818:Animals; D002021:Buffers; D002417:Cattle; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D019075:Electrophoresis, Capillary / Q000379:methods*; D006863:Hydrogen-Ion Concentration; D007782:Lactoglobulins / Q000737:chemistry; D004364:Pharmaceutical Preparations / Q000032:analysis*; D013237:Stereoisomerism
D002021:Buffers; D007782:Lactoglobulins; D004364:Pharmaceutical Preparations