Collected fractions were analyzed by SDS-PAGE

Collected fractions were analyzed by SDS-PAGE. for sample preparation in proteomic technology. == 1 Introduction == Analysis (+)-α-Tocopherol of complex biological fluids such as serum, plasma, urine, and tissue homogenates (+)-α-Tocopherol is complicated by the large dynamic range of individual proteins that are present in these complex mixtures. This range is up to 108to 1012in serum and plasma, and up to 105in cells [13]. In human plasma, 22 proteins account for 99% of the overall protein content [2]. Human serum albumin (HSA) and immunoglobulins are the most abundant ones and they represent over 75% of all proteins present (+)-α-Tocopherol in plasma, while the concentrations of low abundance proteins range from milli- to zeptomolar levels [1,2,4]. HSA and IgG hinder the detection, isolation and identification of other biopolymers present in trace amounts. The low abundance proteins are frequently potential biomarkers or biomarker candidates for various diseases [1]. After isolation and purification, some of biologically active proteins that are present in human plasma in very low concentrations such as clotting factors and inhibitors can be used for CD221 therapeutic purposes [57]. Both optimization industrial scale plasma fractionation and serum and plasma separation in order to isolate low abundance proteins in these complex biological fluids have alredy been topic of many studies [8,9]. However, there is still need for further optimization, especially regarding the speed, high throughput and in case of plasma fractionation, optimization of the yield, purity and characterization of isolated therapeutic proteins [10.11]. Already in very early stage of development monoliths made of polyglycidyl methacrylate polymers have been successfully used for separation of proteins from human plasma [12,13]. Their good mechanical strength, high porosity and dynamic capacity for large molecules, high separation speed and high flow rates at a very low pressure drop enable rapid processing of large volumes of complex biological mixtures [14]. Additionally their pH resistance makes possible cleaning and sanitation under harsh conditions such as high and low pH, and repeating use of monolithic support also for isolation and high-throughput analysis of proteins for therapeutic use [13,15]. Sample displacement chromatography (SDC) for preparative purification of peptides in reversed-phase mode was introduced by Hodges et al. [16,17]. When this chromatographic separation mode is applied, during loading, there is competition among the sample components for the binding sites of the hydrophobic surface of the stationary phase. The more molecules compete for these sites, the more components with lower affinity to the surface will be displaced and eluted from the column. Veeraragavan et al. [18] applied the SDC method for purification of proteins in ion-exchange mode. The Hodges group further developed SDC for purification of synthetic peptides, and new system design for rapid, simple and cost-effective procedure for the purification of peptide mixtures was introduced [19]. The same group also modified the SDC procedure for preparative isolation of proteins from troponin, a rabbit skeletal multi protein complex [20]. Manseth et al. [21] applied SDC to purify active thrombin from plasma of Atlantic salmon on a Heparin Sepharose affinity matrix. In this paper we demonstrate that if monolithic supports were used for separation of complex biological mixtures in SDC mode, the composition of bound and eluted proteins is dependent on column loading. Under overloading conditions, the weakly bound proteins are displaced by strongly binding ones, and this phenomenon was not dependent on column size. It could be demonstrated that small monolithic columns are ideal supports for development of new methods, especially for separation of complex biological fluids, and for sample.