Ovalbumin folding

The setpin fold comprises a compact body of three antiparallel p sheets, A, B and C, which ate partly coveted by a helices (Figure 6.22). In the structure of the uncleaved form of ovalbumin, which can be regarded as the canonical structure of the serpins, sheet A has five strands. The flexible loop starts at the end of strand number 5 of p sheet A (plS in Figure 6.22), then... 

Figure 6,22 Schematic diagram of the structure of ovalbumin which illustrates the serpin fold. The structure is built up of a compact body of three antiparallel p sheets,...

The elution pattern in IEC results from the charge distribution on the folded chain. Therefore, IEC was used for indication, whether the native structure of the protein had been affected by previous RPC or not. Ribonuclease was found to retain its native structure, whereas bovine serum albumin, horse radish peroxidase, and ovalbumin were much altered through RPC on a C 18 column with a gradient water/ (ethanol-butanol 80 20) containing 0.012 M HC1 in both eluent components 59>. 

Foote and coworkers [120] developed a microfabricated system with the ability to electrophoretically preconcentrate fluorescently labeled proteins prior to their separation (see Fig. 6). The authors were able to preconcentrate the proteins using a porous silica membrane situated between adjacent microchannels that allowed for the passage of buffer ions, but excluded larger migrating molecules, such as proteins. Preconcentration factors of 600-fold were achieved using this on-chip format followed by an electrophoretic separation of proteins with SDS-PAGE. Using this chip, fluorescently labeled ovalbumin was detected at concentrations as low as 100 fmol by a combination of field-amplified injection and preconcentration at the membrane prior to microchip electrophoresis. 

For example, Kiosseoglou [75] discussed the role of surface-active lipids at the O/W interface on the viscoelastic parameters of bovine serum albumin (BSA), sodium caseinate, and egg yolk films during adsorption at the olive oil/ protein solution interface. It was postulated that film viscoelasticity was the result of the interaction of surface-active lipids with folded and unfolded proteins at the interface. Benjamins et al. [76] were the first to report on the development of interfacial viscoelasticity at the O/W interface. They found that the proteins with the least conformational flexibility increased the interfacial viscoelastic modulus the most (ovalbumin > BSA > sodium caseinate). 

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