Systematic screening of soluble expression of antibody fragments in the cytoplasm of E. coli

Table 3 Molecular mass of scFv fragments produced with and without CyDisCo

scFv	CyDisCo	NEM treatment	Molecular mass (Da)
Herceptin	−	−	27188
	−	+	27688
	+	−	27185
	+	+	27185
Tysabri	−	−	27753
	−	+	28256
	+	−	27751
	+	+	27752

Masses were determined by electrospray mass spectrometry with (+) or without (−) prior treatment with N-ethylmaleimide (NEM) which reacts with free thiol groups. Reaction with NEM increases the mass of the protein by 125 Da. In the absence of CyDisCo a 500 Da shift in mass was observed upon NEM treatment consistent with four free thiol groups i.e. no disulfide bonds. In contrast in the presence of CyDisCo no shift in mass was observed upon NEM treatment consistent with both disulfide bonds being formed

ISSN: 1475-2859