The disulphide isomerase DsbC cooperates with the oxidase DsbA in a DsbD-independent manner

In Escherichia coli , DsbA introduces disulphide bonds into secreted proteins. DsbA is recycled by DsbB, which generates disulphides from quinone reduction. DsbA is not known to have any proofreading activity and can form incorrect disulphides in proteins with multiple cysteines. These incorrect disulphides are thought to be corrected by a protein disulphide isomerase, DsbC, which is kept in the reduced and active configuration by DsbD. The DsbC/DsbD isomerization pathway is considered to be isolated from the DsbA/DsbB pathway. We show that the DsbC and DsbA pathways are more intimately connected than previously thought. dsbA - dsbC - mutants have a number of phenotypes not exhibited by either dsbA - , dsbC - or dsbA - dsbD - mutations: they exhibit an increased permeability of the outer membrane, are resistant to the lambdoid phage φ80, and are unable to assemble the maltoporin LamB. Using differential two-dimensional liquid chromatographic tandem mass spectrometry/mass spectrometry analysis, we estimated the abundance of about 130 secreted proteins in various dsb - strains. dsbA - dsbC - mutants exhibit unique changes at the protein level that are not exhibited by dsbA - dsbD - mutants. Our data indicate that DsbC can assist DsbA in a DsbD-independent manner to oxidatively fold envelope proteins. The view that DsbC's function is limited to the disulphide isomerization pathway should therefore be reinterpreted.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72894/1/MMI_6030_sm_Tables_S1-S4.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/72894/2/MMI_tables_s1-s4.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/72894/3/j.1365-2958.2007.06030.x.pd

Influence of Surfactant Structure on Photoluminescent ?-Conjugated Polymer Nanoparticles: Interfacial Properties and Protein Binding

π-Conjugated polymer nanoparticles (CPNs) are under investigation as photoluminescent agents for diagnostics and bioimaging. To determine whether the choice of surfactant can improve CPN properties and prevent protein adsorption, five nonionic polyethylene glycol alkyl ether surfactants were used to produce CPNs from three representative π-conjugated polymers. The surfactant structure did not influence size or yield, which was dependent on the nature of the conjugated polymer. Hydrophobic interaction chromatography, contact angle, quartz crystal microbalance, and neutron reflectivity studies were used to assess the affinity of the surfactant to the conjugated polymer surface and indicated that all surfactants were displaced by the addition of a model serum protein. In summary, CPN preparation methods which rely on surface coating of a conjugated polymer core with amphiphilic surfactants may produce systems with good yields and colloidal stability in vitro, but may be susceptible to significant surface alterations in physiological fluids

Conceptualising and measuring defensive marketing orientation (DMO): some inaugural thoughts on assessing marketing's place in 'society's doghouse'

Many have suggested marketing should be at the heart of organisational decision making whilst, coincidentally, lamenting its continued failure to earn strategic sway. Blame is frequently applied to the organisation itself, implying that marketers are unfairly marginalised. For marketing to succeed, however, it must appear both credible and contemporary, yet there is substantive research suggesting, 1) marketing's reputation is far from ideal and, 2) that practitioners remain tethered to traditional means of endeavour, often counter-productive in the context of newer, customer-focused, manifestos. Analysis of both marketing and psychology literatures reveals a lack of tools for determining marketer attitudes toward marketing orientation (MO) or post-MO concerns and, consequently, the commitment of the agent most critical to marketing's aspirations is rarely tested. This paper makes a case for rectifying such discrepancy and, via critical reflection on recent measurement debates, suggests an inaugural perspective on how evaluation might be achieved. An agenda for further research is offered, too