Summary Genetic studies have identified a number of genes whose products appear to be required for the transport of the group A colicins and the single‐stranded DNA of certain filamentous bacteriophages into Escherichia coli. Mutations in these genes allow normal binding of the colicins to their outer‐membrane receptors and of the bacteriophage to the tip of specific conjugative pili, but do not allow translocation of the macromolecules to their target. These mutations have been designed‘tolerant’(tol) mutations and the protein products specified by these genes appear to comprise part of a transport system known as the Tol import system. Some of these genes have been isolated, sequenced and their protein products localized to the membranes or periplasm of E. coli. Information is also available regarding the domains of the colicins or phage proteins which interact with the Tol proteins. A preliminary model of the location and possible interactions of the Tol proteins is presented.

BackgroundDigital interventions have been effective in improving numerous health outcomes and health behaviors; furthermore, they are increasingly being used in different health care areas, including self-management of long-term conditions, mental health, and health promotion. The full potential of digital interventions is hindered by a lack of user engagement. There is an urgent need to develop effective strategies that can promote users’ engagement with digital interventions. One potential method is the use of technology-based reminders or prompts.ObjectiveTo evaluate the effectiveness of technology-based strategies for promoting engagement with digital interventions.MethodsCochrane Collaboration guidelines on systematic review methodology were followed. The search strategy was executed across 7 electronic databases: the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, Web of Science, the Education Resources Information Center (ERIC), PsycINFO, and the Cumulative Index to Nursing and Allied Health Literature (CINAHL). Databases were searched from inception to September 13, 2013, with no language or publication type restrictions, using three concepts: randomized controlled trials, digital interventions, and engagement. Gray literature and reference lists of included studies were also searched. Titles and abstracts were independently screened by 2 authors, then the full texts of potentially eligible papers were obtained and double-screened. Data from eligible papers were extracted by one author and checked for accuracy by another author. Bias was assessed using the Cochrane risk of bias assessment tool. Narrative synthesis was performed on all included studies and, where appropriate, data were pooled using meta-analysis. All findings were reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.ResultsA total of 14 studies were included in the review with 8774 participants. Of the 14 studies, 9 had sufficient data to be included in the meta-analyses. The meta-analyses suggested that technology-based strategies can potentially promote engagement compared to no strategy for dichotomous outcomes (relative risk [RR] 1.27, 95% CI 1.01-1.60, I2=71%), but due to considerable heterogeneity and the small sample sizes in most studies, this result should be treated with caution. No studies reported adverse or economic outcomes. Only one study with a small sample size compared different characteristics; the study found that strategies promoting new digital intervention content and those sent to users shortly after they started using the digital intervention were more likely to engage users.ConclusionsOverall, studies reported borderline positive effects of technology-based strategies on engagement compared to no strategy. However, the results have to be interpreted with caution. More research is needed to replicate findings and understand which characteristics of the strategies are effective in promoting engagement and how cost-effective they are.

The group A colicins and the DNA of many single-stranded filamentous bacteriophage are able to use combinations of the Tol proteins to gain entrance into or across the membrane of Escherichia coli. The TolA protein is a 421-amino acid residue integral membrane protein composed of three domains. Domain I, consisting of the amino-terminal 47 amino acids, contains a 21-residue hydrophobic segment that anchors the protein in the inner membrane. The remaining 374 amino acids, containing the other two domains, reside in the periplasmic space. Domain m, consisting of the carboxylterminal 120 residues, is considered to be the functional domain based on the location of the tolA592 deletion mutation. The internal 262 amino acids comprise domain II, which connects domains I and III together via short regions of polyglycine. It contains a large number of 3-to 5-residue polyaIanine stretches, many of which have a repeat of the sequence Lys-Ala-Ala-Ala-(Glu/Asp). Circular dichroism analysis of different portions of ToIA show domain II to be predominantly a-helical in structure while domain III contains -10% helical structure.The two membranes of Escherichia coli present a formidable barrier to the import of macromolecules into the cytoplasm (1). Yet macromolecules such as colicins or the DNA of certain filamentous bacteriophages are able to use specific systems for entry into the membrane or cytoplasm. The discovery of bacterial proteins involved in such import systems has been facilitated by the analysis of mutant bacteria unable to take up these macromolecules. For example, certain mutations in the tolQRAB gene cluster can render the bacteria insensitive both to infection by the filamentous single-stranded DNA bacteriophage and to the effects of the group A colicins (2-6). Import of these macromolecules into the tol mutants is inhibited after the phage or colicin has bound to its bacterial receptor, specific outer membrane proteins in the case of the colicins and the tip of specific conjugative pili for the filamentous bacteriophage. This implies that the import of phage DNA and colicins is at least a two-step process that requires the Tol proteins only after the molecules have interacted with their respective outer membrane receptors.TolA is one of the Tol proteins necessary for the uptake of all the group A colicins and Tol-dependent phage and, therefore, is thought to play a central role in the import process. TolA is a 44-kDa protein that is tightly associated with the inner membrane (7). Secondary structure predictions suggest that over one-half of the protein appears to be a long uninterrupted a-helix. This helical region contains repeats of the general sequence Lys1_2-Ala3-4-(Glu/Asp). Marqusee and Baldwin (8) (9) and plasmids pET3c and pLysS (10) were obtained from F. W. Studier (Brookhaven National Laboratory, Upton, NY). Plasmid pET3cIF contains the pUC18 Geneblock upper strand (Pharmacia) polylinker inserted by blunt-end ligation into the unique BamHI site distal to the T7 translation start site (S10)....