Simple mechanical molecular and supramolecular machines: Photochemical and Electrochemical control of switching processes

Photochemical control of a self-assembled supramolecular 1:1 pseudorotaxane (formed between a tetracationic cyclophane, namely the tetrachloride salt of cyclobis(paraquat-p-phenylene), and 1,5-bis[2-(2-(2-hydroxy)ethoxy)ethoxy]naphthalene) has been achieved in aqueous solution, The photochemical one-electron reduction of the cyclophane to the radical trication weakens the noncovalent bonding interactions between the cyclophane and the naphthalene guest-pi-pi interactions between the pi-electron-rich and pi-electron-poor aromatic systems, and hydrogen-bonding interactions between the acidic alpha-bipyridinium hydrogen atoms of the cyclophane and the polyether oxygen atoms of the naphthalene derivative-sufficiently to allow the guest to dethread from the cavity; the process can be monitored by the appearance of naphthalene fluorescence. The radical tricationic cyclophane can be oxidized back to the tetracation in the dark by allowing oxygen gas into the system. This reversible process is marked by the disappearance of naphthalene fluorescence as the molecule is recomplexed by the tetracationic cyclophane. This supramolecular system can be chemically modified such that the pi-electron-rich unit, either a naphthalene derivative or a hydroquinone ring, and the tetracationic cyclophane are covalently linked, We have demonstrated that the pi-electron-rich residue in this system is totally ''self-complexed'' by the cyclophane to which it is covalently attached. Additionally, the self-complexation can be switched ''off'' and ''ion'' by electrochemical two-electron reductions and oxidations, respectively, of the tetracationic cyclophane component, Thus, we have achieved the construction of two switches at the nanoscale level, one driven by photons and the other by electrons.</p

Critical care usage after major gastrointestinal and liver surgery: a prospective, multicentre observational study

Background Patient selection for critical care admission must balance patient safety with optimal resource allocation. This study aimed to determine the relationship between critical care admission, and postoperative mortality after abdominal surgery. Methods This prespecified secondary analysis of a multicentre, prospective, observational study included consecutive patients enrolled in the DISCOVER study from UK and Republic of Ireland undergoing major gastrointestinal and liver surgery between October and December 2014. The primary outcome was 30-day mortality. Multivariate logistic regression was used to explore associations between critical care admission (planned and unplanned) and mortality, and inter-centre variation in critical care admission after emergency laparotomy. Results Of 4529 patients included, 37.8% (n=1713) underwent planned critical care admissions from theatre. Some 3.1% (n=86/2816) admitted to ward-level care subsequently underwent unplanned critical care admission. Overall 30-day mortality was 2.9% (n=133/4519), and the risk-adjusted association between 30-day mortality and critical care admission was higher in unplanned [odds ratio (OR): 8.65, 95% confidence interval (CI): 3.51–19.97) than planned admissions (OR: 2.32, 95% CI: 1.43–3.85). Some 26.7% of patients (n=1210/4529) underwent emergency laparotomies. After adjustment, 49.3% (95% CI: 46.8–51.9%, P<0.001) were predicted to have planned critical care admissions, with 7% (n=10/145) of centres outside the 95% CI. Conclusions After risk adjustment, no 30-day survival benefit was identified for either planned or unplanned postoperative admissions to critical care within this cohort. This likely represents appropriate admission of the highest-risk patients. Planned admissions in selected, intermediate-risk patients may present a strategy to mitigate the risk of unplanned admission. Substantial inter-centre variation exists in planned critical care admissions after emergency laparotomies