A highly sensitive and reliable method to sense and identify a single chemical at extremely low concentrations and high contamination is important for environmental surveillance, homeland security, athlete drug monitoring, toxin/drug screening, and earlier disease diagnosis. This article reports a method for precise detection of single chemicals. The hub of the bacteriophage phi29 DNA packaging motor is a connector consisting of 12 protein subunits encircled into a 3.6 nm channel as a path for dsDNA to enter during packaging and to exit during infection. The connector has previously been inserted into a lipid bilayer to serve as a membrane-embedded channel. Herein we report the modification of the phi29 channel to develop a class of sensors to detect single chemicals. The lysine-234 of each protein subunit was mutated to cysteine, generating 12-SH ring lining the channel wall. Chemicals passing through this robust channel and interactions with the SH group generated extremely reliable, precise, and sensitive current signatures as revealed by single channel conductance assays. Ethane (57 Da), thymine (167 Da), and benzene (105 Da) with reactive thioester moieties were clearly discriminated upon interaction with the available set of cysteine residues. The covalent attachment of each analyte induced discrete stepwise blockage in current signature with a corresponding decrease in conductance due to the physical blocking of the channel. Transient binding of the chemicals also produced characteristic fingerprints that were deduced from the unique blockage amplitude and pattern of the signals. This study shows that the phi29 connector can be used to sense chemicals with reactive thioesters or maleimide using single channel conduction assays based on their distinct fingerprints. The results demonstrated that this channel system could be further developed into very sensitive sensing devices.

A study carried out in five nursing homes and 13 general practitioner practices in the North West National Health Service region investigated medicine use in the homes and assessed the extent of inappropriate prescribing using consensus derived criteria. A review of the medical and nursing records of 101 residents showed that they were using a total of 714 items (mean 7.1; range 0 to 15), of which 659 were medicines, including 51 dressings, and 55 were other items such as stoma products. When criteria for inappropriate prescribing were developed and applied, 54 (53 per cent) residents were judged to have one or more inappropriate prescriptions. Medicines most frequently associated with inappropriate prescribing were those for the cardiovascular system (57 per cent of inappropriate prescriptions) and the central nervous system (17 per cent); diuretics accounted for 41 per cent of all inappropriate prescriptions. However, these results may not be representative of the true level of inappropriate prescribing. Of the eight GPs who filled in a questionnaire, five had a system for regularly reviewing drug treatment for nursing home residents; all considered that nursing home residents could benefit if pharmacists were to support GPs by offering advice about individual residents' drug treatment. Elderly residents in nursing homes are at high risk of inappropriate prescribing. A role for pharmacists in the monitoring of individual residents' prescriptions, in academic detailing or in guideline development could help in improving the quality of prescribing for nursing home residents.

New therapies are needed to eradicate androgen resistant, prostate cancer. Prostate cancer usually metastasizes to bone where the concentration of calcium is high, making Ca a promising toxin. Ionophores can deliver metal cations into cells, but are currently too toxic for human use. We synthesized a new rotaxane (CEHR2) that contains a benzyl 15-crown-5 ether as a blocking group to efficiently bind Ca. CEHR2 transfers Ca from an aqueous solution into CHCl to greater extent than alkali metal cations and Mg. It also transfers Ca to a greater extent than CEHR1, which is a rotaxane with an 18-crown-6 ether as a blocking group. CEHR2 was more toxic against the prostate cancer cell lines PC-3, 22Rv1, and C4-2 than CEHR1. This project demonstrates that crown ether rotaxanes can be designed to bind a targeted metal cation, and this selective cation association can result in enhanced toxicity.

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