Anne Routledge

The influence of various physical and chemical factors on the swelling of polystyrene and PEG based resins in greener organic solvents has been systematically investigated. In general, chemical factors: the nature of the functionality/linker and the degree of loading were found to have a far larger influence on the swelling of the resins than physical parameters such as bead size. The results are interpreted in terms of Hansen solubility parameters for the solvents and there is evidence that some solvents interact with the polymeric core of a resin whilst others interact with the functionality. The results are extended to a study of the changes in resin swelling observed during both deprotection and chain elongation reactions during solid phase peptide synthesis.

The use of a range of green solvents to swell a diverse range of resins used in solid-phase synthesis is investigated.

A new array‐based technology for the simultaneous capture, chemical labelling and mass spectrometry analysis of peptides is presented. Isotopically labelled self‐assembled monolayer (SAM) gold arrays are constructed and used simultaneously to capture and label a range of peptides. The array‐immobilised, labelled peptides were released by MALDI ablation, analysed by MALDI mass spectrometry and readily identified as labelled peptides from their characteristic isotope pattern. This new solid‐phase array platform has the advantage of minimal sample manipulation and is suitable for multiple analyses of single protein digests on a single MALDI target plate.

Mono‐ and disaccharide‐functionalised conjugates of the fluoroquinolone antibiotic ciprofloxacin have been synthesised and used as chemical probes of the bacterial uptake of glycosylated ciprofloxacin. Their antimicrobial activities against a panel of clinically relevant bacteria were determined: the ability of these conjugates to inhibit their target DNA gyrase and to be transported into the bacteria was assessed by using in vivo and in vitro assays. The data suggest a lack of active uptake through sugar transporters and that although the addition of monosaccharides is compatible with the inhibition of DNA gyrase, the addition of a disaccharide results in a significant decrease in antimicrobial activity.

A series of fluoroquinolone conjugates was synthesised by linking the carboxylic acid functionality of the carboxylate-type siderophore staphyloferrin A and its derivatives to the piperazinyl nitrogen of ciprofloxacin and norfloxacin via amide bond formation. Four siderophore–drug conjugates were screened against a panel of bacteria associated with infection in humans. Whilst no activity was found against ciprofloxacin- or norfloxacin-resistant bacteria, one of the conjugates retained antibacterial activity against fluoroquinolone-susceptible strains although the structure of its lysine-based siderophore component differs from that of the natural siderophore staphyloferrin A. In contrast, three ornithine-based siderophore conjugates showed significantly reduced activity against strains that are susceptible to their respective parent fluoroquinolones, regardless of the type of fluoroquinolone attached or chirality at the ornithine C_α-atom. The loss of potency observed for the (R)- and (S)-ornithine-based ciprofloxacin conjugates correlates with their reduced inhibitory activity against the target enzyme DNA gyrase.

We have explored two divinylbenzene cross-linked polystyrene supports for use in a solid-supported N-terminal peptide tagging strategy. Resin-bound tags designed to be cleaved in a single step at the N-terminus of peptides have been devised and explored as peptide N-terminal tagging reagents (constructs) for subsequent mass spectrometric analysis. While the brominated tagging approach shows promise, the use of these specific solid supports has drawbacks, in terms of tagging reaction scale, for real applications in proteomics.

Liquid chromatography/mass spectrometry (LC/MS) experiments are described, leading to a reliable method for the measurement of perfluorooctanesulfonic acid (PFOS) and other perfluorinated chemicals (PFCs) in foods. Separations were performed on new fluorinated stationary phases, RP Octyl (‐C ₈ F ₁₇ ) or propyl‐perfluorobenzene (‐C ₃ H ₆ ‐C ₆ F ₅ ), to ensure resolution of PFOS and interfering taurohydroxycholate isomers. Aqueous ammonium formate (5 mM) and methanol were used as the mobile phases. The mass spectrometer was operated in negative electrospray ionisation mode, recording two transitions for each analyte and one for each internal standard. The purities of the analytical standards for the eleven target perfluoro analytes (C ₇ to C ₁₂ carboxylic acids, C ₄ , C ₆ and C ₈ sulfonic acids, and octanesulfonamide (PFOSA)) were found to be in close agreement with the supplied values; the lowest purity was 91%. Five candidate internal standards were investigated, ¹³ C ₄ ‐PFOS, ¹³ C ₄ ‐perfluorooctanoic acid, ¹³ C ₂ ‐perfluorodecanoic acid, D ₉ ‐ n ‐ethylperfluorooctanesulfonamidoethanol (D ₉ ‐ n ‐Et‐FOSE) and D ₃ ‐ n ‐methylperfluorooctanesulfonamide (D ₃ ‐ n ‐Me‐FOSA); the purities were all >98%. The use of tetrahydro‐PFOS generated backgrounds (>1 µg/kg) for perfluoroheptanoic acid and perfluorobutanesulfonic acid. Similarly D ₉ ‐ n ‐Et‐FOSE was unacceptable and D ₃ ‐ n ‐Me‐FOSA was volatile, leaving no clear candidate for normalisation of the measurement of PFOSA. Severe matrix‐induced suppression and enhancement effects influenced ionisation, making external calibration and quantification problematic. This was addressed by a parallel standard addition and matrix‐matching approach, comparing ionisation in methanol, in procedural blanks and in food‐based extracts. The limits of detection (LODs) of 0.001–0.01 µg/kg in solvent and 0.01–1 µg/kg in foods demonstrate that this method is suitable for the determination of PFCs in all food to the required 1 µg/kg reporting level. © Crown copyright 2009. Reproduced with the permission of Her Majesty's Stationery Office. Published by John Wiley & Sons, Ltd.