The polymer surface compositions of some polyesters of importance in biomaterial science and advanced drug delivery have been examined by x-ray photoelectron spectroscopy (XPS) and static secondary ion mass spectrometry (SSIMS). The XPS results show good quantitative stoichiometric correlation with the known chemical composition of the polyesters. The SIMS spectra show systematic fragmentation patterns in both positive and negative ion modes for the series of structurally related polymers. Evidence for the presence of radical cation formation in SIMS is presented. Comparison between the SIMS spectra of poly-glycolic acid and ply-lactic acid and the pyrolysis mass spectra of these polymers are made, and conclusions drawn on the different mechanisms of fragmentation. The combined application of SSIMS and XPS is shown to give a highly detailed analysis of these polyesters.

In recent years electrospray has become the most popular ionization technique for the analysis of biomolecules. In the present study, we have compared the electrospray and continuous-flow fast-atom bombardment methods of sample introduction and ionization for the analysis of sulphated and sulphonated lipids by tandem mass spectroscopy. The tandem mass spectra obtained when using the two ionization techniques were similar; however, small differences were evident. These differences indicate that the precursor ions generated by fast-atom bombardment and electrospray have different internal energies. The two ionization techniques give similar sensitivities for the recording of collision-induced dissociation spectra. Complete structural information can be obtained from 5 to 50 ng of lipid.

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Virulence attenuation in pathogenic bacteria without the use of antibiotics reduces the threat of infection while limiting the evolution of multidrug resistant strains. In many bacteria, virulence is regulated by population density dependent genetic switches, a phenomenon known as quorum sensing (QS). QS depends on the synthesis, transmission, and perception of a variety of low molecular weight signal molecules generically classified as autoinducers. Gram‐negative bacteria, such as Pseudomonas aeruginosa, predominantly “communicate” population density using N‐acyl‐L‐homoserine lactones (AHLs). Crucial to developing Gram‐negative QS modulating strategies, as well as modeling the presence/absence of QS under “real‐world” conditions, is the ability to accurately estimate the relative levels of the ring‐closed (bioactive) and ring‐open (bio‐inactive) forms. While some AHLs have been studied for their hydrolysis (ring‐opening) rates, no quantitative and comprehensive model for degradation exists. Here, we employ 1H‐NMR to monitor the hydrolysis of various AHLs under standard laboratory conditions at fixed acidities to develop such a model. Our model provides valuable insight into the availability of bioactive AHLs at relevant pH conditions and is a valuable tool in the development of QS‐control strategies and evaluation of AHL focused chemical assays and studies.

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The oxygen gllow discharge plasma modification of a contact lens material has been studied using SSIMS. SSIMS provides evidence at the molecular level for the conversion of surface organosiloxane species to inorganic silica functionalities with treatment time. These findings shown an excellent correlation with a dramatic increase in surface hydrolphilicity, as derived from surface energy studies, on plasma treatment. This study further illustrates the potential of SSIMS in the determination of the molecular changes at the surface during the plasma treatment process.

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