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Fig. 3. GC-MS n analysis of culture media (a) without treatment, (b) AgNPs treated.To specifically monitor effects of AgNPs on cell wall PGN glycan strands, the amount ofMuramic acid (MA), released into the culture media was studied. For this purpose, GC-MS n was carried out before and after treatment. It can be seen from Figure 3b that AgNPstreatment caused an increase in MA concentration in the culture medium.Studies demonstrated that PGNs should be digested for HPLC analysis.We hypothesized that, as PGNs structure were broken by AgNPs treatment, theproduced fragments can be monitored using HPLC/MS n analyses. Increase of the lowmolecular weight fractions on the HPLC chromatogram after AgNPs treatment willapprove our hypothesis, that they caused PGN breakage. The MS n analysis of them hasbeen performed usingmass spectrometry. Itcan be seen from thePGN standard solutionsample (Figure 4a) thefragments higher than2500 m/z. On the otherhand the treatment ofAgNPs caused somebreakage of PGNsstructure, which isshown on part Figure4b. From that treatmentmore fragmentation onPGN with low molecularweight, (fragmentslower than 2800m/z) were obtained.These results indicatethat the reaction withAgNPs affects thepeptide primary structureand increasing thenumber of degradationproducts after thesePGNs treatment.Fig. 4. Mass Spectrometry analysis of the PGN standardsolution sample (a), and after the AgNPs treatment (b) ofPGNs, using Finigan LCQ deca ion trap instrumentation.References1. Shrivastava, S., et al.Nanotechnology 18, 225103 (2007).2. Dibrov, P., et al. Antimicrob. Agents Chemother. 46, 2668-2670 (2002).3. Vollmer, W., Blanot, D., de Pedro, M.A. FEMS. Microbiol. Rev. 32, 149-167 (2008).275