Microgram level radiocarbon (14C) determination on carbonaceous particles in ice

In climate research the interest on carbonaceous particles has increased over the last years because of their influence on the radiation balance of the earth. Nevertheless, there is a paucity of available data regarding their concentrations and sources in the past. Such data would be important for a better understanding of their effects and for estimating their influence on future climate. Here, a technique is described to extract carbonaceous particles from ice core samples with subsequent separation of the two main constituents into organic carbon (OC) and elemental carbon (EC) for analysis of their concentrations in the past. This is combined with further analysis of OC and EC 14C/12C ratios by accelerator mass spectrometry (AMS), what can be used for source apportionment studies of past emissions. We further present how 14C analysis of the OC fraction could be used in the future to date any ice core extracted from a high-elevation glacier. Described sample preparation steps to final analysis include the combustion of micrograms of water–insoluble carbonaceous particles, primary collected by filtration of melted ice samples, the graphitisation of the obtained CO2 to solid AMS target material and final AMS measurements. Possible fractionation processes were investigated for quality assurance. Procedural blanks were reproducible and resulted in carbon masses of 1.3 ± 0.6 μg OC and 0.3 ± 0.1 μg EC per filter. The determined fraction of modern carbon (fM) for the OC blank was 0.61 ± 0.13. The analysis of processed IAEA-C6 and IAEA-C7 reference material resulted in fM = 1.521 ± 0.011 and δ13C = −10.85 ± 0.19‰, and fM = 0.505 ± 0.011 and δ13C = −14.21 ± 0.19‰, respectively, in agreement with consensus values. Initial carbon contents were thereby recovered with an average yield of 93%.

Cupiennin 1a, an antimicrobial peptide from the venom of the neotropical wandering spider Cupiennius salei, also inhibits the formation of nitric oxide by neuronal nitric oxide synthase

Cupiennin 1a (GFGALFKFLAKKVAKTVAKQAAKQGAKYVVNKQME-NH2) is a potent venom component of the spider Cupiennius salei. Cupiennin 1a shows multifaceted activity. In addition to known antimicrobial and cytolytic properties, cupiennin 1a inhibits the formation of nitric oxide by neuronal nitric oxide synthase at an IC50 concentration of 1.3 +/- 0.3 microM. This is the first report of neuronal nitric oxide synthase inhibition by a component of a spider venom. The mechanism by which cupiennin 1a inhibits neuronal nitric oxide synthase involves complexation with the regulatory protein calcium calmodulin. This is demonstrated by chemical shift changes that occur in the heteronuclear single quantum coherence spectrum of 15N-labelled calcium calmodulin upon addition of cupiennin 1a. The NMR data indicate strong binding within a complex of 1 : 1 stoichiometry.