Endgroup determination of synthetic polymers by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry

AbstractElectrospray ionization (ESI) was performed on a Fourier transform ion cyclotron resonance mass spectrometer for the endgroup and monomer mass determination of three poly(oxyalkylene)s in the mass range of 400–8000 Da. A combined use of the multiple charge states observed with ESI, leads to a threefold increase in accuracy of the endgroup and monomer determination. The improvement is attributed to the increased number of datapoints used for the regression procedure, yielding more accurate results. Endgroup masses are determined with a mass error better than 5 and 75 millimass units for the molecular weight range of 400–4200 and 6200–8000 Da, respectively. A mass error of better than 1 millimass unit was observed for all monomer mass determinations. With ESI, endgroup and monomer masses have been determined for poly(ethylene glycol) oligomers with a mass higher than 8000 Da. This is almost two times higher than observed with matrix-assisted laser desorption/ionization on the same instrument

Quantitative interior x-ray nanotomography by a hybrid imaging technique

Hierarchical structures appear often in life and materials sciences, and their characterization profits greatly from imaging methods that allow seamless probing of various length scales without sacrificing image quality. X-ray tomography is particularly adept at probing 3D structures; however, zooming in on a region of interest results in a loss of quantitativeness of image contrast and suffers from artifacts unless a priori knowledge or assumptions about the sample are used. Here, we demonstrate a hybrid technique that exploits a micrometer-resolution overview to realize ab initio nanoscale interior tomography with quantitative contrast. In a study of avian eggshell, a model for bionanoporous materials, our approach reveals a complex arrangement of vesicles with sizes ranging from hundred nanometers to a few micrometers. We anticipate that such an approach can be widely adopted and benefited from at synchrotron and laboratory sources, for instance, where such zooming capabilities are already present or can be readily realized

Ancient DNA derived from alkenone-biosynthesizing haptophytes and other algae in Holocene sediments from the Black Sea

Author Posting. © American Geophysical Union, 2006. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Paleoceanography 21 (2006): PA1005, doi:10.1029/2005PA001188.Holocene sea surface temperatures (SST) of the Black Sea have been reconstructed using sedimentary C37 unsaturated alkenones assumed to be derived from the coccolithophorid haptophyte Emiliania huxleyi, whose fossil coccoliths are an important constituent of the unit I sediments. However, alkenones can also be biosynthesized by haptophyte species that do not produce microscopic recognizable coccoliths. A species-specific identification of haptophytes is important in such U 37 K′-based past SST reconstructions since different species have different alkenone-SST calibrations. We showed that 18S rDNA of E. huxleyi made up only a very small percentage (less than 0.8%) of the total eukaryotic 18S rDNA within the up to 3600-year-old fossil record obtained from the depocenter (>2000 m) of the Black Sea. The predominant fossil 18S rDNA was derived from dinoflagellates (Gymnodinium spp.), which are predominant members of the summer phytoplankton bloom in the modern Black Sea. Using a polymerase chain reaction/denaturing gradient gel electrophoresis method selective for haptophytes, we recovered substantial numbers of a preserved 458-base-pair (bp)-long 18S rDNA fragment of E. huxleyi from the Holocene Black Sea sediments. Additional fossil haptophyte sequences were not detected, indicating that the E. huxleyi alkenone-SST calibration can be applied for at least the last ∼3600 years. The ancient E. huxleyi DNA was well protected against degradation since the DNA/alkenone ratio did not significantly decrease throughout the whole sediment core and 20% of ∼2700-year-old fossil E. huxleyi DNA was still up to 23,000 base pairs long. We showed that fossil DNA offers great potential to study the Holocene paleoecology and paleoenvironment of anoxic deep-sea settings in unprecedented detail.This work was supported by a grant from the Netherlands Organization for Scientific Research (NWO) (Open Competition Program 813.13.001 to M.J.L.C.) and NSF grant OCE0117824 to S.G.W., which we greatly appreciate