Fourier-transform electrospray instrumentation for tandem high-resolution mass spectrometry of large molecules

AbstractMass spectrometry instrumentation providing unit resolution and 10-ppm mass accuracy for molecules larger than 10 kDa was first reported in 1991. This instrumentation has now been improved with a 6.2-T magnet replacing that of 2.8 T, a more efficient vacuum system, ion injection with controlled ion kinetic energies, accumulated ion trapping with an open-cylindrical ion cell, acquisition of 2M data points, and updated electrospray apparatus. The resulting capabilities include resolving power of 5 × 105 for a 29-kDa protein, less than 1-ppm mass measuring error, and dissociation of protein molecular ions to produce dozens of fragment ions whose exact masses can be identified from their mass-to-charge ratio values and isotopic peak spacing

Rapid Identification of Emerging Pathogens: Coronavirus

New surveillance approach can analyze >900 polymerase chain reactions per day

Determining Collisional Cross Sections from Ion Decay with Individual Ion Mass Spectrometry

Collision cross section (CCS) measurements determined by ion mobility spectrometry (IMS) provide useful information about gas-phase protein structure that is complementary to mass analysis. Methods for determining CCS without a dedicated IMS system have been developed for Fourier transform mass spectrometry (FT-MS) platforms by measuring the signal decay during detection. Individual ion mass spectrometry (I2MS) provides charge detection and measures ion lifetimes across the length of an FT-MS detection event. By tracking lifetimes for entire ion populations, we demonstrate simultaneous determination of charge, mass, and CCS for proteins and complexes ranging from ∼8 to ∼232 kDa

Fe(III) Reducing Microorganisms from Iron Ore Caves Demonstrate Fermentative Fe(III) Reduction and Promote Cave Formation

<p>The banded iron formations (BIF) of Brazil are composed of silica and Fe(III) oxide lamina, and are largely covered by a rock cap of BIF fragments in a goethite matrix (canga). Despite both BIF and canga being highly resistant to erosion and poorly soluble, >3,000 iron ore caves (IOCs) have formed at their interface. Fe(III) reducing microorganisms (FeRM) can reduce the Fe(III) oxides present in the BIF and canga, which could account for the observed speleogenesis. Here, we show that IOCs contain a variety of microbial taxa with member species capable of dissimilatory Fe(III) reduction, including the <i>Chloroflexi, Acidobacteria</i> and the <i>Alpha</i>- <i>Beta</i>- and <i>Gammaproteobacteria</i>; however, Fe(III) reducing enrichment cultures from IOCs indicate the predominance of <i>Firmicutes</i> and <i>Enterobacteriaceae</i>, despite varying the carbon/electron donor, Fe(III) type, and pH. We used model-based inference to evaluate multiple candidate hypotheses that accounted for the variation in medium chemistry and culture composition. Model selection indicated that none of the tested variables account for the dominance of the <i>Firmicutes</i> in these cultures. The addition of H₂ to the headspace of the enrichment cultures enhanced Fe(III) reduction, while addition of N₂ resulted in diminished Fe(III) reduction, indicating that these <i>Enterobacteriaceae</i> and <i>Firmicutes</i> were reducing Fe(III) during fermentative growth. These results suggest that fermentative reduction of Fe(III) may play a larger role in iron-rich environments than expected. Our findings also demonstrate that FeRM are present within the IOCs, and that their reductive dissolution of Fe(III) oxides, combined with mass transport of solubilized Fe(II) by groundwater, could contribute to IOC formation.</p