Large scale localization of protein phosphorylation by use of electron capture dissociation mass spectrometry.

We used on-line electron capture dissociation (ECD) for the large scale identification and localization of sites of phosphorylation. Each FT-ICR ECD event was paired with a linear ion trap collision-induced dissociation (CID) event, allowing a direct comparison of the relative merits of ECD and CID for phosphopeptide identification and site localization. Linear ion trap CID was shown to be most efficient for phosphopeptide identification, whereas FT-ICR ECD was superior for localization of sites of phosphorylation. The combination of confident CID and ECD identification and confident CID and ECD localization is particularly valuable in cases where a phosphopeptide is identified just once within a phosphoproteomics experiment

Gas-Phase Complexes of Americium and Lanthanides with a Bis-triazinyl Pyridine: Reactivity and Bonding of Archetypes for F-Element Separations.

Bis-triazinyl pyridines (BTPs) exhibit solution selectivity for trivalent americium over lanthanides (Ln), the origins of which remain uncertain. Here, electrospray ionization was used to generate gas-phase complexes [ML3]3+, where M = La, Lu, or Am and L is EtBTP 2,6-bis(5,6-diethyl-1,2,4-triazin-3-yl)-pyridine. Collision-induced dissociation (CID) of [ML3]3+ in the presence of H2O yielded a protonated ligand [L(H)]+ and hydroxide [ML2(OH)]2+ or hydrate [ML(L-H)(H2O)]2+, where (L-H)- is a deprotonated ligand. Although solution affinities indicate stronger binding of BTPs toward Am3+ versus Ln3+, the observed CID process is contrastingly more facile for M = Am versus Ln. To understand the disparity, density functional theory was employed to compute potential energy surfaces for two possible CID processes, for M = La and Am. In accordance with the CID results, both the rate determining transition state barrier and the net energy are lower for [AmL3]3+ versus [LaL3]3+ and for both product isomers, [ML2(OH)]2+ and [ML(L-H)(H2O)]2+. More facile removal of a ligand from [AmL3]3+ by CID does not necessarily contradict stronger Am3+-L binding, as inferred from solution behavior. In particular, the formation of new bonds in the products can distort kinetics and thermodynamics expected for simple bond cleavage reactions. In addition to correctly predicting the seemingly anomalous CID behavior, the computational results indicate greater participation of Am 5f versus La 4f orbitals in metal-ligand bonding

CID overview

On December 1, 1984, NASA and the Federal Aviation Administration (FAA) conducted the first remotely piloted air-to-ground crash test of a transport category aircraft. The Full-Scale Transport Controlled Impact Demonstration (CID) was the culmination of 4 years of effort by the two agencies. NASA and the FAA had many objectives during the joint planning and execution of the Controlled Impact Demonstration. The structural loads experiment was very successful. Ninety-seven percent of the channels were active at impact. The data is still being assessed. Only a portion of the data is presented here; approximately 80 channels of data are available. Analysis of the remaining data is in progress. Interior photography was also very successful. One hundred percent of the cameras functioned. The film contains unique information on the development of fire and smoke in the interior of the aircraft. From a human tolerance point of view, the CID was simulation of a survivable crash

Top-Down Mass Analysis of Protein Tyrosine Nitration: Comparison of Electron Capture Dissociation with “Slow-Heating” Tandem Mass Spectrometry Methods

Tyrosine nitration in proteins is an important post-translational modification (PTM) linked to various pathological conditions. When multiple potential sites of nitration exist, tandem mass spectrometry (MS/MS) methods provide unique tools to locate the nitro-tyrosine(s) precisely. Electron capture dissociation (ECD) is a powerful MS/MS method, different in its mechanisms to the “slow-heating” threshold fragmentation methods, such as collision-induced dissociation (CID) and infrared multiphoton dissociation (IRMPD). Generally, ECD provides more homogeneous cleavage of the protein backbone and preserves labile PTMs. However recent studies in our laboratory demonstrated that ECD of doubly charged nitrated peptides is inhibited by the large electron affinity of the nitro group, while CID efficiency remains unaffected by nitration. Here, we have investigated the efficiency of ECD versus CID and IRMPD for top-down MS/MS analysis of multiply charged intact nitrated protein ions of myoglobin, lysozyme, and cytochrome c in a commercial Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer. CID and IRMPD produced more cleavages in the vicinity of the sites of nitration than ECD. However the total number of ECD fragments was greater than those from CID or IRMPD, and many ECD fragments contained the site(s) of nitration. We conclude that ECD can be used in the top-down analysis of nitrated proteins, but precise localization of the sites of nitration may require either of the “slow-heating” methods

MS²PIP prediction server : compute and visualize MS² peak intensity predictions for CID and HCD fragmentation

We present an MS2 peak intensity prediction server that computes MS2 charge 2+ and 3+ spectra from peptide sequences for the most common fragment ions. The server integrates the Unimod public domain post-translational modification database for modified peptides. The prediction model is an improvement of the previously published (MSPIP)-P-2 model for Orbitrap-LTQ CID spectra. Predicted MS2 spectra can be downloaded as a spectrum file and can be visualized in the browser for comparisons with observations. In addition, we added prediction models for HCD fragmentation (Q-Exactive Orbitrap) and show that these models compute accurate intensity predictions on par with CID performance. We also show that training prediction models for CID and HCD separately improves the accuracy for each fragmentation method

Electron Detachment Dissociation,and Collision-Induced Dissociation of Polyamidoamine (PAMAM) Dendrimer Ions with Amino, Amidoethanol, and Sodium Carboxylate Surface Groups

Here, we investigate the effect of the structure (generation) and nature of the surface groups of different polyamidoamine (PAMAM) dendrimers on electron-mediated dissociation, either electron capture dissociation (ECD) or electron detachment dissociation (EDD), and compare the fragmentation with that observed in collision-induced dissociation (CID). ECD and EDD of the PAMAM dendrimers esulted in simple mass spectra, which are straightforward to interpret, whereas CID produced complex mass spectra. The results show that electron-mediated dissociation (ECD and EDD) of PAMAM dendrimers does not depend on the nature of the surface group but tends to occur within the innermost generations. CID of the PAMAM dendrimers showed a strong dependence on the nature of the surface group and occurred mostly in the outer generation. The results demonstrate the potential utility of ECD and EDD as a tool for the structural analysis of PAMAM dendrimers

Whole-genome sequencing shows that patient-to-patient transmission rarely accounts for acquisition of Staphylococcus aureus in an intensive care unit

BACKGROUND  Strategies to prevent Staphylococcus aureus infection in hospitals focus on patient-to-patient transmission. We used whole-genome sequencing to investigate the role of colonized patients as the source of new S. aureus acquisitions, and the reliability of identifying patient-to-patient transmission using the conventional approach of spa typing and overlapping patient stay. METHODS Over 14 months, all unselected patients admitted to an adult intensive care unit (ICU) were serially screened for S. aureus. All available isolates (n = 275) were spa typed and underwent whole-genome sequencing to investigate their relatedness at high resolution. RESULTS Staphylococcus aureus was carried by 185 of 1109 patients sampled within 24 hours of ICU admission (16.7%); 59 (5.3%) patients carried methicillin-resistant S. aureus (MRSA). Forty-four S. aureus (22 MRSA) acquisitions while on ICU were detected. Isolates were available for genetic analysis from 37 acquisitions. Whole-genome sequencing indicated that 7 of these 37 (18.9%) were transmissions from other colonized patients. Conventional methods (spa typing combined with overlapping patient stay) falsely identified 3 patient-to-patient transmissions (all MRSA) and failed to detect 2 acquisitions and 4 transmissions (2 MRSA). CONCLUSIONS Only a minority of S. aureus acquisitions can be explained by patient-to-patient transmission. Whole-genome sequencing provides the resolution to disprove transmission events indicated by conventional methods and also to reveal otherwise unsuspected transmission events. Whole-genome sequencing should replace conventional methods for detection of nosocomial S. aureus transmission

CID flight/impact

The planned versus the actual results of the controlled impact demonstration of a transport aircraft are discussed. Remote control systems, site selection, manned flight tests, and wreckage distribution are discussed