Saturday, April 30th, 2016

Notices

April 2, 2016 by admin  
Filed under Meetings

1.April 11, 2016 WBMSDG Meeting in Columbia; Speaker:Stephen E. Stein, Ph.D., NIST; Topic:Mass Spectral Libraries of Everything

2.April 15, 2016; Retirement Symposium in Honor of Dr. Sandy Markey

2.2016 Washington-Baltimore MSDG Young Investigator Travel Awards; Application deadline April 25, 2016

April Meeting

April 1, 2016 by admin  
Filed under Meetings

Speaker: Stephen E. Stein, Ph.D., Biomolecular Measurement Division, NIST

Topic: Mass Spectral Libraries of Everything

Date: Monday, April 11, 2016

Time: 6:15 pm: Dinner and Social Hour; 7:15 pm: Presentation; (Student Presentation: 7:10 pm; TBA)

Location: Shimadzu Scientific Instrument, Inc. Training Center 7100 Riverwood Drive, Columbia, MD 21046 (Directions)

Dinner and Social Hour Please RSVP to Jace Jones(jjones@rx.umaryland.edu) if you will be attending dinner.

Abstract: Libraries of mass spectra of known compounds have long been used for identifying compounds in GC/MS experiments and are finding increased use in tandem LC/MS experiments, especially in metabolomics and proteomics studies. Even given the substantial coverage of current libraries, a large fraction of the spectra remain unidentified. In some areas only a small fraction of components can be identified and even for well-developed areas (gc/ms of urine, for example), the origin of many spectra is unknown and likely to remain so for some time. To characterize these unknowns, we have been involved in building annotated libraries of good quality, but unidentified spectra in gc/ms and lc/ms experiments. Progress in three areas will be discussed: 1) GC/MS – multiple occurrences of spectra at fixed retention indices have been collected, clustered and annotated for a range of materials including urine, essential oils and various NIST reference materials; 2) LC/MS proteomics – we have constructed extensive libraries of unidentified peptide from proteomics analysis and developed special methods for their annotation and identification; 3) LC/MS metabolomics – we have built an collection of unidentified spectra from NIST urine reference materials and developed tools for organizing and identifying them. Illustration of the use of these libraries alongside more conventional libraries of reference spectra of identified compounds will be presented.

March 2016 Meeting

February 24, 2016 by admin  
Filed under Meetings

Speaker: Kristina Hakansson, Ph.D., Professor of Chemistry, University of Michigan

Topic: Fourier transform ion cyclotron resonance mass spectrometry for biomolecular identification and structural characterization

Date: Monday, March 14, 2016

Time: 6:15 pm: Dinner and Social Hour; 7:15 pm: Presentation; (Student Presentation: 7:10 pm; Lucía Geis-Asteggiante – Fenselau Group)

Location: Shimadzu Scientific Instrument, Inc. Training Center 7100 Riverwood Drive, Columbia, MD 21046 (Directions)

Dinner and Social Hour Please RSVP to Jace Jones(jjones@rx.umaryland.edu) if you will be attending dinner.

Abstract:
Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) provides unprecedented mass accuracy and resolution compared with other types of mass analyzers. In addition, this MS technique offers gas-phase activation/dissociation approaches (i.e., tandem mass spectrometry or MS/MS) that are complementary to the conventionally used collision-activated dissociation (CAD). For example, gas-phase ion-electron reactions, including electron capture dissociation (ECD) and electron detachment dissociation (EDD), trigger radical ion chemistry that results in unique fragmentation pathways compared to CAD. Fragment ion spectra are interpreted to deduce molecular structure.

However, the powerful methods of ECD and its cousin electron transfer dissociation (ETD) require at least two positive charges (because capture of one electron reduces the total charge by one and mass spectrometers cannot detect neutrals) and, thus, analysis of acidic biomolecules, which show improved ionization in negative ion mode, is challenging. We explore the utility of multivalent metals as charge carriers in ECD/ETD and found that positive ion mode ionization efficiency improves for sulfopeptides and acidic glycans. In addition, ECD of metal-adducted sulfated species proceeds with partial or complete retention of the highly gas-phase labile sulfonate, thereby allowing determination of its location. ECD/ETD of metal-adducted glycans provide intriguing fragmentation patterns with highly sought after sugar cross-ring fragmentation (which can provide linkage information) being dominant in several cases. EDD, which operates in negative ion mode, has lower fragmentation efficiency than ECD/ETD but can also be valuable for glycan analysis.

We also explore electron-induced dissociation (EID, compatible with both positive and negative ion mode) of singly charged analytes and have shown, e.g., that EID of manganese-adducted fatty acids allows double bond position determination. Furthermore, we have discovered that biomolecular anions can capture electrons (rather than lose electrons such as in EDD, or undergo electronic excitation such as in EID). This phenomenon, which we termed negative ion electron capture dissociation (niECD), results in charged-increased species that undergo dissociation analogous to that in ECD/ETD of cationic species. niECD is exciting for several reasons: 1) negative ion mode analysis yields improved ionization efficiency for many important acidic molecules, including phospho- and sulfopeptides. 2) FT-ICR MS detection efficiency is proportional to charge and thus niECD results in improved detection limits. 3) niECD is compatible with singly charged ions and thus allows coupling with matrix-assisted laser desorption/ionization (MALDI).

In NIH-funded work, we utilize the high performance of FT-ICR MS to interrogate enzyme-bound intermediates in natural product biosynthesis. We are also developing infrared multiphoton dissociation (IRMPD) for selective detection of biosynthetic protein active site peptides in complex metaproteomic samples.

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