Electron Transfer Dissociation Mass Spectrometry of Hemoglobin on Clinical Samples

A mass spectrometry-based assay combining the specificity of selected reaction monitoring and the protein ion activation capabilities of electron transfer dissociation was developed and employed for the rapid identification of hemoglobin variants from whole blood without previous proteolytic cleavage. The analysis was performed in a robust ion trap mass spectrometer operating at nominal mass accuracy and resolution. Subtle differences in globin sequences, resulting with mass shifts of about one Da, can be unambiguously identified. These results suggest that mass spectrometry analysis of entire proteins using electron transfer dissociation can be employed on clinical samples in a workflow compatible with diagnostic applications.     

Imaging mass spectrometry using peptide isoelectric focusing

Imaging Mass Spectrometry (IMS) has emerged as a powerful technique in the field of proteomics. The use of Immobilized pH Gradient-IsoElectric Focusing (IPG-IEF) is also a new trend, as the first dimension of separation, in shotgun proteomics. We report a combination of these two outstanding technologies. This approach is based on the separation of shotgun-produced peptides by IPG-IEF. The peptides are then transferred by capillarity to a capture membrane, which is then scanned by the mass spectrometer to generate MS images. This high-throughput methodology allows a preview of the sample to be obtained in a single day. We report the application of this new pipeline for differential comparison of the membrane proteome of two different strains of Staphylococcus aureus bacteria in a proof-of-principle experiment.     

Dual picosecond dye lasers synchronously pumped by a mode locked cw yag laser

The performance of a novel dual dye laser system synchronously pumped by the frequency doubled output of a mode-locked CW-YAG laser is evaluated in relation to pulsewidth, pulse substructure, pulse spectral width and timing jitter. The behavior of the system is adequately described by a theoretical model which includes the time dependent gain and losses due to frequency bandwidth, cavity length mismatch and output coupler. The jitter is significantly reduced from that obtained with CW gas laser pumping as a result of the shorter pump pulse (50 ns instead of ≈100 ps). A routine operating condition uses 2-plate birefringen filters, 0.8 W pump power at 532 nm, to yield two 2.0 ps pulses having a cross correlation width of 3.8 ps, and 30 mW average power from each laser.     

Studies of fast inertial and diffusive motions in liquids

Recent studies of quasi-free molecular motion in liquids will be presented. Of particular interest is the inertial regime of motion which occurs significantly only if the free rotational period is comparable with the effective collisional frequency in the liquid. Results on the isomerism of stilbene and on the anisotropy decays for aniline in solution have exposed regions where the motion is nondiffusive. The results are compared with current statistical mechanical theories. This research was supported by grants from NSF, NIH and AROD and by the LRSM program at the University of Pennsylvania.     

Tres forte separation de l'etat fondamental 6S52 DU Mn2+ dans des boracites de Cl,Br et I en phase cubique

A very strong axial Zero Field Splitting is found for the ground state (⁶S_{$\text{5}\text{2}$}) of the Mn²⁺ in the cubic phase of Mg-Cl, Zn-Cl, Zn-Br and Zn-I Boracites going from 1.6 cm^-1 for Zn-Cl to 3.8 cm^-1 for Zn-I.     

Spectral manifestations of nonradiative processes in azulene

The linewidths for S₁ ← S₀ (at 14 652 cm⁻¹) and S₂ ← S₀ (at 28 048 cm⁻¹) of azulene in a naphthalene host crystal at 1.2°K are presented along with measurements of the line narrowing due to perdeuteration of the azulene. The results are related to current ideas of nonradiative processes in azulene and azulene-d₈.     

Radiative decay of benzophenone low pressure gas

The radiative decay of benzophenone low pressure gas was studied subsequent to pulse excitation at several wavelengths. Estimates of the emission rates and quantum yields for the fast and slow decay processes lead to models for the isolated molecule radiationless processes; both somewhat different from that recently proposed by Busch et al. We propose that it is the very rapid intersystem crossing process that produces the non-stationary mixed singlet-triplet levels.     

Design, synthesis, and photochemical validation of peptide linchpins containing the S,S-tetrazine phototrigger

The design, solid-phase synthesis, and photochemical validation of diverse peptide linchpins, containing the S,S-tetrazine phototrigger, have been achieved. Steady state irradiation or femtosecond laser pulses confirm their rapid photofragmentation. Attachment of peptides to the C- and N-termini will provide access to diverse constrained peptide constructs that hold the promise of providing information about early peptide/protein conformational dynamics upon photochemical release.     

Wipe sampling procedure coupled to LC–MS/MS analysis for the simultaneous determination of 10 cytotoxic drugs on different surfaces

A simple wipe sampling procedure was developed for the surface contamination determination of ten cytotoxic drugs: cytarabine, gemcitabine, methotrexate, etoposide phosphate, cyclophosphamide, ifosfamide, irinotecan, doxorubicin, epirubicin and vincristine. Wiping was performed using Whatman filter paper on different surfaces such as stainless steel, polypropylene, polystyrol, glass, latex gloves, computer mouse and coated paperboard. Wiping and desorption procedures were investigated: The same solution containing 20% acetonitrile and 0.1% formic acid in water gave the best results. After ultrasonic desorption and then centrifugation, samples were analysed by a validated liquid chromatography coupled to tandem mass spectrometry (LC–MS/MS) in selected reaction monitoring mode. The whole analytical strategy from wipe sampling to LC–MS/MS analysis was evaluated to determine quantitative performance. The lowest limit of quantification of 10 ng per wiping sample (i.e. 0.1 ng cm⁻²) was determined for the ten investigated cytotoxic drugs. Relative standard deviation for intermediate precision was always inferior to 20%. As recovery was dependent on the tested surface for each drug, a correction factor was determined and applied for real samples. The method was then successfully applied at the cytotoxic production unit of the Geneva University Hospitals pharmacy.     

The polarized charge-transfer spectrum of crystalline anthracene-TNB complex

The intermolecular charge-transfer spectrum of the crystalline anthracene-TNB complex has been measured, using polarized light. The crystal spectrum differs from that of the solution to a much greater degree than is the case for ordinary aromatic systems. The transition is polarized along the intermolecular axis and is blue-shifted with respect to the solution. There is pronounced vibrational structure, including a prominent 250 cm^-1 interval. A Davydov splitting of approximately 200 cm^-1 is observed, and this is shown to be in reasonable agreement with the known crystal structure and with the symmetry assignment of the transition, which is A′ ← A′ for the complex in solution and A ← A in the crystal.