9 research outputs found
Fragmentation of peptide negative molecular ions induced by resonance electron capture
A simple robust method to study resonance gas-phase reactions between neutral peptides of low volatility and free electrons has been designed and implemented. Resonance electron capture (REC) experiments were performed by several neutral model peptides and two naturally occurring peptides. The assignment of negative ions (NIs) formed in these gas-phase reactions was based on high mass-resolving power experiments. From these accurate mass measurements, it was concluded that fragment NIs formed by low (1–2 eV) energy REC are of the same types as those observed in electron capture∕transfer dissociation, where the positive charge is a factor. The main feature resulting from these REC experiments by peptides is the occurrence of zn−1 ions, which are invariably of the highest abundances in the negative ion mass spectra of larger peptides. [M–H]− NIs presumably the carboxylate anion structure dominate the REC spectra of smaller peptides. There was no evidence for the occurrence of the complementary reaction, i.e., the formations of cn+1 ions. Instead, cn ions arose without hydrogen∕proton transfer albeit with lower abundances than that observed for zn−1 ions. Only the amide forms of small peptides showed more abundant ion peaks for the cn ions than for the zn−1 ions. The mechanisms for the N–Cα bond cleavage are discussed
Is it time for transition from the subject-based to the integrated preclinical medical curriculum?
In the 60s of the last century, a number of new universities in the world began to apply an integrated program of medical education, the cornerstone of which was problem-oriented education. Thus, the Flexner model of higher education adopted by that time in most countries of the world, with its characteristic segregation of teaching of the theoretical and clinical disciplines, which had ceased to satisfy the needs of modern healthcare, was gradually replaced by a new system that put the student in the center of the educational
process and opened the way to active methods of teaching being focused on the end result – training of graduates whose qualifications most fully satisfy the needs of society. Over the half-century history of its existence, this system has been adopted by most medical universities in different countries of the world, in many of which it has undergone significant modifications in accordance with the needs of national educational standards. Many medical universities in Russia and other countries of the former Soviet Union showed interest in this system, some of the medical faculties of our country accepted certain elements of it. However, up to date no integrated preclinical medical education program has been applied in any of the Russian universities. Hereby we are undertaking an attempt to analyze the reasons and assess the possible perspectives for the transition of medical universities in Russia to teaching of fundamental and biomedical disciplines using the integrated curriculum
Exploring ECD on a Benchtop Q Exactive Orbitrap Mass Spectrometer
As
the application of mass spectrometry intensifies in scope and
diversity, the need for advanced instrumentation addressing a wide
variety of analytical needs also increases. To this end, many modern,
top-end mass spectrometers are designed or modified to include a wider
range of fragmentation technologies, for example, ECD, ETD, EThcD,
and UVPD. Still, the majority of instrument platforms are limited
to more conventional methods, such as CID and HCD. While these latter
methods have performed well, the less conventional fragmentation methods
have been shown to lead to increased information in many applications
including middle-down proteomics, top-down proteomics, glycoproteomics,
and disulfide bond mapping. We describe the modification of the popular
Q Exactive Orbitrap mass spectrometer to extend its fragmentation
capabilities to include ECD. We show that this modification allows
≥85% matched ion intensity to originate from ECD fragment ion
types as well as provides high sequence coverage (≥60%) of
intact proteins and high fragment identification rates with ∼70%
of ion signals matched. Finally, the ECD implementation promotes selective
disulfide bond dissociation, facilitating the identification of disulfide-linked
peptide conjugates. Collectively, this modification extends the capabilities
of the Q Exactive Orbitrap mass spectrometer to a range of new applications
Cellulose from Annual Plants and Its Use for the Production of the Films Hydrophobized with Tetrafluoroethylene Telomers
Cellulose HogC was produced by the modified traditional method with 35% yield from the stem of Sosnovsky hogweed and was characterized by elemental analysis, infrared (IR) spectroscopy, powder X-ray diffractometry, differential scanning calorimetry (DSC) and X-ray photoelectron spectroscopy (XPS). For HogC, the degree of crystallinity (approximately 70%) and the glass transition temperature (105–108 °C) were determined. It was found that the whiteness characteristic in the case of HogC was 92% and this significate was obtained without a bleaching procedure using chlorine-containing reagents. In this paper, the possibility of hydrophobization of HogC films by treatment with radiation-synthesized telomers of tetrafluoroethylene is shown. It was found that the contact angle of the telomer-treated cellulose film surface depended on the properties of the telomers (the chemical nature of the solvent, and the initial concentration of tetrafluoroethylene) and could reach 140 degrees
Characterization and Identification of Dityrosine Cross-Linked Peptides Using Tandem Mass Spectrometry
The use of mass spectrometry
coupled with chemical cross-linking
of proteins has become a powerful tool for proteins structure and
interactions studies. Unlike structural analysis of proteins using
chemical reagents specific for lysine or cysteine residues, identification
of gas-phase fragmentation patterns of endogenous dityrosine cross-linked
peptides have not been investigated. Dityrosine cross-linking in proteins
and peptides are clinical markers of oxidative stress, aging, and
neurodegenerative diseases including Alzheimer’s disease and
Parkinson’s disease. In this study, we investigated and characterized
the fragmentation pattern of a synthetically prepared dityrosine cross-linked
dimer of Aβ(1–16) using ESI tandem mass spectrometry.
We then detailed the fragmentation pattern of dityrosine cross-linked
Aβ(1–16), using collision induced dissociation (CID),
higher-energy collision induced dissociation (HCD), electron transfer
dissociation (ETD), and electron capture dissociation (ECD). Application
of these generic fragmentation rules of dityrosine cross-linked peptides
allowed for the identification of dityrosine cross-links in peptides
of Aβ and α-synuclein generated in vitro by enzymatic
peroxidation. We report, for the first time, the dityrosine cross-linked
residues in human hemoglobin and α-synuclein under oxidative
conditions. Together these tools open up the potential for automated
analysis of this naturally occurring post-translation modification
in neurodegenerative diseases as well as other pathological conditions