The radical cation of cytosine (Cyt.+ ) is generated by dissociative oxidation from a ternary CuII complex in the gas phase. characterized infrared multiple photon dissociation (IRMPD) spectroscopy fingerprint region, UV/Vis photodissociation (UVPD) spectroscopy, ion-molecule reactions, and theoretical calculations (density functional theory ab initio). experimental IRMPD spectrum features diagnostic bands for two enol-amino keto-amino tautomers Cyt.+ that are calculated to be among lowest...

The single-conformation spectroscopy and infrared-induced conformational isomerization of a model protonated pentapeptide [YGPAA + H]+ is studied under cryo-cooled conditions in the gas phase. Building on recent results ( DeBlase , A. F. ; J. Am. Chem. Soc. 2017 139 5481 - 5493 ), firm assignments are established for presence two conformer families with distinct infrared ultraviolet spectra, using IR-UV depletion spectroscopy. Families (A B) share similar structure near N-terminus but differ...

Incorporation of the unnatural d-proline (DP) stereoisomer into a polypeptide sequence is typical strategy to encourage formation β-hairpin loops because natural sequences are often unstructured in solution. Using conformation-specific IR and UV spectroscopy cold (≈10 K) gas-phase ions, we probe inherent conformational preferences DP LP diastereomers protonated peptide [YAPAA+H]+, where only intramolecular interactions possible. Consistent with solution-phase studies, one conformers...

D-Proline (DPro, DP) is widely utilized to form β-hairpin loops in engineered peptides that would otherwise be unstructured, most often as part of a DPG sub-unit forms β-turn. To observe whether facilitated this effect short protonated peptides, conformation specific IR-UV double resonance photofragment spectra the cold (∼10 K) DP and LP diastereomers pentapeptide YAPGA was carried out hydride stretch (2800-3700 cm-1) amide I/II (1400-1800 regions. A model localized Hamiltonian developed...

The formation and investigation of sulfur-based cysteine radicals cationized by a group 1A metal ion or Ag+ in the gas phase are reported. Gas-phase ion-molecule reactions (IMR) infrared multiple-photon dissociation (IRMPD) spectroscopy revealed that Li+ , Na+ K+ adducts radical remain S-based as initially formed. Theoretical calculations for three alkali ions found lowest-energy isomers Cα -based radicals, but they not observed experimentally owing to barriers associated with hydrogen-atom...

Intramolecular hydrogen atom transfer (HAT) was examined in homocysteine (Hcy) thiyl radical/alkali metal ion complexes the gas phase by combination of experimental techniques (ion-molecule reactions and infrared multiple photon dissociation spectroscopy) theoretical calculations. The results unequivocally show that complexation (as opposed to protonation) regiospecifically generated Hcy radical promotes its rapid isomerisation into an α-carbon via HAT. Theoretical calculations were employed...

Since our drug raid during the Fall of 1969 and present application peer group approach much has been explored concerning changing attitudes behavior. The complexities learning process, including student, methodology materials, must be re-examined. Drugs are not problem. Finding ways to communicate so that student a chance involve himself actively in process is secret. An active exchange honest information will, long run, provide more lasting impact. Many approaches solving problem being...

The determination of peak purity in chromatographic methods used pharmaceutical analysis is a vital step evaluating specificity to ensure the safe production medicines. Current assessments accomplished through diode array detectors (DAD) and mass spectrometry (MS) have some challenges that could lead misinterpreted values when sample under evaluation susceptible limitations these techniques. Two-dimensional liquid chromatography (2D-LC) has ability resolve difficult-to-separate mixtures,...

The gas-phase linearization of cyclotides via site-selective ring opening at dehydroalanine residues and its application to cyclotide sequencing is presented. This strategy relies on the ability incorporate into macrocyclic peptide ions, which easily accomplished through an ion/ion reaction. Triply protonated cations are transformed radical reaction with sulfate anion. Subsequent activation cation generates a single cysteine residue, identified by odd-electron loss ·SCH2CONH2. presence in...

A strategy to sequence lysine-containing cyclic peptides by MSn is presented. Doubly protonated ions are transformed into gold (I) cationized peptide via cation switching ion/ion reaction. Gold(I) cationization facilitates the oxidation of neutral lysine residues in gas phase, weakening adjacent amide bond. Upon activation, facile cleavage N-terminal oxidized residue provides a site-specific ring opening pathway that converts acyclic analogs. The ensuing ion contains imine as new N-terminus...

(2,2′-Bipyridine)M═O+ ions (M = Cu, Ni, Co) were generated by collision-induced dissociation and near-UV photodissociation of readily available [(2,2′-bipyridine)MII(NO3)]+ in the gas phase, their structure was confirmed ion–molecule reactions combined with isotope labeling. Upon storage a quadrupole ion trap, (2,2′-bipyridine)M═O+ spontaneously added water, formed [(2,2′-bipyridine)M═O + H2O]+ complexes eliminated OH upon further photodissociation. This reaction sequence can be accomplished...

Incorporation of the unnatural D-proline ( D P) stereoisomer into a polypeptide sequence is typical strategy to encourage formation β-hairpin loops because natural sequences are often unstructured in solution.Using conformation-specific IR and UV spectroscopy cold (10 K) gas-phase ions, we probe inherent conformational preferences P L diastereomers protonated peptide [YAPAA+H] + , where only intramolecular interactions possible.Consistent with solution phase studies, one conformers...

Tethered peptides are synthetic in which a chemical linkage between two remote sites the peptide sequence bind these together.The Fairlie group has devised tether that locks pentapeptide 'core' into single turn of an alpha helix, robust to large swings pH, temperature, and denaturant.By changing chirality amino acids, left-(D) right-handed (L) helices can be exclusively formed.Catenating sub-units leads α-helices greater length.This talk describes propensity tethered maintain their helical...

This talk will describe single-conformation IR and UV spectroscopy of a series single-turn double-turn alpha helices as cryo-cooled, gas phase ions.Synthesized samples tethered pentapeptides are known to form in aqueous solution.When L-amino acids used, right-handed helix is formed while D-amino produce left-handed helix.Due the tether, these structures remarkably stable solution over wide range temperatures, pH, denaturant.They can be concatenated, making LL, DD, LD, DL forms.When...