Video Experimental Relacionado
Updated: Jun 18, 2026
11:45
Preparation of Stable Bicyclic Aziridinium Ions and Their Ring-Opening for the Synthesis of Azaheterocycles
Published on: August 22, 2018
Evidencia de estructuras de diketopiperazina y oxazolona para el ion HA b2+
Brittany R Perkins1, Julia Chamot-Rooke, Sung Hwan Yoon
1Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, USA.
Journal of the American Chemical Society
|November 13, 2009
Resumen
Este estudio revela que la fragmentación del péptido produce una mezcla de estructuras de diketopiperazina y oxazolona para el ión b. Estos hallazgos ayudan a comprender la estructura del péptido y las vías de fragmentación.
Área de la Ciencia:
- Química Analítica La Química Analítica es la
- Física Química Física Química es la física de la química.
- La bioquímica es la bioquímica.
Sus antecedentes:
- La fragmentación de péptidos es un proceso clave en la espectrometría de masas.
- El ion b(2)(+) puede adoptar distintos isómeros estructurales, incluyendo la oxazolona y la ditopiperazina.
- Comprender estas estructuras es crucial para una identificación y secuenciación precisas de péptidos.
Objetivo del estudio:
- Para dilucidar la identidad estructural del ion b(2)(+) generado a partir de HAAAA protonado.
- Para investigar la coexistencia de estructuras de oxazolona y diketopiperazina en la fase gaseosa.
- Validar los hallazgos experimentales con predicciones computacionales.
Principales métodos:
- Espectroscopia de disociación por multifotones en el infrarrojo (IRMPD). espectroscopia de disociación por multifotones en el infrarrojo.
- Modelado computacional (por ejemplo, cálculos de DFT).
- Experimentos de intercambio de hidrógeno-deuterio (H/D) en la fase gaseosa.
Principales resultados:
- El espectro experimental de IRMPD del ion b(2)(+) coincidía con los espectros experimentales y teóricos de la ditetopiperazina.
- Una banda espectral distinta a 1875 cm (-1) indicó la presencia de una especie de oxazolona.
- El intercambio H/D confirmó una mezcla de dos poblaciones distintas, consistente con las estructuras de la ditetopiperazina y la oxazolona.
Conclusiones:
- El ion b(2)(+) del HAAAA protonado existe como una mezcla de isómeros de diketopiperazina y oxazolona.
- La espectroscopia IRMPD y el intercambio H/D son potentes herramientas para diferenciar estos productos de fragmentación de péptidos.
- Esta heterogeneidad estructural tiene un impacto en el análisis e interpretación de los péptidos.
Más Videos Relacionados
Videos de Conceptos Relacionados
01:25Basicity of Heterocyclic Aromatic Amines
Heterocyclic amines, where the N atom is a part of an alicyclic system, are similar in basicity to alkylamines. Interestingly, the heterocyclic amine having a nitrogen atom as part of an aromatic ring has much less basicity than its corresponding alicyclic counterpart. For this reason, as presented in Figure 1, piperidine (pKb = 2.8) is significantly more basic than pyridine (pKb = 8.8).
02:42Valence Bond Theory
Coordination compounds and complexes exhibit different colors, geometries, and magnetic behavior, depending on the metal atom/ion and ligands from which they are composed. In an attempt to explain the bonding and structure of coordination complexes, Linus Pauling proposed the valence bond theory, or VBT, using the concepts of hybridization and the overlapping of the atomic orbitals. According to VBT, the central metal atom or ion (Lewis acid) hybridizes to provide empty orbitals of suitable...
04:01VSEPR Theory and the Effect of Lone Pairs
Effect of Lone Pairs of Electrons on Molecule Geometry
02:46Crystal Field Theory - Tetrahedral and Square Planar Complexes
Tetrahedral Complexes
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than the dxy,...
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than the dxy,...
01:18Aromatic Hydrocarbon Cations: Structural Overview
Cycloheptatriene is a neutral monocyclic unsaturated hydrocarbon that consists of an odd number of carbon atoms and an intervening sp3 carbon in the ring. The three double bonds in the ring correspond to 6 π electrons, which is a Huckel number, and therefore satisfies the criteria of 4n + 2 π electrons. However, the intervening sp3 carbon disrupts the continuous overlap of p orbitals. As a result, cycloheptatriene is not aromatic.
Removing one hydrogen from the intervening CH2 group with both...
Removing one hydrogen from the intervening CH2 group with both...
01:18Structure of Benzene: Molecular Orbital Model
According to the molecular orbital (MO) model, benzene has a planar structure with a regular hexagon of six sp2 hybridized carbons. As shown in Figure 1, each carbon is bonded to three other atoms with C–C–C and H–C–C bond angles of 120°. The C–H bond length is 109 pm, and the C–C bond length is 139 pm which is midway between the single bond length of sp3 hybridized carbons (154 pm) and sp2 hybridized carbons (133 pm).