Video Experimental Relacionado
Updated: May 13, 2026
10:31
Residue-Specific Exchange of Proline by Proline Analogs in Fluorescent Proteins: How "Molecular Surgery" of the Backbone Affects Folding and Stability
Published on: February 3, 2022
Propensión a la formación de hélices de los oligómeros alifáticos de urea que incorporan patrones de sustitución de
Nagendar Pendem1, Céline Douat, Paul Claudon
1Université de Bordeaux -CNRS UMR 5248, CBMN, Institut Européen de Chimie et Biologie, 2 rue Robert Escarpit, 33607 Pessac, France.
Journal of the American Chemical Society
|March 1, 2013
Resumen
Las oligoureas alifáticas forman hélices, pero su estructura es sensible a las modificaciones de residuos. Los investigadores exploraron cómo diferentes patrones de sustitución afectan la formación de hélices en estos peptidomiméticos.
Área de la Ciencia:
- Biología Química Biología química.
- Química orgánica es la química orgánica.
- La ciencia de los polímeros es la ciencia de los polímeros.
Sus antecedentes:
- Las oligoureas alifáticas N,N'-enlazadas son foldameros peptido-miméticos.
- Estos foldamers adoptan estructuras secundarias helicoidales bien definidas.
- La estabilidad de la hélice se rige por enlaces de hidrógeno remotos de tres centros que forman pseudoanillos.
Objetivo del estudio:
- Investigar las reglas que rigen la formación de hélices en las oligoureas.
- Para determinar la compatibilidad de los patrones de sustitución alternativos con la geometría de hélice.
- Comprender cómo las variaciones de residuos afectan la estructura helicoidal para posibles aplicaciones funcionales.
Principales métodos:
- Evaluación sistemática de la formación de hélices en los pentámeros modificados de oligourea.
- Análisis del estado de solución utilizando la espectroscopia de infrarrojos de la transformada de Fourier (FTIR), la resonancia magnética nuclear (RMN) y el dicroísmo circular electrónico (DCE).
- Cristalografía de rayos X de alta resolución y cálculos teóricos para racionalizar las preferencias conformacionales.
Principales resultados:
- Tres nuevos patrones de sustitución fueron acomodados dentro de la estructura de 2.5 hélices.
- La columna vertebral de urea helicoidal en oligómeros cortos demostró sensibilidad a los patrones de sustitución de residuos, incluida la posición y la estereoquímica.
- Unidades específicas, como el trans-1,2-diaminociclohexano, interrumpieron la nucleación de hélice, mientras que los isómeros cis no lo hicieron.
Conclusiones:
- La estructura helicoidal de las oligoureas alifáticas es sensible a las modificaciones en la sustitución de residuos y la estereoquímica.
- Comprender estas sensibilidades es crucial para diseñar foldamers funcionales con arreglos controlados de la cadena lateral.
- Los datos teóricos y experimentales proporcionan información sobre las preferencias conformacionales y las limitaciones de estos peptidomiméticos.
Más Videos Relacionados
Videos de Conceptos Relacionados
01:28Structures of Carboxylic Acid Derivatives
Structure of Carboxylic Acid Derivatives
Carboxylic acid derivatives contain an acyl group attached to a heteroatom such as chlorine, oxygen, or nitrogen. The carbonyl carbon and oxygen are both sp2-hybridized with an unhybridized p orbital.
The three sp2 orbitals of the carbonyl carbon form three σ bonds, one each with the carbonyl oxygen, the α carbon, and the heteroatom, whereas the other two sp2 orbitals of the carbonyl oxygen are occupied by the lone pairs. Further, the unhybridized p...
Carboxylic acid derivatives contain an acyl group attached to a heteroatom such as chlorine, oxygen, or nitrogen. The carbonyl carbon and oxygen are both sp2-hybridized with an unhybridized p orbital.
The three sp2 orbitals of the carbonyl carbon form three σ bonds, one each with the carbonyl oxygen, the α carbon, and the heteroatom, whereas the other two sp2 orbitals of the carbonyl oxygen are occupied by the lone pairs. Further, the unhybridized p...
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).
02:38Electrophilic Addition to Alkynes: Halogenation
Introduction
Halogenation is another class of electrophilic addition reactions where a halogen molecule gets added across a π bond. In alkynes, the presence of two π bonds allows for the addition of two equivalents of halogens (bromine or chlorine). The addition of the first halogen molecule forms a trans-dihaloalkene as the major product and the cis isomer as the minor product. Subsequent addition of the second equivalent yields the tetrahalide.
Halogenation is another class of electrophilic addition reactions where a halogen molecule gets added across a π bond. In alkynes, the presence of two π bonds allows for the addition of two equivalents of halogens (bromine or chlorine). The addition of the first halogen molecule forms a trans-dihaloalkene as the major product and the cis isomer as the minor product. Subsequent addition of the second equivalent yields the tetrahalide.
01:18Basicity of Aromatic Amines
The basicity of aromatic amines is much weaker than that of aliphatic amines due to the involvement of the lone pair of electrons over the N atom in resonance with the aryl rings. Generally, the electron-donating ability of any substituents on the aryl ring of aromatic amines increases the basicity of the amine by increasing electron density, and hence the availability of lone pair on the nitrogen. On the other hand, electron-withdrawing functional groups on the aryl ring of amines decrease the...
01:19Structure of Amines
The hybridized nitrogen atom in amines possesses a lone pair of electrons and is bound to three substituents with a bond angle of around 108°, which is less than the tetrahedral angle of 109.5°. However, the C–N–H bond angle is slightly larger at 112°, with a carbon–nitrogen bond length of 147 pm. This carbon–nitrogen bond length of of amines is longer than the carbon–oxygen bond of alcohols (143 pm) but shorter than alkanes’ carbon–carbon bond (154 pm). These aspects are illustrated in Figure...
02:30Stability of Substituted Cyclohexanes
This lesson discusses the stability of substituted cyclohexanes with a focus on energies of various conformers and the effect of 1,3-diaxial interactions.
The two chair conformations of cyclohexanes undergo rapid interconversion at room temperature. Both forms have identical energies and stabilities, each comprising equal amounts of the equilibrium mixture. Replacing a hydrogen atom with a functional group makes the two conformations energetically non-equivalent.
For example, in...
The two chair conformations of cyclohexanes undergo rapid interconversion at room temperature. Both forms have identical energies and stabilities, each comprising equal amounts of the equilibrium mixture. Replacing a hydrogen atom with a functional group makes the two conformations energetically non-equivalent.
For example, in...