Video Experimental Relacionado
Updated: Jun 25, 2026
10:03
Proton Transfer and Protein Conformation Dynamics in Photosensitive Proteins by Time-resolved Step-scan Fourier-transform Infrared Spectroscopy
Published on: June 27, 2014
Espectroscopia de infrarrojos en fase gaseosa de aminoácidos desprotonados
Jos Oomens1, Jeffrey D Steill, Britta Redlich
1FOM Institute for Plasma Physics Rijnhuizen, Edisonbaan 14, 3439MN Nieuwegein, The Netherlands. joso@rijnhuizen.nl
Journal of the American Chemical Society
|March 10, 2009
Resumen
La espectroscopia infrarroja en fase gaseosa revela que los aniones de aminoácidos existen predominantemente como carboxilatos. La ampliación en los espectros de aspartato y glutamato sugiere un puente de protones entre la columna vertebral y los carboxilatos de la cadena lateral.
Área de la Ciencia:
- Química Física es la química física.
- La espectroscopia es una técnica de espectroscopia.
- Química computacional es la química computacional.
Sus antecedentes:
- Los aminoácidos son moléculas biológicas fundamentales.
- Comprender los estados de desprotonación de los aminoácidos es crucial para estudiar sus propiedades químicas y funciones biológicas.
- Estudios anteriores han propuesto diferentes estructuras para los aminoácidos desprotonados.
Objetivo del estudio:
- Para investigar las estructuras de la fase gaseosa de los aminoácidos desprotonados utilizando la espectroscopia de disociación de fotones múltiples por infrarrojos (IRMPD).
- Para comparar los hallazgos experimentales con los cálculos de la teoría funcional de densidad (DFT).
- Para aclarar las diferencias estructurales entre varios aniones de aminoácidos.
Principales métodos:
- Se empleó espectroscopia de disociación múltiple de fotones infrarrojos (IRMPD) de fase gaseosa para registrar espectros de aminoácidos desprotonados.
- Se registraron espectros infrarrojos para las bases conjugadas de Asp, Cys, Glu, Phe, Ser, Trp y Tyr.
- Los espectros experimentales se compararon con los cálculos a nivel de DFT.
Principales resultados:
- Los espectros IRMPD de la mayoría de los aniones de aminoácidos investigados exhibieron fuertes modos de estiramiento del carboxilato, lo que indica una estructura de carboxilato.
- La base conjugada de la tirosina fue identificada inequívocamente como un carboxilato, no un fenóxido.
- Los aniones de aspartato y glutamato mostraron características espectrales amplias y no resueltas, lo que sugiere un puente de protones entre los carboxilatos de la cadena vertebral y la cadena lateral.
Conclusiones:
- El estudio confirma una estructura carboxilata para las bases conjugadas de la mayoría de los aminoácidos investigados.
- La ampliación espectral observada en el aspartato y el glutamato se atribuye al puenteamiento de protones, lo que lleva a una amplia ampliación espectral debido al movimiento de protones de gran amplitud.
- Estos hallazgos proporcionan información sobre la diversidad estructural y la dinámica vibratoria de los aniones de aminoácidos en la fase gaseosa.
Videos de Conceptos Relacionados
01:19NMR Spectroscopy Of Amines
In proton NMR spectroscopy, primary amines and secondary amines showcase their N–H protons as a broad signal in the chemical shift range between δ 0.5 and 5 ppm. The exact position in this range depends on several factors, including sample concentration, hydrogen bonding, and the type of solvent used. Since amine protons undergo fast proton exchange in solution, the protons are labile and therefore do not participate in any splitting with adjacent protons. Thus, the observed peak is broad and...
01:15Mass Spectrometry of Amines
In mass spectroscopy, amines undergo fragmentation to give parent ions with odd molecule weights. This observed mass spectrum follows the nitrogen rule; a molecule with an odd number of nitrogen atoms produces a molecular ion with an odd molecular weight. Amines undergo fragmentation through α cleavage, producing nitrogen-containing cations—iminium ions—and alkyl radicals. Mass spectra of aromatic and cyclic aliphatic amines exhibit strong molecular ion peaks, but acyclic aliphatic amines show...
01:26Spectroscopy of Carboxylic Acid Derivatives
Infrared spectroscopy is primarily used to determine the types of bonds and functional groups. In carboxylic acid derivatives, a typical carbonyl bond absorption is observed around 1650–1850 cm−1. For esters, the absorption is recorded at around 1740 cm−1, while acid halides show the absorption at about 1800 cm−1. Another acid derivative, the acid anhydrides, exhibit two carbonyl absorption around 1760 cm−1 and 1820 cm−1, arising from the symmetrical and unsymmetrical carbonyl vibration.
In the...
In the...
01:20¹³C NMR: Distortionless Enhancement by Polarization Transfer (DEPT)
When proton-coupled carbon-13 spectra are simplified by a broadband proton decoupling technique, structural information about the coupled protons is lost. Distortionless enhancement by polarization transfer (DEPT) is a technique that provides information on the number of hydrogens attached to each carbon in a molecule. While the DEPT experiment utilizes complex pulse sequences, the pulse delay and flip angle are specifically manipulated. The resulting signals have different phases depending on...
01:30NMR and Mass Spectroscopy of Carboxylic Acids
In ¹H NMR spectroscopy, acidic protons (–COOH) of carboxylic acids are highly deshielded and absorb far downfield, at around 9–12 ppm. The chemical shift value depends on the concentration and solvent used.
While α protons of carboxylic acids absorb at 2–2.5 ppm, β protons absorb further upfield.
Carboxylic acids are easily identified by dissolving them in deuterium oxide, which results in a rapid exchange of the acidic protons with deuterium. This leads to the disappearance of the acidic...
While α protons of carboxylic acids absorb at 2–2.5 ppm, β protons absorb further upfield.
Carboxylic acids are easily identified by dissolving them in deuterium oxide, which results in a rapid exchange of the acidic protons with deuterium. This leads to the disappearance of the acidic...
01:08IR Spectrum Peak Splitting: Symmetric vs Asymmetric Vibrations
Identical bonds within a polyatomic group can stretch symmetrically (in-phase) or asymmetrically (out-of-phase). Similar to hydrogen bonding, these vibrations also influence the shape of the IR peak. Generally, asymmetric stretching frequencies are higher than symmetric stretching frequencies. For example, primary amines exhibit two distinct IR peaks between 3300–3500 cm−1 corresponding to the symmetric and asymmetric N-H stretching, while secondary amines exhibit a single stretching vibration...