Evaluación de la existencia de enlaces axiales Co(II) -N hiperlargos en modelos de cobinamida B(12) mediante el uso de espectroscopia de resonancia paramagnética de electrones
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Structure and Coordination Determination of Peptide-metal Complexes Using 1D and 2D 1H NMR
Published on: December 16, 2013
J S Trommel1, K Warncke, L G Marzilli
1Department of Physics, Emory University, Atlanta, Georgia 30322, USA.
Journal of the American Chemical Society
|July 18, 2001
Resumen
Este estudio resuelve las discrepancias entre la espectroscopia EPR y la teoría con respecto a la vitamina B12.
Área de la Ciencia:
- La bioquímica es la bioquímica.
- Química bioorgánica Química bioorgánica.
Sus antecedentes:
- Se propone el control proteico de la longitud del enlace de ligando de nitrógeno cobalto-axial en la coenzima de vitamina B12 para modular la reactividad.
- Los enlaces Co-N hiperlargos pueden facilitar la escisión homolítica del enlace trans-cobalto-carbono.
Objetivo del estudio:
- Para aclarar los hallazgos cristalográficos de rayos X en los enlaces Co-N hiperlargos en las holoenzimas B12 utilizando espectroscopia EPR.
- Resolver el aparente conflicto entre la teoría EPR y los resultados experimentales relativos a los aductos de cobinamida Co (II).
Principales métodos:
- Estudiado Co(II) cobinamida (Co(II)Cbi(+)) aductos con piridinas 4-sustituidas sin trabas en el etilenoglicol.
- Utilizó una nueva destilación de Co (III) afinidad para purificar la 2-picolina y eliminar las impurezas de ligando.
- Se ha investigado la selectividad de unión de Co(II)Cbi(+) con varias piridinas sustituidas.
Principales resultados:
- Se encontró un aumento lineal en la división hiperfina de Co ((II) con disminución de la basicidad de piridina 4-sustituida, consistente con la teoría.
- Se demostró que la 2-picolina purificada no forma aductos con Co(II)Cbi(+), refutando hallazgos anteriores.
- Identificó el obstáculo estérico del anillo de corrina como un factor clave en la unión selectiva Co(II) Cbi(+).
Conclusiones:
- Se resuelve el aparente conflicto entre el experimento EPR y la teoría.
- Es probable que los enlaces axiales Co-N en los cofactores de vitamina B12 ligados a las enzimas no sean hiperlargos.
- Co(II)Cbi(+) actúa como un agente de unión selectivo para los ligandos donantes de nitrógeno sin obstáculos.
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