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Mediciones electrostáticas dirigidas al sitio con un nitróxido sensible al ph específico del tiol: diferenciando los

Alex I Smirnov¹, Andres Ruuge, Vladimir A Reznikov

¹Department of Chemistry, North Carolina State University, 2620 Yarbrough Drive, Raleigh, North Carolina 27695-8204, USA. alex_smirnov@ncsu.edu

Journal of the American Chemical Society

|July 22, 2004

Resumen

Este estudio introduce el éster (IMTSL) de ácido metanetiosulfónico S-(1-oxil-2,2,3,5,5-pentametil-imidazolidina-4-ilmetil) para la determinación precisa del péptido pKa mediante la resonancia paramagnética de electrones (EPR). IMTSL permite mediciones de pKa dirigidas al sitio mediante el monitoreo de los cambios de protonación a través de espectros EPR.

Área de la Ciencia:

Química biofísica y bioquímica.
Biología Química Biología química.
La espectroscopia es una técnica de espectroscopia.

Sus antecedentes:

La determinación de pKa dirigida al sitio es crucial para comprender la función de los péptidos y las proteínas.
La resonancia paramagnética de electrones (EPR) ofrece un método sensible para sondear entornos moleculares.
Los métodos existentes para la determinación de pKa pueden carecer de especificidad del sitio o requerir estrategias de etiquetado específicas.

Objetivo del estudio:

Introducir y validar una nueva etiqueta de espín, IMTSL, para la determinación de pKa de péptidos dirigida en el sitio.
Establecer un método para diferenciar los efectos de polaridad local de los eventos de protonación utilizando EPR.
Para demostrar la utilidad de IMTSL en un sistema de péptidos biológicamente relevantes.

Principales métodos:

Adhesión covalente del derivado del metanetiosulfonato (IMTSL) a los residuos de cisteína en los péptidos.
Utilizando la espectroscopia EPR de banda W (95 GHz) para monitorear cambios en los parámetros magnéticos isotrópicos del nitróxido (Aiso y giso).
Calibración de parámetros EPR en disolventes de polaridad y pH variables para establecer correlaciones.

Principales resultados:

Se observaron dos correlaciones lineales distintas entre Aiso y giso para las formas ácida y básica de IMTSL.
Estas correlaciones permiten la separación de las influencias de polaridad local de los efectos de protonación N3 en los espectros EPR.
La titulación exitosa de un fragmento de péptido P11 sintético de la cadena laminina B1 demostró la aplicabilidad del método.

Conclusiones:

IMTSL es una etiqueta de espín eficaz para la determinación de pKa dirigida al sitio en péptidos utilizando EPR.
El método permite la desconvolución de los efectos de polaridad y protonación en la etiqueta de giro.
Esta técnica proporciona una herramienta valiosa para estudiar las propiedades ácido-base locales de péptidos y proteínas.

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