Que es un control scrambled peptide?

Peptido con misma composicion de aminoacidos pero secuencia aleatorizada. Usado como control para verificar que la interaccion es especifica de secuencia, no de propiedades fisicoquimicas generales. No debe mostrar binding.

Como funciona SPR para medir interacciones?

Surface plasmon resonance detecta cambios en indice de refraccion cerca de una superficie metalica cuando moleculas se unen o disocian. Permite medir cinetica en tiempo real: Kon (asociacion), Koff (disociacion) y calcular KD = Koff/Kon.

Que son los dominios SH2, SH3 y PDZ?

Dominios modulares que reconocen secuencias peptidicas especificas. SH2 une fosfotirosina, SH3 une proline-rich motifs, PDZ une C-terminal motifs. Son modulos de reconocimiento en proteinas de senalizacion.

Por que cross-linking captura interacciones transitorias?

El cross-linker forma enlaces covalentes entre moleculas que estan interactuando en el momento de la reaccion. Aunque la interaccion sea debil o transitoria, el enlace covalente la congela, permitiendo deteccion posterior.

Interactoma de Peptidos y Proteinas

Categorías: Metodología de Investigación, Información General

Las interacciones peptido-proteina son fundamentales para la biologia celular. Mapearlas es esencial para entender mecanismos y desarrollar terapias.

Resumen Simplificado

Co-IP, pull-down, cross-linking MS y arrays de peptidos mapean interacciones moleculares.

Principios de interaccion

Interacciones son especificas. Fuerzas involucradas. Hidrofobas. Core de union. Exclusion de agua. Electrostaticas. Carga complementaria. Salt bridges. Hydrogen bonds. Specificity. Orientation. Van der Waals. Surface complementarity. Shape matching. Afinidad. Kd. Dissociation constant. nM alta afinidad. mM baja afinidad. Terapeutico. nM-uM range typically. Kinetics. Association rate. Kon. Dissociation rate. Koff. Residence time. 1/Koff. May matter more than affinity. Allosteric effects. Binding at one site. Affects another. Regulation. Cooperativity. Positive. Negative. Multi-valency. Multiple binding sites. Avidity. Combined strength. Functional consequences. Activation. Inhibition. Localization. Degradation. Interaccion es equilibrio. Dinamica y especifica.

Co-inmunoprecipitacion

Co-IP es metodo clasico. Principle. Antibody against bait. Capture bait protein. Interactors co-precipitate. Through binding. Procedure. Lyse cells. Gentle conditions. Preserve interactions. Incubate with antibody. Capture complex. Wash. Remove non-specific. Elute. Analyze interactors. Bead selection. Protein A/G. Magnetic beads. Agarose. Washing stringency. Balance. Too harsh. Lose interactors. Too gentle. Non-specific binding. Controls. IgG control. Non-specific pull-down. Bait-only control. Identify background. Analysis. Western blot. Known interactors. Mass spectrometry. Discovery. Unbiased. Limitations. Transient interactions. May be lost. False positives. Abundant proteins. Sticky proteins. Keratins. Co-IP is starting point. Validation needed.

Peptido pull-down

Pull-down usa peptidos immobilizados. Principle. Bait peptide on solid support. Capture binding proteins. From lysate or solution. Immobilization. Biotin-streptavidin. Most common. Biotinylated peptide. Streptavidin beads. High affinity. NHS-activated beads. Direct coupling. Covalent. His-tag binding. Ni-NTA beads. Via tag. Considerations. Orientation. N-terminal vs C-terminal coupling. Accessible binding site. Linker length. Spacer needed. Avoid steric hindrance. Density. Too high. Self-competition. Too low. Weak signal. Controls. Scrambled peptide. Same composition. Wrong sequence. Unrelated peptide. Same tag. No peptide. Beads only. Analysis. Western. Specific proteins. MS. Discovery mode. Pull-down is versatile. Works for peptides specifically.

Cross-linking mass spectrometry

XL-MS captura interacciones transitorias. Principle. Cross-linker added. Covalent link formed. Between interacting molecules. Capture transient. Map interaction interface. Cross-linkers. BS3. Amine-reactive. DSS. Similar. Homobifunctional. DSSO. MS-cleavable. Facilitate analysis. Sulfo-SMCC. Amine-sulfhydryl. Heterobifunctional. Zero-length. EDC. Direct bond. Workflow. Cross-link in vivo. Or in vitro. Quench reaction. Digest. Cross-linked peptides. Enrich. MS analysis. Identify linked residues. Data analysis. Complex. Specialized software. XlinkX. pLink. MeroX. Identify cross-linked pairs. Map distance constraints. Structural modeling. Integrative. Combine with other data. XL-MS is powerful. Structural insights. Interaction interfaces.

Arrays de peptidos

Peptide arrays son high-throughput. Principle. Many peptides on surface. Screen many interactions. Simultaneously. Types. SPOT synthesis. Cellulose membrane. Spot by spot. In situ synthesis. Commercial arrays. Pre-made. Custom options. Glass slides. High density. Applications. Binding specificity. Screen many variants. Epitope mapping. Antibody specificity. Domain-peptide interactions. SH2, SH3, PDZ domains. Kinase substrates. Motif recognition. Readout. Fluorescence. Labeled protein. Colorimetric. Radioactive. Older methods. Advantages. High throughput. Many sequences. Low sample. Limitations. Surface effects. Non-physiological. False positives. False negatives. Density limitations. Data analysis. Quantification. Comparison. Statistical validation. Arrays are screening. Follow-up required.

Validacion de interacciones

Interacciones deben validarse. Orthogonal methods. Different principle. Confirm binding. Biophysical methods. SPR. Surface plasmon resonance. Real-time kinetics. Kon, Koff, KD. ITC. Isothermal titration calorimetry. Thermodynamics. Delta H, Delta S. MST. Microscale thermophoresis. Solution-based. Label or label-free. BLI. Bio-layer interferometry. Similar to SPR. Fluorescence polarization. Size-based. Binding increases size. Polarization change. Cellular validation. FRET. Fluorescence resonance. Two labeled proteins. Proximity detection. BRET. Bioluminescence. No excitation needed. Proximity ligation assay. In situ detection. Fluorescence spots. Co-localization. Confocal microscopy. Overlap. Not proof of direct binding. Functional assays. Effect of interaction. Mutants that disrupt. Loss of function. Validation is essential. Each method has limitations.

Hallazgos Clave

Las interacciones peptido-proteina involucran fuerzas hidrofobas, electrostaticas y H-bonds
Co-IP captura complejos con anticuerpos pero puede perder interacciones transitorias
El pull-down con peptidos biotinilados identifica proteinas que unen secuencias especificas
XL-MS usa cross-linkers covalentes para mapear interfaces de interaccion
Los arrays de peptidos permiten screening de alta densidad de especificidad
La validacion requiere metodos ortogonales como SPR, ITC y ensayos celulares

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Preguntas frecuentes

Que es un control scrambled peptide?: Peptido con misma composicion de aminoacidos pero secuencia aleatorizada. Usado como control para verificar que la interaccion es especifica de secuencia, no de propiedades fisicoquimicas generales. No debe mostrar binding.
Como funciona SPR para medir interacciones?: Surface plasmon resonance detecta cambios en indice de refraccion cerca de una superficie metalica cuando moleculas se unen o disocian. Permite medir cinetica en tiempo real: Kon (asociacion), Koff (disociacion) y calcular KD = Koff/Kon.
Que son los dominios SH2, SH3 y PDZ?: Dominios modulares que reconocen secuencias peptidicas especificas. SH2 une fosfotirosina, SH3 une proline-rich motifs, PDZ une C-terminal motifs. Son modulos de reconocimiento en proteinas de senalizacion.
Por que cross-linking captura interacciones transitorias?: El cross-linker forma enlaces covalentes entre moleculas que estan interactuando en el momento de la reaccion. Aunque la interaccion sea debil o transitoria, el enlace covalente la congela, permitiendo deteccion posterior.

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