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  • Labeling with SNAP-tag® Technology Troubleshooting Guide

    Problem Possible Cause Solution
    Cellular Labeling No labeling Fusion protein
    not expressed
    1. Verify transfection
    2. Check expression of fusion protein via Western blot or SDS-PAGE with Vista Green label
    Weak labeling Poor expression and/or
    insufficient exposure of
    fusion protein to substrate
    1. Increase substrate concentration
    2. Increase incubation time
    Rapid turnover of fusion protein
    1. Analyze samples immediately or fix cells directly after labeling
    2. Label at lower temperature (4°C or 16°C)
    High background Non-specific binding of
    1. Reduce substrate concentration and/or incubation time
    2. Allow final wash step to proceed for up to 2 hours
    3. Include fetal calf serum or BSA during labeling
    Signal strongly reduced after short time Instability of
    fusion protein
    1. Fix cells
    2. Switch tag from N-terminus to C-terminus or vice versa
    1. Add commercially available anti-fade reagent
    2. Reduce illumination time and/or intensity
    Labeling in Solution Precipitation Insoluble fusion
    1. Test from pH 5.0 to 10.0
    2. Optimize salt concentration [50 to 250 mM]
    3. Add 0.05 to 0.1% Tween 20
    Weak or no labeling Exhaustive labeling has not been achieved
    1. Increase incubation time to 2 hrs at 25°C or 24 hrs at 4°C
    2. Reduce the volume of protein solution labeled
    3. Check expression of fusion protein via SDS-PAGE with Vista Green label
    Loss of activity Instability of
    fusion protein
    1. Reduce labeling time
    2. Decrease labeling temperature (4°C or 16°C)