Poor Detection of Small Molecular Weight Proteins

Symptom

Proteins smaller than 15-20 kDa show weak or absent signal while larger proteins detect normally. Small protein bands are masked or obscured.

1. 1 Large blocking molecules like BSA (66 kDa) mask small protein epitopes
2. 2 Excessive surfactant (Tween, Triton X-100) concentration strips small proteins
3. 3 Prolonged antibody or wash incubation times cause small protein loss
4. 4 High molecular weight blocking agents sterically hinder antibody access

1. 1 Switch to low molecular weight blocking agent: casein, polyvinylpyrrolidone (PVP), or protein-free blocker
2. 2 Minimize surfactant concentration: reduce Tween-20 to <0.05% or eliminate Triton X-100
3. 3 Reduce antibody and wash incubation times to minimum effective duration
4. 4 Avoid excessive blocking reagent concentration and prolonged blocking times