Nonspecific immunocytochemical reactions with certain neurohormonal peptides and basic peptide sequences

Area of Science:

• Immunocytochemistry
• Molecular Biology
• Neuroendocrinology

Background:

• Immunocytochemical staining is widely used to detect peptides in biological samples.
• Nonspecific binding of labeled probes can lead to inaccurate results.
• Basic peptides and poly-L-lysine are common components in biological systems.

Purpose of the Study:

• To investigate the nature and extent of nonspecific binding of labeled reporter molecules to basic neurohormonal peptides and poly-L-lysine.
• To identify conditions and substances involved in this binding.
• To propose necessary control measures for immunocytochemical studies involving basic polypeptides.

Main Methods:

• Immunocytochemical staining experiments on filter paper and nitrocellulose models.
• Testing binding of labeled reporter molecules (IgG, protein A, streptavidin, albumin) to various peptides (ACTH, VIP, opioid peptides) and poly-L-lysine.
• Pre-absorption experiments using excess homologous or heterologous peptides.
• Evaluation of binding under varying salt, pH, and detergent conditions.

Main Results:

• Many basic neurohormonal peptides and poly-L-lysine strongly bind labeled reporter molecules.
• This binding is largely abolished or reduced by pre-absorption with homologous or heterologous basic peptides.
• Nonspecific binding is resistant to high salt, high pH, detergents, and blocking proteins.
• A dynorphin antiserum also showed nonspecific binding, which was blocked by basic peptide pre-absorption.

Conclusions:

• Basic neurohormonal peptides and poly-L-lysine can cause significant nonspecific binding in immunocytochemistry.
• Researchers must exercise caution when interpreting immunocytochemical results for these substances.
• Inclusion of specific control procedures, such as basic peptide pre-absorption, is crucial for accurate detection.