Related Experiment Video
Updated: May 22, 2026

Concanavalin A-Based Sedimentation Assay to Measure Substrate Binding of Glucan Phosphatases
Published on: December 23, 2022
Comparative determinations of non SHBG-bound serum testosterone, using ammonium sulfate precipitation, Concanavalin A
Frank Giton1, Jérôme Guéchot, Jean Fiet
1AP-HP, Hôpital H. Mondor - A.Chenevier, Pôle Biologie, Centre d'investigation Biologique 006, Créteil 94000, France.
Background:
Testosterone (T) circulates tightly bound to sex hormone-binding globulin (SHBG) and weakly to albumin. Non-SHBG-bound T is considered as the bioavailable T (BT) and was recommended for the evaluation of androgen disorders. Two methods, BT calculating from T, SHBG and albumin or BT measurement using ammonium sulfate precipitation of [SHBG-T] complex have been widely used. Using SHBG separation with Concanavalin-A (ConA) was recently proposed as a more specific method. The aim of this work was to compare these three methods in male patients.
Methods:
Serum samples of 131 consecutive untreated men (15-81 years) referred for suspicion of hypogonadism were collected. Total T was measured by GC-MS, SHBG by immunoradiometric assay. Level of BT was assayed using ammonium sulfate precipitation, ConA separation and calculated using the Issam web calculator.
Results:
Only few differences were found between ammonium sulfate or ConA BT measurements. However, we found much higher serum calculated BT than assayed BT with an increasing bias when BT levels increased.
Conclusions:
Measurement of BT using ConA separation could be recommended. The results are equivalent to those obtained using ammonium sulfate precipitation. This method eliminates the possible non specific albumin precipitation that can occur with ammonium sulfate when the assay conditions are not rigorously controlled.
Related Concept Videos
Protein-Drug Binding: Determination Methods
Indirect methods involve isolating the bound drug from its free form in biological samples such as blood, serum, or plasma. These techniques aim to measure the percentage of drugs bound to proteins. Equilibrium dialysis is a commonly used method where the free drug concentration at equilibrium is measured by separating the bound...
Precipitation Titration: Endpoint Detection Methods
In the Volhard method, a standard excess of AgNO3 is first added to the...
Precipitation Titration: Overview
A precipitation titration curve demonstrates the change in concentration of the titrant or analyte upon adding the...
EDTA: Indirect and Alkalimetric Titration

