Haemochromogen
Definition
A reduced haem-nitrogenous-base complex. In the Takayama test, pyridine is the base, giving pyridine haemochromogen: pink, feathery or needle-like crystals.
- Definition
- Reduced haem-nitrogenous-base complex
- Takayama base
- Pyridine
- Product name
- Pyridine haemochromogen
- Crystal appearance
- Pink, feathery or needle-like crystals
Common questions
How does the Takayama test's haemochromogen differ from the Teichmann test's haemin?+
Both tests form a haem-based crystal used to confirm blood, but Teichmann produces an oxidised chlorohemin crystal using a halide salt, while Takayama produces a reduced pyridine haemochromogen crystal using pyridine and a reducing sugar, giving the two tests different crystal shapes and colours to examine microscopically.
Why is a reducing agent needed to form pyridine haemochromogen?+
The haem iron must be in a reduced state to bind pyridine and form the haemochromogen complex, so the Takayama reagent includes a reducing sugar such as glucose alongside pyridine and sodium hydroxide to drive the haem into the correct oxidation state for crystal formation.
Related terms
- Confirmatory Test
- A test with sufficient specificity to establish the identity of a biological fluid for reporting purposes. Examples include Takayama and Teichmann crystal...
- Glacial Acetic Acid
- Concentrated acetic acid (near 100%), used in the Teichmann reagent to provide an acidic medium that helps oxidise haem and incorporate the...
- Haemin (Chlorohemin)
- The oxidised, halide-salt form of haem produced in the Teichmann test. Haemin crystals are brown, rhomboid, and form in pairs or groups...
- Pyridine
- An aromatic nitrogen heterocycle used as a secondary denaturant in Indian denatured spirit formulations (at 1-2% v/v). Its presence in a headspace...
- Sensitivity Limit
- The minimum amount of blood (or age/dilution of stain) at which the crystal test can still produce identifiable crystals. Below this threshold...