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Blood
constitutes about 8% of the human body weight of a healthy individual.
Plasma
The fluid portion of the blood.
Red Blood Cells
Also known as erythrocytes. Their life span in humans is approximately 3–4 months.
Red Blood Cells
They do not have nuclei, and therefore lack nuclear DNA.
hemoglobin
proteins that are responsible for the transportation of oxygen.
Ferroprotoporphyrin
A heme molecule.
White Blood Cells
Also called leucocytes. They are involved in defending the body against infection. They have nuclei and thus represent the main sources of nuclear DNA from the blood.
Platelets
Also known as thrombocytes. Like erythrocytes, they lack nuclei.
Platelets
They play a role in blood clotting. They aggregate at sites of vascular and blood vessel injury.
Presumptive blood assays
are designed to detect traces of blood.
Oxidation–Reduction Reactions
These involves a change in the oxidation state of a molecule.
Oxidants
Chemicals that can be reduced and gain electrons from other molecules.
Reductants
Chemicals that can be oxidized and therefore lose electrons to other molecules.
Phenolphthalin Assay
It presents the results of a reaction in which phenolphthalin, a colorless compound, is catalyzed by heme with hydrogen peroxide as the oxidant.
Phenolphthalein
A member of a class of indicators and dyes, is used in titrations of mineral and organic acids as well as most alkalis.
Benzidine
Used a presumptive assay for the presence of blood after the discovery that the oxidation of benzidine can be catalyzed by heme to produce a blue to dark blue color.
Orthotolidine
A dimethyl derivative of benzidine. Its oxidation reaction can be catalyzed by heme to produce a blue color reaction under acidic conditions
Tetramethylbenzidine (TMB)
A tetramethyl derivative of benzidine. Its oxidation can be catalyzed by heme to produce a green to blue-green color under acidic conditions.
Hemastix® assay kit
TMB-based assay that utilizes a TMB-containing strip device.
chemiluminescence assay
In the ________, light is emitted as a product of a chemical reaction.
Fluorescence Assay
requires the exposure of an oxidized product, such as fluorescin, to a particular wavelength of an excitation light source.
Luminol
It is usually utilized as a chemiluminescent reagent.
Fluorescin
It is used to test for the presence of bloodstains at a crime scene.
Oxidants
Chemicals that are strong oxidants may cause a false-positive reaction.
Plant Peroxidases
It may catalyze oxidation reactions and lead to false-positive results.
Reductants
A false-negative result can occur when a strong reductant is present in a sample.
Microcrystal assays
apply chemicals to treat bloodstains, forming crystals of heme molecules.
Hemochromagens
are heme derivatives in which the ferrous iron of the heme forms two bonds with nitrogenous bases.
Takayama Crystal Assay
A bloodstain is treated with pyridine and glucoseunder alkaline conditions to form crystals of pyridine ferroprotoporphyrin.
Hematin Crystal Assay
Also known as the Teichmann crystal assay.
Hematin
A heme derivative; its iron is in the ferric state.
Chromatographic and Electrophoretic Methods
can identify hemoglobin by its mobility characteristics.
Spectrophotometric methods
_________ for identifying hemoglobin are based on measurements of the characteristic light spectra, with a peak absorbance at 400–425 nm, absorbed by hemoglobin and its derivatives.
Immunological methods
utilize antihuman hemoglobin antibodies. This antibody can be used to detect human hemoglobin and thus indicate the presence of human blood.
RNA-based assays
These assays are based on the fact that certain genes are specifically expressed in certain cell types.
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