Hydroxyapatite
Definition
The calcium phosphate mineral (Ca10(PO4)6(OH)2) that constitutes approximately 70 percent of bone dry weight. Its crystals bind to DNA fragments electrostatically, slowing enzymatic degradation. The mineral phase is more stable than the organic phase and persists for geological timescales in favourable burial conditions.
- Formula
- Ca10(PO4)6(OH)2
- Proportion of bone
- Approximately 70 percent of dry bone weight
- DNA interaction
- Binds DNA fragments electrostatically, slowing enzymatic breakdown
- Relative stability
- More stable than bone's organic (collagen) phase over time
Common questions
Why does hydroxyapatite matter for DNA recovery from old skeletal remains?+
Because the mineral surface adsorbs DNA fragments and shields them from nucleases and microbial degradation, extraction protocols for degraded bone often use demineralization steps specifically to release this protected DNA before amplification.
Does hydroxyapatite content vary between bone types or with age?+
Mineral density increases somewhat with skeletal maturity and varies by bone type and anatomical site, which is one reason dense cortical bone such as the femoral shaft is often preferred over more porous trabecular bone for DNA sampling.
Related terms
- Cortical Bone
- The dense outer shell of long bones, also called compact bone. Porosity is less than 10 percent. High mineral density, slow water...
- Inhibitor Removal
- Laboratory steps applied to degraded bone before PCR amplification. Collagen hydrolysis products, humic acids, and heavy metals in aged bone inhibit DNA...
- Osteon (Haversian System)
- The basic structural unit of compact cortical bone: a central Haversian canal surrounded by concentric lamellae of mineralised collagen. Osteon diameter and...
- Stable Isotope Analysis
- A technique that measures the ratio of stable (non-radioactive) isotopes of elements such as strontium, oxygen, and carbon in a biological sample....
- Trabecular Bone
- The spongy inner lattice of bone, found at epiphyses and in flat bones. Porosity of 50 to 90 percent allows rapid water...