Biomineralisation Flashcards
Biomineralisation
Define biominerlaisation
- refers to the the processes by which organism form minerals
what is biosphere
life on earth
what is lithosphere
solid part of earth
Describe the origin of biominerlisation
- taking place since water appeared on the earth surfaces
- 3.5 Gyr - first prokaryotes and then eukaryotes developed the ability to form biominerals
- 540 Myr ago organism form different phyla evolved the ability to form many of 64 different biominerals known to date
what is biominerlasiation responsible for
- hard, resistant products of life which are mainly responsible for the Earths fossil record
why does biominerlasiton take place?
- provide evolutionary advantages for many organisms
- played an important role in shaping the survival strategies of these organisms
- mechanical support
- digestive processes
- Protection/camouflage
- Defense mechanism
- Attack strategies
- optical advantage
State two basic processes of biominerlation and there other forms of mineraltion
- biologically induces minerlasiiton
- Biologically controlled mineralisation
- extracellular
- intercellular
- intracellular
describe biologically induced mineralisation
- cell is a causative agent only, without control over mineral type or habit
- chemical processes influenced by metabolic activities indirectly form specific minerals
(e.g bacteria such as Thiobacillus ferooxidans can induce the mineralisation of minerals such as iron sulphide on metal surfaces ) - cell surfaces acts as causative agents for nucleation and subsequent mineral growth
- hetrogenetiy is hallmark
- compositions of. minerals vary - morphology, water content, trace, sediment, rock record
Describe biologically controlled mineralisation
- Organism guide mineral formation through cellular activities controlling nucleation, growth,morphology and final location
- Typically occurs in isolated environments
- varies in control across species
describe biological controlled extracellular mineralisation
- cells produce matrix outside the cell
- this matrix is genetically programmed to facilitate mineral formation
(C-HAp crystal formation by ameloblasts)
describe biological controlled intercellular mineralisation
- Typically occurs in single celled organism
- epithelial surfaces of cells directs mineral formation
- mineralisation between cells fill intercellular spaces ( Calcite formation by alcerous algae)
describe biological controlled Intracellular mineralisation
occurs within cells often in specialised vesicles
- some intracellular biominerals remain within cell
- others released by exocytosis or membrane fusion and may undergo secondary assembly
(Silica polymerisation in diatoms)
Define biominerals
Minerals that are produced by the activity of living things
- different properties to their inorganically formed counterparts
- span vast size range
- some organisms can Crete biominerals in seconds
some take thousands of years
how many biominerals are known to date
64
which bxomineral is the most abundant
calcium carbonate
what percentage does iron make up of biominerals
40%
what % does calcium make up of biomienrlas
50%
- preferred cation for majority of organisms
attributed to roles calcium plays in cellular metabolism
what % does hydrated biomaterials make up
60%
- contain water or hydroxyl group
favoured over dehydrated as they educe energy barriers for crystal nucleation and growth form aq
what % makes up crystal/amorphous biominerals
25%
what % make sup phosphates
25%
- carbonated hydroxyapapite - most abundant produced phosphate minerals
present in bones and teeth
- small and unstable
more soluble than HAP
what is the hardest most mienralised tissue in the body
enamel
96% MINERAL
Describe the structure of enamel
- 5 nanometres wide elongated prisms
- cross sections of majority of prisms exhibit a keyhole pattern
- prism houses thousands of needle- like enamel crystals
- hexagonal cross sections
- 60nm in width
30nm in thickness
Describe the conceptual model for protein mediated enamel biominerlaisation
- Ameloblasts develop distal Tomes processes as they move away from the enamel dentine junction
- TP contribute to deposition and shaping of enamel
- Ameloblasts secretes matrix proteins (amelogenin and non amelogenin) as well as mineral forming ions eg. calcium and phosphate
- Amelogenin self assemble into nanospheres stabilising amorphous calcium phosphate (ACP) particles
- Nanospheres could contain non-amelogenesis (enamelin and amelobaslting)
- MMP-20 cleaves amelogenin C terminus promoting self assembly into nanochains for orientated nucleation of calcium phosphate clusters
-ACP clusters fuse into elongated ribbons and transform into crystalline c-HAP - formed mineral crystals mainly grow in length
MMP-20 cleaves amelognein N terminus, promoting nano spheres disassembly - amelogenin and other matrix proteins are further degraded by the serine proteinase KLK-4 allowing further growth of c-HAP
-ameloblasts transition between ruffle and smooth ended states to regulate ion transport, pH and remove organic debris
=c-HAp crsytal grow in thickness and width aided by protein amelotin
describe key methods in studying enamel biominerlasition
- x ray mciroputed tomography
Synchrotron x ray diffraction - SEM
Describe how X-RAY microcomputed tomography is used to study enamel biominerlisation
- as maturation progresses, the bxomineral concentration increases and becomes more uniform
- Gets mineral conc
- biominerlaistion starts near the cusp and the EDJ moving cervically and towards the surface as a function of maturation
Describe how Synchrotron X ray diffraction is used to study dental enamel biomienrlaistion
- pass x ray and study diffraction
orientation persist form early maturation of enamel to new maturation
-crystals orientated approximately perpendicular to EDJ regardless the developmental stage - initial preferred directions of crystals persist form early through to full maturation
Describe how SEM Is used to study dental enamel biominerlaistion
- In fully developed enamel the spasm boundaries were more difficult to distinguish compared to developing enamel
- indicates that mienrlaistion of prisms cores precede that of prisms boundaries
- in devleoped tooth, the mineralisation is homogenous
what does MMP20 do
-cleaves amelogenin C terminus - promoting self assembly into nano chains for orientated nucleation of calcium phosphate clusters
- cleaves amelogensins N terminus- promoting nanpsphers disassembly
what does nanosphers contain
ameolgenin and non amelogenin (enamel and ameloblastin)
what does serine proteases KLK-4 do?
- degrade amelogenin and other matrix proteins allowing further growth of c-HAp
