first evidence of octacalcium phosphate@osteocalcin nanocomplex as skeletal bone component directing collagen triple–helix nanofibril mineralization - pearl necklace and earring set

by:JINGLIXIN     2019-08-15
first evidence of octacalcium phosphate@osteocalcin nanocomplex as skeletal bone component directing collagen triple–helix nanofibril mineralization  -  pearl necklace and earring set
A human technique of the tibia and spine of the rat studied high
The resolution TEM at the atomic scale to reveal a snapshot of the morphological occurrence process of the formation of local bone superstructures.
By taking into account the reflection of ha for Fourier filtering, the appearance of a single alpha chain in the three helix clearly shows that the bone has a molecular complex that extends from atoms to nanometers, thus representing collagen and phosphate.
A careful Fourier analysis showed that non-collagen bone calcium protein was directly bound to calcium phosphate.
In addition to a single spherical specimen with a diameter of about 2 nm, the bone calcium protein is also distributed between and above the collagen original fibers and is usually observed as a string of pearl necklaces. In high-
Resolution TEM, three binding sites of γ-
The acid amino acid Group of the mineralised bone calcium protein was successfully imaged, which provided chemical binding for calcium phosphate.
Bone calcium protein is attached to the collagen structure and is related (100)
Ha platelets mainly Ca-
Ca is about 9 away. 5u2009Å.
Therefore, bone calcium protein has the function of Ca-ion transport and inhibition of ha expansion.
Since Havers's first report on the structure of the bone, the structural hierarchy of the bone consists mainly of five levels, which have become more refined over the years, extending to seven levels, and now even to nine.
The basic structural unit of type I collagen, consisting of two identical chains and a three-helix chain, is a hard-soluble molecule with a length of about 300nm and 1.
The thickness is 5 nm.
Type I collagen is a two-parent molecule.
In the presence of a two-valent electrolyte (Ca)
, Due to excessive alkaline residues in the amino acid sequence, it is positively charged near neutral pH.
As shown in flourdenberg.
, From pH 7, the electricity point changes with the increase of ion strength in the CaCl solution. More than 5 PH 9.
The bone is composed of mineral collagen containing about 65 weights.
% Phosphate, 25 wt.
% Organic molecules, mainly type I collagen and 10 wt. %water. Non-
Collagen (NCPs)
The amount is about 10-15 wt.
Percentage of organic parts.
NCPs can be divided into five groups.
About 25% of NCPs are Dalton with a molecular weight of 69 kilograms (kD)
, Fetuin precursor α 2-
HS protein 2q11-13.
Therefore, this group contains only two different proteins. Proteoglycans (13 proteins)
The molecular weight is from 59 to several million kD, containing the protein (7 proteins)
Molecular weight from 21 to 1920 kD is the largest group.
The fourth group belongs to cell binding protein (9 members)
From 44 to 450 kD.
Bone nutritional protein (46–75 kD)
This group is an important part of the extracellular matrix of bone cells, accounting for about 8% of all non-extracellular matrix of bone cells.
Collagen found in bone and bone.
Another prominent representative of this group is bone Bridge protein (44–75 kD).
Both of them anchor the macrophages and show a strong Ca binding.
The fifth group belongs to the dimethamine or Gla protein with acidic amino group (
4 members/protein)
Molecular weight from 5-72 kD, bone calcium protein (OC)
Become the most important member of this family.
In addition to type I collagen (85–90 wt. %)
, OC is the second-abundant protein in the mature human bone organic matrix, and plays an important role in the regulation of structure-oriented molecules and bone cells and broken cell activity.
The content of bone calcium protein was from 0. 028 (human)to 0. 2–0. 25 wt. % (bovine)for dry bone.
Most species are clustered at 0. 14–0. 19 wt. % range. OC (
Molecular weight 5. 2–5. 9 kD)
As a calcium binding protein, it is mainly unstructured in aqueous solution, but transformed into a folded state, almost spherical structure with a diameter of about 1. 7–2.
In the presence of the physiological concentration of calcium, 0nm nm.
OC is present on the surface of mineralised collagen fibers.
The study revealed the relationship between bone calcium protein and type I collagen, in which the binding was shown to be reversible.
Bone calcium in collagen fibers was detected in the gap area and part of the adjacent overlapping area.
Therefore, we assume that OC mediated the nuclear and growth of platelet-shaped ha (HAP)crystals.
The crystal structure of the pig OC-Ca complex reveals a negatively charged protein surface that coordinates up to five lithium ions, Three Gla and Asp residues (
Gla _ = γ-acid amino acid obtained from spiral α, asp _ = aspartic gate acid obtained from spiral α).
The single molecule attached to HAP is most suitable for the plane parallel to the axis.
Bone calcium protein is involved in the regulation of mineralization, because observations on bone calcium protein gene knockout mice suggest that bone calcium protein may have a role in limiting bone formation.
Molecular dynamics simulations show the optimal correlation of the distance between uncoordinated Gla-oxygen atoms (COOH groups)
The calcium distance between OC is 9.
43 u2009 Å in hydroxyl apatite crystal structure (rather than 5.
44 proposals made earlier by the company).
Increased availability of binding sites (9.
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