オクタカルシウムリン酸塩のヒドロキシアパタイトへの変容の固体状態のNMR研究:中央のダークライン形成のためのメカニズムモデル
Yao-Hung Tseng1, Chung-Yuan Mou, Jerry C C Chan
1Department of Chemistry and the Center of Condensed Matter, National Taiwan University, No. 1, Section 4 Roosevelt Road, Taipei, Taiwan.
Journal of the American Chemical Society
|May 25, 2006
まとめ
オクタカルシウムフォスファート (OCP) は,生物学的アパタイト形成を模倣して,ヒドロキシアパタイト (HAp) にインビトロで変形します. NMR光譜を用いて研究されたこの変換は,骨と歯の構造を理解するために極めて重要な上位軸のメカニズムを明らかにします.
科学分野:
- 材料科学 材料科学とは
- バイオミネラライゼーション
- 固体化学 固体化学
背景:
- オクタカルシウムリン酸 (OCP) は,骨と歯の生物学的アパタイトの前駆体として長い間理論化されてきました.
- OCPからヒドロキシアパタイト (HAp) への変換を理解することは,バイオマテリアルとバイオミネラライゼーションの研究の鍵です.
研究 の 目的:
- OCPからHApへの変換の分子メカニズムをin vitroで解明する.
- この生物鉱物化の過程におけるpHと水解の役割を調査する.
主な方法:
- 固体 31P ホモ核二重量子 (DQ) NMRスペクトロスコーピー.
- スキャン電子顕微鏡 (SEM) と伝送電子顕微鏡 (TEM).
- 粉末X線微分法 (PXRD) 粉末X線微分法.
主要な成果:
- OCP結晶は,pHが4.35から6.69に上昇すると,六角棒状のHAp結晶に変身します.
- トランスフォーメーションは,OCPとHApの間の特定の格子軸の並べ替えで,トポアキアルである.
- OCPの水分層への水解と水分子の組み込みが,その変化の原動力となっている.
結論:
- この研究は,OCPからHApへの変換メカニズムに関する分子洞察を提供します.
- この発見は,格子不一致による生物学的硬組織における中央の暗線の形成を説明するものである.
- 提案された水解反応は,OCPからHApへの変換中にイオンデプロトネーションを明確にします.
関連する概念動画
01:13¹H NMR: Complex Splitting
A proton M that is coupled to a proton X results in doublet signals for M. However, NMR-active nuclei can be simultaneously coupled to more than one nonequivalent nucleus. When M is coupled to a second proton A, such as in styrene oxide, each peak in the doublet is split into another doublet.
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied first.
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied first.
00:52¹H NMR of Conformationally Flexible Molecules: Temporal Resolution
At room temperature, the chair conformer of cyclohexane undergoes rapid ring flipping between two equivalent chair conformers at a rate of approximately 105 times per second. These two chair conformers are in equilibrium. The rapid ring flipping results in the interconversion of the axial proton to an equatorial proton and an equatorial to the axial proton. Such interconversions are too rapid and cannot be detected on the NMR timescale. Hence, the NMR spectrometer cannot distinguish between the...
01:28Structures of Carboxylic Acid Derivatives
Structure of Carboxylic Acid Derivatives
Carboxylic acid derivatives contain an acyl group attached to a heteroatom such as chlorine, oxygen, or nitrogen. The carbonyl carbon and oxygen are both sp2-hybridized with an unhybridized p orbital.
The three sp2 orbitals of the carbonyl carbon form three σ bonds, one each with the carbonyl oxygen, the α carbon, and the heteroatom, whereas the other two sp2 orbitals of the carbonyl oxygen are occupied by the lone pairs. Further, the unhybridized p...
Carboxylic acid derivatives contain an acyl group attached to a heteroatom such as chlorine, oxygen, or nitrogen. The carbonyl carbon and oxygen are both sp2-hybridized with an unhybridized p orbital.
The three sp2 orbitals of the carbonyl carbon form three σ bonds, one each with the carbonyl oxygen, the α carbon, and the heteroatom, whereas the other two sp2 orbitals of the carbonyl oxygen are occupied by the lone pairs. Further, the unhybridized p...
01:15NMR Spectroscopy: Chemical Shift Overview
The position of the absorption signal of a sample is reported relative to the position of the signal of tetramethylsilane (TMS), which is added as an internal reference while recording spectra. The difference between the absorption frequencies of the sample and TMS (in Hz) is divided by the spectrometer operating frequency (in MHz) to obtain a dimensionless quantity called the chemical shift. It is reported on the δ (delta) scale and expressed in parts per million.
For instance, the proton...
For instance, the proton...
01:08NMR Spectroscopy: Spin–Spin Coupling
The spin state of an NMR-active nucleus can have a slight effect on its immediate electronic environment. This effect propagates through the intervening bonds and affects the electronic environments of NMR-active nuclei up to three bonds away; occasionally, even farther. This phenomenon is called spin–spin coupling or J-coupling. Coupling interactions are mutual and result in small changes in the absorption frequencies of both nuclei involved. While nuclei of the same element are involved in...
01:19NMR Spectroscopy Of Amines
In proton NMR spectroscopy, primary amines and secondary amines showcase their N–H protons as a broad signal in the chemical shift range between δ 0.5 and 5 ppm. The exact position in this range depends on several factors, including sample concentration, hydrogen bonding, and the type of solvent used. Since amine protons undergo fast proton exchange in solution, the protons are labile and therefore do not participate in any splitting with adjacent protons. Thus, the observed peak is broad and...