ヘリックス・ターン・ヘリックス・モチーフは,ソルバットされていないペプチドに含まれています
David T Kaleta1, Martin F Jarrold
1Department of Chemistry, Indiana University, 800 East Kirkwood Avenue, Bloomington, Indiana 47405, USA.
Journal of the American Chemical Society
|June 12, 2003
まとめ
この研究は,ヘリックス・ターン・ヘリックス・ペプチドのモデルが,支配的なコイル・コイル構造を採用していることを明らかにしています. より高い温度では,この構造は個々のヘリクとランダム化されたループに切り離されます.
科学分野:
- バイオフィジックス 生物物理学
- コンピューティング・ケミストリー
- 構造生物学 構造生物学とは
背景:
- ペプチドの構成を理解することは,タンパク質の折りたたみと機能に不可欠です.
- モデルシステムとして設計されたペプチドは,複雑なバイオ分子構造の洞察を提供します.
- ヘリックス-ターン-ヘリックスモチーフは,タンパク質の共通の構造要素です.
研究 の 目的:
- モデルヘリックスターンヘリックスペプチド (Ac-A14KG3A14K + 2H+) の構成を調査する.
- このペプチドの温度に依存する構造的移行を特徴付けるために.
主な方法:
- イオン流動性の測定. イオン流動性の測定.
- 分子力学シミュレーション. 分子力学シミュレーション.
主要な成果:
- ペプチドは3つの異なる幾何学を採用しています: 拡張された螺旋形状 (低温),交換されたライシンを持つ転移性構造,および支配的なコイルされたコイル.
- グライシンループで結びついている螺旋アルアニン断面の反並列の配置であるコイルドコイルは,最も安定した形状です.
- 350 K以上の温度では,ヘリクスが分離し,ループはランダム化され,この移行には -45 kJ mol−1 のエンタルピー変化 (ΔH°) と 114 J K−1 mol−1 のエントロピー変化 (ΔS°) が起こります.
結論:
- コイルドコイルは,研究中のモデルペプチドの支配的な構造です.
- 温度がペプチドの構造的安定性に大きく影響し,ヘリックス解離とループランダム化を引き起こします.
- 熱力学パラメータは,ヘリックス・ドッキングとループ・アンコールプロセスに含まれるエネルギーとエントロピーを定量化します.
関連する概念動画
02:06Newman Projections
Different notations are used to represent the three-dimensional structure of molecules on two-dimensional surfaces. One of the most commonly used representations is the dash-wedge formula. The dashed wedges, solid wedges, and the plane lines indicate the groups situated behind the plane, coming out of the plane, and in the plane, respectively.
The organic molecules rotate across the single bonds leading to numerous temporary three-dimensional structures of varying energy known as conformers.
The organic molecules rotate across the single bonds leading to numerous temporary three-dimensional structures of varying energy known as conformers.
02:11Conformations of Cyclohexane
Cyclohexane does not exist in a planar form due to the high angle and torsional strain it would experience in the planar structure. Instead, it adopts non-planar chair and boat conformations.
The chair form is the most stable and derives its name from its resemblance to the “easy chair.” In the chair conformation, two carbon atoms are arranged out-of-plane — one above and one below, minimizing the torsional strain. In the chair form, the bond angle is very close to the ideal tetrahedral value,...
The chair form is the most stable and derives its name from its resemblance to the “easy chair.” In the chair conformation, two carbon atoms are arranged out-of-plane — one above and one below, minimizing the torsional strain. In the chair form, the bond angle is very close to the ideal tetrahedral value,...
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...
01:15¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR
The axial and equatorial protons in cyclohexane can be distinguished by performing a variable-temperature NMR experiment. In this process, except for one proton, the remaining eleven protons are replaced by deuterium. The deuterium substitution avoids the possible peak splitting caused by the spin-spin coupling between the adjacent protons. The remaining proton flips between the axial and equatorial positions.
01:19Polar Curves
The spirograph is a versatile tool for visualizing the relationship between geometry and mathematical representation. In particular, it demonstrates how polar coordinates offer an alternative framework for describing curves in comparison to Cartesian coordinates. Instead of specifying a point by its horizontal and vertical displacements (x, y), polar coordinates use a radius r, the distance from the origin, and an angle θ, measured counterclockwise from the polar axis. This system is...
01:30Oriented Surfaces
A surface is called orientable if a consistent choice of unit normal vector can be made at every point on the surface. A thin soap film stretched across a wire loop provides a familiar example. The film separates the air on one side from the air on the other, so one side can be selected as positive and the opposite side as negative. Once this choice is made, a unit normal vector can be assigned smoothly across the entire surface.At each point on the soap film, a unit normal vector points...