過張B-DNA:個々の二重鎖および単一鎖DNA分子の弾性反応
S B Smith1, Y Cui, C Bustamante
1Institute of Molecular Biology, University of Oregon, Eugene 97403, USA.
Science (New York, N.Y.)
|February 9, 1996
まとめ
レーザーピンチで二重鎖DNA (dsDNA) を伸縮すると,65 pNで安定した超伸縮形が明らかになりました. この反転可能な移行は,イオン強度の影響を受け,DNA再結合エネルギーに影響を与える可能性があります.
科学分野:
- 分子生物学は分子生物学である.
- バイオフィジックス 生物物理学
- バイオケミストリー バイオケミストリー
背景:
- DNAメカニズムを理解することは,分子生物学にとって極めて重要です.
- DNAは,正規のB型を超えて様々な構造形態に存在する.
- DNAの機械的性質は,その生物学的機能に影響を与えます.
研究 の 目的:
- 二重鎖DNA (dsDNA) の力作用下における機械的性質を調査する.
- 過剰なDNA状態への移行を特徴付けるために.
- このDNA移行に影響を与える要因を探求するために.
主な方法:
- 力を測定するレーザーピンチを使って,単一のDNA分子を伸ばした.
- 水性バッファ内のdDNAに制御された縦方向のストレスを適用した.
- DNAの長さの変化と構造的移行の可逆性を測定した.
主要な成果:
- dsDNAは,65ピコニュートン (pN) で安定した超伸縮形状への協力的移行を経験します.
- この過剰に伸びたDNAはB型dDNAよりも70%長く,塩基対あたり5.8アングストーム上昇する.
- この移行は,ストレス緩和時に逆転し,イオン強度と水の活性によって影響を受けます.
結論:
- 過剰に伸びたDNA形態は,安定した,機械的に誘発された状態です.
- イオン強度などの環境要因は,DNAの機械的移行を調節する.
- 過剰に伸びたDNA構成は,DNA再結合エネルギー学において有意である可能性があります.
関連する概念動画
01:02The DNA Replication Fork
An organism’s genome needs to be duplicated in an efficient and error-free manner for its growth and survival. The replication fork is a Y-shaped active region where two strands of DNA are separated and replicated continuously. The coupling of DNA unzipping and complementary strand synthesis is a characteristic feature of a replication fork. Organisms with small circular DNA, such as E. coli, often have a single origin of replication; therefore, they have only two replication forks, one in...
02:02DNA Topoisomerases
Topoisomerases are enzymes that relax overwound DNA molecules during various cell processes, including DNA replication and transcription. These enzymes regulate positive and negative DNA supercoiling without changing the nucleotide sequence. DNA overwinding in a clockwise direction results in positively supercoiled DNA, whereas underwinding in a counterclockwise direction produces negatively supercoiled DNA.
Types and Mechanism of action
Topoisomerases are divided into two main types. Type I...
Types and Mechanism of action
Topoisomerases are divided into two main types. Type I...
02:04Fixing Double-strand Breaks
The double-stranded structure of DNA has two major advantages. First, it serves as a safe repository of genetic information where one strand serves as the back-up in case the other strand is damaged. Second, the double-helical structure can be wrapped around proteins called histones to form nucleosomes, which can then be tightly wound to form chromosomes. This way, DNA chains up to 2 inches long can be contained within microscopic structures in a cell. A double-stranded break not only damages...
02:31Homologous Recombination
The basic reaction of homologous recombination (HR) involves two chromatids that contain DNA sequences sharing a significant stretch of identity. One of these sequences uses a strand from another as a template to synthesize DNA in an enzyme-catalyzed reaction. The final product is a novel amalgamation of the two substrates. To ensure an accurate recombination of sequences, HR is restricted to the S and G2 phases of the cell cycle. At these stages, the DNA has been replicated already and the...
01:03Single-Strand DNA Binding Proteins
For successful DNA replication, the unwinding of double-stranded DNA must be accompanied by stabilization and protection of the separated single strands of the DNA. This crucial task is performed by single-strand DNA-binding (SSB) proteins. They bind to the DNA in a sequence-independent manner, which means that the nitrogenous bases of the DNA need not be present in a specific order for binding of SSB proteins to it. The binding of SSB proteins straightens single-stranded DNA (ssDNA) and makes...
02:04Fixing Double-strand Breaks
The double-stranded structure of DNA has two major advantages. First, it serves as a safe repository of genetic information where one strand serves as the back-up in case the other strand is damaged. Second, the double-helical structure can be wrapped around proteins called histones to form nucleosomes, which can then be tightly wound to form chromosomes. This way, DNA chains up to 2 inches long can be contained within microscopic structures in a cell. A double-stranded break not only damages...