📚 The Importance of Hydrogen Bonding in DNA | 氢键在DNA中的重要性
Deoxyribonucleic acid (DNA) stores the genetic blueprint of life, replicating and transmitting information from one generation to the next with remarkable precision. At the heart of its structure and function lies a subtle and reversible intermolecular force: the hydrogen bond. Although each hydrogen bond is relatively weak on its own, the collective action of thousands of these bonds holds the two strands of the double helix together, enables faithful copying, and allows the controlled access required for gene expression. This article explores the importance of hydrogen bonding in DNA from a chemical perspective, suitable for Cambridge A-Level Chemistry students.
脱氧核糖核酸（DNA）存储着生命的遗传蓝图，以惊人的精确度复制信息并将之代代相传。在其结构与功能的核心，是一种微妙且可逆的分子间作用力：氢键。尽管单个氢键本身相对较弱，但成千上万个氢键的共同作用将双螺旋的两条链维系在一起，实现忠实复制，并允许基因表达所需的可控存取。本文从化学角度探讨氢键在DNA中的重要性，适合剑桥A-Level化学学生阅读。
1. What is Hydrogen Bonding? | 什么是氢键？
A hydrogen bond is a type of intermolecular attraction that occurs when a hydrogen atom covalently bonded to a highly electronegative element (usually nitrogen, oxygen, or fluorine) experiences an electrostatic interaction with a lone pair of electrons on another electronegative atom. The electronegative atom polarises the covalent bond, leaving the hydrogen with a partial positive charge (δ+) that can interact with the δ– region of a nearby acceptor atom.
氢键是一种分子间吸引力，当共价键合在高电负性元素（通常是氮、氧或氟）上的氢原子与另一个电负性原子上的孤对电子发生静电相互作用时便产生。高电负性原子使共价键极化，使氢带部分正电荷（δ+），从而能够与邻近受体原子的δ–区域相互作用。
Typical hydrogen bond strengths range from 5 to 30 kJ mol⁻¹, which is much weaker than covalent bonds (typically 150–400 kJ mol⁻¹) but stronger than van der Waals forces. The directionality of hydrogen bonds—where the donor, hydrogen, and acceptor tend to align linearly—gives them special importance in molecular recognition, as seen in DNA base pairing.
典型的氢键强度在5到30 kJ mol⁻¹之间，远弱于共价键（通常150–400 kJ mol⁻¹），但强于范德华力。氢键具有方向性——供体、氢和受体倾向于直线排列——这使它们在分子识别中特别重要，正如在DNA碱基配对中所见。
2. Overview of DNA Structure | DNA结构概述
DNA is a polymer composed of nucleotide monomers. Each nucleotide consists of a deoxyribose sugar, a phosphate group, and a nitrogenous base. The sugar-phosphate backbones form the two outer strands of the double helix, running antiparallel to each other, while the flat nitrogenous bases project inwards and pair through hydrogen bonds. The four bases in DNA are adenine (A), thymine (T), cytosine (C), and guanine (G).
DNA是由核苷酸单体组成的多聚体。每个核苷酸包含一个脱氧核糖、一个磷酸基团和一个含氮碱基。糖-磷酸骨架构成双螺旋的两条外侧链，彼此反向平行，而扁平的含氮碱基向内突出并通过氢键配对。DNA中的四种碱基是腺嘌呤（A）、胸腺嘧啶（T）、胞嘧啶（C）和鸟嘌呤（G）。
The double helix is stabilised by two main forces: stacking interactions between adjacent base rings (pi–pi and hydrophobic effects) and hydrogen bonding between complementary base pairs. While stacking contributes the most
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