期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2021
卷号：118
期号：2
页码：1
DOI：10.1073/pnas.2024376118
出版社：The National Academy of Sciences of the United States of America
摘要：Water is a key component of biological systems. Traditionally, water is considered as the background against which biology evolves. However, recently, it is becoming apparent that water is very much an essential part of the system. One could even ask to what extent water determines the structure of proteins, membranes, DNA, and the more complex biomachinery that is composed of multiple compounds. To answer this question, it is important to understand how the hydration shell of a biomolecule responds to its structural changes. Chirality (or handedness) is one of the most fundamental aspects of biomolecular structure. Two molecular groups are chiral when they have the same chemical structure but are each other’s mirror image. Amino acids in proteins are chiral, and although they can exist as left (l-) and right-handed (d-) mirror images, only l-enantiomers are found in nature. In contrast, sugars and DNA occur only in d-form. Macromolecules constructed from chiral building blocks form either exclusively l- or d-structures. The vast majority of biological reactions in aqueous environments are fine-tuned for their speed and accuracy by using chiral selectivity. Determining the structural properties of water around chiral biomolecules is therefore important to understand the complexity of life itself. However, experimentally measuring the structure of water in contact with a biomolecule or larger molecular assemblies is a challenging task. In PNAS Perets et al. (1) implement an elegant approach that combines interferometric chiral sum frequency generation (SFG) spectroscopy, isotopic exchange experiments, and molecular dynamics (MD) simulations to understand the relationship between peptide β-sheets and their hydrating water. (l-) and (d-) antiparallel peptide β-sheets are demonstrated to impart their chirality to adjacent water molecules, leading to chiral superstructures of water around peptides that extend for approximately five hydration layers.
