I remember it like it was yesterday, even though it was more than 30 years ago. I was a graduate student at the University of Arizona (U.S.A.), sitting at my desk, eating lunch and perusing the latest issue of Science magazine. I came across an article about an intriguing new molecule called “polyamide nucleic acid” or PNA.^[1] (We now define PNA as “peptide nucleic acid,” which is a perfectly fine name, except that PNA technically is not a peptide, it is not found in the nucleus and it is not an acid!) My Ph.D. thesis research had nothing to do with nucleic acid chemistry, but I still found the article fascinating, as the authors—Peter Nielsen, Michael Egholm, Rolf Berg, and the late Ole Buchardt at the University of Copenhagen (Denmark)—reported the ability of PNA to bind complementary DNA targets via a novel strand-invasion mechanism. The exceptionally high affinity of PNA for its targets, its resistance to natural degradation pathways and its fidelity to the Watson–Crick rules for base pairing sparked an intense level of excitement in both the fundamental science and the applications of PNA that continues to this day. Reading that paper certainly triggered my interest in nucleic acids and motivated me to seek out a postdoctoral position in the field. Two years later, I joined the laboratory of Gary Schuster at the University of Illinois (U.S.A.) where, by way of a happy accident, I had the good fortune to begin working with PNA through collaboration with Peter Nielsen's laboratory. 29 years later, my lab continues to work with this amazing molecule and its descendants. That paper changed my life!

In this Special Collection of Biopolymers, we have gathered original research and review articles that highlight the ongoing evolution of PNA—both its structure and its applications. Backbone modifications that enhance affinity, nucleobase modifications that promote cell uptake, new applications in biosensing and self-assembly, and advances in targeting non-canonical structures, such as double-stranded RNA all demonstrate the versatility of PNA. While the original structure of PNA bedeviled researchers because of technical issues, for example aggregation, the next generation of PNAs have overcome these challenges. Moreover, the exploitation of PNA's peptide-like character via incorporation of amino acid side chains into the backbone, distinguishes PNA from other members of the nucleic acid alphabet soup, for example, LNA, that are more closely related to the natural biopolymers DNA and RNA.

We hope you enjoy reading these articles and that you will return from time to time as we plan to take advantage of the dynamic nature of a virtual Special Collection to add more contributions in the future. Who knows what is in store for PNA, but the seemingly endless varieties that chemists are producing and the innovative new applications that scientists and biotechnologists continue to develop give great optimism that the PNA universe will continue to expand from the Big Bang of the 1991 paper.

我记得它就像昨天一样，尽管那是 30 多年前的事了。我是亚利桑那大学（美国）的一名研究生，坐在办公桌前吃午饭，仔细阅读最新一期的《科学》杂志。我偶然发现了一篇关于一种名为“聚酰胺核酸”或 PNA 的有趣新分子的文章。^{[ 1 ]}（我们现在将 PNA 定义为“肽核酸”，这是一个非常好的名称，只是 PNA 在技术上不是肽，它不存在于细胞核中，也不是酸！）我的博士学位。论文研究与核酸化学无关，但我仍然觉得这篇文章很吸引人，因为作者——Peter Nielsen、Michael Egholm、Rolf Berg 和已故的哥本哈根大学（丹麦）的 Ole Buchardt——报告了核酸化学的能力PNA 通过一种新的链入侵机制结合互补 DNA 靶标。PNA 对其目标的异常高亲和力、对自然降解途径的抵抗力以及对碱基配对的 Watson-Crick 规则的忠实度在基础科学和 PNA 应用中引发了强烈的兴奋，这种兴奋一直持续到今天。阅读那篇论文无疑激发了我对核酸的兴趣，并促使我在该领域寻求博士后职位。两年后，我加入了伊利诺伊大学（美国）的 Gary Schuster 实验室，在那里，由于一个幸运的意外，我有幸通过与 Peter Nielsen 实验室的合作开始了与 PNA 的合作。29 年后，我的实验室继续研究这种神奇的分子及其后代。那篇论文改变了我的生活！我的实验室继续研究这种神奇的分子及其后代。那篇论文改变了我的生活！我的实验室继续研究这种神奇的分子及其后代。那篇论文改变了我的生活！

在这个生物聚合物的特别收藏中，我们收集了突出 PNA 持续发展的原创研究和评论文章——包括其结构和应用。增强亲和力的主链修饰、促进细胞摄取的核碱基修饰、生物传感和自组装中的新应用以及靶向非规范结构（如双链 RNA）的进展都证明了 PNA 的多功能性。虽然 PNA 的原始结构由于聚合等技术问题困扰着研究人员，但下一代 PNA 已经克服了这些挑战。此外，通过将氨基酸侧链纳入主链来利用 PNA 的肽样特性，将 PNA 与核酸字母汤的其他成员区分开来，例如 LNA，

我们希望您喜欢阅读这些文章，并且您会不时回来，因为我们计划利用虚拟特别收藏的动态特性在未来添加更多贡献。谁知道 PNA 会发生什么，但化学家正在生产的看似无穷无尽的品种以及科学家和生物技术专家不断开发的创新应用让人非常乐观地认为 PNA 宇宙将从 1991 年论文的“大爆炸”开始继续扩展。