Direct Site Selective 19F- and 18F-labelling of Peptides and Proteins Towards "Zero Size - Zero Background" Bioimaging

非侵入性成像技术现在主导着疾病诊断，原则上可以在分子水平上提供疾病状态的重要知识。在这种情况下，准确的诊断将允许更适当和成功的治疗方案。在过去的几十年里，已经建立了无数的成像方法，也许更突出的是磁共振成像、光学成像、超声、正电子发射断层扫描和X射线计算机断层扫描。与此同时，一系列用作示踪剂、靶向或造影剂的小分子、分子络合物、微米和纳米级材料已经经历了高度多样化，以通过增强信号来支持这些技术。然而，尽管取得了这些显著的进展，分子成像剂的使用仍然令人惊讶地缺乏--分子成像剂不仅能提供更好的信号，还能告诉我们与疾病相关的分子事件。因此，在生物学和疾病的分子过程的基本理解方面进展较慢。我们的目标是通过开发一种通用方法来弥合分子科学和医学科学之间的这种“脱节”，这种方法将允许创造创新的化学工具来生产用于“分子成像”的卓越探针。获得精确的氟(F)修饰的多肽和蛋白质是非常有用的，可以使复杂基质中的生物现象可视化，包括细胞裂解物、整个细胞，甚至整个生物体。19F核磁共振波谱在药物化学中是推动早期铅发现工作的有价值的工具，19F核磁共振成像(MRI)已被应用于临床前模型中的细胞跟踪和生物标记物的分子成像的原理验证研究。在核医学中，正电子发射断层扫描(PET)是一种强大的非侵入性成像技术，可以可视化整个生物体，前提是人们可以接触到18F标记的小分子、多肽和蛋白质。18F是一种回旋加速器产生的放射性同位素，具有一系列有利的物理性质，包括合理的半衰期(略低于两小时)和干净的衰变曲线(97%的正电子发射)。这些非凡的应用鼓励了许多科学家开发获得氟标记生物制剂的方法。从反应性的观点来看，氟是元素周期表中一个具有挑战性的元素，它阻碍了有效、精确和可重复的直接氟肽或氟蛋白质键结构的发展。为了绕过这些困难，化学家们选择首先对多肽或蛋白质进行修饰，使其标记上能够掺入氟的所谓假体。然而，这种假体可以改变本地生物制品的结构，以至于功能受到有害的影响。因此，迫切需要一种直接、有效、准确、易于实施的蛋白质氟化方法。在这里，我们建议开发这样一种方法，通过汇集两位申请者的专业知识来精确地标记多肽和蛋白质，这两位申请者在化学生物学和化学医学的背景下共同拥有广泛的氟化学和多肽/蛋白质化学知识。我们方法的新颖性是开发了一种无接头假体技术，它用非天然的CH2SCF3和CH2CF3侧链修饰多肽和蛋白质，用于生物成像，可能的最小对称多氟基团：CF3。我们提出的晚期19F-和18F-三氟甲基化多肽和蛋白质，依赖于所谓的19F-和18F-Uemoto试剂的可用性，不仅是非常新颖的，而且可能被证明是转变为成像科学的工具。

Non-invasive imaging techniques now dominate disease diagnosis and can, in principle, provide vital knowledge of disease states at the molecular level. In this was accurate diagnosis will allow more appropriate and successful treatment plans. A myriad of imaging methods, perhaps more prominently magnetic resonance imaging, optical imaging, ultrasonography, positron emission tomography and X-ray computed tomography have become established over the past decades. In parallel, a range of small molecules, molecular complexes, micro- and nanoscale materials used as tracers, targeting or contrast agents has undergone intense diversification to support these technologies by enhancing signal. However, despite this remarkable progresses, there is a surprising lack in the use of molecular imaging agents - agents that not only give a better signal but also tell us about the molecular events associated with the disease. As a result, there has been slower progress towards the fundamental understanding of molecular processes in biology and diseases. We aim to bridge this 'disconnect' between the molecular and medicinal sciences through the development of a general method that will allow creation of innovative chemical tools to produce superior probes for 'molecular imaging'. Access to precisely fluorine(F)-modified peptides and proteins is incredibly useful to allow the visualisation of biological phenomena in complex matrices including cellular lysates, whole cells, and even whole organisms. 19F Nuclear Magnetic Resonance (NMR) spectroscopy is a valuable tool in medicinal chemistry driving early lead discovery efforts, and 19F Magnetic Resonance Imaging (MRI) has been applied in proof-of-principle studies to cell tracking and for molecular imaging of biomarkers in preclinical models. In nuclear medicine, positron emission tomography (PET) is a powerful non-invasive imaging technique that can visualise whole organisms providing that one can access 18F-labelled mall molecules, peptides and proteins. 18F is a cyclotron-produced radioisotope that presents a range of advantageous physical properties including reasonable half life (just under two hours) and clean decay profile (97% positron emission). These remarkable applications have encouraged many scientists to develop methodologies to access fluorine-labelled biologics. From a reactivity viewpoint, fluorine is a "challenging"element of the periodic table, that has prevented the development of effective, precise and reproducible direct fluorine-peptide or fluorine-protein bond construction. To circumvent these difficulties, chemists have opted to modify firstly the peptide or protein to be labelled with a so-called prosthetic that is amenable to fluorine incorporation. However, such prosthetics can modify the structure of the native biologics to such a degree that function is affected in a detrimental way. As a result, direct, effective, precise and easy to implement methods for protein fluorination are in urgent demand. Here, we propose to develop such a method to precisely fluorine-label peptide and proteins by pooling the expertise of the two applicants who together have extensive knowledge of fluorine chemistry and peptide/protein chemistry within the context of chemical biology and chemical medicine. The novelty of our approach is the development of a linker-prosthetic free technology that modifies peptide and proteins with the unnatural CH2SCF3 and CH2CF3 side-chains for application in bioimaging with the minimal symmetrical multi-fluorine group that is possible: CF3. Our proposed late stage 19F- and 18F-trifluoromethylation of peptide and proteins that relies on the availability of so-called 19F- and18F-Umemoto reagents is not only highly novel but could prove transformatory to imaging science as a tool.