Department of Chemical Engineering, Michigan State University, East Lansing, Michigan, USA.
Department of Biomedical Engineering, Michigan State University, East Lansing, Michigan, USA.
NMR Biomed. 2023 Nov;36(11):e5007. doi: 10.1002/nbm.5007. Epub 2023 Jul 19.
Chemical exchange saturation transfer (CEST) MRI has been identified as a novel alternative to classical diagnostic imaging. Over the last several decades, many studies have been conducted to determine possible CEST agents, such as endogenously expressed compounds or proteins, that can be utilized to produce contrast with minimally invasive procedures and reduced or non-existent levels of toxicity. In recent years there has been an increased interest in the generation of genetically engineered CEST contrast agents, typically based on existing proteins with CEST contrast or modified to produce CEST contrast. We have developed an in silico method for the evolution of peptide sequences to optimize CEST contrast and showed that these peptides could be combined to create de novo biosensors for CEST MRI. A single protein, superCESTide, was designed to be 198 amino acids. SuperCESTide was expressed in E. coli and purified with size exclusion chromatography. The magnetic transfer ratio asymmetry generated by superCESTide was comparable to levels seen in previous CEST reporters, such as protamine sulfate (salmon protamine) and human protamine. These data show that novel peptides with sequences optimized in silico for CEST contrast that utilize a more comprehensive range of amino acids can still produce contrast when assembled into protein units expressed in complex living environments.
化学交换饱和转移（CEST）MRI 已被确定为一种替代经典诊断成像的新方法。在过去的几十年中，已经进行了许多研究来确定可能的 CEST 试剂，例如内源性表达的化合物或蛋白质，可以用于以微创程序和降低或不存在的毒性水平产生对比。近年来，人们对基因工程 CEST 对比剂的产生产生了浓厚的兴趣，这些对比剂通常基于具有 CEST 对比的现有蛋白质，或者经过修饰以产生 CEST 对比。我们已经开发了一种用于优化 CEST 对比的肽序列进化的计算方法，并表明这些肽可以组合在一起，为 CEST MRI 创建新的生物传感器。一个名为 SuperCESTide 的单一蛋白质被设计为 198 个氨基酸。SuperCESTide 在大肠杆菌中表达，并通过尺寸排阻层析进行纯化。SuperCESTide 产生的磁转移比不对称性与先前的 CEST 报告剂（如硫酸鱼精蛋白和人鱼精蛋白）中观察到的水平相当。这些数据表明，在计算机中针对 CEST 对比进行序列优化的新型肽，利用更全面的氨基酸范围，当组装成在复杂的生活环境中表达的蛋白质单位时，仍然可以产生对比。
