Novel Bioactive Conformation Constructed by Structurally Constrained CH/π Interaction between Amino Acids Side Chains

烷基（CH给体）和苯环（π给体）之间的CH/π相互作用是一种氢键，对构建特定的蛋白质三维结构具有重要意义。本研究的目的是建立一种新的方法，通过构建氨基酸侧链之间的CH/π相互作用来限制肽的生物活性构象，从而创造一种新的生物活性肽。CH/π相互作用应该成为疏水核心的结构要素。具有D-L构型序列的二肽亮氨酸在亮氨酸异丁基和苯基之间构建了典型的CH/π相互作用。这个二肽有一个n端游离氨基和一个c端游离羧基。如果我们能够加载一个结构元件来诱导与目标肽或蛋白质分子的特定相互作用，那么衍生物将成为一种新型的激动剂，目标的抑制剂。我们已经成功地设计和合成了一系列特异性更高的丝氨酸蛋白酶抑制剂，通过偶联一个基团结合到每个酶的底物识别位点。当苯基与c端羧基结合时，得到的D-Leu-Phe苯酰胺被发现是一种强的凝乳胰蛋白酶抑制剂。当该苯基的对氢被胍基取代时，衍生物对凝乳胰蛋白酶没有抑制作用。相反，它强烈抑制胰蛋白酶，另一种丝氨酸蛋白酶。因此，新合成了几个系列的化合物作为胰蛋白酶和凝乳胰蛋白酶的抑制剂。结果清楚地表明，二肽单元D-Leu-Phe可以作为一个结构核心来加载一个元素，作为一种新的生物活性肽。本研究将为肽科学的结构-活性研究开辟一个新的领域。为了加强CH/π的相互作用，寻找更适合作为CH给体或π给体的结构是很重要的。作为给体，我们设计了一系列氨基酸，其侧链含有甲胺基团（-N）CH3n （n= 1,2,3）。此外，我们还合成了苯丙氨酸衍生物，作为强π给体，其苯基氢被卤素取代。例如，当间溴-对氟苯丙氨酸在位置2被掺入到SFLLRNP中时，可使凝血酶受体栓系配体肽SFLLRNF的活性提高约6倍。显然，这是一种通过增强结构受限的CH/π相互作用来增强活性的新方法。因此，这项研究项目的主要目标取得了巨大的科学成就。少

The CH/π interaction between alkyl group (CH donor) and benzene ring (π donor) is a kind of hydrogen bondings, and is important to construct a particular three-dimensional structure of proteins. The goal of the present study is to establish a novel method to constrain the bioactive conformation of peptides by constructing such a CH/π interaction between amino acid side chains in order to create a novel biologically active peptide. The CH/π interaction should become a structural essential with the hydrophobic core. Dipeptide Leu-Phe with the D-L configurational sequence constructs a typical CH/π interaction between Leu-isobutyl group and Phe-phenyl group. This dipeptide has a N-terminal free amino group and a C-terminal free carboxyl group. If we are able to load a structural element to induce a specific interaction with the target peptide or protein molecule(s), the derivative would be a new type of agonist, inhibitors of the target. We have succeeded in the design and synthesis of spe … More cific inhibitors of a series of serine proteases by conjugating a group that binds to the substraterecognition site of each enzyme. When the benzyl group was combined to the C-terminal carboxyl group, the resulting D-Leu-Phe benzyl amide was found to be a strong inhibitor of chymotrypsin. When the para-hydrogen of this benzyl group was replaced by the guanidine group, the derivative showed no inhibition for chymotrypsin. Instead, it strongly inhibited trypsin, another type serine protease. Thus, several series of compounds were newly synthesized as inhibitors of trypsin and chymotrypsin. The results clearly indicate that the dipeptide unit D-Leu-Phe can be a structural core to load an element to function as a novel bioactive peptide. The procedure employed in this study will definitely open a new field in the structure-activity studies of peptide sciences.In order to strengthen the CH/π interaction, it is important to search the structures more suitable as a CH donor or as a π donor. As CH donors we have designed a series of amino acids, the side chains of which contain the methylamine group, (-N)CH3n (n=1, 2, and 3). In addition, we achieved the synthesis of the phenylalanine derivatives, as strong π donors the phenylhydrogens of which were substituted with halogens. For instance, meta-bromo-para-fluorophenylalanine increased the activity of thrombin receptor-tethered ligand peptide SFLLRNF about six times when it was incorporated into this SFLLRNP at position 2. Apparently, this is a new way to enhance the activity by reinforcing the structurally restricted CH/π interaction. Thus, the major goal of this research project was achieved with enormous scientific successes. Less