Design of therapeutically viable antimicrobial peptides with cell selectivity against microorganisms is an important step towards the development of new antimicrobial agents. Here, we report four de novo designed, short amphipathic sequences based on a α-helical template comprising of Lys, Trp and Leu or their corresponding D-and/or β-amino acids. Sequence A-12 was protease susceptible whereas its α/β-diastereomeric analogue UNA-12 was resistant to trypsin and proteinase K up to 24 h. A-12 and UNA-12 exhibited broad-spectrum antibacterial activity (MIC: 2–32 µg/mL) against pathogens including methicillin resistant S. aureus (MRSA) and methicillin-resistant S. epidermidis (MRSE). Interestingly, A-12 was found to be most toxic (>50% haemolytic at 250 µg/mL) whereas UNA-12 was found to be non cytotoxic among the all analogues against hRBCs and human keratinocytes. Interaction studies with artificial membranes by tryptophan fluorescence and acrylamide quenching assay demonstrated A-12 interacted equally in bacterial as well as mammalian mimic membrane whereas UNA-12 was found to be more selective towards bacterial mimic membrane. Further microscopic tool has revealed membrane damaging ability of A-12 and UNA-12 with bactericidal mode of action against MRSA. Encouragingly, peptidomimetics analogue UNA-12 showed remarkable safety and efficacy against MRSA in in-vivo neutropenic mice thigh infection model. In summary, simultaneous replacement of the natural amino acids with D-/β-congeners is a promising strategy for designing of potent, cell selective and protease stable peptide based antibiotics.

具有针对微生物的细胞选择性的治疗上可行的抗菌肽的设计是朝着开发新的抗菌剂迈出的重要一步。在此，我们报告了一个基于从头到尾设计的短两亲序列，这些序列是基于一个由Lys，Trp和Leu或其相应D-和/或β-氨基酸组成的α-螺旋模板。序列A-12对蛋白酶敏感，而其α/β-非对映异构体类似物UNA-12在长达24小时的时间内对胰蛋白酶和蛋白酶K具有抗性。A-12和UNA-12对包括耐甲氧西林的金黄色葡萄球菌（MRSA）和耐甲氧西林的表皮葡萄球菌在内的病原体表现出广谱抗菌活性（MIC：2–32 µg / mL）。（MRSE）。有趣的是，在所有针对hRBC和人类角质形成细胞的类似物中，A-12被发现毒性最高（在250 µg / mL时溶血> 50％），而UNA-12被发现无细胞毒性。通过色氨酸荧光和丙烯酰胺淬灭试验与人工膜的相互作用研究表明，A-12在细菌和哺乳动物模拟膜中均等地相互作用，而UNA-12被发现对细菌模拟膜更具选择性。进一步的显微镜工具显示了A-12和UNA-12的膜破坏能力以及对MRSA的杀菌作用。令人鼓舞的是，拟肽模拟物UNA-12在体内对MRSA表现出显着的安全性和有效性中性粒细胞减少症小鼠大腿感染模型。总之，用D- /β-同源物同时替换天然氨基酸是设计有效的，细胞选择性的和蛋白酶稳定的基于肽的抗生素的有前途的策略。