Multidrug resistance of infectious bacterial pathogens has emerged as one of the greatest human health problems. As such, there is a great impetus to develop new generation antibiotics. Cationic amphipathic antimicrobial peptides (AMPs) are nature's ancient antibiotics. They possess a broad spectrum of antimicrobial activity. However, AMP based antibiotics have short lifetime due to protease degradation. Peptide mimics, the so-called peptidomimetics, were recently conceptualized and explored in hope of identifying antibiotic substitutes with superior antimicrobial properties. We are at the nexus of this effort. In particular, we have developed a new class of peptidomimetics referred to as ?-AApeptides, which are named after the N-acylated- N-aminoethyl amino acid unit. ?-AApeptides outperform natural AMPs by providing better potency, and excellent resistance to protease degradation. They are also not prone to eliciting bacterial resistance. Another advantage of ?-AApeptides is their easy accommodation of versatile functional groups. This enables us to design and synthesize various types of ?-AApeptides. So far we have developed a few subclasses of ?- AApeptides through cyclization and lipidation. It was found that ?-AApeptides primarily target bacterial membranes. To translate ?-AApeptides into clinically efficient and safe antibiotic substitutes, a detailed mechanistic understanding of ?-AApeptides interacting with bacterial membranes becomes a prerequisite. For this proposal our first specific aim is to determine interactions between ?-AApeptides and model membranes mimicking bacterial cytoplasmic and outer membranes. Our biophysical studies will elucidate (1) bacterial membrane properties (i.e., structure and nanomechanics) with different lipid compositions, (2) bacterial lipid effect in dictating ?-AApeptide activity, and (3) structural and compositional characteristics of ?-AApeptides that govern their antimicrobial activity. Our second specific aim is to study morphology and elasticity of live bacterial cells modulated by ?-AApeptides. The whole-cell studies will unveil (1) multiple stages employed by ?- AApeptides in killing bacteria, ranging from cell envelope alteration to complete lysis, and (2) dynamic impact of ?-AApeptides on mechanical integrity of live bacterial cells. Bacterial membrane interactions emerging from molecular and cellular level studies will be integrated into our third specific aim, which is to develop potent ?- AApeptides specifically targeting Gram-positive methicillin-resistant S. aureus (MRSA) and Gram-negative P. aeruginosa with minimum inhibitory concentrations meeting clinical standards. The innovation of the proposed project is to establish a platform maximizing the expertise of biophysicists and biochemists. We believe a detailed mechanistic understanding discerned from our biophysical studies will substantially benefit structure and function optimization in generating novel ?-AApeptides. The results from the proposed project will have a strong impact on rational design of novel peptidomimetics with larger antimicrobial efficacy and less propensity of eliciting bacterial resistance.

Public Health Relevance

Multidrug resistance of infectious bacterial pathogens has emerged as one of the greatest human health prob- lems. We propose to study molecular and cellular level interactions between a novel class of peptidomimetics referred to as ?-AApeptides and bacterial membranes. Our ultimate goal is to translate laboratory research findings into the development of new generation peptidomimetic based antibiotics with superb potency and di- minished bacterial resistance.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Academic Research Enhancement Awards (AREA) (R15)
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Biochemistry and Biophysics of Membranes Study Section (BBM)
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Chin, Jean
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University of South Florida
Schools of Arts and Sciences
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Pan, Jianjun; Dalzini, Annalisa; Khadka, Nawal K et al. (2018) Lipid Extraction by ?-Synuclein Generates Semi-Transmembrane Defects and Lipoprotein Nanoparticles. ACS Omega 3:9586-9597
Pan, Jianjun; Sahoo, Prasana K; Dalzini, Annalisa et al. (2017) Membrane Disruption Mechanism of a Prion Peptide (106-126) Investigated by Atomic Force Microscopy, Raman and Electron Paramagnetic Resonance Spectroscopy. J Phys Chem B 121:5058-5071
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Khadka, Nawal K; Teng, Peng; Cai, Jianfeng et al. (2017) Modulation of lipid membrane structural and mechanical properties by a peptidomimetic derived from reduced amide scaffold. Biochim Biophys Acta Biomembr 1859:734-744
Ho, Chian Sing; Khadka, Nawal K; She, Fengyu et al. (2016) Influenza M2 Transmembrane Domain Senses Membrane Heterogeneity and Enhances Membrane Curvature. Langmuir 32:6730-8
Ho, Chian Sing; Khadka, Nawal K; She, Fengyu et al. (2016) Polyglutamine aggregates impair lipid membrane integrity and enhance lipid membrane rigidity. Biochim Biophys Acta 1858:661-70
Pan, Jianjun; Khadka, Nawal K (2016) Kinetic Defects Induced by Melittin in Model Lipid Membranes: A Solution Atomic Force Microscopy Study. J Phys Chem B 120:4625-34