Insights into dynamic properties of water in lipidic cubic phases by 2D nuclear Overhauser effect (NOE) NMR spectroscopy.

Two-dimensional NOE (nuclear Overhauser effect) NMR spectroscopy was employed to investigate the dynamic properties of water within lyotropic bicontinuous lipidic cubic phases (LCPs) formed by monoolein (MO). Experiments observed categorically different effective residence times of water molecules: (i) in proximity to the glycerol moiety of MO, and (ii) adjacent to the hydrophobic chain towards the hydrocarbon tail of MO, as evidenced by the opposite signs of intermolecular NOE cross peaks between protons of water and those of MO in 2D H-H NOESY spectra. Spectroscopic data delineating the different effective residence times of water molecules within both the gyroid (Q) and diamond (Q) phase groups corresponding to hydration levels of 35 and 40 wt%, respectively, are presented.

The Adipokinetic Hormone (AKH) and the Adipokinetic Hormone/Corazonin-Related Peptide (ACP) Signalling Systems of the Yellow Fever Mosquito : Chemical Models of Binding.

Neuropeptides are the main regulators of physiological, developmental, and behavioural processes in insects. Three insect neuropeptide systems, the adipokinetic hormone (AKH), corazonin (Crz), and adipokinetic hormone/corazonin-related peptide (ACP), and their cognate receptors, are related to the vertebrate gonadotropin (GnRH) system and form the GnRH superfamily of peptides. In the current study, the two signalling systems, AKH and ACP, of the yellow fever mosquito, , were comparatively investigated with respect to ligand binding to their respective receptors.

The intricate link between membrane lipid structure and composition and membrane structural properties in bacterial membranes.

It is now evident that the cell manipulates lipid composition to regulate different processes such as membrane protein insertion, assembly and function. Moreover, changes in membrane structure and properties, lipid homeostasis during growth and differentiation with associated changes in cell size and shape, and responses to external stress have been related to drug resistance across mammalian species and a range of microorganisms. While it is well known that the biomembrane is a fluid self-assembled nanostructure, the link between the lipid components and the structural properties of the lipid bilayer are not well understood.

NMR techniques for investigating antimicrobial peptides in model membranes and bacterial cells.

AMPs are short, mainly cationic membrane-active peptides found in all living organism. They perform diverse roles including signaling and acting as a line of defense against bacterial infections. AMPs have been extensively investigated as templates to facilitate the development of novel antimicrobial therapeutics.

A solution NMR view of lipidic cubic phases: Structure, dynamics, and beyond.

Nuclear magnetic resonance (NMR) spectroscopy is well-established nowadays for the elucidation of the 3D structures of proteins and protein complexes, the evaluation of biomolecular dynamics with atomistic resolution across a range of time scales, the screening of drug candidates with site specificity, and for the quantitation of molecular translational diffusion. Lyotropic lipidic cubic phases (LCPs) are lipid bilayer-based materials with a complex geometry, formed the spontaneous self-assembly of certain lipids in an aqueous environment at specific temperature ranges. LCPs have been successfully applied to the crystallization of membrane proteins for structural studies by X-ray crystallography, and have also shown promising potential for serving as matrices for drug and nutrient delivery/release .

The membrane activity of the antimicrobial peptide caerin 1.1 is pH dependent.

Antimicrobial peptides are an important class of membrane-active peptides that can provide alternatives or complements to classic antibiotics. Among the many classes of AMPs, the histidine-rich family is of particular interest since they may induce pH-sensitive interactions with cell membranes. The AMP caerin 1.

In-cell DNP NMR reveals multiple targeting effect of antimicrobial peptide.

Dynamic nuclear polarization NMR spectroscopy was used to investigate the effect of the antimicrobial peptide (AMP) maculatin 1.1 on cells. The enhanced N NMR signals from nucleic acids, proteins and lipids identified a number of unanticipated physiological responses to peptide stress, revealing that membrane-active AMPs can have a multi-target impact on cells.

Transformation of L-DOPA and Dopamine on the Surface of Gold Nanoparticles: An NMR and Computational Study.

Gold nanoparticles (AuNPs) have found applications in biomedicine as diagnostic tools, but extensive research efforts have been also directed toward their development as more efficient drug delivery agents. The high specific surface area of AuNPs may provide dense loading of molecules like catechols (L-DOPA and dopamine) on nanosurfaces, enabling functionalization strategies for advancing conventional therapy and diagnostic approaches of neurodegenerative diseases. Despite numerous well-described procedures in the literature for preparation of different AuNPs, possible transformation and structural changes of surface functionalization agents have not been considered thoroughly.

Ultrasound-induced protein restructuring and ordered aggregation to form amyloid crystals.

Amyloid crystals, a form of ordered protein aggregates documented relatively recently, have not been studied as extensively as amyloid fibres. This study investigates the formation of amyloid crystals with low frequency ultrasound (20 kHz) using β-lactoglobulin, as a model protein for amyloid synthesis. Acoustic cavitation generates localised zones of intense shear, with extreme heat and pressure that could potentially drive the formation of amyloid structures at ambient bulk fluid temperatures (20 ± 1 °C).

NMR measurement of biomolecular translational and rotational motion for evaluating changes of protein oligomeric state in solution.

Defining protein oligomeric state and/or its changes in solution is of significant interest for many biophysical studies carried out in vitro, especially when the nature of the oligomeric state is crucial in the subsequent interpretation of experimental results and their biological relevance. Nuclear magnetic resonance (NMR) is a well-established methodology for the characterization of protein structure, dynamics, and interactions at the atomic level. As a spectroscopic method, NMR also provides a compelling means for probing both molecular translational and rotational motion, two predominant measures of effective molecular size in solution, under identical conditions as employed for structural, dynamic and interaction studies.

NMR spectroscopy of lipidic cubic phases.

Lipidic cubic phase (LCP) structures have been used for stabilisation and crystallisation of membrane proteins and show promising properties as drug carriers. In this mini-review, we present how NMR spectroscopy has played a major role in understanding the physico-chemical properties of LCPs and how recent advances in pulsed field gradient NMR techniques open new perspectives in characterising encapsulated molecules.

Enhancing proline-rich antimicrobial peptide action by homodimerization: influence of bifunctional linker.

Antimicrobial peptides (AMPs) are host defense peptides, and unlike conventional antibiotics, they possess potent broad spectrum activities and, induce little or no antimicrobial resistance. They are attractive lead molecules for rational development to improve their therapeutic index. Our current studies examined dimerization of the designed proline-rich AMP (PrAMP), Chex1-Arg20 hydrazide, C-terminal thiol addition to a series of bifunctional benzene or phenyl tethers to determine the effect of orientation of the peptides and linker length on antimicrobial activity.

Multi-Omic Analysis to Characterize Metabolic Adaptation of the Lipidome in Response to Environmental Stress.

As an adaptive survival response to exogenous stress, bacteria undergo dynamic remodelling of their lipid metabolism pathways to alter the composition of their cellular membranes. Here, using as a well characterised model system, we report the development and application of a 'multi-omics' strategy for comprehensive quantitative analysis of the temporal changes in the lipidome and proteome profiles that occur under exponential growth phase versus stationary growth phase conditions i.e.

Water diffusion in complex systems measured by PGSE NMR using chemical shift selective stimulated echo: Elimination of magnetization exchange effects.

The interpretation of molecular translational diffusion as measured by pulsed gradient spin-echo NMR (PGSE NMR) can be complicated by the presence of chemical exchange and/or dipolar cross-relaxation (including relayed cross-relaxation via spin diffusion). The magnitude of influence depends on the kinetics of exchange and/or dipolar cross-relaxation present within the system as well as the PGSE NMR sequences chosen for measurements. First, we present an exchange induced zero-crossing phenomenon for signal attenuation of water in lipidic cubic phases (formed by a mixture of monoolein and water) in the presence of pulsed gradients observed using a standard STimulated Echo (STE) sequence.

Spectroscopic study of L-DOPA and dopamine binding on novel gold nanoparticles towards more efficient drug-delivery system for Parkinson's disease.

Nano-drug delivery systems may potentially overcome current challenges in the treatment of Parkinson's disease (PD) by enabling targeted delivery and more efficient blood-brain penetration ability. This study investigates novel gold nanoparticles (AuNPs) to be used as delivery systems for L-DOPA and dopamine by considering their binding capabilities in the presence and absence of a model protein, bovine serum albumin (BSA). Four different AuNPs were prepared by surface functionalization with polyethylene glycol (PEG), 1-adamantylamine (Ad), 1-adamantylglycine (AdGly), and peptidoglycan monomer (PGM).

Characterisation of cell membrane interaction mechanisms of antimicrobial peptides by electrical bilayer recording.

Many antimicrobial peptides (AMPs) are cationic host defence peptides (HDPs) that interact with microbial membranes. This ability may lead to implementation of AMPs as therapeutics to overcome the wide-spread antibiotic resistance problem as the affected bacteria may not be able to recover from membrane lysis types of attack. AMP interactions with lipid bilayer membranes are typically explained through three mechanisms, i.

The impact of antibacterial peptides on bacterial lipid membranes depends on stage of growth.

The impact of maculatin 1.1 (Mac1) on the mechanical properties of supported lipid membranes derived from exponential growth phase (EGP) and stationary growth phase (SGP) lipid extracts was analysed by surface plasmon resonance and atomic force microscopy. Each membrane was analysed by quantitative nanomechanical mapping to derive measurements of the modulus, adhesion and deformation in addition to bilayer height.

TOAC spin-labeled peptides tailored for DNP-NMR studies in lipid membrane environments.

The benefit of combining in-cell solid-state dynamic nuclear polarization (DNP) NMR and cryogenic temperatures is providing sufficient signal/noise and preservation of bacterial integrity via cryoprotection to enable in situ biophysical studies of antimicrobial peptides. The radical source required for DNP was delivered into cells by adding a nitroxide-tagged peptide based on the antimicrobial peptide maculatin 1.1 (Mac1).

Utilizing magnetic resonance techniques to study membrane interactions of amyloid peptides.

Alzheimer's disease (AD) is a common neurodegenerative condition that involves the extracellular accumulation of amyloid plaques predominantly consisting of Aβ peptide aggregates. The amyloid plaques and soluble oligomeric species of Aβ are believed to be the major cause of synaptic dysfunction in AD brain and their cytotoxic mechanisms have been proposed to involve interactions with cell membranes. In this review, we discuss our solid-state nuclear magnetic resonance (ssNMR) studies of Aβ interactions with model membranes.

C-terminus amidation influences biological activity and membrane interaction of maculatin 1.1.

Cationic antimicrobial peptides have been investigated for their potential use in combating infections by targeting the cell membrane of microbes. Their unique chemical structure has been investigated to understand their mode of action and optimize their dose-response by rationale design. One common feature among cationic AMPs is an amidated C-terminus that provides greater stability against in vivo degradation.

Expression and purification of the native C-amidated antimicrobial peptide maculatin 1.1.

Maculatin 1.1 (Mac1) is an antimicrobial peptide (AMP) from an Australian tree frog and exhibits low micromolar activity against Gram-positive bacteria. The antimicrobial properties of Mac1 are linked to its disruption of bacterial lipid membranes, which has been studied extensively by in vitro nuclear magnetic resonance (NMR) spectroscopy and biophysical approaches.

Structural Disruptions of the Outer Membranes of Gram-Negative Bacteria by Rationally Designed Amphiphilic Antimicrobial Peptides.

Gram-negative bacteria are covered by both an inner cytoplasmic membrane (IM) and an outer membrane (OM). Antimicrobial peptides (AMPs) must first permeate through the OM and cell wall before attacking the IM to cause cytoplasmic leakage and kill the bacteria. The bacterial OM is an asymmetric bilayer with the outer leaflet primarily composed of lipopolysaccharides (LPSs) and the inner leaflet composed of phospholipids (PLs).

Chemically modified and conjugated antimicrobial peptides against superbugs.

Antimicrobial resistance (AMR) is one of the greatest threats to human health that, by 2050, will lead to more deaths from bacterial infections than cancer. New antimicrobial agents, both broad-spectrum and selective, that do not induce AMR are urgently required. Antimicrobial peptides (AMPs) are a novel class of alternatives that possess potent activity against a wide range of Gram-negative and positive bacteria with little or no capacity to induce AMR.

(Re)Defining the Proline-Rich Antimicrobial Peptide Family and the Identification of Putative New Members.

As we rapidly approach a post-antibiotic era in which multi-drug resistant bacteria are ever-pervasive, antimicrobial peptides (AMPs) represent a promising class of compounds to help address this global issue. AMPs are best-known for their membrane-disruptive mode of action leading to bacteria cell lysis and death. However, many AMPs are also known to be non-lytic and have intracellular modes of action.