Structure and Dynamics of Cinnamycin-Lipid Complexes: Mechanisms of Selectivity for Phosphatidylethanolamine Lipids.

Cinnamycin is a lantibiotic peptide, which selectively binds to and permeabilizes membranes containing phosphatidylethanolamine (PE) lipids. As PE is a major component of many bacterial cell membranes, cinnamycin has considerable potential for destroying these. In this study, molecular dynamics simulations are used to elucidate the structure of a lipid-cinnamycin complex and the origin of selective lipid binding.

A unified heteronuclear decoupling picture in solid-state NMR under low radio-frequency amplitude and fast magic-angle-spinning frequency regime.

Heteronuclear spin decoupling is a highly important component of solid-state NMR experiments to remove undesired coupling interactions between unlike spins for spectral resolution. Recently, experiments using a unification strategy of standard decoupling schemes were presented for high radio-frequency (RF) amplitudes and slow-intermediate magic-angle-spinning (MAS) frequencies, in the pursuit of deeper understanding of spin decoupling under phase-modulated RF irradiation [A. Equbal et al.

Intermittent, low dose carbon monoxide exposure enhances survival and dopaminergic differentiation of human neural stem cells.

Exploratory studies using human fetal tissue have suggested that intrastriatal transplantation of dopaminergic neurons may become a future treatment for patients with Parkinson's disease. However, the use of human fetal tissue is compromised by ethical, regulatory and practical concerns. Human stem cells constitute an alternative source of cells for transplantation in Parkinson's disease, but efficient protocols for controlled dopaminergic differentiation need to be developed.

Critical Influence of Cosolutes and Surfaces on the Assembly of Serpin-Derived Amyloid Fibrils.

Many proteins and peptides self-associate into highly ordered and structurally similar amyloid cross-β aggregates. This fibrillation is critically dependent on properties of the protein and the surrounding environment that alter kinetic and thermodynamic equilibria. Here, we report on dominating surface and solution effects on the fibrillogenic behavior and amyloid assembly of the C-36 peptide, a circulating bioactive peptide from the α-antitrypsin serine protease inhibitor.

The Changing Face of Aging: Highly Sulfated Glycosaminoglycans Induce Amyloid Formation in a Lattice Corneal Dystrophy Model Protein.

Glycosaminoglycans (GAGs) are related to multiple biological functions and diseases. There is growing evidence that GAG concentration and sulfate content increase with age. The destabilizing mutation A546T in the corneal protein TGFBIp leads to lattice-type corneal dystrophy, but symptoms only appear in the fourth decade of life.

ThT 101: a primer on the use of thioflavin T to investigate amyloid formation.

Thioflavin T (ThT) has been widely used to investigate amyloid formation since 1989. While concerns have recently been raised about its use as a probe specific for amyloid, ThT still continues to be a very valuable tool for studying kinetic aspects of fibrillation and associated inhibition mechanisms. This review aims to provide a conceptual instruction manual, covering appropriate considerations and pitfalls related to the use of ThT.

Significance of symmetry in the nuclear spin Hamiltonian for efficient heteronuclear dipolar decoupling in solid-state NMR: A Floquet description of supercycled rCW schemes.

Symmetry plays an important role in the retention or annihilation of a desired interaction Hamiltonian in NMR experiments. Here, we explore the role of symmetry in the radio-frequency interaction frame Hamiltonian of the refocused-continuous-wave (rCW) pulse scheme that leads to efficient H heteronuclear decoupling in solid-state NMR. It is demonstrated that anti-periodic symmetry of single-spin operators (I, I, I) in the interaction frame can lead to complete annihilation of the H-H homonuclear dipolar coupling effects that induce line broadening in solid-state NMR experiments.

Parameter independent low-power heteronuclear decoupling for fast magic-angle spinning solid-state NMR.

Major advances have recently been made in the field of heteronuclear dipolar decoupling in solid-state nuclear magnetic resonance (NMR). These developments have improved the resolution and sensitivity of the NMR spectrum of spins coupled to protons. One such new scheme, denoted as rCW, has proven to be robust with practically no need for parameter optimization [A.

Reactive Center Loop Insertion in α-1-Antitrypsin Captured by Accelerated Molecular Dynamics Simulation.

Protease inhibition by metastable serine protease inhibitors (serpins) is mediated by one of the largest functional intradomain conformational changes known in biology. In this extensive structural rearrangement, protease-serpin complex formation triggers cleavage of the serpin reactive center loop (RCL), its subsequent insertion into central β-sheet A, and covalent trapping of the target protease. In this study, we present the first detailed accelerated molecular dynamics simulation of the insertion of the fully cleaved RCL in α-1-antitrypsin (αAT), the archetypal member of the family of human serpins.

Ligand Binding in the Extracellular Vestibule of the Neurotransmitter Transporter Homologue LeuT.

The human monoamine transporters (MATs) facilitate the reuptake of monoamine neurotransmitters from the synaptic cleft. MATs are linked to a number of neurological diseases and are the targets of both therapeutic and illicit drugs. Until recently, no high-resolution structures of the human MATs existed, and therefore, studies of this transporter family have relied on investigations of the homologues bacterial transporters such as the leucine transporter LeuT, which has been crystallized in several conformational states.

Highly efficient F heteronuclear decoupling in solid-state NMR spectroscopy using supercycled refocused-CW irradiation.

We present heteronuclear F refocused CW (rCW) decoupling pulse sequences for solid-state magic-angle-spinning NMR applications. The decoupling sequences have been designed specifically to ensure suppression of the pertinent C-F dipolar coupling interactions while simultaneously suppressing strong anisotropic chemical shift as well as homonuclear F-F dipolar coupling effects as typically present in perfluorated compounds. In an extensive numerical and experimental analysis using a rigid, organic solid as a model compound, it becomes evident that the supercycled rCW schemes markedly improve the decoupling efficiency, leading to substantial enhancements in resolution and sensitivity when compared to previous state-of-the-art methods.

Epigallocatechin Gallate Remodels Overexpressed Functional Amyloids in Pseudomonas aeruginosa and Increases Biofilm Susceptibility to Antibiotic Treatment.

Epigallocatechin-3-gallate (EGCG) is the major polyphenol in green tea. It has antimicrobial properties and disrupts the ordered structure of amyloid fibrils involved in human disease. The antimicrobial effect of EGCG against the opportunistic pathogen Pseudomonas aeruginosa has been shown to involve disruption of quorum sensing (QS).

Allosteric-Activation Mechanism of Bovine Chymosin Revealed by Bias-Exchange Metadynamics and Molecular Dynamics Simulations.

The aspartic protease, bovine chymosin, catalyzes the proteolysis of κ-casein proteins in milk. The bovine chymosin-κ-casein complex is of industrial interest as the enzyme is used extensively in the manufacturing of processed dairy products. The apo form of the enzyme adopts a self-inhibited conformation in which the side chain of Tyr77 occludes the binding site.

Handling the influence of chemical shift in amplitude-modulated heteronuclear dipolar recoupling solid-state NMR.

We present a theoretical analysis of the influence of chemical shifts on amplitude-modulated heteronuclear dipolar recoupling experiments in solid-state NMR spectroscopy. The method is demonstrated using the Rotor Echo Short Pulse IRrAdiaTION mediated Cross-Polarization ((RESPIRATION)CP) experiment as an example. By going into the pulse sequence rf interaction frame and employing a quintuple-mode operator-based Floquet approach, we describe how chemical shift offset and anisotropic chemical shift affect the efficiency of heteronuclear polarization transfer.

In situ high-resolution structure of the baseplate antenna complex in Chlorobaculum tepidum.

Photosynthetic antenna systems enable organisms harvesting light and transfer the energy to the photosynthetic reaction centre, where the conversion to chemical energy takes place. One of the most complex antenna systems, the chlorosome, found in the photosynthetic green sulfur bacterium Chlorobaculum (Cba.) tepidum contains a baseplate, which is a scaffolding super-structure, formed by the protein CsmA and bacteriochlorophyll a.

Mild heat treatments induce long-term changes in metabolites associated with energy metabolism in Drosophila melanogaster.

Heat-induced hormesis, the beneficial effect of mild heat-induced stress, increases the average lifespan of many organisms. Yet little is known about the mechanisms underlying this effect. We used nuclear magnetic resonance spectroscopy to investigate the long-term effects of repeated mild heat treatments on the metabolome of male Drosophila melanogaster.

Structural Basis for Simvastatin Competitive Antagonism of Complement Receptor 3.

The complement system is an important part of the innate immune response to infection but may also cause severe complications during inflammation. Small molecule antagonists to complement receptor 3 (CR3) have been widely sought, but a structural basis for their mode of action is not available. We report here on the structure of the human CR3 ligand-binding I domain in complex with simvastatin.

A Complex Dance: The Importance of Glycosaminoglycans and Zinc in the Aggregation of Human Prolactin.

The zinc binding hormone pituitary human prolactin (hPRL) is stored in secretory granules of specialized cells in an aggregated form. Glycosaminoglycans (GAGs) are anionic polysaccharides commonly associated with secretory granules, indicating their involvement in granule formation. Here we, for the first time, study the impact of GAGs in combination with Zn(2+) on the reversible hPRL aggregation across the pH range of 7.

How Glycosaminoglycans Promote Fibrillation of Salmon Calcitonin.

Glycosaminoglycans (GAGs) bind all known amyloid plaques and help store protein hormones in (acidic) granular vesicles, but the molecular mechanisms underlying these important effects are unclear. Here we investigate GAG interactions with the peptide hormone salmon calcitonin (sCT). GAGs induce fast sCT fibrillation at acidic pH and only bind monomeric sCT at acidic pH, inducing sCT helicity.

Incorporation of β-Silicon-β3-Amino Acids in the Antimicrobial Peptide Alamethicin Provides a 20-Fold Increase in Membrane Permeabilization.

Incorporation of silicon-containing amino acids in peptides is known to endow the peptide with desirable properties such as improved proteolytic stability and increased lipophilicity. In the presented study, we demonstrate that incorporation of β-silicon-β3-amino acids into the antimicrobial peptide alamethicin provides the peptide with improved membrane permeabilizing properties. A robust synthetic procedure for the construction of β-silicon-β3-amino acids was developed and the amino acid analogues were incorporated into alamethicin at different positions of the hydrophobic face of the amphipathic helix by using SPPS.

Theranostic tumor targeted nanoparticles combining drug delivery with dual near infrared and F magnetic resonance imaging modalities.

Combining imaging and drug delivery of "theranostic" nanoparticles has enabled concurrent diagnosis and therapy of diseases. Here, we describe a novel theranostic system that combines two imaging tracers, perfluorooctyl bromide (PFOB) for F magnetic resonance imaging (MRI) and indocyanine green (ICG) for near infrared (NIR) imaging, with the chemotherapeutic agent doxorubicin (Dox) into poly (lactic-co-glycolic acid)- poly (ethylene-glycol)-folate (PLGA-PEG-folate) nanoparticles. Cell culture studies using flow cytometry, confocal laser scanning microscope imaging, and F MRI showed enhanced uptake of nanoparticles via folate receptors expressed on human nasopharyngeal epidermal carcinoma (KB) cells.

Epigallocatechin Gallate Remodels Fibrils of Lattice Corneal Dystrophy Protein, Facilitating Proteolytic Degradation and Preventing Formation of Membrane-Permeabilizing Species.

Lattice corneal dystrophy is associated with painful recurrent corneal erosions and amyloid corneal opacities induced by transforming growth factor β-induced protein (TGFBIp) that impairs vision. The exact mechanism of amyloid fibril formation in corneal dystrophy is unknown but has been associated with destabilizing mutations in the fourth fasciclin 1 (Fas1-4) domain of TGFBIp. The green tea compound epigallocatechin gallate (EGCG) has been found to inhibit fibril formation of various amyloidogenic proteins in vitro.

Conformational Dynamics of the Human Islet Amyloid Polypeptide in a Membrane Environment: Toward the Aggregation Prone Form.

Human islet amyloid polypeptide (hIAPP) is a 37-residue peptide hormone, which upon misfolding changes from the physiologically active monomer into pathological amyloid fibril aggregates in the pancreas of type 2 diabetes mellitus patients. During this process, the insulin-producing pancreatic β-cells are damaged; however, the underlying mechanism of this mode of cytotoxicity remains elusive. It is known that anionic lipids accelerate amyloid fibril formation, implicating the importance of the cellular membrane in the process, and that a pH close to the level in the β-cell secretory granules (pH 5.

Relative merits of rCW(A) and XiX heteronuclear spin decoupling in solid-state magic-angle-spinning NMR spectroscopy: A bimodal Floquet analysis.

We present a bimodal Floquet analysis of the recently introduced refocused continuous wave (rCW) solid-state NMR heteronuclear dipolar decoupling method and compare it with the similar looking X-inverse X (XiX) scheme. The description is formulated in the rf interaction frame and is valid for both finite and ideal π pulse rCW irradiation that forms the refocusing element in the rCW scheme. The effective heteronuclear dipolar coupling Hamiltonian up to first order is described.