A valine-to-lysine substitution at position 210 induces structural conversion of prion protein into a β-sheet rich oligomer

Double-Network Hydrogel with Strengthened Mechanical Property for Controllable Release of Antibacterial Peptide

Developing double-network (DN) hydrogels with high mechanical properties and antibacterial efficacy to combat multidrug-resistant bacterial infections and serve as scaffolds for cell culture still remains an ongoing challenge. In this study, an ion-responsive antibacterial peptide (AMP) (C16-WIIIKKK, termed as IK7) was synergistically combined with a photoresponsive gelatin methacryloyl (GelMA) polymer to fabricate a biocompatible DN hydrogel. The GelMA-IK7 DN hydrogel showed enhanced mechanical properties in contrast to the individual IK7 and GelMA hydrogels and demonstrated substantial antibacterial efficacy. Further investigations revealed that the DN hydrogel effectively inhibited bacterial growth by the controlled and sustained release of the IK7 peptide. In addition, the formation of the DN hydrogel was also found to protect AMP IK7 from rapid degradation by proteinase K. Our findings suggested that the developed GelMA-IK7 DN hydrogel holds great potential for next-generation antibacterial hydrogels for three-dimensional cell culture and tissue regeneration.

Targeting the binding pocket of the fluorophore 8-anilinonaphthalene-1-sulfonic acid in the bacterial enzyme MurA

8-Anilinonaphthalene-1-sulfonic acid (ANS) has been extensively used as a fluorescent probe to detect conformational changes of proteins. It has been cocrystallized with several of the proteins it is used to monitor, including the bacterial cell wall synthesis enzyme MurA. MurA catalyzes the first committed step of peptidoglycan biosynthesis, converting UDP-N-acetylglucosamine (UDP-GlcNAc) into enolpyruvyl UDP-GlcNAc. It has been reported before that ANS binds to MurA from Enterobacter cloacae without inhibiting the enzyme's activity up to a concentration of 1 mM ANS. In this study, we present evidence that ANS inhibits the activity of several isoforms of MurA with IC50 values of 18, 22, and 31 µM against wild-type Escherichia coli, C115D E. coli, and E. cloacae MurA, respectively. This prompted us to test a larger series of structural analogs of ANS for the inhibition of these MurA enzymes, which led to the discovery of compound 26. This ANS analog showed enhanced inhibition of MurA (WT and C115D MurA from E. coli, and E. cloacae MurA) with IC50 values of 2.7, 10, and 14 µM, respectively. Based on our results, the ANS binding pocket was identified as a novel target site for the development of potential antibiotics.

Monomeric a-synuclein (aS) inhibits amyloidogenesis of human prion protein (hPrP) by forming a stable aS-hPrP hetero-dimer

Intermolecular interaction between hPrP and αS was investigated using high-speed atomic force microscopy, dynamic light scattering, and nuclear magnetic resonance. We found that hPrP spontaneously gathered and naturally formed oligomers. Upon addition of monomer αS with a disordered conformation, poly-dispersive property of hPrP was lost, and hetero-dimer formation started quite coherently, and further oligomerization was not observed. Solution structure of hPrP-αS dimer was firstly characterized using hetero-nuclear NMR spectroscopy. In this hetero-dimeric complex, C-terminal helical region of hPrP was in the molten-globule like state, while specific sites including hot spot and C-terminal region of αS selectively interacted with hPrP. Thus αS may suppress amyloidogenesis of hPrP by trapping the hPrP intermediate by the formation of a stable hetero-dimer with hPrP.

Abbreviations: hPrP, human prion protein of amino acid residues of 23-231; PrP^C, cellular form of prion protein; PrP^Sc, scrapie form of prion protein, HS-AFM; high speed atomic force microscopy; αS, α-synuclein; DLS, dynamic light scattering

Synthesis and Spectral Properties of 8-Anilinonaphthalene-1-sulfonic Acid (ANS) Derivatives Prepared by Microwave-Assisted Copper(0)-Catalyzed Ullmann Reaction

For decades, the dye 8-anilino-1-naphthalenesulfonic acid (ANS) has been used to study biological systems due to its environmentally sensitive fluorescent nature and propensity to bind to hydrophobic pockets of proteins. However, the syntheses of ANS and its derivatives have been low yielding, requiring harsh reaction conditions and long reaction times. We have developed efficient, mild microwave-assisted copper(0)-catalyzed Ullmann coupling conditions to synthesize ANS derivatives with yields of up to 74%. Many of these derivatives have spectral properties distinct from ANS, including improved and diminished quantum yields, different absorption and emission maxima, and complete loss of fluorescence. ANS derivatives with these unique fluorescence properties are useful tools to study biological systems.

Synchrotron radiation-based FTIR spectro-microscopy of the brainstem of the hSOD1 G93A rat model of amyotrophic lateral sclerosis

Pathological mechanisms in amyotrophic lateral sclerosis (ALS), a fatal neurodegenerative disease, are still poorly understood. One subset of familial ALS cases is caused by mutations in the metallo-enzyme copper-zinc superoxide dismutase (SOD1), increasing the susceptibility of the SOD1 protein to form insoluble intracellular aggregates. Here, we employed synchrotron radiation-based Fourier transform infrared spectroscopy and microscopy to investigate brainstem cross-sections from the transgenic hSOD1 G93A rat model of ALS that overexpresses human-mutated SOD1. We compared the biomacromolecular organic composition in brainstem tissue cross-sections of ALS rats and their non-transgenic littermates (NTg). We demonstrate that the proteins and especially their antiparallel β-sheet structure significantly differed in all three regions: the facial nucleus (FN), the gigantocellular reticular nucleus (GRN) and the trigeminal motor nucleus (TMN) in the brainstem tissue of ALS rats. The protein levels varied between different brainstem areas, with the highest concentration observed in the region of the FN in the brainstem tissue of NTg animals. Furthermore, the concentration of lipids and esters was significantly decreased in the TMN and FN of ALS animals. A similar pattern was detected for choline and phosphate assigned to nucleic acids with the highest concentrations in the FN of NTg animals. The spectroscopic analysis showed significant differences in phosphates, amide and lipid structure in the FN of NTg animals in comparison with the same area of ALS rats. These results show that the hG93A SOD1 mutation causes metabolic cellular changes and point to a link between bioorganic composition and hallmarks of protein aggregation.