Structure-Activity Relationship Study of Helix-Stabilized Antimicrobial Peptides Containing Nonproteinogenic Amino Acids.

Helical amphipathic peptides containing cationic and hydrophobic amino acid residues can possess potent antimicrobial activity against both Gram-positive and Gram-negative bacteria. In this study, several amphipathic peptides with enhanced helical structures containing nonproteinogenic amino acids were designed, and the relationships between the antimicrobial activity, hemolytic activity, and cytotoxicity were evaluated. In particular, the effect on the antimicrobial activity and cytotoxicity of the number and position of stapling structures introduced into the sequence was investigated. Peptide stp1 containing α,α-disubstituted amino acids showed potent antimicrobial activity against multidrug-resistant bacteria (MDRP, SP45, and Staphylococcus aureus) without causing appreciable hemolytic activity or cytotoxicity. The cytotoxicity was found to be somewhat correlated to the hydrophobicity of the peptides.

Novel Defense by Metallothionein Induction Against Cognitive Decline: From Amyloid ß1-42-Induced Excess Zn2+ to Functional Zn2+ Deficiency.

The role of metallothioneins (MTs) in cognitive decline associated with intracellular Zn2+ dysregulation remains unclear. Here, we report that hippocampal MT induction defends cognitive decline, which was induced by amyloid ß1-42 (Aß1-42)-mediated excess Zn2+ and functional Zn2+ deficiency. Excess increase in intracellular Zn2+, which was induced by local injection of Aß1-42 into the dentate granule cell layer, attenuated in vivo perforant pathway LTP, while the attenuation was rescued by preinjection of MT inducers into the same region. Intraperitoneal injection of dexamethasone, which increased hippocampal MT proteins and blocked Aß1-42-mediated Zn2+ uptake, but not Aß1-42 uptake, into dentate granule cells, also rescued Aß1-42-induced impairment of memory via attenuated LTP. The present study indicates that hippocampal MT induction blocks rapid excess increase in intracellular Zn2+ in dentate granule cells, which originates in Zn2+ released from Aß1-42, followed by rescuing Aß1-42-induced cognitive decline. Furthermore, LTP was vulnerable to Aß1-42 in the aged dentate gyrus, consistent with enhanced Aß1-42-mediated Zn2+ uptake into aged dentate granule cells, suggesting that Aß1-42-induced cognitive decline, which is caused by excess intracellular Zn2+, can more frequently occur along with aging. On the other hand, attenuated LTP under functional Zn2+ deficiency in dentate granule cells was also rescued by MT induction. Hippocampal MT induction may rescue cognitive decline under lack of cellular transient changes in functional Zn2+ concentration, while its induction is an attractive defense strategy against Aß1-42-induced cognitive decline.

Inhalation Properties and Stability of Nebulized Naked siRNA Solution for Pulmonary Therapy.

The use of naked unmodified small interfering RNA (N-siRNA) without vector has previously been investigated as a pulmonary therapy. However, little is known regarding stabilities and aerodynamic particle sizes of N-siRNA-containing droplets; nebulizers have not yet been optimized for N-siRNA solutions. Thus, in this study, we investigated the feasibility of inhaled N-siRNA solutions for pulmonary therapy using nebulization. Various nebulizers and N-siRNA concentrations were assessed in terms of siRNA integrity after nebulization, and inhalation properties including aerodynamic particle size were examined. In comparison with ultrasonic-, air-jet-, and vibrating-mesh nebulizers, N-siRNA integrity was not affected by nebulization. Thus, in further experiments, performances of N-siRNA aerosols with different nebulizers and N-siRNA concentrations were evaluated and screened using an aerodynamic particle sizer (APS) which employed the time-of-flight principle or a cascade impactor. Mean mass aerodynamic diameters of N-siRNA-containing droplets from vibrating-mesh nebulizers tended to decrease with increasing N-siRNA concentrations, reflecting the influence of N-siRNA solutions on surface tension, as indicated by contact angles. These data indicate the utility of APS instruments for investigating the nebulized characteristics of expensive drugs including siRNAs and may facilitate the development of N-siRNA inhalation formulations.

Multiple crystal forms of N,N'-diacetylchitobiose deacetylase from Pyrococcus furiosus.

Native N,N'-diacetylchitobiose deacetylase from Pyrococcus furiosus (Pf-Dac) and its selenomethionine derivative (Se-Pf-Dac) were crystallized and analyzed in the presence and absence of cadmium ion. The four crystal structures fell into three different crystal-packing groups, with the cadmium-free Pf-Dac and Se-Pf-Dac belonging to the same space group, with homologous unit-cell parameters. The crystal structures in the presence of cadmium contained distorted octahedral cadmium complexes coordinated by three chlorides, two O atoms and an S or Se atom from the N-terminal methionine or selenomethionine, respectively. The N-terminal cadmium complex was involved in crystal contacts between symmetry-related molecules through hydrogen bonding to the N-termini. While all six N-termini of Se-Pf-Dac were involved in cadmium-complex formation, only two of the Pf-Dac N-termini participated in complex formation in the Cd-containing crystal, resulting in different crystal forms. These differences are discussed in light of the higher stability of the Cd-Se bond than the Cd-S bond. This work provides an example of the contribution of cadmium towards determining protein crystal quality and packing depending on the use of the native protein or the selenomethionine derivative.

Expression from engineered Escherichia coli chromosome and crystallographic study of archaeal N,N'-diacetylchitobiose deacetylase.

UNLABELLED: In order to develop a structure-based understanding of the chitinolytic pathway in hyperthermophilic Pyrococcus species, we performed crystallographic studies on N,N'-diacetylchitobiose deacetylases (Dacs) from Pyrococcus horikoshii (Ph-Dac) and Pyrococcus furiosus (Pf-Dac). Neither Ph-Dac nor Pf-Dac was expressed in the soluble fraction of Escherichia coli harboring the expression plasmid. However, insertion of the target genes into the chromosome of E. coli yielded the soluble recombinant protein. The purified Pyrococcus Dacs were active and thermostable up to 85 °C. The crystal structures of Ph-Dac and Pf-Dac were determined at resolutions of 2.0 Å and 1.54 Å, respectively. The Pyrococcus Dac forms a hexamer composed of two trimers. These Dacs are characterized by an intermolecular cleft, which is formed by two polypeptides in the trimeric assembly. In Ph-Dac, catalytic Zn situated at the end of the cleft is coordinated by three side chain ligands from His44, Asp47, and His155, and by a phosphate ion derived from the crystallization reservoir solution. We considered that the bound phosphate mimicked the tetrahedral oxyanion, which is an intermediate of hydrolysis of the N-acetyl group, and proposed an appropriate reaction mechanism. In the proposed mechanism, the N(ε) atom of His264 (from the adjacent polypeptide in the Ph-Dac sequence) is directly involved in the stabilization of the oxyanion intermediate. Mutation analysis also indicated that His264 was essential to the catalysis. These factors give the archaeal Dacs an unprecedented active site architecture a Zn-dependent deacetylases. DATABASE: Structural data are available in the Protein Data Bank database under accession numbers 3WL3, 3WL4, and 3WE7.

Signal amplified two-dimensional photonic crystal biosensor immobilized with glyco-nanoparticles.

A two-dimensional, glycopolymer-immobilized, photonic crystal (PhC) biosensor was developed for the detection of proteins. Glycopolymers with different conformations, homopolymers and sugar-incorporating nanoparticles were immobilized on the PhC using intermediate succinimide-containing polymers and proteins. The surface modification was analyzed in detail, and the sugar-protein interaction was detected by monitoring changes in the reflection intensity that was expressed by the two-dimensional PhC. The surface modifications were performed successfully, and specific interactions were detected between the glycopolymers and the proteins. Stronger bonds were present between the glycopolymers and the target proteins than between the glycopolymers and the monovalent sugar, because of a clustering effect. The sugar-incorporating nanoparticles showed a larger binding capacity compared with the homopolymers, and low protein concentrations (with a detection limit of 6.0 ng mL-1) were detected using the sugar-incorporating nanoparticle-immobilized PhC. The detection limit of the developed biosensor was lower than that of surface plasmon resonance sensor (1.43 µg mL-1). The results of this study indicated the potential of the developed biosensor for the detection of a variety of biomolecules.