Antibacterial mechanism and structure-activity relationships of Bombyx mori cecropin A.

Bombyx mori cecropin A (Bmcecropin A) has antibacterial, antiviral, anti-filamentous fungal and tumour cell inhibition activities and is considered a potential succedaneum for antibiotics. We clarified the antibacterial mechanism and structure-activity relationships and then directed the structure-activity optimization of Bmcecropin A. Firstly, we found Bmcecropin A shows a strong binding force and permeability to cell membranes like a detergent; Bmcecropin A could competitively bind to the cell membrane with the cell membrane-specific dye DiI, then damaged the membrane for the access of DiI into the cytoplasm and leading to the leakage of electrolyte and proteins. Secondly, we found Bmcopropin A could also bind to and degrade DNA; furthermore, DNA library polymerase chain reaction (PCR) results indicated that Bmcecropin A inhibited DNA replication by non-specific binding. In addition, we have identified C-terminus amidation and serine-lysine- glycine (SLG) amino acids of Bmcecropin A played critical roles in the membrane damage and DNA degradation. Based on the above results, we designed a mutant of Bmcecropin A (E9 to H, D17 to K, K33 to A), which showed higher antibacterial activity, thermostability and pH stability than ampicillin but no haemolytic activity. Finally, we speculated that Bmcecropin A damaged the cell membrane through a carpet model and drew the schematic diagram of its antibacterial mechanism, based on the antibacterial mechanism and the three-dimensional configuration. These findings yield insights into the mechanism of antimicrobial peptide-pathogen interaction and beneficial for the development of new antibiotics.

Complete mitochondrial genome of the mulberry psyllid Paurocephala sauteri Enderlein (Hemiptera: Psyllidae) and phylogenetic analysis.

Paurocephala sauteri (Enderlein, 1914) (Hemiptera: Psyllidae) is a species of a psyllid distributed in Asia. Mulberry is the only known host for P. sauteri until now. The complete mitogenome of P. sauteri (accession number: MT759765) 14,963 bp in size, including 13 protein-coding genes, 22 transfer RNAs, and two ribosomal RNAs genes. The base composition of the whole P. sauteri mitogenome is 40.26% for A, 7.86% for G, 34.07% for T, and 11.81% for C, with a high AT bias of 80.33%. The mitochondrial genome of P. sauteri was sequenced and annotated as the first representative of family Paurocephalidae. The present data could contribute to a detailed phylogeographic analysis of this valuable economic insect for further study in differentiating closely related species.

C-type lectin 5, a novel pattern recognition receptor for the JAK/STAT signaling pathway in Bombyx mori.

The Janus kinase/signal transducer and activator of transcription cascade transduction (JAK/STAT) signaling pathway is highly conserved in mammals, but the pattern recognition receptors (PRRs) and their functions are unclear. We found that the expression pattern of Bombyx mori C-type lectin 5 (BmCTL 5) had a synergy relevance with the JAK/STAT signaling pathway against Beauveria bassiana. An RNAi assay, subcellular localization analysis, yeast two-hybrid technique, protein recruitment experiment and pathogen infection tests were used to explore the roles of BmCTL 5 in the JAK/STAT signaling pathway. Knock-down of the BmCTL 5 suppressed the JAK/STAT signaling pathway and the PO cascade of nodule melanization. BmCTL 5 is located in the cytomembrane and interacted with BmHOP both in yeast and B. mori ovary cells N (BmN cells). BmCTL 5 and the JAK/STAT signaling pathway was activated by B. bassiana but only slightly activated by B. mori cytoplasmic polyhedrosis virus (BmCPV), Nosema bombycis and bacteria LPS. These findings suggest that BmCTL 5 might be an important PRR for the JAK/STAT signaling pathway and may mediate the nodule melanization for fungi infection. These data provide insights into the immune mechanism of the JAK/STAT signaling pathway in insects and aid understanding of the mechanism of the JAK/STAT signaling pathway and adaptive immune systems in mammals.

Ratiometric phosphorescence imaging of Hg(II) in living cells based on a neutral iridium(III) complex.

In this work, a neutral iridium(III) complex [Ir(bt)(2)(acac)] (Hbt = 2-phenylbenzothiazole; Hacac = acetylacetone) has been realized as a Hg(II)-selective sensor through UV-vis absorption, phosphorescence emission, and electrochemical measurements and was further developed as a phosphorescent agent for monitoring intracellular Hg(II). Upon addition of Hg(II) to a solution of [Ir(bt)(2)(acac)], a noticeable spectral blue shift in both absorption and phosphorescent emission bands was measured. (1)H NMR spectroscopic titration experiments indicated that coordination of Hg(II) to the complex induces fast decomposition of [Ir(bt)(2)(acac)] to form a new complex, which is responsible for the significant variations in optical and electrochemical signals. Importantly, cell imaging experiments have shown that [Ir(bt)(2)(acac)] is membrane permeable and can be used to monitor the changes in Hg(II) levels within cells in a ratiometric phosphorescence mode.

Phosphorescent iridium(III) complex with an N

Phosphorescent iridium(III) complexes have been attracting increasing attention in applications as luminescent chemosensors. However, no instance of an iridium(III) complex being used as a molecular logic gate has hitherto been reported. In the present study, two iridium(III) complexes, [Ir(ppy)(2)(PBT)] and [Ir(ppy)(2)(PBO)], have been synthesized (PBT, 2-(2-Hydroxyphenyl)-benzothiazole; PBO, 2-(2-hydroxyphenyl)-benzoxazole), and their chemical structures have been characterized by single-crystal X-ray analysis. Theoretical calculations and detailed studies of the photophysical and electrochemical properties of these two complexes have shown that the N^O ligands dominate their luminescence emission properties. Moreover, [Ir(ppy)(2)(PBT)], containing a sulfur atom in the N^O ligand, can serve as a highly selective chemodosimeter for Hg(2+) with ratiometric and naked-eye detection, which is associated with the dissociation of the N^O ligand PBT from the complex. Furthermore, complex [Ir(ppy)(2)(PBT)] has been further developed as an AND and INHIBIT logic gate with Hg(2+) and histidine as inputs.

A cyclometalated iridium(III) complex with enhanced phosphorescence emission in the solid state (EPESS): synthesis, characterization and its application in bioimaging.

Iridium(III) complexes with intense phosphorescence in solution have been widely applied in organic light-emitting diodes, chemosensors and bioimaging. However, little attention has been paid to iridium(III) complexes showing weak phosphorescence in solution and enhanced phosphorescence emission in the solid state (EPESS). In the present study, two ß-diketonate ligands with different degrees of conjugation, 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone (HL1) and 1-phenyl-3-methyl-4-phenylacetyl-5-pyrazolone (HL2), have been synthesized to be used as ancillary ligands for two iridium(III) complexes, Ir(ppy)(2)(L1) and Ir(ppy)(2)(L2) (Hppy = 2-phenylpyridine). The two complexes have been characterized by single-crystal X-ray crystallography, (1)H NMR and elemental analysis. Interestingly, Ir(ppy)(2)(L1) is EPESS-active whereas Ir(ppy)(2)(L2) exhibits moderately intense emission both in solution and as a neat film, indicating that the degree of conjugation of the ß-diketone ligands determines the EPESS-activity. The single-crystal X-ray analysis has indicated that there are π-π interactions between the adjacent ppy ligands in Ir(ppy)(2)(L1) but not in Ir(ppy)(2)(L2). Finally, EPESS-active Ir(ppy)(2)(L1) has been successfully embedded in polymer nanoparticles and used as a luminescent label in bioimaging.

Reply to comment on 'aggregation-induced phosphorescent emission (AIPE) of iridium(III) complexes': origin of the enhanced phosphorescence.

An obvious enhanced phosphorescence emission in the solid state (EPESS) was observed for two iridium(III) complexes with restricted (even fixed) intramolecular rotational motion, which is contrary to the opinion ("restricted intramolecular rotational motion as the origin of EPESS") of Park et al., and our observation confirmed that the pi-pi stacking of adjacent pyridyl rings of ppy ligands played a key role in EPESS.

Unique formation of two high-nuclearity metallamacrocycles from a mononuclear complex [Zn(dmpzdtc)2] (dmpzdtc=3,5-dimethylpyrazole-1-dithiocarboxylate) via CS2 elimination.

Dissolution of a mononuclear complex [Zn(dmpzdtc)2] in BrCH2CH2Br or DMF saturated with water followed by CS2 elimination led to the formation of two unique high-nuclearity metallamacrocyclic complexes, [Zn4(micro-dmpz)6(micro-OH)2]2 and [Zn4(micro-dmpz)6(micro-OH)2]4.