Some new water soluble complexes [N,N′-bis{5-[(triphenyl phosphonium chloride)-methyl]salicylidine}-3,4-diaminopyridine] M(II), which are formulated as nano-[Zn(5-CH₂PPh₃-3,4-salpyr)](ClO₄)₂ (1), [Zn(5-CH₂PPh₃-3,4-salpyr)](ClO₄)₂ (2), nano-[Ni(5-CH₂PPh₃-3,4-salpyr)](ClO₄)₂ (3), [Ni(5-CH₂PPh₃-3,4-salpyr)](ClO₄)₂ (4), and [N,N′-bis{5-[(triphenyl phosphonium chloride)-methyl]salicylidine}-2,3-diaminopyridine]Ni(II) [Ni(5-CH₂PPh₃-2,3-salpyr)](ClO₄)₂ (5) have been isolated and characterized by elemental analysis, FT-IR, ¹H NMR, ¹³C NMR, ³¹P NMR, and UV-vis spectroscopy. The morphology and size of the nano complexes were determined using FE-SEM and TEM. In vitro DNA binding studies were investigated by UV-vis absorption spectroscopy, viscosity measurements, CD spectroscopy, cyclic voltammetry, emission spectra and gel electrophoresis, which suggest that the metal complexes act as efficient DNA binders. The absorption spectroscopy of the compounds with DNA reveals that the DNA binding affinity (K_b) has this order: 3 > 4 > 5 > 1 > 2 > Ligand. The metal complexes show DNA binding stronger than the ligand, which is expected due to the nature of the metal. The nano complexes display DNA binding stronger than the other complexes which is related to the effect of size on binding affinity and the Ni(II) complexes reveal DNA binding stronger than the corresponding Zn(II) analogues, which is expected due to their z* effect and geometry. The prominent double strand DNA cleavage abilities of compound 3 are observed in the absence of H₂O₂ with efficiencies of more than 50% even at 70 μM complex concentration. Surprisingly, Zn(II) complexes (compounds 1 & 2) exhibit a higher cytotoxicity (IC₅₀: 7.3 & 10.9 μM at 24 h; IC₅₀: 4.6 & 8.7 μM at 48 h) against human hepatoma (HepG2) and HeLa cell lines than the Ni(II) complexes (compounds 3, 4 & 5) and 5-fluorouracil as control in spite of their inability to cleave DNA. Finally, DNA binding interactions were performed by docking studies. Density functional theory (DFT) studies were performed using the GAUSSIAN 03 program. The DFT method with B3LYP functional, LANL2DZ basis set for metal centers and 6-311g* for other atoms was used. The synthesized compounds and DNA were simulated by molecular docking to explore more details of the ligands conformation and their orientations in the active site of the receptor.

The production of a protease was investigated under conditions of high salinity by the moderately halophilic bacterium Halobacillus karajensis strain MA-2 in a basal medium containing peptone, beef extract, maltose and NaCl when the culture reached the stationary growth phase. Effect of various temperatures, initial pH, salt and different nutrient sources on protease production revealed that the maximum secretion occurred at 34°C, pH 8.0–8.5, and in the presence of gelatin. Replacement of NaCl by various concentrations of sodium nitrate in the basal medium also increased the protease production. The secreted protease was purified 24-fold with 68% recovery by a simple approach including a combination of acetone precipitation and Q-Sepharose ion exchange chromatography. The enzyme revealed a monomeric structure with a relative molecular mass of 36 kDa by running on SDS-PAGE. Maximum caseinolytic activity of the enzyme was observed at 50°C, pH 9.0 and 0.5 M NaCl, although at higher salinities (up to 3 M) activity still remained. The maximum enzyme activity was obtained at a broad pH range of 8.0–10.0, with 55 and 50% activity remaining at pH 6 and 11, respectively. Moreover, the enzyme activity was strongly inhibited by phenylmethylsulfonyl fluoride (PMSF), Pefabloc SC and EDTA; indicating that it probably belongs to the subclass of serine metalloproteases. These findings suggest that the protease secreted by Halobacillus karajensis has a potential for biotechnological applications from its haloalkaline properties point of view.

A novel moderately halophilic, Gram-negative, curved-rod-shaped bacterium, designated strain AF-2004^T, was isolated from Bakhtegan Lake, a hypersaline lake with 17 % (w/v) total salt located in the southern region of Iran. Strain AF-2004^T was a facultative anaerobe, motile by one polar flagellum, non-sporulating and oxidase- and catalase-positive. It grew at salinities of 1–17 % (w/v) NaCl, showing optimal growth at 5 % (w/v). Growth occurred at 10.0–45.0 °C and pH 5.0–9.5, with optimum growth at 32.0–35.0 °C and pH 8.0–8.5. Phylogenetic analyses based on 16S rRNA gene sequence comparisons indicated that strain AF-2004^T is a member of the genus Salinivibrio. Strain AF-2004^T had C_18 : 1ω7c (31.6 %), C_16 : 1ω7c (22.1 %) and C_16 : 0 (20.7 %) as the predominant fatty acids and Q-8 as the major respiratory lipoquinone. The DNA G+C content was 49.5 mol%, which is in the range of values for members of the genus Salinivibrio. On the basis of differentiation from Salinivibrio costicola by phenotypic and chemotaxonomic characteristics, 16S rRNA sequence analysis and DNA–DNA relatedness, it is proposed that strain AF-2004^T (=DSM 19052^T =CIP 109598^T) should be placed in the genus Salinivibrio as the type strain of a novel species, Salinivibrio proteolyticus sp. nov.