Facile synthesis,physiochemical characterization and bio evaluation of sulfadimidine capped cobalt nanoparticles

Due to their less expensive, environment friendly nature, and their natural abundance of cobalt have attained more significant attention for the synthesis of cobalt nanoparticles. In the present study, we report the facile synthesis of cobalt nanoparticles using a straight forward chemical reduction approach of cobalt chloride with sodium borohydride and capping of sulfadimidine. sulfadimidine has strong capping eligibility on the surface of nanoparticles due to its chemical stability and is an applicable as stabilizer due to the existence of an amine bond. The as-synthesized sulfadimidine stabilized cobalt nanoparticles (Co-SD NPs) were characterized by using various spectroscopic and microscopic analysis like UV–Visible spectroscopy (UV–Vis), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), High-Resolution Transmission electron microscopy (HR-TEM), and Fourier-transform infrared spectroscopy (FT-IR). The XRD analysis exhibited the triclinic crystal structure of the as-synthesized cobalt nanoparticles and FT-IR analysis confirmed the capping of sulfadimidine via monodentate interaction. The HR-TEM analysis displayed the size of the cobalt nanoparticles approximately 3–5 nm. The antibacterial properties of the sulfadimidine stabilized cobalt nanoparticles (Co-SD NPs) were tested against various bacterial strains such as Klebsiella pneumonia (KP), Escherichia coli (EC) and Pseudomonas syringae (PS) by using agar disc diffusion approach. The results of sulfadimidine capped cobalt nanoparticles displayed the enhanced biological properties against the tested gram-negative bacteria.     

Synthesis, characterisation and substitution kinetics of unusually labile trans-[Co(tmen)(diamine)Cl2] complexes

The mixed diamine complexes trans-[Co(tmen)(diamine)Cl₂]⁺ have been synthesised (tmen = NH₂C(Me)₂C(Me)₂NH₂; diamine = en = NH₂(CH₂)₂NH₂, and ibn = NH₂C(Me)₂CH₂NH₂). Replacement of one en ligand in trans-[Co(en)₂Cl₂]⁺ by one tmen ligand engenders an enormous rate enhancement (2000-fold) for acid hydrolysis. Solvolysis rates have been measured in Me₂SO and DMF for these complexes and also trans-[Co(tmen)₂Cl₂]⁺ which is more reactive again (10⁴-fold). The measured reactivities in DMF at 2 °C establish that the kinetic effect of replacing each en by tmen is incremental, and the extreme base catalysed racemisation rate for (+)-[Co(tmen)₃]³⁺ can now be explained on this basis.     

Does cobalt really bind tightly to hemocyanin active sites?

The analysis of Co(II)-apoHc complexes of two arthropodan species (freshwater crayfish): Orconectes limosus and Astacus astacus enabled to reach some conclusions about possible cobalt binding sites in the hemocyanin molecules. The occurrence of binding sites for Co(II) at sites other than the active center has been demonstrated. We excluded the possibility of strong binding of EDTA-non-removable cobalt ions in the binding sites occupied by copper. There were no differences between apoHc and the Co(II)apoHc complex in terms of the amount of bound Cu(I) ions and the kinetics of Cu(I) ion reconstitution.Abbreviations He hemocyanin - apoHc apohemocyanin - oxyHc oxyhemocyanin - Co-Hc hemocyanin complex with cobalt ions Offprint requests to: E. Serafln     

Protoporphyrin‐based eggshell pigmentation predicts hatching success and offspring sex ratio in the barn swallow

Inter‐ and intraspecific variation in eggshell colouration has long fascinated evolutionary biologists. Among species, such variation may accomplish different functions, the most obvious of which is camouflage and background matching. Within species, it has been proposed that inter‐female variation in eggshell pigmentation patterns can reflect egg, maternal or paternal traits and hence may provide cues to conspecifics about egg, maternal or paternal phenotypic quality. However, the relationship between protoporphyrin‐based eggshell pigmentation and egg or maternal/paternal traits appears to be highly variable among species. We investigated patterns of intraspecific variation in Eurasian barn swallow Hirundo r. rustica protoporphyrin‐based eggshell pigmentation, and analysed its association with egg and clutch characteristics, maternal/paternal phenotypic traits and parental feeding effort. Eggshell pigmentation pattern significantly varied between breeding colonies, was significantly repeatable in first clutches laid by the same females in different years (intraclass correlation coefficient ranging between 0.56 and 0.63), but it was not significantly associated with egg traits, such as position in the laying sequence, egg mass, yolk testosterone concentration and antioxidant capacity. It was weakly or non‐significantly associated with female and male traits (sexual ornaments), but females laying darker (higher pigment intensity) first clutches had higher hatching success, suggesting that eggshell pigment intensity may predict fitness. Male nestling feeding effort was not predicted by eggshell pigmentation. In addition, females with darker breast plumage colouration (a melanin‐based trait related to fitness) laid highly protoporphyrin‐covered eggs, suggesting the presence of a previously unappreciated link between protoporphyrin biosynthesis and plumage melanisation. Moreover, the proportion of male offspring increased in clutches originating from highly protoporphyrin‐covered eggs, suggesting that parents could acquire visual cues about their future brood sex composition before egg hatching. Our results support the idea that intraspecific signalling via eggshell pigmentation is a species‐specific rather than a general feature of avian taxa.     

Photodynamics of Porphyric Insecticides

The discovery of porphyric insecticides was a direct fallout of the discovery and development of photodynamic herbicides. Tetrapyrrole-dependent photodynamic herbicides are compounds that force green plants to accumulate undesirable amounts of metabolic intermediates of the chlorophyll and heme metabolic pathways, namely, tetrapyrroles. In light, the accumulated tetrapyrroles photosensitize the formation of singlet oxygen that kills treated plants by oxidation of their cellular membranes. Demonstration of the potential for tetrapyrrole accumulation in insects was achieved by spraying T. ni larvae with δ-aminolevulinic acid (ALA) and 2,2-dipyridyl (Dpy). Treated larvae were placed overnight in darkness at 28°C in order to allow for tetrapyrrole accumulation. Extraction of treated, dark-incubated larvae with ammoniacal acetone, followed by spectrofluorometric examination of the larval extract, revealed the accumulation of massive amounts of protoporphyrin IX (Proto). A high degree of correlation was observed between Proto accumulation in darkness and larval death in the light. A few hours after exposure to light, the larvae became sluggish and flaccid due to loss of body fluids. Death was accompanied by extensive desiccation. Because control of insects by ingestion is as viable an option as control by spraying, and offers certain advantages under household conditions, studies were conducted to determine whether combinations of ALA and porphyric insecticide modulators would be effective if ingested with the food. The effect of ALA and 1,10-phenanthroline (Oph) were determined by incorporating them into the diet of T. ni larvae. After exposure to light, following 17 h of dark incubation, larvae underwent violent convulsions and vomiting and died within 20 to 40 s. Tetrapyrrole analysis of the treated larvae immediately after dark incubation revealed significant amounts of Proto and Zn-Proto accumulation. Correlation between tetrapyrrole accumulation and larval death was significant. Similar results were obtained when ALA and Dpy were administered to the larvae with the diet. The above results indicated that in addition to contact via spraying, porphyric insecticides had the potential to be very potent when ingested. For a more thorough understanding of the mode of action of porphyric insecticides, the phenomenology of tissue, cellular, and subcellular sites of tetrapyrrole accumulation in representative insect species was investigated. In T. ni larvae, on a unit protein basis, about 59% of the accumulated Proto was observed in the hemolymph, 35% in the gut, and 6% in the integument. Further understanding of the response of insect organs and tissues to porphyric insecticide treatment was obtained by investigating the response of isolated organs and tissues to incubation with ALA + Dpy or ALA + Oph in adult Blattella germanica (German cockroach), adult Anthonomus grandis (cotton boll weevil), fifth instar larvae of Heliothus zea (corn earworm), and fifth instar larvae of T. ni (cabbage looper). In T. ni, and H. zea, significant Proto accumulation was observed in incubated midgut and fat bodies. Proto accumulation occurred when tissues were incubated with Dpy, ALA + Dpy, Oph, and ALA + Oph (2). No response to treatment with ALA alone was observed. In cockroaches, more of the Proto appeared to accumulate in the male and female guts than in their abdomen. As in T. ni and H. zea, the response was elicited by each of the treatments that included Dpy or Oph. Cotton boll weevil abdomens appeared to be less responsive than the abdomens of the other three species. To determine whether Proto accumulation resulted in photodynamic damage of incubated tissues, T. ni midguts were incubated in darkness either in buffer, with ALA, or with Oph + ALA. Oxygen consumption of the tissue was monitored before and after exposure to 2-h of illumination. A 30% decrease in O₂ consumption was observed in midguts treated with Oph or with ALA + Oph after 2 h in the light. The decrease in oxygen consumption observed in isolated T. ni midguts was shown to be caused by photodynamic damage to mitochondrial enzymes. Finally, structure-function photodynamic insecticidal studies led to the identification of 36 compounds belonging to 10 different chemical families that were effective (>70% mortality) against at least one insect species. Of the 36 modulators, 10 exhibited potent activity toward cockroaches.     

Metal dependent coordination of biomolecular ligand: X-ray crystal structures of copper, cobalt and calcium complexes of (3-hydroxy-5-(hydroxymethyl)-2-methylisonicotinic acid) 5-phosphate, an oxidized pyridoxal 5-phosphate

X-ray crystal analyses of divalent copper, cobalt and calcium complexes of monoanionic (3-hydroxy-5-(hydroxymethyl)-2-methylisonicotinic acid) 5-phosphate (L₁C₈H₉NO₇P⁻) revealed the chemical compositions of Cu ---L·3H₂O(1), Co ---L·5H₂O(2) and Ca·L₂·7H₂O (3) and the coordination structures which depend on the coordination abilities and chemical properties of the respective metal ions. Although 1 and 2 crystals showed similar features, i.e., presence of the metal ion at the crystallographic center of symmetry and octahedral six-coordination, the patterns of coordination with the ligand molecules differed. While direct coordination to the L carboxyl oxygen was observed in 1 crystals, all ligation positions in 2 crystals were occupied by water molecules. On the other hand, 3 crystals formed a pentagonal bipyramidal structure (seven-coordination), where oxygens of L phosphates and water molecules coordinated to the calcium ion. Each of the complex structures showed characteristic molecular packing depending on the pattern of coordination to the respective metal ion. L is monoanionic in all complex crystals, where the phosphate and carboxyl groups are deprotonated and pyridine nitrogen is protonated, and is neutralized by each metal ion. Crystal data: 1, monoclinic, space group P2₁/c, A = 5.4129(6), B = 10.515(2), C = 22.770(2) Å, β = 91.853(9)°, Z = 4, R = 0.0404 for 1834 observed reflections; 2, triclinic, space group

Full-size image

, c = 6.789(3) Å, α = 96.84(3), β = 109.10(3), γ = 100.50(2)°, Z = 2, R = 0.0684 for 1605 observed reflections; 3, triclinic, , a = 10.069(2), B = 14.501(3), c = 10.051(1) Å, α = 100.75(1), β = 97.28(2), γ = 76.18(2)°, Z = 2, R = 0.0540 for 3637 observed reflections.     

Photodynamic effects of protoporphyrin on the cellular level—Anin vitro approach

Summary The purpose of this study was characterizing the phototoxic action of protoporphyrin and cellular protection mechanisms, as studied on the cellular level. In this process, active oxygen is involved. As a biological system, rat hepatocyte shortterm and primary cultures were used. Phototoxicity of protoporphyrin could be observed, after previous absorption of protoporphyrin to membrane structures. Damaging of several cell organelles occurred, such as mitochondria and lysosomes. Peroxisomes were not affected. Coated vesicles located at the periphery of the cells’ interior suggested that protoporphyrin absorption is mediated by an active uptake (endocytosis), as well as passive diffusion. Lipid peroxidation played a role in protoporphyrin photoxicity. Cellular protection mechanisms such as superoxide dismutase and the scavenger glutathione (GSH) protected the cells from active oxygen toxicity. In conclusion, protoporphyrin entered the cells by diffusion and endocytosis. Previous adsorption to the membrane structures was necessary for the expression of protoporphyrin phototoxicity. However, active oxygen itself could not be demonstrated. Lipid peroxidation was involved in cell-damaging processes. Mechanisms of protoporphyrin phototoxicity on the cellular level were studied. Rat hepatocyte primary and short-term cultures proved to be suitablein vitro systems for studying biochemical and morphological effects on the cellular level. This article is based on PhD research carried out at the Department of Veterinary Pharmacology, Pharmacy and Toxicology, Utrecht University, The Netherlands.     

Genetic transactivation of Dissociation elements in transgenic tomato plants

Summary A DNA amplification is correlated with the dominant, unstable cob-354 cobalt resistance trait in the cellular slime mold, Dictyostelium discoideum. The amplified DNA is present as about 50 copies of an extrachromosomal element. Cells grown under nonselective conditions in the absence of cobalt ions lose both the cobalt resistance trait and all extrachromosomal copies of the amplified DNA. The amplified DNA is transferrable to new genetic backgrounds by parasexual genetic crosses. These results explain the inability to map the cob-354 trait to a linkage group. The chromosomal origin of the amplified DNA is group III or VI. Thus the resistance trait appears to be independent of the previously known cobalt resistance locus, cobA, which maps to group VII. A developmental defect involving the production of multiply-tipped aggregates that do not complete fruiting body formation also is correlated with the presence of the amplified DNA.     

Q-band electron paramagnetic resonance study of nitrosylprotoheme dimethyl ester complexes with N-,O-, and S-donor ligand as model systems for nitrosylhemoproteins

Electron paramagnetic resonance (epr) spectra (at X- and Q band frequency) of nitrosyl(proto-porphyrin IX dimethyl ester) iron( II) complexes with a trans axial ligand of nitrogen-, oxygen-, and sulfur-donor ligand, in the trozen glass state at 77°K, have been investigated in order to understand the epr spectra of nitrosylhemoproteins. The Q-band spectra resolved the spectral features more clearly than the X-band spectra and distinctly exhibited two groups of absorptions, which were attributable to two molecular species. Significant relations were found between two g values (e.g., g_x-g_z, g_x-g_y) and between the g value and the degree of the hyperfine splitting in central absorption. The epr parameters were not very sensitive to the π-bonding ability of the axial ligand, but registered the steric interaction of the axial ligand with porphynnato core. These findings can be utilized in the characterization of an axial ligand trans to the nitrosyl group in nitrosylhemoproteins.