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1.  Zn(II)-Chlorido Complexes of Phytohormone Kinetin and Its Derivatives Modulate Expression of Inflammatory Mediators in THP-1 Cells 
PLoS ONE  2013;8(6):e65214.
Kinetin (N6-furfuryladenine) belongs to a group of plant growth hormones involved in cell division, differentiation and other physiological processes. One of the possible ways to obtain biologically active compounds is to complex biologically relevant natural compounds to suitable metal atoms. In this work, two structural groups of Zn(II) complexes [Zn(Ln)2Cl2]·Solv (1–5) and [Zn(HLn)Cl3]·xLn (6–7); n = 1–5, Solv = CH3OH for 1 and 2H2O for 2; x = 1 for 6 and 2 for 7; involving a phytohormone kinetin and its derivatives (Ln) were evaluated for their ability to modulate secretion of tumour necrosis factor (TNF)-α, interleukin (IL)-1β and matrix metalloproteinase (MMP)-2 in a lipopolysaccharide (LPS)-activated macrophage-like THP-1 cell model. The penetration of the complexes to cells was also detected. The mechanism of interactions of the zinc(II) complexes with a fluorescent sensor N-(6-methoxy-8-quinolyl)-p-toluene sulphonamide (TSQ) and sulfur-containing biomolecules (l-cysteine and reduced glutathione) was studied by electrospray-ionization mass spectrometry and flow-injection analysis with fluorescence detection. The present study showed that the tested complexes exhibited a low cytotoxic effect on the THP-1 cell line (IC50>40 µM), apart from complex 4, with an IC50 = 10.9±1.1 µM. Regarding the inflammation-related processes, the Zn(II) complexes significantly decreased IL-1β production by a factor of 1.47–2.22 compared with the control (DMSO), but did not affect TNF-α and MMP-2 secretions. However, application of the Zn(II) complexes noticeably changed the pro-MMP-2/MMP-2 ratio towards a higher amount of maturated MMP-2, when they induced a 4-times higher production of maturated MMP-2 in comparison with the vehicle-treated cells under LPS stimulation. These results indicated that the complexes are able to modulate an inflammatory response by influencing secretion and activity of several inflammation-related cytokines and enzymes.
PMCID: PMC3670929  PMID: 23755195
2.  The experimental chemotherapeutic N6-furfuryladenosine (kinetin-riboside) induces rapid ATP depletion, genotoxic stress, and CDKN1A (p21) upregulation in human cancer cell lines 
Biochemical pharmacology  2008;77(7):1125-1138.
Cytokinins and cytokinin nucleosides are purine derivatives with potential anticancer activity. N6-furfuryladenosine (FAdo, kinetin-riboside) displays antiproliferative and apoptogenic activity against various human cancer cell lines, and FAdo has recently been shown to suppress tumor growth in murine xenograft models of human leukemia and melanoma. In this study, FAdo-induced genotoxicity, stress response gene expression, and cellular ATP depletion were examined as early molecular consequences of FAdo-exposure in MiaPaCa-2 pancreas carcinoma, A375 melanoma, and other human cancer cell lines. FAdo, but not adenosine or N6-furfuryladenine, displayed potent antiproliferative activity that was also observed in human primary fibroblasts and keratinocytes. Remarkably, massive ATP depletion and induction of genotoxic stress as assessed by the alkaline comet assay occurred within 60 to 180 minutes of exposure to low micromolar concentrations of FAdo. This was followed by rapid upregulation of CDKN1A and other DNA damage/stress response genes (HMOX1, DDIT3, GADD45A) as revealed by expression array and Western analysis. Pharmacological and siRNA-based genetic inhibition of adenosine kinase suppressed FAdo cytotoxicity and also prevented ATP-depletion and p21-upregulation suggesting the importance of bioconversion of FAdo into the nucleotide form required for drug action. Taken together our data suggest that early induction of genotoxicity and energy crisis are important causative factors involved in FAdo cytotoxicity.
PMCID: PMC2656390  PMID: 19186174
kinetin; N6-furfuryladenosine; genotoxic stress; ATP depletion; CDKN1A; cancer
3.  One Step Synthesis of NiO Nanoparticles via Solid-State Thermal Decomposition at Low-Temperature of Novel Aqua(2,9-dimethyl-1,10-phenanthroline)NiCl2 Complex 
[NiCl2(C14H12N2)(H2O)] complex has been synthesized from nickel chloride hexahydrate (NiCl2·6H2O) and 2,9-dimethyl-1,10-phenanthroline (dmphen) as N,N-bidentate ligand. The synthesized complex was characterized by elemental analysis, infrared (IR) spectroscopy, ultraviolet-visible (UV-vis) spectroscopy and differential thermal/thermogravimetric analysis (TG/DTA). The complex was further confirmed by single crystal X-ray diffraction (XRD) as triclinic with space group P-1. The desired complex, subjected to thermal decomposition at low temperature of 400 ºC in an open atmosphere, revealed a novel and facile synthesis of pure NiO nanoparticles with uniform spherical particle; the structure of the NiO nanoparticles product was elucidated on the basis of Fourier transform infrared (FT-IR), UV-vis spectroscopy, TG/DTA, XRD, scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDXS) and transmission electron microscopy (TEM).
PMCID: PMC3876087  PMID: 24351867
nickel(II) complex; thermal decomposition; 2,9-dimethyl-1,10-phenanthroline; nanoparticles
4.  Metalloporphyrin Mixed-Valence π-Cation Radicals: [Fe(oxoOEC./2)(Cl)]2SbCl6, Structure, Magnetic Properties, and Near-IR Spectra 
Inorganic chemistry  2011;50(18):9114-9121.
The preparation and characterization of a mixed-valence π-cation radical derivative of an iron(III) oxochlorinato complex is reported. The new complex has been synthesized by the one-electron oxidation of a pair of [Fe(oxoOEC)(Cl)] molecules to form the dimeric cation [Fe(oxoOEC)(Cl)]+2. The cation has been characterized by an X-ray analysis, Mössbauer spectroscopy, UV-vis and near-IR spectroscopy, and magnetic susceptibility measurements from 6–300 K. The crystal structure shows that the two rings have a smaller overlap area that those of the formally related nickel and copper octaethylporphyrinateethylporphinate derivatives, reflecting the larger steric congestion at the periphery in part of the oxochlorin rings. The Mössbauer data is consistent with two equivalent iron(III) centers. The unpaired electron is delocalized over the two oxochlorin rings and mediates a strong antiferromagnetic interaction between the high-spin iron(III) centers.
PMCID: PMC3171574  PMID: 21809820
5.  Di-μ-chlorido-bis­{bis­[4-(adamantan-1-ylcarbamo­yl)pyridine-κN]chlorido­copper(II)} hemihydrate 
In the centrosymmetric dimeric title compound, [Cu2Cl4(C16H20N2O)4]·0.5H2O, the CuII atom is in a distorted trigonal–bipyramidal environment defined by two bridging Cl atoms, one terminal Cl atom and two N atoms from two monodentate 4-(adamantan-1-ylcarbamo­yl)pyridine ligands. The amine N atoms are involved in intra­molecular N—H⋯O and inter­molecular N—H⋯Cl hydrogen bonds. The latter hydrogen bonds link the complex mol­ecules into a ribbon along [010]. The uncoordinated water mol­ecule is 0.25-occupied.
PMCID: PMC3274881  PMID: 22346828
6.  Discovery of a Cytokinin Deaminase† 
ACS chemical biology  2011;6(10):1036-1040.
An enzyme of unknown function within the amidohydrolase superfamily was discovered to catalyze the hydrolysis of N-6-substituted adenine derivatives, several of which are cytokinins. Cytokinins are a common type of plant hormone and N-6-substituted adenines are also found as modifications to tRNA. Patl2390, from Pseudoalteromonas atlantica T6c, was shown to hydrolytically deaminate N-6-isopentenyladenine to hypoxanthine and isopentenylamine with a kcat/Km of 1.2 × 107 M−1 s−1. Additional substrates include N-6-benzyl adenine, cis- and trans-zeatin, kinetin, O-6-methylguanine, N-6-butyladenine, N-6-methyladenine, N,N-dimethyladenine, 6-methoxypurine, 6-chloropurine, and 6-thiomethylpurine. This enzyme does not catalyze the deamination of adenine or adenosine. A comparative model of Patl2390 was computed using the three-dimensional crystal structure of Pa0148 (PDB code: 3PAO) as a structural template and docking was used to refine the model to accommodate experimentally identified substrates. This is the first identification of an enzyme that will hydrolyze an N-6 substituted side chain larger than methylamine from adenine.
PMCID: PMC3199332  PMID: 21823622
7.  Structural and Magnetic Effects of meso-Substitution in Alkyl-Substituted Metalloporphyrinate π-Cation Radicals: Characterization of [Fe-(TalkylP.)(Cl)]SbCl6 (alkyl = ethyl and n-propyl) 
Inorganic chemistry  2010;49(17):8078-8085.
We report the preparation and characterization of two meso-alkyl substituted porphyrin π-cation radical derivatives, [Fe(TalkylP.)(Cl)]SbCl6 (alkyl = ethyl or propyl). Both complexes have been characterized by UV/vis/near-IR, IR and Mössbauer spectroscopy, temperature-dependent solid-state magnetic susceptibility measurements and X-ray structure determinations. All data for both oxidized species are consistent with the formulation of the complexes as ring-oxidized iron(III) porphyrin species. The molecular structures of the two five-coordinate species have the typical square-pyramidal coordination group of high-spin iron(III) derivatives. The crystal structures also reveal that the species form cofacial π–π dimers with lateral shifts of 1.44 Å and 3.22 Å, respectively, for the propyl and ethyl radical derivatives. Both radicals exhibit porphyrin cores with alternating bond distance patterns in the inner 16-membered ring. In addition, [Fe(TEtP.)(Cl)]SbCl6 and [Fe(TPrP.)(Cl)]SbCl6 have been characterized by temperature-dependent (6–300K) magnetic susceptibility studies, the best fitting of the temperature-dependent moments reveal strong coupling between iron spins and porphyrin radical, and a smaller magnitude of antiferromagnetic coupling between ring radicals, which are opposite to those found in the five-coordinate iron(III) OEP radicals. The differences in structure and properties of the cation radical meso-alkyl and β-alkyl derivatives possibly reflect differences in properties of a 1u- and a 2u-forming radicals.
PMCID: PMC2980783  PMID: 20799740
8.  Metal-Based Biologically Active Compounds: Synthesis, Spectral, and Antimicrobial Studies of Cobalt, Nickel, Copper, and Zinc Complexes of Triazole-Derived Schiff Bases 
A series of cobalt, nickel, copper, and zinc complexes of bidentate Schiff bases derived from the condensation reaction of 4-amino-5-mercapto-3-methyl/ethyl-1,2,4-triazole with 2,4-dichlorobenzaldehyde were synthesized and tested as antimicrobial agents. The synthesized Schiff bases and their metal complexes were characterized with the aid of elemental analyses, magnetic moment measurements, spectroscopic and thermogravimetric techniques. The presence of coordinated water in metal complexes was supported by infrared and thermal gravimetric studies. A square planar geometry was suggested for Cu(II) and octahedral geometry proposed for Co(II), Ni(II), and Zn(II) complexes. The Schiff bases and their metal complexes have been screened for antibacterial (Pseudomonas aeruginosa, Bacillus subtilis) and antifungal activities (Aspergillus niger, A. flavus). The metal complexes exhibited significantly enhanced antibacterial and antifungal activity as compared to their simple Schiff bases.
PMCID: PMC3246298  PMID: 22216017
9.  Characterization and Antimicrobial Activity of Erbium(III) Complexes of C-3 Substituted 2-hydroxy-1,4-naphthalenedione-1-oxime Derivatives 
Metal-Based Drugs  2001;8(3):159-164.
Erbium(III) complexes of 2-hydroxy-l,4-naphthalenedione-1-oxime and its C-3 substituted derivatives are synthesized and characterized by elemental analysis, thermogravimetric analysis, infrared spectroscopy, magnetic susceptibility measurements 2-hydroxy-1,4-naphthalenedione-1-oxime derivatives are analysed using 1H and 13C NMR spectroscopy. The molecular composition of the synthesized complexes is found to be [ML3(H2O)2]. The antimicrobial activity of these complexes is determined by well diffusion method against the target microorganisms- Staphylococcus aureus, Xanthomonas campestris, Pseudomonas aeruginosa, Candida albicans and Aspergillus niger. The antimicrobial activities of 2- hydroxy-1,4-naphthalenedione-1-oximes and their complexes are compared. It is observed that 2-hydroxy-1,4-naphthalenedione-l-oximes exhibit higher antifungal activity as compared to antibacterial activity. These activities are reduced upon complexation of these oximes with Erbium.
PMCID: PMC2365264  PMID: 18475990
10.  Plant regeneration from immature inflorescence derived callus cultures of salt tolerant kallar grass (Leptochloa fusca L.) 
Efficient plant regeneration has been achieved from immature inflorescence derived callus cultures of salt tolerant grass Leptochloa fusca (L.). Young inflorescence explants displayed wide-ranging responses for callus induction and plant regeneration when subjected to different cold treatment durations and without cold treatment exposure (control) prior to its inoculation to MS medium supplemented with different concentrations/combinations of plant growth regulators (PGRs). The PGRs included auxins: 2, 4-dichlorophenoxy acetic acid (2, 4-D), picloram (Pic), 3, 6-dichloro-2-methoxy benzoic acid (dicamba) and cytokinins: Kinetin (KN), N6-benzyl adenine (BA). These treatments promoted different callus induction frequencies as well as various callus types such as type 1, type 2 and type 3. Induction of type 2 callus (white and compact) with potential for regeneration was obtained from cold treated (3 days at 10 °C) immature inflorescence cultured on MS medium containing 2.0 mg/l dicamba and 0.25 mg/l BA. The study demonstrated that 2.0 mg/l dicamba and 0.25 mg/l BA induced callus promoted improved frequency compared to zilch shoot regeneration response with other combinations involving 2, 4-D, picloram, KN and BA. Full strength MS supplemented with 2.0 mg/l NAA and 0.5 mg/l BA was found to be optimal for plant regeneration. The regeneration frequencies ranged from 13.8 ± 1.366 to 55.5 ± 2.766 with highest number of shoots (19.1 ± 0.560) per 50–60 mg of callus as explants after 28 days of inoculation. Plant regeneration was also obtained on the dicamba callus induction medium itself within 21 days inoculation of immature inflorescence explants. Half strength MS medium both semisolid and liquid devoid of plant growth regulators promoted highest frequency (92.8 ± 4.099 and 100 ± 0.00) of rooting in regenerated shoots. Plants with well developed roots were successfully transferred to pots and grown to maturity with normal flowering and seed set. This is the first report on induction of callus and subsequent plant regeneration in kallar grass using immature inflorescence explants.
PMCID: PMC3550551  PMID: 24082497
Leptochloa fusca; Immature inflorescence; Callus induction; Plant regeneration
11.  Coordination Polymer: Synthesis, Spectral Characterization and Thermal Behaviour of Starch-Urea Based Biodegradable Polymer and Its Polymer Metal Complexes 
A starch-urea-based biodegradable coordination polymer modified by transition metal Mn(II), Co(II), Ni(II), Cu(II), and Zn(II) was prepared by polycondensation of starch and urea. All the synthesized polymeric compounds were characterized by Fourier transform-infrared spectroscopy (FT-IR), 1H-NMR spectroscopy, 13C-NMR spectroscopy, UV-visible spectra, magnetic moment measurements, differential scanning calorimeter (DSC), and thermogravimetric analysis (TGA). The results of electronic spectra and magnetic moment measurements indicate that Mn(II), Co(II), and Ni(II) complexes show octahedral geometry, while Cu(II) and Zn(II) complexes show square planar and tetrahedral geometry, respectively. The thermogravimetric analysis revealed that all the polymeric metal complexes are more thermally stable than the parental ligand. In addition, biodegradable studies of all the polymeric compounds were also carried out through ASTM standards of biodegradable polymers by CO2 evolution method.
PMCID: PMC2857575  PMID: 20414461
12.  Di-μ-chlorido-bis­[chlorido(N,N′-dibenzyl­propane-1,2-diamine-κ2 N,N′)copper(II)] 
In the title complex, [Cu2Cl4(C17H22N2)2], the CuII cation is coordinated by a N,N′-dibenzyl­propane-1,2-diamine ligand and two Cl− anions, and a Cl− anion from an adjacent mol­ecule further bridges to the CuII cation in the apical position, with a longer Cu—Cl distance of 2.9858 (18) Å, forming a centrosymmetric dimeric complex in which each CuII cation is in a distorted square-pyramidal geometry. Intra­molecular N—H⋯Cl hydrogen bonding is observed in the dimeric complex.
PMCID: PMC2971131  PMID: 21578213
13.  Thermal stability of the prototypical Mn porphyrin-based superoxide dismutase mimic and potent oxidative-stress redox modulator Mn(III) meso-tetrakis(N-ethylpyridinium-2-yl)porphyrin chloride, MnTE-2-PyP5+ 
Cationic Mn porphyrins are among the most potent catalytic antioxidants and/or cellular redox modulators. Mn(III) meso-tetrakis(N-ethylpyridinium-2-yl)porphyrin chloride (MnTE-2-PyPCl5) is the Mn porphyrin most studied in vivo and has successfully rescued animal models of a variety of oxidative stress-related diseases. The stability of an authentic MnTE-2-PyPCl5 sample was investigated hereon by thermogravimetric, derivative thermogravimetric, and differential thermal analyses (TG/DTG/DTA), under dynamic air, followed by studies at selected temperatures to evaluate the decomposition path and appropriate conditions for storage and handling of these materials. All residues were analyzed by thin-layer chromatography (TLC) and UV-vis spectroscopy. Three thermal processes were observed by TG/DTG. The first event (endothermic) corresponded to dehydration, and did not alter the MnTE-2-PyPCl5 moiety. The second event (endothermic) corresponded to the loss of EtCl (dealkylation), which was characterized by gas chromatography-mass spectrometry. The residue at 279 °C had UV-vis and TLC data consistent with those of the authentic, completely dealkylated analogue, MnT-2-PyPCl. The final, multi-step event corresponded to the loss of the remaining organic matter to yield Mn3O4 which was characterized by IR spectroscopy. Isothermal treatment at 188 °C under static air for 3 h yielded a mixture of partially dealkylated MnPs and traces of the free-base, dealkylated ligand, H2T-2-PyP, which reveals that dealkylation is accompanied by thermal demetallation under static air conditions. Dealkylation was not observed if the sample was heated as a solid or in aqueous solution up to ∼100 °C. Whereas moderate heating changes sample composition by loss of H2O, the dehydrated sample is indistinguishable from the original sample upon dissolution in water, which indicates that catalytic activity (on Mn basis) remains unaltered. Evidently, dealkylation at high temperature compromises sample activity.
PMCID: PMC3688467  PMID: 22503130
Porphyrin; Thermal Analysis; Antioxidant; SOD mimic; Dealkylation
14.  Di-μ2-chlorido-bis­[chlorido(η5-2,3,4,5-tetra­methyl-1-propyl­cyclo­penta­dien­yl)iridium(III)] 
The asymmetric unit of the title complex, [Ir2Cl4(C12H19)2], a versatile starting material for the preparation of uniquely substituted penta­alkyl­cyclo­penta­dien­yl–iridium complexes, consists of an iridium(III) atom, a substituted cyclo­penta­dienyl ligand and two chlorine ligands. The full dimer is generated by an inversion center. In the dimer, the two IrIII atoms and two bridging Cl atoms form a perfectly planar ring. The two IrIII atoms and the two terminal Cl atoms also form a rigorous plane that is orthogonal [89.48 (3)°] to the Ir2Cl2 ring. The plane of the cyclo­penta­dienyl ligand forms a dihedral angle of 54.06 (7)° with respect to the Ir2Cl2 ring.
PMCID: PMC3588487  PMID: 23476515
15.  Assessing the response of indigenous loquat cultivar Mardan to phytohormones for in vitro shoot proliferation and rooting*  
In vitro cultures of loquat cultivar Mardan were established using shoot apices after treating with NaOCl (5%, 7%, 10%, 12%, 14% (v/v)) for 12 min and HgCl2 (0.01%, 0.05%, 0.10%, 0.20%, 0.25% (w/v)) for 2 min. A maximum survival rate of 70% was recorded after surface sterilization with 10% NaOCl. Caulogenic response was assessed on Murashige and Skoog (MS) medium fortified with assorted combinations of the cytokinins, benzylaminopurine (BAP), kinetin, and N6-(2-isopentyl)adenine (2iP). Treatment of BAP 1.5 mg/L combined with 2iP 9.0 mg/L and kinetin 1.5 mg/L was found to be optimum for shoot morphogenesis in terms of the number and subsequent growth of shoots, while the highest shoot length was yielded by the combination of BAP 0.5 mg/L, kinetin 0.5 mg/L, and 2iP 3 mg/L. Higher levels of cytokinins induced callogenesis, vitrification and stunted growth to some extent. For rhizogenesis, uniform sized micro-shoots were excised and transferred to half-strength MS medium containing auxins. The best rooting expression was observed with naphthaleneacetic acid (NAA) 1 mg/L combined with indole-3-butyric acid (IBA) 2 mg/L and paclobutrazol (PBZ) 1 mg/L.
PMCID: PMC3773548  PMID: 24009197
Eriobotrya japonica; Micropropagation; Sterilization of loquat; Plant growth regulator; Shoot proliferation; Rhizogenesis
16.  trans-Di-μ-chlorido-bis­{chlorido[tris­(3,5-dimethyl­phen­yl)phosphane-κP]palla­dium(II)} dichloro­methane monosolvate 
In the dimeric title compound, [Pd2Cl4{P(C8H9)3}2]·CH2Cl2, the metal complex molecule is situated about an inversion centre and is accompanied by a dichloro­methane solvent mol­ecule situated on a twofold rotation axis. The PdII atom has a slightly distorted square-planar coordination sphere. The effective cone angle for the tris­(3,5-dimethyl­phen­yl)phos­phane ligand was calculated to be 169°. In the crystal, the metal complex and solvent mol­ecules are linked via C—H⋯Cl inter­actions, generating chains along [10-2]. There are also C—H⋯π and weak π–π inter­actions present [centroid–centroid distance = 3.990 (2) Å, plane–plane distance = 3.6352 (15) Å and ring slippage = 1.644 Å], forming of a three-dimensional structure.
PMCID: PMC3588800  PMID: 23468765
17.  Manilkara zapota (Linn.) Seeds: A Potential Source of Natural Gum 
ISRN Pharmaceutics  2014;2014:647174.
Mucilage isolated from seeds of Manilkara zapota (Linn.) P. Royen syn. is a plant growing naturally in the forests of India. This mucilage is yet to be commercially exploited, and characterized as polymer. Various physicochemical methods like particle size analysis, scanning electron microscopy, thermal analysis, gel permeation chromatography, X-ray diffraction spectrometry, zeta potential, Fourier transform infrared spectroscopy, and nuclear magnetic resonance spectroscopy have been employed to characterize this gum in the present study. Particle size analyses suggest that mucilage has particle size in nanometer. Scanning electron microscopy analysis suggests that the mucilage has irregular particle size. The glass transition temperature of the gum was observed to be 138°C and 136°C by differential scanning calorimetry and differential thermal analysis, respectively. The thermogravimetric analysis suggested that mucilage had good thermal stability. The average molecular weight of mucilage was determined to be 379180, by gel permeation chromatography, while the viscosity of mucilage was observed to be 219.1 cP. The X-ray diffraction spectrometry pattern of the mucilage indicates a completely amorphous structure. Elemental analysis of the gum revealed the contents of carbon, hydrogen, nitrogen, and sulfur to be 80.9 (%), 10.1 (%), 1.58 (%), and 512 (mg/kg), respectively. Mucilage had specific content of calcium, magnesium, potassium, lower concentrations of aluminum, cadmium, cobalt, lead, and nickel. The major functional groups identified from FT-IR spectrum include 3441 cm−1 (–OH), 1660 cm−1 (Alkenyl C–H & C=C Stretch), 1632 cm−1 (–COO–), 1414 cm−1 (–COO–), and 1219 cm−1 (–CH3CO). Analysis of mucilage by paper chromatography and 1D NMR, indicated the presence of rhamnose, xylose, arabinose, mannose, and fructose.
PMCID: PMC3960745  PMID: 24729907
18.  Quinine and Chloroquine Differentially Perturb Heme Monomer–Dimer Equilibrium 
Inorganic chemistry  2008;47(13):6077-6081.
Nuclear magnetic resonance (NMR) measurements of magnetic susceptibility have been utilized to study the equilibrium between two forms (high-spin monomer vs the antiferromagnetically coupled μ-oxo dimer) of ferriprotoporphyrin(IX) as a function of pH. The pH dependence of this equilibrium is significantly altered by the addition of either chloroquine or quinine. Chloroquine promotes the μ-oxo dimer whereas quinine promotes the monomer.
PMCID: PMC2584347  PMID: 18533646
19.  Cryptococcus neoformans Mitochondrial Superoxide Dismutase: an Essential Link between Antioxidant Function and High-Temperature Growth 
Eukaryotic Cell  2005;4(1):46-54.
Manganese superoxide dismutase is an essential component of the mitochondrial antioxidant defense system of most eukaryotes. In the present study, we used a reverse-genetics approach to assess the contribution of the Cryptococcus neoformans manganese superoxide dismutase (Sod2) for antioxidant defense. Strains with mutations in the SOD2 gene exhibited increased susceptibility to oxidative stress as well as poor growth at elevated temperatures compared to isogenic wild-type strains. The sod2Δ mutants were also avirulent in a murine model of inhaled cryptococcosis. Reconstitution of a sod2Δ mutant restored Sod2 activity, eliminated the oxidative stress and temperature-sensitive (ts) phenotypes, and complemented the virulence phenotype. Characterization of the ts phenotype revealed a dependency between Sod2 antioxidant activity and the ability of C. neoformans cells to adapt to growth at elevated temperatures. The ts phenotype could be suppressed by the addition of either ascorbic acid (10 mM) or Mn salen (200 μM) at 30°C, but not at 37°C. Furthermore, sod2Δ mutant cells that were incubated for 24 h at 37°C under anaerobic, but not aerobic, conditions were viable when shifted to the permissive conditions of 25°C in the presence of air. These data suggest that the C. neoformans Sod2 is a major component of the antioxidant defense system in this human fungal pathogen and that adaptation to growth at elevated temperatures is also dependent on Sod2 activity.
PMCID: PMC544162  PMID: 15643059
20.  Spectroscopic, Thermal, Electrochemical, and Antimicrobial Studies of Mononuclear Manganese(II) Ditolyldithiophosphates 
New complexes of manganese(II) corresponding to [{(ArO)2PS2}2Mn] and [{(ArO)2PS2}2Mn.nL] (Ar = o-, m-, p-CH3C6H4 and p-Cl-m-CH3C6H3; n = 1, L = N2C12H8, N2C10H8; n = 2, L = NC5H5, P(C6H5)3) have been synthesized and characterized by microelemental analyses (C, H, and N), magnetic susceptibility, molar conductance, thermogravimetric, cyclic voltammetry, and spectral analyses including ESI mass spectrometry, IR, and UV-visible. The presence of a four-and-six coordinated Mn atoms has been established in the complexes and adducts, respectively. Antimicrobial screening of the complexes against gram negative bacteria E. coli, K. pneumonia, and P. aeruginosa and fungus S. rolfsii has shown potential bioactivity.
PMCID: PMC3747474  PMID: 23983670
21.  Antimicrobial Study of Newly Synthesized Lanthanide(III) Complexes of 2-[2-hydroxy-3-methoxyphenyl]-3-[2-hydroxy-3-methoxybenzylamino]-1,2-dihydroquinazolin-4(3H)-one 
Metal-Based Drugs  2008;2007:37348.
New lanthanide(III) complexes with 2-[2-hydroxy-3-methoxyphenyl]-3-[hydroxyl-3-methoxybenzylamino]-1,2-dihydroquin- azoline-4(3H)-one (Hmpbaq) have been synthesized and characterized by elemental analysis, conductance measurements, magnetic susceptibilities, spectroscopic (IR, NMR, UV, EPR), and thermal studies. Molar conductance studies indicate 1 : 1 electrolytic behavior for these complexes. IR spectra indicate that Hmpbaq acts as a tridentate ligand coordinating through carbonyl oxygen, benzyl amine nitrogen, and deprotonated phenolic oxygen. TG and DTA studies of La(III) and Pr(III) complexes indicate the presence of two coordinated water molecules. Based on these studies, the complexes have been formulated as [La(mpbaq)2(H2O)2]·NO3, where Ln = La(III), Pr(III), Nd(III), Sm(III), Eu(III), Gd(III), Th(III), Dy(III), and Y(III). The ligand, lanthanide(III) salts, and the corresponding complexes have been simultaneously screened for their antibacterial and antifungal activities and compared with the drugs in use.
PMCID: PMC2248225  PMID: 18309372
22.  catena-Poly[[bis­[1-(2-hydroxy­ethyl)-1H-tetra­zole-κN 4]copper(II)]-di-μ-chlorido]: a powder study 
The crystal structure of the title polymeric complex, [CuCl2(C3H6N4O)2]n, was obtained by the Rietveld refinement from laboratory X-ray powder diffraction data collected at room temperature. The unique CuII ion lies on an inversion center and is in a slightly distorted octa­hedral coordination environment. In the hydroxy­ethyl group, all H atoms, the O atom and its attached C atom are disordered over two positions; the site occupancy factors are ca 0.6 and 0.4. The OH group is involved in an intra­molecular O—H⋯N hydrogen bond.
PMCID: PMC2961963  PMID: 21203033
23.  Di-μ-chlorido-bis­[(2,2′-bibenzimidazole)chloridocadmium(II)] 
The title binuclear complex, [Cd2Cl4(C14H10N4)2], was synthesized by the hydro­thermal reaction of CdCl2 and the ligand 2,2′-bibenzimidazole. The mol­ecule lies on an inversion center and the metal center displays a strongly distorted trigonal-bipyramidal geometry. The CdII ions are coordinated by two N atoms from the organic ligand, and by one terminal and two bridging chloride anions. The crystal structure involves inter­molecular N—H⋯Cl hydrogen bonds, resulting in a one-dimensional supra­molecular structure.
PMCID: PMC2967883  PMID: 21581509
24.  Antiferromagnetic Ordering of Magnetic Clusters Units in Nb6F15 
Applied Magnetic Resonance  2012;44(1-2):143-151.
We have studied the magnetic cluster compound Nb6F15 which has an odd number of 15 valence electrons per (Nb6F12)3+ cluster core, as a function of temperature using nuclear magnetic resonance, magnetic susceptibility, electron magnetic resonance and neutron powder diffraction. Nuclear magnetic resonance of the 19F nuclei shows two lines corresponding to the apical Fa−a nucleus, and to the inner Fi nuclei. The temperature dependence of the signal from the Fi nuclei reveals an antiferromagnetic ordering at T < 5 K, with a hyperfine field of ~2 mT. Magnetic susceptibility exhibits a Curie–Weiss behavior with TN ~5 K, and μeff ~1.57 μB close to the expected theoretical value for one unpaired electron (1.73 μB). Electron magnetic resonance linewidth shows a transition at 5 K. Upon cooling from 10 to 1.4 K, the neutron diffraction shows a decrease in the intensity of the low-angle diffuse scattering below Q ~0.27 Å−1. This decrease is consistent with emergence of magnetic order of large magnetic objects (clusters). This study shows that Nb6F15 is paramagnetic at RT and undergoes a transition to antiferromagnetic order at 5 K. This unique antiferromagnetic ordering results from the interaction between magnetic spins delocalized over each entire (Nb6F12i)3+ cluster core, rather than the common magnetic ordering.
PMCID: PMC3549236  PMID: 23349566
25.  Formation of Asymmetrical Structured Silica Controlled by a Phase Separation Process and Implication for Biosilicification 
PLoS ONE  2013;8(4):e61164.
Biogenetic silica displays intricate patterns assembling from nano- to microsize level and interesting non-spherical structures differentiating in specific directions. Several model systems have been proposed to explain the formation of biosilica nanostructures. Of them, phase separation based on the physicochemical properties of organic amines was considered to be responsible for the pattern formation of biosilica. In this paper, using tetraethyl orthosilicate (TEOS, Si(OCH2CH3)4) as silica precursor, phospholipid (PL) and dodecylamine (DA) were introduced to initiate phase separation of organic components and influence silica precipitation. Morphology, structure and composition of the mineralized products were characterized using a range of techniques including field emission scanning electron microscopy (FESEM), transmission electron microscope (TEM), X-ray diffraction (XRD), thermogravimetric and differential thermal analysis (TG-DTA), infrared spectra (IR), and nitrogen physisorption. The results demonstrate that the phase separation process of the organic components leads to the formation of asymmetrically non-spherical silica structures, and the aspect ratios of the asymmetrical structures can be well controlled by varying the concentration of PL and DA. On the basis of the time-dependent experiments, a tentative mechanism is also proposed to illustrate the asymmetrical morphogenesis. Therefore, our results imply that in addition to explaining the hierarchical porous nanopatterning of biosilica, the phase separation process may also be responsible for the growth differentiation of siliceous structures in specific directions. Because organic amine (e.g., long-chair polyamines), phospholipids (e.g., silicalemma) and the phase separation process are associated with the biosilicification of diatoms, our results may provide a new insight into the mechanism of biosilicification.
PMCID: PMC3621999  PMID: 23585878

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