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1.  Synthesis, Characterization, and Biological Studies of Organotin(IV) Derivatives with o- or p-hydroxybenzoic Acids 
Organotin(IV) complexes with o- or p-hydroxybenzoic acids (o-H2BZA or p-H2BZA) of formulae [R2Sn(HL)2] (where H2L = o-H2BZA and R = Me- (1), n-Bu- (2)); [R3Sn(HL)] (where H2L = o-H2BZA and R = n-Bu- (3), Ph- (4) or H2L = p-H2BZA and R = n-Bu- (5), Ph- (6)) were synthesized by reacting a methanolic solution of di- and triorganotin(IV) compounds with an aqueous solution of the ligand (o-H2BZA or p-H2BZA) containing equimolar amounts of potassium hydroxide. The complexes were characterized by elemental analysis, FT-IR, Far-IR, TGA-DTA, FT-Raman, Mössbauer spectroscopy, 1H, 119Sn-NMR, UV/Vis spectroscopy, and Mass spectroscopy. The X-ray crystal structures of complexes 1 and 2 have also been determined. Finally, the influence of these complexes 1–6 upon the catalytic peroxidation of linoleic acid to hydroperoxylinoleic acid by the enzyme lipoxygenase (LOX) was kinetically studied and the results showed that triorganotin(IV) complex 6 has the lowest IC50 value. Also complexes 1–6 were studied for their in vitro cytotoxicity against sarcoma cancer cells (mesenchymal tissue) from the Wistar rat, and the results showed that the complexes have high activity against these cell lines with triphenyltin((IV) complex 4 to be the most active one.
PMCID: PMC2669538  PMID: 19390627
2.  The First Metal Complexes of 4,6-diamino-1-hydro-5-hydroxy-pyrimidine-2-thione: Preparation, Physical and Spectroscopic Studies, and Preliminary Antimicrobial Properties 
The new complexes [M2O5L2(H2O)2] · H2O (M = Mo, 1; M = W, 2), [RuL2(H2O)2] · H2O (3), [ML3] · xH2O (M = Rh, x = 2, 4; M = Ir, x = 1, 5), [RhL2(PPh3)2](ClO4) · 2H2O (6), [PdL2] · 2H2O (7), [PdL(phen)]Cl · H2O (8), [Re OL2(PPh3)]Cl (9) and [UO2L2] (10) are reported, where LH is 4,6-diamino-1-hydro-5-hydroxy-pyrimidine-2-thione. The complexes were characterized by elemental analyses, physical techniques (molar conductivity, room-temperature magnetic susceptibility), and spectroscopic (IR, Raman, UV/VIS/ligand field, NMR, mass) methods. The ligand L− is in its thione form and behaves as a bidentate chelate with the deprotonated (hydroxyl) oxygen and the nitrogen of one amino group as donor atoms. Oxobridged dinuclear (1, 2) and various mononuclear (3–10) structures are assigned for the complexes in the solid state. The metal ion coordination geometries are octahedral (1–6, 9, 10) or square planar (7, 8). The free ligand LH and complexes 1, 4, 7, and 8 were assayed in vitro for antimicrobial activity against two bacterial and two fungal cultures.
PMCID: PMC2659754  PMID: 19325921
3.  Cu(II) and Ni(II) Interactions with the Terminally Blocked Hexapeptide Ac-Leu-Ala-His-Tyr-Asn-Lys-amide Model of Histone H2B (80–85) 
The N- and C-terminal blocked hexapeptide Ac-Leu-Ala-His-Tyr-Asn-Lys-amide (LAHYNK) representing the 80–85 fragment of histone H2B was synthesized and its interactions with Cu(II) and Ni(II) ions were studied by potentiometric, UV-Vis, CD, EPR, and NMR spectroscopic techniques in solution. Our data reveal that the imidazole N(3) nitrogen atom is the primary ligating group for both metal ions. Sequential amide groups deprotonation and subsequent coordination to metal ions indicated an {Nimidazole, 3Namide} coordination mode above pH∼9, in all cases. In the case of Cu(II)-peptide system, the almost exclusive formation of the predominant species CuL in neutral media accounting for almost 98% of the total metal ion concentration at pH 7.3 strongly indicates that at physiological pH values the sequence -LAHYNK- of histone H2B provides very efficient binding sites for metal ions. The imidazole pyrrole N(1) ionization (but not coordination) was also detected in species CuH−4L present in solution above pH ∼ 11.
PMCID: PMC2292837  PMID: 18431450
4.  Crystal Structure and Antitumor Activity of the Novel Zwitterionic Complex of tri-n-Butyltin(IV) with 2-Thiobarbituric Acid 
A novel tri-n-butyl(IV) derivative of 2-thiobarbituric acid (HTBA) of formula [(n-Bu)3Sn(TBA) H2O] (1) has been synthesized and characterized by elemental analysis and 119Sn-NMR and FT-IR spectroscopic techniques. The crystal structure of complex 1 has been determined by single crystal X-ray diffraction analysis at 120(2) K. The geometry around Sn(IV) is trigonal bipyramidal. Three n-butyl groups and one oxygen atom from a deprotonated 2-thiobarbituric ligand are bonded to the metal center. The geometry is completed with one oxygen from a water molecule. Compound 1 exhibits potent, in vitro, cytotoxicity against sarcoma cancer cells (mesenchymal tissue) from the Wistar rat, polycyclic aromatic hydrocarbons (PAH, benzo[a]pyrene) carcinogenesis. In addition, the inhibition caused by 1, in the rate of lipoxygenase (LOX) catalyzed oxidation reaction of linoleic acid to hyperoxolinoleic acid, has been also kinetically and theoretically studied. The results are compared to that of cisplatin.
PMCID: PMC2288696  PMID: 18401456
5.  Thermodynamic and Structural Characterization of the Copper(II) Complexes of Peptides Containing Both Histidyl and Aspartyl Residues 
Terminally protected pentapeptides with 2 histidines (Ac-HHVGD-NH2 and Ac-HVGDH-NH2) and the terminally free peptides containing both internal aspartyl and C-terminal histidyl residues (FDAH and VIDAH) have been synthesized, and copper(II) complexes studied by potentiometric, UV-Vis, CD, and EPR spectroscopic techniques in solution. Both thermodynamic and spectroscopic data reveal that side chain donor atoms of aspartyl and histidyl residues have a significant contribution to the metal binding affinity of peptide molecules. In the case of terminally protected peptides, the role of the imidazole-N donor functions is reflected in the enhanced stability of the 3N and 4N coordinated copper(II) complexes. The amino and β-carboxylate groups of FDAH and VIDAH create a very effective metal binding site with the (NH2, N−, β-COO−) and (NH2, N−, N−, β-COO−) coordination modes including the N-termini, while the histidine sites are available for the formation of the (Nim, N−, N−) binding mode resulting in the preference of dinuclear complex formation.
PMCID: PMC2216053  PMID: 18273380
6.  Pressure-Tuning Raman Spectra of Diiodine Thioamide Compounds: Models for Antithyroid Drug Activity 
The pressure-tuning Raman spectra of five solid, diiodine heterocyclic thioamide compounds (mbztS)I2 (mbztS = N-methyl-2-mercaptobenzothiazole) (1); [(mbztS)2I]+[I7]− (2); (pySH)I2 (pySH = 2-mercaptopyridine) (3); [(pySH)(pyS]+[I3]− (4); (thpm)(I2)2 or possibly [(thpm)I2]+[I3]− (thpm = 2-mercapto-3,4,5,6-tertahydropyrimidine (5) have been measured for pressures up to ∼ 50 kbar using a diamond-anvil cell. Compounds 1, 4, and 5 undergo pressure-induced phase transitions at ∼ 35, ∼ 25, and ∼ 32 kbar, respectively. Following the phase transition in 1, the pressure dependences of the vibrational modes, which were originally located at 84, 111, and 161 cm−1 and are associated with the S⋯I–I linkage, are 2.08, 1.78, and 0.57 cm−1/kbar, respectively. These pressure dependences are typical of low-energy vibrations. The pressure-tuning FT-Raman results for the pairs of compounds 1 , 2, 3, and 4 are remarkably similar to each other suggesting that the compounds are most probably perturbed diiodide compounds rather than ionic ones. The Raman data for 5 show that it is best formulated as (thpm)(I2)2 rather than [(thpm)2I]+[I3]−.
PMCID: PMC1794079  PMID: 17497015
7.  Interaction of Thioamides, Selenoamides, and Amides With Diiodine 
We review the results of our work on the iodine interaction with thioamides, selenoamides, and amides. Complexes with (i) “spoke” or “extended spoke” structures, D · I2 and D · I2 · I2, respectively, (D is the ligand donor) (ii) iodonium salts of {[D2 − I]+[In]−} (n = 3, 7) and {[D2 − I]+[FeCl4]−} formulae and (iii) disulfides of the categories (a) [D − D], (b) {[D − DH]+[I3]−} have been isolated and characterized. A compound of formula {[D2 − I]+[I3]−[D · I2]} containing both types of complexes (i) and (ii) was also isolated. The interaction of diiodine with selenium analogs of the antithyroid drug 6-n-propyl-2-thiouracil (PTU), of formulae RSeU (6-alkyl-2-Selenouracil) results in the formation of complexes with formulae [(RSeU)I2]. All these results are correlated with the mechanism of action of antithyroid drugs. Finally, we review here our work on the diiodine interaction with the amides (LO).
PMCID: PMC1794077  PMID: 17497011
8.  Interactions of Zn(II) Ions with Three His-Containing Peptide Models of Histone H2A 
The interactions of Zn(ll) ions with the blocked hexapeptide models -TESHHK-, -TASHHK- and -TEAHHK- of the -ESHH- motif of the C-terminal of historic H2A were studied by using potentiometric and IH-NMR techniques. The first step of these studies was to compare the pKa values of the two His residues inside each hexapeptide calculated by potentiometric or H-NMR titrations. Hereafter, the potentiometric titrations in the pH range 5 11 suggest the formation of several monomeric Zn(ll) complexes. It was found that all hexapeptides bind to Zn(ll) ions initially through both imidazole nitrogens in weakly acidic and neutral solutions forming slightly distorted octahedral complexes. At higher pH values, the combination of potentiometric titrations and one and two dimensional NMR suggested no amide coordination in the coordination sphere of Zn(II) ions. Obviously, these studies support that the -ESHH- sequence of histone H2A is a potential binding site for Zn(II) ions similarly with the Cu(II) and Ni(ll) ions, presented in previous papers.
PMCID: PMC2267071  PMID: 18365073
9.  Communication: Synthesis of a Novel Triphenyltin(IV) Derivative of 2- Mercaptonicotinic Acid with Potent Cytotoxicity in vitro  
A novel triphenyltin(IV) derivative of 2-mercaptonicotinic acid (H2mna) of formula {[(C6H5)3Sn]2(mna).[(CH3)2CO]} (1) has been synthesized and characterized by elemental analysis and 1H, 13C-NMR, and FT-IR spectroscopic techniques. The crystal structure of complex (1) has been determined by single crystal X-ray diffraction analysis at 173(1) K. Compound (1) contains two triphenyltin moieties linked by a doubly de-protonated 2,mercaptonicotinic acid (H>2mna). It is an example of a pentacoordinated Ph3SnXY system with an axial-equatorial arrangement of the phenyl groups at Sn(1). Compound (1), exhibits potent, in vitro, cytotoxicity against sarcoma cancer cells (mesenchymal tissue) from the Wistar rat, polycyclic aromatic hydrocarbons (PAH, benzo[a]pyrene) carcinogenesis.
PMCID: PMC2267064  PMID: 18365056
10.  Interaction of Cu(II)with His-Val-Gly-Asp and of Zn(II) with His-Val-His, Two Peptides at the Active Site of Cu,Zn-Superoxide Dismutase 
His-Val-His and His-Val-Gly-Asp are two naturally occurring peptide sequences, present at the active site of Cu,Zn-superoxide dismutase (Cu,Zn-SOD). We have already studied the interaction of His-Val-His=A (copper binding site) with Cu(II) and of His-Val-Gly-Asp=B (zinc binding site) with Zn(II). As a continuation of this work and for comparison purposes we have also studied the interaction of Zn(II) with His-Val-His and Cu(II) with His-Val-Gly-Asp using both potentiometric and spectroscopic methods (visible, EPR, NMR). The stoichiometry, stability constants and solution structure of the complexes formed have been determined. Histamine type of coordination is observed for/ZnAH/2+, /ZnA/+, /ZnA2H/+ and/ZnA2/ in acidic pH while deprotonation of coordinated water molecules is observed at higher pH. /CUB/ species is characterized by the formation of a macrochelate and histamine type coordination. Its stability results in the suppression of amide deprotonation which occurs at high pH resulting in the formation of the highly distorted from square planar geometry 4N complex/CuBH-3/3.
PMCID: PMC2267047  PMID: 18365046

Results 1-10 (10)