Maria Louloudi

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The Zn(2+), Cd(2+), Hg(2+), Co(2+) and Ni(2+) ions produce zwitterionic type complexes with the ligands (L), 2-(alpha-hydroxy-benzyl)thiamine=HBT and 2-(alpha-hydroxy-cyclohexyl-methyl)thiamine = HCMT, of the type MLCl(3). The ligands are in the S conformation, the metals are bound to N(1), of the pyrimidine moiety of thiamine and the complexes have a(More)
 The crystal structure of the 2-(α-hydroxethyl) thiamin pyrophosphate (LH2) was solved by X-ray diffraction. Crystallographic data: space group F2dd, a=7.922(4) Å, b=33.11(2) Å, c=36.232(10) Å, V=9503(9) Å3, z=16. Metal complexes of the general formula K2{[M(LH)Cl2]2} (M=Zn2+, Cd2+) were isolated from methanolic solutions and characterized by elemental(More)
This paper is a brief review of the detailed mechanism of action of thiamine enzymes, based on metal complexes of bivalent transition and post-transition metals of model compounds, thiamine derivatives, synthesized and characterized with spectroscopic techniques and X-ray crystal structure determinations. It is proposed that the enzymatic reaction is(More)
Metal complexes of thiamine pyrophosphate (TPP) of the general formula [M2(TPPH)2Cl2].4H2O (M =Zn2+, Cd2+) were isolated from methanolic solutions and characterized by elemental analysis, FT-IR, and multinuclear NMR spectroscopies. The data provide evidence for the bonding of the metals to the N(1') atom of the pyrimidine ring and to the pyrophosphate(More)
Thiamine dependent enzymes catalyze ligase and lyase reactions near a carbonyl moiety. Chemical models for these reactions serve as useful tools to substantiate a detailed mechanism of action. This tutorial review covers all such studies performed thus far, emphasizing the role of each part around the active site and the conformation of the cofactor during(More)
To obtain structural information on the active site of thiamin-dependent enzymes in solution, we have studied the interactions of Cu(2+) ions with 2-(alpha-hydroxyethyl)thiamin pyrophosphate (HETPP), the pentapeptide Asp-Asp-Asn-Lys-Ile surrounding the thiamin pyrophosphate moiety in the transketolase enzyme, and the tertiary Cu(2+)-pentapeptide-HETPP(More)
Mononuclear CuL and Cu(2L) complexes, where L is propyl-thiazol-2-ylmethylene-amine, covalently immobilized onto SiO2, can catalyze efficiently the oxidation of 3,5-di-t-butylcatechol (DTBC) to 3,5-di-t-butylquinone (DTBQ) by utilizing ambient O2 as oxidant. By increasing the loading of L on SiO2, the DTBQ formation can be improved up to 400% vs the(More)
The sorption of a hydrophobic pesticide, thiram, on humic acid (HA) occurs via a specific pH-dependent binding of thiram at the deprotonated carboxylates of humic acid, forming a species thiram-[HACOO-] with K = 0.69. Similarly, thiram was sorbed by two model polycarboxylate-{SiO2COOH} materials via the formation of a surface species thiram-{SiO2COO-} with(More)
A detailed catalytic study of LFe(III)Cl (where L = 3-{2-[2-(3-hydroxy-1,3-diphenyl-allylideneamino)-ethylamino]-ethylimino}-1,3-diphenyl-propen-1-ol) for hydrocarbon oxidation was carried out, focusing on the role of solvent, atmospheric dioxygen, and oxidant on catalytic efficiency. The data showed that LFe(III)Cl catalyst was efficient in homogeneous(More)