Biology of Metals

Photodynamic therapy (PDT) is a promising technique for the treatment of various diseases. In this sense, the singlet oxygen quantum yield (Φ∆) is a physical–chemical property that allows to stablish the applicability of a potential photosensitizers (PS) as a drug for PDT. In the herein report, the Φ∆ of three photosensitizers was determined: metal-free tetrahydroxyphenyl porphyrin (THPP), THPP-Zn and the THPP-V metal complexes. Their biological application was also evaluated. Therefore, the in vitro study was carried out to assess their biological activity against Escherichia coli. The metal-porphyrin complexes exhibited highest activities against the bacterial strain Escherichia coli. at the highest concentration (175 μg/mL) and show better activity than the free base ligand (salts and blank solution). Results indicated a relation between Φ∆ and the inhibitory activity against Escherichia coli, thus, whereas higher is the Φ∆, higher is the inhibitory activity. The values of the Φ∆ and the inhibitory activity follows the tendency THPP-Zn > THPP > THPP-V. Furthermore, quantum chemical calculations allowed to gain deep insight into the electronic and optical properties of THPP-Zn macrocycle, which let to verify the most probable energy transfer pathway involved in the singlet oxygen generation.

In our previous report we first described a complex between lactoferrin (Lf) and ceruloplasmin (Cp) with K d ~ 1.8 μM. The presence of this complex in colostrum that never contains more than 0.3 μM Cp questions the reliability of K d value. We carefully studied Lf binding to Cp and investigated the enzymatic activity of the latter in the presence of Lf, which allowed obtaining a new value for K d of Cp–Lf complex. Lf interacting with Cp changes its oxidizing activity with various substrates, such as Fe2+, o-dianisidine (o-DA), p-phenylenediamine (p-PD) and dihydroxyphenylalanine (DOPA). The presence of at least two binding sites for Lf in Cp molecule is deduced from comparison of substrates’ oxidation kinetics with and without Lf. When Lf binds to the first site affinity of Cp to Fe2+ and to o-DA increases, but it decreases towards DOPA and remains unchanged towards p-PD. Oxidation rate of Fe2+ grows, while that of o-DA, p-PD and DOPA goes down. Subsequent Lf binding to the second center has no effect on iron oxidation, hampers DOPA and o-DA oxidation, and reduces affinity towards p-PD. Scatchard plot for Lf sorbing to Cp-Sepharose allowed estimating K d for Lf binding to high-affinity (~13.4 nM) and low-affinity (~211 nM) sites. The observed effect of Lf on ferroxidase activity of Cp is likely to have physiological implications.

Flavinogenic yeast overproduce riboflavin (RF) in iron-deprived media. In optimal growth media supplemented with Fe, hexavalent chromium 'Cr (VI)' treatment led to elevated RF synthesis in all cases of 37 flavinogenic strains studied. The level of RF production exceeded the rate observed at iron-deficient conditions. At sublethal Cr concentrations the RF oversynthesis over time correlated well with the growth-inhibitory adaptational period as manifested by the prolonged lag phase. The consecutive logarithmic biomass growth was accompanied by a drop in RF biosynthesis. Cr (VI)-induced RF overproduction was not a result of cellular iron level decrease. The treatment of yeast with Cr (VI) led to the stimulation of GTP-cyclohydrolase and RF-synthase activities, the key enzymes of the RF biosynthesis pathway.

Lead is an important toxic metal found in industrial communities. Due to the industrialization in the recent decade in Thailand, lead intoxication as a toxicant-related disorder becomes a new public health problem. A retrospective study on clinical presentation of hospitalized patients with diagnosis of lead intoxication during year 1990–1999 in King Chulalongkorn Memorial hospital, the largest Thai Red Cross Society Hospital, was performed. All 14 cases diagnosed with lead intoxication were identified in our series. Average age of the subjects was 25.55 ± 21.93 years old. Male predominance was detected in our series (male:female = 12:2). Two main groups of subjects as; (1) childhood aged below 10 years old (male:female = 4:2) and (2) adult aged between 24 and 60 years old (n = 8, all male), can be identified. For the first group, the clinical presentations were convulsion (n = 3), unexplained anemia (n = 1), attention deficit (n = 1) and asymptomatic (n = 1), respectively. All of the subjects in this group presented the history of living at the old battery plant area. Five of the six cases came from the same village. For the second group, the clinical presentations were unexplained abdominal pain (n = 5), chronic renal failure (n = 1), unexplained anemia (n = 1) and asymptomatic (n = 1), respectively. Most of the subjects (75%) in this group presented the history of working in the battery plant for more than 10 years. Another case presented the history of gunshot and residual bullet in the bone marrow. The other one left is an interesting case with the history of prolonged usage of ritual pill and holy paper incineration. Like other studies, battery plant had strong relation with the lead intoxication. Although the total identified cases are rather few, there may be more undetected asymptomatic lead intoxication cases in the community. Specific control of lead resulted from battery plant and monitoring of the workers as public health strategies are still recommended.

Zinc is a trace nutrient for the brain and a signal factor to serve for brain function. A portion of zinc is released from glutamatergic (zincergic) neuron terminals in the brain. Synaptic Zn2+ signaling is involved in synaptic plasticity such as long-term potentiaion (LTP), which is a cellular mechanism of memory. The block and/or loss of synaptic Zn2+ signaling in the hippocampus and amygdala with Zn2+ chelators affect cognition, while the role of synaptic Zn2+ signal is poorly understood, because zinc-binding proteins are great in number and multi-functional. Chronic zinc deficiency also affects cognition and cognitive decline induced by zinc deficiency might be associated with the increase in plasma glucocorticoid rather than the decrease in synaptic Zn2+ signaling. On the other hand, excess glutamatergic (zincergic) neuron activity induces excess influx of extracellular Zn2+ into hippocampal neurons, followed by cognitive decline. Intracellular Zn2+ dynamics, which is linked to presynaptic glutamate release, is critical for LTP and cognitive performance. This paper deals with insight into cognition from zinc as a nutrient and signal factor.

This study is to examine the effects of single nucleotide polymorphisms (SNPs) of SLC30A and SLC39A on seminal plasma zinc concentration. Blood and seminal plasma samples were collected from outpatients. SNPs of zinc transporters were analyzed by next Generation sequencing technology, and seminal plasma zinc concentration were determined by inductively coupled plasma optical emission spectrometry. Our date showed nine SNPs (SLC30A8 rs2466295, rs2466294, SLC30A10 c.-160 C>G, SLC39A8 rs9331, rs9705, rs151392, rs151393, SLC39A11 rs9912126, SLC39A14 rs1051708) were significantly associated with seminal plasma zinc concentration, and 14 SNPs (SLC30A8 rs2466295, rs2466294, SLC30A10 c.-160 C>G, SLC39A6 rs148550301, SLC39A8 rs9331, rs9705, rs151392, rs151393, SLC39A11 rs9912126, rs61736066, rs36041371 and SLC39A14 rs1051708, rs76963096, rs17060854) were found to be significantly associated with total zinc per ejaculate. The seminal plasma zinc concentrations and total zinc per ejaculate were associated with the number of SNPs, and decreased significantly when five SNPs (SLC39A8 rs9331, rs9705, rs151392, rs151393 and SLC39A14 rs1051708) were a combination of homozygous genotype. Our findings suggest that different zinc transporter SNPs may significantly affect seminal plasma zinc levels.

Zn(II) complexes with norfloxacin (NOR) in the absence or in the presence of 1,10-phenanthroline (phen) were obtained and characterized. In both complexes, the ligand NOR was coordinated through a keto and a carboxyl oxygen. Tetrahedral and octahedral geometries were proposed for [ZnCl2(NOR)]·H2O (1) and [ZnCl2(NOR)(phen)]·2H2O (2), respectively. Since the biological activity of the chemicals depends on the pH value, pH titrations of the Zn(II) complexes were performed. UV spectroscopic studies of the interaction of the complexes with calf-thymus DNA (CT DNA) have suggested that they can bind to CT DNA with moderate affinity in an intercalative mode. The interactions between the Zn(II) complexes and bovine serum albumin (BSA) were investigated by steady-state and time-resolved fluorescence spectroscopy at pH 7.4. The experimental data showed static quenching of BSA fluorescence, indicating that both complexes bind to BSA. A modified Stern–Volmer plot for the quenching by complex 2 demonstrated preferential binding near one of the two tryptophan residues of BSA. The binding constants obtained (K b ) showed that BSA had a two orders of magnitude higher affinity for complex 2 than for 1. The results also showed that the affinity of both complexes for BSA was much higher than for DNA. This preferential interaction with protein sites could be important to their biological mechanisms of action. The analysis in vitro of the Zn(II) complexes and corresponding ligand were assayed against Trypanosoma cruzi, the causative agent of Chagas disease and the data showed that complex 2 was the most active against bloodstream trypomastigotes.