Study of complexes of cadmium with some L-amino acids and vitamin-C by voltammetric technique

Voltammetric technique was used to study the binary and ternary complexes of cadmium with L-amino acids and vitamin-C (L-ascorbic acid) at pH =7.30 ± 0.01, µ = 1.0M KNO3 at 25ºC and 35ºC. Cd (II) formed 1:1:1, 1:1:2 and 1:2:1 complexes with L-lysine, L-ornithine, L-threonine, L-serine, L-phenylglycine, L-phenylalanine, L-glutamic acid and L-aspartic acid used as primary ligands and L-ascorbic acid used as secondary ligand. The trend of stability constant of complexes was L-lysine < L-ornithine < L-threonine < L-serine < L-phenylglycine < L-phenylalanine < L-glutamic acid < L-aspartic acid which can be explained on the basis of size, basicity and steric hindrance of ligands. The values of stability constant (log β) varied from 2.23 to11.33 confirm that these drugs i.e. L-amino acids or in combination with L-ascorbic acid or their complexes could be used against Cd (II) toxicity. The study has been carried out at 35ºC also to determine the thermodynamic parameters such as enthalpy change (ΔH), Free energy change (ΔG) and entropy change (ΔS) respectively.

Thyroid peroxidase activity is inhibited by amino acids

Normal in vitro thyroid peroxidase (TPO) iodide oxidation activity was completely inhibited by a hydrolyzed TPO preparation (0.15 mg/ml) or hydrolyzed bovine serum albumin (BSA, 0.2 mg/ml). A pancreatic hydrolysate of casein (trypticase peptone, 0.1 mg/ml) and some amino acids (cysteine, tryptophan and methionine, 50 µM each) also inhibited the TPO iodide oxidation reaction completely, whereas casamino acids (0.1 mg/ml), and tyrosine, phenylalanine and histidine (50 µM each) inhibited the TPO reaction by 54% or less. A pancreatic digest of gelatin (0.1 mg/ml) or any other amino acid (50 µM) tested did not significantly decrease TPO activity. The amino acids that impair iodide oxidation also inhibit the TPO albumin iodination activity. The inhibitory amino acids contain side chains with either sulfur atoms (cysteine and methionine) or aromatic rings (tyrosine, tryptophan, histidine and phenylalanine). Among the amino acids tested, only cysteine affected the TPO guaiacol oxidation reaction, producing a transient inhibition at 25 or 50 µM. The iodide oxidation inhibitory activity of cysteine, methionine and tryptophan was reversed by increasing iodide concentrations from 12 to 18 mM, while no such effect was observed when the cofactor (H2O2) concentration was increased. The inhibitory substances might interfere with the enzyme activity by competing with its normal substrates for their binding sites, binding to the free substrates or reducing their oxidized form.

Radiometric studies on the oxidation of (U-14C) L-amino acids by drug-susceptible and drug-resistant mycobacteria

A radiometric assay system has been used to study oxidation patterns of (U-14C) L-amino acids by drug-susceptible and drug-resistant mycobacteria. Drug-susceptible M. tuberculosis (H37Rv TMC 102 and Erdman) along with the drug-resistant organism M. tuberculosis (H37 Rv TMC 303), M. bovis, M. avium, M. intracellulare, M. kansasii and M. chelonei were used. The organisms were inoculated into a sterile reaction system with liquid 7H9 medium and one of the (U-14C) L-amino acids. Each organism displayed a different pattern of amino acid oxidation, but these patterns were not distinctive enough for identification of the organism. Complex amino acids such as proline, phenylalanine and tyrosine were of no use in identification of mycobacteria, since virtually all organisms failed to oxidize them. There was no combination of substrates able to separate susceptible from resistant organisms.

The influence of sugars and amino acids on the blood-feeding behaviour, oviposition and longevity of laboratory colony of Lutzomyia longipalpis (Lutz & Neiva, 1912) (Diptera: Psychodidae, Phlebotominae)

Schneider's Drosophila medium, a complex amino acid rich medium was tested alone and with seven different sugars for some aspects of the biology of Lutzomyia longipalpis. Statistically significant results were obtained when sucrose was used alone, indicating that among the sugars tested, this is still the most suitable and practical one for the maintenance of L. longipalpis colonies. However, the addition of Schneider's medium to a pool of different sugars, was suggested to be related with the acceptance of the first and second blood meals and to longevity, these being, obviously, quite relevant aspects when tansmission experiments are contemplated.

Modulating the electronic structure of amino acids: interaction of model lewis acids with anthranilic acid

On the basis of theoretical B3LYP calculations, Yáñez and co-workers (J. Chem. Theory Comput. 2012, 8, 2293) illustrated that beryllium ions are capable of significantly modulating (changing) the electronic structures of imidazole. In this computational organic chemistry study, the interaction of this β-amino acid and five model Lewis acids (BeF1+, Be2+, AlF2(1+), AlF2+, and Al3+) were investigated. Several aspects were addressed: natural bond orbitals, including second order perturbation analysis of intra-molecular charge delocalization and the natural population analysis atomic charges; molecular geometries; selected infrared stretching frequencies (C-N, C-O, and N-H), and selected ¹H-NMR chemical shifts. The data illustrate that this interaction can weaken the H-O bond and goes beyond strengthening the intra-molecular hydrogen bond (N...H-O) to cause a spontaneous transfer of the proton to the nitrogen atom in five cases generating zwitterion structures. Many new features are observed. Most importantly, the zwitterion structures include a stabilizing hydrogen bond (N-H...O) that varies in relative strength according to the Lewis acid. These findings explain the experimental observations of α-amino acids (for example: J. Am. Chem. Soc. 2001, 123, 3577) and are the first reported fundamental electronic structure characterization of β-amino acids in zwitterion form.

N-terminal amino acids of bovine alpha interferons are relevant for the neutralization of their antiviral activity

The structure-function relationship of interferons (IFNs) has been studied by epitope mapping. Epitopes of bovine IFNs, however, are practically unknown, despite their importance in virus infections and in the maternal recognition of pregnancy. It has been shown that recombinant bovine (rBo)IFN-alphaC and rBoIFN-alpha1 differ only in 12 amino acids and that the F12 monoclonal antibody (mAb) binds to a linear sequence of residues 10 to 34. We show here that the antiviral activities of these two IFNs were neutralized by the F12 mAb to different extents using two tests. In residual activity tests the antiviral activity dropped by more than 99% with rBoIFN-alphaC and by 84% with rBoIFN-alpha1. In checkerboard antibody titrations, the F12 mAb titer was 12,000 with rBoIFN-alphaC and only 600 with rBoIFN-alpha1. Since these IFNs differ in their amino acid sequence at positions 11, 16 and 19 of the amino terminus, only these amino acids could account for the different neutralization titers, and they should participate in antibody binding. According to the three-dimensional structure described for human and murine IFNs, these amino acids are located in the alpha helix A; amino acids 16 and 19 of the bovine IFNs would be expected to be exposed and could bind to the antibody directly. The amino acid at position 11 forms a hydrogen bond in human IFNs-alpha and it is possible that, in bovine IFNs-alpha, the F12 mAb, binding near position 11, would disturb this hydrogen bond, resulting in the difference in the extent of neutralization observed.

Attraction to amino acids by Lymnaea acuminata, the snail host of Fasciola species

Adult Lymnaea acuminata (average length 20-22 mm) were collected locally from lakes and low-lying submerged fields from Gorakhpur. The chemoattraction studies were made in round glass aquaria measuring 30 cm in diameter and filled to a depth of 10 mm with 500 ml dechlorinated tap water. Each aquarium was divided into four concentric zones. At the starting time of the assay 10 snails were placed on the circumference of outermost zone 0. Snail attractant pellets (SAP) were added simultaneously in the center of central zone 3. SAP of different amino acids were prepared at concentrations of 10, 20, 50, 80 and 100 mM/2% agar solution and, subsequently, spread to a uniform thickness of 5 mm. After cooling, SAP were cut in small pieces of 5 mm in diameter. Lymnaea acuminata's attraction to amino acids was studied using different amino acid concentrations in SAP. Pellets containing amino acids with non-polar R groups (proline and tryptophan), a charged polar group (arginine) and uncharged polar R groups (serine, citrulline and asparagine) were tested. The snails were more attracted to the uncharged polar R group amino acid serine than to other groups of amino acids. The preferred amino acid concentration was 80 mM. The attraction of snails to different amino acids was concentration dependent. Snails could discriminate amongst the different amino acids at > or = 50 mM.

Amino acid composition of parturient plasma, the intervillous space of the placenta and the umbilical vein of term newborn infants

The objective of the present study was to determine the levels of amino acids in maternal plasma, placental intervillous space and fetal umbilical vein in order to identify the similarities and differences in amino acid levels in these compartments of 15 term newborns from normal pregnancies and deliveries. All amino acids, except tryptophan, were present in at least 186% higher concentrations in the intervillous space than in maternal venous blood, with the difference being statistically significant. This result contradicted the initial hypothesis of the study that the plasma amino acid levels in the placental intervillous space should be similar to those of maternal plasma. When the maternal venous compartment was compared with the umbilical vein, we observed values 103% higher on the fetal side which is compatible with currently accepted mechanisms of active amino acid transport. Amino acid levels of the placental intervillous space were similar to the values of the umbilical vein except for proline, glycine and aspartic acid, whose levels were significantly higher than fetal umbilical vein levels (average 107% higher). The elevated levels of the intervillous space are compatible with syncytiotrophoblast activity, which maintain high concentrations of free amino acids inside syncytiotrophoblast cells, permitting asymmetric efflux or active transport from the trophoblast cells to the blood in the intervillous space. The plasma amino acid levels in the umbilical vein of term newborns probably may be used as a standard of local normality for clinical studies of amino acid profiles.

Elevated amniotic fluid amino acid levels in fetuses with gastroschisis

Our objective was to measure maternal plasma and amniotic fluid amino acid concentrations in pregnant women diagnosed as having fetuses with gastroschisis in the second trimester of pregnancy. Twenty-one pregnant women who had fetuses with gastroschisis detected by ultrasonography (gastroschisis group) in the second trimester and 32 women who had abnormal triple screenings indicating an increased risk for Down syndrome but had healthy fetuses (control group) were enrolled in the study. Amniotic fluid was obtained by amniocentesis, and maternal plasma samples were taken simultaneously. The chromosomal analysis of the study and control groups was normal. Levels of free amino acids and non-essential amino acids were measured in plasma and amniotic fluid samples using EZ:fast kits (EZ:fast GC/FID free (physiological) amino acid kit) by gas chromatography (Focus GC AI 3000 Thermo Finnigan analyzer). The mean levels of essential amino acids (histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine) and non-essential amino acids (alanine, glycine, proline, and tyrosine) in amniotic fluid were found to be significantly higher in fetuses with gastroschisis than in the control group (P < 0.05). A significant positive correlation between maternal plasma and amniotic fluid concentrations of essential and nonessential amino acids was found only in the gastroschisis group (P < 0.05). The detection of significantly higher amino acid concentrations in the amniotic fluid of fetuses with a gastroschisis defect than in healthy fetuses suggests the occurrence of amino acid malabsorption or of amino acid leakage from the fetus into amniotic fluid.

Plasma amino acids in pregnancy, placental intervillous space and preterm newborn infants

Plasma amino acid levels have never been studied in the placental intervillous space of preterm gestations. Our objective was to determine the possible relationship between plasma amino acids of maternal venous blood (M), of the placental intervillous space (PIVS) and of the umbilical vein (UV) of preterm newborn infants. Plasma amino acid levels were analyzed by ion-exchange chromatography in M from 14 parturients and in the PIVS and UV of their preterm newborn infants. Mean gestational age was 34 ± 2 weeks, weight = 1827 ± 510 g, and all newborns were considered adequate for gestational age. The mean Apgar score was 8 and 9 at the first and fifth minutes. Plasma amino acid values were significantly lower in M than in PIVS (166%), except for aminobutyric acid. On average, plasma amino acid levels were significantly higher in UV than in M (107%) and were closer to PIVS than to M values, except for cystine and aminobutyric acid (P < 0.05). Comparison of the mean plasma amino acid concentrations in the UV of preterm to those of term newborn infants previously studied by our group showed no significant difference, except for proline (P < 0.05), preterm > term. These data suggest that the mechanisms of active amino acid transport are centralized in the syncytiotrophoblast, with their passage to the fetus being an active bidirectional process with asymmetric efflux. PIVS could be a reserve amino acid space for the protection of the fetal compartment from inadequate maternal amino acid variations.

Amniotic fluid amino acid levels in non-immune hydrops fetalis: a case-control study

In a prospective case-control study, we compared the amniotic fluid amino acid levels in non-immune hydrops fetalis (NIHF) and normal fetuses. Eighty fetuses underwent amniocentesis for different reasons at the prenatal diagnosis unit of the Department of Obstetrics and Gynecology, Faculty of Medicine, Dicle University. Forty of these fetuses were diagnosed with NIHF. The study included 40 women each in the NIHF (mean age: 27.69 ± 4.56 years) and control (27.52 ± 5.49 years) groups, who had abnormal double- or triple-screening test values with normal fetuses with gestational ages of 23.26 ± 1.98 and 23.68 ± 1.49 weeks at the time of sample collection, respectively. Amniotic fluid amino acid concentrations (intra-assay variation: 2.26-7.85%; interassay variation: 3.45-8.22%) were measured using EZ:faast kits (EZ:faast GC/FID free (physiological) amino acid kit; Phenomenex, USA) by gas chromatography. The standard for quantitation was a mixture of free amino acids from Phenomenex. The levels of 21 amino acids were measured. The mean phosphoserine and serine levels were significantly lower in the NIHF group, while the taurine, α-aminoadipic acid (aaa), glycine, cysteine, NH4, and arginine (Arg) levels were significantly higher compared to control. Significant risk variables for the NIHF group and odds coefficients were obtained using a binary logistic regression method. The respective odds ratios and 95% confidence intervals for the risk variables phosphoserine, taurine, aaa, Arg, and NH4 were 3.31 (1.84-5.97), 2.45 (1.56-3.86), 1.78 (1.18-2.68), 2.18 (1.56-3.04), and 2.41 (1.66-3.49), respectively. The significant difference between NIHF and control fetuses suggests that the amniotic fluid levels of some amino acids may be useful for the diagnosis of NIHF.

Disturbance in hemoglobin metabolism and in vivo antimalarial activity of azole antimycotics

Plasmodium parasites degrade host hemoglobin to obtain free amino acids, essential for protein synthesis. During this event, free toxic heme moieties crystallize spontaneously to produce a non-toxic pigment called hemozoin or ß-hematin. In this context, a group of azole antimycotics, clotrimazole (CTZ), ketoconazole (KTZ) and fluconazole (FCZ), were investigated for their abilities to inhibit ß-hematin synthesis (IßHS) and hemoglobin proteolysis (IHbP) in vitro. The ß-hematin synthesis was recorded by spectrophotometry at 405 nm and the hemoglobin proteolysis was determined by SDS-PAGE 12.5%, followed by densitometric analysis. Compounds were also assayed in vivo in a malaria murine model. CTZ and KTZ exhibited the maximal effects inhibiting both biochemical events, showing inhibition of β-hematin synthesis (IC50 values of 12.4 ± 0.9 µM and 14.4 ± 1.4 µM respectively) and inhibition of hemoglobin proteolysis (80.1 ± 2.0% and 55.3 ± 3.6%, respectively). There is a broad correlation to the in vivo results, especially CTZ, which reduced the parasitemia (%P) of infected-mice at 4th day post-infection significantly compared to non-treated controls (12.4 ± 3.0% compared to 26.6 ± 3.7%, p = 0.014) and prolonged the survival days post-infection. The results indicated that the inhibition of the hemoglobin metabolism by the azole antimycotics could be responsible for their antimalarial effect.

Analysis of the chemical components of hydatid fluid from Echinococcus granulosus

Introduction The aim of this study was to explore the environment of Echinococcus granulosus (E. granulosus) protoscolices and their relationship with their host. Methods Proteins from the hydatid-cyst fluid (HCF) from E. granulosus were identified by proteomics. An inductively coupled plasma atomic emission spectrometer (ICP-AES) was used to determine the elements, an automatic biochemical analyzer was used to detect the types and levels of biochemical indices, and an automatic amino acid analyzer was used to detect the types and levels of amino acids in the E. granulosus HCF. Results I) Approximately 30 protein spots and 21 peptide mass fingerprints (PMF) were acquired in the two-dimensional gel electrophoresis (2-DE) pattern of hydatid fluid; II) We detected 10 chemical elements in the cyst fluid, including sodium, potassium, calcium, magnesium, copper, and zinc; III) We measured 19 biochemical metabolites in the cyst fluid, and the amount of most of these metabolites was lower than that in normal human serum; IV) We detected 17 free amino acids and measured some of these, including alanine, glycine, and valine. Conclusions We identified and measured many chemical components of the cyst fluid, providing a theoretical basis for developing new drugs to prevent and treat hydatid disease by inhibiting or blocking nutrition, metabolism, and other functions of the pathogen.

Water relations in physic nut according to climatic seasonality, in semiarid conditions

The objective of this work was to determine the effect of climatic seasonality on physic nut (Jatropha curcas), in field, under semiarid climate conditions. Stomatal conductance (g s), transpiration (E), soluble leaf carbohydrates (SLC), free amino acids (FAA) and total proteins (TP) were measured in leaves, in a commercial plantation in Northeast Brazil, during the summer and autumn. Plants showed high g s and E, as well as SLC, FAA and TP contents in the summer, which gradually decreased with the lower temperatures and photosynthetically active radiation during the autumn, despite the higher water availability. Even in conditions of adequate water availability, the combination of low temperatures and reduced light drastically decreased foliar metabolism.

Proteases virais: importantes alvos terapêuticos de compostos peptideomiméticos

Proteases catalyze the hydrolysis of peptide bonds of proteins and peptides to produce smaller peptides and free amino acids. These enzymes are involved in physiologic processes such as blood coagulation and cellular death, and are related to life cycle of several viruses, such as hepatitis C, dengue, and AIDS. These features make most of proteases very important therapeutic targets for new pharmaceutical compounds. The development of peptidemimetics with improved pharmacokinetic properties is driving extensive research in the field of viral protease inhibitors. The present paper aims to highlight the design and synthesis of peptidemimetics that are able to inhibit viral proteases related to hepatitis C, dengue, and AIDS.