A product inhibition study on adenosine deaminase by spectroscopy and calorimetry

Kinetic and thermodynamic studies have been made on the effect of the inosine product on the activity of adenosine deaminase in a 50 mM sodium phosphate buffer, pH 7.5, at 27 degrees C using UV spectrophotometry and isothermal titration calorimetry (ITC). A competitive inhibition was observed for inosine as a product of the enzymatic reaction. A graphical-fitting method was used for determination of the binding constant and enthalpy of inhibitor binding by using isothermal titration microcalorimetry data. The dissociation-binding constant is equal to 140 microM by the microcalorimetry method, which agrees well with the value of 143 microM for the inhibition constant that was obtained from the spectroscopy method     

Cadmium-induced changes in antioxidant enzyme activities in rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L. cv. Dongjin)

We studied how the relationship between cadmium (Cd) toxicity and oxidative stress influenced the growth, photosynthetic efficiency, lipid peroxidation, and activity of ntioxidative enzymes in the roots and leaves of rice(Oryza sativa L Dongjin). Plants were exposed to Cd for 21 d. Both seedling growth and photosynthetic efficiency decreased gradually with increasing cadmium concentrations. Lipid peroxidation increased slowly in both roots and leaves, causing oxidative stress. However, each tissue type responded differently to Cd concentrations with regard to the induction/ inhibition of antioxidative enzymes. The activity of Superoxide dismutase (SOD) increased in both roots and leaves. Ascorbate peroxidase (APX) activity increased in leaves treated with up to 0.25 μM Cd, then decreased gradually at higher concentrations. In contrast, APX activity in roots increased and remained constant between 0.25 and 25 μM Cd. Enhanced peroxidase (POD) activity was recorded for treatments with up to 25/M Cd, gradually decreasing at higher concentrations in the leaves but remaining unchanged in the roots. Catalase (CAT) activity increased in the roots, but decreased in the leaves, whereas the activity of glutathione reductase (GR) was enhanced in both roots and leaves, where it remained elevated at higher Cd concentrations. These results suggest that rice seedlings tend to cope with free radicals generated by Cd through coordinated, enhanced activities of the antioxidative enzymes involved in detoxification.     

Evolutionary relationships among heterokont algae (the autotrophic stramenopiles) based on combined analyses of small and large subunit ribosomal RNA

In order to study the phylogenetic relationships within the stramenopiles, and particularly among the heterokont algae, we have determined complete or nearly complete large-subunit ribosomal RNA sequences for different species of raphidophytes, phaeophytes, xanthophytes, chrysophytes, synurophytes and pinguiophytes. With the small- and large-subunit ribosomal RNA sequences of representatives for nearly all known groups of heterokont algae, phylogenetic trees were constructed from a concatenated alignment of both ribosomal RNAs, including more than 5,000 positions. By using different tree construction methods, inferred phylogenies showed phaeophytes and xanthophytes as sister taxa, as well as the pelagophytes and dictyochophytes, and the chrysophytes/synurophytes and eustigmatophytes. All these relationships are highly supported by bootstrap analysis. However, apart from these sister group relationships, very few other internodes are well resolved and most groups of heterokont algae seem to have diverged within a relatively short time frame.     

Design,synthesis, and biological evaluation of a cephalosporin-monohydroguaiaretic acid prodrug activated by a monoclonal antibody-beta-lactamase conjugate

A novel cephalosporin derivative of monohydroguaiaretic acid (cephem-M(3)N, 7) was synthesized and found to possess anticancer activity against human leukemia (K562), breast carcinoma (MCF7), human lung cancer (A549), human colon cancer (Colo205) and pancreatic cancer cells (Capan2 and MiaPaCa2). A tumor targeting fusion protein (dsFv3-beta-lactamase) was also used in conjunction with cephem-based M(3)N 7 and its potency toward K562, MCF7, A549, Colo205, Capan2, and MiaPaCa2 was found to approach that of the free M(3)N (4). In the presence of dsFv3-beta-lactamase, tumor cells were found to be much more susceptible to conjugate 7 than normal human embryonic lung (HEL) cells and normal fibroblasts (Hef522). These notions provide a new approach to the use of nordihydroguaiaretic acid (NDGA) and its derivatives for antitumor therapy.     

Solvent effects on the stability of nifuroxazide complexes with cobalt(II), nickel(II) and copper(II) in alcohols

A spectrophotometric study of the complexation of nifuroxazide with cobalt(II), nickel(II) and copper(II) was carried out in different alcohols. The formation of a complex in each case is reported and their stability constants have been calculated. For a given solvent, the stability of the complexes increases from cobalt to copper. In the case of copper(II), the stability varies as an inverse function of the dielectric constant of the solvent. A possible structure of the complex is proposed.     

Biological activity of palladium(II) and platinum(II) complexes of the acetone Schiff bases of S-methyl- and S-benzyldithiocarbazate and the X-ray crystal structure of the [Pd(asme)2] (asme=anionic form of the acetone Schiff base of S-methyldithiocarbazate) complex

Palladium(II) and platinum(II) complexes of general empirical formula, [M(NS)(2)] (NS=uninegatively charged acetone Schiff bases of S-methyl- and S-benzyldithiocarbazate; M=Pt(II) and Pd(II)) have been prepared and characterized by a variety of physicochemical techniques. Based on conductance, IR and electronic spectral evidence, a square-planar structure is assigned to these complexes. The crystal and molecular structure of the [Pd(asme)(2)] complex (asme=anionic form of the acetone Schiff base of S-methyldithiocarbazate) has been determined by X-ray diffraction. The complex has a distorted cis-square planar structure with the ligands coordinated to the palladium(II) ions as uninegatively charged bidentate NS chelating agents via the azomethine nitrogen and the mercaptide sulfur atoms. The distortion from a regular square-planar geometry is attributed to the restricted bite angles of the ligands. Antimicrobial tests indicate that the Schiff bases exhibit strong activities against the pathogenic bacteria, Bacillus subtilis (mutant defective DNA repair), methicillin-resistant Staphylococcus aureus, B. subtilis (wild type) and Pseudomonas aeruginosa and the fungi, Candida albicans (CA), Candida lypotica (2075), Saccharomyces cerevisiae (20341) and Aspergillus ochraceous (398)-the activities exhibited by these compounds being greater than that of the standard antibacterial and antifungal drugs, streptomycin and nystatin, respectively. The palladium(II) and platinum(II) complexes are inactive against most of these organisms but, the microbe, Pseudomonas aeruginosa shows strong sensitivity to the platinum(II) complexes. Screening of the compounds for their cytotoxicities against T-lymphoblastic leukemia cancer cells has shown that the acetone Schiff base of S-methyldithiocarbazate (Hasme) exhibits a very weak activity, whereas the S-benzyl derivative (Hasbz) is inactive. However, the palladium(II) complexes exhibit strong cytotoxicities against this cancer; their activities being more than that of the standard anticancer drug, tamoxifen. The [Pt(asme)(2)] complex exhibits a very weak cytotoxicity, whereas [Pt(asbz)(2)] is inactive against leukemic cells.     

Effect of acidity on the enantiomeric resolution of thyroxine and tocainide by HPLC on a (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid column

Enantiomeric resolution of thyroxine and tocainide was achieved on a (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid column. The mobile phases were methanol/water (4:1, v/v) and methanol/water containing 5 mM sulfuric acid (4:1, v/v) for tocainide and thyroxine respectively. The flow rate was 0.5 ml/min. The effect of the acidity on the chiral resolution of these drugs was studied. Detection was at 220 nm for both drugs. The values of alpha and Rs were 2.08-3.11 and 1.00-2.60, respectively, for thyroxine while the values of alpha and Rs were 1.13-1.26 and 0.10-1.30, respectively, for tocainide.     

The effects of centrally administered apelin-13 on food intake, water intake and pituitary hormone release in rats

Apelin is the recently identified endogenous ligand for the G-protein-coupled receptor, APJ. Preproapelin and APJ mRNA are found in hypothalamic regions known to be important in the regulation of food and water intake, and pituitary hormone release. The effects of intracerebroventricular (ICV) administration of pyroglutamylated apelin-13 on food and water intake and pituitary hormone release in rats were investigated. Apelin-13 had little effect on food intake, but dose-dependently increased drinking behaviour and water intake at 1 h. Apelin-13 (10 nmol) increased water intake by up to sixfold compared to saline. Compared to saline control, apelin-13 (10 nmol) significantly increased plasma ACTH and corticosterone and decreased plasma prolactin, LH and FSH at 30 min. In vitro, apelin-13 stimulated the release of CRH and AVP from hypothalamic explants, but had no effect on NPY release. These results suggest that apelin may play an important role in the hypothalamic regulation of water intake and endocrine axes.     

Relaxation kinetics and the glassiness of proteins: the case of bovine pancreatic trypsin inhibitor

Folded proteins may be regarded as soft active matter under physiological conditions. The densely packed hydrophobic interior, the relatively molten hydrophilic exterior, and the spacer connecting these put together a large number of locally homogeneous regions. For the case of the bovine pancreatic trypsin inhibitor, with the aid of molecular dynamics simulations, we have demonstrated that the kinetics of the relaxation of the internal motions is highly concerted, manifesting the protein's heterogeneity, which may arise from variations in density, local packing, or the local energy landscape. This behavior is characterized in a stretched exponential decay described by an exponent of approximately 0.4 at physiological temperatures. Due to the trapped conformations, configurational entropy becomes smaller, and the associated stretch exponent drops to half of its value below the glass transition range. The temperature dependence of the inverse relaxation time closely follows the Vogel-Tamman-Fulcher expression when the protein is biologically active.     

Vascular architecture and patchy nutrient availability generate within-plant heterogeneity in plant traits important to herbivores

Within-plant heterogeneity in growth, morphology, and chemistry is ubiquitous, and is commonly attributed to differences in tissue age, light availability, or previous damage by herbivores. Although these factors are important, we argue that plant vascular architecture is an underappreciated determinant of heterogeneity. Vascular architecture can restrict the transport of resources (nutrients, photosynthate, hormones, etc.) to within specific sectors of the plant: this is referred to as sectoriality. Although studies have documented sectoriality in the transport of isotopes and dyes from roots to shoots, the ecological consequences of this sectoriality remain poorly understood. We tested the hypothesis that spatial variation in belowground nutrient availability combined with sectorial transport results in localized "fertilization" of aboveground plant parts and generates heterogeneity in traits important to herbivores. Our split-root experiments with tomato (Lycopersicon esculentum Mill) clearly demonstrate that fertilization to isolated lateral roots generates heterogeneity in leaf morphology, phenolic chemistry, and side-shoot growth. Specifically, leaflets with direct connections to these lateral roots were larger and had lower levels of rutin and chlorogenic acid than did leaflets in other sectors lacking direct vascular connections. Moreover, side-shoot production was greater in the connected sectors. We discuss the implications of this heterogeneity for plant-herbivore interactions.