α-OXIDASE ACTIVITY IN PLANTS AS PROMOTOR OF ELECTRONIC ENERGY

Abstract The a-oxidase activity of higher plants acting on long chain fatty acids generates the lower aldehyde in the ground state; however if chlorophyll or chioroplasts are present the chlorophylls are excited most likely by a chemically initiated electron exchange (CIEEL) luminescence process with the putative a-peroxylactone intermediate. When the aldehyde is substituted for the acid, the lower aldehyde appears in the triplet state. The chiral discrimination observed in the quenching by D- and L-tryptophan of the chlorophyll sensitized emission indicates that the triplet aldehyde is generated within the enzymatic preparation and transfers energy while still bound to the enzyme.
Chlorophylls in chioroplasts are excited by addition of a long chain fatty acid or aldehyde. The mechanism, however, is unknown.     

DETECTION OF DNA-PSORALEN PHOTOADDUCTS in situ

Abstract— An immunological method, with the use of specific immune serum, has been developed for detection of 8-methoxypsoralen (8-MOP) photoadducts to DNA, formed in situ in cell nuclei, after combined treatment with 8MOP and UV-A irradiation (Zarçbska et al. , 1978). Lymphocytes fixed on slides or in suspension, and cryostat sections of different mammalian tissues, served as antigenic substrate, after treatment with 8-MOP and UV-A in vitro. Specific fluorescence in these substrates was detected in the nuclei after treatment with 30 ˜ 140 kJ/m² UV-A in the presence of 0.1-0.3 μg/cm² 8-MOP. PHA-stimulated-lymphocytes appeared to be the most sensitive substrate.
However, hairless mice treated with high doses of UV-A in vivo , 70 ˜ 360 kJ/m² did not reveal a specific fluorescence of epidermal nuclei, unless a high local concentration of 8-MOP was attained.
The apparent discrepancy in the level of photoadduct detection between the in vitro and in vivo treated specimens was explained by the low number of DNA-8-MOP-photoadducts formed in vivo under these experimental conditions. The relevance of these findings to the role of DNA-8-MOP-photoadducts formed during PUVA photochemotherapy is discussed.     

X-Ray Structure and Proton NMR Study of a Hexacoordinated Lithium Complex

The structure of the lithium complex with1,3,5-tris[oxymethylene(N,N-dicyclohexyl)carboxyamido]cyclohexanehas been determined by the X-ray method.The compound is triclinic, space group P¯1,a = 15.623(3), b = 19.279(4),c = 19.295(4)Å = 102.32(3), = 92.45(3), = 105.67(3)0, V = 5436(2)Å3, Z = 4. Itscomposition is represented by the formulaC48H82N3O6LiI 0.5H2O. The lithium cationis encapsulated in a polar pseudo-cavity of six oxygen atoms of the ligandmolecule and displays a distorted trigonal prism coordination. The conformationof the ligand in the solid state complex has been compared with the conformationof the complex in solution determined by 1H-NMR measurements.Supplementary data relevant to this publication have been deposited with the British Library, No. SUP 82224 (21 pages).     

CHEMILUMINESCENCE AND FLUORESCENCE OF THE EUROPIUM IONS-ADENINE NUCLEOTIDES SYSTEM AND ITS POSSIBLE BIOLOGICAL SIGNIFICANCE

Abstract— Chemiluminescence of the Eu(II)/Eu(III)-adenine nucleotide-H₂O₂ system and fluorescence of the Eu(III)-adenosine triphosphate system have been investigated. The spectral distribution of the chemiluminescence emission has shown an occurrence of three main bands (Λ=470–480,590–620 and ca. 700 nm). The energy transfer process from the adenosine triphosphate molecules to the Eu(III) ions has been observed in the fluorescence spectrum. The examined chemiluminescence and fluorescence spectra show that these both kinds of emission originate from the ⁵ D _***τ⁷F_*** ( n =1–4) transitions in the Eu(III) ions.     

Evaluation of a novel nanocrystalline hydroxyapatite powder and a solid hydroxyapatite/Chitosan-Gelatin bioceramic for scaffold preparation used as a bone substitute material

Artificially fabricated hydroxyapatite (HAP) shows excellent biocompatibility with various kinds of cells and tissues which makes it an ideal candidate for a bone substitute material. In this study, hydroxyapatite nanoparticles have been prepared by using the wet chemical precipitation method using calcium nitrate tetra-hydrate [Ca(NO₃)₂.4H₂O] and di-ammonium hydrogen phosphate [(NH₄)₂ HPO₄] as precursors. The composite scaffolds have been prepared by a freeze-drying method with hydroxyapatite, chitosan, and gelatin which form a 3D network of interconnected pores. Glutaraldehyde solution has been used in the scaffolds to crosslink the amino groups (|NH₂) of gelatin with the aldehyde groups (|CHO) of chitosan. The X-ray diffraction (XRD) performed on different scaffolds indicates that the incorporation of a certain amount of hydroxyapatite has no influence on the chitosan/gelatin network and at the same time, the organic matrix does not affect the crystallinity of hydroxyapatite. Transmission electron microscope (TEM) images show the needle-like crystal structure of hydroxyapatite nanoparticle. Scanning Electron Microscope (SEM) analysis shows an interconnected porous network in the scaffold where HAP nanoparticles are found to be dispersed in the biopolymer matrix. Fourier transforms infrared spectroscopy (FTIR) confirms the presence of hydroxyl group (OH^-) , phosphate group (PO^3-₄) , carbonate group (CO^2-₃) , imine group (C=N), etc. TGA reveals the thermal stability of the scaffolds. The cytotoxicity of the scaffolds is examined qualitatively by VERO (animal cell) cell and quantitatively by MTTassay. The MTT-assay suggests keeping the weight percentage of glutaraldehyde solution lower than 0.2%. The result found from this study demonstrated that a proper bone replacing scaffold can be made up by controlling the amount of hydroxyapatite, gelatin, and chitosan which will be biocompatible, biodegradable, and biofriendly for any living organism.     

Thermal Explosion with Variable Thermal Conductivity: Criticality and Its Disappearance

Thermal stability of reacting masses, whose thermal conductivityis a function of temperature, is investigated. Some generalresults relating to criticality and its disappearance are presented.A particular study is made of the disappearance of criticalityfor the slab geometry with infinite Biot number (Frank-Kamenetskiiconditions) for both linear and exponential forms for the temperaturedependence of conductivity.     

CHEMIEXCITATION IN THE ARACHIDONIC ACID CASCADE

As investigated in neutrophils, the very weak luminescence accompanying the arachidonic acid cascade is associated with the lipoxygenase pathway. The emission is dramatically enhanced by energy transfer to chlorophyll a. The number of chlorophyll molecules excited to the fluorescent state per oxygen consumed, (the S1/O2 ratio), equal to the product of the quantum yields of chemiexcitation and of energy transfer, is 5.4 x 10(-6). The quantum yield of chemiexcitation is inferred to be higher than 1 x 10(-3). The two most likely chemiexcitation routes point to triplet conjugated carbonyls as the most likely candidates for the excited species that transfer to chlorophyll. As such the emission intensity may reflect the level of hydroperoxyeicosatetraenoic acid. This is the first case where addition of a biotic substrate to a cellular system results in substantial generation of electronic excited states without any drastic loss of cell viability. Whether the formation of excited states in the arachidonic acid cascade in neutrophils is accidental or has a biological role is an open question.     

The basic reproduction ratio for a model of directly transmitted infections considering the virus charge and the immunological response

Correspondent author email: hyunyang{at}ime.unicamp.br In order to describe mathematically the transmission of microparasites,especially directly transmitted infections, it is usual to setup differential equations assuming the mass action law and ahomogeneously mixed population. In this paper we analyze sucha model taking into account heterogeneity with respect to theinfectivity, that is, the variability in the evolution of theinteraction between parasite and the human host during the infectiousperiod. The well established biological phenomenon of initialincrease in parasite abundance followed by its decrease, dueto the interaction between the host's immunological responseand the parasite, has thus been taken into account The variableamount of microparasites eliminated by an infectious individual,and the different (heterogeneous) immunological response buildup by the host when in interaction with parasite are presentin the model. The analytical expression for the basic reproductionratio is derived through stability analysis.     

State models and asymptotic behaviour of 2D positive systems

Homogeneous 2D positive systems are 2D state-space models whosevariables are alwalys nonnegative and, consequently, are describedby a pair of nonnegative square matrices (A, B). In the paper,the properties of these pairs are discussed both in the generalcase and under particular assumptions like finite memory, separability,and property L. Various aspects of the positive asymptotic dynamic are considered;in particular, sufficient conditions are provided guaranteeingthat the local states are eventually strictly positive. Finally,some results on the convergence of the states towards a constantasymptotic distribution are presented.     

Modelling the metabolic action of human and rat CYP1A2 and its relationship with the carcinogenicity of heterocyclic amines

Cytochrome P450 (CYP) is a family of enzymes responsible for organism detoxification. However, some of the members of the CYP1A subfamily also catalyse the activation of heterocyclic amines (HAs), present in cooked meat, to carcinogenic compounds which have been shown to increase the risk of breast, colorectal and lung cancer. In humans, CYP1A2 is the enzyme with the most significant action in HA metabolism but in rodents CYP1A1 is also important in this biotransformation. Understanding the metabolic action of these enzymes is essential to predict the factors that enable the formation of the carcinogenic products. We have built two models of CYP1A2, one for the human enzyme and one for the rat homologue. The templates chosen include the only X-ray structure published to date for a mammal CYP, a quimeric C2A5 from rabbit, as well as CYPs belonging to Bacillus megaterium (CYPBm-3), Pseudomonas putida (CYPcam), Pseudomonas sp. (CYPterp), and Saccharopolyspora erythraea (CYPeryf). Two HAs, MeIQ (2-amino-3,4-dimethylimidazo[4,5-?]quinoline) and MeIQx (2-amino-3,8-dimethylimidazo[4,5-?]quinoxaline), known substrates of human and rat CYPIA2, were docked in the active site of the models, providing information regarding the different catalytic rates associated with the metabolisms in both enzymes. This is important for analysing the behaviour of animal models concerning the testing of anticancer drugs.