University of Tehran Journal of Sciences, Islamic Republic of Iran 1016-1104 8 4 1997 12 01 ELUCIDATION OF pK VALUES FOR ACTIVE SITE OF HORSERADISH PEROXIDASE AND BINDING STUDY OF INTERACTION WITH N-PHENYL BENZHYDROXAMIC ACID USING A SPECIAL DIFFERENCE SPECTROPHOTOMETRIC TECHNIQUE - 31273 EN Journal Article 1970 01 01 The binding behavior of a competitive inhibitor, N-phenylbenzhydroxamic acid (BHA) against horseradish peroxidase (HRP) was studied in order to understand and predict the interaction mechanism of hydrogen donors with the enzyme. The dissociation constants of the complexes of HRP-BHA, HRP-donor and HRP-BHA-azide were estimated at specified conditions by difference spectroscopy. The binding site of BHA and that of hydrogen donor were also detected by spectroscopic titration of HRP in the presence of BHA and specific amino acid modifiers. A histidine binding site with pK = 6.40 was detected for the binding of BHA. On the other hand, activity-pH measurements showed that the maximum interaction of BHA with HRP occurs at a minimum point of activity at pH=6.40. The catalytic behavior of His 42 in the kinetic mechanism of enzyme action was also discussed

University of Tehran Journal of Sciences, Islamic Republic of Iran 1016-1104 8 4 1997 12 01 PRODUCTION, RELEASE AND THERMAL CHARACTERIZATION OF CELLULOLYTIC ENZYME FROM CELLULOMONAS sp. STRAIN "0" - 31274 EN Journal Article 1970 01 01 Cellulase production by a Cellulomonas sp., isolated in 1985 from forest humus soil along the border of the Caspian Sea in Iran, was investigated. This strain secreted endo-and exo-cellulases in the culture medium, but some of the enzymes produced remained cell membrane bound. Cell bound enzymes were released by various treatments. The highest amount of endo-glucanase (up to 95%) and exo-glucanase (62%) was released when the cells were treated with 1% Tween 80 for 300 and 60 minutes, respectively. No extracellular or cell membrane bound ?-glucosidase was obtained. Optimum temperature for the endo-glucanase and exo-glucanase activities was 50°C and optimum pH was 7 for both enzymes. Thermal stability of enzymes was measured at 30 to 50°C and was compared with that of endo- and exo-glucanses from mesophilic fungi such as Neurospora crassa, Trichoderma viri& and Pencillium funiculosum. It was found that the thermal stability of endo- and exo-glucanases from Cellulomntas sp. strain "0"w as the same as that of fungal enzymes up to 37?C, however, at higher temperatures these enzymes lost their activities faster than the fungal cellulases

University of Tehran Journal of Sciences, Islamic Republic of Iran 1016-1104 8 4 1997 12 01 A SIMPLE MODEL FOR THE ESTIMATION OF DIELECTRIC CONSTANTS OF BINARY SOLVENT MIXTURES - 31275 EN Journal Article 1970 01 01 A simple and reliable method for quick estimation of the dielectric constant of a binary solvent mixture is proposed. The validity of the proposed method has been tested for a broad range of binary solvent mixtures

University of Tehran Journal of Sciences, Islamic Republic of Iran 1016-1104 8 4 1997 12 01 DIFFERENTIAL PULSE POLAROGRAPHIC DETERMINATION OF OSMIUM BY CATALYSIS OF PYROGALLOL-RED BROMATE REACTION - 31276 EN Journal Article 1970 01 01 A highly sensitive differential pulse polarographic (DPP) method has been developed for the determination of trace amounts of osmium, based on the catalytic effect of osmium (VIII) on the oxidation of pyrogallol red (PGR) by sodium bromate at pH 7.00 and 25.0 0.1 ? C. The reaction rate was monitored by measuring the differential pulse cathodic current of the oxidation product of PGR and bromate. Various parameters such as the effect of pH, reagents concentrations, time, temperature and interference of a number of cations and anions on the estimation of osmium have been studied to optimize the conditions for determination of osmium. The concentration of osmium in the range of 0.1- 300 ng ml has been determined. The limit of detection was 0.02 ng ml . The precision and accuracy of the method are reported

University of Tehran Journal of Sciences, Islamic Republic of Iran 1016-1104 8 4 1997 12 01 SYNTHESIS OF 1,2,4-TRIAZINO [3,4-C] [I ,2,4] BENZOTRIAZINE, A NOVEL HETEROCYCLIC SYSTEM - 31277 EN Journal Article 1970 01 01 3-Mercapto-1,2,4 benzotriazine (1) was methylated by methyl iodide in the presence of base to afford 1,2-dihydro-3-methyhercapto-1, 2,4 benzotriazine (2). The latter was reacted with hydrazine hydrate to give the corresponding 3-hydrazine derivative (3). Compound (3) on condensation with phenacyl bromide gave 3- phenacyl hydrazino l,2,4-benzotriazine (4). PPA cyclization of the ketone (4) yielded lH, 2H, 10H-4-phenyl-triazino [3,4-c]- 1,2,4-benzotriazine (5). Triazino benzotriazine (5) is a novel heterocyclic system and is reported for the first time.

University of Tehran Journal of Sciences, Islamic Republic of Iran 1016-1104 8 4 1997 12 01 EXTENSION OF LINEAR ISOTHERM REGULARITY TO LOWER DENSITY RANGE - 31278 EN Journal Article 1970 01 01 The general equation of state which was found for dense fluids, both compressed liquids and dense supercritical fluids, namely "Linear Isotherm Regularity," is extended to the lower density range, specifically for densities lower than the Boyle density. This new equation of state which is called "ELIR" is shown to be compatible with the equations of state based on statistical-mechanical theory, although ELIR gives a more accurate density at high pressures. This equation of state has been tested with experimental data for different fluids (Ar,N , O , CO, CH , C H , CH 0H ,H ) for both vapor and compressed liquid phases. The ELIR is able to predict the critical isotherm and also both of the coexistence phases at equilibrium can be expressed by a single ELIR equation of state

University of Tehran Journal of Sciences, Islamic Republic of Iran 1016-1104 8 4 1997 12 01 PALYNOSTRATIGRAPHY AND PACAIEOGEOGRAPHY OF EARLY PEFIMM STRATA IN THE ZAGROS BASIN, SOUTHEAST SOUTHWEST IRAN - 31279 EN Journal Article 1970 01 01 A totall of 500 Early Permian samples from the Chal-i-Sheh Formation in the Zagros Basin were examined palynollogically in order to determine the stratigraphical age of the formation and to assess the palaeogeopaphicd relatianships of this basin to the Southern and Northern Hemispheres during the Early Permian. Fifty-eight taxa were recorded including 46 pollen, 10 spore and 2 acritarch species, which permitted the establishment of the age of the formation. Quantitatively, pollen contributed 98 percent, spores 1.5 percent, and acritarchs 0.5 percent of the total assemblages. The high relative percentage of gymospermous pollen taxa suggests a relatively cold condition which was in favor of gymnospernous plants at the beginning of the Early Permian, Comparison of the taxa recorded from the Early Permian strata of the Zagros Basin with those reported from other parts of the world indicates that the Zagros Basin was part of the Gondwanan Supercontinent located on the southern shore of Tethys sea during the Permian period

University of Tehran Journal of Sciences, Islamic Republic of Iran 1016-1104 8 4 1997 12 01 FOCAL POINT AND FOCAL K-PLANE - 31280 EN Journal Article 1970 01 01 This paper deals with the basic notions of k-tautimmersions . These notions come from two special cases; that is, tight and taut immersions. Tight and taut based on high and distance functions respectively and their basic notions are normal bundle, endpoint map, focal point, critical normal. We generalize hight and distance functions to cylindrical function and define basic notions of k-taut immersions such as k-plane normal bundle , end k-plane map, focal k-plane, and critical k-plane normal. Then we prove index theorems for cylindrical function similar to the standard index theorems of distance function . In this way, the key point is the relation between focal point and focal k-plane

University of Tehran Journal of Sciences, Islamic Republic of Iran 1016-1104 8 4 1997 12 01 FLOWS AND UNIVERSAL COMPACTIFICATIONS - 31281 EN Journal Article 1970 01 01 The main purpose of this paper is to establish a relation between universality of certain P-compactifications of a semitopological semigroup and their corresponding enveloping semigroups. In particular, we show that if we take P to be the property that the enveloping semigroup of a compactification of a semitopological semigroup s is left simple, a group, or the trivial singleton semigroup, then the universal P- compactification of S would be the distal, the right simple, or the right zero compactification , respectively

University of Tehran Journal of Sciences, Islamic Republic of Iran 1016-1104 8 4 1997 12 01 EFFECT OF FUSION REACTION PRODUCTS HEATING ON THE VOLUME IGNITION OF DT AND D3He FUEL PELLETS - 31282 EN Journal Article 1970 01 01 Laser fusion simulations are carried out for DT and D- He pellets by using a hydrodynamic code including heating from all charged reaction products and neutrons. It is shown that the inclusion of the side reactions and heating from all reaction products in the fuel pellets have an appreciable effect on the plasma temperature, the ICF drive energy requirement, fusion gain and the ignition conditions. The total input energy is decreased and the burn efficiency and total gain are increased compared to the results of simple volume ignition calculations

University of Tehran Journal of Sciences, Islamic Republic of Iran 1016-1104 8 4 1997 12 01 THE THEORY OF PHOTOTHERMAL LENSING SPECTROSCOPY - 31283 EN Journal Article 1970 01 01 A general theoretical description of dual-beam photothermallensing spectroscopy is given. The results are valid for most general conditions, that is, for flowing as well as stationary media, for optically thick as well as optically thin media, and also for any transverse modes of incident pump beams