JSCS Vol 61, No. 7
 
J. Serb. Chem. Soc. 61(7)517-522(1996) 
UDC 547/.9:541.183.12 
JSCS-2258 
Original scientific paper

GLYCIDYL ESTERS SYNTHESIS CATALYSED BY ION-EXCHANGE RESINS

DUSAN Z. MIJIN, IVANA D. OSTRIC and MILICA M. MISIC-VUKOVIC

Faculty of Technology and Metallurgy, University of Belgrade 
Karnegijeva 4, P.O.Box 494, YU-11001, Belgrade, Yugoslavia

(Received 14 November 1995)
Ion-exchange resins not previously used for this purpose were employed to study the synthesis of glycidyl esters. The reaction was carried out both with free acids and their sodium salts. The model reaction was the synthesis of glycidyl stearate. Crude glycidyl stearate was afforded in yields greater than 90% in a nonaquous, but not anhydrous system with GC purity above 99%. The phase-transfer catalytic (PTC) mechanism is proposed for the investigated reaction.

Key words: Glycidyl stearate, phase transfer catalysis, ion-exchange resins

J. Serb. Chem. Soc. 61(7)523-528(1996) 
UDC 547.743/.745 
JSCS-2259 
Original scientific paper

CYCLOADDITION REACTIONS OF AZOMETHINE YLIDES GENERATED BY 
1,2 PROTOTROPY FROM IMINES

SUREN HUSINEC*, LJILJANA MILOVANOVIC** and VLADIMIR SAVIC**

*Institute of Chemistry, Technology and Metallurgy, Department of Chemistry, Njegoseva 12, POB 815, YU-11001 Belgrade 
**Faculty of Pharmacy, Department of Organic Chemisty, Vojvode Stepe 450, YU-11000 Belgrade, Yugoslavia

(Received 7 December 1995)
The in situ formation of azomethine ylides by condensing an amino ester and an aldehyde followed by cycloaddition to the activated double bond was investigated. Different types of substituted pyrrolidines were synthesised by this methodology.

Key words: cycloaddition reaction, azomethine ylides, 1,2 prototropy, 1,3 dipolar cycloaddtion, imines, amino ester, pyrrolidine

J. Serb. Chem. Soc. 61(7)529-533(1996) 
UDC 543.866.002.2 
JSCS-2260 
Original scintific paper

PRODUCTION, PURIFICATION AND SOME PROPERTIES OF EXTRACELLULAR BACTERIOLYTIC ENZYMES PRODUCED BY STREPTOMYCES HYGROSCOPICUS

IVANKA KARADZIC*, GORDANA GOJGIC-CVIJOVIC** and JOVAN VUCETIC***

*Faculty of Medicine, Institute of Chemistry, Visegradska 26, YU-11000 Belgrade, 
** Institute of Chemistry, Technology and Metallurgy, Department of Chemistry, Njegoseva 12, P.O.Box 815, YU-11001 Belgrade and 
***Faculty of Chemistry, Akademski trg 16, YU-11000 Belgrade, Yugoslavia

(Received 17 August 1995)
A strain Streptomyces hygroscopicus was isolated from a soil sample from Vojvodina, Yugoslavia. From the fermentation broth of this antibiotic-producing strain an extracellular proteolytic complex was isolated. By purification of the crude proteolytic complex, bacteriolytic enzymes were obtained. The bacteriolytic preparation, active toward heat-killed E. coli, was analyzed by SDS-PAGE with substrate (E. coli)-containing gels. Three bands, as distinct bacteriolytic enzymes, were detected. Their molecular mass was estimated to be approximately 42000D, 27000D and less than 10000D for small bacteriolytic enzyme(s). Bacteriolytic enzymes are metallo-enzymes.

Key words: Streptomyces, proteolytic, bacteriolytic, extracellular, enzyme

J. Serb. Chem. Soc. 61(7)535-538(1996) 
UDC 547.953:547.963.4 
JSCS-2261 
Original scientific paper

COVALENT GLYCOPHOSPHOLIPID BINDING TO HEMOGLOBIN. A NEW POST-TRANSLATIONAL MODIFICATION OCCURRING IN ERYTHROCYTES EXPOSED TO INSULIN

VESNA NIKETIC*, NENAD TOMASEVIC*, VLATKA VAJS** and ZANKA BOJIC*

*Department of Chemistry, University of Belgrade, Studentski trg 16, P.O. Box 158, YU-11001 Belgrade, and 
**Center for Chemistry, ICTM, Belgrade, Yugoslavia

(Received, 7 August 1995)
In this work a novel hitherto unrecognised hemoglobin (Hb) fraction, HbA1x, which we detected previously in hemolysates of erythrocytes exposed to high concentration of insulin under hypoglycemic conditions, both in vivo and in vitro, was analysed. Both  chains of Hb in HbA1x were found to be modified by covalent binding of a substance containing sugar, phosphate and fatty acid residues. HbA1x was therefore termed glycophospholipid (GPL) adduct (Hb-GPL). To our knowledge, this is the first demonstration of such modification of Hb, as well as the first demonstration of post-translational GPL binding to proteins in response to insulin binding to a cell. The mechanism proposed for Hb-GPL formation is briefly described.

Key words: hemoglobin, glycophospholipid, insulin

J. Serb. Chem. Soc. 61 (7)539-543(1996) 
UDC 539.143.3:547.538 
JSCS-2262 
Original scientific paper

THE DEPENDENCE OF THE TOTAL P-ELECTRON ENERGY OF ISOMETRIC UNBRANCHED CATACONDENSED BENZENOID HYDROCARBONS WITH A FIXED NUMBER OF BAY REGIONS ON THE NUMBER OF KEKULÉ STRUCTURES

SVETLANA MARKOVIC, IVAN GUTMAN and JELENA SUKOVIC

Faculty of Scince, University of Kragujevac, P.O. Box 60, YU-34000 Kragujevac, Yugoslavia

(Received 11 December 1995)
The dependence of the total -electron energy of large unbranched catacondensed benzenoid hydrocarbons on the number of Kekulé structures is examined in families of isomers possessing a fixed number of bay regions (b). For small values of b this dependence is found to be curvilinear, whereas for larger values of b the dependence is essentially linear. These findings are in harmony with, and provide a further extension of, the results of previous studies in which the effect of bay regions was not taken into account.

Key words: total p-electron energy, number of Kekulé structures, number of bay regions

J. Serb. Chem. Soc. 61(7)545-549(1995) 
UDC 547.963.3:543.51:537.533.1 
JSCS-2263 
Original scientific paper

SOME ASPECTS OF THE QUANTITATIVE ANALYSIS OF CYCLIC NUCLEOTIDES BY FAST-ATOM BOMBARDMENT MASS SPECTROMETRY

ALEKSANDRA A. PERIC*, MILA D. LAUSEVIC*, RUSSELL P. NEWTON** and GARETH A. BRENTON**

*Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, P.O.Box 494, YU-11000 Belgrade, Yugoslavia and 
**University College of Swansea, Swansea SA2 8PP, United Kingdom

(Received 27 September 1995, revised 28 January 1996)
The possibilities of the quantitative analysis of cyclic nucleotides by fast-atom bombardment are examined. Aspects such as the amount of matrix, the formation of protonated ion species and the presence of more than one cyclic nucleotide in the sample are discussed and the conclusion has been reached that these aspects are in direct relation with the quantification of the data obtained from the mass spectra. Consideration of these aspects suggests that fast-atom bombardment does not seem to be a convenient ionisation technique for the quantitative analysis of cyclic nucleotides.

Key words: cyclic nucleotides, mass spectrometry, fast-atom bombardment

J. Serb. Chem. Soc. 61(7)551-556(1996) 
UDC 547.771:661.78 
JSCS-2264 
Original scientific paper

METAL COMPLEXES WITH PYRAZOLE-DERIVED LIGANDS. 
PART 3. COBALT(II) COMPLEXES WITH 3(5)-AMINO-4-ACETYL-5(3)-METHYLPYRAZOLE

VUKADIN M. LEOVAC*, ERIKA Z. IVEGES*, VALERIJA I. CESLJEVIC*, ANA F. PETROVIC**, DRAGOSLAV M. PETROVIC** and DEJAN POLETI***

*Institute of Chemistry, Faculty of Science, Trg D. Obradovica 3, YU-21000 Novi Sad, Yugoslavia, 
**Institute of Physics, Faculty of Science, Trg D. Obradovica 4, YU-21000 Novi Sad, Yugoslavia, 
***Department of General and Inorganic Chemistry, Faculty of Technology and Metallurgy, P. O. Box 494, YU-11001 Belgrade, Yugoslavia

(Received 6 October 1995)
Several tetrahedral cobalt(II) complexes with 3(5)-amino-4-acetyl-5(3)-methylpyrazole (HL) of the general formula [CoX2(HL)2] (X = Cl, Br, I, NCO, NCS), as well as the octahedral [Co(H2O)4(HL)2] (NO3)2 and [Co{m-N(CN)}2)2(HL)2] complexes were synthesized and characterized by elemental analysis, molar conductivity, magnetic susceptibility measurements. IR, reflectance and absorption electronic spectra.

Key words: cobalt(II)-complexes, 3(5)-amino-4-acetyl-5(3)-methylpyrazole, physico-chemical characterization

J. Serb. Chem. Soc. 61(7)557-565(1996) 
UDC 547.261:541.138:66.094.3 
JSCS-2265 
Original scientific paper

STRUCTURAL EFFECTS IN ELECTROCATALYSIS: OXIDATION OF METHANOL ON SINGLE CRYSTAL PLATINUM ELECTRODES IN ALKALINE SOLUTION

A.V. TRIPKOVIC and K.Dj. POPOVIC

Institute of Electrochemistry, ICTM, University of Belgrade 
P.O.Box 815,YU-11001 Belgrade, Yugoslavia

(Received 3 November 1995, revised 13 March 1996)
The effect of structure on the oxidation of methanol has been studied by investigating the reaction on three platinum low index planes, and ten stepped surfaces from all three zones of the stereographic triangle in 0.1 M NaOH. A pronounced structural dependence of the reaction has been shown. The most active plane from the low index surfaces was the (100). The highest current peak was obtained on the (111) plane but at a more positive potential then on the (100) plane. The most active of the stepped surfaces appeared to be the (322). The activity of the stepped surfaces was influenced by the step orientation and the step density. The origin of the surface activity was associated with the presence of OH species and the degree of OH coverage on the low index planes and on the different sites (terraces and steps) on the stepped surfaces.

Key words: methanol oxidation; structural effects; single crystal platinum electrodes; alkaline solution.

J. Serb. Chem. Soc. 61(7)567-575(1996) 
UDC 543.251:546.11' 74'' 98''' 
JSCS-2226 
Original scientific paper

VOLTAMMETRIC STUDIES OF ELECTRODEPOSITED HYDROGEN AT ELECTROCHEMICALLY DEPOSITED PD-NI-ELECTRODES

LJ. VRACAR* and M. STOJANOVIC**

* Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, 
P.O. Box 494, YU-11001 Belgrade and 
**Military-Technical Institute, Kataniceva 15, YU-11000 Belegrade, Yugoslavia

(Received 10 November 1995, revised 12 March 1996)
Potentiodynamic studies of H accommodation at a Pd-Ni electrodeposited alloy show that the hydrogen deposition-absorption or H oxidation processes can be distinguished from possible spontaneous oxidation, over somewhat overlapping potential regions. Some process which involves diffusion is indicated in experiments at various sweep rates where a linearity between jp,a and 1/2 is observed. It is suggested that this process can be diffusion of absorbed H into the electrode surface. Electrocatalytic behaviour of this alloy for any process occuring in the "hydrogen region" of potential must take into account the changed surface properties due to the presence of sorbed H.

Key words: Pd-Ni alloy, hydrogen adsorption, hydrogen absorption, hydrogen evolution, cyclic voltammetry

J. Serb. Chem. Soc. 61(7)577-582(1996 
UDC 546.59:548.51/.55 
JSCS-2267 
Original scientific paper

THE INITIAL STAGES OF THE NUCLEATION AND GROWTH OF AU ON AU(111) OBSERVED BY STM

SVETLANA STRBAC* and ZLATKO RAKOCEVIC**

*Institute of Electrochemistry, ICTM, P.O.Box 815, YU-11001 Belgrade and 
**Vinca Inastitute of Nuclear Sciences, P.O.Box 522, YU-11001 Belgrade, Yugoslavia

(Received 13 December 1995)
Tne initial stages of the nucleation and growth of Au on the Au(111) single crystal substrate have been observed by scanning tunneling microscopy (STM) in air with the surface coverage by deposited gold atoms ranging from 0.006 monolayer (ML) to 0.04 ML. The creation of two types of clusters was observed. The first type were two-dimensional (2D)-3SQRT3 clusters with vacancies in various positions having mainly seven atoms and tending to a hexagonal structure. We suppose that such clusters nucleate at point defects of flat terraces. With an increase in coverage these clusters grew up into (2D) terraces with the arrangement of gold atoms consistent with the symmetry of the (111) plane of the substrate indicating that growth occurs in a layer-by-layer mode. The second type of clusters were lined clusters whose creation begins at step edges. In the initial stages, they nucleate as 1D clusters. Their further growth is characterized by the formation of quazi-hexagonal strings. The coalescence of those strings leads to the growth of the second layer before the first one is completely filled in.

Key words: nucleation, gold, single crystal, scanning tunneling microscopy

J. Serb. Chem. Soc. 61(7)583-590(1996) 
UDC 41.134.4:41.138:621.316:541.135.6/.61 
JSCS-2268 
Original scientific paper

THE CURRENT DISTRIBUTION IN AN ELECTROCHEMICAL CELL. 
PART II. QUALITATIVE CONSIDERATIONS ON THE BASIS OF POLARIZATION CURVE SHAPE

KONSTANTIN I. POPOV, STRAHINJA K. ZECEVIC and SLAVISA M. PESIC

Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, 
P.O.Box 494, YU-11001 Belgrade, Yugoslavia

(Received 14 November 1995, revised 11 March 1996)
The current density-cell voltage curves of the system (-)Cu/CuSO4, H2SO4, H2O/Cu(+) were recorded in cell with a parallel plate electrodes for different parameters such as inter-electrode distance, distance between the edges of the electrodes and the side walls of the cell, CuSO4 and H2SO4 concentrations, temperature and the agitation of the electrolyte. The current distribution is qualitatively discussed on the basis of polarization curve shape and current line propagation depth outsides the space between the eleectrodes.

Key words: metal deposition, electrochemical cell, current distribution

J. Serb. Chem. Soc. 61(7)591-600(1996) 
UDC 678.674/.743:691.7:620.193 
JSCS-2269 
Original scientific paper

CORROSION BEHAVIOUR OF POLYESTER AND FLUOROPOLYMER COATINGS ON 
COIL COATED STAINLESS STEEL

V. B. MISKOVIC-STANKOVIC*, F. DEFLORIAN**, P. L. BONORA** and L. FEDRIZZI**

*Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, P.O.Box 494, YU-11001 Belgrade, Yugoslavia and 
**Material Engineering Department, University of Trento, Trento, Italy

(Received 12 December 1995)
Coil coated stainless steel is a new material for applications in civil and industrial fields with the purpose of reducing maintenance costs and increasing the service life of the products. The corrosion behaviour of different types of stainless steel coated with both polyester and fluoropolymer films of different thickness has been studied by means of AC impedance spectroscopy (EIS), the break-point frequency method and scanning electron microscopy analysis (SEM). The charge-transfer resistance and double-layer capacitance for both polyester and fluoropolymer coatings on stainless steel reveal no reactivity, corrosion or disbonding on the substrate. The changes of pore resistance, coating capacitance and break-point frequency over time indicate the different corrosion behaviour of polyester and fluoropolymer coatings due to their different chemical structure and film thickness. On the other hand, the polyester coatings on phosphatized galvanized steel exhibit quite different behaviour in regard to the same coatings on stainless steel. Different types of stainless steel as substrate cause the different corrosion behaviour of the investigated polyester and fluoropolymer coatings. It has been observed that stainless steel which contains more nickel and molybdenum shows higher resistance to corrosion attack in chloride environments.

Key words: corrosion, electrochemical impedance spectroscopy, protective properties, polyester coatings, fluoropolymer coatings.

J. Serb. Chem. Soc. 61(7)601-607(1996 
UDC 576.45:535.37:620.193 
JSCS-2270 
Original scientific paper

THE LUMINESCENT METHOD OF DETERMINING BERYLLIUM IN ENVIRONMENTAL SPECIMENS

L. E. ZELTSER*, M. B. BASTIC**, XILOLA Y. USMALOVA* and LJ. V. BASTIC***

*Tachkent State University, Department of Chemistry, 700095 Tashkent, Uzbekistan 
**Faculty of Technology and Metallurgy, University of Belgrade, YU-11000 Belgrade, Yugoslavia and 
***Yugoslav Institute of Meat Hygiene and Technology, YU-11000 Belgrade, Yugoslavia

(Received 17 July 1995, revised 27 February 1996)
The paper deals with a study of the formation of a complex of a new liminescence reagent, calconcarbonic acid, with beryllium and the development of a liminescent method for the determination of Be in environmental specimens in the usual way or by applying an immobilized reagent, which indicates the positive influence of immobilization on the analytical parameters of the Be determination method. The developed methods allow the determination of 2.0-8.0 ng Be with a detection limit of 0.7 ng.

Key words: luminescence, beryllium ion determination.

J. Serb. Chem. Soc. 61(7)609-614(1996) 
UCC 669.292.5:621.7.016.2 
JSCS-2271 
Original scientific paper

APPARENT ENERGY OF ACTIVATION FOR HOT WORKING OF VANADIUM MICROALLOYED STEEL

DJORDJE DROBNJAK*, ANKICA KOPRIVICA**, NENAD RADOVIC* and MILOJICA ANDJELIC**

*Department of Physical Metallurgy, Faculty of Technology and Metallurgy, University of Belgrade, P.O.Box 494, YU-11001 Belgrade, Yugoslavia and 
**Institue for Ferrous Metallurgy, YU-43400 Niksic, Yugoslavia

(Received 24 October 1995)
Two-stage linear ln [sinh(as)] vs.1/T plots, based on isothermal continuous and anisothermal multipass torsion curves, indicate the double QHW behaviour of a V-steel. Above Tnr, QHW is independent of all variables but strain. Below Tnr (which is interpass time dependent), i.e., in a temperature range in which interpass recrystallization is supressed, QHW is not only increased but that based on multipass curves also interpass time dependent, and only valid for multipass working operations.

Key words: microalloyed steel, hot working, energy of activation, simulation torsion test, recrystallization and precipitation interaction.