JSCS Vol 66, No. 9

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J.Serb.Chem.Soc. 66(9)571–580(2001)
UDC 66.094.732
JSCS – 2887
Original scientific paper

Autoxidation of tryptophan in aqueous solutions


Vinca Institute of Nuclear Sciences, Laboratory for Radiation Chemistry and Physics “Gamma”, P. O. Box 522, YU-11001 Belgrade, Yugoslavia
 E-mail address: ivanaj@rt270.vin.bg.ac.yu

(Received 22 February 2001)
Autoxidation of tryptophan was investigated in aqueous solutions by the gamma radiolytic technique. The oxygen uptake and formation of peroxide materials was followed as a function of pH, dose rate and concentration of tryptophan. The results obtained indicate that TrpH(OH)OO. radicals react with tryptophan by adduct formation thus propagating autoxidation. The chain propagation length (CPL) for a 2·10–2 mol dm–3 tryptophan solution at pH 9.5 and a dose rate 0.01 Gy s–1 was estimated to be ~ 5.8, which shows that the autoxidation of tryptophan is a short chain reaction.
Keywords: autoxidation, tryptophan, peroxy radicals.
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J.Serb.Chem.Soc. 66(9)581–589(2001)
UDC 582.231
JSCS – 2888
Original scientific paper

Comparative study on biochemical activity of the intestinal isolates Lactobacillus sp. V3 and Bifidobacterium sp. A71 in different substrates


Faculty of Technology and Metallurgy, Karnegijeva 4, YU-11001 Belgrade, Yugoslavia

(Received 6 March, revised 4 July 2001)
The two intestinal isolates Lactobacillus sp. V3 and Bifidobacterium sp. A71 were selected for soymilk fermentation according to their acidification activity in soymilk. Beetroot juice and carrot juice were chosen for soymilk supplementation as additional sources of carbohydrates and brewer's yeast as an extra source of nitrogen. The fermentation was carried out for eight hours at 42°C. The fermentation was monitored by standard analytical and microbiological tests for changes of acidity (decreasing pH and increasing acid content), the contents of soluble dry substances, sugars and a-amino acids as well as changes in the number of viable cells. The samples were collected at the beginning and subsequently every two hours until the end of the fermentation. The results showed that there were differences between the tested isolates in terms of their ability to ferment soymilk. The mix with brewer's yeast had a better stimulating effect on the growth of both strains compared to those with juices alone. In addition, the carrot juice stimulated the growth of Bifidobacterium sp. A71 better than beetroot juice, while the opposite effect was found for the growth of Lactobacillus sp. V3.
Keywords: Lactobacillus, Bifidobacterium, soymilk, fermentation, biochemical activity.
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J.Serb.Chem.Soc. 66(9)591–596(2001)
UDC 63ι.34ιl
JSCS – 2888

Stabilization of Tc-99m radiopharmaceuticals by chemical additives


 Laboratory for Radioisotopes, Vinca Institute of Nuclear Sciences, P. O. Box 522, YU-11001 Belgrade, Yugoslavia

(Received 3  March, revised 4 July 2001)
The reliability and applicability of the preparation of the three, for nuclear medicine very important, 99mTc-radiopharmaceuticals from the inactive (technetium-cold) kit solutions were tested. Each examined commercial kit was dissolved in saline (0.9 % NaCl). The conditions of the storage of the inactive kit solutions till labeling were examined. The main problem is the stablity of the reductant stannous ions which is very difficult to predict. To stabilize and ensure a good quality of the labeled radiopharmaceuticals, ascorbic or gentisic acid were added. It was found that the best results were obtained by keeping the samples frozen at –20 ?C. Both stabilizers can be used but for an effective protection much lower concentrations of ascorbic acid are needed. Its concentrations of 12–60 mg/ml of the kit, stabilized dimercaptosuccinate (DMS) and pyrophosphate (PyP) for about 7–8 days. The solution of 2,3-dicarboxypropane-1,1-diphosphonate (DPD) was found to be stable even without the stabilizer. This could be attributed probably to the chemical nature of this complex. However, in routine praxis the applied procedure demands great care and personel very experienced in radiopharmacy.
Keywords: Radiopharmaceuticals, technetium-99m, dimercaptosuccinate, dicarboxypropane diphosphonate, pyrophosphate.
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UDC 66086.2:5ι3ι3.7
JSCS – 2889
Original scientific paper

Tetranuclear Cu(II) complex with octaazamacrocycle and bridging bicyclic dicarboxylato ligands


Faculty of Chemistry, University of Belgrade, P.O. Box 158, YU-11001 Belgrade and
*Institute of Chemistry, Faculty of Science, Trg D. Obradovica 3, YU-21000 Novi Sad, Yugoslavia

(Received 19 March 2001)
A new tetranuclear copper(II) complex of the formula [Cu4L(tpmc)2](ClO4)6·4NaClO4 (tpmc = N,N’,N”,N’’’-tetrakis(2-pyridylmethyl)-1,4,8,11-tetraazacyclotetradecane; L = endo-bicyclo[2.2.1]-hept-5-en-2,3-cis-dicarboxylate dianion) has been isolated. The complex was characterized by elemental analysis, magnetic and conductometric measurements, electronic and IR spectroscopy and cyclic voltammetry (CV). This is one of the rare cases when a tetranuclear complex with tpmc is formed, with the bulky bicyclic dicarboxylate as the bridging ligand between two tpmc units in which two copper(II) ions are coordinated in the exo position.
Keywords: tetranuclear complex, bicyclic dicarboxylato ligand, octaazamacrocycle, copper(II).
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J.Serb.Chem.Soc. 66(9)605–611(2001)
UDC 669.18ι
JSCS – 2890
Original scientific paper

Choosing the exponent in the definition of the connectivity index


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

(Received 4 May 2001)
Let du denote the degree of the vertex u of a molecular graph G. Then the connectivity index of G is defined as C (l) = G (l; C) = S (dudu)l, where the summation goes over all pairs of adjacent vertices. The exponent l is usually chosen to be equal to –1/2, but other options were considered as well, especially l = –1. We show that whereas C(–1/2) is a suitable measure of branching of the carbon-atom skeleton of organic molecules, and thus applicable as a topological index for modeling physico-chemical properties of the respective compounds, this is not the case with C(–1). The value of l is established, beyond which C(l) fails to correctly reflect molecular branching.
Keywords: connectivity index, branching, topological index, tree, chemical tree.
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J.Serb.Chem.Soc. 66(9)613–630(2001)
UDC 66ι.8ι
JSCS – 2891
Original scientific paper
Interplay between vibronic and spin-orbit couplings in 3P states of triatomic molecules using as an example the A3Pu electronic state of NCN


Faculty of Physical Chemistry, University of Belgrade, Studentski trg 12–16, P. O. Box 137, YU 11000 Belgrade, Yugoslavia

(Received 7 May 2001)
A systematic study of various effects on the structure of the spectra of linear triatomic molecules in the 3P electronic states has been carried out. Paricular attention was paid to the interplay between the vibronic and spin-orbit couplings. Variational and perturbative computations at various levels of sophistication were performed fot the A3Pu state of the NCN radical.
Keywords: Renner-Teller effect, spin-orbit coupling, ab initio calculations, variational and perturbative approaches.
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J.Serb.Chem.Soc. 66(9)631–636(2001)
UDC 543.2ι    516.822/. 8ι4
JSCS – 2892
Original scientific paper

New indicator reaction for kinetic determination of micro amounts of Sn(II)


Department of Chemistry, Faculty of Science, University of Nis, Cirila i Metodija 2, YU-18000 Nis, Yugoslavia

(Received 2 Feburary, revised 16 April 2001)
A new reaction is suggested and a new method is elaborated for determination of micro amounts of Sn(II) based on its inhibiting effect on the oxidation of {4-bis[n-(dimethylamino) phenyl ]methylene-2,5-cyclohexadiene-1-ilydene}dimethyl-ammonium chloride (crystal violet CV) by H2O2. The method sensibility is 0.4 mg/cm3. The probable relative error is 2.8–12.8 % for Sn(II) in the concentration interval of 3 to 0.8  mg/cm3. The kinetic equation for this process is given. The influence of some other ions on the reaction rate was tested. The method was applied to the determination of Sn(II) in a sample of microalloy.
Keywords: tin, kinetic determination, crystal violet.
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J. Serb.Chem.Soc. 66(9)637–646(2001)
UDC 543.553:546.132+533.15
JSCS – 2893
Original scientific paper

Optimization and application of the gas-diffusion flow injection method for the determination of chloride


Faculty of Chemistry, University of Belgrade, Studentski trg 16, P. O. Box 158, YU-11001 Belgrade, Yugoslavia

(Received 17 July 2000, revised 2 July 2001)
A selective and sensitive procedure for the fast and indirect determination of chloride by the gas-diffusion FIA method has been optimized and applied for the determination of chloride in water samples which contained different amounts of the analyte. The examined samples were: seawater, tap water and very pure water from the water-steam system of the power plant “Nikola Tesla B” in Obrenovac. Application of an amperometric detector (model LC-17A; BAS, West Lafayette, USA) enables the detection limit to be decreased down to 0.05 mmol/dm3 of chloride, which corresponds to 35.5 pg, and adjustment of the acceptor flow rate and direction inside the gas-diffusion unit. In this way the optimized FIA system has excellent repeatability. For 5 mmol/dm3 it was found to be 1.11 % (n = 5). The throughput of this method is 60 samples per hour.
Keywords: gas-diffusion flow injection method, amperometric detection, indirect chloride determination.
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