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
IVANA A. JANKOVIC and LJUBICA R. JOSIMOVIC
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
SUZANA DIMITRIJEVIC-BRANKOVIC and JOSIP BARAS
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 63é.34él
JSCS – 2888
Note
N O T E
Stabilization
of Tc-99m radiopharmaceuticals by chemical additives
JURIJ VUCINA and NADEZDA VUKICEVIC
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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J.Serb.Shem.Soc.66(9)597–603(2001)
UDC 66086.2:5é3é3.7
JSCS – 2889
Original scientific paper
Tetranuclear Cu(II) complex with
octaazamacrocycle and bridging bicyclic dicarboxylato ligands
ZORAN M. MIODRAGOVIC, GORDANA VUCKOVIC and VUKADIN M. LEOVAC*
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 669.18é
JSCS – 2890
Original scientific
paper
Choosing the exponent in the
definition of the connectivity index
IVAN GUTMAN and MIRKO LEPOVIC
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 66é.8é
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
MARIJA KRMAR and MILJENKO PERIC
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 543.2é 516.822/. 8é4
JSCS – 2892
Original scientific paper
New indicator reaction for kinetic
determination of micro amounts of Sn(II)
RANGEL P. IGOV, VIOLETA D. MITIC, TODOR G. PECEV and VESNA P.
STANKOV-JOVANOVIC
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
ALEKSANDAR LOLIC, SNEZANA NIKOLIC-MANDIC and PREDRAG POLIC
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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Copyright & copy; SHD 2001.
Last
Updated Seprember 20, 2001.
For
more information contact: SHD@elab.tmf.bg.ac.yu