JSCS - Vol 65, No 4

JSCS Vol 65, No. 4

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J.Serb.Chem.Soc. 65 (4) 207-227 (2000)
UDK 543.866:547.158.4
JSCS-2740
Review paper

REVIEW
Structure and function of yeast alcohol dehydrogenase

SVETLANA TRIVI and VLADIMIR LESKOVAC*

Faculty of Science and *Faculty of Technology, Bulevar Cara Lazara 1, YU-21000 Novi Sad, Yugoslavia

(Received 15 June 1999, revised 17 January 2000)
1. Introduction
2. Isoenzymes of YADH
3. Substrate specificity
4. Kinetic mechanism
5. Primary structure
6. The active site
7. Mutations in the yeast enzyme
8. Chemical mechanism
9. Binding of coenzymes
10. Hydride transfer
Keywords: yeast alcohol dehydrogenase, structure and function.

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J.Serb.Chem.Soc. 65 (4) 229-244 (2000)
622.337:539.183.4:534.24
JSCS-2741
Original scientific paper

Fourier transform infrared and electron spin resonance examinations of kerogen from the Gunflint stromatolitic cherts (Middle Precambrian, Ontario, Canada) and related materials

PAVLE I. PREMOVIC, GORAN S. NIKOLIC, MIROSLAV P. PREMOVIC and IVANA R. TONSA

Laboratory for Geochemistry and Cosmochemistry, Department of Chemistry, Faculty of Science, University of Nis, P.O. Box 91, YU-18000 Nis, Yugoslavia

(Received 16 August 1999)
Kerogen occurrences in stromatolitic cherts from the Middle Precambrian Gunflint Formation and related rocks have been investigated by the use of elemental analysis, Fourier transform infrared and electron spin reconance spectroscopies. Particular attention was paid to the structural properties of the Schreiber kerogen to allow comparison with biologically controlled kerogens from Paleozoic carbonaceous rocks. The low atomic H/C ratios (0.5) of the Schreiber kerogen indicates that this material has reached a high level of maturity. The Fourier transform infrared/electron spin resonance examinations revealed that the Schreiber kerogen contains predominantly aromatic/polyaromatic structures similar to those found in mature kerogens from Paleozoic carbonaceous rocks. The evidence from this organogeochemical comparison indicates that the Schrei-ber kerogen and mature kerogens from Paleozoic/Mesozoic carbonaceous rocks have sufficient similarity to suggest a similar origin. Consequently, this work gives strong support to the hypothesis that if the Schreiber kerogen is of biotic origin than it is derived from the remnants of various microbial organisms (mainly phytoplanktons) including a minor contribution of subtidal (stromatolite-building) cyanobacteria.
Keywords: kerogen, Gunflint stromatolitic cherts, electron spin resonance. Fourier transform infrared spectroscopy.

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J.Serb.Chem.Soc. 65(4) 245-253 (2000)
UDC 547.814.5/ .973:547.973.6:543.42/ .52
JSCS-2742
Original scientific paper

A study of the IR spectra of copigments formed by malvin chloride with flavones

UBAVKA B. MIOC, JASMINA M. DIMITRIC MARKOVIC and JELISAVETA M. BARANAC

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

(Received 5 August, revised 28 December 1999)
Research into the essence of the process of copigmentation of anthocyan molecules was continued by applying IR spectroscopy, in an attempt to elucidate the formation mechanism of copigment molecules between malvin chloride and several variously substituted flavones. Analysis of the IR spectra of the formed copigments revealed that the process of copigmentation is achieved via the formation of hydrogen bonds. The strength of the formed hydrogen bonds was correlated with the equilibrium constants of the processes of copigmentation of these molecules. The found correlation was in accordance with the supposed mechanism of the copigmentation reaction.
Keywords: malvin, flavones, copigmentation, IR spectra.

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J.Serb.Chem.Soc. 65(4) 255-263 (2000)
UDC 547.565.3:543.48
JSCS-2743
Original scientific paper

An investigation of the Fe³⁺- sulphonated pyrogallol system in aqueous solutions

M. G. PJESCIC, D. S. VESELINOVIC*, V. P. KOMNENIC and I. V. DRASKOVIC

Faculty of Metallurgy and Technology, University of Montenegro, Cetinjski put bb, YU-81000 Podgorica and
* Faculty of Physical Chemistry, University of Belgrade, P.O. Box 137, YU-11001 Belgrade, Yugoslavia

(Received 3 March 1999, revised 10 January 2000)
The electrochemical behaviour of the Fe³⁺-sulphonated pyrogallol (SP) complex was investigated and its composition and stability constants were determinated at pH 2.30. It was found by voltammetric and spectrophotometric measurements that Fe³⁺ and SP form a complex of the ML₂ type, which is relatively stable during the first 30 minutes. The optimal pH value for complex formation is between 2.30 and 2.80. The relative stability constants determined by voltammetric and spectrophotometric measurements are log b₂ = 5.08±0.26 and log b₂ = 6.31±0.04, respectively.
Keywords: cyclic voltammetry, spectrophotometry, Fe³⁺ ions, complex, sulphonated pyrogallol.

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J.Serb.Chem.Soc. 65(4)265-274(2000)
UDC 549.766.21:661.834:66.049
JSCS-2744
Original scientific paper

The products of selenite hydrothermal treatment in lithium chloride solutions

SLOBODANKA MARINKOVIC, ALEKSANDRA KOSTIC-PULEK and MIRJANA DJURICIC*

Faculty of Mining and Geology, University of Belgrade, P.O. Box 162, YU-11001 Belgrade and
*Institute for Technology of Nuclear and Other Raw Materials, P.O. Box 390, YU-11001 Belgrade, Yugoslavia

(Received 9 June, revised 16 August 1999)
Selenite was boiled in LiCl solutions of different concentrations (1 M, 2 M, 3 M, 4 M and 5 M) at the respective boiling temperatures and atmospheric pressure. The products were subjected to X -ray diffraction analysis, qualitative infrared analysis, differential thermal analysis, thermogravimetric analysis and microscopic examination. The product obtained in the 1 M LiCl solution was the b-form of calcium sulphate hemihydrate (b-CaSO₄·0.5H₂O). In more concentrated LiCl solutons, 2 M and 3 M, the a-form of calcium sulphate hemihydrate (a-CaSO₄·0.5H₂O) was formed. The product obtained in the 4 M LiCl solution was also the a-form of calcium sulphate hemihydrate, only mixed with the g-form of calcium sulphate (g-CaSO₄). Finally, in the 5 M LiCl solution the g-form of calcium sulphate or g-anhydrite was formed.
Keywords: selenite, hemihidrate, hydrothermal treatment, calcium sulphate.

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J.Serb.Chem.Soc. 65(4) 275-279 (2000)
UDC 546.41:542.61:347.545/547.53/
JSCS-2745
Short communication

SHORT COMMUNICATION
Extraction of calcium from water into nitrobenzene using strontium dicarbollylcobaltate in the presence of 18-crown-6

MARCELA DANKOVA, EMANUEL MAKRLIK* and PETR VANURA**

Kremlickova 964, 280 00 Kolin II,
*341 42 Kolinec 250 and
**Department of Analytical Chemistry, Prague Institute of Chemical Technology, 166 28 Prague, Czech Republic

(Received 11 October 1999)
From extraction experiments and g-activity measurements, the extraction constant corresponding to the equilibrium Ca²⁺(aq) + SrL²⁺(nb) « CaL²⁺(nb) + Sr²⁺(aq) taking place in the two-phase water-nitrobenzene system (L = 18-crown-6, aq = aqueous phase, nb = nitrobenzene phase) was evaluated as log K_ex(Ca²⁺, SrL²⁺) = -1. 9±0.1. Furthermore, the stability constant of the calcium - 18-crown-6 complex in nitrobenzene saturated with water was calculated for the temperature of 25°C: log b_nb (CaL²⁺) = 10.1±0.1.
Keywords: water-nitrobenzene system, calcium, 18-crown-6, stability constant.

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