CONTENTS & ABSTRACTS

In English. Summaries in Estonian

Proceedings of the Estonian Academy of Sciences.

Chemistry

Volume 53 No. 4 December 2004

Modulation of adenylate cyclase activity in rat striatal membranes by adenosine A_2A receptors; 153–164

Argo Vonk, Ain Uustare, and Ago Rinken

Abstract. Possibilities of characterizing adenosine A_2A receptor dependent signal transduction in rat striatal membranes by activation of adenylate cyclase were studied. By optimization of membrane preparation methods and the composition of the incubation buffer, an up to 10-fold increase in cyclic AMP (cAMP) accumulation was achieved in response to the binding of A_2A-specific agonist CGS 21680. The best response was achieved in the crude striatal homogenate in the buffer where Na⁺ and K⁺ were omitted and then the potency of CGS 21680 was characterized by EC₅₀ = 0.5 ± 0.2 mM. The presence of at least 1 mM Mg²⁺ was required to achieve the maximal specific AC activation, but at higher concentrations magnesium increased the non-specific cAMP accumulation and decreased the receptor-mediated effects. The antagonist of A_2A receptors, ZM 241385, had no effect on the basal activity of adenylate cyclase in striatal homogenate, but inhibited the CGS 21680-dependent activation with affinity that was in agreement with the binding affinity of this antagonist to A_2A receptors.

Key words: adenosine A_2A receptor, CGS 21680, ZM 241385, adenylate cyclase, rat striatum.

Purification of amine oxidase from Pisum sativum for the construction of amine biosensors; 165–173

Andero Vaarik and Toonika Rinken

Abstract. Copper-containing amine oxidase was purified from the extract of pea seedlings (Pisum sativum) for a possible application as a bioselective compound of amine biosensors. The specific activity of the purified enzyme at different purification steps was characterized with the help of a Clark-type oxygen sensor by measuring the dissolved oxygen consumption during the oxidation of amine compounds. This sensing system was characterized with a steady-state output parameter calculated on the basis of the dynamic model of biosensors. Among the studied amine compounds pea seedlings amine oxidase (PSAO) was found to have the highest catalysing activity for cadaverine. The three-step purification procedure of PSAO revealed 35-fold purification and an enzyme preparation ready for application in biosensors.

Key words: pea seedlings amine oxidase, purification, catalytic activity.

Comparative chemical composition of the essential oil of Mentha ´ piperita L. from various geographical sources; 174–181

Anne Orav, Ain Raal, and Elmar Arak

Abstract. Variations in the essential oil composition of Mentha ´ piperita L., cultivated in different European countries, were determined. The oils were obtained in yields of 0.8–3.3% from dried samples. A total of 46 components were identified, representing over 90% of the total yield of oil. The principal components in the oils of peppermint were menthone (11.2–45.6%), menthol (1.5–39.5%), isomenthone (1.3–15.5%), menthyl acetate (0.3–9.2%), piperitone (0.8–5.9%), pulegone (0.1–13.0), 1,8-cineole (0.4–6.0%), limonene (1.0–5.9%), and trans-sabinene hydrate (traces – 6.2%). The ratio between menthol and menthone varied from 0.04 to 2.8 and between 1,8-cineole and limonene from 0.3 to 5.0. Menthol was predominant (37–40%) in the oils from Greece and Hungary. Russian peppermint oil contained only 1.5% menthol, but was rich in menthone (38.2%), isomenthone (15.5%), and pulegone (13.0%). Menthone (37.9–39.5%) and menthol (31.6 – 35.8%) were found in high concentrations in Estonian peppermint oil.

Key words: Mentha ´ piperita L., Labiatae, peppermint, essential oil, menthone, menthol, menthyl acetate.

Heavy metals in roadside soils; 182–200

Maire-Liis Hääl, Helvi Hödrejärv, and Harri Rõuk

Abstract. Strong correlations were found between traffic volume and heavy metals in the roadside soil, reflecting the vehicles as sources of Fe, Zn, Pb, and Cd and partly of Cr, Ni, and Co. In winter when de-icing salt is used an increased concentration of heavy metals, especially of Fe and Zn, in soil was observed. Zinc can be used as an indicator element to demonstrate the effect of traffic pollution in spring. In summer the mobility of Zn compounds rises due to better aeration and the lowering of the pH of soil.

Key words: soil contamination, heavy metals, chlorides, traffic, studded tires, road maintenance.

Determination of lead in contaminated soils by graphite furnace atomic absorption spectrometry for environmental risk assessment; 201–209

Lilli Paama, Hannu Rönkkömäki, Pekka Parvinen, and Toivo Kuokkanen

Abstract. A simple and rapid graphite furnace atomic absorption spectrometric (GF-AAS) technique was developed for the determination of lead in soil samples taken from a skeet shooting area. The method was evaluated by measuring some of the samples by inductively coupled plasma atomic emission spectrometry. Water and nitric acid extraction were used to determine the easily soluble lead and the total lead in order to evaluate the mobility of lead in the ground. The precision (RSD) of the GF-AAS analysis ranged from 1.1% to 3.2%. The method was tested with determining the lead in the reference materials CANMETC-Cu, PACS-2, and CRM 320. The results obtained were in good agreement with the recommended values.

Key words: lead determination, contaminated soils, GF-AAS, ICP-AES, environmental risk assessment.

Instructions to authors; 210–212

Contents of volume 53; 213–214