Lichen Symbiosis: Search and Recognition of Partners.

The problems associated with the initial stages of the formation of the thallus of lichens, i.e., compatibility of symbiotic partners, recognition ofsymbionts, and signals required for the formation of the differentiated thallus, are discussed.

Influence of extreme ambient temperatures and anaerobic conditions on Peltigera aphthosa (L.) Willd. viability.

Lichen are symbiotic systems constituted by heterotrophic fungi (mycobionts) and photosynthetic microorganism (photobionts). These organisms can survive under extreme stress conditions. The aim of this work was to study the influence of low (-70 °C) or high (+70 °C) temperatures, temperature fluctuations from +70 °C to -70 °C, and anaerobic conditions on P.

[Method of preparing a radioactive collagen substrate from chick embryo tendons for determining the activity of collagenases of animal origin].

A method, described for obtaining of 14C-collagen from chicken embryo tendons, permitted to isolate the highly purified native substrate with high specific radioactivity applied to estimation of animal collagenases activity. The method is relatively simple, reproducible, does not require large amount of labelled amino acids; it shortens the course of protein purification.

[Quaternary structure of NAD-kinase from rabbit skeletal muscles].

The quaternary structure and some kinetic properties were studied for NAD-kinase from the rabbit skeletal muscles. The molecular weight of the 150-300-fold purified enzymic preparation was determined by separation in the Sephadex G-200 thin layer, by means of Sephadex G-200 column gel-filtration and by the method of electrophoresis in the gradient of polyacrylamide gel concentration. Some molecular forms of NAD-kinase with a molecular weight of 31000-305000 are found in the enzymic preparation and possibility to change from one form to another is shown.

[Biosynthesis and properties of collagen forming in the cartilage of chick embryos in the presence of various proline analogs].

Effect of proline analogues on biosynthesis and properties of collagen in chick embryo cartilage was studied. Azethidine-2-carboxylic acid, 3,4-dehydroproline, cis-fluoro-proline, cis-hydroxyproline and thiazolidine-4-carboxylic acid were found to inhibit the incorporation of 14C-proline into proteins by 66-89%. Introduction of proline analogues, instead of the amino acid, into the polypeptide chains of collagen caused the impairment of the enzymatic hydroxylation of the proline residues (formation of hydroxyproline).

[Spontaneous fluctuations in the activity of rabbit skeletal muscle NAD-kinase].

Spontaneous fluctuations in the time of the activity of the 280-300-fold purified NAD-kinase preparation from rabbit skeletal muscle following its dilution are described. Defrosted but undiluted enzyme preparation failed to exhibit any fluctuations in its activity.