Structural changes of ultraviolet-irradiated DNA derived from hydrodynamic measurements

The paper reports on sedimentation and viscosity measurements performed on ultraviolet-irradiated DNA from T7 phage and calf thymus. From the hydrodynamic data the relative changes in the mean molecular weight, radius of gyration, and effective Kuhn statistical segment length were calculated. The results show that ultraviolet irradiation (254 nm) leads to a significant decrease of the effective statistical segment length of DNA which may be due to small local helix kinks (produced by the generation of photodimers) and a local increase of chain flexibility. Alterations in the overall DNA conformation may be observed even at low fluences where the mean molecular weight almost stays constant. The locally distorted helix regions possibly may serve as recognition sites in the first step of excision repair.     

Synthesis and some reactions of 3,5-di-O-methyl-d-glucose and -fructose

Hydrolysis of 1,2-O-isopropylidene-3,5-di-O-methyl-α-d-glucofuranose by strong acid yielded 3,5-di-O-methyl-d-glucofuranose (6) and its 1,6-anhydride (10). The mechanism of the reaction giving 10 is discussed. On treatment with a catalytic amount of sodium methoxide, 1,2,6-tri-O-acetyl-3,5-di-O-methyl-d-glucofuranose (8) gives the 6-O-acetyl derivative, whereas complete deacetylation, and subsequent isomerization to the d-fructose derivative 16, takes place in the presence of 0.1m sodium methoxide. The structure of 16 was proved both chemically and spectroscopically. Reduction of 6 or 8 with a borohydride afforded 3,5-di-O-methyl-d-glucitol.²     

Effect of various inhibitors on the multiplication of BLE bacteriophage inBacillus licheniformis

A total of 40 substances were tested for their inhibitory effect on the multiplication of a bacteriophage in a growing culture ofBacillus licheniformis and their influence on bacitracin production. Acriflavine was the only substance which, at a concentration of 3 μg ml^-1, completely suppressed phage multiplication while having no effect on the growth ofBacillus licheniformis and on the production of the antibiotic.     

Saprobic sequence within the genus euglena

In total 73 species of Euglena were ordered according to their saprobic index (S) and saprobic valency starting with species tolerating a heavy organic pollution and ending with those from most clean water. This paper is meant as an addition to the Ergebnisse der Limnologie, Heft 7 (Sládeek, 1973).     

Relationship between acute and chronic exposures in mutagenicity studies in mice

The relationship between acute and chronic exposures in mutagenicity studies on mammals still lacks experimental data that might permit the decision whether or not the long-term exposures are of significance in mutagenicity testing.Fractional application of TEPA, THIOTEPA, EMS cyclophosphamide and sodium arsenite was made in experiments with mice, by using the dominant-lethal test and cytogenetic analysis of bone marrow. In most experiments the repeated application yielded the same or higher genetic injury than the same total dose at a single application. Negative results are discussed in relation to the threshold dose and the different sensitivity of the germ-cell stage.Possible interaction of mutagens was also studied by analyzing the combined effect of a long-term exposure to sodium arsenite, which probably affected the repair mechanism, and of a single dose of TEPA. It is concluded that the present stage of knowledge requires acceptance of the opinion that the genetic risk induced by chronic exposure to a chemical is as serious as that induced by an acute exposure.     

The properties of oligonucleotide fragments containing the triphosphorylated 5′-termini of nuclear pre-mRNA from Ehrlich ascites carcinoma cells

Triphosphorylated 5-end fragments 50–150 nucleotides in length were isolated from nuclear pre-mRNA with the aid of a hydroxyapatite chromatography. They are enriched in U and G (28 and 26%, respectively). About 15% of the fragments isolated from poly(U)⁺RNA contain poly(U) tracks. Neither poly(A)-nor double-stranded sequences were found. Hybridization experiments in conditions of vast DNA excess demonstrated that the 5-end fragments contain a low amount of highly repetitive sequences but enriched in sequences hybridizing at C ₀ t 1/2 ~100.     

Taxonomy of primycin producing actinomycetes. I. Description of the type strain of thermomonospora galeriensis.

Strain FBUA 1274 (=strain 28/650707, Hungarian National Collection of Medical Bacteria, National Institute of Public Health, Budapest) is designated the type strain of Thermonospora galeriensis (Vályi-Nagy et al.) comb. nov., and the morphological characteristics of this strain are described.