Interactions des ions métalliques avec le DNA. I. Comportement de polyélectrolyte et liaison des ions compensateurs

The theory of polyelectrolyte solution of Alexandrowicz: and Katchalsky is used to calculate the electrostatic potential of single stranded polynucleotides for different ionic strength. We have considered the potential of double stranded DNA as the superposition of the different potentials produced by each chain, provided the average distance between the strands is higher than an ionic strength-dependent parameter b. For ionic strength lower than 5 × 10^?2M, the assumption is no longer valid, and a cylindrical model with a uniform charge density must be used. The continuity between the two models was tested, and thus we can calculate the electrical potential at the vicinity of a phosphate group in the whole range of ionic-strength where the double helix is stable. It was therefore possible to determine the theoretical number of ions bound electrostatically to DNA and we found an increase of ion binding with a decrease of ionic strength. Such a model was further applied to the change of specific volume in different salt solutions. Comparison is made with recent pycnometric data on Na^? and Cs^? salts of DNA. Agreement is good in the case of Cs⁺, but for Na⁺, cation binding is likely to be accompanied by a change of the hydration of DNA, which depends on ionic strength. With the same model we can see easily the ion-trapping properties of DNA which play an important role in any formation of complex between heavy ions and bases.     

Néandertal et le feu au Paléolithique moyen ancien. Tour d’horizon des traces de son utilisation dans le Nord de la France

This article aims at drawing up balance sheet of remains of fire use by the first Neanderthals of Northern France, during the second part of the Saalian (MIS 8 to 6). This overview reminds us the rarity of fire testimonies during Early Middle Palaeolithic (300–130 ky BP) on the scale of North-Western Europe. For Northern France, only the sites of Biache-Saint-Vaast and Therdonne present remains of combustion. At Biache-Saint-Vaast, it is not less than six levels, which present clues of combustion: burnt flint and faunal remains and sometimes charcoals. At Therdonne, besides burnt numerous flint and some rare faunal remains were brought to light during the excavation of level N3 several rich zones in organic residues and micro-charcoals. All the datas collected concerning the clues of combustion at Biache-Saint-Vaast and Therdonne is compiled, analyzed and interpreted. This approach permits to establish the fire use or its absence in saalian occupations of Neanderthals of Northern France and to discuss modalities of its use, particularly at Therdonne. To conclude, fire status and its implications in first Neanderthals occupations are briefly discussed.     

Bryozoaires des Peuplements Sciaphiles de Méditerranée: Révision de Cribrilina setosa Waters et Description de Deux Nouvelles Espéces de Cribrilaria (Bryozoa, Cheilostomata)

The cribrimorph bryozoan Puellina setosa (Waters) is reviewed, together with a closely related species, Puellina gattyae (Busk), and two new Cribrilaria species from the Mediterranean, C. cassidainsis sp. n. and C. minima sp. n., which present some characters in common with P. setosa and were previously confused with it.     

Evolution des activités enzymatiques dans le tractus digestif au cours de la vie larvaire de la sole. Variations des protéinogrammes et des zymogrammes

The activities of digestive enzymes were studied during the course of larval development (from hatching to 30 days) in the sole, Solea solea. No glycosidase activity was present, but alkaline proteolytic activity increased from hatching to day 5, then decreased until day 15. In the acid range, proteolytic activity was relatively stable from the 10th to the 30th day. There were also changes in the number of esterase-like isozymes which increased between day 20 and 30, with minimum activity observed during metamorphosis.