The secondary structure of amides of adenylic acid containing D- and L-aromatic amino acids

Adenylyl-(5'leads to N)-amino acids containing as amino components, methyl esters of D-, L- and DL-phenylalanine, D-, L- and DL-tyrosine, and D-, L- and DL-tryptophan have been investigated by proton magnetic resonance (PMR) spectroscopy and circular dichroism (CD). The temperature and pD dependences of proton chemical shifts of these compounds have been studied. These data, together with the magnitudes of the upfield chemical shifts of the PMR signals of adenine and aromatic amino acids residues in adenylyl-(5'leads to N)-amino acids, have enabled us to construct conformational models of these compounds. The proposed conformation has been substantiated by the CD results. It is shown that in adenylyl-(5'leads to N)-amino acids the planes of adenine and amino acid aromatic moieties are roughly parallel. The aromatic rings of phenylalanine and tyrosine are localized approximately above the centre of adenine. In adenylyl-(5'leads to N)-D, -(L)-tryptophan, the six-membered rings of the indole overlaps the five-membraned ring of adenine indole partially overlaps the six-membered ring of adenine. A difference in the non-covalent interactions of D- and L-amino acids with nucleotides has been revealed. The mutual localization of the aromatic systems of AMP and the amino acids and also the positions of -OCH3 group with respect to the centre of the amino acid aromatic moiety differs in the series of the studied nucleotide derivatives of D- and L-amino acids.     

Experimental model investigations of sliding stability of a narrow-profile concrete dam

Conclusions Model tests for the carrying capacity of a structure on monolithic and block-system foundations show that in the cases investigated the stability factors K for a monolithic foundation are no greater than for a block-system foundation. Therefore, one can expect that stability safety factors determined for a structure whose foundation can be represented as some monolithic body, are characteristic of, as it were, the lowest level at which the carrying capacity of the structure is fully exhausted. Using this concept one can establish a design model of the system comprising the dam and a homogeneous foundation which, as a first approximation, can be applied to actual textures of rock masses in determining the stability of the structure. The investigations of the failure phase enabled an overall evaluation to be made of the carrying capacity of a narrow-profile concrete dam for the Kurpsa hydroelectric development, in comparison with the other alternatives investigated. The results obtained indicate that upon being overloaded by horizontal forces, the new design in the limiting state possesses a sufficient reserve of stability against sliding. It is essential to note that the values of the safety factors of the new dam design (model No. 3) and of the dam with a downstream slope of 1:0.7 (model No. 2) are practically identical (see Table 1). Even with sharply reduced strength properties in the contact joint (R_j≌0.2R_dam) the lowest K value obtained in tests on both models was 1.3. This indicates that the new dam design possesses a definite reliability and has sufficient reserves of strength and stability. One can conclude that from the viewpoint of static conditions the narrow-profile alternative for a concrete dam (model No. 3) should be regarded as a design which, in regard to its efficiency, is equivalent to a dam with a traditional profile (model No. 2). Thus, the series of experimental investigations carried out verifies the possibility of using in hydraulic engineering practice economical designs of conrete gravity dams of the narrow-profile alternative for the Kurpsa concrete dam (with membrane, upstream apron, etc.). Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 12, pp. 36–40, December, 1976.