Waveguide optogalvanic device

In the paper an optogalvanic experiment is described. A tunable dye laser irradiates discharge plasma in neon and the change of the plasma density is measured by microwave technique. The paper describes also the theoretical method which gives the change of the plasma impedance in relation to the measured signal. Finally the measuring method, the theoretical predictions for optimizing the method and the proposed approximations were experimentally checked.     

Image Projection and Representation on S<Superscript>n</Superscript>

In signal processing, communications, and other branches of information technologies, it is often desirable to map the higher-dimensional signals on Sⁿ. In this article we introduce a novel method of representing signals on Sⁿ. This approach is based on geometric function theory, in particular on the theory of quasiregular mappings. The importance of sampling is underlined, and new geometric sampling theorems for general manifolds are presented.     

Recent advances in electrochemical analysis of biomacromolecules. Catalytic hydrogen evolution and modification of glycoproteins and glycans by Os(VI) complexes

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Synthesis of Amine Derivatives of the Polyhedral Borane Anion [B(20)H(18)](4)(-)

Ethylenediamine (en) reacts with the polyhedral borane anion [n-B(20)H(18)](2)(-), in the presence or absence of strong nonnucleophilic auxiliary bases, to produce the [ae-B(20)H(17)(en)](3)(-) anion. In either case, substitution is accompanied, to an approximately equal extent, by reduction of the starting material to form [a(2)()-B(20)H(18)](4)(-). As found with similar substituted systems derived from this 20-boron structure, [ae-B(20)H(17)(en)](3)(-) may be conveniently rearranged to the [a(2)()-B(20)H(17)(en)](3)(-) anion. A more convenient synthesis of the known [ae-B(20)H(17)NH(3)](3)(-) ion, which employs acetonitrile as the source of the NH(3) ligand instead of liquid ammonia, is also described.     

Catalytic Activity of Enzymes Altered at Their Active Sites

Protein engineering has as its goals the design and construction of new peptides and proteins with novel binding and catalytic properties. In one approach to protein engineering, new active sites have been introduced into naturally occurring proteins either by site-directed mutagenesis or by chemical modification. Providing that important changes in the tertiary structures do not result from such alterations, at least a portion of the binding site of the original protein should be available for the formation of complexes between the altered enzyme and its substrates. Many examples of active-site mutations have been described, including the generation by us of a cysteine mutant of alkaline phosphatase. A fundamental limitation of the site-directed mutagenesis methodology is that replacements of residues are restricted to the twenty naturally occurring amino acids. The alternative, chemical modification, is difficult to carry out for the specific replacement of one amino acid by another. However, we have shown that through such modification coenzyme analogues can be introduced covalently into appropriate positions in proteins, allowing us to produce semisynthetic enzymes with catalytic activities radically altered from those of their precursor proteins. In another approach to protein engineering efforts have focused on the construction of systems where, as a first approximation, folding can be neglected and the preparation of secondary structural units is the target. Examples of the successful design of biologically active peptides and proteins along such lines, taken from our own work, include molecules mimicking apolipoproteins, toxins, and many hormones. In recent studies we have progressed to the stage where we are starting to combine the two general approaches to protein engineering we have described and are able to construct small enzymes like ribonuclease T₁ and its structural analogues.