Site-specificity

Many phenomena ask for local, site-specific properties of a molecule such as the partial charge on a specific atom in a molecule or the hydrogen bond donor ability of a certain OH group. It would be highly desirable to have methods as simple as an additivity model to estimate such site-specific molecular properties. 

Capital and operating costs for soda ash production are extremely site specific (29,10). Key factors iaclude iafrastmcture development, freight to consumers, local energy and labor costs, and by-product saleabiUty. 1990 Hst price of bulk natural soda ash was 108/t, F.O.B. Wyoming. 

Y. Shimizu and co-workers, "Life Span Study Report 11, Part 1, Comparison of Risk Coefficients for Site-Specific Cancer MortaUty," Technical Report RERF-TR-12-87, Radiation Effect Research Foundation, Hiroshima, Japan, 1987. 

Analytical and Test Methods. Many of the procedures for technical analyses of magnesium hydroxide are readily available from the principal producers. These procedures should be carefully reviewed. Site-specific variations in procedure steps and mechanics, especially for chemical activity, can bias results and inadvertantiy disqualify an otherwise acceptable product. 

HammerheadRtbozyme. A small RNA molecule that catalyzes cleavage of the phosphodiester backbone of RNA is known as the hammerhead ribozyme. This ribozyme occurs namrally in certain vimses where it facihtates a site-specific self-cleavage at the phosphate and generates a 2 3 -cychc phosphate and a 5 -hydroxyl terminus. The reaction requires a divalent metal ion, such as or, as a cofactor. Whereas the 

Sellers H 1991 On modeling chemisorption processes with metal cluster systems. II. Model atomic potentials and site specificity of N atom chemisorption on Pd(111) Chem. Phys. Lett. 178 351-7 

In many chemical applications, however, it would be more interesting to know how polarizability can stabilize a charge introduced into a molecule. Thus, rather than the global molecular property, mean molecular polarizability, a local, site-specific value for polarizability is needed. 

Modified oligonucleotides can be used to cross-link DNA sequences via a reactive group tethered to an oligonucleotide. When irradiated with uv light, psoralens (31) reacts with thymine bases, and the reaction yields a cross-link if the thymine residues are adjacent to each other on opposite strands. Psoralen linked to oligonucleotides have been shown to induce site-specific cross-links in vitro (51). 

It IS convenient to distinguish between enantiomeis by prefixing the sign of iota tion to the name of the substance Foi example we lefei to one of the enantiomeis of 2 butanol as (+) 2 butanol and the othei as (—) 2 butanol Optically pure (+) 2 butanol has a specific rotation ol of +13 5° optically pure (—) 2 butanol has an exactly oppo site specific rotation ol of —13 5° 

Sustainable Agriculture. The third factor that will influence the future of pesticide sales is the emphasis on sustainable agriculture systems that rely on more natural pest control methods and reduced pesticide usage. These are integrated systems that requke nutrients and crop protection chemicals from on-farm natural sources and cultural methods. Many current sustainable farms are site-specific systems that may depend on the soils in a 

To date (ca 1996) many potentially usefiil sucrose derivatives have been synthesized. However, the economics and complexities of sucrochemical syntheses and the avadabiLity of cheaper substitutes have limited their acceptance hence, only a few of them are in commercial use. A change in the price and availability of petroleum feedstocks could reverse this trend. Additional impetus may come from regioselective, site-specific modifications of sucrose to produce derivatives to facilitate and improve the economics of sucrochemical syntheses. For example, the microbe yigwbacterium tumifaciens selectively oxidizes sucrose to a three-keto derivative, a precursor of alkylated sucroses for detergent use (50). Similarly, enzymes have been used for selective synthesis of specific sucrose derivatives (21). 

The unmodified and complementary oligonucleotides were also synthesized, in order to detect thermodynamic and spectroscopic differences between the double helices. Circular dichroism spectra revealed that the covalently bound anthracene does not stack in the centre of the DNA double helix. Mutagenic activity by intercalative binding of the anthracene residue is thus unlikely. Only in vitro and in vivo replication experiments with site-specifically modified 

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