RNA sequences having up to three consecutive internal amide linkages were
synthesized and studied using UV and NMR spectroscopy. The amide modifications
did not interfere with normal base-pairing and A-type RNA conformation. Three
consecutive amides were well tolerated in the passenger strand of siRNA and
caused little change in RNAi activity.
Amides as neutral and hydrophobic internucleoside linkages in RNA are highly interesting modifications for RNA interference. However, testing amides in siRNAs is hampered by the shortage of efficient methods to synthesize the monomeric building blocks, the nucleoside amino acid equivalents. This paper reports an efficient synthesis of protected ribonucleoside 5'-amino 3'-carboxylic acids from D-xylose in 14 steps 7% overall yield. The key features that ensure efficiency and ease of operations are chemoselective reduction of the ester and minimization of protecting group manipulation.
Leathers made from exotic skins or rare parts of animals have very good market value. The exotic leathers are usually preferred because of their patterns, naturally occurring marks and their unique structures. The objective of this study was to investigate the feasibility of tanning the ovine stomach into novelty leather and leather products. The ovine stomach was converted into an exotic leather using oil tanning methodology, with goat oil as a tanning agent. The rumen and reticulum parts of the stomach were taken through pre-tanning, tanning and post-tanning operation. The resultant leather had a different grain from the ordinary leather. Then mechanical operations like drying, toggling and staking were done. Physical properties of the leathers were analyzed by determining their thickness, tensile strength, elongation at break, tear strength, flex endurance and ball burst extension test. The grain structure of the leathers was analyzed using a light microscope. The results of physical tests were poor compared to the grains of conventional leathers since the composition of raw outer coverings of animals and those of the stomach are different. The leather processed from this non-conventional source has been found suitable for manufacturing fancy small leather goods like coin purse, key holders, purses and wallets.
The main drawback in the utilization of geothermal resources arises from the precipitation of secondary minerals within wells, pipelines, steam separators, turbines and other surface equipment in form of scales. Scale formation is an outcome of the alteration of various rocks dissolved in geothermal fluids that find their way into a reservoir. Once geothermal fluids ascend to the surface, hydrostatic pressure decreases toward a phase separation level that permits the dissolved gases such as CO 2 , H 2 S and H 2 , and steam to separate from the liquid phase by "boiling". Stripping of these volatiles may increase fluid pH, leading to precipitation and deposition of secondary minerals. The study sought to establish the relationship between water-rock interaction and secondary mineral precipitates at the surface and deep fluid at different temperatures during depressurisation boiling and cooling. Samples were collected from selected Olkaria wells; OW-38A, OW-910 and OW-910A. The analysis of the results outlined deep fluid Alkali-Chloride waters and surface steam-heated Alkali-Bicarbonate and acidic Sulphate-Chloride waters. Various models suggested adiabatic boiling, conductive cooling and possible mixing and dilution in the wells. Hydrothermal alteration minerals were found to be in equilibrium with the geothermal fluids at varying temperatures, and the secondary minerals controlled the chemistry of the reservoir. Silica-saturated solutions precipitated silica in OW-910 and OW-910A, which may have resulted from rapid cooling following mixing with cold surface water.
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