Anhydrous

About: Anhydrous is a research topic. Over the lifetime, 17632 publications have been published within this topic receiving 163495 citations.

On Protein Denaturation in Aqueous−Organic Mixtures but Not in Pure Organic Solvents

Abstract: FTIR spectroscopy was used to quantitatively assess the secondary structure of proteins in aqueous−organic mixtures ranging from pure water to a pure solvent. For every such solution/suspension, the α-helix content of the protein was independently calculated from the amide I and amide III spectral regions (which gave essentially identical results). In all cases studied (two unrelated enzymic proteinslysozyme and subtilisin; three dissimilar water-miscible solventsacetonitrile, tetrahydrofuran, and 1-propanol), the protein secondary structure was much more native-like in pure organic solvents than in most water−solvent mixtures, e.g., 60% (v/v) organic solvents. In fact, placing lyophilized (or crystalline) proteins in the anhydrous solvents tested had no appreciable effect on the α-helix content, whereas the latter declined markedly in the 60% (v/v) solvents. This behavior was found to be kinetically controlled, i.e., to be due to inherent restrictions on protein conformational mobility in anhydrous, in c...

Crystalline zeolite ZSM-23 and synthesis thereof

Abstract: A new crystalline zeolite, designated ZSM-23, a method of making same and the use thereof in catalytic conversion of organic compounds is the subject of this application. The new zeolite has a composition, in the anhydrous state, expressed in terms of mole ratios of oxides, as follows; (0.58-3.4)M.sub.2/n O : Al.sub.2 O.sub.3 : (40-250)SiO.sub.2 wherein M is at least one cation having a valence n, and is characterized by a specified X-ray powder diffraction pattern.

Use of Anhydrous Hydrogen Fluoride in Peptide Synthesis. I. Behavior of Various Protective Groups in Anhydrous Hydrogen Fluoride

Abstract: The properties of anhydrous hydrogen fluoride (HF) as a reagent for the acidolysis of various protective groups have been studied. Amino acids with various protective groups were each treated with HF at 0 or 20°C in the presence of anisole, and the reaction products were tested. Thus, HF was found to be much better than the other known reagents, such as hydrogen bromide and trifluoroacetic acid. In the present study, the following groups were shown, for the first time, to be removed safely: the nitro group in nitroarginine, the diphenylmethyl group in diphenylmethylamide, the t-butyl group in S-t-butylcysteine, the isopropyloxycarbonyl group, and the isopropyl ester group. A new and convenient apparatus was designed for the safe handling of HF for peptide synthesis.

Crystallization and phase stability of CaSO4 and CaSO4- based salts

Abstract: Calcium sulfate occurs in nature in form of three different minerals distinguished by the degree of hydration: gypsum (CaSO4·2H2O), hemihydrate (CaSO4·0.5H2O) and anhydrite (CaSO4). On the one hand the conversion of these phases into each other takes place in nature and on the other hand it represents the basis of gypsum-based building materials. The present paper reviews available phase diagram and crystallization kinetics information on the formation of calcium sulfate phases, including CaSO4-based double salts and solid solutions. Uncertainties in the solubility diagram CaSO4–H2O due to slow crystallization kinetics particularly of anhydrite cause uncertainties in the stable branch of crystallization. Despite several attempts to fix the transition temperatures of gypsum–anhydrite and gypsum–hemihydrate by especially designed experiments or thermodynamic data analysis, they still vary within a range from 42–60°C and 80–110°C. Electrolyte solutions decrease the transition temperatures in dependence on water activity. Dry or wet dehydration of gypsum yields hemihydrates (α-, β-) with different thermal and re-hydration behaviour, the reason of which is still unclear. However, crystal morphology has a strong influence. Gypsum forms solid solutions by incorporating the ions HPO4 2−, HAsO4 2−, SeO4 2−, CrO4 2−, as well as ion combinations Na+(H2PO4)− and Ln3+(PO4)3−. The channel structure of calcium sulfate hemihydrate allows for more flexible ion substitutions. Its ion substituted phases and certain double salts of calcium sulfate seem to play an important role as intermediates in the conversion kinetics of gypsum into anhydrite or other anhydrous double salts in aqueous solutions. The same is true for the opposite process of anhydrite hydration to gypsum. Knowledge about stability ranges (temperature, composition) of double salts with alkaline and alkaline earth sulfates (esp. Na2SO4, K2SO4, MgSO4, SrSO4) under anhydrous and aqueous conditions is still very incomplete, despite some progress made for the systems Na2SO4–CaSO4 and K2SO4–CaSO4–H2O.

Melting of Refractory Mantle at 1·5, 2 and 2·5 GPa under Anhydrous and H2O-undersaturated Conditions: Implications for the Petrogenesis of High-Ca Boninites and the Influence of Subduction Components on Mantle Melting

Abstract: GPa and in the presence of 2‐3 wt % H2O. The eVect of 2‐3 wt % dissolved H2O produces a liquidus depression in primary olivine liquidus depression (∞ C) = 74·403 · (H2 Ow t %) 0 · 352 . boninite of >112 ‐ 19∞C at a given temperature. The H2O- The equation that describes this empirical relationship is non-linear bearing melts, recalculated to 100 wt % anhydrous, are >2‐6 with an error of >9 relative percent. wt % higher in MgO, >1‐2 wt % higher in SiO2 and >1‐1·5 wt % lower in FeO, compared with nominally anhydrous melts at the same P and T. These diVerences are consistent with a change in the melting reaction, resulting in a higher contribution of or- KEY WORDS: high-Ca boninites; mantle melting; H2O-undersaturated melting; olivine liquidus depression; anhydrous melting thopyroxene to the melt phase, compared with anhydrous conditions.