Relative partial molar enthalpies and apparent molar volumes of dipeptides in aqueous solution

Enthalpies of dilution at 25°C of aqueous solutions of the dipeptides glycylglycine, glycylalanine and alanylalanine have been determined and used to calculate the partial molar enthalpies of the solvent water in the solutions. The partial molar volumes of these dipeptides are also reported. The results are discussed in terms of the likely solute-solvent interactions.     

Zur Geometrie der totalen Differential-gleichungen

Ohne ZusammenfassungDiese Arbeit wurde der Redaktion im Okt. 1924 eingereicht.     

Über die „induzierte“ Löslichkeit von Ferrihydroxyd und einigen anderen Hydroxyden in Alkalilaugen in Gegenwart von Chromihydroxyd. I

Ohne Zusammenfassung     

Über das Pinakon aus Äthylphenylketon

Ohne ZusammenfassungZum Schlusse sei es mir gestattet, meinen hochverehrten Lehrern, Herrn Hofrat Prof. Dr. Ad. Lieben und Herrn Prof. Dr. C. Pomeranz, für ihre fördernde Liebenswürdigkeit und für die wertvollen Ratschläge, die sie mir während meiner Arbeit in reichem Maße zu teil werden ließen, innigsten Dank zu sagen.     

Volumetric Properties of the Nucleoside Thymidine in Aqueous Solution at T = 298.15 K and p = (10 to 100) MPa

Sound speeds have been measured for aqueous solutions of the nucleoside thymidine at T = 298.15 K and at the pressures p = (10, 20, 40, 60, 80, and 100) MPa. The partial molar volumes at infinite dilution, $ V_{2}^{\text{o}} $ , the partial molar isentropic compressions at infinite dilution, $ K_{S,2}^{\text{o}} $ , and the partial molar isothermal compressions at infinite dilution, $ K_{T,2}^{\text{o}} $ $ \{ K_{T,2}^{\text{o}} = - (\partial V_{2}^{\text{o}} /\partial p)_{T} \} $ , have been derived from the sound speeds at elevated pressures using methods described in our previous work. The $ V_{2}^{\text{o}} $ and $ K_{T,2}^{\text{o}} $ results were rationalized in terms of the likely interactions between thymidine and the aqueous solvent. The $ V_{2}^{\text{o}} $ results were also compared with those calculated using the revised Helgeson–Kirkham–Flowers (HKF) equation of state.     

The Partial Molar Heat Capacities and Expansions of Inosine, 2′-Deoxyinosine and 2′-Deoxyguanosine in Aqueous Solution at 298.15 K

Solution densities over the temperature range 288.15 to 313.15 K have been measured for aqueous solutions of the nucleosides inosine, 2′-deoxyinosine, and 2′-deoxyguanosine, from which the partial molar volumes of the solutes at infinite dilution, V ₂^o, were obtained. The partial molar expansions for the nucleosides at infinite dilution and 298.15 K, E ₂^o {E ₂^o=(∂ V ₂^o/∂ T) _p }, were derived from the V ₂^o results. The V ₂^o values at 298.15 K for the two sugars D-ribose and 2-deoxyribose also have been determined. The partial molar heat capacities at infinite dilution for all the solutes, C _p,2^o, have been determined at 298.15 K. These V ₂^o,E ₂^o, and C _p,2^o results are critically compared with all of the results available from the literature, and the use of group additivity to evaluate these solution thermodynamic properties for the sparingly soluble nucleoside guanosine is explored.     

Effects of mass difference on pressure-dependent emission characteristics in laser-induced plasma spectroscopy

A comprehensive experimental study was performed to demonstrate the effects of ambient air pressure on the emission characteristics of analyte elements in a variety of host materials in laser-induced plasma spectroscopy in low ambient air pressures. It was shown that the pressure-dependent characteristics of the emission lines are generally influenced by host elements when significant mass difference exists between the analyte and the host elements. Further investigation on the time profiles of the spatially integrated emission intensities reveal the important interplay among the dynamical factors associated with the mass-difference effect, which effectively influence the shock wave excitation process and hence the related emission intensities. The result of this study also indicates the need of proper control of time delay for the detection of maximum emission intensity in the cases considered. PACS 50.52     

The partial molar heat capacity, expansion, isentropic, and isothermal compressions of thymidine in aqueous solution at T = 298.15 K

Solution densities have been determined for aqueous solutions of thymidine at T = (288.15, 298.15, 303.15, and 313.15) K. The partial molar volumes at infinite dilution, , obtained from the density data were used to derive the partial molar isobaric expansion at infinite dilution for thymidine at T = 298.15 K, . The partial molar heat capacity at infinite dilution for thymidine, , at T = 298.15 K has also been determined. Sound speeds have been measured for aqueous solutions of thymidine at T = 298.15 K. The partial molar isentropic compression at infinite dilution, , and the partial molar isothermal compression at infinite dilution, , have been derived from the sound speed data. The , , , and results for thymidine are critically compared with those available from the literature.     

Enzymatic Degradation of Poly(ethylene terephthalate): Rapid Hydrolyse using a Hydrolase from T. fusca

Summary: It is demonstrated that PET, which is usually regarded as ‘non‐biodegradable’, can effectively be depolymerized by a hydrolase from the actinomycete Thermobifida fusca. Erosion rates of 8 to 17 µm per week were obtained upon incubation at 55 °C. Lipases from Pseudomonas sp. and Candida antarctica did not degrade PET under comparable conditions. The influences of crystallinity, melting point, and glass transition temperature on the enzymatic attack on PET, PBT, and PHB are discussed.

Outline of the degradation of PET.     

Thermodynamic properties of peptide solutions 4. Partial molar volumes and heat capacities of aqueous solutions of some glycyl dipeptides

Partial molar volumes, V ₂ ^o and partial molar heat capacities C _p,2 ^o have been determined in aqueous solution at 25°C for the dipeptides glycyl-L-asparagine, glycyl-DL-threonine, glycyl-DL-serine and glycyl-DL-phenylalanine. These results, along with those for some other dipeptides of sequence Gly-X, were used to estimate side chain contributions to V ₂ ^o and C _p,2 ^o . For these dipeptides both V ₂ ^o and C _p,2 ^o were found to be a linear function of the respective thermodynamic property for the amino acid X. The contributions of the glycyl units to V ₂ ^o and C _p,2 ^o of the dipeptide are discussed.