Terahertz spectroscopic characterizations and DFT calculations of indomethacin cocrystals with nicotinamide and saccharin.

Co-crystallization is an effective strategy to improve the drug properties such as solubility and stability. However, its thermodynamic backgrounds, especially lattice vibration, haven't been fully understood. In this work, indomethacin (IND) cocrystals formed with nicotinamide (NIC) and saccharin (SAC) are successfully characterized by using terahertz spectroscopy. DFT calculations at PBE-D3 level with and without constrained unit cell are performed to predict the absorption peaks at spectral range. The results suggest that the DFT calculations with constrained unit cell achieve a better agreement with experimental observations. Based on the optimized geometries and calculated phonons, the thermodynamic contributions from lattice vibrations to cocrystal formations are further evaluated. The findings reveal that the vibrational energy plays a comparable role with electronic energy, but has an opposite impact on these two cocrystal formations.

[Effect of lactic acid bacteria isolated from Tibetan Plateau on silage fermentation quality of Elms nutans].

OBJECTIVE: In order to detect the effect of lactic acid bacteria isolated from Tibetan Plateau on silage fermentation quality of Elms nutans. METHODS: We used 3 isolated lactic acid bacteria with better growth at low temperatures of 10 and 15 degrees C at ensiling of Elymus nutans. Subsequently, effects of the selected lactic acid bacteria on fermentation profiles of Elymus nutans silages stored at 15 and 25 degrees C were evaluated by using the same species of commercial inoculants as the control. RESULTS: PP-6 isolated from Tibetan Plateau could ferment raffinose, lactose, sorbitol, melibiose and sucrose, and LS-5 could ferment cottonseed sugar, laetrile, rhamnose, lactose, sorbitol, xylose, arabinose, melibiose and sucrose, but the same species of commercial strains could not use these sugars. Inoculation of these three strains into Elymus nutans at 15 and 25 degrees C ensiled for 50 d, we found that LS-5 significantly reduced silage pH, propionic acid concentration and ratio of ammonia nitrogen/total nitrogen at 15 degrees C (P < 0.05), salvaged more water-soluble carbohydrate and crude protein; Application of LP-2 and PP-6 as a combined inoculant to Elymus nutans significantly improved lactic acid concentration (P < 0.05), resulting in a lower ratio of ammonia nitrogen/total nitrogen, saved more crude protein and significantly reduced neutral detergent fiber content (P < 0.05) as compared with the commercial strains. CONCLUSION: The three isolated strains can improve silage quality of Elymus nutans growing on the Qinghai-Tibetan Plateau at low temperature, but these strains have no obvious advantages at 25 degrees C in comparison with the commercial inoculants.