Vibrational heat capacity of silver carp collagen.

The study of the experimental and calculated heat capacity, Cp of fish collagen (silver carp) with contents of several additive components was presented. The experimental low-temperature heat capacity was measured in the temperature range of 1.85 to 302.8 K using a Quantum Design Physical Property Measurement System (PPMS) and the higher temperature Cp from 223.15 K to 382.15 K by Differential Scanning Calorimetry (DSC) method. For an interpretation of the experimental, low-temperature data, the vibrational heat capacity of the pure silver carp collagen was calculated based on the contribution of a sum of the vibrational heat capacity of 4248 amino acids. The vibrational heat capacity for each amino acids was taken from Advanced Thermal Analysis System (ATHAS) Data Bank for individual poly (amino acid) residues based on their group and skeletal vibrational spectra. Comparing of the experimental heat capacity of the collagen with additive components and the calculated vibrational heat capacity of the pure silver carp collagen shows that the differences range from around 10% at 100 K to 14% at 300 K temperature. Such thermal analysis can provide information about the contribution to Cp of unknown components or impurities in the investigated system.

Esters with imidazo [1,5-c] quinazoline-3,5-dione ring spectral characterization and quantum-mechanical modeling.

1-phenyl-2H,6H-imidazo[1,5-c]quinazoline-3,5-dione reacts with ethyl bromoacetate under mild conditions to give 2-(ethoxycarbonylmethyl)-1-phenyl-6H-imidazo[1,5-c]quinazoline-3,5-dione (MEPIQ) and next 2,6-bis(ethoxycarbonylmethyl)-1-phenylimidazo[1,5-c]quinazoline-3,5-dione (BEPIQ). The products were isolated at high yield and identified on the basis of IR, 1H- and 13C-NMR, UV spectroscopy, and X-ray crystallography. Diester (BEPIQ) can be presented by 16 possible pair of enantiomers. Only one pair of them is the most stable and crystallizes which is shown crystallographic research. Based on quantum-mechanical modeling, with the use of DFT method, which conformers of mono- and diester and why they were formed was explained. It was calculated that 99.93% of the monoester (MEPIQ) is formed at position No. 2 and one pair of the monoester conformers, from six possible, has the largest share (51.63%). These results afforded to limit the number of diester conformers to eight. Unfortunately, the quantum-mechanical calculations performed that their shares are similar. Further quantum-mechanical modeling showed that conformers are able to undergo mutual transformations. As a result only one pair of diester conformers forms crystals. These conformers have substituents in trans position and these substituents are located parallel to imidazoquinazoline ring. This allows for the denser packing of the molecules in the unit cell.