Effects of low-frequency ultrasound on heterogenous deacetylation of chitin.

The effects of low frequency ultrasound to the heterogeneous deacetylation of chitin from the shell of white shrimp (Penaeus vannamei) were examined. The deacetylation process was carried out in the range of NaOH concentrations from 35% to 65% (w/w) with and without the ultrasound in the frequency of 37kHz, RMS=300W. The chitosan obtained was characterized in the degree of deacetylation, solubility, FT-IR and X-ray diffraction. The results showed that the behaviors of the deacetylation in two cases, with and without ultrasound, were similar but the ultrasound enhanced the deacetylation rate and therefore reduced the time of the reaction to get the same degree of deacetylation. The role of ultrasound in the process showed more clearly in the low concentration of sodium hydroxide, below 45% (w/w). At the higher concentration of sodium hydroxide, the influence of ultrasound on facilitating deacetylation decreased significantly, however, ultrasound was still keeping on its improving effect on the solubility of the chitosan obtained. The data from FT-IR and X-ray diffraction did not show any considerable change in structure of both kinds of chitosan. This study showed the potential of using low frequency ultrasound in enhancing the deacetylation of chitin for reducing the chemical consumption.

High accuracy mass spectrometry comparison of Conus bandanus and Conus marmoreus venoms from the South Central Coast of Vietnam.

Cone snail (genus Conus) venoms provide a rich source of small bioactive peptides known as conopeptides or conotoxins, which are highly interesting in pharmacological studies for new drug discovery. Conus species have evolved expressing a variety of conopeptides, adapted to the biological targets of their own specific preys at their living environments. Therefore, the potential proteomic evaluation of Conus venom components, poorly studied, is of great interest. Early studies supposed about 5% overlap in venom peptides from different Conus species. In this study, we compare using nano-liquid chromatography coupled with electrospray ionisation-mass spectrometry and bioinformatics, the molluscivorous Conus bandanus venom to that of its close-relative Conus marmoreus of the South Central Coast of Vietnam. With this approach, we demonstrate with high precision that 92 common conopeptides are present in the venom of the two mollusc-hunting cone snails, representing 24.4% (out of 376 peptides) and 18.4% (out of 499 peptides) of C. bandanus and C. marmoreus components, respectively. The proteomic comparison of the two close-relative interspecies suggests both common and different strategies for mature conopeptide production in the two species. The overall estimation of putative conopeptide disulphide bridges reveals 75% and 61% of "disulphide-rich" peptides in C. bandanus and C. marmoreus venom components, respectively. The same amino acid sequence for Bn1.1 and Mr1.1, determined at the genomic level, was also found in the two venoms, besides other common conopeptides. Confidently, the broader distribution of C. bandanus compared to C. marmoreus guarantee new opportunities for discovering conopeptides with original pharmacological properties.