Structural characterization and in vitro biomedical activities of sulfated chitosan from Sepia pharaonis

A low molecular weight sulfated chitosan (SP-LMWSC) was isolated from the cuttlebone of Sepia pharaonis. Elemental analysis established the presence of C, H and N. The sulfation of SP-LMWSC was confirmed by the presence of characteristic peaks in FT-IR and FT-Raman spectra. The thermal properties of SP-LMWSC were studied by thermogravimetric analysis and differential scanning calorimetry. Electrolytic conductivity of SP-LMWSC was measured by cyclic voltammetry and the molecular weight was determined by MALDI-TOF/MS. The molecular structure and sulfation sites of SP-LMWSC were unambiguously confirmed using H-1,C-13, 2D COSY and 2D HSQC NMR spectroscopy. SP-LMWSC exhibited increased anticoagulant activity in avian blood by delaying coagulation parameters and displayed cytostatic activity by inhibiting the migration of avian leucocytes. SP-LMWSC demonstrated avian antiviral activity by binding to Newcastle disease virus receptors at a low titer value of 1/64. These findings suggested that SP-LMWSC isolated from an industrial discard holds immense potentials as carbohydrate based pharmaceuticals in future. (C) 2015 Elsevier B.V. All rights reserved.

Folding of Protein L with Implications for Collapse in the Denatured State Ensemble

A fundamental question in protein folding is whether the coil to globule collapse transition occurs during the initial stages of folding (burst phase) or simultaneously with the protein folding transition. Single molecule fluorescence resonance energy transfer (FRET) and small-angle X-ray scattering (SAXS) experiments disagree on whether Protein L collapse transition occurs during the burst phase of folding. We study Protein L folding using a coarse-grained model and molecular dynamics simulations. The collapse transition in Protein L is found to be concomitant with the folding transition. In the burst phase of folding, we find that FRET experiments overestimate radius of gyration, R-g, of the protein due to the application of Gaussian polymer chain end-to-end distribution to extract R-g from the FRET efficiency. FRET experiments estimate approximate to 6 angstrom decrease in R-g when the actual decrease is approximate to 3 angstrom on guanidinium chloride denaturant dilution from 7.5 to 1 M, thereby suggesting pronounced compaction in the protein dimensions in the burst phase. The approximate to 3 angstrom decrease is close to the statistical uncertainties of the R-g data measured from SAXS experiments, which suggest no compaction, leading to a disagreement with the FRET experiments. The transition-state ensemble (TSE) structures in Protein L folding are globular and extensive in agreement with the Psi-analysis experiments. The results support the hypothesis that the TSE of single domain proteins depends on protein topology and is not stabilized by local interactions alone.