Preparation and physico-chemical characterization of chitin and chitosan from the pens of the squid species, Loligo lessoniana and Loligo formosana

β-chitin and its chitosan from the pens of Loligo lessoniana and Loligo formosana has been isolated, prepared, and physico-chemically characterized to demonstrate a potential chitin source. Without deminerization due to negligible ash content, only deproteinization was used in the chitin isolation with an yield of 35–38%, without significant difference either between the two species or the collection seasons. Reducing step not only saves production cost but also obviates acid pollutant. Mild alkaline deacetylation with various time periods was employed in the chitosan preparation. Optical rotation and thermal transition of chitin from both species suggested the weak intermolecular forces compared with shrimp chitin. The results of nitrogen contents indicate the effectiveness of the deproteinization method used. The samples were categorized as a Class III: moderate hygroscopicity. Traces of elements presented in pens markedly decreases but are incapable to be got rid of within the step of chitin–chitosan preparation. In addition, a small amount of cadmium, as the contamination, was detected in the samples from L. formosana.     

The Role of Caprylate Ligand Ion on the Stabilization of Human Serum Albumin

Sodium caprylate was added to a pharmaceutical-grade human serum albumin (HSA) to stabilize the product. In this study we have aimed to establish how caprylate ligand protects HSA from thermal degradation. The fatty acid stabilizer was first removed from commercial HSA by charcoal treatment. Cleaned HSA was made to 10% w/v in pH 7.4 buffered solutions and doped with sodium caprylate in serial concentrations up to 0.16 mmol/g-protein. These solutions as well as a commercial HSA, human serum, and enriched-albumin fraction were subjected to differential scanning calorimetry (DSC) within the temperature range of 37–90°C at a 5.0°C/min scanning rate. The globular size of the cleaned HSA solutions was measured by dynamic light scattering. The denaturing temperatures for albumin with sodium caprylate and a commercial one were significantly higher than for albumin only. It was found that the protein globules of cleaned HSA were not as stable as that of the native one due to aggregation, and the caprylate ion may reduce the aggregation by enlarging the globules’ electrical double layer. A rational approximation of the Lumry-Eyring protein denaturation model was used to treat DSC denaturing endotherms. The system turned from irreversible dominant Scheme: to reversible dominant Scheme: with the increase in caprylate concentration from null to ~0.08 mmol/g-protein. It was postulated that the caprylate ligand may decrease the rate of reversible unfolding as it binds to the IIIA domain which is prone to reversible unfolding/refolding and causes further difficulty for irreversible denaturation which, in turn, HSA can be stabilized.KEY WORDS: differential scanning calorimetry, human serum albumin, Lumry-Eyring model, protein denaturation, sodium caprylate     

Thermal behavior of a pharmaceutical solid acetaminophen doped withp-aminophenol

Thermal behavior of a series of acetaminophen (APAP) doped withp-aminophenol (PANP) was studied by differential scanning calorimetry (DSC) to determine whether it exhibited a eutectic system. Within the temperature range of 120 to 200° C, accurately weighed (1–2 mg) samples sealed in hermetic pans were calorimetrically scanned with a low scanning rate of 1° C/min. The mixture formed a single eutectic with the composition ratio APAP/PANP of 0.6/0.4 at a temperature of 138° C, where it liquefied. Melting began as early as at the eutectic point, which was below the melting temperature of APAP (169° C). The melting point as well as heat of APAP fusion was depressed with the increase in doped PANP. It was postulated that there might be a deficit heat of APAP fusion in APAP doped with PANP, which was coincident with the heat consumed by early liquefaction. The deficit heat was used to correct fraction molten in the van’t Hoff law of purity determination. It was found that the purity determination of APAP doped with PANP was comparable to the UV-spectroscopic method up to the maximum doped PANP level of 8 mol percent. It was concluded that DSC was able to approach early heat of liquefaction of APAP doped with PANP. The van’t Hoff law may be applicable to the determination of APAP with the presence of PANP as a eutectic impurity.     

Theoretical Aspects of Differential Scanning Calorimetry as a Tool for the Studies of Equilibrium Thermodynamics in Pharmaceutical Solid Phase Transitions

Although differential scanning calorimetry (DSC) is a non-equilibrium technique, it has been used to gain energetic information that involves phase equilibria. DSC has been widely used to characterize the equilibrium melting parameters of small organic pharmaceutical compounds. An understanding of how DSC measures an equilibrium event could make for a better interpretation of the results. The aim of this mini-review was to provide a theoretical insight into the DSC measurement to obtain the equilibrium thermodynamics of a phase transition especially the melting process. It was demonstrated that the heat quantity obtained from the DSC thermogram (ΔH) was related to the thermodynamic enthalpy of the phase transition (ΔH ^P ) via: ΔH?=?ΔH ^P /(1?+?K ^??1) where K was the equilibrium constant. In melting, the solid and liquefied phases presumably coexist resulting in a null Gibbs free energy that produces an infinitely larger K. Thus, ΔH could be interpreted as ΔH ^P. Issues of DSC investigations on melting behavior of crystalline solids including polymorphism, degradation impurity due to heating in situ, and eutectic melting were discussed. In addition, DSC has been a tool for determination of the impurity based on an ideal solution of the melt that is one of the official methods used to establish the reference standard.     

Behavior of Freezable Bound Water in the Bacterial Cellulose Produced by Acetobacter xylinum: An Approach Using Thermoporosimetry

The aim of the study is to examine thermal behavior of water within reticulated structure of bacterial cellulose (BC) films by sub-ambient differential scanning calorimetry (DSC). BC films with different carbon source, either manitol (BC (a)) or glycerol (BC (b)), were produced by Acetobacter xylinum using Hestrin and Shramm culture medium under static condition at 30 ± 0.2°C for 3 days. BC samples were characterized by electron scanning microscopy and X-ray diffraction spectroscopy. The pore analysis was done by B.H.J. nitrogen adsorption. The pre-treated with 100% relative humidity, at 30.0 ± 0.2°C for 7 days samples were subjected to a between 25 and −150°C-cooling–heating cycle of DSC at 5.00°C/min rate. The pre-treated samples were also hydrated by adding 1 μl of water and thermally run with identical conditions. It is observed that cellulose fibrils of BC (a) were thinner and reticulated to form slightly smaller porosity than those of BC (b). They exhibited slightly but non-significantly different crystalline features. The freezable bound water behaved as a water confinement within pores rather than a solvent of polymer which is possible to use thermoporosimetry based on Gibb–Thomson equation to approach pore structure of BC. In comparison with nitrogen adsorption, it was found that thermoporosimetry underestimated the BC porosity, i.e., the mean diameters of 23.0 nm vs. 27.8 nm and 27.9 nm vs. 33.9 nm for BC (a) and BC (b), respectively, by thermoporosimetry vs. B.H.J. nitrogen adsorption. It may be due to large non-freezable water fraction interacting with cellulose, and the validity of pore range based on thermodynamic assumptions of Gibb–Thomson theory.     

Thermal porosity analysis of croscarmellose sodium and sodium starch glycolate by differential scanning calorimetry

The aim of the study was to demonstrate the applicability of differential scanning calorimetry (DSC) on porosity analysis for cellulose and starch. Croscarmellose sodium (CCS) and sodium starch glycolate (SSG) were allowed to sorb moisture in 85%, 90%, 95%, and 100% relative humidity (RH) at 40°C for 24 hours. The pretreated samples were then subjected to DSC running temperature ranging from 25°C to −50°C at a cooling rate of 10°C/min. The cooling traces of water crystallization, if present, were transformed to porosity distribution via capillary condensation using Kelvin's equation. The porosity analysis of CCS and SSG was also done using nitrogen adsorption as a reference method. It was found that sorbed water could not be frozen (in cases of 85% and 90% RH) until the moisture content exceeded a cutoff value (in cases of 95% and 100% RH). The nonfreezable moisture content was referred to tightly bound, plasticizing water, whereas the frozen one may be attributed to loosely bound water condensation in pore structure of CCS and SSG surfaces. Not only capillary condensation but also the tightly bound, nonfreezable monolayer water lying along the inner pores of the surface contributed to porosity determination. Good agreement with less than 5% deviation of mean pore size was observed when the results were compared with nitrogen adsorption. The narrower pore size distributions, however, were obtained because of the limitations of the technique. It was concluded that pore analysis by DSC could be successful. Further research needs to be done to account for limitations and to extend the applicability of the technique.