Thermal Stability and Decomposition Kinetic Studies of Acyclovir and Zidovudine Drug Compounds

Investigations on thermal behavior of drug samples such as acyclovir and zidovudine are interesting not only for obtaining stability information for their processing in pharmaceutical industry but also for predicting their shelf lives and suitable storage conditions. The present work describes thermal behaviors and decomposition kinetics of acyclovir and zidovudine in solid state, studied by some thermal analysis techniques including differential scanning calorimetry (DSC) and simultaneous thermogravimetry–differential thermal analysis (TG/DTA). TG analysis revealed that thermal degradation of the acyclovir and zidovudine is started at the temperatures of 400°C and 190°C, respectively. Meanwhile, TG–DTA analysis of acyclovir indicated that this drug melts at about 256°C. However, melting of zidovudine occurred at 142°C, which is 100°C before starting its decomposition (242°C). Different heating rates were applied to study the DSC behavior of drug samples in order to compute their thermokinetic and thermodynamic parameters by non-isothermal kinetic methods. Thermokinetic data showed that both drugs at the room temperature have slow degradation reaction rates and long shelf lives. However, acyclovir is considerably more thermally stable than zidovudine.     

Suitability of aquaculture effluent solids mixed with cardboard as a feedstock for vermicomposting

Recirculating aquaculture systems are highly intensive culture systems that actively filter and reuse water, thus minimizing water requirements and creating relatively small volumes of concentrated waste (compared to flow-through aquaculture systems). Vermicomposting, which uses earthworms to stabilize and transform organic wastes into valuable end-products, has been proposed as an alternative treatment technology for high-moisture-content organic wastes from agricultural, industrial and municipal sources. This study was conducted to determine if the effluent solids from a large recirculating aquaculture facility (Blue Ridge Aquaculture, Martinsville, Virginia) were suitable for vermicomposting using the earthworm Eisenia fetida. In two separate experiments, worms were fed mixtures of solids removed from aquaculture effluent (sludge) and shredded. Mixtures containing 0%, 5%, 10%, 15%, 20%, 25%, and 50% aquaculture sludge (dry weight basis) were fed to the worms over a 12-week period and their growth (biomass) was measured. Worm mortality, which occurred only in the first experiment, was not influenced by feedstock sludge concentration. In both experiments worm growth rates tended to increase with increasing sludge concentration, with the highest growth rate occurring with feedstocks containing 50% aquaculture sludge. Effluent solids from recirculating aquaculture systems mixed with shredded cardboard appear to be suitable feedstocks for vermicomposting.     

Dynamic mechanical properties of solid films of deoxyribonucleic acid

Solid films of deoxyribonucleic acid (DNA) from salmon testes were prepared by a solvent-casting method. The thermal molecular motion of the DNA film was examined by dynamic mechanical analysis (DMA). Four absorption peaks and one shoulder of the loss modulus were observed in the temperature domain from approximately 150 to 490 K. To assign these, thermal analysis employing thermogravimetry (TG) and differential thermal analysis (DTA) was used in conjunction with ultraviolet (UV)-visible and Fourier-transform infrared (FT-IR) spectroscopy. It seems most likely that, in order of increasing temperature, they are a B(I)→B(II) conformational transition, a relatively large-scale movement associated with water molecules, water evaporation, thermal denaturation of DNA, and a glass transition.     

大黄酸和大黄素的热分析及其动力学研究

本文采用热重法(TG)和差热分析法(DTA)测定了大黄酸和大黄素的DTA,TG-DTG曲线。两者的DTA曲线中皆有两个较为明显的吸热峰,第一个在熔化过程中出现,第二个发生在热分解过程中并伴随有明显的失重现象。TG曲线均有一个失重平台,失重率在90%以上。用TG-DTG法对两者在非等温条件下进行热分解动力学研究,把从TG-DTG曲线中取得的数据和31个不同的方程采用Achar微分法和Madhusudanan-Krishnan-Ni-nan(MKN)积分法对其进行非等温分解动力学研究,得到动力学参数活化能(E和指前因子A)和分解动力学机理及方程。得出结论:大黄酸和大黄素的动力学方程为dα/dt=Aexp(-E/RT)3/2(1-α)4/3[1/(1-α)1/3-1]-1和dα/dt=Aexp(-E/RT)3/2(1-α)2/3[1/(1-α)1/3]-1,其分解等合3D抗理。二者的活化能E(kJ/mol)分别为117.6和86.79,lnA/s-1分别是36.72和27.44。     

Four mixed-ligands lead(II) complexes based on 8-hydroxyquinolin (8-HQuin), [Pb(8-Quin)X]; X = 4-pyridinecarboxylate, acetate, thiocyanate and nitrate; structural and thermal studies

Lead(II) 8-hydroxychinolate complexes (8-Quin) containing four different anions, [Pb(8-Quin)X]; X = 4-pyridinecarboxylate (1), acetate (2), thiocyanate (3) and nitrate (4), have been synthesized and characterized by elemental analysis, IR-, ¹H NMR- and ¹³C NMR-spectroscopy. All these compounds were structurally characterized by single-crystal X-ray diffraction. The thermal stabilities of compounds 1–4 were studied by thermal gravimetric (TG) and differential thermal analyses (DTA). The results show the influence of different counter-ions to form dimers in compound 2, one-dimensional polymer in compound 4 and two-dimensional polymer in compounds 1 and 3.     

The interaction of the VO cation with oxidized glutathione

The interaction of the vanadyl(IV) cation with oxidized glutathione (GSSG) in solution has been investigated using spectrophotometric techniques. Two complexes, stable at different metal-to-ligand ratios, could be identified at pH = 7. A solid 2:1 VO²⁺:GSSG complex could also be isolated at pH = 4.5 and characterized by chemical analysis and infrared and electronic spectroscopies. Its thermal behavior was investigated through TG and DTA measurements.     

Characterization of bis(isoorotato)diaquamagnesium(II) dihydrate: a potentially useful complex for magnesium supplementation.

The synthesis and crystal structure of a new Mg(II) complex of stoichiometry [Mg(isoor)2(H2O)2].2H2O, where isoor is the monoanion of 5-carboxyuracil (isoorotic acid), are reported. The structure, solved by single-crystal X-ray diffractometry, shows that it crystallizes in the triclinic space group P(-1) with Z = 1. The electronic, IR and Raman spectra of the complex are briefly discussed. Its thermal behavior was also investigated by means of thermal gravimetry (TG) and differential thermal analysis (DTA) measurements in an oxygen atmosphere. Dissolution studies support the usefulness of the compound for magnesium supplementation.     

Na2Zn3(CO3)4.3H2O: a potentially useful compound for zinc supplementation.

The infrared and Raman spectra of the title compound were recorded and are briefly discussed on the basis of its structural characteristics. Its thermal behaviour was investigated by means of TG and DTA measurements. Several dissolution tests were also performed. The results support the potential usefulness of this double carbonate as a useful compound for Zn(II) supplementation.     

Comparative in-vitro biodegradation studies of epoxy and its silicone blend by selected microbial consortia

A total of six bacterial isolates were developed into two consortia and tested for utilization of epoxy silicone blends (ESBs; % w/w: 3.0) and epoxy as the sole carbon source. In-vitro biodegradation studies in minimal broth revealed that higher biomass and more sustained growth of consortia were obtained in the presence of epoxy and/or ESBs when these were incubated under aerobic conditions for 15 days. Treated samples were analyzed by Fourier transform infrared spectroscopy (FTIR) and simultaneous thermogravimetric–differential thermogravimetry–differential thermal analysis (TG–DTG–DTA), which indicated the breakage and formation of bonds in the polymer backbone. Moreover, a weight loss of 34.17 and 36.9% was found in epoxy and ESBs, respectively after 15 days of treatment with consortium-1. Further, in-vitro growth statistics study revealed more CFU count at mid-logarithmic phase in the presence of epoxy/ESBs unlikely to the absence of the polymers. However, the generation time was not affected. In the present study, consortium-1, comprising of Microbacterium sp., Pseudomonas putida and Bacterium Te 68R showed better biodegradation in comparison to consortium-2, wherein, P. putida and Pseudomonas aeruginosa were present. Overall, these results suggest that epoxy/ESBs polymers could be degraded by a biologically mediated process if a suitable consortium is used.     

TG/DTG/DTA evaluation of flame retarded cotton fabrics and comparison to cone calorimeter data

Unbleached cotton fabrics (UCF) with 12.5% polypropylene scrim treated with two phosphate-urea based fire-retardant (FR) formulations were evaluated for FR properties using thermogravimetry/differential thermogravimetry/differential thermal analysis (TG/DTG/DTA) method. In addition to testing the two FR-treated unbleached cotton fabrics (CF-FR1 and CF-FR2), bleached cotton fabric (BCF) treated with the two FR formulations (BCF-FR1 and BCF-FR2) was evaluated. Both formulations were washable with add-on of FR chemicals at 18.7% (FR1) or 17.4% (FR2) for UCF and 22.5% (FR1) or 24.9% (FR2) for BCF. The decreasing order of sums at maximal rates of samples degradation in air environment according to DTG method was: BCF (21.40%/min)>UCF (12.91%/min)>BCF-FR2 (12.83%/min)>BCF-FR1 (11.68%/min)>CF-FR2 (10.20%/min)>CF-FR1 (9.73%/min). It indicates that both formulations cause the decrease of thermooxidation of the products at slower rates than the starting material. Several endo- and exothermic peaks observed by DTA in inert and oxidative environment gives additional information about the degradation process. The order of decreasing thermal responses of the studied samples based on sums of DTA peak values of endothermic and exothermic peaks in air environment is: UCF (0.597°C/mg)>BCF (0.120°C/mg)>CF-FR1 (0.089°C/mg)>BCF-FR1 (0.077°C/mg)>CF-FR2 (0.062°C/mg)>BCF-FR2 (0.053°C/mg). This is in agreement with the cone calorimeter results according to which the flammability properties are improving with the decreasing heat release rates or ignition time prolongation in order: UCF>CF-FR1>CF-FR2. The advantage of TG/DTG/DTA method is slower linear heating rate, which allows the more detailed evaluation of the light and flammable cotton fabric.     

Effects of silicate resupply to silicate‐deprived Thalassiosira weissflogii (Bacillariophyceae) in stationary or senescent phase: short‐term patterns of growth and cell death

The ability of nutrient‐deprived phytoplankton to recover in the short term when nutrients are resupplied has been studied for nitrogen and phosphorus, but the case for silicate (Si) is poorly understood. Si‐limited Thalassiosira weissflogii (Grunow) Fryxell et Hasle (grown in batch culture) was harvested in stationary phase (when cell numbers stopped increasing ~2 d after Si depletion) and senescence (when cell numbers declined ~4 d after Si depletion) and Si was resupplied at different concentrations (from 0 to 100 μM). Cell numbers, proportion of dead cells, variable fluorescence emissions (F_v/F_m), and activities of proteases were measured during Si depletion and for 24 h after Si resupply. As Si was depleted, the specific growth rate declined, dead cells increased from ~2% in log phase, to ~25% in stationary phase to over 35% in senescence, and activities of proteases associated with cell death increased several‐fold. Concentration‐dependent recovery of growth rate was seen after 24 h for cultures resupplied with Si in stationary phase but not in senescence. However, resupply of Si at 100 μM to stationary phase cultures alone increased protease activity to nearly the levels seen in senescence. Differences in the responses to Si resupply suggest that the ability and time to recover from Si depletion depend not only on the growth phase but also on the concentration resupplied.     

石楠和蜡梅茎结冰动力学过程的差热扫描分析

在（0.66 ±0.2）℃/min（0℃~-20℃）的降温速度下,采用高分辨率差热分析法分别对石楠（Photinia serrulata Lindl.）和蜡梅（Chimonanthus praecox（L.）Link）活体幼茎和经过10 min高温煮沸的幼茎在结冰过程中的热力学行为进行分析,并根据茎的形态解剖结构对他们的结冰特征进行研究。结果显示：石楠和蜡梅的活体幼茎在结冰过程中的差热扫描曲线均出现3个放热峰;而经过高温杀死后的茎仅出现1个单放热峰。分析结果表明,2种植物活体幼茎的3个放热峰可能与其木质部、质外体、韧皮部、形成层的结冰、脱水以及髓组织的结冰、脱水过程有关。进一步采用生理盐水浸湿的滤纸进行模拟实验,结果发现差热扫描曲线出现与高温杀死的茎类似的放热峰。实验结果表明,采用高分辨率差热分析法可以探测植物组织结冰过程中的放热强度、结冰温度及其与结冰动力学过程相关的大量细节,适用于植物的结冰动力学分析。     

生物热分析研究 1.四种天然氨基酸热分解机理

本文采用热分析方法（ＴＧ,ＤＴＡ）和红外光谱等手段,对四种天然氨基酸（盐酸赖氨基酸,色氨酸,天门冬氨酸,苯丙氨酸）的热稳定性和热分解机理进行了研究,发现这四种天然氨基酸热分解的共同特点是首先失去羧基,形成胺的中间产物,然后是中间产物分解,且脱羧温度与β位碳原子上所连的基团密切相关,从电荷密度等因素出发对此进行了分析和讨论。     

Antifungal and physical characteristics of modified denture base acrylic incorporated with silver nanoparticles

doi: 10.1111/j.1741‐2358.2011.00489.x Antifungal and physical characteristics of modified denture base acrylic incorporated with silver nanoparticles Objective: This study evaluated the antifungal and physical characteristics of denture base acrylic combined with silver nanoparticles. Materials and methods: Polymerized denture acrylic disc specimens containing 0 (control), 1.0, 5.0, 10.0, 20.0 and 30.0 wt% of silver nanoparticles were placed on separate culture plate dish and 100 ìL samples of yeast suspension of Candida albicans strain were inoculated on each specimens and incubated at 37°C, for 24 h. The antifungal effects were evaluated as a number of viable cells in retrieved fungal suspension. To characterize physical aspects, specimens were tested for elution of silver cation (Ag⁺) at 24 h and 30th day, thermal analysis (TG/DTA), scanning electron microscope and energy dispersed X‐ray analysis (SEM/EDX) and color stability. Results: Significant reduced CFU was exhibited at 20.0 and 30.0 wt% of silver nanoparticles incorporated (p < 0.01) and Ag⁺ elution from specimens (maximum 0.356 ± 0.11 mg/L) contributed little to the antifungal activity considering MIC of Ag⁺ in this study (3.0 mg/L). The successful synthesis of modified denture acrylic containing silver nanoparticles was accessed by TG/DTA and EDX analysis. Conclusion: The modified denture base acrylic combined with silver nanoparticles displayed antifungal properties and acted like latent antifungal material itself with low‐releasing Ag⁺, however, the improvement of poor color stability was still required.     

Selective dehydration of bio-ethanol to ethylene catalyzed by lanthanum-phosphorous-modified HZSM-5: influence of the fusel

Bio-ethanol dehydration to ethylene is an attractive alternative to oil-based ethylene. The influence of fusel, main byproducts in the fermentation process of bio-ethanol production, on the bio-ethanol dehydration should not be ignored. We studied the catalytic dehydration of bio-ethanol to ethylene over parent and modified HZSM-5 at 250°C, with weight hourly space velocity (WHSV) equal to 2.0/h. The influences of a series of fusel, such as isopropanol, isobutanol and isopentanol, on the ethanol dehydration over the catalysts were investigated. The 0.5%La-2%PHZSM-5 catalyst exhibited higher ethanol conversion (100%), ethylene selectivity (99%), and especially enhanced stability (more than 70 h) than the parent and other modified HZSM-5. We demonstrated that the introduction of lanthanum and phosphorous to HZSM-5 could weaken the negative influence of fusel on the formation of ethylene. The physicochemical properties of the catalysts were characterized by ammonia temperature-programmed desorption (NH(3)-TPD), nitrogen adsorption and thermogravimetry (TG)/differential thermogravimetry (DTG)/differential thermal analysis (DTA) (TG/DTG/DTA) techniques. The results indicated that the introduction of lanthanum and phosphorous to HZSM-5 could inhibit the formation of coking during the ethanol dehydration to ethylene in the presence of fusel. The development of an efficient catalyst is one of the key technologies for the industrialization of bio-ethylene.     

Preparation and characterization of mixed ammonium salts of Keggin phosphomolybdate

Keggin-type modified ammonium salts of molybdophosporic acid were prepared by partial substituting of the ammonium ions by X (X = Sb^III, Bi^III or Sn^II) ions. They were characterised by BET method, XRD, ³¹P NMR, UV-Vis, Raman, IR spectroscopies and thermal analysis (TG and DTA). It appeared that introducing an element X = Sb or Sn led to partially reduced compound corresponding to the electron exchange occurring between Sb(III) or Sn(II) and Mo(VI) without modification of Keggin structure.     

The first radiation hybrid map of a perch-like fish: the gilthead seabream (Sparus aurata L)

Among Teleosts, Perciformes are the largest order of fishes and include numerous species of commercial importance. Perciformes also comprise species of primary interest for evolutionary studies and analysis of the sex determination systems and sex chromosome plasticity. Unfortunately, genomics tools and resources for Perciformes remain to be developed. Here, we report the production of a seabream whole-genome radiation hybrid (RH) panel in which quality was ascertained by the construction of a 2-Mb-resolution RH map. The map encompasses 440 markers (288 microsatellites, 82 gene-based markers, and 70 STS) suitable for linkage analysis and comparative mapping studies. Achievement of a RH panel and a whole-genome RH map should contribute to establishing seabream as a fish model among the Perciformes and should be of importance in aquaculture for marker-assisted selection, improvement of growth performance, and disease management. Development of RH maps in a cost-effective manner for other fishes with the described methodology will offer a powerful approach in aquaculture and will provide extended capabilities for comparing vertebrate genome evolution.     

Synthesis and luminescent properties of Eu(TTA)3·3H2O nanocrystallines

Nanocrystallines of rare earth complex, Eu(TTA)₃·3H₂O, were synthesized by the chemical precipitation method and were characterized by elemental analysis, ultraviolet visible absorption spectroscopy (UV–vis), infrared spectroscopy (IR), differential thermal analysis–thermogravimetry (TG‐DTA), X‐ray diffraction (XRD) and transmission electron microscopy (TEM). The size of the nanocrystallines was tunable by selecting the proper buffer system, which was used to control the pH of the solution. A small polydispersity in particle size ranging from 70 to 250 nm was obtained when ammonia was used. The nanocrystallines showed the characteristic fluorescence of europium ions and energy transfer from the organic ligand to central ions was observed by fluorescence excitation and emission spectroscopy. These nanoparticles of rare earth complexes have potential application in luminescent materials due to their excellent fluorescence properties. Copyright © 2009 John Wiley & Sons, Ltd.     

Dipalmitoylphosphatidylcholine-palmitic acid phase diagram studied by 13C nuclear magnetic resonance

The phase diagram of dipalmitoylphosphatidylcholine (DPPC) and palmitic acid mixtures in excess D2O was studied by 13C-NMR. Phase boundaries were determined from plots of apparent spin-spin relaxation time T2 (for both choline methyl and fatty acid chain carbons) versus temperature. A peritectic transition in the 1-10 mol% region, whose existence has been theoretically inferred from the Gibbs phase rule but which was undetectable by differential thermal analysis (DTA) (S.E. Schullery et al. Biochemistry, 20 (1981) 6818-6824), was located by NMR at 41.6 degrees C. A second, nearby peritectic line at 44 degrees C, which had been shown by DTA to extend from about 3-25 mol% palmitic acid, was seen by NMR only above 10 mol%. The palmitic acid/DPPC complex (2:1), with a sharp melting point at 64 degrees C, reported in earlier studies, was also seen by NMR. A phase diagram including both NMR and DTA results is presented. Important general conclusions from this study are: (i) NMR and scanning thermal analysis are complementary techniques for phase studies; each can see transitions that are invisible to the other. (ii) The case for the applicability of the Gibbs phase rule to lipid bilayer systems has been strengthened by the observance of two predicted, close-spaced boundaries. (iii) Low concentrations of fatty acids and related molecules can not be assumed to disperse as simple ideal solutes in the bilayer matrix.