Results 1 - 10 of 7510
Results 1 - 10 of 7510. Search took: 0.031 seconds
|Sort by: date | relevance|
[en] A series of deep eutectic solvents (DESs) were prepared using glycerol and choline chloride (ChCl), and Fourier transform infrared spectrometer (FT-IR) was used to analyze the spectra of glycerol, choline chloride and DESs based on glycerol and choline chloride. Then DESs were used as the additives of mobile phase to optimize chromatographic behavior of caffeic acid in high performance liquid chromatography (HPLC). A 17-run Box-Behnken design (BBD) was employed to evaluate effect of DESs as additives by analyzing the maximum theoretical plate number. Three factors, reaction temperature (60 .deg. C, 80 .deg. C, 100 .deg. C), molar ratio of glycerol and choline chloride (2 : 1, 3 : 1, 4 : 1, n/n), and volume percent of additives (0.05%, 0.10%, 0.15%, v/v), were investigated in BBD. The optimum experiment condition was that of reaction temperature (80 .deg. C), molar ratio of glycerol and ChCl (3 : 1, n/n), and volume percent of additive (0.10%, v/v). The mean chromatographic theoretical plate number of the caffeic acid this condition was 1567.5, and DESs as additives shorten the retention time and modify the chromatogram shape, proving DESs as additives for effective theoretical plate number and column efficiency in HPLC.
[en] Standard heterogeneous electron transfer rate constant k for some important pyridinium model compounds: N-methyl-a-picolinium- , N-(2,4-dinitrophenyl)-4-(4'-pyridyl) pyridinium-, N-(phenyl)-4-(4'-pyridyl) pyridinium-, N-(cyanophenyl)-4-(4'-pyridil) pyridinium- and N-(2, 4-dinitrophenyl) pyridinium chlorides as well as 1-1' dimethyl 4-4'-bipyridinium (methyl viologen), were determined using cyclic voltammetric technique. Methods of Nicholson and Gileadi were used. k were computed using various forms of Marcus equations. It was found that the simple Marcus equation gave much higher values of k; while the precursor equilibrium-model gave better agreement with the experimental results. In all these cases an adiabatic electron transfer was assumed. It was inferred that the general practice of omitting 'lambda', the inner reorganization energy, can not be accepted in the present case: when strong electron withdrawing group nitro-, cyano-, carbomethoxy- etc. are the substituents near the reaction site, 'lambda' should not be ignored. (author)
[en] Objective: The aim of our study was to investigate the value of choline in the discrimination of benign and malignant soft tissue and bone tumors. Materials and methods: The study group consisted of thirty subjects with bone or soft tissue tumors larger than 1.5 cm in diameter. The experiments were performed in a 1.5 T MR scanner. Coils were selected according to specific locations. A single-voxel MRS was performed for three different TE (time to echo) (31, 136, 272 ms). The volume of interest was positioned on the brightest enhancement. The presence of a cholin peak on at least 2 of these spectrums was considered as the marker of malignancy. The sensitivity, specificity and accuracy of the MRS in the detection and diagnosis of malignant lesions were calculated. The reproducibility of MRS and histopathological results were tested with kappa statistics. Results: Histopathologically, 18 (60%) of the lesions were classed as malignant whereas 12 (40%) were classed as benign. With MRS, 15 (50%) of these lesions were classed as malignant and 15 (50%) as benign. Two patients who were found spectroscopically to have malignant tumors were shown histopathologically to have benign types. Five patients with an MRS showing a benign type were classed with malignant types in histopathological examinations. MRS had a sensitivity rate of 72.2%, specificity of 83.3%, and an accuracy rate of 76.6% in detecting malignant bone and soft tissue tumors. The interrater reliability of both techniques had a kappa value of 0.533. Conclusions: MRS may help in the differentiation of benign and malignant soft tissue and bone tumors.
[en] Nanoliposomes are commonly used as a carrier in controlled release drug delivery systems. Controlled release formulations can be used to reduce the amount of drug necessary to cause the same therapeutic effect in patients. One of the most noticeable factors in release profiles is the strength of the drug-carrier interaction. To adjust the pharmacokinetic and pharmacodynamic properties of therapeutic agents, it is necessary to optimize the drug-carrier interaction. To get a better understanding of this interaction, large unilamellar liposomes containing calcein were prepared using 1,2-dioleoyl-sn-glycero-3-phosphocholine, 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine, and 1,2-palmitoyl-sn-glycero-3-phosphocholine, and a mixture of them; calcein was chosen as a model polar molecule of biological interest. The thermodynamic changes induced by calcein and its location in lipid bilayers were determined by differential scanning calorimetry and Raman spectroscopy, respectively. The results reveal that calcein has no significant influence on thermotropic properties of the lipid membrane, but causing the abolition of pre-transition. The decreasing of the pre-transition can be ascribed to the presence of calcein near the hydrophilic cooperative zone of the bilayer. The change in intensity of the Raman peaks represents the interaction of calcein with choline head groups. Moreover, the impact of calcein on phosphoglyceride Langmuir layers spread at the air–water interface was studied using surface pressure-area and surface potential-area isotherms, as well as polarization-modulation infrared reflection–absorption spectroscopy and Brewster angle microscopy. The results obtained indicate that calcein introduce no major modification on the systems prepared with pure lipids
[en] Research highlights: → Autotaxin (ATX) has lysophospholipase D activity. → ATX catalyzes the formation of lysophosphatidic acid (LPA). → LPA is a mitogen, and thus is responsible for cancer. → ATX also catalyzes the formation of anti-cancerous cyclic phosphatidic acid. → Autotaxin is a novel target of cancer therapy research. -- Abstract: Autotaxin (ATX) is a catalytic protein, which possesses lysophospholipase D activity, and thus involved in cellular membrane lipid metabolism and remodeling. Primarily, ATX was thought as a culprit protein for cancer, which potently stimulates cancer cell proliferation and tumor cell motility, augments the tumorigenicity and induces angiogenic responses. The product of ATX catalyzed reaction, lysophosphatidic acid (LPA) is a potent mitogen, which facilitates cell proliferation and migration, neurite retraction, platelet aggregation, smooth muscle contraction, actin stress formation and cytokine and chemokine secretion. In addition to LPA formation, later ATX has been found to catalyze the formation of cyclic phosphatidic acid (cPA), which have antitumor role by antimitogenic regulation of cell cycle, inhibition of cancer invasion and metastasis. Furthermore, the very attractive information to the scientists is that the LPA/cPA formation can be altered at different physiological conditions. Thus the dual role of ATX with the scope of product manipulation has made ATX a novel target for cancer treatment.
[en] Nerve agents (sarin, tabun, soman and VX) are class of military important substances able to cause many severe intoxications during few minutes. Currently, the threat of misuse of these agents is daily discussed. Unfortunately, there is no single antidote able to treat intoxication caused by all of these agents. Owing to this fact, new generation of antidotes, especially acetylcholinesterase (AChE: EC 18.104.22.168) reactivators, is still developed. In this study, we have tested four newly developed AChE reactivators: 1-(4-hydroxyiminomethylpyridinium)- 5-(4-carbamoylpyridinium)-3-oxa-pentane dibromide (1), 1-(3-hydroxyiminomethylpyridinium)- 5-(4-carbamoylpyridinium)-3-oxa-pentane dibromide (2), 1,5-bis(2-hydroxyiminomethylpyridinium)- 3-oxa-pentane dichloride (3) and 1,5-bis(4-hydroxyiminomethylpyridinium)-3-oxa-pentane dibromide (4) for their potency to reactivate in vitro tabun and cyclosarin-inhibited AChE. Their reactivation efficacy was compared with currently the most promising oxime HI-6 (1-(2-hydroxyiminomethylpyridinium)-3-(4- carbamoylpyridinium)-2-oxa-propane dichloride). According to obtained results, two AChE reactivators 1 and 4 were able to reactivate tabun-inhibited AChE. On the contrary, there was no better AChE reactivator than HI- 6 able to reactivate cyclosarin-inhibited AChE
[en] A simple new method was developed for the determination of betaine in Fructus Lycii using hydrophilic interaction liquid chromatography with evaporative light scattering detection (HILIC-ELSD). Good chromatographic separation and reasonable betaine retention was achieved on a Kinetex HILIC column (2.1 x 100 mm, 2.6 μm) packed with fused-core particle. The mobile phase consisted of (A) acetonitrile and (B) 10 mM ammonium formate (pH 3.0)/acetonitrile (90/10, v/v). It was used with gradient elution at a flow rate of 0.7 mL/ min. The column temperature was set at 27.5 .deg. C and the injection volume was 10 μL. The ELSD drift tube temperature was 50 .deg. C and the nebulizing gas (nitrogen) pressure was 3.0 bar. Stachydrine, a zwitterionic compound, was used as an internal standard. Calibration curve over 10-250 μg/mL showed good linearity (R2 > 0.9992) and betaine in the 70% methanol extract of Fructus Lycii was well separated from other peaks. Intra and inter-day precision ranged from 1.1 to 3.0% and from 2.4 to 5.3%, respectively, while intra- and inter-day accuracy ranged from 100.0 to 107.0% and from 94.3 to 103.9%, respectively. The limit of quantification (LOQ) was 10 μg/mL and the recoveries were in the range of 98.2-102.7%. The developed HILIC-ELSD method was successfully applied to quantitatively determine the amount of betaine in fourteen Fructus Lycii samples from different locations, demonstrating that this method is simple, rapid, and suitable for the quality control of Fructus Lycii