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Reactivities of Amino Acids and Proteins with Iodine
Published in Erwin Regoeczi, Iodine-Labeled Plasma Proteins, 2019
Diiodination of histidine on a gram scale is usually carried out by the method of Brunings.88 In brief, an aqueous alkaline (0.5 M NaOH) solution of the amino acid, placed in an ice bath, is stirred vigorously with pure hexane, and calculated volumes of iodine-hexane are run in from a separatory funnel slowly (over 1 to 2 hr) so that the iodine color in the emulsion is not excessive. The iodine content is maintained in this way at the minimum allowed by the substitution reaction. The mixture is stirred vigorously enough to ensure emulsification throughout, continuing for approximately 30 min after the addition is complete. Then the iodide produced by the substitution reaction is oxidized to I2 by the addition of KI03 and HC1. The mixture is allowed to separate and the hexane-iodine layer is removed, the extraction being repeated 2 to 3 times. The residue is concentrated to approximately 50 m𝓁 by heating at 50 to 60°C in vacuo, followed by pH adjustment to 2 to 4 with ammonia. On standing overnight in the cold at this pH, diiodohistidine precipitates.
Preparation of Low Molecular Weight Copper Complexes
Published in Robert A. Greenwald, CRC Handbook of Methods for Oxygen Radical Research, 2018
Our routine procedure is to add the solution of copper chloride to the ligand solution. The ligand solution is stirred rapidly with a Teflon®-coated stirring bar, and the copper chloride solution is dropped slowly into the vortex of the stirred ligand solution from a burette or separatory funnel. Rapid stirring appears to avoid entrapment of ligand solution in the precipitating product. Since the kinetic rate of complex formation is very fast, the reaction is complete soon after addition of the copper chloride. We continue to rapidly stir the resultant suspension for an additional 30 to 60 min/hr to enable shear forces to act upon the suspended particles and further reduce entrapment of the solution and its contents.
In vitro α-glucosidase inhibition by Brazilian medicinal plant extracts characterised by ultra-high performance liquid chromatography coupled to mass spectrometry
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2022
Mariacaterina Lianza, Ferruccio Poli, Alan Menezes do Nascimento, Aline Soares da Silva, Thamirys Silva da Fonseca, Marcos Vinicius Toledo, Rosineide Costa Simas, Andréa Rodrigues Chaves, Gilda Guimarães Leitão, Suzana Guimarães Leitão
Countercurrent chromatography separations were performed on a P.C. Inc. (Potomac, MD) apparatus equipped with a triple polytetrafluoroethylene multi-layer coil (15 mL + 80 mL + 280 mL, 1.6 mm i.d.) equilibrated by a counterweight. The rotation speed is adjustable from 0 to 1000 rpm. The 80-mL coil was used in all experiments. The solvents were pumped with a HPLC Solvent Delivery System Model M-45 Waters (Milford, MA) and the fractions were collected in a Super Fraction Collector SF-2120 Advantec MFS Inc. (Tokyo, Japan). The solvent systems tests were performed as follows: small amounts of a sample extract were dissolved in a test tube containing a two-phase solvent system. After shaking and allowing compounds’ partition between the two phases, equal aliquots of each phase were spotted individually on silica gel TLC plates to determine the distribution coefficients (KD) by visual inspection. Solvent systems used in all separations by CCC were prepared in a separatory funnel at room temperature. After the equilibrating, the two phases were separated and degassed by sonication for 5 min. In each run, a CCC column was first filled with the stationary phase, after setting the rotation, the mobile phase was pumped in. Samples were dissolved in equal volumes of phases and were injected after the hydrodynamic equilibrium inside the column was reached.
Enhanced oral absorption of insulin: hydrophobic ion pairing and a self-microemulsifying drug delivery system using a D-optimal mixture design
Published in Drug Delivery, 2022
Yoon Tae Goo, Sangkil Lee, Ji Yeh Choi, Min Song Kim, Gi Hyeong Sin, Sun Ho Hong, Chang Hyun Kim, Seh Hyon Song, Young Wook Choi
The log P values of different HIP complexes were determined by the shake-flask method (Zhang et al., 2021). Prior to the experiment, distilled water and n-octanol were poured into a separatory funnel, vigorously shaken, and then allowed to settle for 24 h to mutually saturate. Stock solutions of HIP complexes in the saturated n-octanol were prepared and mixed with pre-saturated distilled water at a 1:10 (vol/vol) ratio. INS was dissolved in saturated distilled water and then mixed with pre-saturated n-octanol. The tube was incubated at 25 °C for 24 h with continuous shaking (50 rpm) and allowed to separate for 1 h, after which it was centrifuged at 16,000g for 10 min. Afterward, samples from both phases were carefully analyzed by HPLC. The log P value was calculated as follows: log P = log (Cn-octanol/Caqueous), where Cn-octanol and Caqueous refer to the concentrations of INS in the n-octanol and aqueous phases, respectively, at equilibrium.
Biochemical, hematological, and hormonal profile of rats orally administered methanol stem bark extract of Napoleona vogelii Hook and Planch (Lecythidaceae)
Published in Drug and Chemical Toxicology, 2019
Victor Olabowale Ikumawoyi, Esther Oluwatoyin Agbaje, Olufunsho Awodele, Akinwumi Akinyinka Akinyede
The method of Obdoni and Ochuko (2001) was employed. The samples were ground and 20 g of each was put into a conical flask and 100 cm3 of 20% of aqueous ethanol was added. The samples were heated over a hot water bath for 4 h with continuous stirring at approximately 55 °C. The mixture was filtered and the residue re-extracted with another 200 ml of 20% of ethanol. The combined extracts were reduced to 40 ml over water bath at approximately 90 °C. The concentrate was transferred into a 250 ml separatory funnel and 20 ml of diethyl ether was added and shaken vigorously. The aqueous layer was recovered while the ether layer was discarded. The purification process was repeated. Sixty milliliter of n-butanol was added. The combined n-butanol extracts were washed twice with 10 ml of 5% of aqueous sodium chloride. The remaining solution was heated in a water bath. After evaporation the samples were dried in the oven to a constant weight and the saponin content was calculated.