China
Africa
Explore chapters and articles related to this topic
Total Synthesis of Some Important Natural Products from Brazilian Flora
Published in Luzia Valentina Modolo, Mary Ann Foglio, Brazilian Medicinal Plants, 2019
Leonardo da Silva Neto, Breno Germano de Freitas Oliveira, Wellington Alves de Barros, Rosemeire Brondi Alves, Adão Aparecido Sabino, Ângelo de Fátima
To synthesize different eusiderins, the authors traced a strategy involving a general route, varying only the reagent used in the last step responsible for the side chain and the substituents of the attached aromatic ring. The synthesis has two key steps: the first key step is a Mitsunobu reaction between the phenolic derived from the previously synthesized o-vanillin and (S)-ethyl lactate, thus fixing the first chiral center in the structure, followed by a reduction with DIBAL at −78°C that results in the formation of aldehyde 62 (Figure 12.16), a common intermediate for the other eusiderins, which undergoes an addition of an aromatic organometallic reagent that differentiates eusiderin A 58 from eusiderin B 59; after a reduction and cyclization in Amberlyst 15, formation of the intermediate occurs (63, 64), which undergoes the second key step of eusiderin synthesis (Suzuki reaction). Then, the eusiderins are synthesized from the intermediates 63 and 64, and the boronate ester side chain derived from organoboron is used, since the Suzuki reaction is a carbon-carbon cross-coupling reaction. A disadvantage faced in the synthetic route proposed by Pilkington and Barker (2012) is the step involving the formation of the second stereogenic center of the 1,4-benzodioxane ring, wherein the cyclization generates the cis and trans isomers in a ratio of 1:5, resulting in a reduction in the reaction yield due to the need to separate the products for the last step of the synthesis.
Future Perspectives on Nucleic Acid Testing
Published in Attila Lorincz, Nucleic Acid Testing for Human Disease, 2016
Larry J. Kricka, Paolo Fortina
Nucleic acid testing is a relatively young discipline and quality assurance (QA) and quality control (QC) are still in active phases of development. Validation of equipment is an important component of quality control and assurance. A thermocycler for PCR is an essential instrument for most nucleic acid tests, and the performance of thermocyclers has a direct bearing on analytical quality. The impact of thermocycler operation on PCR-based test results was studied in an inter-laboratories survey involving two standardized assays in 18 laboratories using 33 cyclers of various kinds.136 This study revealed significant variation in reaction yield, inter-block variation in results, and highlighted the importance of temperature calibration of thermocyclers for improving repeatability of data. QA and QC must be continuing priorities to allow further improvements in the quality of molecular diagnostic testing and attain the accuracy and precision levels currently achieved by less complicated serum chemistry tests.
Gas Phase Sequence Analysis of Proteins/Peptides
Published in Ajit S. Bhown, Protein/Peptide Sequence Analysis: Current Methodologies, 1988
R1 is a sweet smelling, volatile liquid. In the presence of base, the PITC in it reacts quantitatively with the free amino-terminal amino group of a peptide (as well as amino side chain groups) to form the phenylthiocarbamyl-protein (PTC-protein). In the standard degradation cycles for the sequencer, R1 is delivered to the cartridge to saturate the filter (usually a 3-sec delivery is sufficient). Three separate deliveries are made in-between deliveries of the basic R2. These repeated R1 deliveries increase the reagent-protein contact and improve the reaction yield. After each R1 delivery, argon removes the nonreactive heptane.
Evaluation of the environmental impact of magnetic nanostructured materials at different trophic levels
Published in Nanotoxicology, 2021
Roberto Carlos Valerio-García, Iliana E. Medina-Ramírez, Mario A. Arzate-Cardenas, Ana Laura Carbajal-Hernández
The synthesis consisted of the addition of 165 mg of FeCl3 and 250 mg of FeCl2 • 4H2O to 150 ml of the organic coating solution: sodium citrate (0.1 M), PVP (0.1 M), glycine (0.1 M) and Arabic gum (2.5%) respectively. The mixtures were stirred for 15 minutes. Then, 20 mL NH4OH (28%, v/v) was dropwise added, and the resulting solutions were kept at 70° C under continuous stirring for 2 h. Magnetic particles were separated with the aid of a magnet and washed three times with ethyl ether (10 mL) and absolute ethanol (10 mL). Once the powder was dried after ether evaporation, it was then homogenized in the mortar and sonicated for 5 min. The reaction yield was about 90%. Finally, each material was analyzed based on its colloidal stability.
Quercetin-loaded nanoparticles enhance cytotoxicity and antioxidant activity on C6 glioma cells
Published in Pharmaceutical Development and Technology, 2020
Melike Ersoz, Aysegul Erdemir, Serap Derman, Tulin Arasoglu, Banu Mansuroglu
Encapsulation efficiency (EE) of the Qu1NP, Qu2NP, and Qu3NPs were determined using an indirect method via spectrophotometric evaluation of supernatant obtained after centrifugation (Arasog˘lu and Derman 2018). Unentrapped quercetin amount in the supernatant was detected with an UV-Vis spectrometer at 374 nm. A previously constructed standard calibration curve was used to calculate quercetin concentration. The gravimetric method was used to determine the reaction yield (RY) of the nanoparticle synthesis process. The RY was determined as the ratio between synthesized nanoparticles amount and total amount of quercetin and PLGA. Reaction yield and encapsulation efficiency were determined by the following equations respectively.
l -Carnitine conjugated chitosan-stearic acid polymeric micelles for improving the oral bioavailability of paclitaxel
Published in Drug Delivery, 2020
Tan Yang, Jianfang Feng, Qian Zhang, Wei Wu, Hailan Mo, Lanzhen Huang, Wei Zhang
The micelle skeleton CS-SA was synthesized by EDC-mediated amido formation between carboxyl group of SA and amine group of CS. Since the carboxyl group was activated by EDC to promote the conjugation to the amine group of CS, the reaction would be accelerated. The molecular weight of CS, as an important factor affecting the reaction yield, was trialed, including Mw 30k, 10k, 3–6k, and 2k. Since CS with high molecular weight was poorly soluble in water and the low was hard to obtain amphiphilic molecule due to its excessive water-solubility, the target molecular weight 3–6k was chosen due to the higher reaction yield of amphiphilic CS-SA.