China
Africa
Explore chapters and articles related to this topic
Separation Of The Bound And Unbound Forms Of The Radioactivity
Published in Erwin Regoeczi, Iodine-Labeled Plasma Proteins, 2019
The suitability of unknown proteins for anion-exchange chromatography can be tested in several ways. After removing the unbound radioactivity by a different method (e.g., dialysis), a minute amount of a labeled protein can be applied to an exchanger column to see how the radioactivity behaves. Unlabeled proteins can be tested spectrophotometrically. A known volume of a protein stock solution is loaded on the exchanger and is eluted with a known volume of an eluant; an aliquot of the stock solution is diluted separately with the eluting solution to the same degree, and the absorbance of both specimens is determined at 280 nm; for proteins which are inert towards the resin the readings are the same.
Receptors and Signal Transduction Pathways Involved in Autonomic Responses
Published in Kenneth J. Broadley, Autonomic Pharmacology, 2017
The effects of cAMP as a second messenger are terminated by its hydrolysis to AMP (5’-adenosine monophosphate), which does not activate cAMP-dependent protein kinase (PKA), by the actions of phosphodiesterase (PDE, EC 3.1.4.17) (Figures 13.3 and 13.7). Inhibition of PDE will therefore allow intracellular cAMP levels to rise which is the basis of the pharmacological responses to PDE inhibitors. This enzyme is not a single entity but exists as several different isoenzymes. Confusion has occurred over different systems used for the naming of these isoenzymes. Initially, it was according to their order of elution from anion-exchange chromatography. This was not entirely satisfactory since the number of peaks of PDE activity can depend upon both the tissue and the chromatographic conditions, and a peak may include more than one isoenzyme. The classification now most widely adopted relates not only to the elution pattern, but also to the primary amino acid sequences of the enzyme and that deduced from cDNA. It also takes into account the kinetic properties of isoenzyme affinities for hydrolysis of cAMP or cGMP, susceptibility to inhibition by these cyclic nucleotides and by pharmacological agents.
Long Lived and Unconventional PET Radionuclides
Published in Martin G. Pomper, Juri G. Gelovani, Benjamin Tsui, Kathleen Gabrielson, Richard Wahl, S. Sam Gambhir, Jeff Bulte, Raymond Gibson, William C. Eckelman, Molecular Imaging in Oncology, 2008
Jason S. Lewis, Rajendra K. Singh, Michael J. Welch
Multiple methods are available for the separation of radiocopper from enriched nickel. These include precipitation, solvent extraction, and electroplating. However, ion chromatography is the most effective method of isolating high-purity no-carrier-added radionuclide. Anion exchange chromatography has been the most widely used method of ion exchange separation (9,11,14–16) resulting in high specific activity 64Cu, but the use of cation exchange methods has been reported (17). Separation of the 64Cu from the expensive isotopically enriched nickel results in the ability to recycle the target material, which in turn dramatically reduces costs.
Interrogating heterogeneity of cysteine-engineered antibody-drug conjugates and antibody-oligonucleotide conjugates by capillary zone electrophoresis-mass spectrometry
Published in mAbs, 2023
Tian Xu, Fan Zhang, Daoyang Chen, Liangliang Sun, Daniela Tomazela, Laurence Fayadat-Dilman
Composed of mAbs conjugated to oligonucleotides such as small interfering RNA (siRNA), and anti-sense oligonucleotides,19,44–47 AOCs have been reported as promising gene-silencing cancer therapeutics and enhancing reagents in radiotherapy.44,45 While most AOC drugs are in the preclinical stages, clinical trials for several (DYNE-101, DYNE-251, AOC 1001, AOC 1044, AOC 1020) have recently started. The analyses of AOCs also face challenges, particularly for OAR species characterization.19,47 The conventional chromatographic methods developed for resolving DAR variants of ADCs based on hydrophobicity, such as HIC and RPLC, do not apply to AOCs.19 Most recently, native SEC was coupled with Fourier transform MS to characterize AOCs, but the direct resolution of DAR variants is difficult with this method.47 Despite the challenges, the OAR species of AOCs are potentially resolvable based on their heterogeneity in charge, given that oligonucleotides carry various negative charges and can significantly modify the net charge of AOCs. Previously, a study successfully applied anion-exchange chromatography to separate the DAR of AOCs.44 However, the method relied on a high concentration of sodium chloride as a mobile phase for separation and cannot be directly coupled to MS for mass characterization of individual species. Other than ion exchange chromatography, CZE can separate AOC variants with charge heterogeneity. Herein, we purpose a CZE-MS method for resolving and characterizing OARs of cysteine-engineered AOCs.
Polysaccharides from Hemerocallis citrina Baroni Inhibit the Growth of Hepatocellular Carcinoma Cells by Regulating the Wnt/β-Catenin Pathway
Published in Nutrition and Cancer, 2023
TianYu Sang, Yue Jun Fu, Li Song
The monosaccharide composition of HcBPS2 was measured by high-performance anion exchange chromatography analysis using a Dionex ICS-5000 system equipped with a Dionex CarbopacTMPA20 column (3.0 mm × 150 mm). The standard monosaccharides included fucose, rhamnose, arabinose, galactose, glucose, xylose, mannose, fructose, ribose, galacturonic acid, glucuronic acid, galacturonic acid, galacturonic acid, glucosamine hydrochloride, glucosamine hydrochloride, N-acetyl-d-glucosamine, guluronic acid, and mannose acid. The sample was hydrolyzed with trifluoroacetic acid (TFA) at 120 °C for 3 h. After acid hydrolysis, the solution was transferred to a tube to be blown and dried with nitrogen. Deionized water was added, and the sample was centrifuged at 12000 rpm for 5 min. The supernatant was used for high-performance anion exchange chromatography analysis.
Improving titer while maintaining quality of final formulated drug substance via optimization of CHO cell culture conditions in low-iron chemically defined media
Published in mAbs, 2018
Jianlin Xu, Matthew S. Rehmann, Xuankuo Xu, Chao Huang, Jun Tian, Nan-Xin Qian, Zheng Jian Li
Since the 7-L run achieved a good titer with acceptable drug substance color (Table 1 and Fig. 4), the prototype Process B using long-term passage seeds in low-iron media was scaled up in both 50-L and 500-L bioreactors. Although both titer (Fig. 5) and final drug substance color (data not shown) were good, as expected, the charge variant profile did not fully match the early-phase Process A (Table 2). The prototype Process B resulted in a significantly lower main peak and a much higher basic peak than Process A (Table 2). To identify the root cause, the charge variant profile at different steps of downstream processing was examined (Fig. 6). While the anion exchange chromatography step led to significant changes in the amounts of acidic and main species, basic species were relatively constant throughout all downstream processing steps (Fig. 6). Therefore, we concluded that the difference of basic species between Process A and prototype Process B was mainly due to upstream changes rather than downstream processing.