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PubMed2005

Rapid deprotection of N-Boc amines by TFA combined with freebase generation using basic ion-exchange resins.

The deprotection of N-Boc amines was rapidly accomplished using 5 equivalents of TFA in methylene chloride in a focused microwave instrument with irradiation at 60 degrees C for 30 min. The freebase amines are then obtained by scavenging the crude reaction mixture with the basic Amberlyst A-21 ion-exchange resin. This procedure is suitable for the parallel deprotection of N-Boc amines.

Amines↗
PubMed1987

Studies on the physical state of water in living cells and model systems. VII. Exclusion of sugars and sugar alcohols from the water in sulfonate ion exchange resins: the "size rule".

The equilibrium distribution of D-arabinose, glycerol, D-ribose, sorbitol, sucrose or inulin in the water of sulfonate ion exchange resins (containing as counterions to the sulfonate anions, H+, Li+, Na+, K+, Rb+, Cs+, NH4+, tetraethylammonium or tetra-n-butyl-ammonium) was studied, usually at one temperature (25 degrees C) but sometimes at two (25 degrees C, 0 degrees C). The apparent equilibrium distribution (p-value) changes with the nature of the counterion, temperature and the molecular weights of the sugar, sugar alcohols, and derivative in question. Linear correlation coefficients between the molecular weights of the solutes and their respective p-values in the range of -0.92 to -0.93 were obtained when the resins were in the Li+, Na+, K+, or Rb+ form.

Anion Exchange Resins↗
PubMed1992

Measurement of 226Ra and 228Ra in water by gamma-ray counting after preconcentration on ion-exchange resin.

A rugged resin concentration method followed by gamma counting was developed for measuring 226Ra and 228Ra in drinking water. Using typical distribution system pressure, 310 kPa (45 psig), radium in a 20-L sample was concentrated 100-fold onto 200 mL of ion-exchange resin beads that were then sealed in a glass jar for gamma activity measurement. Parameters and materials affecting the concentration step were studied with the objective of maximizing radium recovery in a short time. Empty bed contact times were varied from 0.1-3.0 min (2.0-0.67 mL min-1) and input concentrations of radium were varied from 370-3700 Bq m-3 (10-100 pCi L-1). Varying these parameters did not affect the percentage recovery of radium by the resin. At each empty bed contact time after all adsorbent media were tested, more than 99% of the influent radium was adsorbed. In these experiments, activities were counted for 100 min using a gamma-ray spectrometer equipped with a 3 x 3-inch sodium iodide (thalium-activated) [NaI(Tl)] crystal detector. Activity calculations were based on resin loaded with traceable standard solutions of 226Ra and 286Ra from the National Institute of Standards and Technology. Analyzing entire spectra with a least-squares analysis program resulted in limits of detection for 226Ra and 228Ra of 7.4 Bq m-3 (0.2 pCi L-1) and 33.3 Bq m-3 (0.9 pCi L-1), respectively.

Ion Exchange Resins↗
PubMed1994

Ion exchange resins for the purification of monoclonal antibodies from animal cell culture.

We have compared various ion exchangers for monoclonal antibody (MAb) purification using different starting materials such as ascitic fluid and cell culture supernatant. Twelve cation and anion exchange resins were tested so far. Purification of MAbs with regard to the starting material is described. In well-defined conditions of adsorption (20 mM MES buffer, pH 6.50), one purification step based on cation-exchange chromatography is generally sufficient to achieve at least 90% purity of the MAb, even when produced by animal cell culture. Cation-exchange supports exhibit higher capacity for MAbs compared to anion exchangers. Among the cation exchangers tested, we have selected the cross-linked matrix S Sepharose FF for its large specificity and capacity for MAbs. Considering these key parameters and also the good mechanical resistance of the S Sepharose FF, we describe how, by varying the flow rate, sample concentration, and size of the column, the productivity may be improved in a monoclonal antibody purification process. Finally, a general 'gram scale' purification protocol of MAbs produced by animal cell cultures is proposed. This protocol, based on economical adsorption conditions and three steps of elution (100 mM, 200 mM and 1 M NaCl), allows the recovery of highly purified MAbs.

Animals↗