Ethanolamine buffers

The kinetics of demethylation were followed in hermetically closed vials in a water bath at 25°C. Ethanolamine/HCl buffer, at a final molarity of 0.2 M, was used to vary the pH. Tubes containing 1 ml of pectin solution in distilled water were prepared and at t = 0, 1 ml of ethanolamine buffer was added. One tube in each series was used to read the initial pH of the... 

The rate of nucleophilic substitution reaction between F and 6 have been studied at constant pH (attained by Tris and ethanolamine buffers), 25°C, and at different [CTACl], and the observed data have been analyzed in terms of PIE model. The pH- and buffer-independent miceUar rate constant, k (= 0.096 A/ sec ) is similar to that measured in bulk water, that is, = 1. The value... 

Fig. 2 Time-course of demethylation of a pectin solution (-5 mg/ml) at 25°C in 0.2 M ethanolamine/HCl buffer.

We found a slight decrease of pH during reaction (0.1-0.2 pH units in the buffer zone of ethanolamine), which however translated as a decrease of about 20% of the concentration of OH ions. Above pH 10.5, the loss in OH ions reached about 40% of the initial concentration. This variation could be predicted by taking into account the need for replacement of the buffer ions at any time t 0 eletroneutrality implies that for every carboxylate liberated (i.e. every methoxylated galacturonate saponified), one molecule of ethanolamine is converted from the base form (EtNHj) to the salt form (EtNH, ). The concentration of the base and salt forms at... 

Twenty-three kinetics have been carried out at 25°C for pH values from 8.25 to 11.25. The rate constant, calculated as the average of all the ks, was of 27.2 9.0 mol 1 min. The pH correction according to equation (2) was not perfect, as there was a tendency to obtain higher k values at lower pH values. However, this was specially true for extreme vdues of our pH range, where the buffer capacity of ethanolamine was limited (higher pHs) or the reaction proceeded very slowly (low pHs), impairing the precision of the data. Another factor that might explain the dispersion of the data is lack of precision of pH measurement (no better than 0.02 pH units). 

PGIP, purified fi om P.vulgaris hypocotyls [11], was immobilized to the sensor ch via amine coupling. A continuous flow of HBS buffer (5 pl/min) was mantained over the sensor surface. The carboxylated dextran matrix of the sensor surface was first activated by a 6-min injection of a mixture of N-hydroxy-succinimide and N-ethyl-N - (3-diethylaminopropyl) carbodiimide, followed by a 7-min injection of PGIP (lOng/pl in 10 mM acetate, pH 5.0). Hie immobilization procedure was con leted by a 7-min injection of 1 M ethanolamine hydrochloride to block the remaining ester groups. 

The polyamines putrescine, cadaverine, spermidine, and spermine, which are seen at elevated levels in some victims of cancer, were separated on a Technicon (The Technicon Company Chauncey, NY) TSM Amino Acid Analyzer packed with an 8% divinylbenzene-co-polystyrene sulfonated resin with post-column ninhydrin detection.111 Amines such as ethanolamine, noradrenaline, hexamethylene diamine, methoxytryptamine, spermine, and spermidine were separated from amino acids on a DC-4A cation exchange resin.112 A similar approach, using a Beckman Model 121M amino acid analyzer equipped with an AA-20 column, was also successful.113 A Polyamin-pak strong cation exchange column (JASCO) was eluted with a citrate buffer for the detection of putrescene, spermine, cadaverine, and 1,5-diaminohex-ane from rat thymus.114 A post-column o-phthaldehyde detection system was used. 

Saber and Sidky [39] described polarographic estimations of Bayluscide (I) (niclosamide) or its ethanolamine salt (II). Solutions of I or II containing 80% by volume methanol (the rest was the buffer components in H20) yielded highly reproducible polarograms [39]. 

The amidine bond formed is quite stable at acid pH however, it is susceptible to hydrolysis and cleavage at high pH. A typical reaction condition for using imidate crosslinkers is a buffer system consisting of 0.2 M triethanolamine in 0.1 M sodium borate, pH 8.2. After conjugating two proteins with a bifunctional imidoester crosslinker, excess imidoester functional groups may be blocked with ethanolamine. 

Wash beads with coupling buffer and resuspend in the same buffer containing 100 mM of an amine-containing hydrophilic quenching molecule to block excess reactive sites (i.e., ethanolamine or Tris). 

Centrifuge and wash the particles at least 3 times with buffer to remove unreacted protein and ethanolamine. Finally, suspend the particles in a suitable storage buffer containing a preservative. 

Add ethanolamine to the particle suspension at a final concentration of 0.1 M to quench any remaining active groups and react with mixing for 1 hour. Other amine-containing quenchers may be used, too, such as Tris buffer. Note DSC-activated sites on the particles that completely hydrolyze will revert back to the original hydroxyls. 

Wash the particles with coupling buffer and block excess reactive groups by resuspending in 50 mM ethanolamine, pH 9.0. React for 1 hour at room temperature with mixing. 

Note Some protocols do not call for a reduction step. As an alternative to reduction, add 50 pi of 0.2 M lysine in 0.5 M sodium carbonate, pH 9.5 to each ml of the conjugation reaction to block excess reactive sites. Block for 2 hours at room temperature. Other amine-containing small molecules may be substituted for lysine—such as glycine, Tris buffer, or ethanolamine. 

For calculation it was assumed that these five phospholipids together accounted for all of the phospholipids of the membrane. In the actual analyses, other phospholipids (primarily lysophosphatidyl choline and lysophosphatidyl ethanolamine) were found to account for less than 5% of the total. The heavy and light microlipid droplet fractions were obtained by sucrose density gradient centrifugation. Heavy fractions were collected between 0.5 and 1.0 M sucrose and light fractions banded at the 0.5 M sucrose-buffer interface. 

---