Buffering effect blood plasma

Basic procedure (ACW kit) Mix 1500 pL of ACW reagent 1 (diluter) with 1000 pL of ACW reagent 2 (buffer) and 25 pL of photosensitizer reagent (lumi-nol based). Start measurement after brief vortexing. Assayed solution (or control) is added before addition of photosensitizer reagent. Volume of ACW reagent 1 is reduced by the volume of assayed plasma sample. Standard substance ascorbic acid. Duration of measurement 2-3 min. Measured parameter effective lag phase = lag-phase sample - lag-phase blank. Assayed amount of human blood plasma 2 pL. 

Due to their high concentration, plasma proteins—and hemoglobin in the erythrocytes in particular—provide about one-quarter of the blood s buffering capacity. The buffering effect of proteins involves contributions from all of the ionizable side chains. At the pH value of blood, the acidic amino acids (Asp, Glu) and histidine are particularly effective. 

Tin metabolic acidosis (p. 652) there is an increase in glutamine processing by the kidneys. Not all the excess NH4 thus produced is released into the bloodstream or converted to urea some is excreted directly into the urine. In the kidney, the NH% forms salts with metabolic acids, facilitating their removal in the urine. Bicarbonate produced by the decarboxylation of a-lcetoglutarate in the citric acid cycle can also serve as a buffer in blood plasma. Taken together, these effects of glutamine metabolism in the kidney tend to counteract acidosis. ... 

The pH of blood plasma is 7.40. Assuming the principal buffer system is HC0 /H2C03, calculate the ratio [HC0J]/[H2C03]. Is this buffer more effective against an added acid or an added base ... 

In animals with lungs, the bicarbonate buffer system is an effective physiological buffer near pH 7.4, because the H2CO3 of blood plasma is in equilibrium with a large reserve capacity of C02(g) in the air space of the lungs. This buffer system involves three reversible equilibria between gaseous CO2 in the lungs and bicarbonate (HCOs ) in the blood plasma (Fig. 1). 

We begin with some comments on the various experimental methods used in our studies. Investigations of single proteins in buffer are then discussed, including kinetics and isotherms, reversibility, denaturation, and the structural status of adsorbed proteins. Results of competitive adsorption studies using mixtures of proteins in buffer are then described. We next discuss our more recent studies of protein adsorption from blood plasma using both radiolabeled proteins and elution techniques. Finally, data on the effect of red blood cells on protein adsorption are summarized. 

Medical Uses. Citric acid and citrate salts are used to buffer a wide range of pharmaceuticals at their optimum pH for stabiUty and effectiveness (65—74). Effervescent formulations use citric acid and bicarbonate to provide rapid dissolution of active ingredients and improve palatabiUty. Citrates are used to chelate trace metal ions, preventing degradation of ingredients. Citrates are used to prevent the coagulation of both human and animal blood in plasma and blood fractionation. Calcium and ferric ammonium citrates are used in mineral supplements. 

Osmotic lysis The plasma membranes of cells are water-permeable but are impermeable to large molecules and some ions. Thus, if cells are placed into water or dilute buffer, they swell owing to the osmotically driven influx of water. Since the plasma membrane is not able to stretch very much (the red blood cell membrane can stretch only up to 15 percent of its normal area before disruption), the cells burst. The method is effective for isolated cells but is not so effective for tissues. 

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