Calcium phosphate adsorption and

The first demonstration of transhydrogenase activity in Pseudomonas fluoreacens by Colowick et al. (1) was carried out with a crude extract obtained from cells grown on citrate as the sole carbon source. This extract could be fractionated further by acetone precipitation followed by calcium phosphate adsorption and subsequent elution with potassium phosphate. A second acetone fractionation and calcium phosphate adsorption gave a total purification of about 200-fold. This preparation was devoid of dehydrogenase activity using glutamate, isocitrate, lactate,... 

Adsorptive Properties. Under certain conditions of pH and low ionic strength, certain proteins will be adsorbed by various substances. Calcium phosphate gel and alumina Cy gel, for example, are frequently used to adsorb specific proteins from heterogeneous mixtures. The adsorbed proteins can frequently be released from the insoluble support either by altering the pH or increasing the ionic strength. Thus, purification can be obtained by removing either the extraneous unwanted proteins or the desired protein with the gel. 

Wang et al. 146) reported in 1956 the isolation of succinate dehydrogenase from heart muscle preparations treated with succinate and cyanide. The enzyme was extracted with 20% aqueous ethanol at pH 9.0. The final product, after adsorption on calcium phosphate gel and ammonium sulfate fractionation, was stated to be electrophoretically homogeneous and to contain 1 mole of flavin and 4 g-atoms of iron per 140,000-... 

FTIR spectroscopy has proven to be particularly useful in gaining an understanding of the biocompatibility phenomenon. It is believed [746, 841, 856, 857] that protein adsorption is the initial step in the interaction of blood with implanted biomaterials, followed by adhesion of cells and subsequent tissue attachment. This implies that the substrate surface characteristics influence the process, which was confirmed by ATR studies of albumin adsorption on calcium phosphate bioceramics and titanium [763] and segmented polyurethane [764], albumin and fibrinogen on acetylated and unmodified cellulose [765, 766], poly(acrylic acid)-mucin bioadhesion [767], polyurethane-blood contact surfaces [768], and other proteins on poly(ester)urethane [769], polystyrene [767, 771] and poly(octadecyl methacrylate) [771] and by IRRAS study of adsorption of proteins on Cu [858]. Another branch of IR spectroscopic studies of protein adsorption relates to microbial adhesion (Section 7.8.3). 

An enzyme catalyzing the formation of CHjOH-FH4 has been observed in pigeon liver 53). This enzjune was partially purified from acetone powder extracts by adsorption and elution from calcium phosphate gel, and by salting-out at 55-75 % saturation of (NH4)2S04. The assay of this enzyme could be performed by a shift in the ultraviolet absorption of FH4 (Xm x = 298 m/i) to that of the formaldehyde adduct (X uix = 290 nut). Osborn et al. 63) report that only a single product is formed by the enzymic reaction. Blakley found a change in the absorption maximum from 298 m/t to 294 m/t on the mere addition of formaldehyde (10 M) to FH4. 

Graded Adsorbents and Solvents. Materials used in columns for adsorption chromatography are grouped in Table 12 in an approximate order of effectiveness. Other adsorbents sometimes used include barium carbonate, calcium sulfate, calcium phosphate, charcoal (usually mixed with Kieselguhr or other form of diatomaceous earth, for example, the filter aid Celite) and cellulose. The alumina can be prepared in several grades of activity (see below). 

Adsorption. The adsorption of the components of a vaccine on to a mineral adjuvant. The mineral adjuvants, or carriers, most often used are aluminium lydroxide, aluminium phosphate and calcium phosphate and their effect is to increase the immunogenieity and decrease the toxicity, local and systemic, of a vaccine. Diphtheria vaccine, tetanus vaccine, diphtheria/tetanus vaccine and diphtheriaAetanus/pertussis vaccine are generally prepared as adsorbed vaccines. 

Adsorption on calcium pectate and calcium phosphate, and chromatography on DEAE-cellulose, were used for the purification of pectin lyase from Aspergillus fonsecaeus.253 Two forms of pectin lyase (having pH optima at 7.3 and 8.3) were isolated266 from the culture filtrate of Sclerotinia fructigena by chromatography on Seph-adex G-75 and CM-Sephadex C-50. 

Precipitation can occur if a water is supersaturated with respect to a solid phase however, if the growth of a thermodynamically stable phase is slow, a metastable phase may form. Disordered, amorphous phases such as ferric hydroxide, aluminum hydroxide, and allophane are thermodynamically unstable with respect to crystalline phases nonetheless, these disordered phases are frequently found in nature. The rates of crystallization of these phases are strongly controlled by the presence of adsorbed ions on the surfaces of precipitates (99). Zawacki et al. (Chapter 32) present evidence that adsorption of alkaline earth ions greatly influences the formation and growth of calcium phosphates. While hydroxyapatite was the thermodynamically stable phase under the conditions studied by these authors, it is shown that several different metastable phases may form, depending upon the degree of supersaturation and the initiating surface phase. 

Humic substances. Analogous to the reactions described above, humic substances (the polymeric pigments from soil (humus) and marine sediments) can be formed by both enzymatic and non-enzymatic browning. High concentrations of free calcium and phosphate ions and supersaturation with respect to hydroxyapatite can sustain in soil, because adsorption of humic acids to mineral surfaces inhibits crystal growth (Inskeep and Silvertooth, 1988). A similar adsorption to tooth mineral in a caries lesion can be anticipated for polycarboxylic polymers from either the Maillard reaction or enzymatic browning. 

When particles or large molecules make contact with water or an aqueous solution, the polarity of the solvent promotes the formation of an electrically charged interface. The accumulation of charge can result from at least three mechanisms (a) ionization of acid and/or base groups on the particle s surface (b) the adsorption of anions, cations, ampholytes, and/or protons and (c) dissolution of ion-pairs that are discrete subunits of the crystalline particle, such as calcium-oxalate and calcium-phosphate complexes that are building blocks of kidney stone and bone crystal, respectively. The electric charging of the surface also influences how other solutes, ions, and water molecules are attracted to that surface. These interactions and the random thermal motion of ionic and polar solvent molecules establishes a diffuse part of what is termed the electric double layer, with the surface being the other part of this double layer. 

Again, there are several choices of extractant, and the preferred one depends mainly on the type of soil under test. One of the most widely used procedures is the Olsen method (Olsen ef al., 1954), which was developed in the USA to correlate crop response to fertilizer on calcareous soils. The amount of P extracted will vary with temperature (increases by 0.43 mg P kg- per degree rise between 20°C and 30°C) and shaking speed, so conditions should be standardized. The extractant is 0.5 M sodium bicarbonate adjusted to pH 8.5. The bicarbonate competes with phosphate on the adsorption sites extracts, and removes most, but not all of it, together with some soluble calcium phosphate. Addition of phosphate-free activated carbon before shaking is necessary if coloured soil extracts are obtained, and then they will require filtration. 

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