Buffers adsorption

Brockmann, H. and Schodder, H., Aluminum oxide with buffered adsorptive properties for purposes of chromatographic adsorption, Berl. Dtsch. Chem. Ges., 74B, 73, 1941. 

Fibrinogen adsorption from citrated blood plasma was in the order Silastic < poly(HEMA)/Silastic < poly(NVP)/Silastic. The different order from buffer adsorption may be due to lipoprotein adsorption from plasma to Silastic. 

Ion-retardation resins, which consist of acrylic acid polymerized inside a strong anion-exchange resin on a polystyrene divinylbenzene matrix [30], are also effective for removal of SDS from proteins. Passage of a protein-SDS complex through the resin results in complete retention of SDS and elution of protein with 80-90% recovery [31]. The capacity of the resin for SDS is more than 2.2mg/g, which effectively reduces the SDS level to less than one molecule of SDS per protein molecule. Because SDS binds tenaciously to the resin, it cannot be removed and the resin must be discarded after use. In the presence of buffers, adsorption of SDS by an ion-retardation column is reduced, resulting in incomplete removal of detergent from the protein. This can be circumvented by prior removal of buffer by SEC or, more conveniently, by the addition of a few grams of size exclusion gel to the head of the ion-retardation resin bed to retard the buffer [4]. 

In phosphate buffers, well-defined cyclic voltammetric waves due to the one-electron oxidation and reduction of adsorbed cytochrome c were observed. Peak areas were initially larger and the adsorbed protein remained electroactive longer for pH 8 phosphate buffers than for pH 6 buffers. Adsorption was also favored at lower ionic strength, at least in the case of pH 6. These effects of pH on apparent coverage parallel those... 

Adsorption of t-PA to process equipment surfaces consisting of either stainless steel or glass was minimized by adding the detergent polyoxyethylene sorbitan monooleate (Tween 80) to the semm-free culture conditioned media at 0.01% (vol/vol). The equipment was also rinsed, before use, with phosphate buffered saline (PBS) containing 0.01% Tween 80. Hydrophilic, plastic equipment was used whenever possible. AH buffers were sterile filtered. Sterile filtration of Hquids and gases is usually carried out using 0.2 or 0.45 p.m filters. 

L-pyrenyldiazomethane to form stable, highly fluorescent L-pyrenyhnethyl monoesters (87). These esters have been analy2ed in human blood by ce combined with lif detection. To mimini e solute adsorption to the capillary wall, they were coated with polyacrjiamide, and hydroxypropyl methylceUulose and dimethylfoTTnamide were used as buffer additives to achieve reflable separations. Separation was performed in tris-citrate buffer, pH 6.4, under reversed polarity conditions. The assay was linear for semm MMA concentrations in the range of 0.1—200 p.mol/L. 

Electrochemical reduction of iridium solutions in the presence azodye (acid chrome dark blue [ACDB]) on slowly dropping mercury electrode is accompanied by occurrence of additional peaks on background acetic-ammonium buffer solutions except for waves of reduction azodye. Potentials of these peaks are displaced to cathode region of the potential compared to the respective peaks of reduction of the azodye. The nature of reduction current in iridium solutions in the presence ACDB is diffusive with considerable adsorptive limitations. The method of voltamiuetric determination of iridium with ACDB has been developed (C 1-2 x 10 mol/L). 

For Yiv > YPv> where y v and Ypv are the surface tensions of liquid and protein, respectively, AFads increases with increasing ysv, predicting decreasing polymer adsorption. An example of this is phosphate buffer saline where y]v = 72.9 mJ/m2 and Ypv is usually between 65 and 70mJ/m2 for most proteins [5]. Therefore, supports for gel-permeation and affinity chromatography should be as hydrophilic as possible in order to minimize undesirable adsorption effects. 

In 1971, Hiatt et al. found that polyethylene oxide (PEO) of molecular weight about 100000 prevented the adsorption of rabies virus to porous glass with an average pore diameter of 1250 A. The support was modified by passage of one void volume of 0.4% solution of the polymer in water, followed by 5 or more volumes of distilled water or buffered salt solution. The virus was effectively purified from the admixtures of brain tissue fluid by means of size-exclusion chromatography on the modified glass column [28]. 

Fig. 17.5. Experimental configuration for integrated bead milling and fluidised bed adsorption 1. Feedstock 2. peristaltic pump 3. bead mill 4. flow through/waste 5. fluidised bed contactor 6. elution buffer 7. fraction collector/ waste 8. loading buffer.

The inhibition of Streptococcus mutans adherence to hydroxyapatite with combinations of alkyl phosphates and nonionic surfactants was tested. Seven alkyl phosphate derivatives and three nonionic surfactants were examined for their ability to inhibit the adherence of 3H-labeled cells of S. mutans to hydroxyapatite treated with buffer or parotid saliva. No compound by itself effectively hindered binding of bacteria to hydroxyapatite. A combination of certain of the alkyl phosphates, notably a disodium phosphate of 1-octadecanol, and nonionic surfactant at a 1 1 molar ratio gave a strong inhibition of S. mutans adherence. Treatment with this combination resulted in 98% reduction of adherence. Adsorption of the two types of surface-active agents alone and in combinations was studied using 14C-labeled agents. Electrophoretic measure-... 

Chen et al. utUized a direct chemical reaction with a given solution (wet treatment) to modify the surface of the silicone rubber. The presence of a layer of PEO on a biomaterial surface is accompanied by reductions in protein adsorption, and cell and bacterial adhesion. In order to obtain a PEO layer on top of the silicone rabber surface, the surface was firstly modihed by incorporating an Si-H bond using (MeHSiO) , and followed by PEO grafting to the surface using a platinum-catalyzed hydrosilylation reaction. These PEO-modified surfaces were demonstrated by fibrinogen adsorption both from buffer and plasma, as well as albumin adsorption from buffer. Reductions in protein adsorption of as much as 90% were noted on these surfaces. 

Figure 26 shows the redox potential of 40 monolayers of cytochrome P450scc on ITO glass plate in 0.1 KCl containing 10 mM phosphate buffer. It can be seen that when the cholesterol dissolved in X-triton 100 was added 50 pi at a time, the redox peaks were well distinguishable, and the cathodic peak at -90 mV was developed in addition to the anodic peak at 16 mV. When the potential was scanned from 400 to 400 mV, there could have been reaction of cholesterol. It is possible that the electrochemical process donated electrons to the cytochrome P450scc that reacted with the cholesterol. The kinetics of adsorption and the reduction process could have been the ion-diffusion-controlled process. 

Direct measurement of adsorptive stripping voltaimnetric peaks using HMDE 0.60 V and accumulation potential of -0.40V Dilution in phosphate buffer and water, analyzed in Vis region Ion pair formation with octadecyltrimethylammonium bromide at pH 5.6, extraction of ion pair into n-butanol Sample solution mixed with 1 M HCl, ethanol and purification on Sephadex DEAE 25 gel, gel beads are filtered off, packed into 1 nun cell and absorbance measured... 

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