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PubMed2001

[Adsorptive voltammetric behavior of omeprazole and its application].

AIM: To study the electrochemical behavior of omeprazole (OPZ) and a new method for the determination of the compound was established by adsorptive stripping voltammetry. METHODS: Linear-sweep polarography and cyclic voltammetry were used. RESULTS: In a supporting electrolyte containing 0.1 mol.L-1 NH3-NH4Cl, a reduction peak of OPZ was observed by linear-sweep voltammetry at Hg electrode. The peak showed a potential of -1.04 V (vs Ag/AgCl at 100 mV.s-1) and adsorptive characteristics. The adsorbed species is most probably the neutral molecular of OPZ. The saturated adsorption of OPZ at Hg electrode is 9.55 x 10(-11) mol.cm-2 and every OPZ molecule occupies and area of 1.74 nm2. On the surface of the hanging mercury drop electrode, the adsorption of OPZ obeys Frumkin adsorption isotherm. The adsorption coefficient beta is 1.32 x 10(6), the Gibbs energy of adsorption delta G theta is -34.93 kJ.mol-1, the number of electrons transferred n is 4, the kinetics parameter alpha n alpha is 0.78, the rate constant of the surface electrode reaction ks is 0.18 s-1, the diffusion coefficient D of OPZ in solution is 1.03 x 10(-5) cm2.s-1. The detection limit of the adsorptive stripping voltammetry of OPZ is 2.0 x 10(-9) mol.L-1 under optimized condition. CONCLUSION: This indicates an irreversible process with adsorption.

Anti-Ulcer Agents↗

PubMed1996

Plasma protein adsorption to sulfonated poly(ethylene oxide)-grafted polyurethane surface.

Adsorption of proteins (fibrinogen, albumin, and gamma globulin) from plasma onto surface-modified PUs (PU-PEO, PU-SO3, and PU-PEO-SO3) was evaluated. Adsorbed fibrinogen at steady state decreased in the order PU-SO3 > PU > PU-PEO-SO3 > PU-PEO, suggesting that sulfonate groups have specific high affinity to fibrinogen. The intermediate fibrinogen adsorption on PU-PEO-SO3 can be explained by the compensatory effect between the low protein binding affinity of the PEO chain and the high fibrinogen binding affinity of the sulfonate group. In addition, PU-PEO-SO3 showed a very fast fibrinogen adsorption due to the high accessibility of the sulfonate group to fibrinogen by the poly(ethylene oxide) (PEO) spacer. The kinetic profiles of their surfaces showed that as the adsorption time increases, fibrinogen initially adsorbed was decreased and a plateau reached, demonstrating that all the surfaces exhibited the Vroman effect (the fibrinogen displacement phenomenon). PU-PEO showed the least fibrinogen and albumin adsorption among PUs, confirming the known nonadhesive property of PEO chains. It is very interesting that PU-PEO-SO3 exhibited the highest adsorption of albumin and the lowest adsorption of IgG. Therefore, it may be concluded that such adsorption behaviors of proteins to PU-PEO-SO3 contribute to improved blood compatibility.

Adsorption↗

PubMed2000

Determination of apparent thermodynamic parameters for adsorption of a midchain peptidyl residue onto a glass surface.

Protein adsorption onto the surface of an implanted material is widely recognized as an important factor controlling the biological response. Although numerous studies have been conducted to investigate protein adsorption behavior, very little is actually understood regarding the specific molecular events involved in protein-surface adsorption processes. As a basic science approach to investigate protein-surface interactions, an experimental method is developed and applied to determine apparent thermodynamic parameters for the adsorption of a single midchain peptidyl residue onto a glass surface. This article presents the results of adsorption studies for four molecular weight ranges of poly-L-lysine onto glass microspheres in physiologic saline at four temperatures. Isotherm data plots are constructed and the apparent changes in enthalpy (DeltaH degrees ), entropy (DeltaS degrees ), and Gibbs' free energy (DeltaG degrees ) are calculated assuming a Langmuir-like model for adsorption. Estimates of apparent DeltaH degrees, DeltaS degrees, and DeltaG degrees for the adsorption of a single midchain lysine residue are determined from the initial slopes of the plots of the apparent thermodynamic parameters versus the degree of polymerization of the adsorbed poly-L-lysine. It is proposed that the generation of such molecular-level adsorption data is a necessary step toward the goal of understanding, predicting, and controlling protein-surface interactions.

Adsorption↗

PubMedDate not supplied

Human low density lipoprotein and human serum albumin adsorption onto model surfaces studied by total internal reflection fluorescence and scanning force microscopy.

The adsorption of low density lipoprotein (LDL) and human serum albumin (HSA) to model surfaces of different hydrophobicities has been studied using two, surface-sensitive, real-time, in situ techniques: total internal reflection fluorescence (TIRF) and scanning force microscopy (SFM). The model surfaces used were: (1) hydrophilic negatively charged silica (TIRF) and mica (SFM) surfaces, (2) hydrophobic octadecyldimethylsilyl-(ODS)-modified silica (TIRF) and ODS-modified oxidized silicon (SFM) surfaces and (3) amphiphilic ODS-silica gradient surfaces (TIRF). The kinetics of fluorescein isothiocyanate-LDL adsorption onto the ODS-silica gradient surface from FITC-LDL solution and from a solution mixture of LDL and HSA showed that a transport-limited process on the clean silica changed into an adsorption-limited process with increasing surface coverage of ODS chains. SFM analysis of the in situ adsorption of LDL on hydrophilic mica demonstrated a steady increase in surface coverage with time which was somewhat lower than determined by TIRF for FITC-LDL adsorption on silica. The adsorption behavior of a binary mixture of HSA and LDL suggested that lateral interactions between HSA and LDL affect the adsorption process. The diameter of LDL adsorbed on mica and ODS-modified silicon has been determined using SFM to be approximately 55 nm. Tetrameric LDL aggregates were observed on all of the surfaces in addition to some dimers and trimers. Imaging LDL and HSA adsorption on clean oxidized silicon surfaces using "contact mode' SFM techniques was hindered by probe manipulation of the proteins.

Adsorption↗

PubMed2005

Protein adsorption in fused-silica and polyacrylamide-coated capillaries.

The model proteins cytochrome c, myoglobin, ovalbumin, and beta-lactoglobulin were investigated with regard to their adsorption properties on capillaries for electrophoresis. The model compounds were selected to cover a wide range of properties. Cytochrome c is a basic protein (isoelectric point (pI): 9.6; M(r): 11.7 kDa), beta-lactoglobulin is rather acidic (pI: 5.4, M(r): 18.4 kDa), myoglobin was chosen as a neutral reference protein (pI: 6.8-7.4, M(r): 17.8 kDa), and ovalbumin (pI: 5.1, M(r): 45.0 kDa) was selected as a relatively larger analyte. First, the pH dependence of adsorption was investigated for the bare fused silica. A clear correlation to the respective pIs was noted. For myoglobin and ovalbumin, none or negligible adsorption was found above the pI, whereas strong adsorption was noted just below this parameter. Cytochrome c and beta-lactoglobulin already showed distinct adsorption above their pIs. However, none of the proteins showed any significant adsorption more than one pH unit above the pIs. For linear polyacrylamide-coated capillaries, a decreased but not a complete lack of adsorption was observed. Here, pH-dependent adsorption was noted as well. Regeneration of the capillaries by rinsing with buffers containing 200 mM SDS was also investigated. This method was completely successful for myoglobin, but that too for only freshly-adsorbed protein. After a storage time of 24 h and due to the aging of the adsorbate, a sufficient regeneration was no longer possible.

Adsorption↗

PubMed1987

Adsorption of low density lipoproteins onto selected biomedical polymers.

This study examines the interaction of human low density lipoprotein (LDL) with a select group of biomedical polymers. The adsorption characteristics of LDL on cured filler-free poly(dimethyl Siloxane) (C-PDMS), Biomer, Cardiomat 610, Kraton 1650, poly(hydroxyethyl methacrylate) (PHEMA) and glass are presented. Adsorption of LDL to charged hydrophilic glass control surfaces occurred rapidly, reaching plateau concentrations within one minute (0.19 +/- 0.01 ug/cm2). Adsorption of LDL to polymer surfaces appeared to be dependent upon both the polymer hydrophobicity (or apolar nature), and flexibility (or dynamic nature) at the interface. Increased surface concentrations were observed for Biomer (0.32 +/- 0.01 ug/cm2) as well as other polymers which exhibited both hydrophobic and elastomeric properties. Temperature changes between 25 degrees C and 37 degrees C were found to significantly influence the surface concentration of LDL on Biomer (0.16 +/- 0.01 ug/cm2 at 25 degrees C versus 0.32 +/- 0.01 ug/cm2 at 37 degrees C). A lipid core phase transition at 36 degrees C was believed to be responsible for the temperature influence. Preliminary competitive adsorption studies of LDL with albumin (HSA) and serum on silicone surfaces suggests that LDL adsorption occurred rapidly and preferentially (0.25 +/- 0.01 ug/cm2 for LDL alone; 0.33 +/- 0.01 ug/cm2 for LDL + HSA; 0.15 +/- 0.01 ug/cm2 LDL + serum). Preliminary studies on the role of LDL in calcification were not conclusive. It can be concluded that LDL adsorption is dependent upon polymer hydrophobicity, flexibility and temperature. Competitive adsorption experiments suggests that LDL may have a substantial influence on protein adsorption.

Adsorption↗

PubMed1991

Protein adsorption to poly(ethylene oxide) surfaces.

Surfaces containing poly(ethylene oxide) (PEO) are interesting biomaterials because they exhibit low degrees of protein adsorption and cell adhesion. In this study different molecular weight PEO molecules were covalently attached to poly(ethylene terephthalate) (PET) films using cyanuric chloride chemistry. Prior to the PEO immobilization, amino groups were introduced onto the PET films by exposing them to an allylamine plasma glow discharge. The amino groups on the PET film were next activated with cyanuric chloride and then reacted with bis-amino PEO. The samples were characterized by scanning electron microscopy, water contact angle measurements, gravimetric analysis, and electron spectroscopy for chemical analysis (ESCA). The adsorption of 125I-labeled baboon fibrinogen and bovine serum albumin was studied from buffer solutions. Gravimetric analysis indicated that the films grafted with the low-molecular-weight PEO contained many more PEO molecules than the surfaces grafted with higher-molecular-weight PEO. The high-molecular-weight PEO surfaces, however, exhibited greater wettability (lower water contact angles) and less protein adsorption than the low-molecular-weight PEO surfaces. Adsorption of albumin and fibrinogen to the PEO surfaces decreased with increasing PEO molecular weight up to 3500. A further increase in molecular weight resulted in only slight decreases in protein adsorption. Protein adsorption studies as a function of buffer ionic strength suggest that there may be an ionic interaction between the protein and the allylamine surface. The trends in protein adsorption together with the water contact angle results and the gravimetric analysis suggest that a kind of "cooperative" water structuring around the larger PEO molecules may create an "excluded volume" of the hydrated polymer coils. This may be an important factor contributing to the observed low protein adsorption behavior.

Adsorption↗

PubMed2007

Protein adsorption onto polyester surfaces: is there a need for surface activation?

Surface hydrolysis of polyester scaffolds is a convenient technique suggested to promote protein adsorption for improving cell attachment. We have, therefore, investigated the effect of hydrolysis of polyester surfaces for protein adsorption to clarify the conditions needed. Three polyesters, poly(ethylene terephthalate) (PET), poly(lactic acid) (PLA), and poly(glycolic acid) (PGA), were selected. Adsorption was investigated by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and quartz crystal microbalance (QCM). Hydrolyzed PET adsorbed significantly more proteins than nonhydrolyzed. Degradable polymers adsorbed at higher rates when the polymers were hydrolyzed prior to adsorption, but the same amount as nonhydrolyzed, suggesting spontaneous hydrolysis during the adsorption. XPS shows that hydrolysis prior to absorption for PET results in a surface nitrogen composition of approximately 14%, similar to pure protein (16%). Nonhydrolyzed PET surfaces showed only approximately 7% nitrogen, indicating protein layers thinner than approximately 10 nm. Adsorption to PLA and PGA shows nitrogen contents of 14-15% in both cases. SEM revealed striking differences in morphology of the protein coating. Hydrolyzed or spontaneously hydrolyzable surfaces display a pronounced fibrous structure while nonhydrolyzed surfaces give smooth structures. In combination, the results show that surface hydrolysis increase adsorption rate, but not the amount of proteins on polyesters that degrades in vivo. Surface treatment of nondegradable polyester increases the total amount of proteins and induces the formation of fibrous protein structures. Post hydrolysis treatment by acetic acid, replacing the counter-ion to a proton, further enhances protein attachment. Finally, cell attachment experiments verifies that protein adsorption increase the cell attachment to polyester surfaces.

3T3 Cells↗

PubMed2005

Adsorption kinetics and thermodynamics of acid dyes on a carboxymethylated chitosan-conjugated magnetic nano-adsorbent.

The monodisperse chitosan-conjugated Fe(3)O(4) nanoparticles with a mean diameter of 13.5 nm were fabricated by the carboxymethylation of chitosan and its covalent binding onto Fe(3)O(4) nanoparticles via carbodiimide activation. The carboxymethylated chitosan (CMCH)-conjugated Fe(3)O(4) nanoparticles with about 4.92 wt.-% of CMCH had an isoelectric point of 5.95 and were shown to be quite efficient as anionic magnetic nano-adsorbent for the removal of acid dyes. Both the adsorption capacities of crocein orange G (AO12) and acid green 25 (AG25), as the model compounds, decreased with increasing pH, and the decreasing effect was more significant for AO12. On the contrary, the increase in the ionic strength decreased the adsorption capacity of AG25 but did not affect, obviously, the adsorption capacity of AO12. By the addition of NaCl and NaOH, both AO12 and AG25 could desorb and their different desorption behavior could be attributed to the combined effect of pH and ionic strength. From the adsorption kinetics and thermodynamics studies, it was found that both the adsorption processes of AO12 and AG25 obeyed the pseudo-second-order kinetic model, Langmuir isotherm, and might be surface reaction-controlled. Furthermore, the time required to reach the equilibrium for each one was significantly shorter than those using the micro-sized adsorbents due to the large available surface area. Also, based on the weight of chitosan, the maximum adsorption capacities were 1 883 and 1 471 mg x g(-1) for AO12 and AG25, respectively, much higher than the reported data. Thus, the anionic magnetic nano-adsorbent could not only be magnetically manipulated but also possessed the advantages of fast adsorption rate and high adsorption capacity. This could be useful in the fields of separation and magnetic carriers. [formula in text].

Acids↗

PubMed2001

Adsorption-desorption behaviour of flufenacet in five different soils of India.

Adsorption-desorption of the herbicide flufenacet (FOE 5043) has been studied in five soils from different locations in India (Delhi, Ranchi, Nagpur, Kerala and Assam) varying in their physicochemical properties. The organic matter (OM) content varied from 0.072 to 0.864%, clay content from 2.5 to 43.7% and pH from 4.45 to 8.35. The adsorption studies were carried out using a batch equilibration technique. Ten grams of soil were equilibrated with 20 ml of aqueous 0.01 M CaCl2 solution containing different concentrations (0-30 mg litre-1) of flufenacet. After equilibration, an aliquot of supernatant was taken out for analysis. During desorption, the amount withdrawn for analysis was replenished with fresh 0.01 M CaCl2 solution and further equilibrated. Desorption studies were carried out with the 30 mg litre-1 concentration of flufenacet only. The adsorption studies revealed that there was moderate to high adsorption of flufenacet considering the comparatively low organic carbon content in the five test soils. Average Kd values ranged from 0.77 to 4.52 and Freundlich KF values from 0.76 to 4.39. The highest adsorption was observed in Kerala soil (OM 0.786%; clay 25%; pH 4.45) followed by Ranchi, Nagpur and Delhi soils, and the lowest in Assam soil (OM 0.553%; clay 2.5%; pH 6.87). The trend in adsorption could be attributed to the chemical nature of flufenacet and the physicochemical properties of the soil such as pH, OM and clay contents. OM and clay contents were positively correlated whereas pH was negatively correlated. Soils having low pH, high OM and high clay contents showed higher adsorption. Desorption studies revealed that there was a hysteresis effect in all the soils. Hysteresis coefficient values (ratio of n(ad) and n(des)) varied from 0.09 to 0.45. The study implies that, because of its moderate to high adsorption, flufenacet is likely to persist in soil for some time. However, the possibility of its movement by leaching or surface run off is less.

Acetamides↗

PubMed1993

Transcytosis of protein through the mammalian cerebral epithelium and endothelium. II. Adsorptive transcytosis of WGA-HRP and the blood-brain and brain-blood barriers.

Morphological evidence of the potential for adsorptive transcytosis of protein through the mammalian blood-brain fluid barriers, first reported from this laboratory in the mouse, has been confirmed and expanded upon in rats injected intravenously or into the lateral cerebral ventricle/subarachnoid space with with exogenous lectin wheatgerm agglutinin (WGA) conjugated to horseradish peroxidase (HRP). Blood-borne WGA-HRP rapidly enters cerebral endothelia by the process of adsorptive endocytosis and labels the vascular tree throughout the CNS. At 3 h post-injection and longer, WGA-HRP occupies the perivascular clefts and labels perivascular cells and basal lamina; this suspected transendothelial transfer of the lectin conjugate from blood to brain involves specific constituents of the endothelial endomembrane system of organelles (e.g., plasmalemma, vesicles, endosomes, Golgi complex). Within 6 h, reaction product is evident in extracellular clefts beyond the perivascular basal lamina and labels endocytic vesicles, endosomes, and dense bodies within cells and processes of the neuropil. Exposure of the abluminal surface of blood-brain barrier endothelia for 1-18 h to WGA-HRP delivered into the cerebral ventricles or subarachnoid space indicates blood-brain barrier endothelia do not engage in demonstrable adsorptive endocytosis at the abluminal surface. In this preparation, no endothelial organelles comparable to those sequestering blood-borne WGA-HRP are labelled with the lectin conjugate; hence, significant adsorptive transcytosis of WGA-HRP through cerebral endothelia from brain to blood is unlikely. The demonstrable difference in membrane internalization of the luminal versus abluminal plasmalemma of blood-brain barrier endothelia suggests the blood-brain barrier is polarized regarding adsorptive endocytosis of WGA-HRP. If adsorptive transcytosis of macromolecules through the blood-brain barrier does occur, the process appears unidirectional, from blood to brain but not from brain to blood. Absence of demonstrable endocytosis at the abluminal front is an enigma in the scheme of transcytosis through the blood-brain barrier from blood to brain insofar as exocytosis and endocytosis are complementary events in the cellular secretory process. This unconventional membrane behavior associated with the abluminal plasmalemma argues against a significant transcytosis of blood-borne protein through blood-brain barrier endothelia. The potential for transcytosis of macromolecules through the blood-cerebrospinal fluid barrier of choroid plexus epithelia is not as problemmatic as that through blood-brain barrier endothelia; additional evidence is provided to suggest choroid plexus epithelia participate in adsorptive endocytosis circumferentially and adsorptive transcytosis of WGA-HRP bidirectionally between the blood and cerebrospinal fluid.

Adsorption↗

PubMed1990

Adsorption of 5'-adenosine monophosphate onto precipitated calcium phosphate: effects of inorganic polyphosphates and carbamyl phosphate.

In this paper it is shown that the adsorption of 5'-adenosine monophosphate (5'-AMP) onto precipitated calcium phosphate exhibits a sigmoidal profile as revealed by isotherms at 45 degrees C. This result indicates a cooperative behavior in the adsorption of 5'-AMP. The relationship between adsorption capacity and surface area of the sedimented matrix may be interpreted as an indication that there is a monolayer of the absorbed nucleotide on the solid surface. The pH dependence of adsorption suggests that the negatively charged phosphoryl group of 5'-AMP interacts with a positively charged site (possibly Ca2+) on the matrix surface. The adsorption of the nucleotide is markedly decreased at pH values above 8.0. The Dixon-like plot of the effect of pH suggests an inhibitory role of hydroxyl ions in the adsorption of 5'-AMP. At pH 7.5, other anions such as pyrophosphate, tripolyphosphate and carbamyl phosphate also inhibit the adsorption of the nucleotide, probably by interacting with its adsorption site. We suggest that these phosphorylated molecules could have played a role in chemical evolution by modulating the amount of nucleotides adsorbed onto mineral surfaces. The significance of these phenomena in chemical evolution is discussed.

Adenosine Monophosphate↗

PubMed1987

Soluble minerals in chemical evolution. II. Characterization of the adsorption of 5'-AMP and 5'-CMP on a variety of soluble mineral salts.

The adsorption of 5'-AMP and 5'-CMP was studied in saturated solutions of several soluble mineral salts (NaCl, Na2SO4, MgCl2 X 6H2O, MgSO4 X 7H2O, CaCl2 X 2H2O, CaSO4 X 2H2O, SrCl2 X 6H2O, SrSO4, and ZnSO4 X 7H2O) as a function of pH, ionic strength, and surface area of the solid salt. The adsorption shows a pH dependence; this can be correlated with the charge on the nucleotide molecule which is determined by the state of protonation of the N-1 nitrogen of 5'-AMP or N-3 nitrogen of 5'-CMP and the phosphate oxygens. The adsorption which results from the binding between the nucleotide molecule and the salt surface is proposed as being due to electrostatic forces. It was concluded that the adsorption was reversible in nature. The adsorption shows a strong dependence upon ionic strength and decreases with increasing ionic strength. Surface area is shown to be an important factor in evaluating and comparing the magnitude of adsorption of nucleotides onto various mineral salts. The implications of the results of the study are discussed in terms of the importance of soluble mineral salts as adsorption sites in the characterization of the adsorption reactions of an adsorbed template in biogeochemical cycles.

Adenosine Monophosphate↗

PubMed1983

Adsorption of sphingomyelinase of Bacillus cereus onto erythrocyte membranes.

Sphingomyelinase of Bacillus cereus proved to be specifically adsorbed onto mammalian erythrocyte membranes in the presence of either Ca2+ or Ca2+ plus Mg2+ in the order of sphingomyelin content; i.e., sheep, bovine greater than porcine greater than rat erythrocytes. No appreciable adsorption was observed in the presence of Mg2+ alone nor in the absence of divalent metal ions. The enzyme adsorption onto bovine erythrocytes was dependent upon the incubation temperature. By shifting the temperature from 37 to 0 degrees C, sphingomyelinase once adsorbed onto the surface of bovine erythrocytes was released into the supernatant. Ca2+ proved to be an essential factor for the enzyme adsorption: The addition of 1 mM Ca2+ enhanced the adsorptive process, but inhibited sphingomyelin hydrolysis and hot or hot-cold hemolysis of erythrocytes, while the addition of 1 mM Ca2+ plus 1 mM Mg2+ enhanced sphingomyelin breakdown and hemolysis as well as the enzyme adsorption. However, when the amount of sphingomyelin fell off to 0.2-0.7 nmol/ml or less by the action of sphingomyelinase, the enzyme once adsorbed was completely released from the surface of erythrocytes. The result indicates that the major binding site for sphingomyelinase is sphingomyelin. In the presence of 1 mM Mg2+ alone, the enzymatic hydrolysis of sphingomyelin and hemolysis proceeded whereas the enzyme adsorption was not encountered during 60 min incubation at 37 degrees C. The change in the molar ratio of Ca2+ to Mg2+ affected the enzyme adsorption and sphingomyelin breakdown; the higher Ca2+ enhanced the adsorption whereas the higher Mg2+ stimulated sphingomyelin hydrolysis.

Adsorption↗

PubMed1995

The effects of a soluble-fibre polysaccharide on the adsorption of carcinogens to insoluble dietary fibres.

Epidemiology and animal experiments indicate that dietary fibres protect against the development of colorectal cancer. However, insoluble dietary fibres appear to be more effective than soluble dietary fibres and one mechanism by which they may protect is by adsorbing dietary carcinogens. We found previously that the ability of a carcinogen to adsorb in vitro to alpha-cellulose (a model insoluble dietary fibre) was strongly related to the hydrophobicity of the carcinogen, measured as the calculated logarithm of the partition coefficient between 1-octanol and water (C log P). Furthermore, soluble dietary fibres (soluble-fibre polysaccharides), including gum arabic, reduced the adsorption of the hydrophobic carcinogen, DNP, to alpha-cellulose. In the present study we tested the ability of gum arabic to reduce the adsorption in vitro of the carcinogens BaP (C log P = 6.124), DNP (C log P = 4.384), and the heterocyclic amines, Trp-P-1 (C log P = 3.230) and MeIQx (C log P = 1.078). Gum arabic reduced the adsorption to alpha-cellulose of BaP and DNP, but not the adsorption of Trp-P-1 or MeIQx. Gum arabic also reduced the adsorption of BaP to an insoluble, dietary-fibre preparation from commercial cork which contains the hydrophobic component, suberin, but did not affect the adsorption of DNP, Trp-P-1 or MeIQx. It also did not affect the adsorption of DNP to an insoluble, dietary-fibre preparation from wheat straw, which contains the hydrophobic component, lignin. The results are discussed in terms of hydrophobic interactions between carcinogens and insoluble dietary fibres. In vivo, it is likely that soluble dietary fibres reduce the adsorption of only highly hydrophobic carcinogens to some insoluble dietary fibres.

1-Octanol↗

PubMed1992

Adsorption of plasminogen from plasma to lysine-derivatized polyurethane surfaces.

The adsorption of plasminogen, the principal protein of the fibrinolytic pathway in blood, to a number of solid surfaces from plasma was investigated. This study forms part of a larger project to develop a fibrinolytic surface for blood-contacting applications. Polyurethanes incorporating lysine residues were developed in an attempt to promote selective adsorption of plasminogen from plasma through lysine-binding sites in the plasminogen molecule. The adsorption of plasminogen to these surfaces as well as to glass, 'conventional' polyurethanes and precursor sulphonated polyurethanes was investigated. Adsorption from citrated human plasma diluted with isotonic Tris buffer (pH 7.4) was measured under static conditions at room temperature using radioiodinated plasminogen. The following trends were observed. (1) Adsorption increases monotonically with increasing plasma concentration and there is no suggestion of transient adsorption (Vroman effect) on any of the surfaces studied. (2) Sulphonate groups appear to have a strong effect on plasminogen adsorption as was found previously for adsorption from buffer. (3) The lysine-derivatized material having the highest lysine content may show a slight increase in plasminogen binding affinity compared to its sulphonated precursor.

Adsorption↗

PubMed1995

Contribution of electrostatic and hydrophobic interactions to the adsorption of proteins by aluminium-containing adjuvants.

The effect of ionic strength and ethylene glycol on the adsorption of bovine serum albumin (BSA) or lysozyme by a commercial aluminium hydroxide or aluminium phosphate adjuvant was studied at pH 7.4 and 25 degrees C. The adsorption of BSA by aluminium hydroxide adjuvant and lysozyme by aluminium phosphate adjuvant was found to be inversely related to ionic strength. This indicates that electrostatic attractive forces contribute to adsorption. The adsorption of lysozyme by aluminium phosphate adjuvant was reduced by the addition of ethylene glycol. However, no change in the adsorption of BSA by aluminium hydroxide adjuvant was noted when up to 40% ethylene glycol was present. This behaviour indicates that hydrophobic forces contribute to the adsorption of lysozyme but not of BSA. However, virtually no adsorption was observed when the protein and the adjuvant had the same surface charge. Thus, attractive forces may not be sufficient to produce adsorption of an antigen by an aluminium-containing adjuvant if electrostatic repulsive forces are present.

Adjuvants, Immunologic↗

PubMed2006

Adsorption behavior of strontium on binary mineral mixtures of montmorillonite and kaolinite.

The adsorption behavior of kaolinite and montmorillonite minerals and their mixtures in respect of Sr ion were studied by means of a batch method using (90)Sr as a radio tracer. The effect of several parameters such as temperature, pH, Sr concentration and supporting electrolyte were investigated. Experimentally measured distribution coefficients showed a good agreement to within 98.5-99.7% with theoretically calculated values. The values of adsorption capacity of adsorbents and mean adsorption energy of adsorption were calculated by fitting the adsorption data to Dubinin-Radushkevich isotherm. The adsorption capacity of clay mixtures decreased as kaolinite fractions increased. The mean adsorption energy values of 8.0-9.5 kJ mol(-1) showed that adsorption was governed by ion exchange. The Freundlich parameters were used to characterize a site distribution function for binary exchange between Sr and Na.

Adsorption↗