Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “LACTOGLOBULINS”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,207 records · Page 67Linked to original sources
PubMed2006

Effect of HLA DQ2, dietary exposure and coeliac disease on the development of antibody response to gliadin in children.

OBJECTIVE: To study the effect of HLA DQ2, dietary history and development of coeliac disease (CD) on the induction of antibody response to wheat gliadin and cow's milk, beta-lactoglobulin between 1 and 2.5 years of age in children who developed CD and in healthy children. MATERIAL AND METHODS: Infants participating in a birth cohort study (the ABIS study) in Sweden were studied. Thirty-nine children developed CD (=cases), confirmed through biopsy, during follow-up until 2.5-5 years of age. A total of 181 healthy control children were matched for duration of exclusive breast-feeding, birth-weight, gender, maternal smoking and season of birth. IgG and IgA antigliadin and anti-beta-lactoglobulin antibodies were measured using enzyme immunoassay (EIA). The effects of HLA-risk genotypes, DQ2 and DQ8, on CD were also considered. RESULTS: Children who developed CD had higher IgG and IgA antigliadin and anti-beta-lactoglobulin antibody levels at 1 year of age than controls (all comparisons: p<0.001). Similar differences were seen between cases with as yet undiagnosed CD by 1 year of age and controls, and also when cases were compared with HLA-matched controls. Higher levels of IgG and IgA antibodies to beta-lactoglobulin (p=0.003; p=0.001), but not to gliadin, were found in treated cases versus controls at 2.5 years of age. HLA-DQ2-positive healthy children had lower levels of IgG and IgA antigliadin antibodies than HLA-DQ2 negative controls at 1 year of age (p=0.004; p=0.012). CONCLUSIONS: Enhanced humoral response emerging not only to gliadin, but also to other food antigens seems to be primarily associated with CD. Poor induction of antibody response to wheat gliadin in healthy children with the HLA-DQ2 risk molecule could at least partly explain the genetic predisposition to gluten intolerance and CD.

Age of Onset↗
PubMed1993

Colostrum protein digestion in newborn lambs.

The efficiency of colostral protein digestion was studied in nine newborn lambs fed one meal of bovine colostrum 3 h after birth. The results were compared with those obtained in two unfed lambs and four lambs fed bovine milk. The protein and peptide composition [immunoglobulins G1 and (IgG1), beta-lactoglobulin, alpha-lactalbumin, caseins and peptides resulting from casein hydrolysis] of digesta, gastrointestinal tissues, blood and urine were determined in samples taken 0.75 or 4 h after feeding. The amounts of ingested proteins in lambs fed colostrum were much higher than in those fed the milk diet, and their abomasal emptying was faster. alpha-Lactalbumin was highly degraded by abomasal and intestinal proteases, whereas beta-lactoglobulin and in particular the immunoglobulins were less sensitive. The gastric emptying of caseins was delayed in and the kinetics of appearance of peptides originating from casein hydrolysis was comparable to that observed in lambs fed milk and in 1-mo-old preruminant calves. Thirty-five percent of dietary amino acids ingested as colostrum were available within 4 h for amino acid metabolism; this percentage was 54% in the milk-fed lambs. In the lambs fed colostrum, these amino acids were provided by beta-lactoglobulin, casein and IgG1 (0.52, 0.43 and 0.30 g/kg body wt, respectively), whereas in milk-fed animals casein and beta-lactoglobulin were the most important sources of these amino acids (0.40 and 0.20 g/kg, respectively).

Abomasum↗
PubMed1991

Soluble interleukin-2 receptor levels in patients with dermatitis herpetiformis.

To determine the role of T-cell activation in dermatitis herpetiformis (DH), soluble IL-2R levels were measured by enzyme-linked immunosorbent assay (ELISA) in the sera of 30 patients with DH. Levels of this shed receptor are considered to be a measure of in vivo T-lymphocyte activation, and are elevated in the sera of many patients with inflammatory and immune-mediated diseases. Fifteen of the thirty (50%) patients with DH had elevated levels of soluble IL-2R compared to one of 31 (3%) healthy HLA-B8 or HLA-DR3 control subjects (p less than 0.00001) and one of 10 (10%) healthy non-HLA-B8/-DR3 subjects (p less than 0.0018). In addition, the mean soluble IL-2R level in the patients with DH (744 +/- 381 U/ml) was also significantly higher than that seen in 31 healthy HLA B8 or HLA DR3 individuals (388 +/- 160 U/ml, p = 0.0001) and 10 healthy non-HLA-B8/DR3 individuals (397 +/- 201 U/ml, p = 0.002). Only two of the 30 patients with DH had active skin lesions at the time of serum sampling, one of whom had elevated levels of IL-2R. Measurement of soluble IL-2R levels in sequential serum samples, available in four patients with DH at times of active and inactive skin disease, demonstrated a temporal association between soluble IL-2R level elevations and active skin disease in two patients and no association in two patients. In one patient a marked elevation in soluble IL-2R levels occurred with the onset of gastrointestinal symptoms, which decreased by 14% with institution of a gluten-free diet. In order to determine if soluble IL-2R levels are related to the mucosal immune response, the IL-2R levels were compared to the level of IgA antibodies directed against the dietary antigen beta-lactoglobulin. Ten of eleven (91%) patients with circulating IgA anti-beta lactoglobulin antibodies were also found to have elevated levels of IL-2R. In contrast, in the patients with no detectable IgA anti-beta lactoglobulin antibodies, only four of 16 (25%) had elevated levels of IL-2R (p = 0.001). Because IL-2R levels are not related to activity of the skin disease in patients with DH but are associated with the presence of IgA antibodies against the dietary antigen beta-lactoglobulin, these results suggest that some of the T-cell activation commonly present in DH reflects an ongoing immune response in the gastrointestinal tract.

Antibodies↗
PubMed1991

Molecular cloning of complementary DNAs for two human endometrial proteins and cellular localization of their messenger RNAs.

Insulin-like growth factor binding protein-1 (IGFBP-1) and a human beta-lactoglobulin homologue (beta LG/PP14) are two major secretory proteins of the human endometrium. The genes coding for these two proteins are expressed in separate types of the endometrial cells, with the IGFBP-1 gene being expressed in the stromal and the beta LG/PP14 gene in the glandular epithelial cells. Although the biological reasons for the presence and expression of IGFBP-1 and beta LG/PP14 in human endometrial cells remain to be elucidated, the fact that these gene products are expressed in different endometrial cell types provides a unique opportunity to employ them as markers in studies on epithelial-to-stromal cell communication in the endometrium. The primary structures of these proteins have been deduced from their cloned cDNAs. beta LG/PP14 is highly homologous to all known beta-lactoglobulins from various species. For example, horse beta-lactoglobulin I monomer exhibits a 53% protein sequence identity with beta LG/PP14; they have the same number of amino acid residues, and their three-dimensional structures are predicted to be similar. This latter conclusion is inferred from the fact that the four cysteinyl residues that are responsible for the formation of intramolecular bridges in beta-lactoglobulins are spatially conserved in beta LG/PP14. The human protein is encoded by a 900-base pair-long mRNA that is expressed in the glandular epithelial cells of the endometrium in a cyclic manner; in addition, it is found in the mucosal epithelial cells of the fallopian tubes. Several lines of circumstantial evidence suggest that the expression of the beta LG/PP14 gene is regulated by progesterone; however, whether this regulation is elicited by the progesterone receptor at the transcriptional level has not so far been demonstrated. The IGFBP-1 protein sequence contains 259 amino acid residues, with the propeptide possessing a 25-amino acid-long signal peptide. The NH2-terminal sequence of this and other IGFBPs is very cysteine-rich, suggesting the possibility that this domain is involved in the binding of IGF-I and IGF-II ligands. A PEST region, a sequence that is found in proteins with short intracellular half-lives, is included in the middle half of the IGFBP-1 polypeptide. Among the IGFBPs, IGFBP-1 appears to be the only one with a PEST sequence. The carboxy-terminal end of IGFBP-1 contains an Arg-Gly-Asp tripeptide that is also found in IGFBP-2 and may function as a cell attachment recognition signal in these proteins.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗
PubMed1994

Influence of preadsorbed milk proteins on adhesion of Listeria monocytogenes to hydrophobic and hydrophilic silica surfaces.

The adsorption of beta-lactoglobulin, bovine serum albumin, alpha-lactalbumin, and beta-casein for 8 h and beta-lactoglobulin and bovine serum albumin for 1 h at silanized silica surfaces of low and high hydrophobicity, followed by incubation in buffer and contact with Listeria monocytogenes, resulted in different numbers of cells adhered per unit of surface area. Adhesion to both surfaces was greatest when beta-lactoglobulin was present and was lowest when bovine serum albumin was present. Preadsorption of alpha-lactalbumin and beta-casein showed an intermediate effect on cell adhesion. Adsorption of beta-lactoglobulin for 1 h resulted in a generally lower number of cells adhered compared with the 8-h adsorption time, while the opposite result was observed with respect to bovine serum albumin. The adhesion data were explainable in terms of the relative rates of arrival to the surface and postadsorptive conformational change among the proteins, in addition to the extent of surface coverage in each case.

Adsorption↗
PubMed1983

Permeability of pancreatic capillaries to small molecules.

The permeability of capillaries in the isolated, blood-perfused canine pancreas was studied with the double-indicator dilution technique. The permeability-surface area products (PS) for inulin and beta-lactoglobulin A were determined at different plasma flows (attained by pump perfusion). The PS for inulin increased with increasing plasma flow, while the PS for beta-lactoglobulin A was relatively independent of plasma flow. At the highest plasma flow acquired, PS for inulin and beta-lactoglobulin A were approximately 23 and 3.5 ml X min-1 X 100 g-1, respectively. The ratio of the PS values for these two solutes was greater than the ratio of their free diffusion coefficients, indicating restricted diffusion of beta-lactoglobulin A relative to inulin. The degree of restriction was consistent with a maximum equivalent pore radius of 67 A for pancreatic capillaries. An ultrastructural analysis revealed that ductal as well as acinar and islet capillaries were fenestrated. The permeability characteristics of fenestrated pancreatic capillaries are similar to those previously reported for the small intestine.

Animals↗
PubMed1984

Immediate hypersensitivity reactions to cow milk proteins in isolated epithelium from ileum of milk-drinking guinea-pigs: comparisons with colonic epithelia.

The epithelium lining the ileum has been isolated and studied in vitro under short-circuit conditions. Tissues were obtained from guinea-pigs fed cow milk. When challenged with beta-lactoglobulin on either the apical or basolateral side, a transient, inward flowing current was recorded. This reaction did not occur with tissues from non-milk drinking animals. Casein and alpha-lactalbumin, in contrast to beta-lactoglobulin, produced only minor effects while bovine serum albumin and bovine gamma-globulin were without effect. The effect with beta-lactoglobulin was associated with overall fluid secretion in the basolateral to apical direction, although the ions responsible for carrying the current have not been identified. Possible mediators of the response to beta-lactoglobulin have been investigated. Throughout the responses of the ileum have been compared with those in the colon. The differences between the two tissues is striking. The relevance of the model to mechanisms of food intolerance is discussed.

Animals↗
PubMed1992

Induction of lactogenesis in transgenic virgin pigs: evidence for gene and integration site-specific hormonal regulation.

Five month-old transgenic female pigs from three lines carrying the mouse whey acidic protein (WAP) gene and nontransgenic female littermates were implanted with slow-release estrogen and progesterone pellets. Histological analysis of biopsies taken at the time of implantation and 4 weeks later revealed that mammary alveolar development had occurred upon hormonal stimulation in vivo. beta-Casein and beta-lactoglobulin mRNA was found in all induced animals, and WAP mRNA was detected in two of the three transgenic pigs. Differential hormonal regulation between the transgenes in the three lines and also between endogenous milk protein genes was observed in induced mammary tissue cultured in vitro. In the presence of insulin, hydrocortisone, and PRL, beta-casein and WAP mRNA levels increased in all transgenic pigs. In contrast, beta-lactoglobulin mRNA had reached or exceeded lactational levels in response to the in vivo induction, and no further increase was observed in vitro. This suggests that the regulation of the beta-lactoglobulin gene is distinct from that of beta-casein and WAP. Differences were also observed during pregnancy; whereas beta-lactoglobulin gene expression was induced in early pregnancy, a time when PRL levels are low, WAP mRNA levels increased sharply around parturition. Finally, the observation that hormonal regulation of WAP transgenes greatly differed between the three lines suggests that chromatin surrounding the integration site can modify the response of transcription elements.

Animals↗
PubMed1987

Association of milk protein types with growth and reproductive performance of dairy heifers.

A total of 890 heifers was used to study the effects of four milk protein loci (alpha S1-casein, beta-casein, kappa-casein, and beta-lactoglobulin) on heifer growth and reproduction. The additive effects of gene substitutions at the four milk protein loci were significant only in 4 of 56 cases for all traits studied. Dominance effects at alpha S1-casein, beta-casein, and kappa-casein loci were not significant for any traits except beta-casein locus on body weight at first calving. Heifers with AB type of beta-lactoglobulin showed greater body weights and measurements and gestation length than the AA or BB type, indicating an overdominance effect. Heifers with AB type of beta-lactoglobulin were significantly younger at first conception and at first freshening and had fewer number of days from first service to conception than the AA or BB type, indicating underdominance effect. Thus, beta-lactoglobulin locus shows overdominance, underdominance, or no dominance, depending upon the traits considered. The four milk protein loci contributed more dominance variance than additive variance to total phenotypic variance. This might account for the existence of milk protein polymorphism in the cattle population. The combined genotypes of the four milk protein loci showed significant effects on 2 of 14 traits studied.

Animals↗
PubMed2000

Effects of pH variation and NaCl on in vitro digestibility of cow's milk proteins in commercially available infant formulas.

Allergenicity and antigenicity of food proteins are generally dependent on their heat-stability and resistance to digestive enzymes. Using the methods of SDS-PAGE and immunoblots, we assessed peptic-digestibility of major milk proteins (casein, beta-lactoglobulin and alpha-lactalbumin) in commercially available infant formulas in acidic pH range (pH 1.5 to 4.0), and we also investigated the effect of NaCl on peptic-digestibility of cow's milk proteins at pH 2.0. The profile of peptic-digestion of casein was similar at pH range from 1.5 to 3.5 where the intact protein of casein rapidly disappeared, whereas slow digestibility of the protein was found at pH 4.0. Beta-lactoglobulin and alpha-lactalbumin were digested at pH range from 1.5 to 2.5 and were almost entirely resistant to peptic digestion at over pH 3.0. In the presence of NaCl at pH 2.0, casein showed a good digestibility by pepsin similar to that in the absence of NaCl, in contrast to beta-lactoglobulin and alpha-lactalbumin both having their peptic-digestibility decreased in the presence of 0.2 M NaCl. As the state of the stomach in new born infants shows low amounts of secretary pepsin and out of optimum pH of peptic activity, low digestibility of beta-lactoglobulin and alpha-lactalbumin in cow's milk based infant formulas at over pH 3.0 is supposed to be responsible for their allergenicity.

Animals↗
PubMed2001

Aroma compounds-proteins interaction using headspace techniques.

Interactions between volatile compounds and proteins in aqueous solution, were studied using static and dynamic headspace techniques. The decrease of aroma compounds concentration in the headspace determined in static mode indicates a retention by beta-lactoglobulin, 2.4% (w/w), pH 3.4, 25 degrees C, varying from 8 to 60% for most of the compounds tested. However 2-hexanone and isoamyl acetate are not significantly retained by the protein and a salting-out effect is noticed for limonene. On the basis of these preliminary results the intensity of interactions of methyl ketones (C7 to C9), ethyl esters (C6 to C9), limonene and mgamma rcene and beta-lactoglobulin for different pH values (2.0 to 11.0) were estimated by the determination of the infinite dilution activity coefficients (gamma i) by exponential dilution. For a constant pH value, the relative activity coefficient in the presence of beta-lactoglobulin (gamma r) of methyl ketones decreases significantly with the hydrophobicity of the volatiles whereas the relative activity coefficient value reaches a minimum for ethyl octanoate in the ester series. For limonene and myrcene an increase of gamma r is generally noticed whereas a decrease occurs in the presence of sodium caseinate and bovine serum albumin. The variations of relative activity coefficient according to the pH of the medium can be related to structural modifications of the beta-lactoglobulin.

Acyclic Monoterpenes↗
PubMedDate not supplied

Value of IgG4 antibodies against foods in atopic dermatitis.

Various authors have linked IgG4 antibodies to biological activities that are apparently contradictory in different studies. On one hand, it has been confirmed that during immunotherapy with inhalant and Hymenoptera venom antigens, an increase is produced in specific IgG4 levels. On the other hand, it has been suggested that these antibodies can intervene in hypersensitivity reactions, basically when these are directed against food antigens. We studied IgG4 levels against milk and egg fractions in patients with atopic dermatitis (AD) (n = 23), and in healthy individuals (n = 20). Patients with AD had significantly much higher IgG4 levels against egg white (24.16 micrograms/ml), egg yolk (9.96 micrograms/ml) and beta-lactoglobulin (10 micrograms/ml) than those found in healthy individuals (6.75, 3.12, 3.35 micrograms/ml, respectively), with no significant differences for alpha-lactalbumin and casein. Patients with AD without hypersensitivity to egg and milk, at the moment of the study, also had significantly higher levels than those of control individuals, against egg white (27.11 micrograms/ml), egg yolk (12 micrograms/ml) and beta-lactoglobulin (11.72 micrograms/ml). There were no differences in IgG4 levels against alpha-lactalbumin, beta-lactoglobulin and casein, when comparing patients with AD and hypersensitivity to milk, and patients with AD without present hypersensitivity to milk. We concluded that patients with AD presented high IgG4 levels against egg and milk fractions, in relation to the healthy population, and that the fraction of milk with the highest antigenic potency was beta-lactoglobulin.

Adolescent↗
PubMed1985

Lymphocyte response to a bovine milk protein in ulcerative colitis.

A recently described in vitro test for cow's milk protein hypersensitivity was applied to adult patients with ulcerative colitis. The test system involved the culture of their peripheral blood lymphocytes with and without beta-lactoglobulin, and the results were expressed as a stimulation index. Stimulation with beta-lactoglobulin was significantly higher (P less than 0.02) in patients with active disease than in those with inactive disease or in healthy controls. beta-Lactoglobulin was the only one of four cow's milk proteins that showed this effect. It is concluded that the cow's milk protein beta-lactoglobulin has a specific blastogenic effect on the lymphocytes of patients with active ulcerative colitis, and, therefore, may serve as a marker of disease activity.

Adolescent↗
PubMed1980

Heat denaturation of whey proteins. Comparative studies with physical and immunological methods.

Samples of a single batch of milk or whey were subjected to various heat treatment and the rates of denaturation of whey proteins (beta-lactoglobulin and alpha-lactalbumin) evaluated by both immunological (radial immunodiffusion using specific antisera) and physical methods (G 100 filtration chromatography and polyacrylamide gel electrophoresis) in order to assess the utility and limitation of these techniques, and to clarify some conflicting resulted previously published. G 100 chromatography and radial immunodiffusion give very good results but the latter is very less time consumming and more quantitative. Polyacrylamide gel electrophoresis must be discarded for quantitative purpose since beta-lactoglobulin B peak is heavily contaminated by polymers of beta-lactoglobulin A, and alpha-lactalbumin peak by polymers of beta-lactoglobulin A and B.

Animals↗
PubMed1990

Comparative studies of recycling isoelectric focusing and continuous flow electrophoresis: separation of proteins with minor charge differences.

Continuous flow zone electrophoresis (CFE) and recycling isoelectric focusing (RIEF) are two of the alternative formats for fluid phase preparative isolation of biological products in liquid separation media. The McDonnell Douglas CFE system has been used for both ground-based and microgravity separations. The ground-based McDonnell Douglas CFE and RIEF were compared for the ability to resolve mixtures of proteins with known charge differences. Mixtures of 1) cytochrome c, myoglobin, and ovalbumin or 2) beta-lactoglobulin and ovalbumin were used to evaluate the resolving capabilities of CFE and RIEF. Following separation, fractions were analyzed by determining absorbance at 280 nm and by analytical isoelectric focusing (IEF) using Coomassie Brilliant Blue or silver staining to detect focused proteins. Both CFE and RIEF apparently separated the components of both mixtures into individual peaks, separated by fractions which contained little or no detectable protein. Coomassie-stained analytical IEF gels supported this finding. However, when separated proteins were analyzed by silver staining of the analytical gels, the separation of ovalbumin from beta-lactoglobulin by CFE was not complete. Ovalbumin was free of beta-lactoglobulin but beta-lactoglobulin was contaminated by trace amounts of ovalbumin. RIEF clearly separated each protein with no detectable contamination. These data demonstrate the superiority of RIEF over CFE for resolution of protein mixtures having only minor charge differences. RIEF may be more efficient due to the documented electrodissociation of noncovalent protein:protein complexes which occurs during RIEF separations.

Cytochrome c Group↗
PubMed1997

Effect of milk fractions on survival of equine spermatozoa.

Milk-based semen diluents are known to be practical and effective in protecting equine spermatozoa during storage. Due to complex composition of milk, the components which are beneficial or harmful to spermatozoa are unknown. To address these unknowns the effect of various milk fractions on motility of stallion spermatozoa was evaluated. The fractions tested were native phosphocaseinate (NPPC), beta-casein, whey protein concentrate (WPC), alpha-lactalbumin, beta-lactoglobulin, microfiltrate, and ultrafiltrate. The standard reference diluents were INRA 82, commercial skim milk, and Hank's salts solution supplemented with Hepes, glucose, lactose (HGLL) supplemented with BSA. After 48 and 96 h storage at 4 or 15 degrees C some milk fractions (ultrafiltrate, microfiltrate, and alpha-lactalbumin fraction) decreased spermatozoal survival. Others (beta-lactoglobulin (BL) and native phosphocaseinate) were protective. Native phosphocaseinate (NPPC) at milk concentration afforted better protection than did the standard reference diluents. The optimal concentration of beta-lactoglobulin afforted significantly better protection than did BSA. The protection afforded by native phophocaseinate was not synergistic with beta-lactoglobulin. This implies a similar mechanism of protective action of these two components. Semen diluted in HGLL supplemented with NPPC (HGLL-NPPC) or in INRA 82 and stored 24 h at 15 degrees C or 4 degrees C, respectively, produced no difference of spermatozoal motility. However, fertility of semen stored in HGLL-NPPC (60%) was higher (p < 0.05) than that stored in INRA 82 (36%).

Journal Article↗
PubMed2004

[Stability of protein to digestion in vitro].

OBJECTIVE: To establish test model of stability of different protein to digestion in simulated gastric fluid (SGF) and simulated intestinal fluid (SIF). METHODS: The component of SGF and SIF being from the United States Pharmacopeia, the stability of various proteins were tested. The concentration of protein in SGF/SIF was 0.5mg/ml. At intervals of 0s, 15s, 30s, 60s, 2min, 4min, 8min, 15min, 30min and 60min, the samples were taken out. According to the results of SDS-PAGE, the stability of various proteins to digestion in SGF/SIF was observed. RESULTS: The experiment showed that trypsin inhibitor from soybean, beta-lactoglobulin A from bovine milk and beta-lactoglobulin B from bovine milk were stable within 60min in SGF. Peanut lectin was digested within 8min. Most soybean lectin was digested within 8min, but the degraded fragments still existed. Ovalbumin, ovomucoid, BSA, soybean lipoxygenase and potato acid phosphatase were digested within 15s. The results in SGF were not consistent with the results in SIF. Trypsin inhibitor from soybean, beta lactoglobulin A from bovine milk, beta-lactoglobulin B from bovine milk, BSA, ovalbumin, ovomucoid, soybean lectin and peanut lectin were stable for 60min in SIF. The degraded fragments of soybean lipoxygenase and potato acid phospatase exited within 60min. CONCLUSION: Different proteins showed different stability to SGF/SIF. According to the difference, model of evaluating the stability of protein to SGF/SIF was established.

Drug Stability↗
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↗