Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0393754 (HSA)
 2,996 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In the present work we analyze the dynamics of fibronectin (FN) adsorption on two different stable titanium oxides, with varied surface roughness, and chemically similar to those used in clinical practice. The two types of titanium oxide surfaces used were TiO2 sputtered on Si (TiO2 sp) and TiO2 formed on commercially pure titanium after immersion in H2O2 (TiO2 cp). Surface characterization was previously carried out using different techniques (Sousa, S. R.; Moradas-Ferreira, P.; Melo, L. V.; Saramago, B.; Barbosa, M. A. Langmuir 2004, 20 (22), 9745-9754). Imaging and roughness analysis before and after FN adsorption used atomic force microscopy (AFM) in tapping mode, in air, and in magnetic alternating current mode, in liquid (water). FN adsorption as a function of time was followed by X-ray photoelectron spectroscopy (XPS), by radiolabeling of FN with 125I (125I-FN), and by ellipsometry. Exchangeability studies were performed using FN and HSA. AFM roughness analysis revealed that, before FN adsorption, both TiO2 surfaces exhibited a lower root-mean-square (Rq) and maximum peak with the depth of the maximum valley (Rmax) roughness in air than in water, due to TiO2 hydration. After protein adsorption, the same behavior was observed for the TiO2 sp substrate, while Rq and Rmax roughness values in air and in water were similar in the case of the TiO2 cp substrate, for the higher FN concentration used. Surface roughness was always significantly higher on the TiO2 cp surfaces. AFM led to direct visualization of adsorbed FN on both surfaces tested, indicating that after 10 min of FN incubation the TiO2 sp surface was partially covered by FN. The adsorbed protein seems to form globular aggregates or ellipsoids, and FN aggregates coalesce, forming clusters as the time of adsorption and the concentration increase. Radiolabeling of FN revealed that a rapid adsorption occurs on both surfaces and the amount adsorbed increased with time, reaching a maximum after 60 min of incubation. Time dependence is also observed for the evolution of the atomic (%) of N determined by XPS and by the increase of the thickness by ellipsometry. TiO2 cp adsorbs more FN than the TiO2 sp surfaces, after 60 min of adsorption, as shown by the radiolabeling data. FN molecules are also more strongly attached to the former surface as indicated by the exchangeability studies. The overall results provide novel evidence that FN spontaneously adsorbs as a self-assembly at TiO2 surfaces as a function of time. The aggregate structure is an intermediate feature shared by some protein fibrillar assemblies at interfaces, which is believed to promote cell adhesion and cytoskeleton organization (Pellenc, D.; Berry, H.; Gallet, O. J. Colloid Interface Sci. 2006, 298 (1), 132-144. Maheshwari, G.; Brown, G.; Lauffenburger, D. A.; Wells, A.; Griffith, L. G. J. Cell Sci. 2000, 113 (10), 1677-1686).
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PMID:Dynamics of fibronectin adsorption on TiO2 surfaces. 1750 64

The membrane phospholipid affinity of ten quinolone antibacterial agents, including both acidic and zwitterionic compounds, was measured by HPLC on two different immobilized artificial membrane (IAM) stationary phases, namely IAM.PC.MG and IAM.PC.DD2; it is expressed as the logarithm of the retention factor measured with (or extrapolated to) 100% aqueous eluent at pH 7.0, logk(w)(IAM). Quinolones are a class of highly potent, orally active, broad-spectrum antibacterial agents. For these compounds, lipophilicity values in n-octanol found in the literature, either calculated or measured, are not consistent with each other and are too low to be compatible with their pharmacokinetic properties. The logk(w)(IAM) values obtained in this study showed no relation with any of the lipophilicity values in the literature (clogP(a), clogP(b), MLP, logD(7.4)). In contrast, they were collinear with a new lipophilicity scale we had previously obtained by an original ion-pair reversed-phase HPLC method set up to estimate the lipophilicity of the neutral forms, logP(N). Moreover, when comparing the retention of quinolones on IAM to the retention of structurally unrelated neutral compounds, we observed that they interact with phospholipids with the same affinity as neutral isolipophilic compounds. The use of an eluent at pH 5.5, instead of pH 7.0, increased the retention on IAM not only for acidic, but also for zwitterionic congeners, indicating that phospholipid affinity is enhanced in the experimental conditions that depress the ionization of the acidic function, even when the ionization of the amino function increases simultaneously. To gain an insight into the mechanism of quinolones/serum-protein interactions, we investigated about possible relationships between quinolones affinity data for serum proteins and IAM data. Quinolone affinity for both HSA and AGP was already demonstrated poorly related to n-octanol lipophilicity values, probably due to the occurrence of electrostatic interactions. Only poor relationships were found between IAM and HSA affinity data, whereas quite good relationships were found with AGP affinity data. However, IAM.PC.DD2 data correlated better than those on IAM.PC.MG with quinolone affinity for both serum-proteins, mainly due to the fact that IAM.PC.MG phase is scarcely discriminative for the compounds with the highest retention values. The results suggest that IAM retention can produce a lipophilicity scale that, unlike solvent/water partition coefficients, is consistent with the pharmacokinetic behaviour of zwitterionic quinolones.
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PMID:Comparison between immobilized artificial membrane (IAM) HPLC data and lipophilicity in n-octanol for quinolone antibacterial agents. 1754 May 45

With the objective of tuning the lipophilicity of ligands and maintaining the neutrality and stability of Gd(III) chelate, we designed and synthesized two bis(amide) derivatives of TTDA, TTDA-BMA and TTDA-BBA, and a mono(amide) derivative, TTDA-N-MOBA. The ligand protonation constants and complex stability constants for various metal ions were determined in this study. The identification of the microscopic sites of protonation of the amide ligand by 1H NMR titrations show that the first protonation site occurs on the central nitrogen atom. The values of the stability constant of TTDA-mono and bis(amide) complex are significantly lower than those of TTDA and DTPA, but the selectivity constants of these ligands for Gd(III) over Zn(II) and Cu(II) are slightly higher than those of TTDA and DTPA. On the basis of the water-exchange rate values available for [Gd(TTDA-BMA)(H2O)], [Gd(TTDA-BBA)(H2O)] and [Gd(TTDA-N-MOBA)(H2O)]-, we can state that, in general, the replacement of one carboxylate group by an amide group decreases the water-exchange rate of the gadolinium(III) complexes by a factor of about three to five. The decrease in the exchange rate is explained in terms of a decreased steric crowding and charge effect around the metal ion when carboxylates are replaced by an amide group. In addition, to support the HSA protein binding studies of lipophilic [Gd(TTDA-N-MOBA)(H2O)]- and [Gd(TTDA-BBA)(H2O)] complexes, further protein-complex binding was studied by ultrafiltration and relaxivity studies. The binding constants (KA) of [Gd(TTDA-N-MOBA)(H2O)]- and [Gd(TTDA-BBA)(H2O)] are 8.6 x 10(2) and 1.0 x 10(4) dm3 mol(-1), respectively. The bound relaxivities (r1(b)) are 51.8 and 52 dm3 mmol(-1) s(-1), respectively. The KA value of [Gd(TTDA-BBA)(H2O)] is similar to that of MS-325 and indicates a stronger interaction of [Gd(TTDA-BBA)(H2O)] with HSA.
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PMID:Synthesis, complexation and water exchange properties of Gd(III)-TTDA-mono and bis(amide) derivatives and their binding affinity to human serum albumin. 1759 91

The antioxidant capacities, antioxidant activities, k(inh), and stoichiometric factors, n, of water-soluble derivatives of bilirubin (BR), BR-human serum albumin (BR-HSA), and BR-ditaurate disodium conjugate (BRC) were determined in aqueous/lipid dispersions of sodium dodecyl sulfate (SDS) micelles/methyl linoleate and in bilayers of dilinoleoylphosphatidylcholine (DLPC) during initiation by water-soluble azo-bis-amidinopropane dihydrochloride (ABAP). The inhibition rate constants for BRC and BR-HSA were similar in micelles (k(inh) approximately 1.3 x 10(4) M(-1) s(-1)), where n approximately 2, whereas the k(inh) for BR-HSA dropped by (1/2) in bilayers. The dimethyl ester of bilirubin (BRDE) gave a k(inh) only one-tenth that of the vitamin E analog, pentamethylhydroxychroman (PMHC) in SDS micelles/methyl linoleate when initiated by lipid-soluble azo-bis-2,4-dimethylvaleronitrile (DMVN). Biliverdin hydrochloride (BVHCl) was NOT an effective peroxyl radical-trapping agent in the micellar phase during initiation by ABAP or DMVN containing methyl linoleate but it inhibited oxygen uptake in the aqueous phase. Both BRC and BR-HSA extended the total radical antioxidant parameter (TRAP) of human blood plasma and their contribution to TRAP was in the range of 5-10% of the natural TRAP of blood plasma, depending on the BR content determined in the blood plasma.
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PMID:Bilirubin as an antioxidant in micelles and lipid bilayers: its contribution to the total antioxidant capacity of human blood plasma. 1764 May 70

The chiral complexation of bilirubin (BR) with bovine and human serum albumin (BSA and HSA), and the aggregation of the complexes at the heptane+chloroform(5:1)/water interface were studied via UV/Vis absorption and circular dichroism (CD) measurements in combination with the centrifugal liquid membrane (CLM) method. The interfacial adsorptivities of BR, BSA and their complexes were also studied by performing interfacial tension measurements at the interface. The changes in the absorbances and the induced CD amplitudes of the interfacial BR-BSA complex provided insights into the mechanism of the conformational enantioselective complexation at the interface, and indicated that the chiral conversion induced by the complexation with BSA was from the P(+) form to the M(-) form of BR. The broadening of the 450 nm band and the appearance of a new shoulder at 474 nm further supported the formation of aggregates of the complexes at the interface. The dependence of the CD amplitude on the molar ratio of BSA to BR revealed that the composition of the complex was 1:1 BSA:BR. The probable interfacial reaction scheme was proposed, and the affinity constant of BR-BSA at the interface was found to be 4.67 x 10(8) M(-2). The interfacial complexation and aggregation of BR and HSA were weaker than those of the BR-BSA complex due to the different BR binding positions adopted for BSA and HSA and the binding effect of chloroform.
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PMID:Chiral complexation and aggregation of bilirubin with serum albumin at a liquid/liquid interface. 1765 79

Two new GdEGTA (EGTA = ethylene glycol-bis(2-aminoethylether)-N,N,N',N'-tetraacetic acid) derivatives incorporating aromatic moieties into the oxoethylenic bridge have been prepared and characterised, their conjugates to HSA investigated and an unprecedented high relaxivity, close to that predicted by theory, interpreted in terms of the combined effect of restricted local rotation and fast rate of water exchange.
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PMID:Maximizing the relaxivity of HSA-bound gadolinium complexes by simultaneous optimization of rotation and water exchange. 1800 21

We describe the stacking and separation of proteins by CE under discontinuous conditions in conjunction with light-emitting diode induced fluorescence (LEDIF) detection using a violet LED at 405 nm. The proteins were derivatized with naphthalene-2,3-dicarboxaldehyde (NDA) to form NDA-protein derivatives prior to CE-LEDIF analysis. During the separation, poly(ethylene oxide) (PEO) solution containing CTAB enters from the cathodic inlet to the capillary via electroosomotic flow (EOF). The optimum conditions are: the capillary was filled with 50 mM glycine buffer (pH 9.0) containing 1.0 mM CTAB, NDA-protein derivatives were prepared in deionized water containing 1.0 mM CTAB, and 0.6% PEO was prepared in 50 mM glycine (pH 9.0) containing 2.0 mM CTAB. The analysis of four NDA-protein derivatives is fast (<3 min), with RSD <1.5% in terms of migration time. In order to improve the sensitivity of NDA-protein derivatives, a stacking approach based on increases in viscosity and electric field, as well as sieving was applied. The efficient stacking approach provides LODs (S/N = 3) of 2.41, 0.59, 0.61, and 4.22 nM for trypsin inhibitor, HSA, beta-lactoglobulin, and lysozyme, respectively. In addition, we also applied the stacking approach to determination of the concentration of HSA in one urine sample, which was determined to be 0.31 +/- 0.05 microM (n = 3).
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PMID:Stacking and separation of protein derivatives of naphthalene-2,3-dicarboxaldehyde by CE with light-emitting diode induced fluorescence detection. 1806 34

We report here a new, label-free approach to measure serum protein binding constants. The assay is able to measure HSA K d values in the milli-molar to micromolar range. The protein is not immobilized on any surface and the assay self-corrects for nonspecific adsorption. No mass balance is required to get accurate binding constants and it is not necessary to wait for equilibrium to extract the binding constant. The assay runs in a 96-well format using commercially available parts and is, therefore, relatively easy to implement and automate. As the chemical membranes used are not water permeable, there is no volume change due to the osmotic pressure and pretreatment (soaking) is not necessary. The concept can potentially be extended to other proteins and could thus serve as a label-free technique for general binding constant measurements.
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PMID:New approach to measure protein binding based on a parallel artificial membrane assay and human serum albumin. 1834 14

This study was undertaken to investigate the influence of fatty acid binding on the unfolding of HSA and how the fatty acid molecules can influence and/or compete with other ligand molecules bound to the protein. The equilibrium unfolding of fatted and fatty acid free HSA was measured by overlapping of unfolding transition curves monitored by different probes for secondary and tertiary structure and determining changes in free energy of unfolding. Proteins stability was studied by fluorescence spectroscopy, whereas conformational changes were detected by circular dichroism techniques. We have suggested a "molten globule" like intermediate state of HSA at a fairly high concentration of GnHCl (3.2 for fatty acid free and 3.6 for fatted). The free energy of stabilization (DeltaG(D)(H2O)) in the presence of fatty acid was found to be 900 cal mol(-1). We also analyze the effects of fatty acid on binding of ligands using spectroscopic technique and reported the equilibrium constants and free energies obtained from the binding and unfolding experiments.
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PMID:Comparative studies of unfolding and binding of ligands to human serum albumin in the presence of fatty acid: spectroscopic approach. 1845 86

The purpose of this study is to investigate the change in collapse appearance and temperature of protein/sugar mixtures as a function of nucleation temperature (T(n)), sublimation velocity (V(sub)) and the sugar/protein mole ratio when performing freeze-dry microscopy experiments. BSA and HSA were used as sample proteins and mixed with either sucrose or trehalose. Differential scanning calorimetry was used to determine the corresponding glass transition temperatures (T'g). To allow a more representative comparison between these analytical methods, a collapse midpoint temperature (T(c-50)) was introduced. While there was no distinct correlation between T(n) and the onset of collapse (T(oc)) for either mixture, V(sub) was found to correlate with the measured collapse temperature which is important for comparability of experiments. Furthermore, V(sub) could be used to qualitatively investigate the product resistance to water vapor flow. A dramatic change in the appearance of collapse was found for high sugar/protein mole ratios (> or =362:1) which needs to be considered to avoid a misinterpretation of T(oc) data. At low protein concentrations midpoint T'g data showed good agreement with T(oc) values but were found significantly lower at higher protein concentrations. Application of the Gordon-Taylor equation failed to predict the critical temperature for any of the protein/sugar mixtures studied.
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PMID:Freeze-dry microscopy of protein/sugar mixtures: drying behavior, interpretation of collapse temperatures and a comparison to corresponding glass transition data. 1882 13


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