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At least 19 recordsLinked to original sources
PubMed2001

Microcalorimetric studies on the interaction mechanism between proteins and hydrophobic solid surfaces in hydrophobic interaction chromatography: effects of salts, hydrophobicity of the sorbent, and structure of the protein.

This study examines the effects of different salts as well as the influence of the relative hydrophobicities of different sorbents on the adsorption processes of proteins in hydrophobic interaction chromatography (HIC). Comparative data acquired by the equilibrium binding analysis and by isothermal titration microcalorimetry (ITC) are presented. In particular, thermodynamic parameters, including the enthalpy changes, related to the interactions between several globular proteins and various Toyopearl 650 M sorbents under solvent conditions containing either 2.0 M ammonium sulfate or 2.0 M sodium sulfate at pH 7.0 and 298.15 K have been evaluated in terms of the molecular properties of these systems. The results reveal that the dependence of the free energy change, deltaGads, for protein adsorption to HIC sorbents on the salt composition can be mainly attributed to the enthalpy changes associated with protein and sorbent dehydration and hydrophobic interactions. Differences in binding mechanisms between the n-butyl- and phenyl-HIC sorbents were evident. In the latter case, the participation of pi-pi hydrophobic interactions leads to significant differences in the associated enthalpy and entropy changes. Furthermore, an increase in the hydrophobicity of either the sorbent or the protein resulted in more negative values for the free energy change, which arose mostly from dehydration processes. Entropic effects favoring HIC adsorption increased with an increase in the exposed nonpolar surface area of the protein. Consequently, an increased contribution from the entropy change to the respective change in free energy occurs when HIC sorbents or proteins of higher hydrophobicity are employed, with these larger entropy changes consistent with a change in the interaction mechanism from a binding event dominated by adsorption to a partitioning-like process. Data extracted from the ITC measurements also provided insight into the interaction mechanisms that occur between proteins and hydrophobic solid surfaces, yielding information that can be applied to the HIC purification of proteins according to the concept of critical hydrophobicity of the system and its thermodynamic consequences.

Calorimetry↗
PubMed2000

Hydrophobic character of surface regions and total hydrophobicity of four variants of chromosomal class C beta-lactamase from Pseudomonas aeruginosa are identical. Chromatographic comparison of the hydrophobic character of the variants and the effect of focusing buffer composition on the separation of the variants by chromatofocusing with internal and external pH gradients.

The hydrophobic character of class C beta-lactamase molecular variants from Pseudomonas aeruginosa was compared by hydrophobic interaction chromatography and reversed-phase liquid chromatography, respectively. Separation of the variants by hydrophobic interaction chromatography was not achieved by modifying salt and pH of mobile phases. Reversed-phase liquid chromatography of the variants resulted in almost identical retention times. The results showed that the hydrophobic character of surface regions as well as total hydrophobicity of the variants are identical. The resolving power of external, internal and gradient chromatofocusing of the variants on strong and weak anion exchangers using low-molecular-mass buffers was compared to that of commercial ampholytes and showed no difference in separation pattern of the variants. Comparisons of variant isoelectric point (pI) values determined by chromatofocusing and isoelectric focusing showed that pI values determined by gradient chromatofocusing were most similar to the pI values determined by isoelectric focusing.

Buffers↗
PubMed1998

The hydrophobic effect. 2. Relative importance of the hydrophobic effect on the solubility of hydrophobes and pharmaceuticals in H-bonded solvents.

The quantitative development of the nonergodic mobile order thermodynamics involving the new interpretation of the hydrophobic effect leads to a general solubility equation. This equation is applied to predict the aqueous and alcohol solubility of chemicals ranging from nonpolar or slightly polar with no H-bonding capacity to polyfunctional polar compounds including pharmaceuticals. The analysis of the relative importance of the contributions involved in the solubility model [i.e., the fluidization of the solute (for solids), the correction for the mixing entropy, the change of the nonspecific cohesion forces, and the formation of solvent-solvent (hydrophobic effect), solute-solute, and solute-solvent H-bonds] unambiguously demonstrates that the hydrophobic effect is essential for predicting the aqueous or alcohol solubility of any substance in general, and of nonpolar compounds in particular. The difference between the origin of the solubility of hydrocarbons in water and of water in hydrocarbons is furthermore presented. In both cases, the quasilinear solubility dependence on the molar volume of the hydrocarbon is of an entropic nature.

Chemical Phenomena↗
PubMed2004

Effect of surface hydrophobicity distribution on retention of ribonucleases in hydrophobic interaction chromatography.

The effect of surface hydrophobicity distribution of proteins on retention in hydrophobic interaction chromatography (HIC) was investigated. Average surface hydrophobicity as well as hydrophobic contact area between protein and matrix were estimated using a classical thermodynamic model. The applicability of the model to predict protein retention in HIC was investigated on ribonucleases with similar average surface hydrophobicity but different surface hydrophobicity distribution. It was shown experimentally that surface hydrophobicity distribution could have an important effect on protein retention in HIC. The parameter "hydrophobic contact area," which comes from the thermodynamic model, was able to represent well the protein retention in HIC with salt gradient elution. Location and size of the hydrophobic patches can therefore have an important effect on protein retention in HIC, and the hydrophobic contact area adequately describes this.

Chromatography, Liquid↗
PubMed2003

Clustering of large hydrophobes in the hydrophobic core of two-stranded alpha-helical coiled-coils controls protein folding and stability.

The de novo design and biophysical characterization of two 60-residue peptides that dimerize to fold as parallel coiled-coils with different hydrophobic core clustering is described. Our goal was to investigate whether designing coiled-coils with identical hydrophobicity but with different hydrophobic clustering of non-polar core residues (each contained 6 Leu, 3 Ile, and 7 Ala residues in the hydrophobic core) would affect helical content and protein stability. The disulfide-bridged P3 and P2 differed dramatically in alpha-helical structure in benign conditions. P3 with three hydrophobic clusters was 98% alpha-helical, whereas P2 was only 65% alpha-helical. The stability profiles of these two analogs were compared, and the enthalpy and heat capacity changes upon denaturation were determined by measuring the temperature dependence by circular dichroism spectroscopy and confirmed by differential scanning calorimetry. The results showed that P3 assembled into a stable alpha-helical two-stranded coiled-coil and exhibited a native protein-like cooperative two-state transition in thermal melting, chemical denaturation, and calorimetry experiments. Although both peptides have identical inherent hydrophobicity (the hydrophobic burial of identical non-polar residues in equivalent heptad coiled-coil positions), we found that the context dependence of an additional hydrophobic cluster dramatically increased stability of P3 (Delta Tm approximately equal to 18 degrees C and Delta[urea](1/2) approximately equal to 1.5 M) as compared with P2. These results suggested that hydrophobic clustering significantly stabilized the coiled-coil structure and may explain how long fibrous proteins like tropomyosin maintain chain integrity while accommodating polar or charged residues in regions of the protein hydrophobic core.

Amino Acid Sequence↗
PubMed2003

Hydrophobicity gradient columns for the separation of trypsin inhibitor by hydrophobic interaction chromatography at low salt concentration.

We investigated hydrophobicity gradient columns composed of two columns packed with supports of different hydrophobicities in order to save time in protein separation by hydrophobic interaction chromatography at low salt concentration using a crude sample of trypsin inhibitor as a model sample. One of the two hydrophobicity gradient columns was packed with a support whose hydrophobicity was critically controlled for target protein (trypsin inhibitor) and the other was packed with a support which was less hydrophobic than the critically controlled hydrophobicity support. It was found that the hydrophobicity gradient columns are useful to separate samples containing impurities of a wide range of hydrophobicities within a reasonable time.

Chromatography, Liquid↗
PubMed1978

Differences in hydrophobic surface characteristics of porcine enteropathogenic Escherichia coli with or without K88 antigen as revealed by hydrophobic interaction chromatography.

Porcine enteropathogenic Escherichia coli strains possessing or lacking K88 antigen were studied by using hydrophobic interaction chromatography on cross-linked agarose gels with alkyl or aryl substituents (amphiphilic gels) to determine whether or not they possessed surface-associated hydrophobic properties. Strains with K88ab or K88ac antigen adsorbed to phenyl and octyl Sepharose gels in the presence of 4 M sodium chloride. This property correlated with phenotypic expression of K88 antigen. Cells grown at 37 degrees C but not those grown at 18 degrees C possessed hydrophobic adsorptive characteristics in addition to the property of mannose-resistant hemagglutination of guinea pig erythrocytes. Adsorption of K88-positive strains to gels with hydrophobic ligands was independent of O group and enterotoxicity. Strains lacking K88 antigen did not adsorb to the hydrophobically substituted derivatives of Sepharose and lacked mannose-resistant hemagglutinating characteristics. Neither the presence of additional polysaccharide K antigens nor nonhemagglutinating pili conferred the property of hydrophobic interaction on the strains. K88-positive bacteria had a lower electrophoretic migration rate than did K88-negative bacteria of the same serotype in free-zone electrophoresis. K88-positive bacteria also adsorbed strongly to hydrophobic ligands in the presence of 1 M ammonium sulfate, whereas K88-negative strains did not. These observations provide evidence for the suspected role of hydrophobic interaction in the adhesive properties of certain enteropathogenic strains of E. coli. Moreover, hydrophobic interaction chromatography provides convenient and rapid alternative means of screening strains for a property potentially associated with adhesiveness.

Adsorption↗
PubMed2005

[Cell-surface hydrophobicity and degradation characteristics of hydrophobic hydrocarbon degrading bacteria].

Three high efficient hydrocarbon degrading bacteria named HDB-1, HDB-2, HDB-3 were separated from the oil contaminant soil. This paper studied on the cell-surface hydrophobicity of these three bacteria and environment influence factor by MATH,and the results show that the xylene-water two-phase system is suitable for studying the cell-surface hydrophobicity of three bacteria; the cell-surface hydrophobicities of HDB-1, HDB-2 and HDB-3 are respectively 68.8%, 57.4% and 64.1%; the hydrophobicity changed with the difference of cultivation and time,carbon source, temperature and pH value; the removal ratio of 1 000 mg/L oil content for 6 day can reach 91.6%, 64.5% and 79.8%. The hydrophobicity is related definitely with the degradation of the organic pollutant, and the degradation rate of hydrophobic organic by the bacteria of high hydrophobicity is quicker than that by the bacteria of low hydrophobicity.

Bacteria↗
PubMed2005

Novel hydrophobicity ruler approach for determining the octanol/water partition coefficients of very hydrophobic compounds via their polymer/solvent solution distribution coefficients.

A novel hydrophobicity ruler approach for determining the octanol/water partition coefficients of very hydrophobic compounds is proposed, which is an indirect method that measures the polymer/solvent solution distribution coefficients (log Kp/s) of reference and unknown compounds. The log Kp/s values of the unknown compounds can be calibrated to their log Ko/w values via the correlation of the log Kp/s values of the reference compounds with their log Ko/w values. An organic solvent was used to increase the solubility of the very hydrophobic compounds in the aqueous solution, so that their concentrations and absorption amounts were high enough to be measured precisely. The solvent also reduced the hydrophobicity scale of the very hydrophobic compounds and controlled the amounts absorbed into the polymer phase, so that compounds spanning a very wide range of log Ko/w values could be measured in a single measurement and the coexisting compounds would not interfere each other. Poly(dimethylsiloxane) (PDMS), aqueous methanol solutions, and a series of 21 PCB (polychlorinated biphenyl) compounds were used to demonstrate the principle of the hydrophobicity ruler approach. The PCB compounds with known experimental log Ko/w values served as reference compounds, whereas the PCB compounds without known log Ko/w values were determined. The log Ko/w values determined for PCB126, PCB187, PCB197, PCB180, PCB170, and PCB195 were 6.94, 7.84, 8.33, 8.17, 7.92, and 8.49, respectively. The correlation of the log Kp/s values of the reference PCB compounds with their log Ko/w values was linear (log Ko/w=2.56 log Kp/s+1.08, R2=0.95). The hydrophobicity ruler approach is also a valuable tool for validating the experimental and theoretical log Ko/w values and identifying outliers in log Ko/w databases.

Acetone↗
PubMed2001

Two types of hydrophobic aggregates in aqueous solutions of chitosan and its hydrophobic derivative.

The aggregation phenomena in aqueous solutions of hydrophobically modified (HM) chitosan, containing 4 mol % of n-dodecyl side chains, were studied by viscometry and fluorescence spectroscopy with pyrene as a probe. The results are compared with those for unmodified chitosan. Surprisingly, fluorescence data reveal the appearance of intermolecular hydrophobic aggregates both in chitosan and in HM chitosan. Nevertheless, these polymers exhibit quite different rheological properties: upon the formation of aggregates the viscosity of HM chitosan sharply increases, while that of unmodified chitosan raises only slightly. The aggregation models for both chitosan and its hydrophobic derivative were proposed. It was shown that in solutions of HM chitosan two types of hydrophobic domains exist: hydrophobic domains typical for different associating polymers with hydrophobic side chains and hydrophobic domains inherent to chitosan itself.

Biopolymers↗
PubMed1995

Non-specific cross-reactivity of hydrophobic serum IgE to hydrophobic drugs.

The purpose of this work was to study the involvement of serum hydrophobic IgE in non-specific cross-reactions with hydrophobic drugs such as cyclohexenyl derivatives. Hydrophobic IgE were detected by radioimmunoassay. The results were expressed as the percentage of labelled anti-IgE which were adsorbed to the drug solid phase via IgE of the patient serum. Phenyl-Sepharose IgE-RIA was at 4.6 +/- 0.7%, 125 +/- 6.5% and 17.8 +/- 8.9% in control subjects (n = 24), in atopic patients with positive Phadiatop (n = 30) and in patients with drug allergy (n = 23), respectively. We selected five patients who were allergic to either penicillin, propofol, glafenin or paracetamol and who had a Phenyl-Sepharose IgE-RIA greater than 20%. In these five cases, IgE-RIA were positive (percentage at least twice more than that obtained with control sera) with all the solid phases prepared with hydrophobic drugs such as penicillin, propofol, glafenin, paracetamol and mexiletine. Inhibition of IgE binding by monoethylene-glycol showed that the cross-reactivity was due to hydrophobic binding of IgE to the drug. Three of the five patients were allergic to penicillin and underwent on adverse reaction against another cyclohexenyl derivative, namely propofol and glafenin. In conclusion, we have observed the presence of 'hydrophobic IgE (with positive Phenyl-Sepharose RIA)' in 64% of patients allergic to a hydrophobic drug.

Adsorption↗
PubMed1999

gamma-cyclodextrins greatly enhance translocation of hydrophobic fluorescent phospholipids from vesicles to cells in culture. Importance of molecular hydrophobicity in phospholipid trafficking studies.

Short-chain, fluorescent derivatives are commonly used to investigate intracellular phospholipid trafficking. However, their use can yield misleading results because they, unlike the native species, can rapidly distribute between organelles due to their low hydrophobicity. On the other hand, hydrophobic derivatives are very difficult to introduce to cells and thus have hardly been used. Here we show that carboxyethylated gamma-cyclodextrin (CE-gamma-CD) greatly enhances transfer of a variety of hydrophobic fluorescent phospholipid derivatives from vesicles to cultured cells. Several lines of evidence indicate that CE-gamma-CD enhances transfer of lipid molecules by increasing their effective concentration in the aqueous phase, rather than by inducing membrane fusion or hemifusion. Incubation with CE-gamma-CD and donor lipid vesicles does not extract cholesterol or phospholipids from the cells or compromise plasma membrane intactness or long term cell viability. Using CE-gamma-CD-mediated transfer, we introduced hydrophobic pyrene-labeled phosphatidylserine to the plasma membrane of fibroblast cells and followed their distribution with time. In contrast to what has been previously observed for other, less hydrophobic species, transport of this lipid to the Golgi apparatus or mitochondria was not detected. Rather, much of this fluorescent PS remained in the plasma membrane or was incorporated to various endocytotic compartments. These findings indicate that the native, typically hydrophobic phosphatidylserine molecules efflux only very slowly via the cytoplasm to intracellular organelles. This helps to explain how cells can maintain a very high concentration of phosphatidylserine in the inner leaflet of their plasma membrane. Furthermore, the present results underline the importance of using hydrophobic analogues when studying intracellular trafficking of many phospholipid classes.

Animals↗
PubMed1978

Inhibition of Bacillus subtilis spore germination by various hydrophobic compounds: demonstration of hydrophobic character of the L-alanine receptor site.

L-Alanine-initiated germination of Bacillus subtilis spores was inhibited by various kinds of hydrophobic compounds. Good correlation of inhibitory effect with hydrophobicity of the compound was demonstrated by using regression analysis in which the hydrophobic character was expressed by the partition coefficient in an octyl alcohol-water system. The correlation coefficient for 20 alcohols was 0.959, and that for 19 miscellaneous compounds was 0.906. Regression lines of the alcohols and other hydrophobic compounds were almost identical, showing that hydrophobic interaction played an important role in inhibition. Diphenylamine was one of the most effective inhibitors examined. n-Octyl, n-nonyl, and n-decyl alcohols were the most effective alcohols. The mode of inhibition by diphenylamine and n-octyl alcohol was a "mixed type" (competitive plus noncompetitive type) with respect to L-alanine; that by D-alanine was competitive inhibition. Sites for diphenylamine, n-octyl alcohol, and D-alanine may have overlapped. Inhibition was reversible by washing; heat resistance, stainability, and germination rate of the washed spores remained unaltered. Thus, we confirmed that the inhibition may occur before the initial trigger reaction of germination and that it may be due to the interaction between a hydrophobic compound and a hydrophobic region closely associated with the L-alanine receptor site on the spore.

Alanine↗
PubMed1992

Effects of total hydrophobicity and length of the hydrophobic domain of a signal peptide on in vitro translocation efficiency.

The hydrophobic domain of the signal peptide of OmpF-Lpp, a model secretory protein, was systematically engineered so as to be composed of different lengths of polyleucine residues or polymers with alternate leucine and alanine residues, and the effects of the length and nature of the hydrophobic stretch on the rate of in vitro translocation were studied using everted membrane vesicles of Escherichia coli. The translocation reaction exhibited high substrate specificity as to the number of hydrophobic residues. The results suggest that the hydrophobic domain is recognized specifically by a component(s) of the secretory machinery rather than nonspecifically by the hydrophobic region of the membrane. The in vitro translocation thus demonstrated required SecA and ATP and was markedly enhanced upon imposition of the proton motive force, as in the case of secretory proteins possessing a natural signal peptide. The highest translocation rate was obtained with the octamer in the case of polyleucine-containing signal peptides, whereas it was the decamer in the case of ones containing both leucine and alanine. These results suggest that the total hydrophobicity of the hydrophobic region of the signal peptides is an important determinant of the substrate specificity.

Adenosine Triphosphatases↗
PubMed2005

The hydrophobicity of the H3 histone fold differs from the hydrophobicity of the other three folds.

The eukaryotic histone dimers, H3-H4 and H2A-H2B, are formed in the cytosol prior to being transported into the nucleus and assembled into the nucleosome. Residue side-chain distances from the interior of the histone dimers are obtained with an ellipsoidal spatial metric and structural information provided by X-ray analyses at atomic resolution of the nucleosome core particles. While the spatial hydrophobic moment profiles of the dimers are comparable with profiles obtained previously that characterize the hydrophobic core of single-chain, single-domain globular soluble proteins, correlation coefficients between the side-chain hydrophobicities and distances from the interior of the H3-H4 dimer and H2A-H2B dimer differ significantly. This difference is traced to the H3 histone fold, which segregates fewer hydrophobic residues within the protein interior than the three other folds. Examination of the correlation coefficient between residue hydrophobicity and side-chain distance from the dimer interior over local regions of the fold sequence shows that the region of reduced correlation is associated mainly with the residues at the carboxyl end of the H3 histone fold, the helical region of the fold involved in the H3-H3' binding of the (H3-H4)(2) tetramer of the nucleosome. Hydrophobic interactions apparently contribute to the binding of this fourfold helical bundle and this evolutionary requirement may trade off against the requirement for H3-H4 dimer stability. The present results provide a different view than previously proposed, albeit of similar origin, to account for the reduced stability of the H3-H4 dimer compared with the H2A-H2B dimer.

Amino Acid Sequence↗
PubMed2002

Characterization and comparison of hydrophobic neutral and hydrophobic acid dissolved organic carbon isolated from three municipal landfill leachates.

The acid-precipitated (AP) and acid-soluble (AS) fractions of the combined hydrophobic neutral and hydrophobic acid dissolved organic carbon (DOC) were isolated from leachate collected from three municipal landfills of different age and redox conditions. The AP and the AS combined hydrophobic neutral and hydrophobic acid DOC comprised 6-15% and 51-66%, respectively, of the leachate nonpurgable organic carbon. Elemental analysis, infra-red spectroscopy, 13C CP-MAS nuclear magnetic resonance spectroscopy and dipolar dephasing experiments, and thermochemolysis gas chromatography/mass spectrometry results showed that the AP and AS fractions of hydrophobic neutral and hydrophobic acid DOC are highly aliphatic, with linear and branching moieties, and less oxidized than most terrestrial and aquatic humic substances. Very little, if any, polysaccharide or cellulose, lignin, or cutin components comprise these fractions. It is hypothesized that a majority of the organic carbon in these fractions originates highly branched, cyclic aliphatic organic compounds.

Acids↗
PubMed2000

Isothermal Titration Microcalorimetric Studies of the Effect of Temperature on Hydrophobic Interaction between Proteins and Hydrophobic Adsorbents.

This study attempted to comprehend how temperature affects hydrophobic interaction between proteins and hydrophobic adsorbents. By equilibrium batch analysis, we measured the adsorption isotherm to evaluate the protein-adsorbent affinity, while isothermal titration calorimetry was used to measure the adsorption enthalpy. In addition, the affinity and enthalpy differences between two proteins, alpha-chymotrypsinogen A and trypsinogen, with two adsorbents, butyl-Sepharose and octyl-Sepharose gel, under varying temperatures were studied with respect to the exposed hydrophobic segments of the protein and ligand hydrophobicity. The enthalpies obtained in this investigation can be used to more thoroughly understand the hydrophobic interaction between proteins and adsorbents. First, the adsorption isotherm experiments reveal that the adsorption quantity of the proteins with the Sepharose gels increases with temperature. For a microcalorimetric measurement, as temperature is increased from 298 to 310 K, the DeltaH value of alpha-chymotrypsinogen A with butyl-Sepharose increases, while the DeltaH value of trypsinogen is reduced. This is likely due to the fact that alpha-chymotrypsinogen A has a higher area of exposed hydrophobic segments than trypsinogen does. This observation also implies that as temperature increases, the interaction mechanism of alpha-chymotrypsinogen A with butyl-Sepharose changes from an adsorption-dominated process to a partitioning process. In addition, for octyl-Sepharose, the DeltaH value of alpha-chymotrypsinogen A is positive and decreases with temperature increment. However, the DeltaH value of trypsinogen was positive and increased with temperature. Therefore, we conclude that as temperature increases, the interaction mechanism of the proteins for octyl-Sepharose is a partitioning-dominated process. Copyright 2000 Academic Press.

Journal Article↗