Journal articles: 'Hydrophobicitet'

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Leelamanie, D. A. L., and Jutaro Karube. "Water stable aggregates of Japanese Andisol as affected by hydrophobicity and drying temperature." Journal of Hydrology and Hydromechanics 62, no. 2 (June 1, 2014): 97–100. http://dx.doi.org/10.2478/johh-2014-0019.

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Abstract Hydrophobicity is a property of soils that reduces their affinity for water, which may help impeding the pressure build-up within aggregates, and reducing aggregate disruption. The purpose of this study was to examine the relation of soil hydrophobicity and drying temperature to water stability of aggregates while preventing the floating of dry aggregates using unhydrophobized and hydrophobized surface Andisol. Soil was hydrophobized using stearic acid into different hydrophobicities. Hydrophobicity was determined using sessile drop contact angle and water drop penetration time (WDPT). Water stability of aggregates (%WSA) was determined using artificially prepared model aggregates. The %WSA increased as the contact angle and WDPT increased. Contact angle and WDPT, which provided maximum %WSA showing less than 1 s of floating, was around 100° and 5 s, respectively. Although the %WSA gradually increased with increasing contact angle and WDPT above this level, high levels of hydrophobicity initiated aggregate floating, which would cause undesirable effects of water repellency. Heating at 50°C for 5 h d-1 significantly affected %WSA and hydrophobicity in hydrophobized samples, but did not in unhydrophobized samples. The results indicate that the contact angle and wetting rate (WDPT) are closely related with the water stability of aggregates. The results further confirm that high levels of hydrophobicities induce aggregate floating, and the drying temperature has differential effects on hydrophobicity and aggregate stability depending on the hydrophobic materials present in the soil.

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Guerrero, Esther, José María Saugar, Katsumi Matsuzaki, and Luis Rivas. "Role of Positional Hydrophobicity in the Leishmanicidal Activity of Magainin 2." Antimicrobial Agents and Chemotherapy 48, no. 8 (August 2004): 2980–86. http://dx.doi.org/10.1128/aac.48.8.2980-2986.2004.

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ABSTRACT The emergence of membrane-active antimicrobial peptides as new alternatives against pathogens with multiantibiotic resistance requires the design of better analogues. Among the different physicochemical parameters involved in the optimization of linear antimicrobial peptides, positional hydrophobicity has recently been incorporated. This takes into consideration the concept of the topological distribution of hydrophobic residues throughout the sequence rather than the classical concept of hydrophobicity as a global parameter of the peptide, calculated as the summation of the individual hydrophobicities of the residues. In order to assess the contribution of this parameter to the leishmanicidal mechanisms of magainin 2 analogues, the activities of two of these analogues, MG-H1 (GIKKFLHIIWKFIKAFVGEIMNS) and MG-H2 (IIKKFLHSIWKFGKAFVGEIMNI), which have similar charges, amino acid compositions, and hydrophobicities but different positional hydrophobicities, against Leishmania donovani promastigotes were assayed (T. Tachi, R. F. Epand, R. M. Epand, and K. Matsuzaki, Biochemistry 41:10723-10731, 2002). The activities were compared with that of the parental peptide, F5W-magainin 2 (GIGKWLHSAKKFGKAFVGEIMNS). The three peptides were active at micromolar concentrations, in the order MG-H2 > MG-H1 > F5W-magainin 2. These activities differ from their hemolytic and bactericidal activities. The results demonstrate that positional hydrophobicity, which reflects the presence of short stretches of sequences rich in hydrophobic amino acids, plays an important role in the activities of leishmanicidal peptides.

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Regester, Geoffrey O., R. John Pearce, Victor W. K. Lee, and Michael E. Mangino. "Heat-related changes to the hydrophobicity of cheese whey correlate with levels of native β-lactoglobulin and α-lactalbumin." Journal of Dairy Research 59, no. 4 (November 1992): 527–32. http://dx.doi.org/10.1017/s0022029900027199.

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SummaryCorrelations were identified between levels of the native whey proteins, β-lactoglobulin and α-lactalbumin and the surface and total hydrophobicities of cheese whey in response to different heat treatments. Heat-induced changes in the native βlactoglobulin content and surface hydrophobicity of whey exhibited the most significant linear relationship while correlations between total hydrophobicity and the native proteins were less significant because of an atypical rise in the n−heptane-binding capacity of whey after high-temperature treatment. The content of native β-lactoglobulin in whey was more sensitive to heating than the content of native α-lactalbumin, while heat-related changes in the total hydrophobicity of whey were generally greater than similar changes in surface hydrophobicity.

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Chalmers, G. W., J. M. Gosline, and M. A. Lillie. "The hydrophobicity of vertebrate elastins." Journal of Experimental Biology 202, no. 3 (February 1, 1999): 301–14. http://dx.doi.org/10.1242/jeb.202.3.301.

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An evolutionary trend towards increasing hydrophobicity of vertebrate arterial elastins suggests that there is an adaptive advantage to higher hydrophobicity. The swelling and dynamic mechanical properties of elastins from several species were measured to test whether hydrophobicity is associated with mechanical performance. Hydrophobicity was quantified according to amino acid composition (HI), and two behaviour-based indices: the Flory-Huggins solvent interaction parameter (chi1), and a swelling index relating tissue volumes at 60 and 1 degrees C. Swelling index values correlated with chi1 and, for most species studied, with HI, suggesting that the different approaches used to quantify hydrophobicity are equally valid. Dynamic mechanical properties were measured both in a closed system, to control the effects of water content, and in an open system, to determine whether the increased swelling of hydrophobic materials at low temperatures offsets the direct stiffening effect of cold. There were no biologically significant differences in mechanical behaviour in either open or closed systems that could be attributed to hydrophobicity. Therefore, although the original function of hydrophobicity in an ancestral elastin may have been to produce molecular mobility, mechanical performance did not drive a subsequent increase in hydrophobicity. Higher hydrophobicities may have arisen to facilitate the manufacture of the elastic fibre.

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Miklavžin, Ana, Mateja Cegnar, Janez Kerč, and Julijana Kristl. "Effect of surface hydrophobicity of therapeutic protein loaded in polyelectrolyte nanoparticles on transepithelial permeability." Acta Pharmaceutica 68, no. 3 (September 1, 2018): 275–93. http://dx.doi.org/10.2478/acph-2018-0032.

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Abstract Oral delivery of protein drugs is greatly limited by low hydrophobicity, an important determinant for intestinal epithelial permeation and bioavailability. Herein, surface properties of recombinant erythropoietin were investigated using the fluorescent dye bis-ANS to monitor relative hydrophobicity for correlation with permeabilities with Caco-2 cells. At various pHs, bis-ANS fluorescence intensity indicated different surface hydrophobicities of erythropoietin molecules. Erythropoietin incorporated in chitosan or chitosan-trimethylchitosan (CS-TMC) nanoparticles prepared by polyelectrolyte complexation and ionotropic gelation with tripolyphosphate also showed different surface hydrophobicities. Chitosan nanoparticles with erythropoietin provided the most hydrophobic surface, followed by free erythropoietin (in water) and that loaded into CS-TMC nanoparticles. Chitosan nanoparticles were more effective than CS-TMC nanoparticles for permeation of erythropoietin across Caco-2 cell monolayers; the lowest permeability was shown by erythropoietin itself. Thus, hydrophilic protein molecules complexed with polyelectrolytes can provide more hydrophobic surfaces that enhance transepithelial permeability. This bis-ANS method also provides valuable information for the design of polyelectrolyte nanoparticules for oral delivery of protein drugs.

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6

Jeffs, Lloyd B., Ilungo J. Xavier, Russell E. Matai, and George G. Khachatourians. "Relationships between fungal spore morphologies and surface properties for entomopathogenic members of the general Beauveria, Metarhizium, Paecilomyces,Tolypocladium, and Verticillium." Canadian Journal of Microbiology 45, no. 11 (November 1, 1999): 936–48. http://dx.doi.org/10.1139/w99-097.

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The surface properties of aerial conidia (AC) from 24 strains of entomopathogenic fungi were studied and compared using the salt-mediated aggregation and sedimentation (SAS) assay, electron microscopy, FITC-labelled lectins, and spore dimensions. Spores with rugose surfaces were hydrophobic, whereas hydrophilic spores had smooth surfaces. Correlation analysis found no link between spore dimensions and either hydrophobicity or surface carbohydrates. However, there was a strong positive correlation between spore hydrophobicity and surface carbohydrates. The three spore types of Beauveria bassiana were all shown to possess discrete surface hydrophobicities, which were also strongly linked to surface carbohydrate profiles. Various chemical treatments had pronounced effects on spore surface properties, with sodium dodecyl sulfate (SDS) and formic acid (FA) reducing both lectin binding and surface hydrophobicity. When FA-protein extracts were separated and analysed using SDS-PAGE, only the hydrophobic spores had low molecular weight hydrophobin-like peptides that were unglycosylated and contained disulfide bonds. The strains with hydrophilic AC had much lower levels of FA-extractable protein per spore dry weight compared to their more hydrophobic counterparts. Moreover, extracts of the more hydrophobic spores tended to have greater protein:carbohydrate ratios.Key words: fungi, spores, hydrophobicity, lectins, morphology, microbial insecticides, protein.

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Zhang, Yongjian, Xin Gao, Hai Chu, and Bernard P. Binks. "Various crust morphologies of colloidal droplets dried on a super-hydrophobic surface." Canadian Journal of Physics 98, no. 11 (November 2020): 1055–59. http://dx.doi.org/10.1139/cjp-2019-0451.

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We have studied the evaporation of water droplets containing silica nanoparticles of various hydrophobicities deposited on a super-hydrophobic substrate. Evaporation induces particle accumulation at the droplet surface and results in the formation of a crust that buckles during further shrinkage. For droplets containing hydrophilic particles, a bowl-shaped crust was observed. For droplets containing hydrophobic particles, the crust develops a multi-buckled shape that could be completely suppressed by increasing the relative humidity. The varied buckling behavior of droplets may be attributed to the different mechanical properties of the gelled layer where particle hydrophobicity plays a role. Our work highlights the important role of particle hydrophobicity and relative humidity in the final crust morphology, thus shedding light on crust shape control and material design via the droplet evaporation approach.

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Millsap, Kevin W., Gregor Reid, Henny C. van der Mei, and Henk J. Busscher. "Cluster analysis of genotypically characterized Lactobacillus species based on physicochemical cell surface properties and their relationship with adhesion to hexadecane." Canadian Journal of Microbiology 43, no. 3 (March 1, 1997): 284–91. http://dx.doi.org/10.1139/m97-039.

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Lactobacilli can interfere with the adhesion of uropathogens to uroepithelial cells and catheter materials through a variety of mechanisms, such as adhesion. Lactobacillus adhesion to substratum surfaces has been theorized to result from the physicochemical properties of the interacting surfaces. In this paper physicochemical cell-surface properties, including hydrophobicity (determined by water contact angles), pH dependence of zeta potentials, elemental surface composition (determined by X-ray photoelectron spectroscopy), and adhesion to hexadecane, of four genotypically characterized Lactobacillus species (eight L. acidophilus, eight L. casei, four L. fermentum, and seven L. plantarum strains) were determined to see whether a grouping of the strains according to their phenotypes could be obtained that corresponded with the genotypic characterization of the strains. The strains showed major differences in physicochemical cell-surface properties: at the species level relationships could be observed between water contact angles, isoelectric points, and the N/C and O/C elemental surface concentration ratios, with nitrogen-containing groups (proteins) being responsible for increased hydrophobicities and isoelectric points, and oxygen-containing groups (phosphates and polysaccharides) yielding decreased hydrophobicities and isoelectric points. A hierarchical cluster analysis grouped all L. acidophilus strains in one well-separated cluster that also included two L. casei and two L. fermentum strains. Separation of L. acidophilus from the other species was done predominantly on the basis of increased cell surface hydrophobicity (average water contact angle of 63°) and isoelectric point (approximately pH 3.3) as compared with the other species, which had lower water contact angles and isoelectric points, and corresponded with the observation that only L. acidophilus strains adhered in measurable numbers to hexadecane. Also, the L. plantarum strains were grouped closely together in one cluster, but this cluster was heterogeneous due to the inclusion of L. casei and L. fermentum strains.Key words: Lactobacillus, surface properties, hydrophobicity, zeta potential, adhesion.

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9

Jeffs, Lloyd B., and George G. Khachatourians. "Estimation of spore hydrophobicity for members of the genera Beauveria, Metarhizium, and Tolypocladium by salt-mediated aggregation and sedimentation." Canadian Journal of Microbiology 43, no. 1 (January 1, 1997): 23–28. http://dx.doi.org/10.1139/m97-004.

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The surface hydrophobicities of fungal spores from the entomopathogenic genera Beauveria, Metarhizium, and Tolypocladium were quantitatively measured and compared using a novel assay employing salt-mediated aggregation and sedimentation (SAS). Spores with greater hydrophobicities were easily identified by their aggregation and sedimentation out of suspension at faster rates under lower salt concentrations. Of the three ammonium salts investigated for their salting-out potentials, ammonium sulfate gave the most pronounced effect, closely followed by ammonium chloride, and then ammonium acetate. Using the SAS assay, spores exhibited more pronounced hydrophobic properties at pH 5.8 than at higher pH values of 6.8 and 7.8. The effects of temperature and spore concentration upon the SAS assay were also investigated, with greater spore sedimentation occurring at elevated temperature. By plotting SAS values for two ammonium salt concentrations (0.01 and 0.1 M) in a coordinate system, it was possible to differentiate the hydrophobicities of all five spore isolates, clearly demonstrating the superiority of SAS over an existing phase-exclusion assay. The significance and potential of the SAS assay are also discussed.Key words: fungal spores, hydrophobicity, microassay, SAS, salting out, microbial insecticides.

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10

ASAMOTO, Yasumasa, Susumu TAZUMA, Hidenori OCHI, Kazuaki CHAYAMA, and Hiroshi SUZUKI. "Bile-salt hydrophobicity is a key factor regulating rat liver plasma-membrane communication: relation to bilayer structure, fluidity and transporter expression and function." Biochemical Journal 359, no. 3 (October 25, 2001): 605–10. http://dx.doi.org/10.1042/bj3590605.

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Bile-salt hydrophobicity regulates biliary phospholipid secretion and subselection. The aim of this study was to determine whether bile salts can influence liver plasma membrane phospholipids and fluidity in relation to the ATP-dependent transporter. Rats were depleted of bile salts by overnight biliary diversion and then sodium taurocholate was infused intravenously at a constant rate (200nmol/min per 100g of body weight), followed by infusion of bile salts with various hydrophobicities (taurochenodeoxycholate, tauroursodeoxycholate, tauro-β-muricholate, tauro-α-muricholate at 200nmol/min per 100g of body weight). The hydrophobicity of the infused bile salts correlated with that of biliary phospholipids, but was inversely related to that of the canalicular membrane bilayer. Canalicular membrane fluidity (estimated by 1,6-diphenyl-1,3,5-hexatriene fluorescence depolarization) and expression of multidrug-resistance proteins (Mrp2, Mrp3) and apical Na+-dependent bile-salt transporter (ASBT) were increased by hydrophilic bile salts, although there was no marked change in the expression of P-glycoprotein subfamilies (Mdr2). Bile-salt export pump (Bsep) expression was increased along with increasing bile-salt hydrophobicity. Bile salts modulate canalicular membrane phospholipids and membrane fluidity, as well as the ATP-dependent transporter expression and function, and these actions are associated with their hydrophobicity. The cytoprotective effect of hydrophilic bile salts seems to be associated with induction of Mrp2, Mrp3 and ASBT.

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Janoschke, Marco, Mirjam Zimmermann, Anna Brunauer, Raffael Humbel, Tina Junne, and Martin Spiess. "Efficient integration of transmembrane domains depends on the folding properties of the upstream sequences." Proceedings of the National Academy of Sciences 118, no. 33 (August 9, 2021): e2102675118. http://dx.doi.org/10.1073/pnas.2102675118.

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The topology of most membrane proteins is defined by the successive integration of α-helical transmembrane domains at the Sec61 translocon. The translocon provides a pore for the transfer of polypeptide segments across the membrane while giving them lateral access to the lipid. For each polypeptide segment of ∼20 residues, the combined hydrophobicities of its constituent amino acids were previously shown to define the extent of membrane integration. Here, we discovered that different sequences preceding a potential transmembrane domain substantially affect its hydrophobicity requirement for integration. Rapidly folding domains, sequences that are intrinsically disordered or very short or capable of binding chaperones with high affinity, allow for efficient transmembrane integration with low-hydrophobicity thresholds for both orientations in the membrane. In contrast, long protein fragments, folding-deficient mutant domains, and artificial sequences not binding chaperones interfered with membrane integration, requiring higher hydrophobicity. We propose that the latter sequences, as they compact on their hydrophobic residues, partially folded but unable to reach a native state, expose hydrophobic surfaces that compete with the translocon for the emerging transmembrane segment, reducing integration efficiency. The results suggest that rapid folding or strong chaperone binding is required for efficient transmembrane integration.

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Iqbal, M., M. Asghar Jamal, Maqsood Ahmed, and Bashir Ahmed. "Partial molar volumes of some drugs in water and ethanol at 35 °C." Canadian Journal of Chemistry 72, no. 4 (April 1, 1994): 1076–79. http://dx.doi.org/10.1139/v94-135.

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Partial molar volumes, V0, of six drugs, mostly anaesthetics, viz., cinchocaine HCl, lidocaine HCl, mepivacaine HCl, procaine HCl, propranolol HCl, tetracaine HCl, in water and ethanol, calculated from precision densities obtained at 35 °C from a vibrating tube densitometer, are reported in this work. The data represent the smaller volumes of drug molecules in ethanol than in water. Volume contribution of hydrochloride part were calculated and excluded from V0 to assess the volume of free base component of the solutes. Volumes of free bases were also found smaller in ethanol, although much closer to those in water. The differences in volumes are interpreted as due to hydrophobicity of solutes. Relative hydrophobicities were estimated from volumes of transfer from aqueous to organic media. Correlation of V0 with van der Waal volumes are also reported. The hydrophobicity of these compounds is proposed to play a key role in the resulting drug action. Possible mechanism of drug binding with the membrane structure is also discussed.

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Tazuma, S., R. L. Barnhart, L. E. Reeve, H. Tokumo, and R. T. Holzbach. "Biliary secretion of organic anions in the dog: association with defined lipid particles." American Journal of Physiology-Gastrointestinal and Liver Physiology 255, no. 6 (December 1, 1988): G745—G751. http://dx.doi.org/10.1152/ajpgi.1988.255.6.g745.

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Organic anions have recently been found to partition in vitro into various biliary lipid particulate species according to their relative hydrophobicities. To establish the physiological relevance of these observations, we intravenously injected various radiolabeled organic anions and assessed the distributions of parent compounds and their metabolites to lipid particles in canine bile. Partitioning into various biliary lipid particles was determined by gel permeation chromatography. Relative hydrophobicities of the various organic anions and their radiolabeled conjugates were determined by reverse-phase high-pressure liquid chromatography. A strong positive correlation (P less than 0.001) was found between percent vesicular association and degree of hydrophobicity for a given organic anion and/or its more polar conjugate. We conclude that 1) the hydrophobic-hydrophilic balance of organic anions is a key factor governing their partitioning to lipid particles secreted in bile; 2) the present study agrees well with our previously published in vitro observations; and 3) other chemical constituents, e.g., proteins, mucin, etc., appear to have little or no effect on organic anion transport in bile.

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HODGKINSON, STEVE, and WOLFGANG P. KASCHKA. "PATTERNS OF HYDROPHOBICITY FOUND IN THE FIRST AND SECOND TRANSMEMBRANE DOMAINS OF SOLUTE TRANSPORTERS SUGGEST A POSSIBLE ROLE IN NASCENT PROTEIN ANCHORING AND ORGANIZATION." Journal of Bioinformatics and Computational Biology 09, no. 04 (August 2011): 471–88. http://dx.doi.org/10.1142/s0219720011005367.

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Solute transporters (STs) are an important subgroup of integral membrane proteins that facilitate the translocation of a diverse range of solutes such as sugars, amino acids, and neurotransmitters across cell membranes. Sequence analysis indicates that STs possess multiple stretches of hydrophobic-rich amino acids that are organized into the transmembrane domains (TMDs) of the functional protein, but exactly how the correct spatial arrangement of these domains is achieved remains a challenging problem. We hypothesized that perhaps differences in interdomain hydrophobicity might play some role in this process. To test this hypothesis, we generated a heptadic model of the alpha helix and mapped the average hydrophobicities (coaxial) and hydrophobic moments (radial) of 108 TMDs found in 9 different human ST proteins. Our results, taken together with earlier work from other groups, suggest that spatial patterns of hydrophobicity found in TMDs 1 and 2 are consistent with a role for these domains in the initial anchoring of the nascent ST protein to the endoplasmic reticulum (ER), as it emerges from the ribosome complex and perhaps in the subsequent spatial organisation of STs.

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Wolfenden, Richard, Charles A. Lewis, Yang Yuan, and Charles W. Carter. "Temperature dependence of amino acid hydrophobicities." Proceedings of the National Academy of Sciences 112, no. 24 (June 1, 2015): 7484–88. http://dx.doi.org/10.1073/pnas.1507565112.

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The hydrophobicities of the 20 common amino acids are reflected in their tendencies to appear in interior positions in globular proteins and in deeply buried positions of membrane proteins. To determine whether these relationships might also have been valid in the warm surroundings where life may have originated, we examined the effect of temperature on the hydrophobicities of the amino acids as measured by the equilibrium constants for transfer of their side-chains from neutral solution to cyclohexane (Kw>c). The hydrophobicities of most amino acids were found to increase with increasing temperature. Because that effect is more pronounced for the more polar amino acids, the numerical range of Kw>c values decreases with increasing temperature. There are also modest changes in the ordering of the more polar amino acids. However, those changes are such that they would have tended to minimize the otherwise disruptive effects of a changing thermal environment on the evolution of protein structure. Earlier, the genetic code was found to be organized in such a way that—with a single exception (threonine)—the side-chain dichotomy polar/nonpolar matches the nucleic acid base dichotomy purine/pyrimidine at the second position of each coding triplet at 25 °C. That dichotomy is preserved at 100 °C. The accessible surface areas of amino acid side-chains in folded proteins are moderately correlated with hydrophobicity, but when free energies of vapor-to-cyclohexane transfer (corresponding to size) are taken into consideration, a closer relationship becomes apparent.

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POWELL, Ashley A., Janna M. LaRUE, A. K. BATTA, and Jesse D. MARTINEZ. "Bile acid hydrophobicity is correlated with induction of apoptosis and/or growth arrest in HCT116 cells." Biochemical Journal 356, no. 2 (May 24, 2001): 481–86. http://dx.doi.org/10.1042/bj3560481.

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Faecal bile acids have long been associated with colon cancer; highly hydrophobic bile acids, which induce apoptosis, have been implicated in the promotion of colon tumours. The moderately hydrophobic chemopreventive agent ursodeoxycholic acid (UDCA) does not induce apoptosis; rather, it causes colon-derived tumour cells to arrest their growth. To investigate the relationship between bile acid hydrophobicity and biological activity we examined 26 bile acids for their capacity to induce apoptosis or alter cell growth. We found that the rapidity with which, and the degree to which, bile acids could induce apoptosis or growth arrest was correlated with their relative hydrophobicities. Of the bile acids tested, only deoxycholic acid (DCA) and chenodeoxycholic acid, the most hydrophobic bile acids tested, could induce apoptosis in less than 12h in the human colon cancer cell line HCT116. The moderately hydrophobic bile acids hyoDCA, lagoDCA, norDCA, homoUDCA and isoUDCA induced growth arrest at 12h but longer incubations resulted in apoptosis. Conjugation of glycine or taurine to the bile acids decreased relative hydrophobicity and eliminated biological activity in our assays. In addition, we tested a subset of these bile acids for their ability to translocate across cell membranes. When 14C-labelled and 3H-labelled DCA, UDCA and lagoDCA were added to cell cultures, we found only minimal uptake by colon cells, whereas hepatocytes had considerably higher absorption. These experiments suggest that hydrophobicity is an important determinant of the biological activity exhibited by bile acids but that under our conditions these activities are not correlated with cellular uptake.

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Ma, Wenjun, Baokun Qi, Rokayya Sami, Lianzhou Jiang, Yang Li, and Hui Wang. "Conformational and Functional Properties of Soybean Proteins Produced by Extrusion-Hydrolysis Approach." International Journal of Analytical Chemistry 2018 (2018): 1–11. http://dx.doi.org/10.1155/2018/9182508.

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The conformational and functional changes of soybean protein after a hybrid extrusion-hydrolysis method were evaluated. Three extrusion temperatures (60, 80, and 100°C) were used prior to enzymatic hydrolysis. The hydrolysis degrees, molecular weight profiles, solubilities, surface hydrophobicities, sulphydryl contents, disulfide bound, water holding capacity, emulsion, and foam properties of the protein isolated from the enzyme-hydrolyzed extruded soybeans were analyzed. It shows that extrusion caused significant changes in the hydrophobicity, molecular weight distribution, solubility, surface hydrophobicity, emulsification activity, and stability of the protein. The increase of molecular weights could be attributed to the formation of protein aggregates during extrusion. Extrusion and enzymatic hydrolysis led to a sharp increase in the number of disulfide bonds with a decrease of the sulphydryl group. The water holding capacity and the solubility of protein increased with the increase of extrusion temperature and hydrolysis time. Extrusion improved the emulsifying activity but reduced the emulsifying stability of the recovered proteins. Extrusion improved the foam capacity but reduced the foam stability of the proteins. The data demonstrated that the extrusion-hydrolysis treatment significantly altered the conformational and functional properties of soybean protein, which may be further optimized for the development of new soy protein ingredient with desired functional properties.

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LIU, G. R., Y. CHENG, DONG MI, and Z. R. LI. "A STUDY ON SELF-INSERTION OF PEPTIDES INTO SINGLE-WALLED CARBON NANOTUBES BASED ON MOLECULAR DYNAMICS SIMULATION." International Journal of Modern Physics C 16, no. 08 (August 2005): 1239–50. http://dx.doi.org/10.1142/s0129183105007856.

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Molecular dynamics simulation is performed to investigate self-insertion behaviors of peptides into single-walled carbon nanotubes (SWCNTs) in water environment. Peptides of different hydrophobicities and varied lengths are tested to show that the propensities of peptides to self-insert into SWCNTs differ drastically. Our results indicate that there exists a potential well for the system of SWCNT and peptide that is able to self-insert into the nanotube. Further investigations of energy components demonstrate that electrostatic interactions, combined with van der Waals interactions, play dominant roles in the self-insertion of peptides into nanotubes. In addition, we also observe a significant correlation between the propensity of a peptide to insert into nanotube and its hydrophobicity. Such results provide valuable information on the potential applications of carbon nanotubes in the fields of drug delivery, drug design and protein control, etc.

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Haymet, A. D. J. "Hydrophobicity." Current Biology 9, no. 3 (February 1999): R81—R82. http://dx.doi.org/10.1016/s0960-9822(99)80053-0.

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Galli, G. "Dissecting hydrophobicity." Proceedings of the National Academy of Sciences 104, no. 8 (February 13, 2007): 2557–58. http://dx.doi.org/10.1073/pnas.0700176104.

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Andrew Karplus, P. "Hydrophobicity regained." Protein Science 6, no. 6 (June 1997): 1302–7. http://dx.doi.org/10.1002/pro.5560060618.

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GUSILS, C., A. PÉREZ CHAIA, S. GONZÁLEZ, and G. OLIVER. "Lactobacilli Isolated from Chicken Intestines: Potential Use as Probiotics." Journal of Food Protection 62, no. 3 (March 1, 1999): 252–56. http://dx.doi.org/10.4315/0362-028x-62.3.252.

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Lactobacillus strains were tested for their in vitro probiotic properties. Cell surface hydrophobicity was found to be very high for Lactobacillus fermentum subsp. cellobiosus and Salmonella Gallinarum; high values could indicate a greater ability to adhere to epithelial cells. Studies on Lactobacillus animalis indicated relative cell surface hydrophobicities smaller than those of L. fermentum subsp. cellobiosus and L. fermentum. L. animalis and Enterococcus faecalis were able to coaggregate with L. fermentum subsp. cellobiosus and L. fermentum, respectively, but not with Salmonella Gallinarum. After mixed-culture studies for determining suitable growth behavior, the pair of strains L. animalis plus L. fermentum subsp. cellobiosus was selected for an attempted challenge against Salmonella Gallinarum. Double and triple mixed-culture studies indicated that selected lactobacillus strains were able to retain their beneficial characteristics in the presence of Salmonella Gallinarum such as presence of lectins, production of antimicrobial compounds, and ability to grow and compete. The selected microorganisms can be considered as potential ingredients for a chicken probiotic feed formulation intended to control salmonellosis and also improve poultry sanitation.

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Graziano, Giuseppe. "Hydrophobicity of benzene." Biophysical Chemistry 82, no. 1 (November 1999): 69–79. http://dx.doi.org/10.1016/s0301-4622(99)00105-2.

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Tian, Ye, and Lei Jiang. "Intrinsically robust hydrophobicity." Nature Materials 12, no. 4 (March 20, 2013): 291–92. http://dx.doi.org/10.1038/nmat3610.

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Eichacker, Lutz A., Bernhard Granvogl, Oliver Mirus, Bernd Christian Müller, Christian Miess, and Enrico Schleiff. "Hiding behind Hydrophobicity." Journal of Biological Chemistry 279, no. 49 (September 27, 2004): 50915–22. http://dx.doi.org/10.1074/jbc.m405875200.

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Taher, I. A. A., and T. W. Macfarlane. "Hydrophobicity ofActinobacillus actinomycetemcomitans." Microbial Ecology in Health and Disease 4, no. 2 (January 1991): 101–4. http://dx.doi.org/10.3109/08910609109140270.

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Naylor, Gavin J. P., Timothy M. Collins, and Wesley M. Brown. "Hydrophobicity and phylogeny." Nature 373, no. 6515 (February 1995): 565–66. http://dx.doi.org/10.1038/373565b0.

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Qinghua Zhang, Qinghua Zhang, Lian Zhou Lian Zhou, Wei Yang Wei Yang, Haohao Hui Haohao Hui, Jian Wang Jian Wang, and Qiao Xu Qiao Xu. "Sol-gel preparation of a silica antireflective coating with enhanced hydrophobicity and optical stability in vacuum." Chinese Optics Letters 12, no. 7 (2014): 071601–71604. http://dx.doi.org/10.3788/col201412.071601.

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Olorunfemi, Idowu. "Soil Hydrophobicity: An Overview." Journal of Scientific Research and Reports 3, no. 8 (January 10, 2014): 1003–37. http://dx.doi.org/10.9734/jsrr/2014/7325.

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Greene, Mark E. "Light switches surface hydrophobicity." Materials Today 9, no. 11 (November 2006): 15. http://dx.doi.org/10.1016/s1369-7021(06)71690-x.

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Kumar, Anuj, Jaladhar Mahato, Mayank Dixit, and G. Naresh Patwari. "Progressive Hydrophobicity of Fluorobenzenes." Journal of Physical Chemistry B 123, no. 47 (October 29, 2019): 10083–88. http://dx.doi.org/10.1021/acs.jpcb.9b08057.

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32

Menger, F. M., and U. V. Venkataram. "A microscopic hydrophobicity parameter." Journal of the American Chemical Society 108, no. 11 (May 1986): 2980–84. http://dx.doi.org/10.1021/ja00271a029.

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Nakai, Shuryo. "Measurement of Protein Hydrophobicity." Current Protocols in Food Analytical Chemistry 9, no. 1 (August 2003): B5.2.1—B5.2.13. http://dx.doi.org/10.1002/0471142913.fab0502s09.

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Dill, K. "The meaning of hydrophobicity." Science 250, no. 4978 (October 12, 1990): 297–98. http://dx.doi.org/10.1126/science.2218535.

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Graziano, Giuseppe. "Cavity Thermodynamics and Hydrophobicity." Journal of the Physical Society of Japan 69, no. 5 (May 15, 2000): 1566–69. http://dx.doi.org/10.1143/jpsj.69.1566.

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Reifsteck, F., S. Wee, and B. J. Wilkinson. "Hydrophobicity--hydrophilicity of staphylococci." Journal of Medical Microbiology 24, no. 1 (August 1, 1987): 65–73. http://dx.doi.org/10.1099/00222615-24-1-65.

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Owen, Michael J. "Silicone Hydrophobicity and Oleophilicity." Silicon 9, no. 5 (March 1, 2014): 651–55. http://dx.doi.org/10.1007/s12633-014-9188-0.

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Maimon, Adi, Amit Gross, and Gilboa Arye. "Greywater-induced soil hydrophobicity." Chemosphere 184 (October 2017): 1012–19. http://dx.doi.org/10.1016/j.chemosphere.2017.06.080.

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Bangham, J. Andrew. "Data-sieving hydrophobicity plots." Analytical Biochemistry 174, no. 1 (October 1988): 142–45. http://dx.doi.org/10.1016/0003-2697(88)90528-3.

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Schneider, P. F., and T. V. Riley. "Cell-surface hydrophobicity ofStaphylococcus saprophyticus." Epidemiology and Infection 106, no. 1 (February 1991): 71–75. http://dx.doi.org/10.1017/s0950268800056454.

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SUMMARYThe cell-surface hydrophobicity of 100 urinary isolates ofStaphylococcus saprophyticus, cultured from symptomatic females in the general population, was assessed using a two-phase aqueous: hydrocarbon system. Relatively strong cell-surface hydrophobicity was exhibited by 79 isolates using the criteria employed, while only 2 of the remaining 21 isolates failed to demonstrate any detectable hydrophobicity. Cell-surface hydrophobicity may be a virulence factor ofS. saprophyticus. important in adherence of the organism to uroepithelia. Additionally, the data support the concept that cell-surface hydrophobicity may be a useful predictor of clinical significance of coagulase-negative staphylococci isoated from clinical sources.

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Bryant, R., S. H. Doerr, and M. Helbig. "Effect of oxygen deprivation on soil hydrophobicity during heating." International Journal of Wildland Fire 14, no. 4 (2005): 449. http://dx.doi.org/10.1071/wf05035.

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Previous studies of the effects of heating on soil hydrophobicity have been conducted under free availability of oxygen. Under fire, however, soils may be deprived of oxygen due to its consumption at the heat source and inadequate replenishment in the soil. In the present study, effects of heating on soil hydrophobicity are examined for three initially hydrophobic Australian eucalypt forest soils under standard and oxygen-deprived atmospheres for temperatures (T) of 250–600°C and durations (tE) 2–180 min. Hydrophobicity assessments using water droplet penetration time (WDPT) tests indicate substantial differences between the absence and presence of oxygen. Heating to 250–300°C enhanced hydrophobicity from initial respective WDPTs of 2029 s, 361 s and 15 s to > 18 000 s for all samples under both atmospheres. Depending on heating duration, hydrophobicity was eliminated (WDPTs ~0 s) in air between 210 and 340°C, but under oxygen-deprived conditions between 400 and 510°C. Relationships between the destruction temperature for hydrophobicity TD and tE provide temperature–duration thresholds below which hydrophobicity persists under oxygen concentrations <21%. As established temperature–duration thresholds for hydrophobicity destruction are based on the free availability of oxygen, caution is advised in their applicability to field situations where heating under burning may occur in oxygen-depleted conditions.

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Yan, Kang, and Zhong Yuan Zhang. "Application of Improved Back Propagation Neural Network for the Recognition of Composite Insulator Hydrophobicity Grade." Applied Mechanics and Materials 373-375 (August 2013): 1155–58. http://dx.doi.org/10.4028/www.scientific.net/amm.373-375.1155.

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The detection of hydrophobicity is an important way to evaluate the performance of composite insulator, which is helpful to the safe operation of composite insulator. In this paper, the image processing technology and Back Propagation neural network is introduced to recognize the composite insulator hydrophobicity grade. First, hydrophobic image is preprocessed by histogram equalization and adaptive median filter, then the image was segmented by Ostu threshold method, and four features associated with hydrophobicity are extracted. Finally, the improved Back Propagation neural network is adopted to recognize composite insulator hydrophobicity grade. The experimental results show that the improved Back Propagation neural network can accurately recognize the composite insulator hydrophobicity

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Chen, Yuxin, Michael T. Guarnieri, Adriana I. Vasil, Michael L. Vasil, Colin T. Mant, and Robert S. Hodges. "Role of Peptide Hydrophobicity in the Mechanism of Action of α-Helical Antimicrobial Peptides." Antimicrobial Agents and Chemotherapy 51, no. 4 (December 11, 2006): 1398–406. http://dx.doi.org/10.1128/aac.00925-06.

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ABSTRACT In the present study, the 26-residue amphipathic α-helical antimicrobial peptide V13KL (Y. Chen et al., J. Biol. Chem. 2005, 280:12316-12329, 2005) was used as the framework to study the effects of peptide hydrophobicity on the mechanism of action of antimicrobial peptides. Hydrophobicity was systematically decreased or increased by replacing leucine residues with less hydrophobic alanine residues or replacing alanine residues with more hydrophobic leucine residues on the nonpolar face of the helix, respectively. Hydrophobicity of the nonpolar face of the amphipathic helix was demonstrated to correlate with peptide helicity (measured by circular dichroism spectroscopy) and self-associating ability (measured by reversed-phase high-performance liquid chromatography temperature profiling) in aqueous environments. Higher hydrophobicity was correlated with stronger hemolytic activity. In contrast, there was an optimum hydrophobicity window in which high antimicrobial activity could be obtained. Decreased or increased hydrophobicity beyond this window dramatically decreased antimicrobial activity. The decreased antimicrobial activity at high peptide hydrophobicity can be explained by the strong peptide self-association which prevents the peptide from passing through the cell wall in prokaryotic cells, whereas increased peptide self-association had no effect on peptide access to eukaryotic membranes.

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Ioelovich, Michael. "Adjustment of Hydrophobic Properties of Cellulose Materials." Polymers 13, no. 8 (April 12, 2021): 1241. http://dx.doi.org/10.3390/polym13081241.

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In this study, physicochemical and chemical methods of cellulose modification were used to increase the hydrophobicity of this natural semicrystalline biopolymer. It has been shown that acid hydrolysis of the initial cellulose increases its crystallinity, which improves hydrophobicity, but only to a small extent. A more significant hydrophobization effect was observed after chemical modification by esterification, when polar hydroxyl groups of cellulose were replaced by non-polar substituents. The esterification process was accompanied by the disruption of the crystalline structure of cellulose and its transformation into the mesomorphous structure of cellulose esters. It was found that the replacement of cellulose hydroxyls with ester groups leads to a significant increase in the hydrophobicity of the resulting polymer. Moreover, the increase of the number of non-polar groups in the ester substituent contributes to rise in hydrophobicity of cellulose derivative. Depending on the type of ester group, the hydrophobicity increased in the following order: acetate < propionate < butyrate. Therefore, tributyrate cellulose (TBC) demonstrated the most hydrophobicity among all studied samples. In addition, the mixed ester, triacetobutyrate cellulose (TAB), also showed a sufficiently high hydrophobicity. The promising performance properties of hydrophobic cellulose esters, TBC and TAB, were also demonstrated.

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Xie, Qiang, Tianhui Hao, Jifeng Zhang, Chao Wang, Rongkui Zhang, and Hui Qi. "Anti-Icing Performance of a Coating Based on Nano/Microsilica Particle-Filled Amino-Terminated PDMS-Modified Epoxy." Coatings 9, no. 12 (November 20, 2019): 771. http://dx.doi.org/10.3390/coatings9120771.

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Coatings with anti-icing performance possess hydrophobicity and low ice adhesion strength, which delay ice formation and make ice removal easier. In this paper, the anti-icing performance of nano/microsilica particle-filled amino-terminated PDMS (A-PDMS)-modified epoxy coatings was investigated. In the process, the influence of the addition of A-PDMS on the hydrophobicity and ice adhesion strength was investigated. Furthermore, the influences of various weight ratios of nanosilica/microsilica (Rn/m) on the hydrophobicity and ice adhesion strength of the coating were investigated. Hydrophobicity was evaluated by contact angle (CA) and contact angle hysteresis (CAH) tests. Ice adhesion strength was measured by a centrifugal adhesion test. The addition of A-PDMS markedly increased hydrophobicity and decreased ice adhesion. The size combination of particles obviously affects hydrophobicity but has little effect on ice adhesion. Finally, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) were used to reveal the anti-icing mechanism of the coatings.

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Masuoka, James, and Kevin C. Hazen. "Cell Wall Mannan and Cell Surface Hydrophobicity in Candida albicans Serotype A and B Strains." Infection and Immunity 72, no. 11 (November 2004): 6230–36. http://dx.doi.org/10.1128/iai.72.11.6230-6236.2004.

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ABSTRACT Cell surface hydrophobicity contributes to the pathogenesis of the opportunistic fungal pathogen Candida albicans. Previous work demonstrated a correlation between hydrophobicity status and changes in the acid-labile, phosphodiester-linked β-1,2-oligomannoside components of the N-linked glycans of cell wall mannoprotein. Glycan composition also defines the two major serotypes, A and B, of C. albicans strains. Here, we show that the cell surface hydrophobicity of the two serotypes is qualitatively different, suggesting that the serotypes may differ in how they modulate cell surface hydrophobicity status. The cell wall mannoproteins from hydrophilic and hydrophobic cells of both serotypes were compared to determine whether the glycan differences due to serotype affect the glycan differences due to hydrophobicity status. Composition analysis showed that the protein, hexose, and phosphate contents of the mannoprotein fraction did not differ significantly among the strains tested. Electrophoretic profiles of the acid-labile mannan differed only with hydrophobicity status, not serotype, though some strain-specific differences were observed. Furthermore, a newly available β-1,2-oligomannoside ladder allowed unambiguous identification of acid-labile mannan components. Finally, to assess whether the acid-stable mannan also affects cell surface hydrophobicity status, this fraction was fragmented into its component branches by acetolysis. The electrophoretic profiles of the acid-stable branches were very similar regardless of hydrophobicity status. However, differences were observed between serotypes. These results support and extend our current model that modification of the acid-labile β-1,2-oligomannoside chain length but not modification of the acid-stable region is one common mechanism by which switching of cell surface hydrophobicity status of C. albicans strains occurs.

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Palmgren, R., F. Jorand, P. H. Nielsen, and J. C. Block. "Influence of oxygen limitation on the cell surface properties of bacteria from activated sludge." Water Science and Technology 37, no. 4-5 (February 1, 1998): 349–52. http://dx.doi.org/10.2166/wst.1998.0663.

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Cell surface hydrophobicity is believed to be important to flocculation in activated sludge and biofilm systems. Optimization of these processes includes changes in the growth conditions of the bacteria. A number of factors influence cell surface hydrophobicity. The influence of oxygen on the cell surface hydrophobicity of 4 bacteria isolated from activated sludge was tested. The bacteria were grown in batch cultures with and without oxygen limitation. It was found that oxygen limitation generally caused a lowering of the cell surface hydrophobicity. The study also showed that there are many difficulties in measuring cell surface hydrophobicity since other cell surface properties, such as surface charge, influence the measurement methods. The MATH test was employed to establish how assay conditions influenced the results.

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Bredholt, Harald, Per Bruheim, Martin Potocky, and Kjell Eimhjellen. "Hydrophobicity development, alkane oxidation, and crude-oil emulsification in a Rhodococcus species." Canadian Journal of Microbiology 48, no. 4 (April 1, 2002): 295–304. http://dx.doi.org/10.1139/w02-024.

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The relationship between the phenomena alkane oxidation, extreme hydrophobicity of the cell surface, and crude-oil emulsification in Rhodococcus sp. strain 094 was investigated. Compounds that induce the emulsifying ability simultaneously induced the cytochrome P450-containing alkane oxidizing system and the transition from low to high cell-surface hydrophobicity. Exposed to inducers of crude-oil emulsification, the cells developed a strong hydrophobic character during exponential growth, which was rapidly lost when entering stationary phase. The loss in hydrophobicity coincided in time with the crude-oil emulsification, indicating that the components responsible for the formation of cell-surface hydrophobicity act as excellent emulsion stabilisers only after release from the cells. Rhodococcus sp. strain 094 possessed three distinct levels of cell-surface hydrophobicity. One level of low hydrophobicity was characteristic of cells in late stationary phase and was independent of growth substrate. A second and more hydrophobic level was observed for cells in exponential phase grown on water-soluble substrates, while a third level, characterised by extreme cell hydrophobicity, was observed for cells in exponential phase cultivated on hydrophobic substrates such as hexadecane. The production of the oil-emulsifying agents seems to require external sources of nitrogen and phosphate.Key words: petroleum, Rhodococcus, seawater, bacteria, bioremediation.

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Peters, Christoph, and Arne Elofsson. "Why is the biological hydrophobicity scale more accurate than earlier experimental hydrophobicity scales?" Proteins: Structure, Function, and Bioinformatics 82, no. 9 (April 29, 2014): 2190–98. http://dx.doi.org/10.1002/prot.24582.

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Dutta, Kingshuk, and Patit Paban Kundu. "Amphiphiles as hydrophobicity regulator: Fine tuning the surface hydrophobicity of an electropolymerized film." Journal of Colloid and Interface Science 397 (May 2013): 192–98. http://dx.doi.org/10.1016/j.jcis.2013.01.045.

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Journal articles on the topic 'Hydrophobicitet'

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