Inhibitory effect of 13 taxane diterpenoids from Chinese yew (Taxus chinensis var. mairei) on the proliferation of HeLa cervical cancer cells

The inhibitory effect of 13 taxanes isolated from the Chinese yew (Taxus chinensis var. mairei) on the proliferation of human cervical cancer HeLa cells were examined using an MTT assay. Four compounds having a hydrophobic cinnamate side chain showed antiproliferative activity, which may be due to increased cell permeability.     

Backbone and sidechain 1H, 13C and 15N chemical shift assignments of the hydrophobin DewA from Aspergillus nidulans

Hydrophobins are proteins secreted by filamentous fungi that are able to self-assemble into monolayers at hydrophobic:hydrophilic interfaces. The layers are amphipathic and can reverse the wettability of surfaces. Hydrophobins have several roles in fungal development, including the formation of coatings on fungal structures to render them hydrophobic. Here we report the backbone and sidechain assignments for the class I hydrophobin DewA from the fungus Aspergillus nidulans.     

Effect of Glucose on the Interaction of Hydrophobic Compounds with the Alanine Receptor Field of Bacillus subtilis Spores during Initiation of Germination

Glucose interfered with the inhibitory action of hydrophobic compounds, such as n-octanol, diphenylamine and 2-tert-butylphenol, during L-alanine-initiated germination of Bacillus subtilis spores. The action of glucose on the action of the hydrophobic compounds was not competitive, and the binding affinity of glucose was not essentially affected by the hydrophobic compounds, indicating the presence of separate binding sites for glucose and the hydrophobic compounds. The binding affinity of D-alanine, a competitive inhibitor of L-alanine, was not affected by the hydrophobic compounds, indicating separate binding sites for D-alanine and the hydrophobic compounds. A possible arrangement of the binding sites for glucose and for the hydrophobic compounds in relation to those for L- and D-alanine on the spores is discussed.     

Effect of a low concentration of a cationic steroid antibiotic (CSA-13) on the formation of a biofilm by Pseudomonas aeruginosa

Aims: Cationic steroids like CSA‐13 have been designed by analogy with antimicrobial cationic peptides and have bactericidal properties. The purpose of this work was to evaluate the effect of a low concentration (1 mg l^?1) of CSA‐13 on the formation of a biofilm by eight strains of Pseudomonas aeruginosa (four mucoid and four nonmucoid strains) on an inert surface. Method and Results: The biofilm formation was measured with the Crystal Violet method. CSA‐13 inhibited the formation of a biofilm by three strains. The zeta potential varied among the strains. The inhibition by the cationic steroid analogue affected the populations of bacteria with the lowest zeta potential. P. aeruginosa bound a fluorescent, more hydrophobic analogue of CSA‐13 but there was no correlation between this binding and the inhibition by CSA‐13 of biofilm formation. The interaction of CSA‐13 with bacteria did not modify their ability to produce rhamnolipids. Conclusions: A low concentration of CSA‐13 inhibits the formation of a biofilm by P. aeruginosa through electrostatic interactions and without affecting the production of rhamnolipids. Significance and Impact of the Study: A low, nontoxic concentration of CSA‐13 might be beneficial for the prevention of biofilm formation.     

Selective isolation of bacteria from soil with hydrophobic materials

Bacterial strains having a hydrophobic cell surface have often been considered as degraders of hydrophobic organic pollutants in soil. In this study, bacterial strains were isolated using hydrophobic materials from 12 soil samples, and their cell surface hydrophobicity was determined by evaluating their adherence to n-hexane. Bacterial strains isolated using polytetrafluoroethylene (PTFE) membrane were more hydrophobic on an average than those isolated with styrene–divinylbenzene (DVB) particles or octadecylsilyl silica gel (ODS) particles. Strains closely related to Burkholderia cepacia could be selectively isolated using the PTFE membrane; those closely related to Ralstonia pickettii, using ODS and DVB particles; and those closely related to B. fungorum, using DVB. These results indicate that bacterial strains having a hydrophobic cell surface or within certain phyla can be selectively isolated from soils using hydrophobic materials, and that this isolation method would be useful for collecting candidates for bioremediation of hydrophobic pollutants.     

Hydrophobic characteristics ofBacillus spores

Spores from severalBacillus species displayed a strong affinity for hexadecane and other hydrophobic solvents. The binding ofBacillus subtilis spore suspensions to octyl-Sepharose was enhanced by ammonium sulfate and other salts, but was inhibited by detergents. Treatment of spore suspensions with strong denaturants promoted their adherence to hexadecane, presumably by exposing hydrophobic residues in coat proteins. The hydrophobic characteristics of spores may be important in the ecological adaptation of certain bacteria.     

An Efficient Synthesis of Deuterated (±)-Dihydrozeatin-d5 and Its Riboside

The antifungal activity of 22 derivatives of 1-(3,5-dichlorophenyl)-2,5-pyrrolidinedione and 6 derivatives of 3-(3,5-dichlorophenyl)-2,4-oxazolidinedione, having various substituents on the imido rings, against Botrytis cinerea was determined by the agar medium dilution method. The structure-activity relationships were analyzed using the physicochemical parameters of the molecules: such as the hydrophobic log P, the electronic σ*, and the steric E_s^c values with the multiple regression technique. Only the hydrophobic effect is significant in determining the activity variations of both series of compounds. Furthermore, the structure-activity relationships of these two series of compounds are represented by an identical equation, having only the hydrophobic term as a variable.     

Legionella pneumophila cell envelope: Permeability to hydrophobic molecules

Legionella pneumophila is sensitive to a number of toxic hydrophobic compounds. Suspensions of cells bound large amounts of the dye crystal violet, and disk agar diffusion assays confirmed the marked sensitivity to this compound. Fatty acids were also inhibitory to the growth ofL. pneumophila in liquid media, and growth inhibition increased with increasing chain length to a maximum with myristic acid. Oxygen uptake by respiring cells was inhibited by similar concentrations of fatty acids.L. pneumophila was also sensitive to low concentrations of progesterone. These results indicated thatL. pneumophila has an outer membrane with unusual permeability to hydrophobic compounds. This characteristic was accompanied by a measurable cell surface hydrophobicity as determined by adherence of the bacterium to the hydrocarbon hexadecane.     

Adsorption of bacterial capsular exopolymers to hydrophilic and hydrophobic surfaces: A 2D‐FTIR analysis

Analysis of the adsorption of capsular exopolymers (EPS) from Pseudomonas sp. NCIMB 2021 to hydrophilic and hydrophobic gold surfaces was examined, in situ, using Fourier transform infrared spectroscopy. The molecular sequence of events occurring upon EPS adsorption to hydrophilic and hydrophobic surfaces has been elucidated using dynamic 2D‐FTIR correlation spectroscopy. This method of analysis enables the enhancement of the resolution of overlapping spectral features and the elucidation of time‐dependent changes. The data reveal the existence of surface dependent adsorption mechanisms. At both surfaces, the aromatic tyrosyl side chains of the protein moiety displace water. This is followed by an adsorption step dominated by carboxylate groups. However, at the hydrophobic surface, the two steps are interrupted by the ingress of water back to the surface. Furthermore, the amount of neutral exopolymer present was greater at the hydrophilic surface than the hydrophobic surface.     

Organic solvents for bioorganic synthesis

Summary The influence of solvents on enzymatic activity and stability was investigated. As a model reaction the -chymotrypsin-catalyzed esterification of N-acetyl-l-phenylalanine with ethanol was used. The enzyme was adsorbed on porous glass beads and used in various solvents. Small amounts of water were added to increase the enzymatic activity. These enzyme preparations obeyed. Michaelis-Menten kinetics. K _m,app decreased slightly with the log P value of the solvent while V _app increased markedly with the log P value. Log P values were also useful for generalizing the influence of solvents on enzyme stability. The enzyme preparations showed a markedly higher thermostability in dry solvents having log P values >0.7 than in less hydrophobic solvents.Also the operational stability was better in the more hydrophobic solvents. The amount of water added to the enzyme preparations greatly influenced the initial reaction rates. For some solvents optimal water contents were determined. The thermostability decreased with increasing water content.The observations are summarized in the conclusion that more hydrophobic solvents are preferable to less hydrophobic ones. The log P value gives a good guidance when selecting an organic solvent for enzymatic conversions.     

A General and Concise Enantioselective Divergent Approach to 13‐Alkyl‐Substituted Ionones

A novel enantioselective divergent route to 13‐alkyl derivatives of α‐ and γ‐ionone, important components of perfumes and fragrances, is reported. This relatively short and convenient methodology takes advantage of the use of a common intermediate, easily obtained from highly enantiomerically enriched (S)‐α‐ionone, which avoids the separate installation of the butenone side chain at C(6) for each analog. Olfactory evaluation of synthesized compounds reconfirmed the influence of the hydrophobic interactions of alkyl substituents at C(5) with olfactory receptors (ORs) in the chemoreception of ionones, and suggested that a synperiplanar orientation of C(13) and the lateral chain is the better geometry fitting OR's cavity.     

Hydrophobicity and surface electrostatic charge of conidia of the mycoparasitic <Emphasis Type="Italic">Trichoderma</Emphasis> species

The present investigation was done to understand the fungal-fungal interactions mechanisms based on level of nonspecific adhesion of a potential fungal mycoparasite (Trichoderma) to their fungal host (Macrophomina phaseolina). The relative cell surface hydrophobicity (CSH) and cell surface electrostatic charge (CSEC) of 29 isolates of Trichoderma species, analyzed by bacterial adhesion to hydrocarbon (BATH), hydrophobic interaction chromatography (HIC), microelectrophoresis and contact angle, revealed a large degree of variability. CSH and CSEC of conidia depended on culture age, pH and temperature. Maximum CSH and CSEC were recorded in 25–28 °C range, and both declined significantly with increasing temperature. Isolate Trichoderma hazianum (Th)-23/98 expressed surface hydrophobicity at 25–28 °C and hydrophilicity at 40 °C. Surface hydrophobicity of the isolate was susceptible to various proteases (trypsin, pepsin, proteinase k and a-chymotrypsin) and inhibitors (SDS, mercaptoethanol and Triton X-100) and a significant reduction in CSH was recorded in hydrophobic conidia. Hydrophilic conidia remained more or less unaffected by such treatments. SDS-PAGE analysis of the hydrophobic and hydrophilic conidia exhibited several protein bands in the 25 to 61 kDa range. However, each protein population contained one protein that was not observed in the other population. For hydrophobic conidia, the unique protein had an apparent molecular mass of 49 kDa, while the unique protein associated with hydrophilic conidia had a molecular mass of 61 kDa. Our findings suggest that CSH and CSEC of mycoparasitic Trichoderma may contribute to non-specific adhesion on to the sclerotial surfaces of Macrophomina phaseolina that may be influenced by growth and environmental conditions.     

Purification and Partial Amino Acid Sequence of Brevicin 27, a Bacteriocin Produced by Lactobacillus brevis SB27

Brevicin 27, a bacteriocin produced by Lactobacillus brevis SB27, is inhibitory mainly against closely related Lactobacillus brevis and Lactobacillus büchneri strains. It was purified from the culture supernatant by a four-step purification procedure including ammonium sulfate precipitation, cation exchange, hydrophobic interaction, and reverse-phase, high performance liquid chromatographies. The purified bacteriocin was subjected to mass spectrometry, amino acid composition analysis, and sequencing by Edman degradation. It was shown to be an about 5200-Da basic protein containing a high proportion of lysine and of hydrophobic amino acids. The partial N-terminal amino acid sequence (25 residues) was unique when compared with the Protein Data Bank (PDB), Swiss Prot, and Protein Information Resource (PIR) data banks and to the translated Gen Bank. Received: 24 July 1996 / Accepted: 10 September 1996     

The C-terminal extrahelical peptide of type I collagen and its role in fibrillogenesis in vitro: effects of ethylurea

Ethylurea was used to weaken hydrophobic interactions during collagen fibrillogenesis in vitro. Intact and enzyme-digested type I collagen was studied. In all preparations, ethylurea decreased the extent and rate of fibril formation, inhibition being greatest in the enzyme-digested collagens. With intact collagen (and probably also with carboxypeptidasedigested collagen), there was no evidence the ethylurea altered the mechanism of fibril growth; in pepsin-digested collagen, however, the growth mechanism was altered by ethylurea, possibly reflecting a conformational change of the “hydrophobic cluster” in the C-terminal peptide. Such a structural change could occur in a hydrophobic environment once the distal portion of the C-terminal peptide (presumed to be essential for its structural stability) is removed by pepsin. The results further emphasize the importance of hydrophobic interactions in collagen fibril nucleation and growth in vitro.     

Isolation of two arginine vasopressin-like factors from ganglia of Locusta migratoria

Tissues of Locusta migratoria are known to contain a material which crossreacts with an antibody against arginine vasopressin (AVP), and this factor has been correlated with the diuretic hormone of this species. In this paper, we report the isolation of two AVP-like factors from suboesophageal ganglia and thoracic ganglia of Locusta migratoria. The less abundant, more hydrophobic of these AVP-like factors shows diuretic activity in an assay where excretion of amaranth dye from Locusta migratoria hemolymph is used as the scoring criterion. After extracting a total of ～ 51,000 ganglia with an acidic solvent, the crude extract was prepurified by batch adsorption/elution from disposable reversed-phase cartridges. The prepurified extract was then sequentially purified by reversed-phase liquid chromatography using solvent programs of substantially differing selectivity. The more abundant factor was isolated to apparent homogeneity in three steps, while the less abundant factor required four or five steps. Use of a C₄ reversed-phase column minimized losses of the minor, more hydrophobic factor.     

Using particle size analysis to determine the hydrophobicity and suspension of fungal conidia with particular relevance to formulation of biopesticide

Fungal formulations are vital for effective biopesticide development. Good formulations help to optimise field efficacy, while poor formulations result in product failure. This study aimed to produce a hydrophobicity test that would be appropriate for fungal conidia produced to a commercial quality and determine relative hydrophobicity of fungi from four different genera by using laser diffraction. A particle size analyser was used to determine the hydrophobicity of: three Metarhizium acridum samples, M. anisopliae, Beauveria bassiana, Trichoderma stromaticum, T. harzianum, T. viride and Alternaria eichhorniae conidia by suspending the conidia in three different liquids: Shellsol T (a mineral oil), water and 0.05 % Tween 80. Hydrophobicity was determined by the size of the particles formed in each of the liquids. All the Metarhizium samples were the most hydrophobic followed by B. bassiana and A. eichhorniae. The Trichoderma samples were the least hydrophobic. As a comparison, a phase exclusion assay and a salt-mediated aggregation and sedimentation (SAS) test were performed. It was not possible to get a reliable reading for the B. bassiana, A. eichhorniae and T. viride samples using the phase exclusion assay. The addition of salt in the SAS test did not affect the rate of sedimentation. It was hypothesised that conidia size affected the results of the SAS test that made A. eichhorniae the most hydrophobic conidia. Particle size analysis (PSA) was a more accurate test for comparing fungi from difference genera compared to the SAS test and phase exclusion assay. PSA was also used to test three emulsions and demonstrated that different formulations had an effect on particle size.     

Effect of some monohydric alcohols on the oxygen affinity of hemoglobin: relevance of solvent dielectric constant and hydrophobicity.

We studied the effect of methanol, ethanol, iso-propanol, and n-propanol on the reaction of hemoglobin with oxygen. The oxygen affinity was found to decrease with increasing alcohol concentration and alkyl group size; no detectable effect on Hill's constant was found. Difference spectroscopy indicated K_R not to be affected by the presence of alcohols; the lowered affinity was then attributed to an altered equilibrium between T and R conformations of hemoglobin. The results have been analyzed in such a way as to allow separation of electrostatic contributions to free energy difference between the T and R states from nonelectrostatic ones. The nonelectrostatic term has been attributed to protein–solvent hydrophobic interactions. Values of hydrophobic free energy are in good agreement with analogous data estimated by correlating different results previously reported in the literature.     

Comparative hydrocarbon utilization by hydrophobic and hydrophilic variants of Pseudomonas aeruginosa

Aims: To investigate hydrocarbon degradation by hydrophobic, hydrophilic and parental strains of Pseudomonas aeruginosa. Methods and Results: Partitioning of hydrocarbon‐degrading P. aeruginosa strain in a solvent/aqueous system yielded hydrophobic and hydrophilic fractions. Exhaustive partitioning of aqueous‐phase cells yielded the hydrophilic variants (L), while sequential fractionation of the hydrophobic phase cells yielded successive fractions exhibiting increasing cell‐surface hydrophobicity (CSH). In hydrocarbon adherence assays (bacterial attachment to hydrocarbon), L had a value of 20%, which increased from 61·7% in first hydrophobic fraction (H₁) to 72·2% in the third (H₃). Crude oil degradation by L was 70%, but increased from 82% in H₁ to 93% in H₃. L variant produced most exopolysaccharides and reduced surface tension from about 73 to 49 mN m^?1. Rhamnolipid production was highest in L, but was not detected in all crude oil cultures. Conclusions: Hydrophobic subpopulations of hydrocarbon‐degrading P. aeruginosa exhibited greater hydrocarbon‐utilizing ability than hydrophilic ones, or the parental strain. Significance and Impact of the Study: Results demonstrate that a population of P. aeruginosa consists of cells with different CSH which affect hydrocarbon utilization. This potentially provides the population with the capacity to utilize different hydrophobic substrates found in petroleum. Judicious selection of such hydrophobic subpopulations can enhance hydrocarbon pollution bioremediation.     

Purification and characterization of enolase fromEscherichia coli

A method for the purification of enolase (EC 4.2.1.11) from an overproducing strain ofEscherichia coli JA 200 pLC 11–8 is described. The procedure included treatment of the crude sonic extract with protamine sulfate, followed by ammonium sulfate fractionation, hydrophobic interaction chromatography with phenyl Sepharose, HPLC ion exchange chromatography with a DuPont Sax column, and HPLC hydrophobic interaction chromatography with a Bio-Rad 5-PW column. The enzyme was purified to homogeneity as determined by silver staining of 10% sodium dodecylsulfate polyacrylamide gels. The native molecular weight ofE. coli enolase was found to be 92 kilodaltons and consisted of two subunits of identical molecular weight, 46 kilodaltons each. The isoelectric point was found to be 4.9.     

Glucoamylase structural,functional, and evolutionary relationships

To correlate structural features with glucoamylase properties, a structure-based multisequence alignment was constructed using information from catalytic and starch-binding domain models. The catalytic domain is composed of three hydrophobic folding units, the most labile and least hydrophobic of them being missing in the most stable glucoamylase. The role of O-glycosylation in stabilizing the most hydrophobic folding unit, the only one where thermostabilizing mutations with unchanged activity have been made, is described. Differences in both length and composition of interhelical loops are correlated with stability and selectivity characteristics. Two new glucoamylase subfamilies are defined by using homology criteria. Protein parsimony analysis suggests an ancient bacterial origin for the glucoamylase gene. Increases in length of the belt surrounding the active site, degree of O-glycosylation, and length of the linker probably correspond to evolutionary steps that increase stability and secretion levels of Aspergillus-related glucoamylases. Proteins 29:334–347, 1997. © 1997 Wiley-Liss, Inc.