Acid Chain Length Research Articles

The chemical modification of a range of starches under aqueous reaction conditions

A series of starch esters with different side-chain lengths and moderate DS-values was prepared and studied. The esters were prepared by acylation of the gelatinised starch with the appropriate acid chloride in 2.5 M aqueous sodium hydroxide (NaOH) solution, which represents an economical and facile method for the preparation of esterified starches. The alkali solution acted as the medium for the derivatisation and ensured uniform substitution by enhancing solubility of the starch and accessibility of the reagent. Successful esterification was limited to acid chlorides containing between six and 10 carbon atoms. Shorter or longer chain-length acid chlorides did not react under these conditions to form esters, as confirmed by FT-IR spectroscopic and elemental analyses, as well as by intrinsic viscosity analysis.

Mechanochemical preparation of hydrogen-bonded adducts between the diamine 1,4-diazabicyclo[2.2.2]octane and dicarboxylic acids of variable chain length: an X-ray diffraction and solid-state NMR study.

Mechanical mixing of solid dicarboxylic acids of variable chain length HOOC(CH(2))(n)COOH (n = 1-7) with solid 1,4-diazabicyclo[2.2.2]octane generates the corresponding salts or co-crystals of the formula [N(CH(2)CH(2))(3)N]-H-[OOC(CH(2))(n)COOH] (n=1-7). Preparation of the same systems from solution has been instrumental for a full characterization of the mechanochemical products by means of single-crystal and powder-diffraction X-ray analyses, as well as by solid-state NMR. The acid-base adducts, whether involving proton transfer from the COOH group to the N-acceptor, that is having ((-))O...H-N((+)) interactions, or the formation of neutral O-H...N hydrogen bonds, show a melting point alternation phenomenon analogous to that shown by the neutral carboxylic acids. The carbon chemical shift tensors of the COOH group obtained from the sideband intensity of low speed spinning NMR spectra provide a reliable criterion for assigning the protonation state of the adducts.

Fats and food intake.

Given the global rates of obesity and the potential link to dietary fat intake, understanding the role of fat in the regulation of food intake is critical. Some short-term, laboratory-based studies demonstrate poor compensation for manipulation of fat content, leading to passive overconsumption, while others demonstrate compensation to levels similar to other macronutrients. The observation of compensation in the short term does not concur with long-term rates of obesity increase. This review discusses factors that may explain at a physiological level these discrepancies, in particular fat structure, dietary adaptation, and palatability. Medium-chain triglycerides have been demonstrated to be more satiating and promote weight loss. Recent data suggest different gastrointestinal transduction mechanisms elicit vagal afferent firing for fatty acids of different chain length. Dietary adaptation to fat can influence the sensitivity of the feedback response, which appears to be nutrient specific and relate to gastric emptying rates and hormonal feedback. Fat content has been found to influence palatability of foods. Recently it has been demonstrated that increasing palatability can partially override the satiating effects of covertly manipulated macronutrient preloads. Recent data suggest that hormonal influences may also affect the palatability response. It is becoming increasingly clear that although energy density of diets is a major factor determining intake, macronutrient structure, subject, dietary and taste differences can all play an important modulatory influence on the final response on food intake. Further understanding of these factors and interactions may provide strategies to help aid weight regulation.

Synthesis of Benzo[a]pyren‐6‐yl‐Substituted Carboxylic Acids.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Exposure to fatty acids modulates interferon production by intraepithelial lymphocytes

Intraepithelial lymphocytes (IELs) play important roles in intestinal mucosal immunity. Although fatty acids are known to modulate the functions of immune effector cells, there has been no information about how fat exposure affects immunological function of IELs. In this study, we examined how fatty acids of various chain lengths modulate the production of interferon (IFN)-γ by IELs stimulated with T-cell receptor (TCR) or interleukin (IL)-12/IL-18. IELs isolated from the small intestine of BALB/c mice were stimulated with plate-coated anti-CD3 monoclonal antibody (mAb) or IL-12/IL-18. They were coincubated in microtiter plates for 3 days with various concentrations of fatty acid micelles. We used arachidonic acid, linoleic acid, and oleic acid as long-chain fatty acids, and used octanoic acid as a medium-chain fatty acid. IFN-γ in the supernatants were measured by ELISA, and the expression of IFN-γ mRNA in IELs was determined by RT-PCR. Significant production of IFN-γ from IELs was observed after anti-CD3 mAb stimulation. The combination of IL-12 and IL-18 induced significant levels of IFN-γ production without TCR stimulation. Increased IFN-γ mRNA was also observed after anti-CD3 or IL-12/IL-18 stimulation. Long-chain fatty acids dose-dependently inhibited the stimulated-IFN-γ production at concentrations greater than 10 μM, but the medium-chain fatty acid did not cause any significant changes in IFN-γ production. IFN-γ production from γδ IELs was very low compared with αβ IELs, however, both populations showed similar attenuating patterns when treated with long-chain fatty acids. There is a possibility that the exposure of IELs to intraluminal fatty acids significantly modifies the immune function of intestinal mucosa.

Anhydride prodrugs for nonsteroidal anti-inflammatory drugs.

The objective of this study was to synthesize anhydride prodrugs for prolong action to shield the carboxylic acid group from irritative effects and to temporary hydrophobize the drug so that it becomes accessible to aqueous media when the anhydride residue is hydrolyzed. Ibuprofen, a nonsteroidal anti-inflammatory agent, was used as a representative drug for anhydride derivatization. Mixed anhydrides of ibuprofen with fatty acids of different chain length were prepared by reacting acid chloride derivatives with the corresponding acid in the presence of acid acceptor and two-phase reaction. Mixed anhydrides were also prepared by dehydration reaction using acetic anhydride and anhydride interchange of symmetric anhydrides. The analgesic effects of mixed anhydride prodrugs were tested using nonsteroidal anti-inflammatory drug rat paw edema model. In vitro degradation of mixed anhydrides and drug release were monitored by high-performance liquid chromatography. Ibuprofen was bound to aliphatic and aromatic acids via an anhydride bond in high reaction yields (>85%) with high mixed anhydride content (>80%). The mix anhydride was purified by chromatography and stored at 4 degrees C to minimize conversion into the symmetric anhydride. These anhydride derivatives hydrolyzed at different time intervals depending on the hydrophobicity of conjugated acid. In vivo testing of the ibuprofen anhydride derivatives for analgesic effect indicated an extended action of the drug for over 24 h as a function of the fatty acid chain length. This study demonstrates the promise of anhydride prodrugs for extending drug action and shielding the carboxylic acid group.

The structure of organic langmuir films on liquid metal surfaces

Langmuir films (LFs) on water have long been studied for their interest for basic science and their numerous applications in chemistry, physics, materials science and biology. We present here Å-resolution synchrotron X-ray studies of the structure of stearic acid LFs on a liquid mercury surface. At low coverage, ⩾110 Å 2/mol, a 2D gas phase of flat-lying molecules is observed. At high coverage, ⩽23 Å 2/mol, two different hexatic phases of standing-up molecules are observed. At intermediate coverage, 52⩽ A⩽110 Å 2/mol, novel single- and double-layered phases of flat-lying molecular dimers are found, exhibiting a 1D in-layer order. Such flat-lying phases were not hitherto observed in any LF. Measurements on LFs of fatty acids of other chain lengths indicate that this structure is generic to chain molecules on mercury, although the existence of some of the flat-lying phases, and the observed phase sequence, depend on the chain length. Organic LFs on Hg, and in particular the new flat-lying phases, should provide a broader nano-structural tunability range for molecular electronic device construction than most solid-supported self-assembled monolayers used at present.

Microwave Irradiation Technique for Synthesis of Dialkyl Dithiophosphoric Acids

Microwave heating technique was applied to the preparation of dialkyl dithiophosphoric acids from the reaction of alcohol with phosphorus pentasulphide. A microwave oven (CEM-MDS 2000) was utilized to determine the preparation conditions for the best yield of dialkyl dithiophosphoric acids under atmospheric pressure at various times and power. Six different (C 4 -C 9 ) chain-length of dialkyl dithiophosphoric acids were studied. All experiments were performed in an open Teflon (poly-tetrafluoroethylene) vessel. The results obtained showed that the reaction of dialkyl dithiophosphoric acids can be achieved more rapidly using microwave heating than using conventional procedures.

Thermodynamic properties of (an ethyl ester + a branched alkane). XV. HmE and VmE values for (an ester + an alkane)

This paper presents H m E and V m E measurements taken at T=298.15 K and at the atmospheric pressure of 100.65 kPa for 22 binary mixtures composed of one of four ethyl esters (methanoate, ethanoate, propanoate, and pentanoate) and one of seven alkane isomers, C 6 to C 8. The H m E of four binary mixtures of ethyl propanoate and pentanoate with n-C 6 and n-C 8, measured at the conditions mentioned above are also presented. The results indicate that the mixing process is endothermic for all the mixtures, with H m E varying regularly with the components chain length, increasing with alkane chain length and decreasing with the acid chain length in the ester. The V m E values vary also regularly in a manner similar to that of the H m E slight contractions are observed for (ethyl pentanoate + 2-methylpentane). A new form of a polynomial equation used previously was employed to correlate the experimental values of the excess quantities and yielded good results in all cases. In addition, the behaviour of these mixtures is explained in terms of an interaction model proposed in previous work.

Multiple mutagenesis of non-universal serine codons of the Candida rugosa LIP2 gene and biochemical characterization of purified recombinant LIP2 lipase overexpressed in Pichia pastoris.

The 17 non-universal serine codons (CTG) in the Candida rugosa LIP2 gene have been converted into universal serine codons (TCT) by overlap extension PCR-based multiple site-directed mutagenesis. An active recombinant LIP2 lipase was overexpressed in Pichia pastoris and secreted into the culture medium. The recombinant LIP2 showed distinguishing catalytic activities when compared with recombinant LIP4 and commercial C. rugosa lipase. The purified enzyme showed optimum activity at pH 7 and a broad temperature optimum in the range 30-50 degrees C. The enzyme retained 80% of residual activity after being heated at 70 degrees C for 10 min. Recombinant LIP2 demonstrated high esterase activity towards long-chain (C12-C16) p-nitrophenyl esters. Tributyrin was the preferred substrate among all triacylglycerols tested for lipolysis. Among cholesteryl esters, LIP2 showed highest lipolytic activity towards cholesteryl laurate. The esterification of myristic acid with alcohols of various chain lengths showed that the long-chain n-octadecanol (C18) was the preferred substrate. In contrast, the esterification of n-propanol with fatty acids of various chain lengths showed that the short-chain butyric acid was the best substrate. From comparative modelling analysis, it appears that several amino acid substitutions resulting in greater hydrophobicity in the substrate-binding site might play an important role in the substrate specificity of LIP2.

The Influence of Fatty Acids and Humidity on Friction and Adhesion of Hydrophilic Polymer Surfaces

Monolayers of saturated fatty acids of different chain lengths and of 9-cis-octadecenoic acid were physisorbed onto regenerated cellulose surfaces to study their effect on friction and adhesion. Lateral and normal force measurements on these surfaces were carried out at different humidities using an atomic force microscope with chemically functionalized silicon nitride cantilevers. Friction and adhesion of clean cellulose increased significantly with humidity. Adhesion forces at high humidity were predicted well by theory that accounted for the effect of the Laplace pressure due to capillary condensation. The magnitude of friction and adhesion and their dependence on humidity decreased with increasing hydrophobicity of the contacting surfaces. Friction of cellulose surfaces impregnated with different saturated fatty acids decreased sharply from a high level to a low level at a carbon chain length above 14 carbon atoms. Contact angle data indicated that only saturated fatty acids with 16 carbon atoms or more in the carbon chain formed vertically oriented monolayers on cellulose. Our results suggest that friction of hydrophilic polymer surfaces under ambient conditions is greatly influenced by capillary condensation. Furthermore, lubrication by fatty acids is achieved through the formation of vertically oriented, hydrophobic monolayers that can withstand the normal and shear stresses during sliding and increase the hydrophobicity of the polymer surface, thereby decreasing the degree of capillary condensation.

Obesity in children and adolescents worldwide: current views and future directions--Working Group Report of the First World Congress of Pediatric Gastroenterology, Hepatology, and Nutrition.

Obesity in children and adolescents worldwide: current views and future directions--Working Group Report of the First World Congress of Pediatric Gastroenterology, Hepatology, and Nutrition.

Effects of High Salt Concentrations on the Micellization of Octyl Glucoside: Salting-Out of Monomers and Electrolyte Effects on the Micelle−Water Interfacial Tension1

The effects of two added electrolytes up to high concentrations, 0−4 M NaCl and 0−6.6 M LiCl, on the critical micellization concentration (cmc) of octyl glucoside (OG), a nonionic surfactant, in aqueous solution have been measured. The fluorescence probe 6-p-toluidino-2-naphthalene sulfonate was used to determine the cmc values. Log cmc values were found to vary linearly with the molar electrolyte concentration, CS, up to the highest concentrations. A theoretical approach based on the salting-out of the monomeric chain, presented in 1965, has been expanded by incorporating an additional effect of added electrolytes on the interfacial tension of the micelle−water interface. A group additivity relationship for the salting-out of hydrocarbon chains, also proposed in 1965, has been shown to give a good account of the salting-out coefficients of some hydrocarbons, primary alcohols, and methyl esters of carboxylic acids of different chain lengths obtained from literature data. Salting-out coefficients for the o...

Effect of fatty acid chain length on initial reaction rates and regioselectivity of lipase-catalysed esterification of disaccharides

In a reaction medium mixture of 9:11 t-BuOH and pyridine (v/v) the effect of fatty acid chain length (C-4–C-12) on C. antarctica lipase B (Novozym 435, EC 3.1.1.3) catalysed esterification was studied. α and β maltose 6′- O-acyl esters in an anomeric molar ratio of 1.0:1.1 were synthesised independently of the chain length, but the initial specific reaction rate increased with decreasing chain length of the acyl donor. The product yield followed the same trend with a lauryl ester yield of 1.1% (mol/mol) and a butyl ester yield of 27.6% (mol/mol) after 24 h of reaction. With sucrose as the acyl acceptor the 6′- O-acyl and 6- O-acyl monoesters were formed with fatty acids of chain length C-4 and C-10 while the 6′,6- O-acyl diester was formed only with butanoic acid (C-4:0) as acyl donor. The 6′- O-acyl and 6- O-acyl monoesters and the 6′,6- O-acyl diester of butanoic acid were produced in a molar ratio of 1.0:0.5:0.2 and with decanoic acid (C-10:0) the 6′- O-acyl and 6- O-acyl monoesters were formed in the ratio of 1.0:0.3. The highest initial reaction rate and yield were obtained with the shortest chain length of the acyl donor. Initial reaction rates and ester yields were affected by the solubility of the disaccharide, with higher reaction rates and yields with maltose than with sucrose, while no formation of esters were observed with either cellobiose or lactose as acyl acceptors.

Inhibition of Hyaluronidases and Chondroitinases by Fatty Acids

The inhibitory effects of various fatty acids on three hyaluronidases (h-ST, h-SH and h-SD) and four chondroitinases (c-ABC, c-B, c-ACI and c-ACII) were examined, and their structure-activity relationships and mechanism of action were studied. The fatty acids used in this experiment showed various inhibitory activities against the enzymes. None of the fatty acids did not inhibit h-ST and h-SH. The saturated fatty acids (C 10:0 to C 22:0) showed very weak or no inhibition against h-SD, c-ABC, c-B, c-ACI and c-ACII but the unsaturated fatty acids (C 14:1 to C 24:1) with one double bond strongly inhibited the enzymes, and the inhibitory potency increased with increase in carbon chain length of the fatty acids. In contrast, the increase in number of double bonds caused a decrease in inhibitory potency against the enzymes. The position of the double bond and the stereochemistry of the cis - trans form of oleic acid (C 18:1) did not influence the inhibitory potency against the enzymes. Carboxyl and hydroxyl groups in the fatty acid molecule were concerned in the inhibition of c-ACI. Among the fatty acids, eicosatrienoic acid (C 20:3) generally inhibited h-SD, c-ABC, c-B and c-ACI, and nervonic acid (C 24:1) was a potent inhibitor of c-ACII, and the fatty acids inhibited the enzymes in a noncompetitive manner.

Fatty acid signalling in a mouse enteroendocrine cell line involves fatty acid aggregates rather than free fatty acids.

Fatty acids induce cholecystokinin (CCK) secretion both in humans and from murine enteroendocrine cell lines. In both cases, only fatty acids above a critical acyl chain length (C(10)) are capable of inducing a response. Using the enteroendocrine cell line STC-1, the aim of this study was to determine whether this acyl chain length dependency is related to the fact that longer chain fatty acids are relatively insoluble in aqueous solutions and, if so, whether it is insoluble aggregates of fatty acids rather than free fatty acids which evoke CCK secretion. Solutions of fatty acids (chain length C(8)-C(14)), which were judged by filtration and Zeta sizer measurement to contain no fatty acid aggregates, never evoked CCK secretion from STC-1 cells. Filtering fatty acid solutions (of chain length C(10), C(12) and C(14)) through polytetrafluoroethylene (PTFE) filters (0.45 microm pore size) revealed a narrow concentration range for each acid over which the amount of fatty acid removed from the solution increased sharply due to the formation of fatty acid aggregates. Filtration experiments, in which suspensions of C(10), C(12) and C(14) fatty acids were passed through pore sizes of 0.2, 0.45 or 1.2 microm, suggested that STC-1 cells did not respond to fatty acid aggregates of greater than 1.2 microm, while at least 50 % of the CCK response was mediated by aggregates which were smaller than 0.45 microm. Fatty acids induce CCK secretion from STC-1 cells by elevating intracellular Ca(2+) concentration ([Ca(2+)](i)). We therefore measured the effects on [Ca(2+)](i) of filtered C(10), C(12) and C(14) fatty acids. In all cases, [Ca(2+)](i) responses were closely correlated with CCK secretion. Interestingly, while filtrates of fatty acid solutions evoked CCK secretion and elevated [Ca(2+)](i), freshly prepared solutions of fatty acids at the same concentration as the filtrates did not. This suggested that fatty acid aggregates were not in equilibrium with the solvent after filtration. The observation that the ability of C(10), C(12) and C(14) filtrates to elevate [Ca(2+)](i) decayed with time was consistent with this hypothesis. Furthermore, sonication of the filtrates abolished their ability to elevate [Ca(2+)](i). These data further suggest that it is a physical property of the fatty acid solution (the presence of insoluble fatty aggregates) which is responsible for the observed cellular responses. We conclude that Ca(2+) mobilisation and CCK secretion in STC-1 cells is driven by a signal transduction mechanism that senses insoluble fatty acid aggregates, rather than free fatty acids in solution.

Surface characterization and platelet adhesion studies of aliphatic polyurethanes grafted by fluorocarbon oligomers: effect of fluorocarbon chain length and carboxylic acid group.

The surfaces of aliphatic polyurethane films, which were synthesized by 1,6 hexamethylene diisocyanate, poly(tetramethylene glycol) and 1,4 butanediol, were modified by grafting different chain length of fluorocarbon oligomers. The fluorocarbon oligomers on polyurethane surfaces were terminated with trifluorocarbon or carboxylic acid functionality. The alkyl groups were also grafted onto polyurethane surfaces for comparison. The surface characterization and platelet-contacting property were studied using electron spectroscopy for chemical analysis (ESCA), static contact angle analysis and in vitro platelet adhesion experiments. The effects of fluorocarbon oligomers and their terminal functionalities are discussed. The ESCA results demonstrate the fluorocarbon enrichment at the outmost layer in fluorocarbon oligomer grafted polyurethanes. The fluorocarbon content at the surface increases with increasing the chain length of fluorocarbon oligomers. The fluorocarbon oligomer grafted polyurethanes exhibit highly hydrophobic surfaces, while alkyl groups grafted polyurethanes show relatively hydrophobic surfaces compared with the untreated polyurethane. The in vitro platelet adhesion experiments indicated that the fluorocarbon oligomer and carboxylic acid functionality significantly reduced the number and the degree of activation of the adherent platelets.

Effect of the Length of the Hydrocarbon Chain of Adsorbed Aliphatic Acids and Alcohols on the Electron Transfer Probability

The kinetics of redox reactions of hemin adsorbed over a monolayer of long-chain aliphatic alcohols, such as cetyl alcohol (C16) and stearyl alcohol (C18), and stearic (C18), behenic (C22), and melissic (C30) acids is studied. The reaction inhibition on an alcohol monolayer (0.34 orders of magnitude per methylene group) is close to that reported in the literature. The inhibition on an acid monolayer is substantially smaller (0.2 to 0.07 orders), which is attributed to irregularity of the structure of the monolayer of carboxylic acids caused by the dissociation of carboxyl groups, especially in alkaline solutions. Violation of a regular structure of an acid monolayer is confirmed by a considerable irreversible increase in the electrode capacitance in alkaline solutions and by a decrease in the ohmic resistance of a monolayer of the longest saturated acid, i.e. triacontanoic acid. For a regular monolayer structure, when the length of an extended hydrocarbon chain defines the barrier thickness (alcohols), experimental data accord with predictions of the “superexchange” theory, which holds that the probability of a long-distance electron transfer depends on the length of the chain of covalent bonds over which the superexchange occurs. If the film structure is irregular (film thickness decreases with increasing hydrocarbon chain length (acids)), the packing of these bonds becomes essential, which allows the electron not to pass over all the bonds but to hop onto a nonbonded chain link nearby. The obtained data indicate that the electron transfer probability is defined by the electron's path, rather than by the barrier's geometrical thickness.

Organo-geochemical and stable isotope indicators ofenvironmental change in a marl lake, Malham Tarn, North Yorkshire,U.K.

Sediments of the marl lake Malham Tarn located in NW Englandpreserve an environmental record since 12 Ka. Eight Holocene pollen zones wereidentified, and the δ13C of total organic carbon (TOC) showsthree stratigraphic divisions. The basal clay unit and overlayingsand/clay/marl unit have δ13C of −24‰which decreases at the base of the principal marl unit to a mean value around−30‰, whilst the topmost black marl unit δ13Cincreases to −28‰ at the surface. Representative samples of theseunits were selected for analysis of n-alkanes andn-fatty acids and their δ13C.Samples of modern Chara and peat were analysed forcomparison. The clay unit has a minor contribution of redeposited matureorganic matter and autochthonous algae, the marl unit a high contribution ofChara, and the dark marl unit has a high contribution fromhigher plants. Compound-specific δ13C revealssystematic differences between alkanes and fatty acids of different chainlength. The major shift in δ13C in the short and medium chainfatty acids are probably due to the decreasing influence of carbonate rockflour as source of DIC. The major shift in δ13C in the longchain n-fatty acids andn-alkanes could reflect the lower atmosphericCO2 concentration at Last Glacial. The negative shift of short chainfatty acids in organic rich dark marls reflects introduction of detrital peatinto the lake. The δ13C results show a dramatic change fromdominance of autochthonous plus eroded sources up to Pollen Zone IV, then slowcolonisation of the hinterland by higher plants, followed by constantChara contributions throughout the deposition of the marl,and a further increase of higher plant material after the rise in water levelin 1791.

N-terminal acylation of somatostatin analog with long chain fatty acids enhances its stability and anti-proliferative activity in human breast adenocarcinoma cells.

The anti-proliferative activity of the somatostatin analog RC-160 is limited by its short serum half life. To circumvent this limitation, fatty acids of chain lengths ranging from 4 to 18 were individually conjugated to the N-terminal residue of RC-160. The lipophilized derivatives of RC-160 were synthesized, purified and characterized. The anti-proliferative activity of lipophilized-RC-160 on the human breast carcinoma cell line MCF-7, was evaluated in vitro. The long chain lipopeptides like pamitoyl-RC-160 exhibited significantly higher anti-proliferative activity on MCF-7 cells (p<0.001), relative to RC-160. The affinity of RC-160 towards somatostatin receptors remained unaltered by pamitoylation. However, the observed increase in bioactivity was manifested within an optimum range of chain length of the lipoppetide. Increasing the peptide hydrophobicity beyond this range reduced the bioactivity of lipophilized-RC-160. Accordingly, stearoyl-RC-160, manifested lower anti-neoplastic activity and receptor affinity relative to pamitoyl-RC-160 and RC-160 itself. The signaling pathways underlying the antineoplastic activity of these lipopeptides were found to be similar to RC-160. Pamitoyl-RC-160 displayed enhanced inhibition of protein tyrosine kinase activity and intracellular cAMP levels in MCF-7 cells, relative to butanoyl-RC-160 or RC-160 itself. Pamitoyl-RC-160 also displayed greater resistance towards trypsin and serum degradation than RC-160. Lipophilization of RC-160 with long chain fatty acids like pamitic acid improves its stability and anti-proliferative activity, thereby improving the scope of enhancing its therapeutic index. However, the optimization of peptide hydrophobicity seems to be a crucial factor governing the efficacy of bioactive lipopeptides.