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PubMed1999

Physico-chemical characterization of insulin-loaded poly(isobutylcyanoacrylate) nanocapsules obtained by interfacial polymerization.

Insulin could be encapsulated very efficiently in oily containing poly(isobutylcyanoacrylate) nanocapsules obtained by interfacial polymerization. In addition, these nanocapsules showed unexpected biological activity after intragastric administration. The hypoglycemic effect was characterized by a lag time period of 2 days and a prolonged effect over a period of 20 days. To explain, the high encapsulation rate of insulin achieved in these nanocapsules and the biological effect, this work was focused on the characterization of the nanocapsules and on the study of the mechanism of nanocapsule formation. Results showed that insulin was found unmodified during the nanoencapsulation process. This was due to the large amount of ethanol used in the preparation of the nanocapsules that initiated the polymerization of isobutylcyanoacrylate preserving the peptide from a reaction with the monomer. Results also showed that insulin was located inside the core of the nanocapsules and not simply adsorbed onto their surface.

Bucrylate↗
PubMedDate not supplied

Protein-lipid interactions studied with designed transmembrane peptides: role of hydrophobic matching and interfacial anchoring.

Biological membranes are characterized by a heterogeneous composition, which is not only manifested in the wide variety of their components, but also in aspects like the lateral organization, topology, and conformation of proteins and lipids. In bringing about the correct membrane structure, protein-lipid interactions can be expected to play a prominent role. The extent of hydrophobic matching between transmembrane protein segments and lipids potentially constitutes a versatile director of membrane organization, because a tendency to avoid hydrophobic mismatch could result in compensating adaptations such as tilt of the transmembrane segment or segregation into distinct domains. Also, interfacial interactions between lipid headgroups and the aromatic and charged residues that typically flank transmembrane domains may act as an organizing element. In this review, we discuss the numerous model studies that have systematically explored the influence of hydrophobic matching and interfacial anchoring on membrane structure. Designed peptides consisting of a polyleucine or polyleucine/alanine hydrophobic stretch, which is flanked on both sides by tryptophan or lysine residues, reflect the general layout of transmembrane protein segments. It is shown for phosphatidylcholine bilayers and for other model membranes that these peptides adapt a transmembrane topology without extensive peptide or lipid adaptations under conditions of hydrophobic matching, but that significant rearrangements can result from hydrophobic mismatch. Moreover, these effects depend on the nature of the flanking residues, implying a modulation of the mismatch response by interfacial interactions of the flanking residues. The implications of these model studies for the organization of biomembranes are discussed in the context of recent experiments with more complex systems.

Animals↗
PubMed2000

Fluorocholesterols, in contrast to hydroxycholesterols, exhibit interfacial properties similar to cholesterol.

We used an automated Langmuir-Pockels surface balance to characterize the air-water interfacial properties of cholesterol (CH) and its derivatives with hydrophilic OH and F substitutions at isologous sites on the sterol body or side chain. We studied 6-fluorocholesterol, 25-fluorocholesterol, 25,26,26,26,27,27,27-heptafluorocholesterol, 7alpha-hydroxycholesterol, 7beta-hydroxycholesterol, 25-hydroxycholesterol and 27-hydroxycholesterol, alone and in mixtures with 1-palmitoyl-2-oleoyl-sn-3-glycero-phosphocholine (POPC). Pressure;-area isotherms of the fluorocholesterols were essentially indistinguishable from CH and all condensed POPC monomolecular layers (monolayers) to variable degrees. Both nucleus-substituted hydroxycholesterols formed expanded monolayers, with lift-offs from baseline 22-26 A(2)/molecule larger than CH, suggesting interfacial tilting; furthermore, in binary mixtures, they condensed POPC monolayers less than CH. In contrast, the side chain hydroxylated CHs were oriented horizontally in the interface at large molecular areas, and became vertical below 140 A(2)/molecule with the side chain-OH rather than 3-OH group anchored in the subphase, as evidenced by low collapse pressures and smaller molecular areas than CH. Both side chain hydroxycholesterols expanded POPC monolayers at molar ratios <30%, but induced condensation with higher ratios, suggesting that OH-acyl chain (POPC) repulsion is superceded at higher mole fractions by lateral phase separation and intersteroidal H-bonding. These studies predict that fluorocholesterols should exhibit intramembrane spatial occupancy nearly identical to CH, whereas nucleus and especially side chain hydroxycholesterols will perturb membrane lipid packing notably.

Cholesterol↗
PubMed2002

Interfacial domains in Sindbis virus 6K protein. Detection and functional characterization.

Alphavirus 6K is a short, constitutive membrane protein involved in virus glycoprotein processing, membrane permeabilization, and the budding of virus particles. The amino-terminal region that immediately precedes the transmembrane anchor contains a conserved sequence motif consisting of two interfacial domains separated by Asn and Gln residues. The presence of this motif confers on the 6K pretransmembrane region the tendency to partition into the membrane interface. To study the functional importance of the interfacial sequences, three different Sindbis virus 6K variants were obtained with the following modifications: 9YLW11xAAA, 18FWV20xAAA, and 9YLW11xAAA/18FWV20xAAA. Reconstituted mutant viruses were infectious and showed no defects in glycoprotein processing, although virus budding was hampered. Single 6K expression in Escherichia coli cells showed interfacial mutants to have a diminished capacity to modify membrane permeability and to have lower toxicity. In particular, the 9YLW11xAAA/18FWV20xAAA variant was expressed at high levels and did not enhance membrane permeability significantly, although it retained its integral membrane protein condition. Parallel analyses of membrane permeabilization in baby hamster kidney cells were carried out using a Sindbis virus replicon that synthesized both capsid protein and 6K. Transfection of the construct with wild-type 6K strongly increased permeability to the antibiotic hygromycin B. Replicons encoding 6K interfacial mutants induced lower membrane permeabilization. Again, the greatest impairment was observed for the 9YLW11xAAA/18FWV20xAAA variant, permeabilization activity of which was approximately 10% that of wild-type 6K. These findings show the importance of the interfacial 6K sequence for virus budding and modification of membrane permeability.

Amino Acid Sequence↗
PubMed2005

Interfacial metal and antibody recognition.

The unique ligation properties of metal ions are widely exploited by proteins, with approximately one-third of all proteins estimated to be metalloproteins. Although antibodies use various mechanisms for recognition, to our knowledge, none has ever been characterized that uses an interfacial metal. We previously described a family of CD4-reactive antibodies, the archetype being Q425. CD4:Q425 engagement does not interfere with CD4:HIV-1 gp120 envelope glycoprotein binding, but it blocks subsequent steps required for viral entry. Here, we use surface-plasmon resonance to show that Q425 requires calcium for recognition of CD4. Specifically, Q425 binding of calcium resulted in a 55,000-fold enhancement in affinity for CD4. X-ray crystallographic analyses of Q425 in the presence of Ca(2+), Ba(2+), or EDTA revealed an exposed metal-binding site, partially coordinated by five atoms contributed from four antibody complementarity-determining regions. The results suggest that Q425 recognition of CD4 involves direct ligation of antigen by the Q425-held calcium, with calcium binding each ligating atom of CD4 with approximately 1.5 kcal/mol of binding energy. This energetic contribution, which is greater than that from a typical protein atom, demonstrates how interfacial metal ligation can play a unique role in antigen recognition.

Amino Acid Sequence↗
PubMedDate not supplied

Surface characterization of oil-containing polyterephthalamide microcapsules prepared by interfacial polymerization.

Oil-containing polyterephthalamide microcapsules were synthesized by the interfacial polymerization of an oil-soluble monomer (terephthaloyl dichloride, TDC) and a mixture of two water-soluble monomers (diethylenetriamine, DETA, and 1, 6-hexamethylenediamine, HMDA). The influence of several synthesis parameters (e.g. concentration ratio of the two amine monomers, stirring rate, concentration of the steric stabilizer PVA) on the size distribution, the membrane morphology and the electrokinetic properties of the microcapsules, was thoroughly investigated. Morphological analysis by electron microscopy showed a strong dependence of the membrane external morphology on the functionality of the water-soluble amine monomer. High stabilizer concentrations and agitation rates during emulsification favoured the production of smaller microcapsules with non-porous and rigid membranes. The electro-chemical interfacial properties of the microcapsules were investigated using a combination of potentiometric, conductimetric and electrokinetic measurements. The dependence of the mean surface charge density on pH revealed the presence of essentially two kinds of chemical groups (e.g. amino and carboxylic groups) on the microcapsule external surface. The total concentration of surface chemical groups and the isoelectric pH were measured as a function of the microcapsule synthesis conditions. Using the experimental data and an appropriate interfacial ionization model, the ratio of the surface groups densities, R = (S - COOH)/(S NH3(+) ), was evaluated and rationalized with respect to the microcapsules synthesis parameters.

Capsules↗
PubMed1998

Scanning acoustic microscopy study of titanium-ceramic interface of dental restorations.

Failures that occur in titanium-ceramic restorations are of concern in clinical dentistry. The purpose of this study was to nondestructively characterize the internal cracks and nonadherent defects at the titanium-porcelain interface using scanning acoustic microscopy. Titanium samples coated with porcelain without a bonding agent, with sputter coated palladium or chromium as an oxygen diffusion barrier on the titanium, and with the use of a porcelain bonding agent (control group) were compared. The scanning acoustic microscopy analyses were correlated with four-point bending test results. The group that was initially coated with palladium had fewer interfacial defects and a higher load to failure than the control group, and the group that did not contain the bonding agent had a higher void area and a lower load to failure than the control group. The use of chromium produced no differences from the control group. Samples after a four-point bending test were also analyzed by scanning electron microscopy. The scanning electron microscopy was not able to characterize interfacial defects at the fractured titanium-ceramic interface for some of the samples. The validity of nondestructive analysis at the Ti-ceramic interface using scanning acoustic microscopy was demonstrated in this study.

Chromium↗
PubMed2002

Comparison of helix interactions in membrane and soluble alpha-bundle proteins.

Helix-helix interactions are important for the folding, stability, and function of membrane proteins. Here, two independent and complementary methods are used to investigate the nature and distribution of amino acids that mediate helix-helix interactions in membrane and soluble alpha-bundle proteins. The first method characterizes the packing density of individual amino acids in helical proteins based on the van der Waals surface area occluded by surrounding atoms. We have recently used this method to show that transmembrane helices pack more tightly, on average, than helices in soluble proteins. These studies are extended here to characterize the packing of interfacial and noninterfacial amino acids and the packing of amino acids in the interfaces of helices that have either right- or left-handed crossing angles, and either parallel or antiparallel orientations. We show that the most abundant tightly packed interfacial residues in membrane proteins are Gly, Ala, and Ser, and that helices with left-handed crossing angles are more tightly packed on average than helices with right-handed crossing angles. The second method used to characterize helix-helix interactions involves the use of helix contact plots. We find that helices in membrane proteins exhibit a broader distribution of interhelical contacts than helices in soluble proteins. Both helical membrane and soluble proteins make use of a general motif for helix interactions that relies mainly on four residues (Leu, Ala, Ile, Val) to mediate helix interactions in a fashion characteristic of left-handed helical coiled coils. However, a second motif for mediating helix interactions is revealed by the high occurrence and high average packing values of small and polar residues (Ala, Gly, Ser, Thr) in the helix interfaces of membrane proteins. Finally, we show that there is a strong linear correlation between the occurrence of residues in helix-helix interfaces and their packing values, and discuss these results with respect to membrane protein structure prediction and membrane protein stability.

Amino Acid Sequence↗
PubMed2000

Changes in interfacial behaviour, emulsifying and foaming properties of faba bean legumin after modification with dimethylsuberimidate.

The effect of a rising rigidity and surface hydrophobicity of the 11S storage protein from faba beans--legumin--induced by chemical modification with dimethylsuberimidate (DMS) on some surface functional properties was studied. Short-time adsorption kinetics using a droplet-volume tensiometer, pressure transformation and desorption behaviour of monolayer using a film balance, and emulsifying and foaming properties were determined to characterize surface activity and interfacial film forming behaviour. Tensio-active properties at the air-water interface, i.e. decay in surface tension and pressure transformation in monolayer, were improved by modification. However, a decrease in emulsifying activity, foam capacity and foam expansion after modification of the legumin points to an overall deterioration of energy-induced film forming behaviour. The results support the view that surface activity is generally governed more by molecular flexibility than by surface hydrophobicity.

Dimethyl Suberimidate↗
PubMed2004

Interfacial properties of most monofluorinated bile acids deviate markedly from the natural congeners: studies with the Langmuir-Pockels surface balance.

We characterized the air-water interfacial properties of four monofluorinated bile acids alone and in binary mixtures with a common lecithin, 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), using an automated Langmuir-Pockels surface balance. We compared 7alpha-fluoromurocholic acid (FMCA), 7alpha-fluorohyodeoxycholic acid (FHDCA), 6alpha-fluoroursodeoxycholic acid (FUDCA), and 6alpha-fluorochenodeoxycholic acid (FCDCA) with their natural dihydroxy homologs, murocholic acid (MCA), hyodeoxycholic acid (HDCA), ursodeoxycholic acid (UDCA), and chenodeoxycholic acid (CDCA). For further comparison, two trihydroxy bile acids, 3alpha,6beta,7alpha-trihydroxycholanoic acid [alpha-muricholic acid (alpha-MCA)] and 3alpha,6alpha,7beta-trihydroxycholanoic acid [omega-muricholic acid (omega-MCA)], with isologous OH polar functions to FMCA and FUDCA were also studied. Pressure-area isotherms of MCA, HDCA, UDCA, CDCA, and FMCA displayed sharp collapse points. In contrast, FHDCA, FUDCA, and FCDCA formed monolayers that were less stable than the trihydroxy bile acids, displaying second-order phase transitions in their isotherms. All natural and fluorinated bile acids condensed mixed monolayers with POPC, with maximal effects at molar bile acid concentrations between 30 and 50 mol%. Examination of molecular models revealed that the 7alpha-F atom of the interfacially stable FMCA projects away from the 6beta-OH function, resulting in minimal steric interactions, whereas in FHDCA, FUDCA, and FCDCA, close vicinal interactions between OH and F polar functions result in progressive bulk solubility upon monolayer compression. These results provide a framework for designing F-modified bile acids to mimic or diverge from the natural compounds in vivo.

Air↗
PubMed2004

Synthesis and characterization of polyurethane and poly(ether urethane) nanocapsules using a new technique of interfacial polycondensation combined to spontaneous emulsification.

Polyurethane polymers and poly(ether urethane) copolymers were chosen as drug carriers for alpha-tocopherol. This active ingredient is widely used as a strong antioxidant in many medical and cosmetic applications, but is rapidly degraded, because of its light, heat and oxygen sensitivity. Polyurethane and poly(ether urethane)-based nanocapsules were synthesized by interfacial reaction between two monomers. Interfacial polycondensation combined with spontaneous emulsification is a new technique for nanoparticles formation. Nanocapsules were characterized by studying particle size (150-500 nm), pH, yield of encapsulation and morphologies. Polyurethanes (PUR) were obtained from the condensation of diisocyanate (isophorone diisocyanate: IPDI) and polyol: 1,2-ethanediol (EG), 1,4-butanediol (BD), 1,6-hexanediol (HD). Poly(ether urethane) copolymers were obtained by replacing diols by polyethylene glycol oligomers (PEG) M(w) 200, 300, 400 and 600. Molecular weights of di- and polyols have a considerable influence on nanocapsules characteristics cited above. The increase of molecular weight of polyols tends to increase the mean size of nanocapsules from (232+/-3)nm using EG to (615+/-39)nm using PEG 600, and led to the apparition of a population of agglomerate particles. We also noted that the yield of encapsulation increases with the increase of polyol length (from 85.6 to 92.2% w/w). Microscopic observations confirmed particle size analysis, but cannot predict the membrane structure owing the small size of the particles.

Administration, Topical↗
PubMed2007

Chemical profile of adhesive/caries-affected dentin interfaces using Raman microspectroscopy.

In clinical practice, dentists must frequently bond adhesives to caries-affected dentin substrates, but the bond that characteristically forms with these substrates does not provide the durability necessary for long-term clinical function. The purpose of this study was to characterize and compare the interfacial chemistry of adhesive with caries-affected and noncarious dentin using micro-Raman spectroscopy. The results indicated that the differences in the Raman spectra between noncarious and caries-affected dentin could not be accounted for by simple decreased mineralization. Both the structure of collagen and mineral in the caries-affected dentin has been altered by the caries process. The differences in structure and composition not only interfered with acid-etching process but also subsequent resin monomer penetration. It was shown that the interface between the adhesive and caries-affected dentin was wider and more complicated than that of the adhesive and noncarious dentin. As a result of adhesive phase separation, a structurally integrated hybrid layer did not form at the interface with either caries-affected or noncarious dentin. Using chemical imaging techniques, this study provides the direct evidence of adhesive phase separation at the interface with caries-affected dentin. Although our group previously reported adhesive phase separation at the interface with noncarious dentin, the chemistry of caries-affected dentin leads to greater variability and a more highly irregular composition along the length and breadth of the interface.

Adult↗
PubMed2004

Electrostatic effects on the yield stress of whey protein isolate foams.

The mechanisms responsible for foam structure are of practical interest within the food industry. The yield stress (tau) of whey protein isolate (WPI) foams as affected by electrostatic forces was investigated by whipping 10% (w/v) protein solutions prepared over a range of pH levels and salt concentrations. Measurements of foam overrun and model WPI interfaces, i.e. adsorption kinetics as determined via dynamic surface tension and dilatational rheological characterization, aided data interpretation. Interfacial measurements were also made with the primary whey proteins, beta-lactoglobulin (beta-lg) and alpha-lactalbumin (alpha-la). Yield stress of WPI foams was dependent on pH, salt type and salt concentration. In the absence of salt, tau was highest at pH 5.0 and lowest at pH 3.0. The addition of NaCl and CaCl2 up to 400 mM significantly increased tau at pH 7.0 but not at pH 3.0. Furthermore, at pH 7.0, equivalent molar concentrations of CaCl2 as compared to NaCl increased tau to greater extents. Salts had minimal effects on tau at pH 5.0. Comparisons with interfacial rheological data suggested the protein's capacity to contribute towards tau was related to the protein's potential at forming strong, elastic interfaces throughout the structure. The dynamic surface tension data for beta-lg and alpha-la were similar to WPI, while the interfacial rheological data displayed several noticeable differences.

Adsorption↗
PubMed2003

Exploring membrane organization and dynamics by the wavelength-selective fluorescence approach.

Wavelength-selective fluorescence comprises a set of approaches based on the red edge effect in fluorescence spectroscopy which can be used to directly monitor the environment and dynamics around a fluorophore in a complex biological system. A shift in the wavelength of maximum fluorescence emission toward higher wavelengths, caused by a shift in the excitation wavelength toward the red edge of absorption band, is termed red edge excitation shift (REES). This effect is mostly observed with polar fluorophores in motionally restricted media such as very viscous solutions or condensed phases where the dipolar relaxation time for the solvent shell around a fluorophore is comparable to or longer than its fluorescence lifetime. REES arises from slow rates of solvent relaxation (reorientation) around an excited state fluorophore which is a function of the motional restriction imposed on the solvent molecules in the immediate vicinity of the fluorophore. Utilizing this approach, it becomes possible to probe the mobility parameters of the environment itself (which is represented by the relaxing solvent molecules) using the fluorophore merely as a reporter group. Further, since the ubiquitous solvent for biological systems is water, the information obtained in such cases will come from the otherwise 'optically silent' water molecules. This makes REES and related techniques extremely useful since hydration plays a crucial modulatory role in a large number of important cellular events, including lipid-protein interactions and ion transport. The interfacial region in membranes, characterized by unique motional and dielectric characteristics, represents an appropriate environment for displaying wavelength-selective fluorescence effects. The application of REES and related techniques (wavelength-selective fluorescence approach) as a powerful tool to monitor the organization and dynamics of probes and peptides bound to membranes, micelles, and reverse micelles is discussed.

Cell Membrane↗
PubMed2003

Studies on PAN-based carbon fibers irradiated by Ar+ ion beams.

In this work, the effects of Ar+ ion beam irradiation on carbon fibers were studied using tensile and surface analytical techniques. The single-fiber pull-out test was executed in order to characterize the fiber/epoxy matrix interfacial adhesion. The Ar+ ion beam was irradiated using an ion-assisted reaction (IAR) method in reactive gas conditions under an oxygen environment with 1 x 10(16) ions/cm(2) Ar+ ion dose (ID), 6 sccm blown gas flow rate, and different ion beam energy intensities. From the experimental results, both the interfacial shear strength (IFSS) and fracture toughness (Gi) were found to increase with increasing Ar+ ion irradiation intensity. This was probably due to the fact that Ar+ ion beam irradiation on carbon fibers was effective in altering their surface physical chemistry and structural morphology, resulting in improved interfacial adhesion in the fiber/epoxy matrix. The reliability of single-fiber pull-out test data could be improved by statistical analysis using the Weibull distribution, which served to predict the variation of the mechanical interfacial properties in a composite system.

Journal Article↗
PubMed1996

Kinetic basis for the substrate specificity during hydrolysis of phospholipids by secreted phospholipase A2.

Kinetics of hydrolysis of aqueous dispersions of arsono-, sulfo-, phosphono- and phospholipids by phospholipase A2 from pig pancreas are characterized in terms of interfacial rate and equilibrium parameters. The enzyme with or without calcium binds with high affinity to the aqueous dispersions of the four classes of anionic lipids and shows the same general kinetic behavior. The rate of hydrolysis of anionic substrates does not show an anomalous change at the critical micelle concentration because the enzyme is present in aggregates even when bulk of the substrate is dispersed as a solitary monomer. Apparent affinities of the enzyme for the interface of different anionic lipids are virtually the same. Also, affinities of these substrates for the active site of the enzyme at the interface are comparable. However, a significant change in the catalytic turnover rate is seen as the sn-3 phosphodiester group is modified; the apparent maximum rate at saturating bulk substrate concentration, V(M)app values, increase in the order: homo- and arsonolipids < sulfo- < phosphono- < phospholipids. Not only the basis for the sn-2 enantiomeric selectivity but also the decrease in the rate of hydrolysis with the increasing chain length is due to a decrease in the value of V(M)app. Results show that even when the bulk concentration of anionic phospholipid is below cmc, hydrolysis occurs in aggregates of enzyme and substrate where the chemical step of the turnover cycle remains rate-limiting, which provides a basis for the assumption that V(M)app is directly related to Kcat. The fact that Kcat depends on the nature of the head group (phosphate, phosphonate, sulfate, arsonate) implies that the head group plays a critical role in the rate-limiting chemical step of the catalytic cycle, possibly during the decomposition of the tetrahedral intermediate. The significance of these results for the microscopic steady-state condition for hydrolysis at the micellar interface, mechanism of esterolysis by phospholipase A2, and inhibitor design are discussed.

Animals↗
PubMed2002

Self-assembled monolayers of alkanethiolates on palladium are good etch resists.

This paper describes microcontact printing (muCP) of long-chain alkanethiolates on palladium, followed by solution-phase etching with an iron(III)-based etchant, to make patterned structures. The commonly used soft-lithographic procedure for fabricating microstructures-muCP of SAMs on gold-has three shortcomings: a significant surface density of pinhole defects, substantial edge roughness, and incompatibility with processes used in CMOS fabrication. Microcontact printing on palladium gives fewer defects and smaller edge roughness than on gold, and is compatible with CMOS. The mechanism by which etch-resistant patterns are formed is different for palladium and gold. The Pd/S interfacial layer formed by the reaction of palladium films with sulfur-containing compounds provides good resistance to etches independently of the barrier to access the surface provided by the film of (CH2)n groups in the long-chain SAMs. This barrier is the basis of the etch resistance of SAMs on gold, but only supplements the etch resistance of the sulfur-containing interfacial layer on palladium. Characterization of the SAM formed from hexadecanethiol on palladium is described.

Microscopy, Electron, Scanning↗
PubMed2002

Action of chlorhexidine digluconate against yeast and filamentous forms in an early-stage Candida albicans biofilm.

An in situ method for sensitive detection of differences in the action of chlorhexidine against subpopulations of cells in Candida albicans biofilms is described. Detection relies on monitoring the kinetics of propidium iodide (PI) penetration into the cytoplasm of individual cells during dosing with chlorhexidine. Accurate estimation of the time for delivery of the dosing concentration to the substratum was facilitated by using a flow cell system for which transport to the interfacial region was previously characterized. A model was developed to quantify rates of PI penetration based on the shape of the kinetic data curves. Yeast were seeded onto the substratum, and biofilm formation was monitored microscopically for 3 h. During this period a portion of the yeast germinated, producing filamentous forms (both hyphae and pseudohyphae). When the population was subdivided on the basis of cell morphology, rates of PI penetration into filamentous forms appeared to be substantially higher than for yeast forms. Based on the model, rates of penetration were assigned to individual cells. These data indicated that the difference in rates between the two subpopulations was statistically significant (unpaired t test, P < 0.0001). A histogram of rates and analysis of variance indicated that rates were approximately equally distributed among different filamentous forms and between apical and subapical segments of filamentous forms.

Amphotericin B↗