Biomedical subjects

R Brasseur

Publications and source records attributed to R Brasseur.

At least 127 records · Page 7Linked to original sources

PubMed1991

Theoretical and functional analysis of the SIV fusion peptide.

The fusion domain of simian immunodeficiency virus (SIV) envelope glycoproteins is a hydrophobic region located at the amino-terminal extremity of the transmembrane protein (gp32). Assuming an alpha helical structure for the SIV fusogenic domain of gp32 in a lipid environment, theoretical studies have predicted that the fusion peptide would insert obliquely in the lipid bilayer. This oblique insertion could be an initial step of the fusion process by disorganizing locally the structure of the lipid bilayer. We have tested this hypothesis by selectively mutagenizing the SIV gp160 expressed via a vaccinia virus vector, to alter the theoretical angle of insertion of the fusion peptide. The fusogenic activity of the wild-type and mutant glycoproteins was tested after infection of T4 lymphocytic cell lines by the recombinant vaccinia virus, and measure of syncytia formation. Mutations that modified the oblique orientation reduced the fusogenic activity. In contrast, mutations that conserve the oblique orientation did not alter the fusogenic properties. Our results support the hypothesis that oblique orientation is important for fusogenic activity.

Amino Acid Sequence↗

PubMed1991

New derivatives of kanamycin B obtained by modifications and substitutions in position 6''. 2. In vitro and computer-aided toxicological evaluation with respect to interactions with phosphatidylinositol.

In a companion paper (previous paper in this issue), we report on the synthesis and microbiological evaluation of new derivatives of the aminoglycoside antibiotic kanamycin B carrying substitutions in 6" (halogeno, or amino, amido, thioalkyl, and alkoxy groups, each series with increasingly bulkier chains). These modifications were intended to potentially modulate the interactions of kanamycin B with phospholipids since these are related to inhibition of lysosomal phospholipase activities and lysosomal phospholipidosis, an early and predictive index of the nephrotoxic potential of aminoglycosides. The new derivatives were therefore examined for inhibitory potency in vitro toward lysosomal phospholipase A1 acting on phosphatidylcholine included in negatively charged liposomes. No simple correlation was observed between the nature or the size of the 6''-substituent and the inhibitory potencies of the corresponding derivatives, although certain groups (diethylamino, isopropylthio) caused a significant increase in inhibitory potency, whereas an N-acetyl-N-methylamino substituent had the opposite effect. 6''-Deoxy-6''-chlorokanamycin B, however, was the only derivative showing both a decrease (albeit limited) of inhibitory potency toward phospholipase A1 associated with the maintenance of a satisfactory microbiological activity (actually equal or slightly better than that of kanamycin B). Computer-aided conformational analysis showed that this chloro substituent did not allow the molecule to insert itself very differently compared to kanamycin B or 6''-deoxykanamycin B in a monolayer of phosphatidylinositol, all three drugs adopting an orientation largely parallel to the hydrophobic-hydrophilic interface and being largely "embedded" in the bilayer at that level. In contrast, the N-acetyl-N-methylamino and isopropylthio substituents caused the corresponding derivatives to adopt an orientation largely perpendicular to the interface, because of the attraction of this substituent, and therefore of the 3''-amino sugar moiety of kanamycin B into the hydrophobic domain of the monolayer, whereas the opposite part of the drug (2',6'-diamino sugar) protruded into the aqueous phase. No simple correlation, however, could be drawn between these changes of conformation and the relative inhibitory potencies of the derivatives.

Computer Graphics↗

PubMed1991

New derivatives of kanamycin B obtained by combined modifications in positions 1 and 6". Synthesis, microbiological properties, and in vitro and computer-aided toxicological evaluation.

Substitution of the C-1 atom in the 2-deoxystreptamine moiety of gentamicin C2, a broad-spectrum aminoglycoside antibiotic, by an axial hydroxymethyl group has been reported to confer protection against most clinically important bacterial enzymes inactivating aminoglycosides, while simultaneously reducing the nephrotoxic potential of this drug. We report here on a similar modification of kanamycin B. Microbiological evaluation, however, revealed no useful protection, as established by the almost complete lack of activity of 1-C-(hydroxymethyl)kanamycin B against an array of organisms producing defined types of aminoglycoside-inactivating enzymes and against which 1-C-(hydroxymethyl)gentamicin C2 and amikacin (1-N-[(S)-2-hydroxy-4-aminobutyryl]kanamycin A) are active. Moreover, toxicological evaluation, based on the in vitro measurement of the drug inhibitory potential toward lysosomal phospholipases, a predictive test of the intrinsic nephrotoxic potential of aminoglycosides, showed not decreased but rather increased toxicity. Comparative conformational analysis of the interactions of the drug with a phosphatidylinositol monolayer explained the lack of protective effect, since no significant change of the mode of insertion of the derivative in this monolayer was detected compared to that of kanamycin B. Combination of a 1-C-(hydroxymethyl) substituent with a 6"-chloro, 6"-acetamido substituent resulted in a partial improvement of the toxicological behavior with no loss of activity for the 6"-chloro and the 6"-azido derivatives, but not to the extent of obtaining better derivatives than kanamycin B itself. We, therefore, suggest that the advantages of an axial hydroxymethyl substituent at C-1 are probably restricted to the gentamicin family and do not extend to kanamycins. It might be concluded that the structural differences between gentamicins and kanamycins play an important, still undescribed role both in their effective recognition by aminoglycoside-inactivating enzymes, which are responsible for most of the clinically important cases of resistance to aminoglycosides, and also in the interactions with phospholipids, which in turn cause nephrotoxicity.

Gram-Positive Bacteria↗

PubMed1991

Lipid-itraconazole interaction in lipid model membranes.

Itraconazole, a lipophilic, fungal sterol-biosynthesis inhibitor, does not disturb membrane organization parameters measured by differential scanning calorimetry and infrared spectroscopy. Conformational analysis studies suggest that the molecular volume and the position of itraconazole in the lipid membrane is similar to that of dipalmitoyl phosphatidylcholine. The mean energy of interaction between itraconazole and the phospholipid is -60.6 kJ mol-1 whereas this energy in the pure lipid matrix is -54.3 kJ mol-1. The mean molecular area of itraconazole calculated by projecting the molecule on the lipid-water interface is equal to that occupied by the pure lipid (60 A2/molecule).

1,2-Dipalmitoylphosphatidylcholine↗

PubMed1991

Characterization of the discoidal complexes formed between apoA-I-CNBr fragments and phosphatidylcholine.

The structure, composition, and physico-chemical properties of lipid-protein complexes generated between dimyristoylphosphatidylcholine (DPMC) and the CNBr fragments of human apoA-I were studied. The fragments were separated by high performance liquid chromatography and purified on a reversed-phase column. The complexes with DMPC were isolated on a Superose column; their dimensions were obtained by gradient gel electrophoresis and by electron microscopy. The secondary structure of the protein in the complexes was studied both by circular dichroism and by attenuated total reflection infrared spectroscopy. The fragments 1 and 4 of apoA-I, containing, respectively, two and three amphipathic helices, recombined with the phospholipid to generate discoidal particles with sizes similar to that of apoA-I- and apoA-II-DMPC complexes. The infrared measurements indicated that in all complexes the apolipoprotein helical segments were oriented parallel to the phospholipid acyl chains and that the protein was located around the edges of the discs. Computer modelling of the complexes based on energy minimization techniques proposed a model for these particles in agreement with the dimensions measured experimentally. In conclusion, we propose that apoA-I and its longest CNBr fragments are able to generate discoidal particles with DMPC, with apolipoprotein helical segments oriented parallel to the acyl chains of the phospholipids.

Apolipoprotein A-I↗

PubMed1990

Orientation into the lipid bilayer of an asymmetric amphipathic helical peptide located at the N-terminus of viral fusion proteins.

The complete amino-acid sequence of viral fusion proteins has been analyzed by the Eisenberg procedure. The region surrounding the cleavage site contains a highly hydrophilic region immediately followed by a membrane-like region. Since the effective cleavage between these two domains seems required to expose the fusogenic domain (located at the N-terminal sequence of the transmembrane like region) which is assumed to interact with the lipid membrane of the host cell, we have focused our analysis on the conformation and mode of insertion of this membrane-like domain in a lipid monolayer. It was inserted as an alpha-helical structure into a dipalmitoylphosphatidylcholine (DPPC) monolayer and its orientation at the lipid/water interface was determined using a theoretical analysis procedure allowing the assembly of membrane components. For each viral protein sequence these N-terminal helical segments oriented obliquely with respect to the lipid/water interface. This rather unusual orientation is envisaged as a prerequisite to membrane destabilization and fusogenic activity.

Amino Acid Sequence↗

PubMed1990

Effect of acidic phospholipids on the activity of lysosomal phospholipases and on their inhibition by aminoglycoside antibiotics--I. Biochemical analysis.

Aminoglycoside antibiotics accumulate in lysosomes of kidney and cultured cells and cause an impairment of phospholipid catabolism which is considered to be an early and significant step in the development of their toxicity. Using liposomes, wer previously demonstrated that the activity of lysosomal phospholipases A1 and A2 towards phosphatidylcholine was markedly enhanced by the inclusion of phosphatidylinositol in the bilayer, and that gentamicin impaired this activity by binding to phosphatidylinositol. Since gentamicin-induced inhibition was inversely related to the amount of phosphatidylinositol included in the liposomes, we proposed that gentamicin impairs activity of phospholipases by decreasing the quantity of available negative charges carried by the bilayer surface (Mingeot-Leclercq et al., Biochem Pharmacol 37: 591-599, 1988). We now extend these observations to phosphatidylserine and phosphatidic acid, and compare the inhibition caused by gentamicin, amikacin and streptomycin towards lysosomal phospholipases on the hydrolysis of phosphatidylcholine in the presence of each of these acidic phospholipids. Inclusion of phosphatidic acid in liposomes, and, to a lesser extent, phosphatidylserine, caused a larger increase in phospholipases activity than phosphatidylinositol. In parallel, the three aminoglycosides tested were found less inhibitory towards phospholipases activity measured on phosphatidic acid-or phosphatidylserine-containing liposomes than was previously observed with phosphatidylinositol, even though equilibrium dialysis experiments failed to demonstrate significant difference in binding parameters of the drug towards each of these liposomes populations. Yet, as for phosphatidylinositol-containing liposomes, the inhibition was inversely related to the amount of phosphatidic acid or phosphatidylserine included in the bilayer and the inhibitory potency of the three drugs was consistently gentamicin greater than amikacin greater than streptomycin with the three types of negatively-charged liposomes used. We conclude that impairment of lysosomal phospholipases activity towards phosphatidylcholine included in negatively-charged membranes by aminoglycoside antibiotics is dependent upon drug binding to the bilayer, but that it is modulated by the nature of the acidic phospholipid that binds the drug as well as by that of the drug itself. A companion paper (Mingeot-Leclercq et al., Biochem Pharmacol 40: 499-506, 1990) will examine by computer-aided conformational analysis the parameters (drug-phospholipid energy of interaction, position of the drug in a monolayer and its accessibility to the aqueous phase) which may be important for these effects.

Amikacin↗

PubMed1990

Effect of acidic phospholipids on the activity of lysosomal phospholipases and on their inhibition induced by aminoglycoside antibiotics--II. Conformational analysis.

In a companion paper (Mingeot-Leclercq et al. Biochem Pharmacol 40: 489-497, 1990), we showed that the inhibitory potency of gentamicin on the activity of lysosomal phospholipases, measured towards phosphatidylcholine included in negatively-charged liposomes, is markedly influenced by the nature of the acidic phospholipid used (phosphatidylinositol, phosphatidylserine, phosphatidic acid), whereas the binding of the drug to the three types of liposomes is similar. This result challenged previous conclusions pointing to a key role exerted by drug binding to phospholipid membranes and presumably charge neutralization, for phospholipases inhibition (Carlier et al. Antimicrob Agents Chemother, 23: 440-449, 1983; Mingeot-Leclercq et al., Biochem Pharmacol 37:591-599, 1988). Conformational analysis of mixed monolayers of gentamicin and each of the three acid phospholipids shows that gentamicin systematically adopts an orientation largely parallel to the hydrophobic-hydrophilic interface, but that (i) the energies of interaction are largely different (phosphatidylinositol greater than phosphatidylserine greater than phosphatidic acid), and (ii) the apparent accessibility of the bound drug to water varies in an inverse relation with the energies of interaction. Amikacin, a semisynthetic derivative of kanamycin A with a lower inhibitory potential towards phospholipases than gentamicin in the three types of liposomes used, also showed similar differences in energies of interaction and accessibility to water, but constantly exhibited an orientation perpendicular to the hydrophobic-hydrophilic interface. We conclude that impairment of lysosomal phospholipase activities towards phosphatidylcholine included in negatively-charged membranes by aminoglycoside antibiotics is indeed dependent upon drug binding to the bilayer, but is also modulated by (i) the nature of the acidic phospholipid, which influences the energy of interaction and the accessibility of the drug with respect to the hydrophilic phase, and (ii) the orientation of the drug, which it itself related to its chemical structure. Inasmuch as phospholipases inhibition is related to aminoglycoside nephrotoxicity, these findings may help in better defining the molecular determinants and mechanisms responsible for this adverse effect.

Amikacin↗

PubMed1990

Mode of assembly of amphipathic helical segments in model high-density lipoproteins.

The structure of discoidal apo A-I-phospholipid complexes, representing the metabolic precursors of mature high-density lipoprotein particles, was studied by a combination of both a theoretical and an experimental approach. The secondary structure of the complex was determined by circular dichroic measurements, while the relative orientation of the apo A-I helical segments and of the phospholipid acyl chains was determined by ATR infrared measurements. Fluorescence energy transfer between the tryptophan residues of apo A-I and fluorescent phospholipid probes yielded an estimation of the relative topography of the lipid and apolipoprotein components in discoidal and spherical particles. The theoretical approach consisted of the identification of the helical segments in various apo A-I species. These segments were then oriented at a lipid/water interface by minimization of their hydrophobic and hydrophilic transfer energies. The calculation of the hydrophobicity profiles along the axis of the helices leads to the identification of specific interactions between pairs of helices. The helices were further assembled together with the phospholipids by computer modelling, enabling an estimation of the dimensions of the complex. The combination of the experimental and theoretical results yielded a model for discoidal apolipoprotein-phospholipid complexes, in which the amphipathic helical segments are oriented along the edges of the discs. Such a model can be extended to the conversion of these complexes into mature spherical HDL, through the formation of a cholesteryl ester core.

Amino Acid Sequence↗

PubMed1990

Structure of the adriamycin-cardiolipin complex. Role in mitochondrial toxicity.

Adriamycin and its derivatives are among the most efficient antimitotics used in clinical therapy. A specific cardiotoxicity places a limit on the total dose of adriamycin that may be administered. The mechanism of cardiac toxicity is complex. Data accumulated from in vitro and in vivo studies indicate a possible common cause for the inhibition of numerous enzymes and tissue degradation by a free radical mechanism: the binding of adriamycin to the inner mitochondrial membrane cardiolipin. The structure of the adriamycin-cardiolipin complex has been investigated by using physico-chemical techniques and via conformational analysis. The results open a rational way to design new structures that are less cardiotoxic.

Animals↗

PubMed1990

Identification of seroreactive regions of the human papillomavirus type 16 protein E4, E6, E7 and L1.

Small fragments of the DNA of human papillomavirus type 16 (HPV-16) were randomly cloned into the bacteriophage fd which expresses the resulting peptides as part of its capsid. Antisera raised against different HPV-16 fusion proteins were used for screening of the phage clones and the reacting peptides were determined by sequencing the inserted HPV-16 DNA fragments of the positive recombinants. Seroreactive regions of the proteins derived from the E4, E6, E7 (two regions) and L1 (three regions) open reading frames could be found by this approach. Of these seven regions, four were defined by at least two overlapping inserts, thus limiting the domains to between 10 and 15 amino acids. In the case of the E4 open reading frame, the same region identified by immunoscreening was also found when synthetic overlapping octapeptides were tested by ELISA with the anti-E4 antiserum. Using an approach to predict 'receptor-like' regions within the respective proteins, five of the seven regions were also identified. From the data on these regions, synthetic peptides were produced and used for the detection of antibodies against HPV-16 proteins in human sera by ELISA.

Amino Acid Sequence↗

PubMed1990

Secretion of Yop proteins by Yersiniae.

Upon incubation at 37 degrees C in the absence of Ca2+ ions, pathogenic strains of the genus Yersinia cease growing and produce large amounts of a series of plasmid-encoded proteins involved in pathogenicity. These proteins, called Yops (for Yersinia outer membrane proteins), are detected in both the outer membrane fraction and the culture supernatant. We present here the nucleotide sequence of genes yop20 and yop25 from Yersinia enterocolitica O:9. Protein Yop25 is very similar to YopE, the corresponding protein from Yersinia pestis, Y. pseudotuberculosis, and Y. enterocolitica O:8 (A. Forsberg and H. Wolf-Watz, J. Bacteriol. 172:1547-1555, 1990). This is the first report of a yop20 sequence of yersiniae. We present evidences that Yops are not membrane proteins. Their detection in the membrane fraction results either from copurification of large aggregates of extracellular Yops with the membrane fraction or from the adsorption of released proteins to the cell surface. In contrast with Yops, protein P1 has characteristics of a true membrane protein. The release of Yops by Y. enterocolitica occurs by a novel secretion mechanism that does not involve the cleavage of a typical signal sequence or the recognition of a carboxy-terminal domain.

Amino Acid Sequence↗

PubMed1990

Map of sequential B cell epitopes of the HIV-1 transmembrane protein using human antibodies as probe.

Antibodies of individuals infected with the human immunodeficiency virus type 1 (HIV-1) were used to probe the antigenicity of the HIV-1 transmembrane protein of 41 kD (gp41) by antibody-reactive peptide scanning (Pepscan). Eleven distinct sequential antibody-binding sites were defined by testing reactivity to 339 overlapping nonapeptides spanning the complete gp41 amino acid sequence. Such analysis only maps continuous antibody-binding sites of nine amino acids in length and does not identify putative discontinuous or assembled epitopes. Three B cell epitopes (aa 609-622; aa 655-699; aa 664-681) at the amino-terminal border of the putative transmembrane anchor and two (aa 732-748; aa 744-762) at the carboxyl-terminal border of this domain were the most antigenic. One antibody-binding domain (aa 834-852) with four amino acids homologous to the beta-1 domain of HLA class II beta-chain was recognized by the serum in 1 of 4 AIDS patients tested and not by any of the eight sera from symptom-free individuals. Although functional domains of gp41 involved in virus replication, cytopathicity and possibly immunosuppression were shown to bind antibodies of HIV-1-infected individuals, no relationship between antibody recognition patterns and disease progression was apparent.

Acquired Immunodeficiency Syndrome↗

PubMed1989

Evaluation of the secondary structure of apo B-100 in low-density lipoprotein (LDL) by infrared spectroscopy.

The secondary structure of the apo B-100 protein present in human low density lipoprotein has been investigated by transmission and attenuated total reflection infrared spectroscopy. The amount of beta-sheet (41%) is significantly higher than that determined by CD spectroscopy in the present study (12%) and elsewhere (15-16%). The high percentage of beta-sheet structure in apo B-100 supports the importance of such segments in maintaining the lipid-protein assembly in LDL. Polarized infrared spectroscopy indicates that the beta-sheet component of apo B-100 adopts a preferential orientation with respect to the phospholipid monolayer surrounding the LDL, whereas no such orientation is observed for the other secondary structure components.

Apolipoprotein B-100↗

PubMed1989

Physico-chemical properties of prostaglandins and related pharmacological compounds. A theoretical study on conformational related activity.

Thromboxane A2, prostaglandin H2, a series of chemically stable cyclic endoperoxide analogues (U 46619, U 44069, ONO 11113, 9, 11, diazo PGH2 and SQ 26655) and different isomers of SQ 26655 were analysed for their spatial configuration by conformational analysis in a simulated membrane-water interface environment with a "structure tree" procedure already described for prostaglandins, leukotrienes and lipoxins. The conformers derived from the structure tree and with a high probability of existence are presented. A new method allows one to visualize the surface charge density of the calculated molecules. The spatial configuration and the surface charge density of each molecule are compared to their known order of competition binding to the putative TXA2/PGH2 receptor of platelets. The conformational and charge density analysis merely shows that the different stereochemistry of these molecules lead to spatial conformation, that mimics (agonists), or that are far from (antagonists) the TXA2/PGH2 conformation.

Chemical Phenomena↗

PubMed1989

High yield synthesis of the bovine leukemia virus (BLV) p24 major internal protein in Saccharomyces cerevisiae.

Bovine leukemia virus (BLV) p24 gene was expressed in Saccharomyces cerevisiae under the control of the PHO5 (encoding repressible acid phosphatase, rAPase) promoter. Yeast cells were transformed by a yeast-E. coli shuttle vector carrying the PHO5 promoter, the p24 gene and the CYC1 transcription terminator. After low inorganic phosphate (Pi) induction of the PHO5 promoter, p24 accumulated in the producing cells up to a concentration representing 10% of total soluble proteins. The expression level of p24 gene was not increased by insertion of the positive regulatory gene PHO4 on the p24 expression vector. The p24 produced in this system and incubated in crude yeast extract showed a remarkably high resistance to proteolytic degradation, a feature that presumably correlates with the compact globular conformation of the protein combined to the stabilizing effect of the N-terminal residue.

Acid Phosphatase↗

PubMed1989

Secondary structure of diphtheria toxin and its fragments interacting with acidic liposomes studied by polarized infrared spectroscopy.

We used infrared attenuated total reflection spectroscopy to study the structure of diphtheria toxin (DT) and its fragments A, B, CB1, and CB4 as a function of the pH in the absence and in the presence of phospholipid vesicles. Binding of DT to asolectin or DL-alpha-dipalmitoylphosphatidylcholine-DL-alpha-dipalmitoylphosphatidic acid liposomes at pH 7.3 results in a 10% increase in its alpha-helix content. At pH 4, in the presence of liposomes, the secondary structure of DT is characterized by the appearance of a beta-sheet structure with strengthened hydrogen bonds which did not exist before pH lowering. DT fragment B displays little conformational change upon pH lowering in the presence of liposomes. However, the alpha-helix content of CB1 increases by 10%, and polarization measurements indicate that the alpha-helices of CB1 at pH 4 are oriented parallel to the lipid acyl chains. On the other hand, the alpha-helix content of CB4 decreases dramatically while the low frequency beta-sheet content increases. Dichroism measurements demonstrate that this sheet lies close to a parallel to the bilayer surface. The fragment A of DT experiences a large conformational change upon pH lowering and binds to the liposome membrane even in the absence of DT fragment B. The conformational modification of DT fragment A is fully reversed when pH is brought back to 7.3.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed1989

Ultrastructural, physico-chemical and conformational study of the interactions of gentamicin and bis(beta-diethylaminoethylether) hexestrol with negatively-charged phospholipid layers.

Aminoglycoside antibiotics such as gentamicin, which are fully hydrophilic, and cationic amphiphilic drugs such as bis(beta-diethylaminoethylether)hexestrol (DEH), are both known to inhibit lysosomal phospholipases and induce phospholipidosis. This enzymatic inhibition is probably related to the neutralization of the surface negative charges on which the lysosomal phospholipases A1 and A2 are dependent to express fully their activities (Mingeot-Leclerq et al., Biochem Pharmacol 37: 591-599, 1988). Using negatively charged liposomes, we show by 31P NMR spectroscopy that both gentamicin and DEH cause a significant restriction in the phosphate head mobility and, in sonicated vesicles, the appearance of larger bilayer structures. Both DEH and gentamicin increased the apparent size of sonicated negatively charged liposomes (but not of neutral liposomes) as measured by quasi-elastic light scattering spectroscopy. Examination of replicas from freeze-etched samples, however, revealed that gentamicin caused aggregation of liposomes, whereas DEH induced their fusion and the formation of intramembranous roundly shaped structures. Only DEH caused a significant decrease of the fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene, a fluorescent lipid-soluble probe. In addition, DEH, but not gentamicin, interfered with the bilayer to hexagonal phase transition occurring in dioleoyl- and dielaidoylphosphatidylethanolamine liposomes upon warming, and caused the appearance of an isotropic signal suggestive of the formation of inverted micelles. In computer-aided conformational analysis of the molecules at a simulated air-water interface, gentamicin was shown to display a largely-open crescent shape. When surrounded by phosphatidylinositol molecules, it remained as such at the interface which it locally mis-shaped, establishing close contact with the negatively charged phospho groups. In contrast, DEH could be oriented perpendicularly to the interface, with its two cationic groups associated with the phospho groups, and its phenyl- and diethylethandiyl moieties deeply inserted between and interacting with the aliphatic chains. Thus, although both agents cause lysosomal phospholipases inhibition, the differences in their interactions with negatively-charged bilayers is likely to result in a different organization of the phospholipids accumulated in vivo, which could lead to different toxicities.

Fluorescence Polarization↗