Analysis of molecular diversity of the Trypanosoma cruzi trypomastigote small surface antigen reveals novel epitopes, evidence of positive selection and potential implications for lineage-specific serology

Chagas disease, marked by life-long chronic infection with Trypanosoma cruzi, remains a major parasitic disease in Latin America. Genetically heterogeneous, T. cruzi is divided into six discrete typing units (DTUs), most recently grouped as TcI-VI. The trypomastigote small surface antigen (TSSA) of T. cruzi has been described as the only known serological marker to identify infection by TcII-VI, as distinct from TcI. Here, by comparative analysis of a cohort of 25 reference strains representing all the known DTUs, we show that TSSA intra-specific diversity is greater than previously reported. Furthermore, TcIII and IV TSSA PCR products are, contrary to expectation, both digested by PvuII, revealing a more nuanced genotyping pattern. Amino acid sequence diversity reveals that the TSSA epitope considered to be serologically characteristic of TcII-VI is restricted to TcII, V and VI, but not of III or IV, and that the diagnostic peptide described as TcI-specific shares key features with TcIII and IV. Notably, TSSA sequences inferred greater phylogenetic affinities of TcIII and IV to TcI than to TcII, V or VI. A high ratio of non-synonymous to synonymous nucleotide substitutions (ω = 1.233) indicates that the TSSA gene has been under positive selection pressure. The demonstration of lineage-specific epitopes within TcII-VI has implications for sero-epidemiological studies of Chagas disease based on this antigen.     

Expression of tumor-specific transplantation antigen in cell lines transformed by wild-type of tsA mutant simian virus 40.

The simian virus 40-induced tumor-specific surface antigen(s) (TSSA) and tumor-specific transplantation antigen(s) (TSTA)were detected in cells transformed by wild-type or temperature-sensitive mutant simian virus 40 by an antibody-mediated cytolytic assay for TSSA and an immunization test for TSTA. Cells transformed by tsA mutants, which lose their transformed phenotype when grown at nonpermissive temperatures, nonetheless do express TSSA and TSTA as well as T-antigen at both temperatures.     

Development of Peptide-Based Lineage-Specific Serology for Chronic Chagas Disease: Geographical and Clinical Distribution of Epitope Recognition

Background

Chagas disease, caused by infection with the protozoan Trypanosoma cruzi, remains a serious public health issue in Latin America. Genetically diverse, the species is sub-divided into six lineages, known as TcI–TcVI, which have disparate geographical and ecological distributions. TcII, TcV, and TcVI are associated with severe human disease in the Southern Cone countries, whereas TcI is associated with cardiomyopathy north of the Amazon. T. cruzi persists as a chronic infection, with cardiac and/or gastrointestinal symptoms developing years or decades after initial infection. Identifying an individual''s history of T. cruzi lineage infection directly by genotyping of the parasite is complicated by the low parasitaemia and sequestration in the host tissues.

Methodology/Principal Findings

We have applied here serology against lineage-specific epitopes of the T. cruzi surface antigen TSSA, as an indirect approach to allow identification of infecting lineage. Chagasic sera from chronic patients from a range of endemic countries were tested by ELISA against synthetic peptides representing lineage-specific TSSA epitopes bound to avidin-coated ELISA plates via a biotin labelled polyethylene glycol-glycine spacer to increase rotation and ensure each amino acid side chain could freely interact with their antibodies. 79/113 (70%) of samples from Brazil, Bolivia, and Argentina recognised the TSSA epitope common to lineages TcII/TcV/TcVI. Comparison with clinical information showed that a higher proportion of Brazilian TSSApep-II/V/VI responders had ECG abnormalities than non-responders (38% vs 17%; p<0.0001). Among northern chagasic sera 4/20 (20%) from Ecuador reacted with this peptide; 1/12 Venezuelan and 1/34 Colombian samples reacted with TSSApep-IV. In addition, a proposed TcI-specific epitope, described elsewhere, was demonstrated here to be highly conserved across lineages and therefore not applicable to lineage-specific serology.

Conclusions/Significance

These results demonstrate the considerable potential for synthetic peptide serology to investigate the infection history of individuals, geographical and clinical associations of T. cruzi lineages.     

Involvement of TSSA (trypomastigote small surface antigen) in Trypanosoma cruzi invasion of mammalian cells

TSSA (trypomastigote small surface antigen) is a polymorphic mucin-like molecule displayed on the surface of Trypanosoma cruzi trypomastigote forms. To evaluate its functional properties, we undertook comparative biochemical and genetic approaches on isoforms present in parasite stocks from extant evolutionary lineages (CL Brener and Sylvio X-10). We show that CL Brener TSSA, but not the Sylvio X-10 counterpart, exhibits dose-dependent and saturable binding towards non-macrophagic cell lines. This binding triggers Ca(2+)-based signalling responses in the target cell while providing an anchor for the invading parasite. Accordingly, exogenous addition of either TSSA-derived peptides or specific antibodies significantly inhibits invasion of CL Brener, but not Sylvio X-10, trypomastigotes. Non-infective epimastigote forms, which do not express detectable levels of TSSA, were stably transfected with TSSA cDNA from either parasite stock. Although both transfectants produced a surface-associated mucin-like TSSA product, epimastigotes expressing CL Brener TSSA showed a ~2-fold increase in their attachment to mammalian cells. Overall, these findings indicate that CL Brener TSSA functions as a parasite adhesin, engaging surface receptor(s) and inducing signalling pathways on the host cell as a prerequisite for parasite internalization. More importantly, the contrasting functional features of TSSA isoforms provide one appealing mechanism underlying the differential infectivity of T. cruzi stocks.     

Hybridization of a mouse T-cell lymphocyte line (HB1) with a polyoma virus-transformed mouse fibroblast line

The establishment of permanent T-lymphocyte cell lines by transformation with DNA viruses has not yet been achieved. This paper reports the successful transfer of polyoma virus genome into T-lymphocyte cells by somatic hybridization. A T-lymphocyte clone, HB₁, derived from (DBA/ 2J×AKR) spleen cells, isolated in vitro by cloning in semi-solid agar, was fused with a polyoma (Py) virus-transformed fibroblast C3HPy, clone 1. The authenticity of the hybrid C3H/HB was established by chromosome and histocompatibility antigen studies. This initial population and the various clones retained T-lymphocyte characteristics such as morphological appearance, growth properties (suspension culture) and differentiation antigen (Thy 1–2). The hybrid cell line and the various clones presented all the characteristics of Py transformation. Namely, they carried the Py genome originating from the fibroblastic parent and maintained Py virus tumour-associated antigens (TSTA, TSSA and T antigens). In most respects, this hybrid population resembled the C3HPy/C11 parent and exhibited the same tumorigenicity.     

Effective algorithms for tag SNP selection

Single nucleotide polymorphisms (SNPs), due to their abundance and low mutation rate, are very useful genetic markers for genetic association studies. However, the current genotyping technology cannot afford to genotype all common SNPs in all the genes. By making use of linkage disequilibrium, we can reduce the experiment cost by genotyping a subset of SNPs, called Tag SNPs, which have a strong association with the ungenotyped SNPs, while are as independent from each other as possible. The problem of selecting Tag SNPs is NP-complete; when there are large number of SNPs, in order to avoid extremely long computational time, most of the existing Tag SNP selection methods first partition the SNPs into blocks based on certain block definitions, then Tag SNPs are selected in each block by brute-force search. The size of the Tag SNP set obtained in this way may usually be reduced further due to the inter-dependency among blocks. This paper proposes two algorithms, TSSA and TSSD, to tackle the block-independent Tag SNP selection problem. TSSA is based on A* search algorithm, and TSSD is a heuristic algorithm. Experiments show that TSSA can find the optimal solutions for medium-sized problems in reasonable time, while TSSD can handle very large problems and report approximate solutions very close to the optimal ones.     

Two star‐shaped tetranuclear Ru(II) complexes containing uncoordinated imidazole groups: synthesis,characterization, photophysical and pH sensing properties

Tetrapodal ligands H₄L¹ and H₄L² containing imidazole groups have been synthesized by the reaction of 1,10‐phenanthroline‐5,6‐dione with 1,2,4,5‐tetrakis[(4‐formylphenoxy)methyl]benzene and 1,2,4,5‐tetrakis[(3‐formylphenoxy)methyl]benzene, respectively, in presence of NH₄OAc. Two star‐shaped complexes [{Ru(bpy)₂}₄(μ₄‐H₄L¹)](PF₆)₈ and [{Ru(bpy)₂}₄(μ₄‐H₄L²)](PF₆)₈ (bpy = 2,2′‐bipyridine) have been prepared by refluxing Ru(bpy)₂Cl₂·2H₂O and each ligand in ethylene glycol. The deprotonated complexes [{Ru(bpy)₂}₄(μ₄‐L¹)](PF₆)₄ and [{Ru(bpy)₂}₄(μ₄‐L²)](PF₆)₄ have been obtained by the reaction of sodium methoxide with [{Ru(bpy)₂}₄(μ₄‐H₄L¹)](PF₆)₈ and [{Ru(bpy)₂}₄(μ₄‐H₄L²)](PF₆)₈, respectively, in methanol. The pH effects on the UV–vis light absorption and emission spectra of both complexes have been studied, and ground‐ and excited‐state ionization constants of both complexes have been derived. The photophysical properties of both complexes are strongly dependent on the solution pH. They act as proton‐induced off–on–off luminescent sensors through two successive deprotonation processes of imidazole groups, with a maximum on–off ratio of 8 in buffer solution at room temperature. Theoretical calculations for the highest occupied molecular orbital (HOMO) and lowest occupied molecular orbital (LOMO) orbitals of bridging ligand are also presented for plausible explanations of the fluorescence changes. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis, characterization and electrochemical behavior of oxo-bridged (arylimido)[tris(3,5-dimethylpyrazolyl)borato] molybdenum(V) complexes

Reaction of the oxo-molybdenum(V) precursor [MoTp*(O)Cl₂] [Tp* = hydrotris(3,5-dimethyl-1-pyrazolyl)borate] with H₂NC₆H₄R-4 (R = OEt; OPr) in refluxing toluene in the presence of Et₃N afforded the binuclear oxo-bridged oxo(arylimido) molybdenum(V) complexes [Tp*Mo(O)Cl](μ-O)[Tp*Mo(NC₆H₄OR-4)Cl]. Surprisingly, a similar reaction between [MoTp*(O)Cl₂] and C₆H₅NH₂ yielded the previously reported compound [{MoTp*(O)Cl}₂(μ-O)] as the only product. The new compounds were characterized by microanalytical data, mass spectrometry, IR and ¹H NMR spectroscopy. Cyclic voltammetric studies of the new compounds, of the previously reported compounds [Tp*Mo(O)Cl](μ-O)[Tp*Mo(NAr)Cl] (Ar = C₆H₄OMe-4, C₆H₄F-3, C₆H₄Cl-4, C₆H₄Br-4, and C₆H₄I-3), and of [{MoTp*(O)Cl}₂(μ-O)] revealed a reversible one-electron oxidation process that is little affected by the nature of the substituent on the aryl group, whereas it is greatly affected by replacement of the imido ligand with an oxo ligand. The [{MoTp*(O)Cl}₂(μ-O)] compound also shows a one-electron reduction process.     

The conversion of leukotriene C4 to isomers of leukotriene B4 by human eosinophil peroxidase

The smooth muscle contractile and vasoactive mediator leukotriene C₄ (5(S)-hydroxy-6(R)-sulfido-glutathionyl-eicosatetraenoic acid; LTC₄) is converted by phorbol ester-stimulated human eosinophils to two isomers of leukotriene B₄, 5(S),12(R)-6,8,10 trans-14 cis-eicosatetraenoic acid (5(S),12(R)-“all-trans”-LTB₄) and 5(S),12(S)-“all-trans”-LTB₄, which are leukocyte chemotactic factors lacking the humoral functions of LTC₄. Optimal conversion of LTC₄ to the “all-trans” isomers of LTB₄ by intact eosinophils and soluble eosinophil peroxidase requires both H₂O₂ and halide ions. Oxidative metabolism of leukotrienes may represent an important regulatory function of eosinophils in hypersensitivity reactions.     

Syntheses and characterizations of four mixed-ligand hydrogen bonding supramolecular architectures with different structural motifs

The reactions of 4-aminobenzoic acid (4-abaH), 4,4′-bipyridine (4,4′-bipy) and transitional metal ions (Zn^II, Mn^II and Cu^II) gave rise to four supramolecular architectures, namely, [(4-abaH)₂(4,4′-bipy)] (1), {[Zn₂(4,4′-bipy)₂(4-aba)₄] (H₂O)₅}_n (2), {[Mn(4,4′-bipy)₂(H₂O)₄] (4-aba)Br(H₂O)₃} (3) and {[Cu₂(4,4′-bipy)₃(H₂O)₂(4-aba)₂](NO₃)₂(H₂O)₄}_n (4). Their crystal structures were determined by X-ray diffraction and show different structural motifs. 1 is a one-dimensional hydrogen bonding ladder constructed by 4-abaH and 4,4′-bipy. In 2, 4,4′-bipy bridges Zn(4-aba)₂ units forming a one-dimensional zigzag chain, which is extended into a three-dimensional framework by crystalline water molecules through hydrogen bonding interactions. Three-dimensional network of 3 is constructed by mononuclear [Mn(4,4′-bipy)₂(H₂O)₄]²⁺ cations, neutral crystalline water molecules, and 4-aba and Br⁻ anions through extensive hydrogen bonding and π-π interactions. However, one-dimensional ladder formed by 4,4′-bipy and Cu(4-aba) units in 4 is extended into a three-dimensional architecture through interpenetration of the lateral 4-aba arms into squares of the adjacent Cu-(4,4′-bipy) ladders and extensive hydrogen bonding interactions.     

Characterization of nickel tetrahydroxy phthalocyanine complexes and the electrocatalytic oxidation of 4-chlorophenol: Correlation of theory with experiments

This work reports on the use of nickel(II) tetrahydroxy (NiPc(OH)₄) and (poly-Ni(OH)Pc(OH)₄) phthalocyanine complexes as films on ordinary poly graphite electrode (OPGE) for the electrochemical oxidation of 4-chlorophenol (4-CP). The NiPc(OH)₄ film was electrotransformed to Ni(OH)Pc(OH)₄ film in aqueous 0.1 M NaOH solution to the ‘O-Ni-O oxo’ bridge form. The result showed that the Ni(OH)Pc(OH)₄ film on OPGE was more electroactive in terms of increase in current and less catalytic in terms of potential compared to the adsorbed NiPc(OH)₄ on OPGE. The reactivity of the two molecules was explained by theoretical calculations. The energies of the frontier orbitals of NiPc(OH)₄, Ni(OH)Pc(OH)₄ and 4-chlorophenol were calculated using density functional theory (DFT) method. The inter molecular hardness (η) and donor-acceptor hardness (η_DA) of Ni(OH)Pc(OH)₄, NiPc(OH)₄, Ni(OH)Pc(OH)₄/4-chlorophenol and NiPc(OH)₄/4-chlorophenol were estimated. The Ni(OH)Pc(OH)₄, showed stronger interaction with 4-chlorophenol than NiPc(OH)₄. DFT method was also used to model IR and Raman spectrum of H₂Pc(OH)₄ and NiPc(OH)₄.     

Chiral and achiral layered divalent metal aromatic ortho-dicarboxylate coordination polymers with bis(4-pyridylmethyl)piperazine ligands: Luminescent behavior and magnetic properties

Four divalent metal coordination polymers containing bis(4-pyridylmethyl)piperazine (4-bpmp) and the ortho-dicarboxylate ligands phthalate (pht) or 4-methylphthalate (mpht) have been prepared by solvent diffusion or hydrothermal methods. {[Cu₂(pht)₂(H4-bpmp)₂(H₂O)₂](NO₃)₂·H₂O}_n (1) and {[Cu₂(pht)₂(H4-bpmp)₂(H₂O)₂](SO₄)·2H₂O}_n (2) possess chiral cationic layer motifs formed by the junction of [Cu(H₂O)(pht)]_n chains by tethering curled-conformation H4-bpmp⁺ ligands. {[Co(pht)(H₂O)(4-bpmp)]·5.5H₂O}_n (3) displays a (4,4) grid constructed from anti-syn carboxylate-bridged {Co₂(H₂O)₂(pht)₂} dimeric clusters linked by open-conformation 4-bpmp ligands. {[Cd₂(mpht)₂(H₂O)₂(4-bpmp)(H4-bpmp)]ClO₄·4H₂O}_n (4) manifests cationic layered motifs based on neutral [Cd₂(H₂O)₂(mpht)₂] dinuclear units with {CdOC₄O}₂ 12-membered circuits, linked by open-conformation 4-bpmp and H4-bpmp⁺ ligands. Variable-temperature magnetic data indicate likely concomitant zero-field splitting and ferromagnetic coupling in 3. Violet light emission is observed when 4 is subjected to ultraviolet irradiation.     

Pharmacological comparison of L-serine borate and glutathione as inhibitors of metabolism of LTC4 to LTD4 by the isolated guinea pig trachea

Cumulative dose-response curyes to leukotriene C₄ (LTC₄) and leukotriene D₄ (LTD)₄ were obtained on indomethacin (5 μM) treated isolated guinea pig tracheal spiral strips. LTC₄ curves, in the presence of either glutathione (GSH; 10 mM) or L-serine borate (SB; 45 mM), were not antagonized by FPL-55712 (3 μM), a selective LTD₄ receptor antagonist. LTC₄ curves on trachea treated with a lower concentration of GSH (1 mM), and LTD₄ curves were competitively antagonized by FPL-55712. LTC, curves on GSH (10 mM) treated trachea were 2 fold to the left of those on SB treated tissues. This effect of GSH was blocked by pretreatment with nordihydro-guiaretic acid (30 μM), an inhibitor of 5-lipoxygenase.GSH (10 μM) and SB (45 mM) are effective inhibitors of conversion of LTC₄ into functionally important levels of LTD₄ by the guinea pig trachea. In addition, GSH appeares to enhance LTC₄ responsiveness by increasing synthesis of a contractile 5-lipoxygenase product(s), possibly LTC₄. From the data it is suggested that for inhibition of LTC₄ metabolism, SB may be more usefull when examining responses to exogenously applied LTC₄, while GSH (10 mM) may be useful when examining responses to endogenously generated LTC₄.     

Synthesis and kinetic studies of new bipyridyl platinum(II) phenoxide complexes by phase transfer catalysis: Crystal structure of [(bipy)Pt(OC6H4-4-OMe)2]

The synthesis of new platinum bipy (bipy = 2,2′-bipyridyl) complexes containing phenoxide ligands is reported, together with kinetic studies of their oxidative addition reactions with MeI to produce phenoxo platinum(IV) complexes. Complexes of the form [(bipy)Pt(OC₆H₄-4-X)₂] (X = OCH₃, CH₃, H, Br, Cl) are prepared by the reaction of the chloro complex [(bipy)PtCl₂] with substituted phenols and KOH in a two phase system of water and chloroform in the presence of benzyl triphenylphosphonium chloride. Platinum(IV) complexes are formed by oxidative addition of MeI to the platinum(II) complexes obtained. The complexes are characterized by elemental analysis, UV-Vis, IR, mass spectrometry and ¹H and ¹³C NMR spectroscopy.The reaction of methyl iodide with [(bipy)Pt(OC₆H₄-4-OMe)₂] to give [(bipy)PtMe(I)(OC₆H₄-4-OMe)₂] follows the rate law rate = k₂[(bipy)Pt(OC₆H₄-4-OMe)₂][MeI]. The values of k₂ increase with increasing polarity of the solvent, suggesting a polar transition state for the reaction.     

Simple layered or complex self-penetrated networks in cadmium homophthalate coordination polymers containing 1,3-bis(4-pyridyl)propane

Hydrothermal reaction of cadmium salts with homophthalic acid (H₂hmph) and 1,3-bis(4-pyridyl)propane (dpp) afforded coordination polymers whose topologies are determined by the absence or presence of any unligated counteranions. [Cd(hmph)(dpp)]_n (1) has a zig-zag (4,4) layer topology with simple AAA stacking. {[Cd₆(hmph)₄(dpp)₁₁(H₂O)₄] (ClO₄)₄·4H₂O}_n (2) has a complicated, unprecedented tetranodal self-penetrated cationic three-dimensional net built from the linkage of 5-fold interpenetrated 3-connected 4.14²cds-a topology [Cd₆(H₂O)₄(dpp)₁₁]_n¹²ⁿ⁺ subnets by bridging and exotridentate hmph ligands. Luminescent properties of these materials are also discussed.     

Mobilization of iron by phytosiderophores as affected by other micronutrients

It has been shown previously (Treeby et al., 1989) that phytosiderophores, released by roots of iron deficient grasses (Gramineae), mobilize from calcareous soils not only iron (Fe) but also zinc (Zn), manganese (Mn) and copper (Cu). Mobilization of Fe may therefore be impaired by other micronutrient cations. This has been studied in both, model experiments with Fe hydroxide and with a calcareous soil (15% CaCO₃, pH 8.6) amended with micronutrients as sulfate salts.Mobilization of Fe from Fe hydroxide by phytosiderophores (epi-3-hydroxymugineic acid) was not affected by the addition of CaCl₂, MgSO₄ and MnSO₄, slightly inhibited by ZnSO₄ and strongly inhibited by CuSO₄. In a calcareous soil amended with increasing levels of ZnSO₄, MnSO₄ and CuSO₄, mobilization of Fe by phytosiderophores remained uneffected by Zn and Mn amendments but was progressively impaired by increasing levels of Cu amendment, correlated with corresponding enhancement of Cu mobilization.High concentrations of ZnSO₄ and MnSO₄ and relatively high concentrations of CuSO₄ were required for inhibition of Fe mobilization by phytosiderophores. It is therefore concluded that in most calcareous soils phytosiderophores efficiently mobilize Fe, and that phytosiderophores play an important role in Fe acquisition by grasses grown on calcareous soils.     

Glycogen, its chemistry and morphological appearance in the electron microscope. III. Identification of the tissue ligands involved in the glycogen contrast staining reaction with the osmium (VI)-iron(II) complex

Synopsis By application of appropriate blocking reactions (acetylation, de-amination, methylation and NaHSO₃-treatment) it is demonstrated that the tissue ligands involved in the selective glycogen contrast staining reaction with the Os^VI. Fe^II complex (known to be present in the combination K₂OsO ₄ ^K ₄Fe(CN)₆) are the glycogen C₂–C₃ di-hydroxyl groups. Deliberate conversion of the diols into di-aldehydes and (di-)carboxyl groups by the application of specific oxidative agents followed, by application of the Os^VI.Fe^II-complex results morphologically in identical selective contrast staining of glycogen.By applying appropriate blocking reactions to such pre-oxidized aldehyde fixed glycogen, evidence is accumulated that K₂OsO₄ and K₃Fe(CN)₆ are unable to oxidize diols, whereas OsO₄ and H₂O₂ are able to convert diols into carboxyl groups.From these results it is concluded that in the combination K₂OsO ₄ ^K ₄Fe(CN)₆ the Os^VI.Fe^II complex reacts with unchanged diols in the glycogen, whereas the OsO₄ in the combination OsO ₄ ^K ₄Fe(CN)₆ can petentially create carboxyl groups in the aldehydefixed glycogen.The addition of urea to the two glycogen contrasting combinations (K₂OsO ₄ ^K ₄Fe(CN)₆ or OsO ₄ ^K ₄Fe(CN)₆), also emphasizes that, although morphologically both combinations produceidentical contrast stained glycogen, chemically the contrast staining is apparently obtained in a different way, as urea prevented the contrast for mation in the glycogen by the combination K₂OsO ₄ ^K ₄Fe(CN)₆, but not by the combination OsO ₄ ^K ₃Fe(CN)₆.     

Four-Stranded Dna Formed by Isoguanine Quartets: Complex Stoichiometry, Thermal Stability and Resistance Against Exonucleases

Single stranded DNA-fragments containing short runs of isoguanine such as d(T₄iG₄T₄) (5) or d(iG₄T₄) (6) form quartet structures by self-assembly of the isoguanine residues. The stoichiometry of the complexes is deduced from mixed aggregates formed between d(T₄iG₄T₄) and d(iG₄T₄). The iG_d-tetrads are more stable with regard to their thermal denaturation and to their resistance against enzymatic phosphodiester hydrolysis than those formed by dG.     

Role of electrostatics in the binding of charged metallophthalocyanines to neutral and charged phospholipid membranes

Binding of the cationic tetra(tributylammoniomethyl)-substituted hydroxoaluminum phthalocyanine (AlPcN₄) to bilayer lipid membranes was studied by fluorescence correlation spectroscopy (FCS) and intramembrane field compensation (IFC) methods. With neutral phosphatidylcholine membranes, AlPcN₄ appeared to bind more effectively than the negatively charged tetrasulfonated aluminum phthalocyanine (AlPcS₄), which was attributed to the enhancement of the coordination interaction of aluminum with the phosphate moiety of phosphatidylcholine by the electric field created by positively charged groups of AlPcN₄. The inhibitory effect of fluoride ions on the membrane binding of both AlPcN₄ and AlPcS₄ supported the essential role of aluminum-phosphate coordination in the interaction of these phthalocyanines with phospholipids. The presence of negative or positive charges on the surface of lipid membranes modulated the binding of AlPcN₄ and AlPcS₄ in accord with the character (attraction or repulsion) of the electrostatic interaction, thus showing the significant contribution of the latter to the phthalocyanine adsorption on lipid bilayers. The data on the photodynamic activity of AlPcN₄ and AlPcS₄ as measured by sensitized photoinactivation of gramicidin channels in bilayer lipid membranes correlated well with the binding data obtained by FCS and IFC techniques. The reduced photodynamic activity of AlPcN₄ with neutral membranes violating this correlation was attributed to the concentration quenching of singlet excited states as proved by the data on the AlPcN₄ fluorescence quenching.     

Leukotriene F4: Comparison of its pharmacological profile with that of the other cysteinyl-containing leukotrienes in guinea-pig ileum and lung parenchyma in vitro

The biological effects of leukotriene (LT)F₄ were compared, on a molar basis, with those of LTC₄, LTD₄ and LTE₄ on isolated superfused strips of guinea-pig ileum smooth muscle (GPISM) and lung parenchyma (GPP). LTF₄ was 1–2 orders of magnitude less active than the other leukotrienes on GPISM (LTD₄ > LTC₄ > LTE₄ > LTF₄) whereas, in the GPP, the activity of LTF₄ was comparable with that of LTE₄, both leukotrienes being about one order of magnitude less active than LTC₄ or LTD₄ (LTC₄=LTD₄ > LTE₄=LTF₄). Further, LTF₄ caused protracted contractions of the GPP which were indistinguishable from those due to LTE₄ and of a much longer duration than responses elicited by either LTC₄ or LTD₄.FPL 55712 (1.9μM) antagonised actions of LTF₄ in both tissue preparations. Indomethacin (2.8μM) inhibited contractions induced by LTF₄ in GPP indicating that part of the bronchoconstriction due to LTF₄, like that elicited by the other leukotrienes, is mediated via release of cyclo-oxygenase products.