Structure activity relationship studies on the antimicrobial activity of novel edeine A and D analogues

Edeines are pentapeptide amide antibiotics composed of four nonprotein amino acids, glycine, and polyamine. They exhibit antimicrobial and immunosuppressive activities and are universal inhibitors of translation. Moreover, it was proven that the free ionizable carboxy group in the (2R, 6S, 7R)-2,6-diamino-7-hydroxyazelaic acid moiety is not essential for biological activity of these compounds. In this paper we describe the synthesis of four novel edeine A and D analogues in which the above-mentioned acid residue was replaced with the (3R, 4S)- or (3S, 4S)-4,5-diamino-3-hydroxypentanoic acid moiety. In one compound we also introduced into molecule the 3-N,N-dimethyl derivative of (S)-2,3-diaminopropanoic acid to prevent the transpeptidation process, which results in the loss of biological activity of alpha-isomers of edeines. All peptides were synthesized applying the active ester and azide methods and on the basis of the coupling of suitable N-terminal tripeptides with proper C-terminal dipeptide amides. The activities of the newly obtained edeine analogues against selected strains of bacteria and fungi are also presented.

N1,N10-ditigloylspermidine, a novel alkaloid from the seeds of Ipomoea nil

A novel spermidine alkaloid, N1,N10-ditigloylspermidine (1), has been isolated from the seeds of Ipomoea nil (L.) Roth (Convolvulaceae). Structural elucidation was achieved by EIMS, HRMS, 1H NMR, and 13C NMR spectroscopy.

NspS, a predicted polyamine sensor, mediates activation of Vibrio cholerae biofilm formation by norspermidine

Vibrio cholerae is both an environmental bacterium and a human intestinal pathogen. The attachment of bacteria to surfaces in biofilms is thought to be an important feature of the survival of this bacterium both in the environment and within the human host. Biofilm formation occurs when cell-surface and cell-cell contacts are formed to make a three-dimensional structure characterized by pillars of bacteria interspersed with water channels. In monosaccharide-rich conditions, the formation of the V. cholerae biofilm requires synthesis of the VPS exopolysaccharide. MbaA (locus VC0703), an integral membrane protein containing a periplasmic domain as well as cytoplasmic GGDEF and EAL domains, has been previously identified as a repressor of V. cholerae biofilm formation. In this work, we have studied the role of the protein NspS (locus VC0704) in V. cholerae biofilm development. This protein is homologous to PotD, a periplasmic spermidine-binding protein of Escherichia coli. We show that the deletion of nspS decreases biofilm development and transcription of exopolysaccharide synthesis genes. Furthermore, we demonstrate that the polyamine norspermidine activates V. cholerae biofilm formation in an MbaA- and NspS-dependent manner. Based on these results, we propose that the interaction of the norspermidine-NspS complex with the periplasmic portion of MbaA diminishes the ability of MbaA to inhibit V. cholerae biofilm formation. Norspermidine has been detected in bacteria, archaea, plants, and bivalves. We suggest that norspermidine serves as an intercellular signaling molecule that mediates the attachment of V. cholerae to the biotic surfaces presented by one or more of these organisms.

Time-dependent inhibitors of trypanothione reductase: analogues of the spermidine alkaloid lunarine and related natural products

The macrocyclic spermidine alkaloid lunarine 1 from Lunaria biennis is a competitive, time-dependent inhibitor of the protozoan oxidoreductase trypanothione reductase (TryR), a promising target in drug design against tropical parasitic diseases. Various molecules related to 1 and the alkaloid itself have been synthesized in racemic form and evaluated against TryR in order to determine the key features of 1 that are associated with time-dependent inhibition. Kinetic data are consistent with an inactivation mechanism involving a conjugate addition of an active site cysteine residue onto the C-24-C-25 double bond of the tricyclic nucleus of 1. Comparison of data for synthetic (+/-)-1, the natural product, and other derivatives 7-10 from L. biennis confirms the importance of the unique structure of the tricyclic core as a motif for inhibitor design and reveals that the non-natural enantiomer may be a more suitable scaffold upon which thiophilic groups may be presented.

Mechanism and structure-activity relationships of norspermidine-based peptidic inhibitors of trypanothione reductase

A library of polyamine-peptide conjugates based around some previously identified inhibitors of trypanothione reductase was synthesised by parallel solid-phase chemistry and screened. Kinetic analysis of library members established that subtle structural changes altered their mechanism of action, switching between competitive and non-competitive inhibition. The mode of action of the non-competitive inhibitors was investigated in detail by a variety of techniques including enzyme kinetic analysis (looking at both NADPH and trypanothione disulfide substrates), gel filtration chromatography and analytical ultracentrifugation, leading to the identification of an allosteric mode of inhibition.

Identification of trypanothione from the human pathogen Entamoeba histolytica by mass spectrometry and chemical analysis

In this paper, we present definitive data to show, from ESI (electrospray ionization) studies, that the thiol-bimane compound isolated and purified from Entamoeba histolytica trophozoites, corresponds unequivocally to the structure of trypanothione. Trypanothione disulphide was shown to have a molecular ion of m/z 722. It was further demonstrated by MALDI-TOF (matrix-assisted laser desorption ionization-time-of-flight) MS that this thiol compound also corresponds to the characteristic monoprotonated ion of trypanothione-(bimane)(2), which has a molecular ion of m/z 1103.95. The ion pattern of the thiol-bimane compound prepared from the commercial trypanothione standard is identical with the E. histolytica thiol-bimane compound. After HPLC separation, chemical amino acid analysis by dabsylation and dansylation of the thiol bimane compound from Entamoeba showed the presence of the following trypanothione components: glutamic acid, cysteic acid, glycine and spermidine. We can conclude from these highly reliable MS experiments and chemical analyses that E. histolytica contains the thiol compound trypanothione, which was previously thought to occur only in trypanosomatids.

[A new synthesis of alpha-methylspermidine]

A five-step synthesis of alpha-methylspermidine (1,8-diamino-5-azanonane), the first polyamine analogue preventing pathological consequences of spermidine depletion in transgenic rats overproducing spermine/spermidine N'-acetyltransferase, from ethyl 3-aminobutyrate was achieved in a high overall yield.

The genome of the African trypanosome Trypanosoma brucei

African trypanosomes cause human sleeping sickness and livestock trypanosomiasis in sub-Saharan Africa. We present the sequence and analysis of the 11 megabase-sized chromosomes of Trypanosoma brucei. The 26-megabase genome contains 9068 predicted genes, including approximately 900 pseudogenes and approximately 1700 T. brucei-specific genes. Large subtelomeric arrays contain an archive of 806 variant surface glycoprotein (VSG) genes used by the parasite to evade the mammalian immune system. Most VSG genes are pseudogenes, which may be used to generate expressed mosaic genes by ectopic recombination. Comparisons of the cytoskeleton and endocytic trafficking systems with those of humans and other eukaryotic organisms reveal major differences. A comparison of metabolic pathways encoded by the genomes of T. brucei, T. cruzi, and Leishmania major reveals the least overall metabolic capability in T. brucei and the greatest in L. major. Horizontal transfer of genes of bacterial origin has contributed to some of the metabolic differences in these parasites, and a number of novel potential drug targets have been identified.

Role of the ABC transporter MRPA (PGPA) in antimony resistance in Leishmania infantum axenic and intracellular amastigotes

Antimonial compounds are the mainstay for the treatment of infections with the protozoan parasite Leishmania. We present our studies on Leishmania infantum amastigote parasites selected for resistance to potassium antimonyl tartrate [Sb(III)]. Inside macrophages, the Sb(III)-selected cells are cross-resistant to sodium stibogluconate (Pentostam), the main drug used against Leishmania. Putative alterations in the level of expression of more than 40 genes were compared between susceptible and resistant axenic amastigotes using customized DNA microarrays. The expression of three genes coding for the ABC transporter MRPA (PGPA), S-adenosylhomocysteine hydrolase, and folylpolyglutamate synthase was found to be consistently increased. The levels of cysteine were found to be increased in the mutant. Transfection of the MRPA gene was shown to confer sodium stibogluconate resistance in intracellular parasites. This MRPA-mediated resistance could be reverted by using the glutathione biosynthesis-specific inhibitor buthionine sulfoximine. These results highlight for the first time the role of MRPA in antimony resistance in the amastigote stage of the parasite and suggest a strategy for reversing resistance.

Dihydrocaffeoyl polyamines (kukoamine and allies) in potato (Solanum tuberosum) tubers detected during metabolite profiling

Four related phenolic amides previously undescribed from the species were revealed during metabolic profiling of potato (Solanum tuberosum) tubers. N(1),N(12)-Bis(dihydrocaffeoyl)spermine (kukoamine A) and N(1),N(8)-bis(dihydrocaffeoyl)spermidine were positively identified by comparison with authentic standards, while the structures N(1),N(4),N(12)-tris(dihydrocaffeoyl)spermine and N(1),N(4),N(8)-tris(dihydrocaffeoyl)spermidine are proposed for the other two metabolites. Each amide was present at several tens of micrograms per gram of dry matter. Several of these compounds were subsequently detected in other solanaceous species, such as tomato (Lycopersicon esculentum) and Nicotiana sylvestris. They appeared not to be present in Arabidopsis thaliana or Beta vulgaris. Bis(dihydrocaffeoyl)spermine isomers have previously been identified in only a single plant, the Chinese medicinal species Lycium chinense (Solanaceae), where they may account for some of the described biological activity. The other compounds have not until now been reported in vivo, though some of the equivalent hydroxycinnamoyl derivatives are known. The surprising discovery of kukoamine and allies in a range of solanaceous species including potato, a common food crop that has a long history of scientific investigation, provides exemplary evidence for the potential of the nontargeted techniques of metabolomics in studying plant metabolites.

Immunological alterations induced by polyamine derivatives on murine splenocytes and human mononuclear cells

Three polyamine derivatives assigned as bis-naphthalimidopropyl putrescine (BNIPPut), spermidine (BNIPSpd) and spermine (BNIPSpm) were studied to determine their effects on the proliferation of murine splenocytes and human peripheral blood mononuclear cells (PBMC) induced by the mitogens, Con A, LPS and PHA. All compounds showed a dose dependent inhibitory effect on mouse and human T cell proliferation induced by the mitogens, with BNIPPut exhibiting the most potent antiproliferative activity, followed by BNIPSpd and by BNIPSpm, respectively (Put > Spd > Spm), when considering human T cells. This suppressive activity also affects the capacity of mouse spleen cells to produce Th1 cytokines, namely IL-2 and INF-gamma after in vitro stimulation with Con A. The polyamine-induced inhibition also occurred in the case of LPS-stimulated B cells with a marked decrease of CD69 expression by these cells. Furthermore, the ability for these polyamine derivatives to induce apoptosis on Con A-stimulated splenocytes could be related to their antiproliferative activity.

Synthesis and Biological Evaluation of Dihydromotuporamine Derivatives in Cells Containing Active Polyamine Transporters

Dihydromotuporamine C (4) and its 4,4-triamine analogue (5) were synthesized in good yield using ring-closing metathesis (RCM) methods. Comparison of their biological activities (Ki determinations in L1210 cells and IC50 determinations in L1210, CHO, and CHO-MG cells) revealed that the motuporamine derivatives do not use the polyamine transporter (PAT) for cellular entry. Bioevaluation of a N1-(anthracen-9-ylmethyl)-N1-(ethyl)homospermidine control (7) revealed that the presence of a N1 tertiary amine center imparted a significant reduction in the PAT affinity of the polyamine conjugate and abolished its PAT-targeting selectivity.

Differential effects of polyamine derivative compounds against Leishmania infantum promastigotes and axenic amastigotes

The natural polyamines are ubiquitous polycationic compounds that play important biological functions in cell growth and differentiation. In the case of protozoan species that are causative agents of important human diseases such as Leishmaniasis, an exogenous supply of polyamines supports parasite proliferation. In the present study, we have investigated the effect of three polyamine derivatives, (namely bis-naphthalimidopropyl putrescine (BNIPPut), spermidine (BNIPSpd) and spermine (BNIPSpm)), on the proliferative stages of Leishmania infantum, the causative agent of visceral leishmaniasis in the Mediterranean basin. A significant reduction of promastigotes and axenic amastigotes growth was observed in the presence of increasing concentrations of the drugs, although the mechanisms leading to the parasite growth arrest seems to be different. Indeed, by using a number of biochemical approaches to analyse the alterations that occurred during early stages of parasite-drug interaction (i.e. membrane phosphatidylserine exposure measured by annexin V binding, DNA fragmentation, deoxynucleotidyltranferase-mediated dUTP end labelin (TUNEL), mitochondrial transmembrane potential loss), we showed that the drugs had the capacity to induce the death of promastigotes by a mechanism that shares many features with metazoan apoptosis. Surprisingly, the amastigotes did not behave in a similar way to promastigotes. The drug inhibitory effect on amastigotes growth and the absence of propidium iodide labelling may suggest that the compounds are acting as cytostatic substances. Although, the mechanisms of action of these compounds have yet to be elucidated, the above data show for the first time that polyamine derivatives may act differentially on the Leishmania parasite stages. Further chemical modifications are needed to make the polyamine derivatives as well as other analogues able to target the amastigote stage of the parasite.

Trypanothione reductase from the human parasite Entamoeba histolytica: a new drug target

Although there is a general agreement that the protist Entamoeba histolytica lacks glutathione, it has been a matter of dispute as to whether this human parasite contains the glutathione derivative known as trypanothione. In the present study, we describe a gene for the TR (trypanothione reductase) obtained from E. histolytica by PCR amplification of its DNA. After Northern-blot analysis, the radiolabelled DNA probe from Trypanosoma cruzi hybridizes with the total RNA of Entamoeba, showing that the TR gene is expressed as mRNA. We have demonstrated the presence of the NADPH-dependent TR activity in vitro with partially purified extracts and showed also that the thiol-bimane compound isolated and purified from E. histolytica trophozoites, unequivocally corresponds, by matrix-assisted laser-desorption ionization-time-of-flight MS, to the characteristic monoprotonated ion of trypanothione-(bimane)(2) with m/z 1104.4 and the trypanothione-(bimane) with m/z 914.3. The PCR product consisted of 1476 bp (491 deduced amino acids), has sequences diagnostic for the reducing catalytic site (CVNVGC) as well as domains for binding NADPH, FAD I and FAD II that are present in all members of this group of disulphide-reducing enzymes, as well as those unique to TRs. The putative protein sequence is 86% identical with that of TR from T. cruzi and it is also clearly distinguishable from other related reductases by phylogenetic analysis. We can conclude, from these highly reliable experiments, that E. histolytica contains the TR enzyme and the thiol compound trypanothione that was previously supposed to occur only in trypanosomatids.

Expression, purification, and characterization of Leishmania donovani trypanothione reductase in Escherichia coli

Trypanothione reductase (TR) is an NADPH-dependent flavoprotein oxidoreductase central to thiol metabolism in all the trypanosomatids including Leishmania. The unique presence of this enzyme in trypanosomatids and absence in mammalian host make this enzyme an attractive target for the development of the antileishmanials. Complete open reading frame encoding trypanothione reductase from Leishmania donovani (Dd8 strain, causative agent of Indian visceral leishmaniasis) was cloned, sequenced, and expressed in Escherichia coli strain BL21 (DE3) as glutathione S-transferase fusion protein. The conditions were developed for overexpression of fusion protein in soluble form and purification of the recombinant protein to homogeneity. The recombinant LdTR was 54.68 kDa in size, dimeric in nature, and reduces oxidized trypanothione to reduced form. The kinetic parameters for trypanothione disulfide are K(m), 50 microM; k(cat), 18,181 min(-1); and k(cat)/K(m), 6.06x10(6) M(-1) s(-1). The yield of recombinant LdTR was approximately 16 mg/L bacterial culture and accounted for 6% of the total soluble proteins. The expressed protein was inhibited by known TR inhibitors as well as by SbIII, the known antileishmanial compound. This is the first report of large-scale production of any leishmanial TR in E. coli.

Immunoelectron microscopy study of polyamines using a newly prepared monoclonal antibody against spermidine: use of a mixture of glutaraldehyde and paraformaldehyde as a cross-linking agent in the preparation of the antigen

We developed a mouse monoclonal antibody (ASPD-19, IgG3 sub-isotype mAb) against spermidine (Spd) conjugated to bovine serum albumin (BSA) using a mixture of glutaraldehyde (GA) and paraformaldehyde (PFA)-sodium borohydride for applications in immunoelectron microscopic studies. The antibody specificity was evaluated by an ELISA binding test simulating the immunocytochemistry (ICC) of tissue sections. The ASPD-19 mAb is highly specific for Spd and Spm, almost the same degree to each, and can distinguish alterations in the chemical structure of other polyamine (PA) analogs, showing less than 3.2% cross-reaction with N(1)-acetylspermidine, acetylspermine, or N(8)-acetylspermidine. By an indirect immunoperoxidase method using the ASPD-19 mAb, PA-like immunoreactivities were observed in different tissues fixed with Karnovsky fixative (a mixture of GA and PFA) in combination with borohydride reduction. In contrast, immunoreactivity was very low in tissues when the borohydride reduction step was omitted. The PA-like immunoreaction was completely abolished by the adsorption of the ASPD-19 mAb with 100 microg/ml of Spd or Spm, but was inhibited little or none by other PA-related compounds or amino acids. A light microscopic ICC method using ASPD-19 produced immunostaining of PAs in certain cells in rat tissues with high biosynthetic activities (small intestine, pancreas and spinal cord). A pre-embedding immunoelectron microscopic study using rat spinal cord showed PA immunoreactivity located predominantly on free (polysomes) and attached ribosomes of the rough endoplasmic reticulum (Nissl bodies) in the cytoplasm of motor neurons. These results are in complete agreement with the results obtained by our recent ICC method using another mAb (ASPM-29) produced against GA-conjugated Spm.

Metabolic stability of alpha-methylated polyamine derivatives and their use as substitutes for the natural polyamines

Metabolically stable polyamine derivatives may serve as useful surrogates for the natural polyamines in studies aimed to elucidate the functions of individual polyamines. Here we studied the metabolic stability of alpha-methylspermidine, alpha-methylspermine, and bis-alpha-methylspermine, which all have been reported to fulfill many of the putative physiological functions of the natural polyamines. In vivo studies were performed with the transgenic rats overexpressing spermidine/spermine N(1)-acetyltransferase. alpha-Methylspermidine effectively accumulated in the liver and did not appear to undergo any further metabolism. On the other hand, alpha-methylspermine was readily converted to alpha-methylspermidine and spermidine; similarly, bis-alpha-methylspermine was converted to alpha-methylspermidine to some extent, both conversions being inhibited by the polyamine oxidase inhibitor N(1), N(2)-bis(2,3-butadienyl)-1,4-butanediamine. Furthermore, we used recombinant polyamine oxidase, spermidine/spermine N(1)-acetyltransferase, and the recently discovered spermine oxidase in the kinetic studies. In vitro studies confirmed that methylation did not protect spermine analogs from degradation, whereas the spermidine analog was stable. Both alpha-methylspermidine and bis-alpha-methylspermine overcame the proliferative block of early liver regeneration in transgenic rats and reversed the cytostasis induced by an inhibition of ornithine decarboxylase in cultured fetal fibroblasts.

Trypanothione biosynthesis in Leishmania major

Trypanothione plays a crucial role in regulation of intracellular thiol redox balance and in defence against chemical and oxidant stress. Crithidia fasciculata requires two enzymes for the formation of trypanothione, namely glutathionylspermidine synthetase (GspS; EC 6.3.1.8) and a glutathionylspermidine-dependent trypanothione synthetase (TryS; EC 6.3.1.9), whereas Trypanosoma cruzi and Trypanosoma brucei use a broad-specificity trypanothione synthetase to make trypanothione from glutathione (GSH) and spermidine. Here, we report the identification of two genes in Leishmania major with similarity to previously identified GSPS and TRYS. GSPS is an apparent pseudogene containing two frame shift mutations and two stop codons, whereas TRYS is in a single open-reading frame. The enzyme encoded by TRYS was expressed and found to catalyse formation of trypanothione with GSH and either spermidine or glutathionylspermidine. When GSH is varied as substrate the enzyme displays substrate inhibition (apparent Km=89 microM, Ki(s)=1mM, k(cat)=2s-1). At a fixed GSH concentration, the enzyme obeys simple hyperbolic kinetics with the other substrates with apparent Km values for spermidine, glutathionylspermidine and MgATP of 940, 40 and 63 microM, respectively. Immunofluorescence and sub-cellular fractionation studies indicate that TryS localises to the cytosol of L. major promastigotes. Phylogenetic analysis of the GspS and TryS amino acid sequences suggest that in the trypanosomatids, TryS has evolved to replace the GspS/TryS complex in C. fasciculata. It also appears that the L. major still harbours a redundant GSPS pseudogene that may be currently in the process of being lost from its genome.

Trypanothione synthesis in crithidia revisited

In Crithidia fasciculata the biosynthesis of trypanothione (N(1),N(8)-bis(glutathionyl)spermidine; reduced trypanothione), a redox mediator unique to and essential for pathogenic trypanosomatids, was assumed to be achieved by two distinct enzymes, glutathionylspermidine synthetase and trypanothione synthetase (TryS), and only the first one was adequately characterized. We here report that the TryS of C. fasciculata, like that of Trypanosoma species, catalyzes the entire synthesis of trypanothione, whereas its glutathionylspermidine synthetase appears to be specialized for Gsp synthesis. A gene (GenBanktrade mark accession number AY603101) implicated in reduced trypanothione synthesis of C. fasciculata was isolated from genomic DNA and expressed in Escherichia coli as His-tagged or Nus fusion proteins. The expression product proved to be a trypanothione synthetase (Cf-TryS) that also displayed a glutathionylspermidine synthetase, an amidase, and marginal ATPase activity. The dual specificity of the Cf-TryS preparations was not altered by removal of the tags. Steady-state kinetic analysis of Cf-TryS yielded a pattern that was compatible with a concerted substitution mechanism, wherein the enzyme forms a ternary complex with Mg(2+)-ATP and GSH to phosphorylate GSH and then ligates the glutathionyl residue to glutathionylspermidine. Limiting K(m) values for GSH, Mg(2+)-ATP, and glutathionylspermidine were 407, 222, and 480 microm, respectively, and the k(cat) was 8.7 s(-1) for the TryS reaction. Mutating Arg-553 or Arg-613 to Lys, Leu, Gln, or Glu resulted in marked reduction or abrogation (R553E) of activity. Limited proteolysis with factor Xa or trypsin resulted in cleavage at Arg-556 that was accompanied by loss of activity. The presence of substrates, in particular of ATP and GSH alone or in combination, delayed proteolysis of wild-type Cf-TryS and Cf-TryS R553Q but not in Cf-TryS R613Q, which suggests dynamic interactions of remote domains in substrate binding and catalysis.

Interhelical spacing in liquid crystalline spermine and spermidine-DNA precipitates

The structure of polyamines-DNA precipitates was studied by x-ray diffraction. Precise measurements of the interhelix distance a(H) were obtained at different NaCl, polyamine, and DNA concentrations. Most of the results were obtained using spermine and few others using spermidine. The precipitates are liquid crystalline, either hexagonal and/or cholesteric, with an interhelical spacing that depends on the ionic concentrations and on the polyamine type. In our experimental conditions, the spacing varies from 28.15 to 33.4 angstroms. This variation is interpreted in terms of different ionic components that are present inside the precipitates and that are thought to regulate the value of the cohesive energy of DNA. These results are discussed in relation to the biological processes requiring a closeness of double helices and to the role played by polyamine analogs in cancer therapy.

A trypanothione-dependent glyoxalase I with a prokaryotic ancestry in Leishmania major

Glyoxalase I forms part of the glyoxalase pathway that detoxifies reactive aldehydes such as methylglyoxal, using the spontaneously formed glutathione hemithioacetal as substrate. All known eukaryotic enzymes contain zinc as their metal cofactor, whereas the Escherichia coli glyoxalase I contains nickel. Database mining and sequence analysis identified putative glyoxalase I genes in the eukaryotic human parasites Leishmania major, Leishmania infantum, and Trypanosoma cruzi, with highest similarity to the cyanobacterial enzymes. Characterization of recombinant L. major glyoxalase I showed it to be unique among the eukaryotic enzymes in sharing the dependence of the E. coli enzyme on nickel. The parasite enzyme showed little activity with glutathione hemithioacetal substrates but was 200-fold more active with hemithioacetals formed from the unique trypanosomatid thiol trypanothione. L. major glyoxalase I also was insensitive to glutathione derivatives that are potent inhibitors of all other characterized glyoxalase I enzymes. This substrate specificity is distinct from that of the human enzyme and is reflected in the modification in the L. major sequence of a region of the human protein that interacts with the glycyl-carboxyl moiety of glutathione, a group that is conjugated to spermidine in trypanothione. This trypanothione-dependent glyoxalase I is therefore an attractive focus for additional biochemical and genetic investigation as a possible target for rational drug design.

Exclusion of alcohols from spermidine-DNA assemblies: probing the physical basis of preferential hydration

The interaction of the alcohols 2-methyl-2,4-pentanediol (MPD) and 2-propanol and of glycerol with condensed spermidine(3+)-DNA arrays are investigated with direct force measurements using osmotic stress coupled with X-ray scattering. Thermodynamic forces between DNA helices are measured from the dependence of helical interaxial spacings on the osmotic pressure applied by poly(ethylene glycol) solutions in equilibrium with the DNA phase. The sensitivity of these forces to solute concentration can be transformed into a change in the number of excess or deficit solutes or waters in the DNA phase by applying the Gibbs-Duhem equation. The alcohols examined are excluded from the condensed DNA array and strongly affect the osmotic stress force curves. DNA is preferentially hydrated. MPD is significantly more excluded than 2-propanol. The exclusion of these alcohols, however, is not due to a steric repulsion since glycerol that is intermediate in size between MPD and 2-propanol does not observably affect DNA force curves. As the distance between DNA helices varies, the change in the number of excess waters is independent of alcohol concentration for each alcohol. These solutes are acting osmotically on the condensed array. The distance dependence of exclusion indicates that repulsive water structuring forces dominate the interaction of alcohols with the DNA surface. The exclusion measured for these condensed arrays can quantitatively account for the effect of these alcohols on the precipitation of DNA from dilute solution by spermidine(3+).

Polyamines of primitive apterygotan insects: springtails, silverfish and a bristletail

Polyamines extracted from whole bodies of four springtails, Tomocerus ishibashii, Hypogastrura communis, Sinella cruviseta and Folsomia candida, a bristletail, Pedetontus nipponicus, and two silverfish, Lepisma saccharina and Thermobia domestica, were analyzed by high-performance liquid chromatography and gas chromatography. All seven apterous insect species contained putrescine, cadaverine and spermidine as the common major polyamines, detected at the level of micromol/g wet mass. T. ishibashii also contained spermine, S. cruviseta contained norspermidine and norspermine and H. communis, F. candida and P. nipponicus contained diaminopropane, norspermidine and norspermine, as minor polyamines above the detection limit (0.01 micromol/g wet mass). The occurrence of diaminopropane, norspermidine, norspermine, spermine and thermospermine was confirmed in L. saccharina and T. domestica. The novel polyamines norspermidine, norspermine and thermospermine, widespread in higher insects, were also distributed within the primitive apterygotan insects.