Synthesis and antimicrobial activity of symmetrical two-tailed dendritic tricarboxylato amphiphiles

Two series of water-soluble, symmetrical two-tailed homologous dendritic amphiphiles--R(2)NCONHC((CH(2))(2)COOH)(3), 2(n,n), and R(2)CHNHCONHC((CH(2))(2)COOH)(3), 3(n,n), where R=n-C(n)H(2n+1)--were synthesized and compared to R'NHCONHC((CH(2))(2)COOH)(3), 1(n), R'=n-C(n)H(2n+1), to determine whether antimicrobial activity was influenced by total or individual alkyl chain lengths, and whether antimicrobial activity depends on hydrophobicity or tail topology (one or two). In a broad screen of 11 microorganisms, 2(n,n) and 3(n,n) generally displayed higher minimal inhibitory concentrations (MICs) than 1(n) against growth as measured by broth microdilution assays. Chain-length specificity was observed against Candida albicans as 1(16), 2(8,8), and 3(8,8) showed the lowest MIC in their respective series. The one case where two-tailed compounds displayed the lowest MICs-3(10,10), 15 microM; 3(11,11), 7.2microM; and 3(12,12), 6.9 microM-was against Cryptococcus neoformans.     

Diiron models for the active site of Fe-only hydrogenase with terminal organosulfur ligation: synthesis, structures and electrochemistry

Diiron model complexes (micro-SCH(2)CH(2)CH(2)S)Fe(2)(CO)(5)L with thioether-substitution, L=S(CH(2)CH(3))(2) (2), S(CH(2)CH(3))(CH(2)CH(2)Cl) (3), S(CH(2)CH(3))(C(6)H(5)) (4), or sulfoxide-substitution, L=SO(CH(2)CH(2)CH(3))(2) (5), SO(CH(3))(2) (6), were synthesized as active site analogues of Fe-only hydrogenase. The organosulfur ligands were introduced into the diiron centers via moderately stable intermediates following two routes. The X-ray crystallographic structures of complexes 2-6 show the apical positions of terminal organosulfur ligands. The electrochemical behaviors of the model complexes were investigated, especially for the interesting properties of the derivative of 6 which is proposed to be the first model with weak donor ligand similar to CO.     

Inducible aluminum resistance of Acidiphilium cryptum and aluminum tolerance of other acidophilic bacteria

Aluminum ions are highly soluble in acidic environments. Toxicity of aluminum ions for heterotrophic, facultatively and obligately chemolithoautotrophic acidophilic bacteria was examined. Acidiphilium cryptum grew in glucose-mineral medium, pH 3, containing 300 mM aluminum sulfate [Al(2)(SO(4))(3)] after a lag phase of about 120 h with a doubling time of 7.6 h, as compared to 5.2 h of growth without aluminum. Precultivation with 1 mM Al(2)(SO(4))(3) and transfer to a medium with 300 mM Al(2)(SO(4))(3) reduced the lag phase from 120 to 60 h, and immediate growth was observed when A. cryptum was precultivated with 50 mM Al(2)(SO(4))(3), suggesting an aluminum-induced resistance. Aluminum resistance was not induced by Fe(3+) ions and divalent cations. Upon exposure of A. cryptum to 300 mM Al(2)(SO(4))(3), the protein profile changed significantly as determined by SDS-PAGE. When other acidophiles were cultivated with 50-200 mM aluminum sulfate, no lag phase was observed while the growth rates and the cellular yields were significantly reduced. This growth response was observed with Acidobacterium capsulatum, Acidiphilium acidophilum, Acidithiobacillus ferrooxidans, and Acidithiobacillus thiooxidans. Precultivation of these strains with aluminum ions did not alter the growth response caused by aluminum. The content of A. cryptum cultivated with 300 mM Al(2)(SO(4))(3)was 0.44 microg Al/mg cell dry weight, while that of the other strains cultivated with 50 mM Al(2)(SO(4))(3) ranged from 0.30 to 3.47 microg Al/mg cell dry weight.     

The preparation,characterisation and in vitro cytotoxicity of potentially chemotherapeutic heterobimetallic complexes containing early and late transition metals

The reactions of phosphine Ph(2)P(CH(2))(2)SO(3)Na with Cp(2)M'Cl(2) (M'=Ti, Zr) in aqueous solution give the metallophosphines, Cp(2)Ti(OSO(2)(CH(2))(2)PPh(2))(2) (Cp=cyclopentadienyl) and CpZr(OH)(OSO(2)(CH(2))(2)PPh(2))(2). These react with CODM"Cl(2) (M"=Pd, Pt) (COD=1,5-cyclooctadiene) in dichloromethane to give heterobimetallic complexes Cp(2)Ti(OSO(2)(CH(2))(2)PPh(2))(2)M"Cl(2) and CpZr(OH)(OSO(2)(CH(2))(2) PPh(2))(2)M"Cl(2) respectively. The compounds are characterised by infrared and NMR spectroscopies and elemental analysis. Electrospray mass spectra of the complexes are reported and compared to those of Cp(2)M'Cl(2) in water and dimethylsulfoxide (DMSO). For zirconocene dichloride and its product heterobimetallic complexes, the addition of ethylenediamine tetraacetic acid disodium salt (Na(2)H(2)EDTA) was found to be an effective ionisation enhancement agent for the electrospray mass spectral studies. Cytotoxicity studies for the previously reported Cl(2)Pt(PPh(2)(CH(2))(2)SO(3)H)(2).3.5H(2)O (Wedgwood et al., Inorg. Chim. Acta 290 (1999) 189), and the compounds Cp(2)Ti(OSO(2)(CH(2))(2) PPh(2))(2).1.5H(2)O and Cp(2)Ti(OSO(2)(CH(2))(2)PPh(2))(2)PtCl(2).4H(2)O reported here, have been evaluated by colony formation assay against cisplatin-sensitive and -resistant cell lines L929 and L929/R to highlight potential chemotherapeutic activity. The compound Cl(2)Pt(PPh(2)(CH(2))(2)SO(3)H)(2).3.5H(2)O overcomes cisplatin resistance.     

[35S]Thiosulphate oxidation by Thiobacillus strain C

1. Thiobacillus strain C oxidized [(35)S]thiosulphate completely to sulphate. 2. During thiosulphate oxidation [(35)S]sulphate was formed more rapidly from (S.(35)SO(3))(2-) than from ((35)S.SO(3))(2-). (35)S disappeared less rapidly from thiosulphate with ((35)S.SO(3))(2-) as substrate than with (S.(35)SO(3))(2-). 3. Thiosulphate labelled in both atoms was produced during ((35)S.SO(3))(2-) oxidation, but not during (S.(35)SO(3))(2-) oxidation. 4. No (35)S was precipitated as elementary sulphur either in the presence or absence of exogenous unlabelled sulphur. 5. During [(35)S]thiosulphate oxidation, appreciable quantities of [(35)S]trithionate accumulated and later disappeared. Other polythionates did not accumulate consistently. 6. [(35)S]Trithionate was formed initially at a greater rate from (S.(35)SO(3))(2-) than from ((35)S.SO(3))(2-), but subsequently at a similar rate from each. 7. Trithionate formed from (S.(35)SO(3))(2-) was labelled only in the oxidized sulphur atoms, but that formed from ((35)S.SO(3))(2-) was labelled in both oxidized and reduced atoms. The proportion of (35)S in the oxidized atoms increased as more trithionate accumulated. 8. The results eliminate some mechanisms of trithionate formation but are consistent both with a mechanism of thiosulphate oxidation based on an initial reductive cleavage of the molecule and with a mechanism in which thiosulphate undergoes an initial oxidative reaction.     

Size of the aliphatic chain of sodium houttuyfonate analogs determines their affinity for renin and angiotensin I converting enzyme

Sodium houttuyfonate analogs (SHAs), CH(3)-(CH(2))(n)-CO-CH(2)-CH(OH)SO(3)Na, (n=6-14) were synthesized and their molecular interactions with renin and angiotensin I converting enzyme (ACE) studied using fluorescence quenching techniques. Unlike renin, inhibition of ACE activity was not directly proportional to the aliphatic chain length of SHAs. Ability of SHAs to inhibit enzyme activities and quench protein fluorescence was greater with renin than with ACE. The presence of an ACE substrate (angiotensin I) did not reduce quenching ability of SHAs, suggesting that enzyme-inhibitor interactions did not involve the active site or the substrate was displaced by inhibitor molecules. The results showed that renin is a more sensitive target than ACE for the potential antihypertensive ability of SHAs.     

Comparing micellar, hemolytic, and antibacterial properties of di- and tricarboxyl dendritic amphiphiles

Homologous dicarboxyl dendritic amphiphiles-RCONHC(CH(3))(CH(2)CH(2)COOH)(2), 4(n); and ROCONHC(CH(3))(CH(2)CH(2)COOH)(2), 5(n), where R=n-C(n)H(2)(n)(+1) and n=13-22 carbon atoms-were synthesized. Critical micelle concentrations (CMCs) in aqueous triethanolamine solutions and at pH 7.4 were measured along with hemolytic activity (effective concentrations, EC(10)) in phosphate-buffered saline (PBS). LogCMC showed a linear dependence on chain length (n); the longest chain in each series had the lowest CMC-in triethanolamine: 4(21), 180μM and 5(22), 74μM and at pH 7.4: 4(21), 78μM and 5(22), 33μM. These two series, 4(n) and 5(n), and three series of homologous tricarboxyl dendritic amphiphiles-RCONHC(CH(2)CH(2)COOH)(3), 1(n); ROCONHC(CH(2)CH(2)COOH)(3), 2(n); RNHCONHC(CH(2)CH(2)COOH)(3), 3(n), where R=n-C(n)H(2)(n)(+1) and n=13-22 carbon atoms-were tested for growth inhibition of Staphylococcus aureus strain ATCC 6358 and methicillin-resistant S. aureus (MRSA) strain ATCC 43330 by microdilution in 0.1-strength brain heart infusion broth (BHIB). Amphiphiles 4(19), 4(21), 5(18), and 5(20) showed the strongest antibacterial activity (2.2-3.4μg/mL) against S. aureus (vancomycin, MIC=0.25μg/mL). These four plus 1(21), 2(20), 2(22), and 3(20) exhibited the strongest antibacterial activity (1.7-6.8μg/mL) against MRSA (vancomycin, MIC=0.25μg/mL). The MICs of these amphiphiles against six clinical MRSA were similar to those against the ATCC strain. In PBS, EC(10)s of the most active homologues ranged from 7 to 18μg/mL and 18 to 220μg/mL for di- and tricarboxyl dendritic amphiphiles, respectively. To assess the potential safety of using dendritic amphiphiles as drugs, measurements of micellar and hemolytic properties were conducted in the same medium (full-strength BHIB) that was used for antibacterial activity. The CMCs (9-36μg/mL, ～18-72μM) of ten amphiphiles were measured by microdilution (log2 progression) with dye-covered beads. The EC(10)s were similar to those in PBS. The MICs of most amphiphiles (14-72μg/mL) and vancomycin (1.1-2.2μg/mL) against both S. aureus and MRSA increased significantly compared to the MICs measured in 0.1-strength BHIB. The one exception, 5(18), had an MIC against S. aureus of 1.1μg/mL compared to vancomycin (2.2μg/mL). With CMC (9-18μg/mL) and EC(10) (16μg/mL) values higher than the MIC, 5(18) was discovered as a lead for further development.     

[35S]Thiosulphate oxidation by rat liver mitochondria in the presence of glutathione

1. Rat liver mitochondria incubated in oxygen with glutathione and [(35)S]-thiosulphate produced labelled sulphate. 2. Inner-labelled thiosulphate (S.(35)SO(3))(2-) was converted into [(35)S]sulphate more rapidly than outer-labelled thiosulphate ((35)S.SO(3))(2-). 3. Thiosulphate labelled in both sulphur atoms was formed during ((35)S.SO(3))(2-) oxidation; the outer sulphur atom before oxidation to sulphate was incorporated into the inner position. 4. A thiosulphate cycle in the metabolic pathway of sulphate formation in animal tissues is discussed.     

Synthesis,structural characterization and antimicrobial activities of 12 zinc(II) complexes with four thiosemicarbazone and two semicarbazone ligands

Twelve zinc(II) complexes with thiosemicarbazone and semicarbazone ligands were prepared and characterized by elemental analysis, thermogravimetric and differential thermal analysis (TG/DTA), FT-IR and 1H and 13C NMR spectroscopy. Seven three-dimensional structures of zinc(II) complexes were determined by single-crystal X-ray analysis. Their antimicrobial activities were evaluated by MIC against four bacteria (B. subtilis, S. aureus, E. coli and P. aeruginosa), two yeasts (C. albicans and S. cerevisiae) and two molds (A. niger and P. citrinum). The 5- and 6-coordinate zinc(II) complexes with a tridentate thiosemicarbazone ligand (Hatsc), ([Zn(atsc)(OAc)](n) 1, [Zn(Hatsc)(2)](NO(3))(2).0.3H(2)O 2, [ZnCl(2)(Hatsc)] 3 and [Zn(SO(4))(Hatsc)(H(2)O)].H(2)O 4 [Hatsc=2-acetylpyridine(thiosemicarbazone)]), showed antimicrobial activities against test organisms, which were different from those of free ligands or the starting zinc(II) compounds. Especially, complex 2 showed effective activities against P. aeruginosa, C. albicans and moderate activities against S. cerevisiae and two molds. These facts are in contrast to the results that the 5- or 6-coordinate zinc(II) complexes with a tridentate 2-acetylpyridine-4N-morpholinethiosemicarbazone, ([Zn(mtsc)(2)].0.2EtOH 5, the previously reported catena-poly [Zn(mtsc)-mu-(OAc-O,O')](n) and [Zn(NO(3))(2)(Hmtsc)] [Hmtsc=2-acetylpyridine (4N-morpholyl thiosemicarbazone)]), showed no activities against the test microorganisms. The 5- and 6-coordinate zinc(II) complexes with a tridentate 2-acetylpyridinesemicarbazone, ([Zn(OAc)(2)(Hasc)] 6 and [Zn(Hasc)(2)](NO(3))(2) 7 [Hasc=2-acetylpyridine(semicarbazone)]), showed no antimicrobial activities against bacteria, yeasts and molds. Complex [ZnCl(2)(Hasc)] 8, which was isostructural to complex 3, showed modest activity against Gram-positive bacterium, B. subtilis. The 1:1 complexes of zinc(II) with pentadentate thiosemicarbazone ligands, ([Zn(dmtsc)](n) 9 and [Zn(datsc)](n) 10 [H(2)dmtsc=2,6-diacetylpyridine bis(4N-morpholyl thiosemicarbazone) and H(2)datsc=2,6-diacetylpyridine bis(thiosemicarbazone)]), did not inhibit the growth of the test organisms. On the contrary, 7-coordinate zinc(II) complexes with one pentadentate semicarbazone ligand and two water molecules, ([Zn(H(2)dasc)(H(2)O)(2)](OAc)(2).5.3H(2)O 11 and [Zn(H(2)dasc)(H(2)O)(2)](NO(3))(2).H(2)O 12 [H(2)dasc=2,6-diacetylpyridine bis(semicarbazone)]), showed modest to moderate activities against bacteria. Based on the X-ray structures, the structure-activity correlation for the antimicrobial activities was elucidated. The zinc(II) complexes with 4N-substituted ligands showed no antimicrobial activities. In contrast to the previously reported nickel(II) complexes, properties of the ligands such as the ability to form hydrogen bonding with a counter anion or hydrated water molecules or the less bulkiness of the 4N moiety would be a more important factor for antimicrobial activities than the coordination number of the metal ion for the zinc(II) complexes.     

Derivatives of oxoisoaporphine alkaloids: a novel class of selective acetylcholinesterase inhibitors

A series of 9-aminoalkanamido-1-azabenzanthrones derviatives (3a-i Ar-NHCO(CH(2))(n)NR(1)R(2)) and their quaternary methiodide salts (4a-g Ar-NHCO(CH(2))(n)N(+)(CH(3))R(1)R(2)I(-)) were designed and synthesized as acetylcholinesterase (AChE) or butyrylcholinesterase (BuChE) inhibitors. The synthetic compounds exhibited high AChE inhibitory activity with IC(50) values in the nanomolar range and high selectivity for AChE over BuChE (45- to 1980-fold). The structure-activity relationships (SARs) were discussed.     

Methane oxidation by cell-free extracts of Methylococcus capsulatus

The separation of two distinct forms of cytochrome P450 from adrenal cortex mitochondria has been achieved by the following steps; (1) lyophilisation (2) iso-octane extraction, (3) (NH(4))(2)SO(4) fractionation in the presence of sodium cholate. The fraction precipitating between 25-35 percent (NH(4))(2)SO(4) gave a difference spectrum with 11-deoxycorticosterone (11-DOC) but not with 20alpha-hydroxycholesterol (20alpha-HOC). This fraction showed high 11beta-hydroxylase activity but low activity for side chain cleavage of cholesterol (S.C.C.). The fraction precipitating between 45-60 percent (NH(4))(2)SO(4) gave a difference spectrum with 20alpha-HOC but not with 11-DOC and exhibited high S.C.C. activity but low 11beta-hydroxylase activity. The absorption spectrum of the 45-60 percent fraction indicated a preponderance of high spin hemoprotein (lambda(max) 395 nm).     

Fatty acyl-gramicidin S derivatives with both high antibiotic activity and low hemolytic activity

In the present study, novel eight GS derivatives having the octanoyl-(Lys)(n)- moieties, cyclo{-Val-Orn-Leu-d-Phe-Pro(4β-NH-X)-Val-Orn-Leu-d-Phe-Pro-} {X=-H (1), and -(Lys)(n)-CO(CH(2))(6)CH(3)n=0 (2), 1 (3), 2 (4), and 3 (5)} and cyclo{-Val-Orn-Leu-d-Phe-Pro(4α-NH-X)-Val-Orn-Leu-d-Phe-Pro-} {X=-H (6), and -(Lys)(n)-CO(CH(2))(6)CH(3)n=1 (7), and 2 (8)} were synthesized. Among them, 4, 5 and 8 result the high antibiotic activity against both Gram-positive and Gram-negative microorganisms tested. In addition, 4 and 5 showed very low hemolytic activity compared with that of GS. Thus, the introduction of the excess amino groups and the fatty acyl moiety to the γ-NH(2) group of Pro(5) residue in GS molecule lowered the unwanted hemolytic activity and enhanced the desired antibiotic activity.     

Study on the amount of binding of anti-tumor metal complexes to different target sites of dGMP using trans-[en(2)Os(eta2-H(2))(CF(3)SO(3))](CF(3)SO(3)) in a competitive mode

In order to investigate the binding sites and the amount of binding of a number of anti-tumor metal complexes (cisplatin, Cp(2)TiCl(2) and (CH(3))(2)SnCl(2)) to target molecule DNA mononucleotides in aqueous solution, a 1H NMR recognition probe, trans-[en(2)Os(eta2-H(2))(CF(3)SO(3))](CF(3)SO(3)), was used in a competitive mode. The minimum percentages of binding of anti-tumor metal complexes to different sites of dGMP were also determined.     

Analysis of the interaction between lectins and tetra- and tri-saccharide mimics of the Sd(a) determinant by surface plasmon resonance detection

The binding properties of a spacer-linked synthetic Sd(a) tetrasaccharide beta-D-GalpNAc-(1-->4)-alpha-Neu5Ac-(2-->3)]-beta-D-Galp-(1-->4)-beta-D-GlcpNAc-(1-->O)-(CH(2))(5)-NH(2) (1), two tetrasaccharide mimics beta-D-Galp-(1-->4)-alpha-Neu5Ac-(2-->3)]-beta-D-Galp-(1-->4)-beta-D-GlcpNAc-(1-->O)-(CH(2))(5)-NH(2) (2) and beta-D-GlcpNAc-(1-->4)-alpha-Neu5Ac-(2-->3)]-beta-D-Galp-(1-->4)-beta-D-GlcpNAc-(1-->O)-(CH(2))(5)-NH(2) (3), and two trisaccharide mimics beta-D-GalpNAc-(1-->4)-3-O-(SO(3)H)-beta-D-Galp-(1-->4)-beta-D-GlcpNAc-(1-->O)-(CH(2))(5)-NH(2) (4) and beta-D-GalpNAc-(1-->4)-3-O-(CH(2)COOH)-beta-D-Galp-(1-->4)-beta-D-GlcpNAc-(1-->O)-(CH(2))(5)-NH(2) (5) with lectins from Dolichos biflorus (DBL), Maackia amurensis (MAL), Phaseolus limensis (PLL), Ptilota plumosa (PPL), Ricinus communis 120 (RCL120) and Triticum vulgaris (wheat germ agglutinin, WGA) have been investigated by surface plasmon resonance (SPR) detection. MAL, PPL, RCL120 and WGA did not display any binding activity with compounds 1-5. However, DBL and PLL, both exhibiting GalNAc-specificity, showed strong binding activity with compounds 1, 4 and 5, and 1, 3, 4 and 5, respectively. The results demonstrate that SPR is a very useful analysis system for identifying biologically relevant oligosaccharide mimics of the Sd(a) determinant.     

Acylspermidine derivatives isolated from a soft coral,Sinularia sp,inhibit plant vacuolar H(+)-pyrophosphatase

H(+)-pyrophosphatase (H(+)-PPase), which pumps H(+) across membranes coupled with PP(i) hydrolysis, is found in most plants, and some parasitic protists, eubacteria and archaebacteria. We assayed a number of extracts derived from 145 marine invertebrates as to their inhibitory effect on plant vacuolar H(+)-PPase. Acylspermidine derivatives [RCONH(CH(2))(3)N(CH(3))(CH(2))(4)N(CH(3))(2)] from a soft coral (Sinularia sp.) inhibited the PPi-hydrolysis activity of purified H(+)-PPase and the PP(i)-dependent H(+) pump activity (half inhibition concentration, 1 micro M) of vacuolar membranes of mung bean. The apparent K(i) was determined to be 0.9 micro M. Acylspermidines did not affect the activity of vacuolar H(+)-ATPase, plasma membrane H(+)-ATPase, mitochondrial ATPase or cytosolic PPase. Acylspermidines inhibited the acidification of vacuoles in protoplasts, as found on monitoring by the acridine orange fluorescent method. These results indicate that acylspermidine derivatives represent new inhibitors of H(+)-PPase with relatively high specificity.     

Regulation of two aspartokinases in Bacillus subtilis

When grown on minimal glucose medium, transformable Bacillus subtilis strains contained two distinct aspartokinases (ATP:l-aspartate 4-phosphotransferase, EC 2.7.2.4). One of these enzymes was inhibited by l-lysine (Lys), whereas the other was insensitive to inhibition but was activated by l-leucine. None of the other amino acids tested had any effect, and the addition of l-threonine did not enhance the inhibition by Lys, in contrast to the concerted inhibition observed for other bacilli. At the end of exponential growth, the Lys-sensitive aspartokinase activity decreased, whereas the Lys-insensitive activity remained relatively constant throughout the stationary phase. The two activities were separated by (NH(4))(2)SO(4) fractionation and Sephadex G-200 chromatography. Growth in the presence of Lys reduced the specific activity of aspartokinase by about 50% and eliminated the inhibition by Lys. In extracts of these cells, only Lys-insensitive activity was found upon (NH(4))(2)SO(4) fractionation and Sephadex G-200 chromatography. Lys apparently repressed the synthesis of the Lys-sensitive enzyme.     

Chemical and biological characterization of sclerosin, an antifungal lipopeptide

Pseudomonas sp. strain DF41 produces a lipopeptide, called sclerosin that inhibits the fungal pathogen Sclerotinia sclerotiorum . The aim of the current study was to deduce the chemical structure of this lipopeptide and further characterize its bioactivity. Mass spectrometry analysis determined the structure of sclerosin to be CH(3)-(CH(2))(6)-CH(OH)-CH(2)-CO-Dhb-Pro-Ala-Leu/Ile-Ala-Val-Val-Dhb-Thr-Val-Leu/Ile-Dhp-Ala-Ala-Ala-Val-Dhb-Dhb-Ala-Dab-Ser-Val-OH, similar to corpeptins A and B of the tolaasin group, differing by only 3 amino acids in the peptide chain. Subjecting sclerosin to various ring opening procedures revealed no new ions, suggesting that this molecule is linear. As such, sclerosin represents a new member of the tolaasin lipopeptide group. Incubation of S.?sclerotinia ascospores and sclerotia in the presence of sclerosin inhibited the germination of both cell types. Sclerosin also exhibited antimicrobial activity against Bacillus species. Conversely, this lipopeptide demonstrated no zoosporicidal activity against the oomycete pathogen Phytophthora infestans . Next, we assessed the effect of DF41 and a lipopeptide-deficient mutant on the growth and development of Caenorhabditis elegans larvae. We discovered that sclerosin did not protect DF41 from ingestion by and degradation in the C.?elegans digestive tract. However, another metabolite produced by this bacterium appeared to shorten the life-span of the nematode compared to C.?elegans growing on Escherichia coli OP50.     

Influence of protic ionic liquids on the structure and stability of succinylated Con A

We report the synthesis of a series of ionic liquids (ILs) from various ions having different kosmotropicity including dihydrogen phosphate (H(2)PO(4)(-)), hydrogen sulfate (HSO(4)(-)) and acetate (CH(3)COO(-)) as anions and chaotropic cation such as trialkylammonium cation. To characterize the biomolecular interactions of ILs with protein, we have explored the stability of succinylated Con A (S Con A) in the presence of these aqueous ILs, which are varied combinations of kosmotropic anion with chaotropic cation such as triethylammonium dihydrogen phosphate [(CH(3)CH(2))(3)NH][H(2)PO(4)] (TEAP), trimethylammonium acetate [(CH(3))(3)NH][CH(3)COO] (TMAA), trimethylammonium dihydrogen phosphate [(CH(3))(3)NH][H(2)PO(4)] (TMAP) and trimethylammonium hydrogen sulfate [(CH(3))(3)NH][HSO(4)] (TMAS). Circular dichroism (CD) and fluorescence experiments have been used to characterize the stability of S Con A by ILs. Our data distinctly demonstrate that the long alkyl chain IL TEAP is a strong stabilizer for S Con A. Further, our experimental results reveal that TEAP is an effective refolding enhancer for S Con A from a thermally denatured protein structure.     

Response to oxygen limitation in bacteria of the genus sulfobacillus

For cultures of moderately thermophilic chemolithotrophic bacteria Sulfobacillus sibiricus N1 and SSO, S. thermosulfidooxidans subsp. asporogenes 41, and the thermotolerant strain S. thermotolerans Kr1 grown under forced aeration and in a high medium layer without aeration, growth characteristics, substrate consumption, and exometabolite formation were compared. Sulfobacilli grown under oxygen limitation exhibited greater generation time, longer growth period, cell yield decreased by from 40 to 85% (depending on the strain), suppressed cell respiration ( demonstrated for S. sibiricus N1 ), accumulation of exometabolites (acetate and propionate) in the medium, and emergence of resting forms. For strains N1, SSO, and Kr1, oscillations of Fe(II) and Fe(III) content in the medium were revealed. For S. sibiricus N1 and S. thermotolerans Kr1, grown under hypoxia (0.07% O₂ in the gas phase), coupling of substrate oxidation with Fe(III) reduction was revealed, as well as utilization of Fe(III) as an electron acceptor alternative to oxygen. The role of labile energy and constructive metabolism for survival of sulfobacilli under diverse conditions is discussed.     

Studies on the interaction of homologues of spermine with deoxyribonucleic acid and with bacterial protoplasts

Four homologues of the naturally occurring polyamine spermine, of the type H(2)N.[CH(2)](3).NH.[CH(2)] (n).NH.[CH(2)](3).NH(2) where n=2, 3, 5 and 6, have been synthesized. Their ability to stabilize Escherichia coli protoplasts against osmotic lysis was compared with that of spermine. All homologues were approximately as effective as spermine. The effect of low concentrations of the homologues on the T(m) of calf thymus DNA and of Aerobacter aerogenes DNA in 0.03m-sodium chloride-1mm-potassium dimethylglutarate buffer, pH6.2, was tested. The increase in T(m) for a given concentration of amine was found to be n=5>n=4 and n=6> n=3>n=2. When calf thymus DNA in 0.15m-sodium chloride-15mm-sodium citrate was used spermine gave the highest increase in T(m). It is concluded that the stabilization of E. coli protoplasts by tetra-amines is a non-specific effect independent of chain length, whereas the elevation of T(m) of DNA is a more specific effect which depends on chain length.