Biomedical subjects

A Cornish

Publications and source records attributed to A Cornish.

At least 19 recordsLinked to original sources

PubMed2006

Laparoscopic versus open Burch colposuspension: a randomised controlled trial.

OBJECTIVE: To compare perioperative characteristics, short-term, and long-term outcomes for laparoscopic Burch colposuspension (LBC) and open Burch colposuspension (OBC) for the treatment of urinary stress incontinence. DESIGN: Randomised surgical trial with single blinding. SETTING: Three tertiary level teaching hospitals involving seven surgeons of varying skill levels. POPULATION: Two hundred women with urodynamic stress incontinence (USI). METHODS: The two groups were treated in identical fashion, except for the laparoscopic or open approach to surgery. Attempts were made to blind the subjects and the observers obtaining outcome data to treatment group. Analyses were adjusted for surgeon experience. MAIN OUTCOME MEASURES: Absence of USI 6 months following surgery, postoperative pain, time spent in hospital, and time to return to activities of normal daily living. RESULTS: There were no significant differences in objective and subjective measures of cure and in patient satisfaction at 6 months, 24 months, or 3-5 years of follow up between laparoscopic and open colposuspension groups. Laparoscopic colposuspension took longer time to perform (87 versus 42 minutes, P< 0.0001) but was associated with less blood loss (P = 0.03), less pain (P = 0.02), and quicker return to normal activities (P = 0.01). CONCLUSION: LBC has significant advantages over traditional OBC, without any apparent compromise in short-term and long-term outcomes. To compare perioperative characteristics, short-term, and long-term outcomes for laparoscopic Burch colposuspension (LBC) and open Burch colposuspension (OBC) for the treatment of urinary stress incontinence. Randomised surgical trial with single blinding. Three tertiary level teaching hospitals involving seven surgeons of varying skill levels. Two hundred women with urodynamic stress incontinence (USI). The two groups were treated in identical fashion, except for the laparoscopic or open approach to surgery. Attempts were made to blind the subjects and the observers obtaining outcome data to treatment group. Analyses were adjusted for surgeon experience. Absence of USI 6 months following surgery, postoperative pain, time spent in hospital, and time to return to activities of normal daily living. There were no significant differences in objective and subjective measures of cure and in patient satisfaction at 6 months, 24 months, or 3-5 years of follow up between laparoscopic and open colposuspension groups. Laparoscopic colposuspension took longer time to perform (87 versus 42 minutes, P < 0.0001) but was associated with less blood loss (P= 0.03), less pain (P= 0.02), and quicker return to normal activities (P= 0.01). LBC has significant advantages over traditional OBC, without any apparent compromise in short-term and long-term outcomes.

Female↗

PubMed2006

Clinical and quality-of-life outcomes in women treated by the TVT-O procedure.

OBJECTIVES: To objectively assess the success rate at 6 months after tension-free vaginal tape obturator (TVT-O) procedure. To assess subjective success rates, complications, patient satisfaction, and quality of life (QOL). DESIGN: A prospective observational study. SETTING: A tertiary referral urogynaecology practice. POPULATION: A cohort of 100 consecutive women who underwent the TVT-O procedure between March and October 2004. METHODS: The TVT-O technique was performed as described. Three standardised QOL questionnaires were completed preoperatively at 6 months and 12 months. At 6 months, a urogenital history, visual analogue scale score (VAS) for patient satisfaction, uroflow, and urinary stress test were performed. After 12 months, a urogenital history and patient satisfaction verbal analogue score (VeAS) were obtained by telephone interview. MAIN OUTCOME MEASURE: Objective success rate of the TVT-O procedure was measured by negative stress test. Secondary outcomes were subjective success rates at 6 and 12 months, pre- and postoperative comparison of urodynamic parameters, complications, postoperative symptomatology, QOL analysis, and patient satisfaction. RESULTS: Mean follow up was 18.5 months. Objective success rate was 95%. Subjective success rates were 92 and 84% at 6 and 12 months. Complications included recurrent urinary tract infection (six), voiding difficulty (two), persistent groin discomfort (three), haematoma (one), wound infection (one), vaginal tape erosion (one), and urethral irritation (one). Prevalence of de novo urge incontinence was 4.1 and 4.8% at 6 and 12 months. QOL analysis showed significant improvements in QOL scores postoperatively. Visual and verbal analogue scores indicated high patient satisfaction (VAS, VeAS >or= 80%) in 77 and 67% at 6 and 12 months. CONCLUSION: The TVT-O is a safe and effective treatment for female stress urinary incontinence.

Female↗

PubMed2001

Probiotic bacteria enhance murine and human intestinal epithelial barrier function.

BACKGROUND & AIMS: The probiotic compound, VSL#3, is efficacious as maintenance therapy in pouchitis and ulcerative colitis. The aim of this study was to determine the efficacy of VSL#3 as a primary therapy in the treatment of colitis in the interleukin (IL)-10 gene-deficient mouse. Mechanisms of action of VSL#3 were investigated in T(84) monolayers. METHODS: IL-10 gene-deficient and control mice received 2.8 x 10(8) colony-forming units per day of VSL#3 for 4 weeks. Colons were removed and analyzed for cytokine production, epithelial barrier function, and inflammation. VSL#3 or conditioned media was applied directly to T(84) monolayers. RESULTS: Treatment of IL-10 gene-deficient mice with VSL#3 resulted in normalization of colonic physiologic function and barrier integrity in conjunction with a reduction in mucosal secretion of tumor necrosis factor alpha and interferon gamma and an improvement in histologic disease. In vitro studies showed that epithelial barrier function and resistance to Salmonella invasion could be enhanced by exposure to a proteinaceous soluble factor secreted by the bacteria found in the VSL#3 compound. CONCLUSIONS: Oral administration of VSL#3 was effective as primary therapy in IL-10 gene-deficient mice, and had a direct effect on epithelial barrier function.

Animals↗

PubMed1998

Combined analysis of studies of the effects of the matrix metalloproteinase inhibitor marimastat on serum tumor markers in advanced cancer: selection of a biologically active and tolerable dose for longer-term studies.

This combined analysis investigated the effect of marimastat, a specific inhibitor of matrix metalloproteinases, on markers of tumor progression measured in patients with advanced cancer. By defining the tolerability and biological activity of the drug, it aimed to establish an appropriate dose range for use in Phase III trials. Patients with advanced, serologically progressive ovarian, prostatic, pancreatic, and colorectal cancer were recruited into six nonrandomized, dose ranging, multicenter clinical trials in North America and Europe. The biological activity of marimastat was assessed by serial measurements of the serum tumor markers carcinoembryonic antigen, CA125, CA19-9, and prostate-specific antigen. Patients were recruited with tumor markers rising by more than 25% averaged over a 4-week screening period. A biological effect was defined as a level of tumor marker at the end of treatment no greater than at study entry; a partial biological effect was defined as a rise in the level of tumor marker over the treatment period of 0-25% per 4 weeks. Pharmacokinetic and safety data were collected and assessed as the studies progressed. All patients were followed up for survival.

Adult↗

PubMed1997

Haloalkanoate dehalogenase II (DehE) of a Rhizobium sp.--molecular analysis of the gene and formation of carbon monoxide from trihaloacetate by the enzyme.

A 3-kb EcoRI fragment of genomic DNA from a Rhizobium sp. cloned into pUC19 endowed Escherichia coli K-12 with the ability to grow, albeit slowly, with 2-chloropropionic acid as substrate. The construct expressed weakly a gene that encoded a non-stereospecific 2-chloropropionic acid dehalogenase (dehalogenase II; DehE). The dehE gene was not closely linked to the organism's other two dehalogenase genes, dehD and dehL. The derived amino acid sequence of DehE showed little identity with DehD or DehL, but there was significant identity to two other dehalogenases that act non-selectively on 2-chloropropionic acid. The fragment carried a truncated ORF upstream of dehE that was 51% identical to a positively acting regulatory protein, DehR, required for expression of a Pseudomonas putida dehalogenase gene. In its complete form this gene could encode the Rhizobium sp. dehalogenase-regulatory protein. DehE dehalogenated tribromoacetic acid completely, forming stoichiometric amounts of carbon monoxide and carbon dioxide as the other products.

Acetates↗

PubMed1996

Cloning, sequencing and expression in Escherichia coli of two Rhizobium sp. genes encoding haloalkanoate dehalogenases of opposite stereospecificity.

A 6.5-kp EcoRI fragment of genomic DNA from a Rhizobium sp. cloned into pUC19 was able to endow Escherichia coli K-12 with the novel ability to grow at the expense of 2-chloropropionic acid. Subcloning showed that this property was a consequence of two dehalogenases encoded on a 2.2-kb PstI fragment. Further subcloning of the PstI fragment led to two constructs that encoded, separately, dehalogenase activity that acted stereospecifically on D-2-chloropropionic acid and L-2-cloropropionic acid, respectively. The genes encoding these two stereospecific dehalogenases have been sequenced and shown to be separated by 177 bp of non-coding DNA. Expression of the dehalogenase genes involved the vector promoter, suggesting that the anticipated Rhizobium sp. regulatory sequences were not functional in E. coli. Comparison of the deduced amino acid sequences of the two dehalogenases (18% identity) indicated with any other 2-chloropropionic acid dehalogenase studied so far.

Amino Acid Sequence↗

PubMed1993

Growth of Azotobacter vinelandii UWD in Fish Peptone Medium and Simplified Extraction of Poly-beta-Hydroxybutyrate.

Azotobacter vinelandii UWD was grown in a fermentor with glucose medium with and without 0.1% fish peptone (FP) in batch and fed-batch cultures for the production of the natural bioplastic poly-beta-hydroxybutyrate (PHB). Strain UWD formed PHB five times faster than cell protein during growth in glucose and NH(4), but PHB synthesis stopped when NH(4) was depleted and nitrogen fixation started. When FP was added to the same medium, PHB accumulated 16 times faster than cell protein, which in turn was inhibited by 40%, and PHB synthesis was unaffected by NH(4) depletion. Thus, FP appeared to be used as a nitrogen source by these nitrogen-fixing cells, which permitted enhanced PHB synthesis, but it was not a general growth stimulator. The addition of FP to the medium led to the production of large, pleomorphic, osmotically sensitive cells that demonstrated impaired growth and partial lysis, with the leakage of DNA into the culture fluid, but these cells were still able to synthesize PHB at elevated rates and efficiency. When FP was continuously present in fed-batch culture, the yield in grams of polymer per gram of glucose consumed was calculated to range from 0.43 g/g, characteristic of nongrowing cells, to an unprecedented 0.65 g/g. Separation of an FP-free growth phase from an FP-containing growth phase in fed-batch culture resulted in better growth of these pleomorphic cells and good production of PHB (yield, 0.32 g/g). The fragility of these cells was exploited in a simple procedure for the extraction of high-molecular-weight PHB. The cells were treated with 1 N aqueous NH(3) (pH 11.4) at 45 degrees C for 10 min. This treatment removed about 10% of the non-PHB mass from the pellet, of which 60 to 77% was protein. The final product consisted of 94% PHB, 2% protein, and 4% nonprotein residual mass. The polymer molecular weight (1.7 x 10 to 2.0 x 10) and dispersity (1.0 to 1.9) were not significantly affected (P = 0.05) by this treatment. In addition, the NH(3) extraction waste could be recycled in the fermentation as a nitrogen source, but it did not promote PHB production like FP. A scheme for improved downstream extraction of PHB as well as the merits of using pleomorphic cells in the production of bioplastics is discussed.

Journal Article↗

PubMed1991

Purification and properties of extracellular lipase from Pseudomonas aeruginosa EF2.

Extracellular lipase was purified from a Tween 80-limited continuous culture of Pseudomonas aeruginosa EF2 by ultrafiltration of the culture supernatant followed by anion-exchange and gel-filtration FPLC. The lipase was composed of a single subunit (Mr 29,000, pI 4.9), which was capable of a variable degree of aggregation, and which exhibited both lipase activity, measured with the insoluble substrate olive oil (predominantly triolein), and esterase activity, measured with the soluble substrates p-nitrophenyl acetate and Tween 80. Lipase activity was approximately eight times higher than either type of esterase activity (kcat approximately 3000 s-1 for the hydrolysis of olive oil). The enzyme showed a marked regiospecificity for the 1,3-oleyl residues of radiolabelled triolein, was relatively stable at moderate temperatures (exhibiting a biphasic loss of activity with an initial t1/2 of 17.5 min at 60 degrees C) and was very stable to freezing and thawing. Lipase activity was only weakly inhibited by the serine-active reagent 3,4-dichloroisocoumarin, and was not inhibited by the chelating agent EDTA (1 mM). The N-terminal amino acid sequence of the Ps. aeruginosa EF2 lipase showed a marked similarity to those of several other bacterial lipases.

Amino Acid Sequence↗

PubMed1990

Binding-protein-dependent lactose transport in Agrobacterium radiobacter.

Agrobacterium radiobacter NCIB 11883 was grown in lactose-limited continuous culture at a dilution rate of 0.045/h. Washed cells transported [14C]lactose and [methyl-14C]beta-D-thiogalactoside, a nonmetabolisable analog of lactose, at similar rates and with similar affinities (Km for transport, less than 1 microM). Transport was inhibited to various extents by the uncoupling agent carbonyl cyanide p-trifluoromethoxyphenylhydrazone, by unlabeled beta-galactosides and D-galactose, and by osmotic shock. The accumulation ratio for methyl-beta-D-thiogalactoside was greater than or equal to 4,100. An abundant protein (molecular weight, 41,000) was purified from osmotic-shock fluid and shown by equilibrium dialysis to bind lactose and methyl-beta-D-thiogalactoside, the former with very high affinity (binding constant, 0.14 microM). The N-terminal amino acid sequence of this lactose-binding protein exhibited some homology with several other sugar-binding proteins from bacteria. Antiserum raised against the lactose-binding protein did not cross-react with two glucose-binding proteins from A. radiobacter or with extracts of other bacteria grown under lactose limitation. Lactose transport and beta-galactosidase were induced in batch cultures by lactose, melibiose [O-alpha-D-galactoside-(1----6)alpha-D-glucose], and isopropyl-beta-D-thiogalactoside and were subject to catabolite repression by glucose, galactose, and succinate which was not alleviated by cyclic AMP. We conclude that lactose is transported into A. radiobacter via a binding protein-dependent active transport system (in contrast to the H+ symport and phosphotransferase systems found in other bacteria) and that the expression of this transport system is closely linked to that of beta-galactosidase.

Amino Acid Sequence↗

PubMed1989

Binding-protein-dependent sugar transport by Agrobacterium radiobacter and A. tumefaciens grown in continuous culture.

Binding-protein-dependent sugar transport has been investigated in Agrobacterium radiobacter and A. tumefaciens. A. radiobacter contained two high-affinity glucose-binding proteins (GBP1 and GBP2) that additionally bound D-galactose (KD 0.26 microM) and D-xylose (KD 0.04 microM) respectively and were involved in the transport of these sugars. Partial sequencing of GBP1 and GBP2 showed that GBP2 exhibited significant homology with both the arabinose-binding protein (ABP) and the galactose-binding protein (GalBP) from Escherichia coli, whereas GBP1 exhibited significant homology only with ABP. Antiserum raised against GBP1 cross-reacted with GBP1 but not with GBP2, and vice versa. Anti-GBP1 and anti-GBP2 also cross-reacted with proteins corresponding to GBP1 and GBP2 respectively in A. tumefaciens, but little or no cross-reaction was observed with selected members of the Enterobacteriaceae, Rhizobiaceae and Pseudomonadaceae families grown under glucose limitation. GBP1 was less strongly repressed than GBP2 following batch growth of A. radiobacter on various carbon sources. The growth of A. radiobacter for more than approximately 10 generations in continuous culture under galactose or xylose limitation (D 0.045 h-1) led to the emergence of new strains which exhibited increased rates of glucose/galactose or glucose/xylose uptake, and which respectively hyperproduced GBP1 (strain AR18a) or GBP2 (strain AR9a). Similarly, growth of A. tumefaciens for more than approximately 15 generations under glucose or galactose limitation produced new strains which exhibited increased rates of glucose/xylose or glucose/galactose uptake and which respectively hyperproduced proteins analogous to GBP2 (strain AT9) or GBP1 (strain AT18a). It is concluded that growth of Agrobacterium species under carbon-limited conditions leads to the predictable emergence of new strains which specifically hyperproduce the transport system for the limiting nutrient. The GBP1-dependent system of A. radiobacter is unique amongst these transport systems in that the mutations that lead to its hyperproduction under carbon limitation render it least susceptible to repression by excess glucose during ammonia limitation, with the result that succinoglucan exopolysaccharide is produced from glucose at an enhanced rate.

Bacterial Proteins↗

PubMed1989

Ocular toxicity of desferrioxamine--an example of copper promoted auto-oxidative damage?

Three patients with rheumatoid disease were given the 'iron chelating' drug desferrioxamine (DFX), which also has an appreciable affinity for copper. The drug was injected cautiously, in lower doses than in patients with thalassaemia, and intramuscularly to evaluate its anti-inflammatory effects. Two of the three patients developed ocular abnormalities. One patient, who also received methyldopa, developed severe but reversible visual failure associated with an abnormal electro-oculogram (EOG); another showed reversible depression of the EOG. Analysis of the cerebrospinal fluid (CSF) of this patient showed an increase in phenanthroline detectable (non-caeruloplasmin-bound) copper. Analysis of the CSF of the third patient, who did not develop any clinical or electrophysiological ocular abnormalities, was normal. Haematological assessments indicated that all three patients probably had reduced iron stores. With in-vitro systems DFX was shown to mobilise copper from albumin and to facilitate copper movement across a cell membrane model, a property that was enhanced by methyldopa. Our observations are consistent with the concept that in rheumatoid patients low iron stores may result in binding of copper by DFX and that this may be of central importance in causing the ocular toxicity of DFX.

Aged↗

PubMed1988

Binding-protein-dependent glucose transport by Agrobacterium radiobacter grown in glucose-limited continuous culture.

Agrobacterium radiobacter NCIB 11883 was grown in glucose-limited continuous culture at low dilution rate. Whole cells transported glucose using an energy-dependent mechanism which exhibited an accumulation ratio greater than 2000. Three major periplasmic proteins were purified and their potential role as glucose-binding proteins (GBP) were investigated using equilibrium dialysis. Two of these, GBP1 (Mr 36,500) and GBP2 (Mr 33,500), bound D-glucose with high affinity (KD 0.23 and 0.07 microM respectively), whereas the third protein (Mr 30,500) showed no binding ability. Competition experiments using various analogues showed that those which differed from glucose at C-6 (e.g. 6-chloro-6-deoxy-D-glucose and 6-deoxy-D-glucose) variably decreased the binding of glucose to both GBP1 and GBP2, whereas those which differed at C-4 (e.g. D-galactose) were only effective with GBP1. The rate of glucose uptake and the concentration of the glucose-binding proteins increased in parallel during prolonged growth under glucose-limitation due to the emergence of new strains in which GBP1 (e.g. strain AR18) or GBP2 (e.g. strain AR9), but not both, was hyperproduced and accounted for at least 27% of the total cell protein. It is concluded that A. radiobacter synthesizes two distinct periplasmic binding proteins which are involved in glucose transport, and that these proteins are maximally derepressed during growth under glucose limitation.

Biological Transport↗

PubMed1988

The relationship between glucose transport and the production of succinoglucan exopolysaccharide by Agrobacterium radiobacter.

Agrobacterium radiobacter NCIB 11883 was grown in ammonia-limited continuous culture at low dilution rate with glucose as the carbon source. Under these conditions the organism produced an extracellular succinoglucan polysaccharide and transported glucose using the same periplasmic glucose-binding proteins (GBP1 and GBP2) as during glucose-limited growth. Transition from glucose- to ammonia-limited growth was accompanied by a very rapid decrease in glucose uptake capacity, whereas the glucose-binding proteins were diluted out much more slowly (t1/2 approximately 1 h and 14 h respectively). Although the rate of glucose uptake and the concentrations of GBP1 and GBP2 were much lower during ammonia limitation, the activities of enzymes involved in the early stages of glucose metabolism and in the production of succinoglucan precursors were essentially unchanged. Glucose transport was also investigated in two new strains of A. radiobacter which had been isolated following prolonged growth under glucose limitation. Glucose uptake by strain AR18 was significantly less repressed during ammonia limitation compared with either the original parent strain or strain AR9, and this was reflected both in its relatively high concentration of GBP1 and in its significantly higher rate of succinoglucan synthesis. Flux control analysis using 6-chloro-6-deoxy-D-glucose as an inhibitor of glucose transport showed that the latter was a major kinetic control point for succinoglucan production. It is concluded that glucose uptake by A. radiobacter, particularly via the GBP1-dependent system, is only moderately repressed during ammonia-limited growth and that the organism avoids the potentially deleterious effects of accumulating excess glucose by converting the surplus into succinoglucan.

Ammonia↗

PubMed1987

Purification, crystallisation and preliminary X-ray diffraction characterisation of methanol dehydrogenase from Methylosinus trichosporium OB3b.

Methanol dehydrogenase was purified from the obligate methanotroph, Methylosinus trichosporium OB3b, in two steps from disrupted biomass by aqueous two-phase partition and ion-exchange chromatography. Copartitioning of a cytochrome c was dependent upon the pH at which aqueous partition was carried out. The native enzyme has a Mr of 120,000, as determined by gel filtration chromatography, and consists of two identical subunits. The purified enzyme contained four electrophoretically distinct isoenzymes, with pI values of 6.3, 6.58, 6.63 and 6.88. The native enzyme has been crystallised in a form suitable for high-resolution X-ray crystallographic studies. The crystals diffract to better than 0.19 nm spacing and are relatively stable to irradiation with X-rays. The space group is P6(1)22 (or P6(5)22) with cell dimensions a = b = 10.21 nm, c = 29.32 nm and the crystal probably contains a single monomer in the asymmetric unit.

Alcohol Oxidoreductases↗

PubMed1985

Incorporation of fluorotryptophan into triostin antibiotics by Streptomyces triostinicus.

The quinoxaline chromophores of the antibiotics produced by Streptomyces triostinicus are derived from tryptophan. Protoplasts of this organism made novel products when they were incubated with DL-5-fluorotryptophan or DL-6-fluorotryptophan. When added to batch cultures of the organism, DL-5-fluorotryptophan, at concentrations as low as 10 microM, inhibited both mycelial growth and triostin production, but gave rise to novel products. These have been characterized, using fast atom bombardment mass spectrometry, as novel triostins in which one or both of the quinoxaline rings contain an atom of fluorine. The chromatographic properties of the triostins arising from the incorporation of DL-5-fluorotryptophan are very similar to those of triostins containing chlorine or bromine at position 6 of the quinoxaline ring; they are clearly different from those having a chlorine atom at position 7. Accordingly, it is suggested that the carbon atom at position 5 of the indole ring of tryptophan ends up at position 6 of the quinoxaline ring system in triostins A and C.

Anti-Bacterial Agents↗

PubMed1985

Cerebral and ocular toxicity induced by desferrioxamine.

Seven patients with rheumatoid disease were given the iron-chelating drug desferrioxamine (DFX) to evaluate its possible anti-inflammatory effects. Two of these patients, who also received the anti-emetic prochlorperazine, lost consciousness for 48-72 h and then fully recovered. Electroencephalography showed abnormalities of the type associated with metabolic disturbance. One of these patients showed pyramidal features and subsequently developed an optic neuropathy and pigmentary retinopathy. Analysis of his cerebrospinal fluid showed a decrease in loosely-bound (catalytic) iron and increase in loosely-bound (catalytic) copper, total iron and products of lipid peroxidation, with values approaching normal as the symptoms resolved. Subsequent in vivo/vitro studies clearly demonstrated that the neurological effects were due to a synergistic action of desferrioxamine and prochlorperazine, probably resulting in exceptional fluxes of intra/extra cellular iron/copper disturbing noradrenergic and serotonergic systems. Two other patients who did not receive prochlorperazine, developed retinal problems which later improved, one after only 15 g of desferrioxamine. Our observations suggest a new model for metabolic encephalopathy studies and provide insight into the mechanisms of pigmentary retinopathy.

Adult↗

PubMed1983

The use of radiolabelled triostin antibiotics to measure low levels of binding to deoxyribonucleic acid.

Triostin antibiotics, which contain a cyclic peptide with a disulphide bridge, have been prepared by growing Streptomyces triostinicus in the presence of inorganic [35S]-sulphate. The labelled triostin A has been shown to behave in all respects similarly to the authentic natural product and to enable a much more sensitive radiochemical adaptation of the solvent-partition method for determining antibiotic binding to DNA. By this means, binding isotherms at low, biologically relevant levels (down to one antibiotic molecule per gene) have been measured. The results indicate the existence of some tight binding sites in natural DNA species that are preferentially occupied at low concentrations. No evidence has been found for any allosteric transitions provoked by interaction between these antibiotics and natural DNA species, though there is evidence for co-operativity in the binding of triostin A to poly(dA-dT). For the first time accurate isotherms have been determined for the binding of triostin C to DNA; its binding constants for a variety of polydeoxynucleotides are uniformly tighter than those of triostin A but fall into the same ranking order when different species of natural DNA are compared.

Animals↗

PubMed1983

Preparation and DNA-binding properties of substituted triostin antibiotics.

Novel derivatives of the triostin group of antibiotics were prepared by supplementing cultures of the producing organism Streptomyces triostinicus with a variety of aromatic carboxylic acids. Five new antibiotics, each having both the natural quinoxaline chromophores replaced by a substituted ring system, were purified to homogeneity and characterized by high-pressure liquid chromatography and nuclear magnetic resonance. Their antibacterial activities and DNA-binding properties were investigated. Addition of a halogen atom at position 6 of the quinoxaline ring or an amino group at position 3 had little effect on either the biological activity or the DNA-binding characteristics. The bis-3-amino derivative is fluorescent, and its fluorescence is strongly quenched by calf thymus DNA and polydeoxyguanylate-polydeoxycytidylate but not by polydeoxyadenylate-polydeoxythymidylate, suggesting that it binds preferentially to guanosine-cytosine-rich sequences in natural DNA. Binding constants for the bis-6-chloro and bis-3-amino derivatives do not differ greatly from those of unsubstituted triostin A. The analogs having two quinoline chromophores or a chlorine atom in position 7 of the quinoxaline ring display little or no detectable antibacterial activity, in marked contrast to the other congeners. Bis-7-chloro-triostin A binds conspicuously more tightly to polydeoxyadenylate-polydeoxythymidylate than to any other polynucleotide tested.

Anti-Bacterial Agents↗