The structure of vacidin A, an aromatic heptaene macrolide antibiotic. I. Complete assignment of the 1H NMR spectrum and geometry of the polyene chromophore.

The constitution of vacidin A, a representative of the aromatic heptaene macrolide antibiotics was established on the basis of 13C and 1H-1H double quantum filtered correlated spectroscopy, rotating frame nuclear Overhauser effect spectroscopy, J-resolved 1H as well as 1H-13C correlation NMR spectra. Geometry of the polyene chromophore was determined as 22E,24E,26E,28Z,30Z,32E,34E.

The structure of vacidin A, an aromatic heptaene macrolide antibiotic. II. Stereochemistry of the antibiotic.

On the basis of coupling constants and rotating frame nuclear Overhauser effect spectroscopy of vacidin A methoxycarbonylmethylamide, the stereochemistry of the antibiotic was established. The configuration of the aglycone was determined as (3R,7R,9R,11S,13S,15R,17S,18R,19S,21R, 36S,37R,38S). The aminosugar constituent of the antibiotic was identified as beta-(D)-mycosamine. The chiral center at C-41 remains to be assigned.

Bending of oligonucleotides containing an isosteric nucleobase: 7-deaza-2'-deoxyadenosine replacing dA within d(A)6 tracts.

Decanucleotide duplexes of the parent sequence d(GGCA6C).d(CCGT6G) containing various numbers of 2'-deoxytubercidin (c7Ad) in place of 2'-deoxyadenosine have been synthesized. Phosphoramidites of protected c7Ad (3a,b) were used in automated solid-phase synthesis together with those of regular nucleosides. Upon enzymic 5'-phosphorylation and ligation, multimers of 5 and 7-11 were analyzed by polyacrylamide gel electrophoresis and compared with regard to intrinsic, sequence-directed bending. Replacement of dA by c7Ad within the oligomers decreased bending, but the extent depends strongly on the position of incorporation: strong bending was still observed if the 3'- and 5'-terminal dA residues of the dA tract were replaced while the interruption of the d(A)6 tract by c7Ad reduced bending strongly.

Comparative study of protein synthesis and heat-shock puffing activity in Drosophila salivary glands treated with chloramphenicol.

The effects of chloramphenicol (CAP) on puffing activity and incorporation of tritiated amino acids in proteins synthesized by cultured larval salivary glands of Drosophila melanogaster were examined. CAP concentrations exceeding 1 mM were found to inhibit cellular protein synthesis and to induce the special group of heat-shock puffs in the polytene chromosomes. Recovery from a transient treatment with 5 mM CAP for 120 min led to rapid regression of the puffs and resumption of protein synthesis giving a pattern of labelled polypeptides similar to that produced by cells submitted to a temperature shift from 25 to 37 degrees C. Only slight inhibition of protein synthesis was found with thiamphenicol, the methylsulphonyl analogue of CAP, which induced a single puff in the 93D region, but did not alter the pattern of polypeptides. In contrast to the results obtained with CAP, recovery from a transient inhibition of protein synthesis by cycloheximide led to the synthesis of normal proteins as produced by control cells at 25 degrees C. Different effects of CAP which may interfere with protein synthesis and puffing activity are discussed.

[Phase separation in dipalmitoyl phosphatidylcholine bilayers induced by ionophores and binary electrolytes]. / Razdelenie faz v dipal'mitoilfosfatidilkholine v prisutstvii ionoforov i binarnykh élektrolitov.

Thermotropic behavior of unsonicated aqueous dispersion of dipalmitoyl phosphatidylcholine (DPPC) has been studied by scanning microcalorimetry and fluorescent probe method. Phase separation in the lipid bilayers was observed for systems containing ionophores (valinomycin, dinactin) and 1 : 1 electrolytes (NaCl, KCl, RbCl, CsCl). The ratio of lipid phases coexisting in the systems appeared to be dependent on the concentration of the electrolytes. Changes in the thermotropic properties of the lipid phase induced by valinomycin were observed when K+ and Rb+ ions-forming complexes with the ionophore were present in the systems. The latter phenomenon was not found for the systems containing dinactin possessing a lower ability for complex formation with the cations.

Kinetics of carrier-mediated ion transport in two new types of solvent-free lipid bilayers.

In contrast with the usual glyceryl-monooleate/decane (GMO-D) bilayer lipid membranes, new membranes, formed from a mixture of GMO in squalene (GMO-S) or from a mixture of GMO in triolein (GMO-T), seem to be almost solvent free. Our results from voltage-jump relaxation studies, using these "solvent-free" membranes with the homologue carriers, nonactin, monactin, dinactin, trinactin, and tetranactin, are compared with the corresponding ones for GMO-D membranes. With all homologues, solvent-free membranes show an increase of the free carrier translocation rate, ks, by a factor of 2.5, a decrease in the dissociation rate constant of the complex, kDi, by a factor of 1.5 and no significant change in its formation rate constant, kRi. However, the principal effect of the absence of solvent in these membranes is an increase by a factor of approximately 10 of the translocation rate constant for moving the complex across the membrane, kis. This increase varies regularly from a factor of 7-15 with decreasing carrier size, and is always larger for GMO-T than for GMO-S membranes. These solvent-free effects are interpreted in terms of modifications of electrostatic and hydrophobic energy profiles in the membrane.

Effects of variation of ion and methylation of carrier on the rate constants of macrotetralide-mediated ion transport in lipid bilayers.

The effects of methylation on the rate constants of carrier-mediated ion transport have been studied on monooleindecane bilayers with K+, Rb+, NH4+, and Tl+ ions, using the series of homologue carriers, nonactin, monactin, dinactin, trinactin, and tetranactin, each member of the series differing from the previous one by only one methyl group. Measurements of the amplitude and time constant of the current relaxation after a voltage jump over a large domain of voltage and permeant ion concentration, together with a computer curve-fitting procedure, have allowed us, without the help of steady-state current-voltage data, to deduce and compare the values of the various rate constants for ion transport: formation (kRi) and dissociation (kDi) of the ion-carrier complex at the interface, translocation across the membrane interior of the carrier (ks) and the complex (kis). With the additional information from steady-state low-voltage conductance measurements, we have obtained the value of the aqueous phase-membrane and torus-membrane partition coefficient of the carrier (gammas and gammas). From nonactin to tetranactin with the NH4+ ion, kis, and gammas are found to increase by factors of 5 and 3, respectively, kDi and gammas to decrease respectively by factors 8 and 2, while kRi and ks are practically invariant. Nearly identical results are found for K+, Rb+, and Tl+ ions. kRi, ks and kis are quite invariant from one ion to the other except for Tl+ were kRi is about five times larger. On the other hand, kDi depends strongly on the ion, indicating that dissociation is the determining step of the ionic selectivity of a given carrier. The systematic variations in the values of the rate constants with increasing methylation are interpreted in terms of modification of energy barriers induced by the carrier increasing size. Within this framework, we have been able to establish and verify a fundamental relationship between the variations of kis and kDi with methylation.

In vitro activity of BU-2313B against anaerobic bacteria.

The antimicrobial efficacy of BU-2313B, a new antibiotic, was evaluated in comparison with clindamycin, chloramphenicol and cefoxitin against 265 clinical anaerobic isolates. BU-2313B inhibited 88% of 66 isolates of Bacteroides fragilis tested at 2 micrograms/ml, whereas clindamycin, chloramphenicol and cefoxitin inhibited 98, 97 and 92% of them at 2, 8 and 16 micrograms/ml, respectively. BU-2313B was severalfold more effective than chloramphenicol and cefoxitin, but it was eight times less effective than clindamycin.

Taxonomy of the antibiotic Bu-2313-producing organism. Microtetraspora caesia sp. nov.

An aerobic actinomycete strain isolated from an Indian soil sample and designated No. E864-61 was found to produce in submerged fermentation a new antibiotic complex, Bu-2313 (components A and B). Strain E864-61 forms single, pairs or chains of three to eight spores on the aerial mycelium and its aerial mass color is grayish blue-green. The cell wall of strain E864-61 contains meso-diaminopimelic acid and galactose. Strain E864-61 has been classified as a new species of the genus Microtetraspora and designated as Microtetraspora caesia sp. nov.

C NMR spectra of streptolydigin, tirandamycin, and related degradation products.

Absorptions of the 32 carbon atoms of streptolydigin, a 3-acyltetramic acid, have been assigned in its C NMR spectrum, as have the adsorptions of triandamycin and related degradation products. Methods employed in assigning the individual carbons include off-resonance decoupling, and comparison studies with appropriate model compounds.

Bu-2313, a new antibiotic complex active against anaerobes. I. Production, isolation and properties of Bu-2313 A and B.

An unidentified oligosporic actinomycete strain, No. E864-61, produced two new antibiotics, Bu-2313 A (C27H35NO9) and Bu-2313 B (C26H33NO9). Bu-2313 A and B each exhibited a broad antibiotic spectrum against Gram-positive and Gram-negative anaerobic bacteria, and showed in vivo activity against experimental infections produced by B. fragilis and C. perfringens. Bu-2313 also inhibited some aerobic bacteria such as streptococci. Bu-2313 B was approximately two-fold more active than Bu-2313 A.

Bu-2313, a new antibiotic complex active against anaerobes. II. Structure determination of Bu-2313 A and B.

The structures of Bu-2313 A and B have been determined. They are dienoyltetramic acid-containing antibiotics structurally related to streptolydigin and tirandamycin.

Bu-2313, a new antibiotic complex active against anaerobes. III. Semi-synthesis of Bu-2313 A and B, and their analogs.

Analogs of Bu-2313 A and B were prepared by C-acylation of tetramic acid derivatives with the dienoic acid moiety obtained by periodate oxidation of Bu-2313 A or B. The C-acylation proceeded in the presence of a strong base such as potassium t-butoxide, sodium hydride or lithium hydride, whereas the use of triethylamine afforded O-acylated products. The semi-synthetic Bu-2313 analogs exhibited antibacterial spectra similar to the parent antibiotic but none exceeded Bu-2313 B in activity.

Studies on new phosphonic acid antibiotics. IV. Structure determination of FR-33289, FR-31564 and FR-32863.

The structure of novel phosphonic acid antibiotics FR-33289, FR-31564, and FR-32863, produced by strains of Streptomyces, have been established as I, II, and III, respectively, on the basis of spectroscopic and chemical evidences.

Modifications of a macrolide antibiotic midecamycin. II. Reaction of midecamycin and 9-acetylmidecamycin with dimethylsulfoxide and acetic anhydride.

Treatment of 9,2'-diacetylmidecamycin (2) with DMSO and acetic anhydride afforded 3''-methylthiomethyl derivative (3) preferably in the presence of pyridine. Reaction of midecamycin (1) with DMSO and acetic anhydride gave 2'-acetyl-9-dehydro-3''-methylthiomethyl derivative (9) indicating that the three hydroxyl groups reacted in a different way to the reagent. When compound 2 was reacted with DMSO and acetic anhydride in the presence of CCl4, 3''-acetoxymethyl derivative (13) was a major product, which was formed via 3 through the Pummerer rearrangement. The structures of 3, 9 and 13 were confirmed by examining NMR and mass spectra of these compounds and their deuterio analogue. They showed antimicrobial spectra similar to 1 but superior in vivo activity.