FTMS structure elucidation of natural products: application to muraymycin antibiotics using ESI multi-CHEF SORI-CID FTMS(n), the top-down/bottom-up approach, and HPLC ESI capillary-skimmer CID FTMS.

The molecular formulas for the structures and substructures of muraymycin antibiotics A1 (C52H90N14O19, MW 1214) and B1 (C49H83N11O18, MW 1113) were determined using electrospray ionization (ESI) Fourier transform mass spectrometry (FTMS). The muraymycin A1 and B1 structures were elucidated by utilizing capillary-skimmer fragmentation with up to five stages of mass spectrometry (MS5). Multi-CHEF, a multiple ion isolation method, was used at each stage of MS(n) to isolate a parent ion and up to four reference ions, for exact-mass calibration. The parent ions were fragmented by SORI-CID and the product ions internally calibrated with average absolute mass errors less than 1 ppm at each stage in the fragmentation processes. Using the top-down/bottom-up approach, the molecular formulas for the antibiotics were determined by summing the elemental formulas of the neutral losses, obtained by measuring the mass differences (<500 Da) between the genetically related sequential parent ion masses in the MS(n) spectra, with the unique elemental formula of the lowest parent ion mass (<500 Da). The structures of 12 additional compounds in the muraymycin complex were elucidated using HPLC ESI capillary-skimmer CID FTMS by correlating their fragmentation patterns with those of muraymycins A1 and B1. Sequential neutral losses of an aminosugar, a valine, a uridine, and an ester fatty acid from the muraymycin parent ions provided diagnostic fragments for characterization.

Muraymycins, novel peptidoglycan biosynthesis inhibitors: synthesis and SAR of their analogues.

A series of Muraymycin analogues was synthesized. These analogues showed excellent antimicrobial activity against gram-positive organisms. These analogues also showed excellent inhibitory activity against the target peptidoglycan biosynthesis enzyme MraY, the cell membrane associated transglycosylase responsible for the formation of Lipid II.

Use of bis-(chiral alpha-methylbenzyl)glycine esters for synthesis of enantiopure beta-hydroxyamino esters.

[reaction: see text] Aldol reactions using bis-(chiral alpha-methylbenzyl)glycine esters with aldehydes gave excellent diastereoselectivity. Thus, an enantiopure ribosylglycine was prepared for the synthesis of analogues of the natural antibiotics muraymycin. This method was extended for formation of beta-hydroxyamino esters.

Muraymycins, novel peptidoglycan biosynthesis inhibitors: semisynthesis and SAR of their derivatives.

Sixteen muraymycin derivatives 2-17 were synthesized based on selective reactions of the primary and secondary amino groups of muraymycin C1 (1) with isocyanates and aldehydes. Disubstituted derivatives 3-9 demonstrated no activity against either MraY or MurG at

[The effect of bacterial and synthetic peptidoglycans on the toxicity of a cell-free pertussis preparation]. / Vliianie bakterial'nykh i sinteticheskikh peptidoglikanov na toksichnost' beskletochnogo kokliushnogo preparata.

The influence of bacterial and synthetic peptidoglycans on the toxicity of acellular pertussis preparations (APP) has been studied in the mouse weight gain test and in the endotoxic shock development test on mice treated with Actinomycin D. The data obtained in these tests indicate that the immunomodulators (IM) under study are capable of changing (increasing or decreasing, depending on the dose) the toxic properties of APP. The antitoxic action of IM, established in this study, depends on the combination of the doses of IM and APP and the time elapsed from the time of immunization. The possibility of using these IM in a dose of 0.0001 microgram for reducing the LD50 of APP has been established. The use of IM belonging to the group of bacterial synthetic peptidoglycans for the development of acellular pertussis vaccines with reduced reactogenicity has been shown to hold much promise.

Blood-platelets-damaging activity of some synthetic Streptococcus peptidoglycan subunits and analogues.

A series of 25 synthetic subunits or analogues of streptococcal peptidoglycan was tested for their ability to damage rabbit blood platelets. The morphological changes of the platelets were studied on an ultrastructural level. Minimal subunit structure able to produce a complete lysis of the platelets was found to be muramyldipeptide (MDP). Comparable lysis of platelets was also caused by muramyltetrapeptide and MDP containing D-Ala instead of L-Ala. The lytic effect was dose-dependent and was exhibited rather after high doses of the substances used (up to 500 micrograms/ml). For the lytic reaction, the configuration of C3 and C4 in the muramyl residue of MDP was essential. Many substances produced only degranulation without lysis of the platelets and some of them did not influence the platelet ultrastructure at all. The paper presents some structure-to-function relationships of the compounds and shows that the platelet-damaging activity of peptidoglycan may be related to certain portions of the peptidoglycan molecule. This activity should be tested when the immunomodulatory substances derived from the bacterial peptidoglycan are searched for.

Arthritis-inducing ability of a synthetic adjuvant, N-acetylmuramyl peptides, and bacterial disaccharide peptides related to different oil vehicles and their composition.

A synthetic adjuvant, N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP), failed to produce polyarthritis with a wide dose range in a water-in-oil emulsion of mineral oil such as liquid paraffin, Drakeol, or heavy mineral oil. MDP, however, produced moderate to severe arthritis with almost 100% incidence in a water-in-oil emulsion made up of Difco incomplete adjuvant, which consists of Bavol F as an oil vehicle and Arlacel A as an emulsifier. N-acetylmuramyl-L-alanyl-L-isoglutamine did not produce arthritis, whereas 4,6-diacetyl-MDP produced the disease. Bacterial peptidoglycans, such as disaccharide peptides which were N-acetylglucosaminyl-N-acetylmuramyl-L-alanyl-D-isoglutaminyl-meso-diaminopimelyl-D-alanine and N-acetylglucosaminyl-6,o-acetyl-N-acetylmuramyl-L-alanyl-D-isoglutaminyl-meso-diaminopimelyl-D-alanine, also produced polyarthritis with low incidence in Difco oil but not in the other mineral oils described above. MDP and bacterial disaccharide peptides were able to produce the disease even in the latter mineral oil only when the concentration of Arlacel A was increased from 15% to 20 to 30% in the oil. We concluded that one of the minimal essential structures responsible for development of this disease is MDP, although the role of the oil vehicle remained uncertain, and there is no direct correlation between granulona formation and arthritogenicity of MDP.

Low-molecular-weight substrate for the lysozyme of T4 bacteriophage.

It has been shown that muropeptide CB, the chemically defined product of Escherichia coli B murein digestion by phage lambda endolysin, is the substrate for T4 lysozyme. This is the tetrasaccharide GlcNAc-MurNAc-GlcNAc-anMurNAc in which the carboxyl groups of MurNAc and anMurNAc residues are substituted by tetrapeptide LAla-DGlu-msA2pm-DAla (MurNAc = N-acetylmuramic acid, GlcNAc = N-acetyl-D-glucosamine, anMurNAc = 1,6-anhydro-N-acetylmuramic acid, LAla = L-alanine, DGlu = D-glutamic acid, msA2pm = meso-diaminopimelic acid). The substrate contains one bond hydrolysable by T4 lysozyme. The products of hydrolysis are the easily identifiable disaccharide muropeptides C6 (GlcNAc-MurNAc-LAla-DGlu-msA2pm-DAla) and CA (GlcNAc-anMurNac-LAla-DGlu-msA2pm-DAla). Thus the substrate may be used for the specific identification of murein N-acetylmuramoylhydrolases of the T4 lysozyme type, as well as for any quantitative measurement of the enzymatic reaction.

The action of lysozyme on peptidoglycan with N-unsubstituted glucosamine residues. Isolation of glycan fragments and their susceptibility to lysozyme.

1. A peptidoglycan preparation N-acetylated at about 30% of glucosamine residues was obtained by the treatment of the lysozyme-resistant cell wall paptidoglycan of Bacillus cereus with acetic anhydride at pH 7. Fractionation of dialyzable material resulting from lysozyme digestion of the glycan component of this peptidoglycan preparation yielded five oligosaccharides designated as S1 to S5 besides the disaccharide GlcNAc-MurAc. 2. Oligosaccharide S3, which accounted for about 30% of the disaccharide units recovered as disaccharides and oligosaccharides, was identified as GlcN-MurAc-GlcNAc-MurAc. Oligosaccharide S1, accounting for about 20% of the disaccharide units recovered, was characterized as GlcN-MurAc-GlcN-MurAc-GlcNAc-MurAc, while oligosaccharide S2, present in a smaller amount, as GlcNAc-MurAc-GlcN-MurAc-glcNAc-MurAc. Oligosaccharides S4, and S5, present in small amounts, were identified as GlcNAc-MurAc-GlcNAc-MurAc and MurAc-GlcNAc-MurAc, respectively. 3. Oligosaccharides S1, S3 and S5 proved to be completely insusceptible to lysozyme, whereas S2 was digsted by lysozyme to produce GlcNAc-MurAc and S3. S1 was found to act as a more potent inhibitor than S3 in lysozyme-catalyzed digestion of polysaccharides. 4. The results obtained show that the lysozyme-catalyzed hydrolysis of peptidoglycan oligosaccharides had an obligatory requirement for the N-acetyl group on the glucosamine residue located in subsite C in the enzyme-substrate complex.

Lipopeptidophosphoglycan from Trypanosoma cruzi. Amide and ester-linked fatty acids.

Lipopeptidophosphoglycan, extracted from whole cells of epimastigote forms of Trypanosoma cruzi, has now been shown to contain 12.6% of fatty acids in addition to the previously identified content of neutral sugars (60%), glucosamine (0.8%), peptide (9.5%) and acid-hydrolyzable phosphate (2%). The main fatty acids are palmitic (6.9%) and lignoceric (4.6%) acids. Stearic (0.55%), oleic (0.15%) and myristic (0.18%) acids were also found. One third of the fatty acids are bound in the lipopeptidophosphoglycan as esters (14 mmol%) and two thirds as amides (28 mmol%). Lignoceric acid was found to be bound only as amide. Two ninhydrin-positive compounds, obtained by chloroform extraction of a total acid hydrolysate of the lipopeptidophosphoglycan, were tentatively identified as sphingosine bases.

Migration inhibition of peritoneal macrophages by peptidoglycan.

Previous studies have shown that peptidoglycans from group A and B streptococci inhibit the migration of peritoneal exudate cells from non-sensitized rats and guinea pigs. In the present studies peptidoglycans from S. aureus and S. epidermidis were found to inhibit the migration of cells to the same extent as group A streptococcal peptidoglycan. In contrast, HSA-pentapeptide, an immunologically active synthetic analog of the peptide moiety of peptidoglycan which is free of the intrinsic toxicity of naturally occurring peptidoglycans, did not induce migration inhibition of peritoneal exudate cells from non-sensitized guinea pigs. Sensitization of animals with 200 mug HSA-pentapeptide emulsified in incomplete Freund's adjuvant significantly reduced the inhibitory effect of streptococcal and staphylococcal peptidoglycan; HSA-pentapeptide again showed no activity. However, when HSA-pentapeptide was tested against cells from animals sensitized with 200 mug HSA-pentapeptide incorporated in complete Freund's adjuvant, a strong inhibition of migration was evident. Skin tests performed in these animals, in contrast to the dermonecrotic reaction elicited by streptococcal or staphylococcal peptidoglycan, revealed a characteristic delay hypersensitivity to HSA-pentapeptide.

A radioactive hapten-binding assay for measuring antibodies to the pentapeptide determinant of peptidoglycan.

A major portion of the humoral immune response to peptidoglycans is directed against the non-cross-linked pentapeptide side chains of these ubiquitous bacterial antigens. At present, no specific and sensitive assay for pentapeptide antibody determination is available. Therefore, a radioimmunoassay has been developed which employs the synthetic pentapeptide hapten L-Ala-gamma-D-Glu-L-Lys-D-Ala-D-Ala, labeled by the active ester method of Bolton and Hunter to high specific activities (6.74 to 18.18 muCi/mug) with 125I, and used as a reagent for measuring pentapeptide antibody. A-variant streptococcal antisera, known to contain pentapeptide antibodies as shown by quantitative precipitation, would bind more than 95% of the radiolabeled hapten in contrast to 2 to 3% by preimmune rabbit sera. Specificity of the binding reaction was demonstrated by inhibition experiments imploying various synthetic oligopeptides related or unrelated to the pentapeptide in the radioimmunoassay. Binding curves established with serial dilutions of peptidoglycan antiserum were linear from 15 to 500 mug/ml of antibody permitting pentapeptide antibody measurement within this range. Comparative data on pentapeptide antibody determinations by quantitative precipitation and radioimmunoassay are given and the time course of the production of this antibody in 14 rabbits hyperimmunized with A-variant streptococcal vaccine is reported.