MALDI-FTMS characterization of oligosaccharides labeled with 9-aminofluorene

9-Aminofluorene (9AmFL) was investigated as an oligosaccharide label. The label was amenable to high UV detectability but did not interfere with mass spectrometric analysis. The 9AmFL label has high molar absorptivity (epsilon = 1.4 x 10(4) L cm(-1) mol(-1) at lambda = 267 nm), is chemically stable, and adds easily in reductive amination to the aldehyde terminus of oligosaccharides. Various linear and branched oligosaccharides were labeled with 9AmFL and the products were purified by chromatography on porous graphitized carbon (PGC). The derivatization reaction gave excellent yields (>95%). Up to 100-fold increase in UV sensitivity at lambda = 206 nm, compared to the corresponding alditol, was observed. Mass spectra were recorded for the labeled compounds. In the presence of sodium dopant, series of Y- and B-fragments were observed. Protonation of the labeled compounds prior to mass spectrometric analysis resulted in simplified spectra (Y-fragments only) and allowed for complete sequence analysis. The retention of the positive charge at the label in the protonated species was consistent with the basicity of the amine. The smallest amount of labeled sugar to be detected by photo-diode array (PDA) was 5 pmol (lambda = 267 nm).

Sparks and puffs in oligodendrocyte progenitors: cross talk between ryanodine receptors and inositol trisphosphate receptors

Investigating how calcium release from the endoplasmic reticulum (ER) is triggered and coordinated is crucial to our understanding of how oligodendrocyte progenitor cells (OPs) develop into myelinating cells. Sparks and puffs represent highly localized Ca(2+) release from the ER through ryanodine receptors (RyRs) and inositol trisphosphate receptors (IP(3)Rs), respectively. To study whether sparks or puffs trigger Ca(2+) waves in OPs, we performed rapid high-resolution line scan recordings in fluo-4-loaded OP processes. We found spontaneous and evoked sparks and puffs, and we have identified functional cross talk between IP(3)Rs and RyRs. Local events evoked using the IP(3)-linked agonist methacholine (MeCh) showed significantly different morphology compared with events evoked using the caffeine analog 3,7-dimethyl-1-propargylxanthine (DMPX). Pretreatment with MeCh potentiated DMPX-evoked events, whereas inhibition of RyRs potentiated events evoked by low concentrations of MeCh. Furthermore, activation of IP(3)Rs but not RyRs was critical for Ca(2+) wave initiation. Using immunocytochemistry, we show OPs express the specific Ca(2+) release channel subtypes RyR3 and IP(3)R2 in patches along OP processes. RyRs are coexpressed with IP(3)Rs in some patches, but IP(3)Rs are also found alone. This differential distribution pattern may underlie the differences in local and global Ca(2+) signals mediated by these two receptors. Thus, in OPs, interactions between IP(3)Rs and RyRs determine the spatial and temporal characteristics of calcium signaling, from microdomains to intracellular waves.

Structure of (-)-neodysidenin from Dysidea herbacea. Implications for biosynthesis of 5,5,5-trichloroleucine peptides

[structure: see text]Neodysidenin was isolated from the marine sponge Dysidea herbacea (Keller 1889) collected on the Great Barrier Reef. The complete configuration was obtained from a combination of methods, including capillary electrophoresis of Marfey's derivatives. Neodysidenin belongs to the L-series of trichloroleucine peptides, and the configuration of the N-methyl thiazolyl alanine residue (13R) is opposite to that of dysidenin.

Herbacic acid, a simple prototype of 5,5,5-trichloroleucine metabolites from the sponge Dysidea herbacea

Dysidea herbacea, collected at Harrier Reef on the Great Barrier Reef, contains the novel metabolite herbacic acid as the major trichloroleucine metabolite. Herbacic acid appears to be an early product of direct free-radical chlorination of leucine and is a prototype for further transformation of the free carboxylic acid group and generation of complex trichloromethyl metabolites, including natural products of the dysidenin family.

Oceanapiside, an antifungal bis-alpha,omega-amino alcohol glycoside from the marine sponge Oceanapia phillipensis

The structure of oceanapiside, an antifungal alpha, omega-bis-aminohydroxylipid glycoside from the temperate marine sponge Oceanapia sp., was elucidated by a combination of 2D NMR, chemical degradation/correlation, and MALDI MS-MS spectrometry. Oceanapiside exhibits antifungal activity against Candida glabrata at 10 micrograms/mL (MIC).

Bastadin 10 stabilizes the open conformation of the ryanodine-sensitive Ca(2+) channel in an FKBP12-dependent manner

The marine sponge Ianthella basta synthesizes at least 25 tetrameric bromotyrosine structures that possess a stringent structural requirement for modifying the gating behavior of ryanodine-sensitive Ca(2+) channels (ryanodine receptors) (RyR)). Bastadin 5 (B5) was shown to stabilize open and closed channel states with little influence on the sensitivity of the channel to activation by Ca(2+) (Mack, M. M., Molinski, T. F., Buck, E. D., and Pessah, I. N. (1994) J. Biol. Chem. 269, 23236-23249). In the present paper, we utilize single channel analysis and measurements of Ca(2+) flux across the sarcoplasmic reticulum to identify bastadin 10 (B10) as the structural congener responsible for dramatically stabilizing the open conformation of the RyR channel, possibly by reducing the free energy associated with closed to open channel transitions (DeltaG*c --> o). The stability of the channel open state induced by B10 sensitized the channel to activation by Ca(2+) to such an extent that it essentially obviated regulation by physiological concentrations of Ca(2+) and relieved inhibition by physiological Mg(2+). These actions of B10 were produced only on the cytoplasmic face of the channel, were selectively eliminated by pretreatment of channels with FK506 or rapamycin, and were reconstituted by human recombinant FKBP12. The actions of B10 were found to be reversible. A structure-activity model is proposed by which substitutions on the Eastern and Western hemispheres of the bastarane macrocycle may confer specificity toward the RyR1-FKBP12 complex to stabilize either the closed or open channel conformation. These results indicate that RyR1-FKBP12 complexes possesses a novel binding domain for phenoxycatechols and raise the possibility of molecular recognition of an endogenous ligand.

Practical synthesis of 2,6-dideoxy-D-lyxo-hexose ("2-deoxy-D-fucose") from D-galactose

2,6-Dideoxy-D-lyxo-hexose was prepared efficiently from D-galactose in eight steps (25% overall yield). The synthesis is amenable to multigram scale-up.

Agelastatins C and D, new pentacyclic bromopyrroles from the sponge Cymbastela sp., and potent arthropod toxicity of (-)-agelastatin A

Two new agelastatins, C (3) and D (4), along with the known compound (-)-agelastatin A (1), were isolated from the Indian Ocean sponge Cymbastela sp. The structures were determined by analysis of spectroscopic data and chemical correlation of 4 with a common derivative 5, also prepared from 1. Agelastatin A (1) exhibited potent activity against brine shrimp (LC50 1.7 ppm) in addition to insecticidal activity against larvae of beet army worm, Spodoptera exigua, and corn rootworm, Diabrotica undecimpunctata.

Xestospongins: potent membrane permeable blockers of the inositol 1,4,5-trisphosphate receptor

Xestospongins (Xe's) A, C, D, araguspongine B, and demethylxestospongin B, a group of macrocyclic bis-1-oxaquinolizidines isolated from the Australian sponge, Xestospongia species, are shown to be potent blockers of IP3-mediated Ca2+ release from endoplasmic reticulum vesicles of rabbit cerebellum. XeC blocks IP3-induced Ca2+ release (IC50 = 358 nM) without interacting with the IP3-binding site, suggesting a mechanism that is independent of the IP3 effector site. Analysis of Pheochromocytoma cells and primary astrocytes loaded with Ca2+-sensitive dye reveals that XeC selectively blocks bradykinin- and carbamylcholine-induced Ca2+ efflux from endoplasmic reticulum stores. Xe's represent a new class of potent, membrane permeable IP3 receptor blockers exhibiting a high selectivity over ryanodine receptors. Xe's are a valuable tool for investigating the structure and function of IP3 receptors and Ca2+ signaling in neuronal and nonneuronal cells.

Bastadins relate ryanodine-sensitive and -insensitive Ca2+ efflux pathways in skeletal SR and BC3H1 cells

Bastadins potently interact with the FK-506-binding protein of 12 kDa (FKBP12)-ryanodine receptor (Ry1R) complex in skeletal muscle to enhance a high-affinity ryanodine binding conformation (M. M. Mack, T. F. Molinski, E. D. Buck, and I. N. Pessah. J. Biol. Chem. 269: 23236-23249, 1994). Bastadins are used to examine the relationship between ryanodine-sensitive and ryanodine-insensitive Ca2+ efflux pathways that coexist in junctional sarcoplasmic reticulum (SR) vesicles from rabbit skeletal muscle and differentiated BC3H1 cells. Complete block of caffeine-sensitive Ca2+ channels with micromolar ryanodine or ruthenium red does not alter the steady-state loading capacity of SR. Inhibition of sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA) pumps with thapsigargin unmasks a ryanodine- and ruthenium red-insensitive Ca2+ efflux pathway. Bastadin 5 alone does not inhibit Ca2+ efflux unmasked by inhibition of SERCA pumps, but, in combination with blocking concentrations of ryanodine or ruthenium red, it eliminates the ryanodine-insensitive Ca2+ "leak" and enhances steady-state loading capacity of SR vesicles approximately 2.5-fold. These actions of bastadins occur in the same concentration range that enhances the number of high-affinity binding sites for [3H]ryanodine (50% effective concentration of approximately 2 microM). Similar effects on SR Ca2+ transport are found with FK-506 and ryanodine in combination. Block of Ry1R in intact BC3H1 cells with ryanodine does not eliminate the prominent Ca2+ leak unmasked by thapsigargin. A membrane-permeant mixture of bastadins in combination with ryanodine nearly eliminates the Ca2+ leak unmasked by thapsigargin, even though the Ca2+ stores are replete. The requirement of both a known Ry1R blocker and bastadins in combination provides a pharmacological link between ryanodine-sensitive Ca2+ channels and ryanodine-insensitive leak pathways in isolated junctional SR and BC3H1 cells. Together, these results strongly suggest that bastadins, through their modulatory actions on the FKBP12-Ry1R complex, convert ryanodine-insensitive leak states into ryanodine-sensitive channels that recognize [3H]ryanodine with high affinity.

Bastadin 20 and bastadin O-sulfate esters from Ianthella basta: novel modulators of the Ry1R FKBP12 receptor complex

New compounds bastadin 20 (9), 15,34-O-disulfatobastadin 7 (10), and 10-O-sulfatobastadin 3 (11) were isolated from Ianthella basta collected in Exmouth Gulf, Western Australia. Compounds 10 and 11 exhibited moderate differential activity as SR Ca2+ channel agonists (EC50 13.6 and 100 microM, respectively) of the Ry1R FKBP12 complex, while the potency of 9 was almost half that of 10 (EC50 20.6 microM). The problem of dereplication of bastadins was addressed using 1H-NMR "fingerprinting" of MeO signals in the corresponding permethyl bastadin derivatives.

A psychrophilic crenarchaeon inhabits a marine sponge: Cenarchaeum symbiosum gen. nov., sp. nov

Archaea, one of the three major domains of extant life, was thought to comprise predominantly microorganisms that inhabit extreme environments, inhospitable to most Eucarya and Bacteria. However, molecular phylogenetic surveys of native microbial assemblages are beginning to indicate that the evolutionary and physiological diversity of Archaea is far greater than previously supposed. We report here the discovery and preliminary characterization of a marine archaeon that inhabits the tissues of a temperate water sponge. The association was specific, with a single crenarchaeal phylotype inhabiting a single sponge host species. To our knowledge, this partnership represents the first described symbiosis involving Crenarchaeota. The symbiotic archaeon grows well at temperatures of 10 degrees C, over 60 degrees C below the growth temperature optimum of any cultivated species of Crenarchaeota. Archaea have been generally characterized as microorganisms that inhabit relatively circumscribed niches, largely high-temperature anaerobic environments. In contrast, data from molecular phylogenetic surveys, including this report, suggest that some crenarchaeotes have diversified considerably and are found in a wide variety of lifestyles and habitats. We present here the identification and initial description of Cenarchaeum symbiosum gen. nov., sp. nov., a symbiotic archaeon closely related to other nonthermophilic crenarchaeotes that inhabit diverse marine and terrestrial environments.

Exact mass determination for elemental analysis of ions produced by matrix-assisted laser desorption

The exact masses of bastadins, cyclic peptides from marine sponges Ianthella basta, are determined using matrix-assisted laser desorption ionization (MALDI) coupled to a Fourier transform mass spectrometer. Two known compounds were mixed with the unknown to serve as internal calibrants. The mass of the calibrants bracketed the mass of the unknown compound. With this method, exact masses were obtained to within 5 ppm for single determinations, and less than 3 ppm for multiple determinations, allowing the derivation of elemental composition. This method is viable for routinely obtaining the exact masses of new compounds with MALDI.

4-Dehydroecdysterone, a new ecdysteroid from the zoanthid Parazoanthus sp

A novel ecdysteroid, 4-dehydroecdysterone [3], has been isolated from the zoanthid Parazoanthus sp. collected from Port Phillip Bay, Australia. The known ecdysteroids ecdysterone [1] and ajugasterone C [2] were also isolated, together with the known alkaloid paragracine [4].

Novel modulators of skeletal muscle FKBP12/calcium channel complex from Ianthella basta. Role of FKBP12 in channel gating

Macrocyclic natural products derived from bromotyrosine isolated from the sponge Ianthella basta are shown to selectively modulate the skeletal isoform of the ryanodine-sensitive sarcoplasmic reticulum calcium channel by a novel mechanism involving the FKBP12/RyR-1 complex. Bastadins 5, 7, and the newly identified isomer of bastadin 5, bastadin 19, show marked differences in potency and efficacy toward activation of the binding of [3H]ryanodine. In physiological salt, bastadin 5 (5 microM) increases the [3H]ryanodine binding capacity of SR membranes 5-fold, by stabilizing the high affinity conformation of RyR-1 for ryanodine without shifting the affinity of the activator site for Ca2+ or altering the response to caffeine or adenine nucleotides. Bastadin 5 decreases the inhibitory potency of Mg2+ 8-fold and high (> 100 microM) Ca2+ 5-fold. Bastadin 5 inhibits Ca2+ uptake into SR vesicles and enhances Ca(2+)-induced Ca2+ release 8-fold. Bastadin 5 increases single-channel open dwell time, tau 1 and tau 2, 65- and 92-fold, respectively, without changing unitary conductance for Cs+ (450 picosiemans) or open probability. Most significant is the finding that the unique actions of bastadin 5 on [3H]ryanodine binding and Ca2+ transport are antagonized by the immunosuppressant FK506. FK506 alone weakly enhances the binding of [3H]ryanodine, compared to bastadin 5. However, FK506 diminishes bastadin 5-induced changes in [3H]ryanodine binding and Ca2+ transport without altering the efficacy of adenine nucleotides. Unlike FK506, bastadin 5 does not directly promote the dissociation of FKBP12 from the RyR-1 membrane complex; however, it markedly enhances the release of FKBP12 induced by FK506. These results suggest that the bastadin 5 effector site is a novel modulatory domain on FKBP12. Bastadins represent a new class of compounds to gain insight into the functional interactions between FKBP12 and RyR-1.

Screening of marine invertebrates for the presence of ergosterol-sensitive antifungal compounds

A simple in vitro agar disk diffusion assay has been employed to detect the presence of ergosterol-sensitive antifungal activity in extracts of marine invertebrates. A collection of 116 marine sponges, ascidians, and cnidarians was assayed to reveal 10 samples (8.3%) with significant activity against Candida albicans. The antifungal activities of three of these extracts were unaffected in the presence of increasing concentrations of ergosterol, while another three were significantly reduced by ergosterol. The activity of jaspamide [3], a potent antifungal from the sponge Jaspis sp., was also reduced by ergosterol concentrations as low as 10 ppm. This ergosterol sensitivity is paralleled by the well-known ergosterol dependence of polyene antifungals, such as amphotericin B [1], and suggests a common mode of activity. The assay may be useful in mechanism-selective screening for new antifungals and as a dereplication tool.

Developments in marine natural products. Receptor-specific bioactive compounds

The discovery of thousands of new marine natural products over the past two decades has been spurred by findings of potent bioactivity. In recent years it has become apparent that many such compounds have affinities for certain cellular receptors in the mammalian cell, functional properties that may also play a part in the largely unknown roles of these compounds in their respective parent organisms. Our work in marine natural products has led to the discovery of compounds with significant activity in several assays with importance in understanding fundamental cellular processes and treatment of human disease states. We present recent work on the isolation of new bioactive compounds from marine invertebrates with profound activity on mammalian and non-mammalian receptors.

Synthetic Studies on Wedeligenin: Preparation of 3-Hydroxy-Substituted Decalincarbonitriles as a Model for 'A Ring' Annulation

Six new 3-hydroxydecalincarbonitriles were synthesized by employing an annulation strategy involving intramolecular alkylation of 5-bromoalkyl substituted malononitriles or acetonitriles. 2-Allyl-2-methylcyclohexanone was condensed with malononitrile to give the dialkylcyclohexylidenepropanedinitrile (14). Alternatively, Horner-Emmons- Wittig condensation of the same ketone with diethyl cyanomethylphosphonate gave the corresponding acetonitrile (28). Reduction of the dinitrile with sodium borohydride to give a mixture of cis and trans cyclohexyl malononitriles followed by epoxidation of the allyl substituent, gave a separable mixture of four epoxides, two of which, (17) and (19), were site-selectively ring-opened to the bromohydrins. Each bromohydrin was quantitatively converted into its respective O- trimethylsilyl bromohydrin ether and cyclized to afford the respective decalindicarbonitriles (6) and (7). The substituted acetonitrile (28) was reduced to a 5 : 2 mixture of the corresponding cyclohexylacetonitriles with magnesium in methanol and the products were carried through to their respective O- trimethylsilyl bromohydrin ethers and cyclized to afford decalincarbonitriles (8)-(11). The structure and stereochemistry of the new decalins were assigned by 1H and 13C n.m.r. spectroscopy.

The stability of allylic and vinylic deuterium atoms during the lithium/ammonia reduction of some styrenoid systems

Reduction of 2-(p-methoxyphenyl)cyclohexan-1-one (8) with lithium aluminium deuteride followed by acetylation gave trans-l-acetoxy-2-(p-methoxyphenyl)(1-2H1)cycohexane (10b). Base-catalysed deuteration of 2-(p-methoxypheny1)cyclohexan-1-one (8) afforded the corresponding trideuterated ketone (11a) which upon hydride reduction and acetylation yielded trans-1-acetoxy-2-(p-methoxy- phenyl)(2,6,6-2H3)cyclohexane (15b). Pyrolysis of the acetate (10b) at 600�/1.0 mm gave 1-(p-methoxyphenyl)(2-2H1)cyclohex-1-ene (16) which was separated from the unconjugated isomer (13) by preparative g.l.c. 1-(p-Methoxyphenyl)(3,3-2H2)cyclohex-1-ene (18) was similarly obtained by pyrolysis of the trideutero acetate (15b). Lithium/ammonia reduction of the deuterated styrenoid compounds (16) and (18) proceeded in each case without any detectable loss or redistribution of the deuterium atoms.