Chemical Composition and Antimicrobial Activity of Ageratina deltoidea

The chemical study of Ageratina deltoidea afforded grandiflorenic acid ( 1 ), ent‐kaurenoic acid ( 2 ), and eight benzylbenzoates ( 3  –  10 ), two of them, 3,5‐dimethoxybenzyl 2,3,6‐trimethoxybenzoate ( 5 ) and 4‐(β‐d ‐glucopyranosyloxy)‐3‐hydroxybenzyl 2,6‐dimethoxybenzoate ( 9 ), described for the first time. In addition, the new sesquiterpene lactone deltoidin C ( 13 ), together with the known 11 and 12 , the phenolic compounds: ayanin, 2,6‐dimethoxybenzoic acid, methyl 3,4‐dihydroxycinnamate, chlorogenic acid, and 3,5‐dicaffeoylquinic acid were also isolated. The structures of these compounds were determined by spectroscopic methods and chemical reactions. The antibacterial and antifungal activities of compounds 1  –  12 were evaluated on Staphylococcus aureus, Escherichia coli, and Candida albicans. Deltoidin A ( 11 ) was the most active antibacterial agent (MIC 16.0 μg ml^?1) against E. coli, and the ent‐kaurenoid derivatives ( 1  –  2 ) showed activity (MIC 31.0 μg ml^?1) against S. aureus.     

Classification of protein families and detection of the determinant residues with an improved self-organizing map

 Using a SOM (self-organizing map) we can classify sequences within a protein family into subgroups that generally correspond to biological subcategories. These maps tend to show sequence similarity as proximity in the map. Combining maps generated at different levels of resolution, the structure of relations in protein families can be captured that could not otherwise be represented in a single map. The underlying representation of maps enables us to retrieve characteristic sequence patterns for individual subgroups of sequences. Such patterns tend to correspond to functionally important regions. We present a modified SOM algorithm that includes a convergence test that dynamically controls the learning parameters to adapt them to the learning set instead of being fixed and externally optimized by trial and error. Given the variability of protein family size and distribution, the addition of this feature is necessary. The method is successfully tested with a number of families. The rab family of small GTPases is used to illustrate the performance of the method. Received: 25 July 1996 / Accepted in revised form: 13 February 1997     

AFLP Linkage Map of the Oomycete Phytophthora infestans

Here we present the first comprehensive genetic linkage map of the heterothallic oomycetous plant pathogen Phytophthora infestans. The map is based on polymorphic DNA markers generated by the DNA fingerprinting technique AFLP (Vos et al., 1995, Nucleic Acids Res. 23: 4407-4414). AFLP fingerprints were made from single zoospore progeny and 73 F1 progeny from two field isolates of P. infestans. The parental isolates appeared to be homokaryotic and diploid, their AFLP patterns were mitotically stable, and segregation ratios in the F1 progeny were largely Mendelian. In addition to 183 AFLP markers, 7 RFLP markers and the mating type locus were mapped. The linkage map comprises 10 major and 7 minor linkage groups covering a total of 827 cM. The major linkage groups are composed of markers derived from both parents, whereas the minor linkage groups contain markers from either the A1 or the A2 mating type parent. Non-Mendelian segregation ratios were found for the mating type locus and for 13 AFLP markers, all of which are located on the same linkage group as the mating type locus. Copyright 1997 Academic Press     

Leptocarpin and 17,18-dihydroleptocarpin,two new heliangolides from Leptocarpha rivularis

The isolation and structure determination of two new sesquiterpene lactones of the heliangolide type, leptocarpin and 17,18-dihydroleptocarpin from Leptocarpha rivularis, are described. The structure of leptocarpin was established as the 8β-angeloyl ester of 3β,8β-dihydroxy germacra-4,11(13)-dien- 1(10)-oxido-6α,12-olide. The second component was the 17,18-dihydro derivative of leptocarpin.     

A novel peptide conformation: First unequivocal observation of the oxy-analog of a β-bend

The x-ray diffraction analysis of the N-benzyloxycarbonyl homo-tripeptide from α-amino-isobutyric acid has shown the occurrence of an incipient 3₁₀-helix characterized by one type-III (or type-III′) β-bend followed by one oxy-analog of the same type of β-bend. This represents the first unequivocal observation of the latter conformation, where the O—H group of the COOH moiety present at the C-terminus of the peptide main chain plays the role of the hydrogen-bonding donor. These results have been compared with those of the same peptide in its monohydrate form and of its methyl ester derivative, the x-ray diffraction structures of which are also described here.     

The Influence of Age,Sex, and Rank on Yawning Behavior in Two Species of Macaques (Macaca fascicularis and M. fuscata)

Yawning behavior was studied in two species of macaques: the long-tailed macaque (Macaca fascicularis) and the Japanese macaque (M. fuscata). Japanese macaques yawned much more than long-tailed macaques. Age, sex, and dominance rank exerted different effects on yawning in the two species. In the long-tailed macaques, sex differences in frequency of yawning emerged only after sexual maturity; yawning rates increased significantly in both males and females as they reached sexual maturity; and, among males, dominance rank was positively correlated with frequency of yawning. Differently, in the Japanese macaques, males, both mature and immature, yawned more than same-aged females; sexual maturity was associated with an increase in yawning in males only; and male rank did not correlate with the frequency of yawning. Regardless of interspecific differences, the overall results supported only in part the finding that, in Old World monkeys, yawning is largely influenced by plasma concentrations of androgens. There was evidence that social factors were also important in influencing the age-sex class distribution of yawning.     

In Vivo Release of Dopamine and Its Metabolites from Rat Striatum in Response to Domoic Acid

The microdialysis technique was used to examine the effect of the neurotoxin domoate, an analog of glutamic acid, on striatal dopamine activity. Our results show that the intracerebral administration of different concentrations of domoate (100 and 500 M) produced increases in the extracellular levels of dopamine associated to decreases in the extracellular levels of its metabolites dihydroxyphenylacetate and homovanillate from rat striatum. These changes seem to be related according to a time sequence, indicating a possible effect on the metabolism of dopamine. Changes were also observed in locomotor activity (cycling behavior, sniffing around and chewing) in rats during the domoate infusion. The physiological mechanism by which domoate increased dopamine release remains to be worked out.     

Regio- and stereoselective dimerization of 1-alkynes catalyzed by an Os(II) complex

The complex [(PP₃)OsH(N₂)]BPh₄ is a catalyst precursor for the regio- and stereoselective dimerization of HCCR (R=Ph, SiMe₃) to (Z)-1,4-disubstituted-but-3-en-l-ynes (PP₃=P(CH₂CH₂PPh₂)₃). In the presence of H₂O or C₂H₅OH, the catalytic reaction with HCCSiMe₃ selectively gives but-3-en-l-ynyl-trimethyisilane. A detailed study under different experimental conditions, the detection of some intermediates, and the use of isolated complexes in independent reactions, taken altogether, permit mechanistic conclusions which account for the observed products. A key-role is played by (vinylidene)σ-alkynyl complexes which transform into η³-butenynyl derivatives via intramolecular C---C bond formation. The Os(II) η³-butenynyl complexes are likely reagents in the rate determining step of the catalytic cycle, and produce free (Z)-1,4-disubstituted-but-3-en-l-ynes upon σ-bond metathesis reaction with HCCR. The 16-electron fragments [(PP₃)OsX]⁺ (X = H, Cl, CCR) are capable of promoting the 1-alkyne to vinylidene tautomerism. In particular, the (vinylidene)hydride [(PP₃)OsH{C=C(H)-SiMe₃}]BPh₄ has been isolated and properly characterized. Since the stoichiometric reaction of the latter compound with HCCSiMe₃ gives vinyltrimethylsilane, the formation of (vinylidene)hydride species is suggested to be an effective step, alternative to 1-alkyne insertion, in the reduction of 1-alkynes to alkenes assisted by hydrido metal complexes.