Chemical Ecology The Chemistry of Biotic Interaction (1995) / Chapter Skim
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The Chemistry of Gamete Attraction: Chemical Structures, Biosynthesis, and ...
The Chemistry of Gamete Attraction: Chemical Structures, Biosynthesis, and ...
Pages 87-102
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From page 87... ...
Endoparasite Protection Against Host Immune Defenses / 85 76. Schmid, S
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isolated the first pheromone of a marine brown alga. The compound was collected from laboratory cultures of fertile female gametophytes of the cosmopolitan brown alga Ectocarpus siliculosus.
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From page 91... ...
The identification of the individual compounds follows from mass spectrometry and from comparison with synthetic reference compounds (21. The biological activity of the identified compounds is assayed by exposing microdroplets of a water immiscible, high density solvent with known concentrations of the compounds to male gametes in sea water (201.
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From page 92... ...
(3-6~. The ability of a compound to induce mass release of male gametes is approached by exposing mature male gametophytes of a species to particles of porous silica previously loaded with the test substances.
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From page 93... ...
Recent advances in gas chromatographic separations of enantiomers allow precise determination of the enantiomeric purity of the algal pheromones. The cis-disubstituted cyclopentenes, such as multifidene, viridiene, and caudoxirene, are of high optical purity ~-95% enantiomeric excess (e.e.~]
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is virtually racemic (191. It is tempting to assume that for marine brown algae the production of characteristic enantiomeric mixtures represents a simple means for individualization of the signal blends, although up to now there is no experimental confirmation for this hypothesis.
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In marine brown algae the family of unsaturated C20 fatty acids provides another, potentially abundant source of suitable precursors (351. Interestingly, the first biosynthetic experiments with [3H]
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-sigmatropic rearrangement. The fatty acid accommodates to the active center of the enzyme in a U-shaped fashion.
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as shown in Figure 6, once again, the disubstituted cyclopropane will be released from the active center as a thermolabile intermediate. Although this mechanistic hypothesis has not yet been experimentally confirmed, the concept nevertheless provides a valuable platform for the systematic derivation of all the known Cal hydrocarbons from the fatty acid precursors.
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From page 98... ...
The latter suffers a spontaneous t1.71hydrogen shift, and it is the helical transition state structure of this antarafacial hydrogen shift that accounts for the observed stereochemistry of the product (Figure 7a)
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-tetraene were produced by homolytic cleavage of a suitable fatty acid hydroperoxide, this acyclic olefin should readily undergo an 8 Tre electrocyclic ring closure (Figure 7b)
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are collected. For example, volatiles collected from cultures of fertile gynogametophytes of Dictyota diemensis exhibit, besides dictyotene, a complex pattern of oxygenated compounds, as shown in Figure 8 (471.
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From page 101... ...
However, final conclusions about the biotic contribution to the pheromone transformation cannot be drawn before careful analysis of the degree of enantioselectivity of the biotic reaction. SUMMARY Female gametes of marine brown algae release and/or attract their conspecific males by chemical signals.
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From page 102... ...
. Compounds 1-14 are isolated products of an oxidative degradation of dictyotene by a radical pathway induced by the system TPPMn/Ph-I=C)
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