Insect Lipids: Chemistry, Biochemistry, and Biology

By David W. Stanley-Samuelson; Dennis R. Nelson | Go to book overview

1992). However, the proximity of a second methyl branch may suppress the β-cleavage.

The methyl branch positions deduced from the mass spectra of the acetate esters were initially confirmed ( Nelsonet al., 1989; Nelsonet al., 1990a) by converting the alcohol to the bromide and then reducing with LiAlH4 ( Nishidaet al., 1976). However, this procedure does not label the end of the molecule which had the hydroxyl group so the position of the methyl branches with respect to the hydroxyl is not known. Therefore, the VLMA and LMA were converted to their mesylates ( Crossland and Servis, 1970) and reduced with LiAlD4 ( Simonet al., 1990). The mass spectra of the deuteride methyl-branched alkanes gave clear evidence of the position of the hydroxyl and of the methyl branch(es) ( Nelson and Fatland, 1992b).

Small amounts of chloride derivatives of the VLMA were formed in the procedure to make the deuteride derivatives. The mass spectra of the chloride derivatives also gave clear evidence of the position of the hydroxyl and of the methyl branch(es) ( Nelson and Fatland, 1992b). Therefore, the chloride derivatives of the LMA and the VLMA were directly prepared by heating with methanesulfonyl chloride in dimethylformamide ( Evanset al., 1968). The chloride derivatives are probably a better choice than the deuteride derivatives. In weak mass spectra, or in mass spectra with other components present or column bleed, it may be difficult or impossible to determine whether the diagnostic ion from a deuteride derivative has increased by one amu. The chloride-containing fragment ions occur at m/z values removed from those of hydrocarbons and the presence of the chlorine isotopes results in characteristic clusters of ions for each chloride- containing fragment ( Guoet al., 1992; Nelson and Fatland, 1992b) clearly establishing the hydroxyl end of the molecule and the methyl branch point.


8 Concluding Remarks

The methyl-branched hydrocarbons, as components of the cuticular lipids, serve important functions in limiting water loss and in the broad area of chemical communication and kin/nestmate recognition among insects. On the other hand, the function of the methyl-branched alcohols is not known. They have not been found among the cuticular lipids of any life stage and are only found in major amounts within the pupae of Lepidoptera. Although the alcohols have methyl-branching positions similar to those of the methyl-branched hydrocarbons, the positions are different enough to indicate that there is not a precursor-product relationship between the hydrocarbons and the alcohols. In pupae, the lack of neutral lipid synthesis is consistent with the lack of feeding and the low levels of

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Insect Lipids: Chemistry, Biochemistry, and Biology
Table of contents

Table of contents

  • Title Page iii
  • Contributors v
  • Contents ix
  • Preface xi
  • References xiii
  • Lipoproteins and Lipid Transport 1
  • 7: Concluding Remarks 20
  • References 21
  • Structure and Function of Manduca Sexta Hemolymph Lipid Transfer Particle 25
  • Acknowledgments 40
  • The Biological Significance of Prostaglandins and Related Eicosanoids in Insects 45
  • 1: Introduction 46
  • Acknowledgments 88
  • Arachidonate Metabolism in Tick Salivary Glands 99
  • 1: Introduction 100
  • Acknowledgments 129
  • References 130
  • Prostanoids and Fluid Balance in Insects 139
  • Acknowledgments 172
  • Cuticular Hydrocarbons and Chemical Communication 179
  • Acknowledgments 212
  • Cuticular Polar Lipids of Insects 227
  • 1: Introduction 228
  • References 261
  • Methyl-Branched Lipids in Insects 271
  • 8: Concluding Remarks 301
  • Hydrocarbon and Hydrocarbon Derived Sex Pheromones in Insects: Biochemistry and Endocrine Regulation 317
  • 1: Abstract 318
  • Acknowledgments 341
  • Biosynthesis and Endocrine Regulation of Fatty Acid Derived Sex Pheromones in Moths 353
  • 1: Introduction 353
  • 4: Conclusion 379
  • Lipid Biochemistry in Aphids 389
  • 1: Introduction 389
  • 12: Conclusions and Future Directions 423
  • References 424
  • Species Name Index 435
  • Common Name Index 443
  • Subject Index 449
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