Mechanical Properties of the Beetle Elytron, a Biological Composite Material

Chemical and Petroleum Engineering, University of Kansas, Lawrence, Kansas 66045, USA.
Biomacromolecules (Impact Factor: 5.79). 02/2011; 12(2):321-35. DOI: 10.1021/bm1009156
Source: PubMed

ABSTRACT We determined the relationship between composition and mechanical properties of elytra (modified forewings that are composed primarily of highly sclerotized dorsal and less sclerotized ventral cuticles) from the beetles Tribolium castaneum (red flour beetle) and Tenebrio molitor (yellow mealworm). Elytra of both species have similar mechanical properties at comparable stages of maturation (tanning). Shortly after adult eclosion, the elytron of Tenebrio is ductile and soft with a Young's modulus (E) of 44 ± 8 MPa, but it becomes brittle and stiff with an E of 2400 ± 1100 MPa when fully tanned. With increasing tanning, dynamic elastic moduli (E') increase nearly 20-fold, whereas the frequency dependence of E' diminishes. These results support the hypothesis that cuticle tanning involves cross-linking of components, while drying to minimize plasticization has a lesser impact on cuticular stiffening and frequency dependence. Suppression of the tanning enzymes laccase-2 (TcLac2) or aspartate 1-decarboxylase (TcADC) in Tribolium altered mechanical characteristics consistent with hypotheses that (1) ADC suppression favors formation of melanic pigment with a decrease in protein cross-linking and (2) Lac2 suppression reduces both cuticular pigmentation and protein cross-linking.

Download full-text


Available from: Stevin H. Gehrke, Jan 24, 2015
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Genome analyses revealed in various basidiomycetes the existence of multiple genes for blue multi-copper oxidases (MCOs). Whole genomes are now available from saprotrophs, white rot and brown rot species, plant and animal pathogens and ectomycorrhizal species. Total numbers (from 1 to 17) and types of mco genes differ between analyzed species with no easy to recognize connection of gene distribution to fungal life styles. Types of mco genes might be present in one and absent in another fungus. Distinct types of genes have been multiplied at speciation in different organisms. Phylogenetic analysis defined different subfamilies of laccases sensu stricto (specific to Agaricomycetes), classical Fe2+-oxidizing Fet3-like ferroxidases, potential ferroxidases/laccases exhibiting either one or both of these enzymatic functions, enzymes clustering with pigment MCOs and putative ascorbate oxidases. Biochemically best described are laccases sensu stricto due to their proposed roles in degradation of wood, straw and plant litter and due to the large interest in these enzymes in biotechnology. However, biological functions of laccases and other MCOs are generally little addressed. Functions in substrate degradation, symbiontic and pathogenic intercations, development, pigmentation and copper homeostasis have been put forward. Evidences for biological functions are in most instances rather circumstantial by correlations of expression. Multiple factors impede research on biological functions such as difficulties of defining suitable biological systems for molecular research, the broad and overlapping substrate spectrum multi-copper oxidases usually possess, the low existent knowledge on their natural substrates, difficulties imposed by low expression or expression of multiple enzymes, and difficulties in expressing enzymes heterologously.
    Current Genomics 04/2011; 12(2):72-94. DOI:10.2174/138920211795564377 · 2.87 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The insect cuticle is a composite biomaterial made up primarily of chitin and proteins. The physical properties of the cuticle can vary greatly from hard and rigid to soft and flexible. Understanding how different cuticle types are assembled can aid in the development of novel biomimetic materials for use in medicine and technology. Toward this goal, we have taken a combined proteomics and transcriptomics approach with the red flour beetle, Tribolium castaneum, to examine the protein and gene expression profiles of the elytra and hindwings, appendages that contain rigid and soft cuticles, respectively. Two-dimensional gel electrophoresis analysis revealed distinct differences in the protein profiles between elytra and hindwings, with four highly abundant proteins dominating the elytral cuticle extract. MALDI/TOF mass spectrometry identified 19 proteins homologous to known or hypothesized cuticular proteins (CPs), including a novel low complexity protein enriched in charged residues. Microarray analysis identified 372 genes with a 10-fold or greater difference in transcript levels between elytra and hindwings. CP genes with higher expression in the elytra belonged to the Rebers and Riddiford family (CPR) type 2, or cuticular proteins of low complexity (CPLC) enriched in glycine or proline. In contrast, a majority of the CP genes with higher expression in hindwings were classified as CPR type 1, cuticular proteins analogous to peritrophins (CPAP), or members of the Tweedle family. This research shows that the elyra and hindwings, representatives of rigid and soft cuticles, have different protein and gene expression profiles for structural proteins that may influence the mechanical properties of these cuticles.
    Journal of Proteome Research 11/2011; 11(1):269-78. DOI:10.1021/pr2009803 · 5.00 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Insects of extremely small size have evolved to solve many problems. Their structure and mechanical properties information can be utilized to mimic them for industrial applications. Since beetle (Coleoptera, an order of insects) wings exhibit special functionalities, they have sparked worldwide research attention. Beetle wings are composed of a forewing (also known as elytron) and a hind wing. The elytra are rigid. A beetle's functional wings, which allow flying, are the hind wings. The elytra have an ingenious structure with superhydrophobic characteristics, a structural coloration and anti-adhesion characteristics. Their inner structure helps to provide light mass and high strength. The rotation angle and wing locking system of elytra are important features which increase beetles' ability to fly; they may furnish an insight for portable micro air vehicles (MAVs) and also provide inspiration for the design of bioinspired deployable systems. Studies of the structural and mechanical properties in biological systems may improve the understanding of natural solutions and advance the design of novel artificial materials. In this paper, the structure, mechanical properties and their relationship to function of beetle wings are discussed. Examples of bioinspired structures and materials are also presented.
    RSC Advances 01/2012; 2(33):12606-12623. DOI:10.1039/c2ra21276e · 3.84 Impact Factor
Show more