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Crystals: animal, vegetable or mineral?

Hyde ST - Interface Focus (2015)

Bottom Line: The idea that there is a clear distinction between these two classes of matter has waxed and waned in popularity through past centuries.The older picture of disjoint universes of forms is better understood as a continuum of forms, with significant overlap and common features unifying biological and inorganic matter.In addition to the philosophical relevance of this perspective, there are important ramifications for science.

View Article: PubMed Central - PubMed

Affiliation: Department of Applied Mathematics, Research School of Physics and Engineering , The Australian National University , Canberra, Australian Capital Territory 0200 , Australia.

ABSTRACT
The morphologies of biological materials, from body shapes to membranes within cells, are typically curvaceous and flexible, in contrast to the angular, facetted shapes of inorganic matter. An alternative dichotomy has it that biomolecules typically assemble into aperiodic structures in vivo, in contrast to inorganic crystals. This paper explores the evolution of our understanding of structures across the spectrum of materials, from living to inanimate, driven by those naive beliefs, with particular focus on the development of crystallography in materials science and biology. The idea that there is a clear distinction between these two classes of matter has waxed and waned in popularity through past centuries. Our current understanding, driven largely by detailed exploration of biomolecular structures at the sub-cellular level initiated by Bernal and Astbury in the 1930s, and more recent explorations of sterile soft matter, makes it clear that this is a false dichotomy. For example, liquid crystals and other soft materials are common to both living and inanimate materials. The older picture of disjoint universes of forms is better understood as a continuum of forms, with significant overlap and common features unifying biological and inorganic matter. In addition to the philosophical relevance of this perspective, there are important ramifications for science. For example, the debates surrounding extra-terrestrial life, the oldest terrestrial fossils and consequent dating of the emergence of life on the Earth rests to some degree on prejudices inferred from the supposed dichotomy between life-forms and the rest.

No MeSH data available.


Related in: MedlinePlus

X-ray diffraction patterns from a point source. (a) Zincblende (ZnS) crystal diffraction, recorded by P. Ewald; image from The Crystalline State by W.H. and W.L. Bragg; (b) cellulose fibres, oriented vertically [7]; (c) a lock of Mozart's hair, and (d) α-keratin diffraction pattern, from Mozart's hair (oriented obliquely) by William Astbury's colleague, Elwynn Beighton, in 1958.
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RSFS20150027F3: X-ray diffraction patterns from a point source. (a) Zincblende (ZnS) crystal diffraction, recorded by P. Ewald; image from The Crystalline State by W.H. and W.L. Bragg; (b) cellulose fibres, oriented vertically [7]; (c) a lock of Mozart's hair, and (d) α-keratin diffraction pattern, from Mozart's hair (oriented obliquely) by William Astbury's colleague, Elwynn Beighton, in 1958.

Mentions: Diffraction relies on highly ordered, indeed crystalline (or quasi-crystalline) arrangements of scattering constituents, namely atoms or, via small-angle X-ray diffraction, molecules. (Here I use the term ‘diffraction’ in the conventional sense of wave interference producing discrete diffraction spots, in contrast to ‘scattering’, which gives diffuse intensity distributions in reciprocal space. Given recent developments with very high powered light sources such as X-ray free-electron lasers, this distinction is fading, with the advent of ‘nano diffraction’ techniques [6]). So the question of whether crystallography is helpful in understanding biological structures is worth asking. As the Russian theoretician of crystalline symmetries, Fedorov, said ‘Crystallisation is death’ [3]! In spite of the perceived gulf between animals and minerals, Bernal and Astbury pushed on, and decided to probe proteins, common to all biological species. They split the potentially unending task into two: Astbury headed off to study fibrous proteins in his X-ray apparatus, while Bernal decided to explore globular proteins. Fedorov's dictum seemed to apply: protein diffraction was a messy affair, dominated by diffuse scattering rather than distinct sharp ‘Bragg’ spots. In contrast to the clean, characteristically ‘spotty’ diffraction patterns from highly crystalline minerals, biological matter was revealed to be less ordered, with a virtual continuum from discrete diffractions spots in the former, to diffuse structure in the latter, illustrated by the examples of figure 3.Figure 3.


Crystals: animal, vegetable or mineral?

Hyde ST - Interface Focus (2015)

X-ray diffraction patterns from a point source. (a) Zincblende (ZnS) crystal diffraction, recorded by P. Ewald; image from The Crystalline State by W.H. and W.L. Bragg; (b) cellulose fibres, oriented vertically [7]; (c) a lock of Mozart's hair, and (d) α-keratin diffraction pattern, from Mozart's hair (oriented obliquely) by William Astbury's colleague, Elwynn Beighton, in 1958.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4590423&req=5

RSFS20150027F3: X-ray diffraction patterns from a point source. (a) Zincblende (ZnS) crystal diffraction, recorded by P. Ewald; image from The Crystalline State by W.H. and W.L. Bragg; (b) cellulose fibres, oriented vertically [7]; (c) a lock of Mozart's hair, and (d) α-keratin diffraction pattern, from Mozart's hair (oriented obliquely) by William Astbury's colleague, Elwynn Beighton, in 1958.
Mentions: Diffraction relies on highly ordered, indeed crystalline (or quasi-crystalline) arrangements of scattering constituents, namely atoms or, via small-angle X-ray diffraction, molecules. (Here I use the term ‘diffraction’ in the conventional sense of wave interference producing discrete diffraction spots, in contrast to ‘scattering’, which gives diffuse intensity distributions in reciprocal space. Given recent developments with very high powered light sources such as X-ray free-electron lasers, this distinction is fading, with the advent of ‘nano diffraction’ techniques [6]). So the question of whether crystallography is helpful in understanding biological structures is worth asking. As the Russian theoretician of crystalline symmetries, Fedorov, said ‘Crystallisation is death’ [3]! In spite of the perceived gulf between animals and minerals, Bernal and Astbury pushed on, and decided to probe proteins, common to all biological species. They split the potentially unending task into two: Astbury headed off to study fibrous proteins in his X-ray apparatus, while Bernal decided to explore globular proteins. Fedorov's dictum seemed to apply: protein diffraction was a messy affair, dominated by diffuse scattering rather than distinct sharp ‘Bragg’ spots. In contrast to the clean, characteristically ‘spotty’ diffraction patterns from highly crystalline minerals, biological matter was revealed to be less ordered, with a virtual continuum from discrete diffractions spots in the former, to diffuse structure in the latter, illustrated by the examples of figure 3.Figure 3.

Bottom Line: The idea that there is a clear distinction between these two classes of matter has waxed and waned in popularity through past centuries.The older picture of disjoint universes of forms is better understood as a continuum of forms, with significant overlap and common features unifying biological and inorganic matter.In addition to the philosophical relevance of this perspective, there are important ramifications for science.

View Article: PubMed Central - PubMed

Affiliation: Department of Applied Mathematics, Research School of Physics and Engineering , The Australian National University , Canberra, Australian Capital Territory 0200 , Australia.

ABSTRACT
The morphologies of biological materials, from body shapes to membranes within cells, are typically curvaceous and flexible, in contrast to the angular, facetted shapes of inorganic matter. An alternative dichotomy has it that biomolecules typically assemble into aperiodic structures in vivo, in contrast to inorganic crystals. This paper explores the evolution of our understanding of structures across the spectrum of materials, from living to inanimate, driven by those naive beliefs, with particular focus on the development of crystallography in materials science and biology. The idea that there is a clear distinction between these two classes of matter has waxed and waned in popularity through past centuries. Our current understanding, driven largely by detailed exploration of biomolecular structures at the sub-cellular level initiated by Bernal and Astbury in the 1930s, and more recent explorations of sterile soft matter, makes it clear that this is a false dichotomy. For example, liquid crystals and other soft materials are common to both living and inanimate materials. The older picture of disjoint universes of forms is better understood as a continuum of forms, with significant overlap and common features unifying biological and inorganic matter. In addition to the philosophical relevance of this perspective, there are important ramifications for science. For example, the debates surrounding extra-terrestrial life, the oldest terrestrial fossils and consequent dating of the emergence of life on the Earth rests to some degree on prejudices inferred from the supposed dichotomy between life-forms and the rest.

No MeSH data available.


Related in: MedlinePlus