Colour-changing pigments

Whilst this definition is academically accurate for many inorganic and organic materials, the label thermochromic has also been applied to important technical areas that involve other external influences as well as heat in the observed colour change, e.g. thermochromic pigments. 

Cholesteric LCs can act as hosts for dyes to produce coloured displays (see section 5.2.2.1 below) " their temperature dependent colour change has found applications in thermochromic inks, °" and as pigments and copy safe colours their selective reflecting capabilities have been applied in colours and filters for reflective displays and projection systems, " reflective polarisers and their electrical field induced switching in displays and smart reflectors, in colour patterning for full-colour recording. ... 

Liao, FI., Cai, Y., and Haslam, E., Polyphenol interactions. Anthocyanins co-pigmentation and colour changes in red wines. J. Sci. Food Agric. 59, 299, 1992. 

R. Akashi, H. Tsutsui and A. Komura, Polymer Gel Light-Modulation Materials Imitating Pigment Cells, Advanced Materials, 14, 1808-1811 (2002) as described by P. Ball, Nature Inspires Colour Change Gel, Nature Materials Update, January 8, 2003. 

Eagerman et al. (1978) have followed the colour change with time in beef semimembranous muscle. Approximately 1 cm thick slices were plaeed against the port of a speetrocolorimeter and the reflectance spectra measured between 600 and 650 mn. The formation of a depression in the region of the speetral curve around 632 nm is an indieator of brown metmyoglobin pigment produetion. 

After treatment, within 48 hours, there is a cessation of growth. Nodes and buds become necrotic. Young leaves show chlorosis, then necrosis, followed by older leaves which show pigment colour changes (anthocyanin formation). Death of the weeds usually occurs after three weeks. 

RPCH is not known to have any true metabolic effect in crustaceans, however, RPCH can (of course) elicit most of the actions of the insect AKHs in the appropriate insect recipient. Likewise, insect AKHs are potent to concentrate pigments in the appropriate crustacean species but to date, no report has shown that AKH can effect a colour change in insects. 

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