638
B. de Souza Fonseca et al.
26.2.1 Phycobilins
Phycobilins correspond to the pigments present in the Rhodophyta, Cyanophyta,
and Cryptophyta divisions (Sampaio and Cruz 2014). They are water-soluble and
are characterized by compounds with two units: alpha and beta (Andrade and Filho
2014). The main role of phycobilins is to assist in capturing solar energy in regions
of the spectrum that chlorophyll has low absorption content. Thus, phycobilins can
capture light even in low light conditions, as in deep ocean regions.
Therefore, the presence of chlorophyll is masked, that is, the energy captured by
phycobilins is transferred to chlorophylls and provides bluish or reddish colorations
to algae. Thus, phycobilins increase the spectrum of light uptake by photosynthesis.
Also, as one of its main functions, phycobilins act as repositories for hydrogen
reserves.
The main contexts of use of phycobilins are as fluorescent reactive agents in
medical and scientific research, since the pigment absorbs part of the light (when
exposed to a bright light) and reflects another part. This reflection makes it possible
to trace elements and cells marked with the pigment.
Phycobilins also act as dyes in foods and cosmetic substances (Vargas-Rodriguez
et al. 2006). In addition, they have applications in antioxidant, anti-inflammatory,
antiviral activities, (Sampaio and Cruz 2014) and even in antitumor contexts, although
research in this latter context is still scarce (Schmitz et al. 2012).
The phycobiliproteins are constituted by a protein part covalently attached to chromophores called bilins (prosthetic group) (Glazer 1981). They form a highly ordered
complex called phycobilisomes, as shown in Fig. 26.1, located on the thylakoid
membrane. The phycobilisomes are composed of two domains: nucleus and stems.
The former is bound to the thylakoid membrane and composed of phycobiliprotein
allophycocyanin. The second is associated with the nucleus, and is composed of
hexameric arrangements of phycoerythrin and phycocyanin.
Fig. 26.1 Structure of a phycobilisome (Esteves 2016)
B. de Souza Fonseca et al.
26.2.1 Phycobilins
Phycobilins correspond to the pigments present in the Rhodophyta, Cyanophyta,
and Cryptophyta divisions (Sampaio and Cruz 2014). They are water-soluble and
are characterized by compounds with two units: alpha and beta (Andrade and Filho
2014). The main role of phycobilins is to assist in capturing solar energy in regions
of the spectrum that chlorophyll has low absorption content. Thus, phycobilins can
capture light even in low light conditions, as in deep ocean regions.
Therefore, the presence of chlorophyll is masked, that is, the energy captured by
phycobilins is transferred to chlorophylls and provides bluish or reddish colorations
to algae. Thus, phycobilins increase the spectrum of light uptake by photosynthesis.
Also, as one of its main functions, phycobilins act as repositories for hydrogen
reserves.
The main contexts of use of phycobilins are as fluorescent reactive agents in
medical and scientific research, since the pigment absorbs part of the light (when
exposed to a bright light) and reflects another part. This reflection makes it possible
to trace elements and cells marked with the pigment.
Phycobilins also act as dyes in foods and cosmetic substances (Vargas-Rodriguez
et al. 2006). In addition, they have applications in antioxidant, anti-inflammatory,
antiviral activities, (Sampaio and Cruz 2014) and even in antitumor contexts, although
research in this latter context is still scarce (Schmitz et al. 2012).
The phycobiliproteins are constituted by a protein part covalently attached to chromophores called bilins (prosthetic group) (Glazer 1981). They form a highly ordered
complex called phycobilisomes, as shown in Fig. 26.1, located on the thylakoid
membrane. The phycobilisomes are composed of two domains: nucleus and stems.
The former is bound to the thylakoid membrane and composed of phycobiliprotein
allophycocyanin. The second is associated with the nucleus, and is composed of
hexameric arrangements of phycoerythrin and phycocyanin.
Fig. 26.1 Structure of a phycobilisome (Esteves 2016)