8 Analytical Protocols in Phycobiliproteins Analysis
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8.5 Evaluation of Biological Activities of PBPs
The exceptional redox and metal-chelating properties of PBPs, and especially their
chromophores, are proved by various biochemical assays for determination of their
antioxidant potential: oxygen radical absorbance capacity (ORAC), total radicaltrapping antioxidant parameter (TRAP), β-carotene or crocin bleaching, ferric ion
reducing antioxidant power (FRAP), lipid peroxidation inhibition, thiobarbituric
acid reactive substances (TBARS), Fe
2+ ions chelating, copper ion reducing antioxidant capacity (CUPRAC), 1,1-diphenyl-2-picrylhydrazyl (DPPH) or 2,2
-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) radical scavenging, hydroxyl radical
absorbance capacity (HORAC), etc. (reviewed in Kenny et al. 2015).
An increasing number of studies, performed in different in vivo and in vitro model
systems, show that purified PBPs, PBSs-enriched extracts, recombinant, and even
encapsulated PBSs, as well as their chromophores, exhibit a plethora of biological
activities with substantial health benefits (summarized in Table 8.1). In vivo, in
rat, mouse, and hamster models with induced disorders, PBPs were tested for their
anti-cancer, anti-inflammatory, neuroprotective, nephroprotective, hepatoprotective,
antihyperlipidemic, and antioxidative effects, while in Caenorhabditis elegans PC‘s
anti-aging action was examined. In vitro, in healthy cells, such as human erythrocytes
and rat cardiomyocytes, PBPs were examined for their protective antioxidant effects
during induced oxidative stress. In cancer cell lines, anti-cancer activity of PBPs was
investigated mainly by testing cell viability, cycle, and apoptosis, while mechanisms
of PBS’s anti-cancer action were examined by monitoring of mRNA and protein
expression of genes and signaling pathways involved in cell death. Photodynamic
cytotoxicity on cancer cell lines was tested upon PBPs treatment followed by laser
irradiation (Table 8.1).
8.6 PBPs Interactions with Other Biomolecules and Ions
Although PBPs and their chromophores are prone to interact (non)covalently with
other molecules and ions, there is limited literature data related to this topic. In
the majority of the studies, fluorescent properties of PC and PCB are exploited for
the determination of their noncovalent interactions and the most frequently used
method is fluorescence quenching. In several studies, fluorescence quenching of a
chromophore was monitored upon its titration with tested molecule or ion. The interactions of PCB with proteins were also followed by fluorescence quenching of protein
Trp residue(s) upon titration with PCB. Gelagutashvili et al. (2013) compared three
methods for monitoring of heavy metal binding to PC: equilibrium dialysis, fluorescence, and absorption titration. Heavy metal binding to PC was even exploited for the
creation of fluorescence chemosensor for Cu
2+ and mercapto biomolecules (Puangploy et al. 2015). Fluorescence quenching was used for monitoring of PC interactions
185
8.5 Evaluation of Biological Activities of PBPs
The exceptional redox and metal-chelating properties of PBPs, and especially their
chromophores, are proved by various biochemical assays for determination of their
antioxidant potential: oxygen radical absorbance capacity (ORAC), total radicaltrapping antioxidant parameter (TRAP), β-carotene or crocin bleaching, ferric ion
reducing antioxidant power (FRAP), lipid peroxidation inhibition, thiobarbituric
acid reactive substances (TBARS), Fe
2+ ions chelating, copper ion reducing antioxidant capacity (CUPRAC), 1,1-diphenyl-2-picrylhydrazyl (DPPH) or 2,2
-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) radical scavenging, hydroxyl radical
absorbance capacity (HORAC), etc. (reviewed in Kenny et al. 2015).
An increasing number of studies, performed in different in vivo and in vitro model
systems, show that purified PBPs, PBSs-enriched extracts, recombinant, and even
encapsulated PBSs, as well as their chromophores, exhibit a plethora of biological
activities with substantial health benefits (summarized in Table 8.1). In vivo, in
rat, mouse, and hamster models with induced disorders, PBPs were tested for their
anti-cancer, anti-inflammatory, neuroprotective, nephroprotective, hepatoprotective,
antihyperlipidemic, and antioxidative effects, while in Caenorhabditis elegans PC‘s
anti-aging action was examined. In vitro, in healthy cells, such as human erythrocytes
and rat cardiomyocytes, PBPs were examined for their protective antioxidant effects
during induced oxidative stress. In cancer cell lines, anti-cancer activity of PBPs was
investigated mainly by testing cell viability, cycle, and apoptosis, while mechanisms
of PBS’s anti-cancer action were examined by monitoring of mRNA and protein
expression of genes and signaling pathways involved in cell death. Photodynamic
cytotoxicity on cancer cell lines was tested upon PBPs treatment followed by laser
irradiation (Table 8.1).
8.6 PBPs Interactions with Other Biomolecules and Ions
Although PBPs and their chromophores are prone to interact (non)covalently with
other molecules and ions, there is limited literature data related to this topic. In
the majority of the studies, fluorescent properties of PC and PCB are exploited for
the determination of their noncovalent interactions and the most frequently used
method is fluorescence quenching. In several studies, fluorescence quenching of a
chromophore was monitored upon its titration with tested molecule or ion. The interactions of PCB with proteins were also followed by fluorescence quenching of protein
Trp residue(s) upon titration with PCB. Gelagutashvili et al. (2013) compared three
methods for monitoring of heavy metal binding to PC: equilibrium dialysis, fluorescence, and absorption titration. Heavy metal binding to PC was even exploited for the
creation of fluorescence chemosensor for Cu
2+ and mercapto biomolecules (Puangploy et al. 2015). Fluorescence quenching was used for monitoring of PC interactions