Abstract
The interaction of a water-soluble cationic porphyrin, Cobalt(III) 5, 10, 15, 20-tetrakis (1-methylpyridinium-4-yl) porphyrin [Co(III)TMPyP], with bovine serum albumin (BSA) has been studied in 1 mM phosphate buffer pH 7.0 containing 5 mM NaCl by UV-vis absorption, resonance light scattering (RLS) and fluorescence spectroscopies at 25°C. The results of RLS studies represent no aggregate formation of porphyrin in the surface of BSA and low tendency of this porphyrin for aggregate formation.The binding of porphyrin complex to BSA quenches fluorescence emission of BSA via a dynamic mechanism and the quenching process obeys a linear Stern-Volmer relationship. The values of Stern-Volmer constants, KSV, was determined nearly 105M−1, that depend on BSA concentration. The average aggregation number of BSA calculated from the analysis of fluorescence quenching data indicates that absence of any porphyrin induced aggregation of BSA due to its interaction with porphyrin complex. The binding of Co(III) TMPyP had no obvious effect on the molecular conformation of the protein. Electrostatic force played an important role in the binding due to the opposite charges on porphyrin and the protein.
Highlights
The research on water-soluble porphyrins has received much interest in recent years [1,2,3,4,5,6]
We have reported the interaction of water-soluble cationic porphyrin Co(III)TMPyP with bovine serum albumin (BSA) a typical globular protein, using absorption, fluorescence and resonance light scattering (RLS) spectroscopy
Fluorescence spectroscopy was used to monitor perturbation in the tertiary structure of BSA induced by porphyrin binding
Summary
The research on water-soluble porphyrins has received much interest in recent years [1,2,3,4,5,6]. Because of their excellent bioactivity water-soluble cationic porphyrins can be used as potential anticancer [7, 8], antibacterial agents [9, 10] and probe for structure and dynamics of DNA [11]. Serum albumin is the natural carrier protein for photosensitizers such as porphyrin [12] and performs a key role in the transport of drugs such as porphyrins in vivo [13]. The binding interaction between porphyrin and protein with one or several binding sites can affect the transportation and metabolism of porphyrin [14]. The binding of porphyrin on protein will change the molecular conformation affecting the physiological function of the protein [14]
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