Spectroscopic studies on the interaction of a water-soluble cationic porphyrin with proteins.
The interaction of a water-soluble cationic porphyrin, meso-tetrakis (4-N,N,N-trimethylanilinium) porphyrin (TMAP), with two proteins, bovine serum albumin (BSA) and human serum albumin (HSA), was studied by UV-vis absorption spectroscopy, fluorescence spectroscopy, fluorescence anisotropy and synchronous fluorescence spectroscopy at neutral aqueous solutions. Free base TMAP bound to proteins as monomers and no aggregation was observed. The binding of TMAP quenched the fluorescence of the protein. On the contrary, the fluorescence of TMAP was enhanced and the fluorescence anisotropy increased due to the binding. The direct static binding mechanism could account for the quenching by TMAP and the binding constants were calculated. TMAP showed a higher quenching efficiency and binding constant of HSA than BSA. The binding of TMAP had no obvious effect on the molecular conformation of the protein. There was only one binding site for TMAP and it was located on the surface of the protein molecule. Electrostatic force played an important role in the binding due to the opposite charges on porphyrin and the proteins.
Ma
Hong-Min
HM
School of Chemistry and Chemical Engineering, University of Jinan, No. 106 Jiwei Road, Jinan 250022, PR China.
Chen
Xin
X
Zhang
Nuo
N
Han
Yan-Yan
YY
Wu
Dan
D
Du
Bin
B
Wei
Qin
Q
D000818:Animals; D001665:Binding Sites; D002412:Cations / Q000737:chemistry; D002417:Cattle; D005454:Fluorescence Polarization; D006801:Humans; D006863:Hydrogen-Ion Concentration; D011166:Porphyrins / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D012709:Serum Albumin / Q000378:metabolism*; D012710:Serum Albumin, Bovine / Q000378:metabolism*; D012995:Solubility; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet; D013057:Spectrum Analysis / Q000379:methods*; D055672:Static Electricity; D014867:Water / Q000737:chemistry*
D002412:Cations; D011166:Porphyrins; D012709:Serum Albumin; C539451:meso-tetrakis (4-N,N,N-trimethylanilinium) porphyrin; D014867:Water; D012710:Serum Albumin, Bovine