2004-01-16 19:21:00WuYung123
藻膽色素
Phycobiliproteins (藻膽色素)
(based on Glazer, 1987)
Phycobiliproteins made up of ab monomers of two dissimilar polypeptide chains, a and b, each with covalently attached bilin prosthetic groups. For a given pure phycobiliprotein, the aggregation stat depends on the organism from which the protein is isolated and the details of the purification procedure, as well as on the pH, ionic strength, composition of the solvent, protein concentration, and temperature. During purification procedures, certain phycobilisome polypeptide components are lost through retention on chromatographic supports, or, in some cases, destroyed by proteolysis. Since the linker polypeptides and the phycobiliproteins interact with each other with high specificity, it is to be anticipated that in many instances complete removal of the linker polypeptides from the phycobiliproeins will require extensive purification. The linker polypeptides have a profound influence on the aggregation state, assembly properties and spectroscopic characteristics of phycobiliproteins. Consequently, the presence of even small amount of these polypeptides can alter the properties of phycobiliprotein preparations. Given such complexities in the characterisation of hpycobiliprotein preparations, purity should not be assess purely on the vis abs spectrum and/or abs ratio of different peaks.
The bilin prosthetic groups consist of four isomeric tetrapyrroles function as the visible light harvesting chromophores of the phycobiliproteins. The spectroscopic properties of these tetrapyrroles are strongly influenced by their conformation and environment within the native phycobiliproteins. Phycocyanobilin gives rives to abs. Max above 600nm, e.g. 620 for CPC and 650 for trimeric APC. Biliporoteins containing phycobiliviolin (also named cryptoviolin) have abs max at 568nm, where as those containing phycoerythrobilin have abs. Max between 535 and 567nm. Phycourobilin-containing biliproteins show a sharp abs peak (or shoulder) at about 495nm.
(based on Glazer, 1987)
Phycobiliproteins made up of ab monomers of two dissimilar polypeptide chains, a and b, each with covalently attached bilin prosthetic groups. For a given pure phycobiliprotein, the aggregation stat depends on the organism from which the protein is isolated and the details of the purification procedure, as well as on the pH, ionic strength, composition of the solvent, protein concentration, and temperature. During purification procedures, certain phycobilisome polypeptide components are lost through retention on chromatographic supports, or, in some cases, destroyed by proteolysis. Since the linker polypeptides and the phycobiliproteins interact with each other with high specificity, it is to be anticipated that in many instances complete removal of the linker polypeptides from the phycobiliproeins will require extensive purification. The linker polypeptides have a profound influence on the aggregation state, assembly properties and spectroscopic characteristics of phycobiliproteins. Consequently, the presence of even small amount of these polypeptides can alter the properties of phycobiliprotein preparations. Given such complexities in the characterisation of hpycobiliprotein preparations, purity should not be assess purely on the vis abs spectrum and/or abs ratio of different peaks.
The bilin prosthetic groups consist of four isomeric tetrapyrroles function as the visible light harvesting chromophores of the phycobiliproteins. The spectroscopic properties of these tetrapyrroles are strongly influenced by their conformation and environment within the native phycobiliproteins. Phycocyanobilin gives rives to abs. Max above 600nm, e.g. 620 for CPC and 650 for trimeric APC. Biliporoteins containing phycobiliviolin (also named cryptoviolin) have abs max at 568nm, where as those containing phycoerythrobilin have abs. Max between 535 and 567nm. Phycourobilin-containing biliproteins show a sharp abs peak (or shoulder) at about 495nm.