Structure and luminescence properties of some new AgLnW(2)O(8) compounds

Three new compounds, AgLnW(2)O(8) (Ln(3+)=Eu, Gd or Tb), have been prepared by a solid-state reaction and crystallize with a scheelite-related monoclinic symmetry. Their IR spectra show absorption transitions in the region 1000-400 cm(-1) similar to KLnW(2)O(8). Broad excitation and emission bands of the tungstate group with a large Stokes shift (12573 cm(-1)) are observed in AgGdW2O8. Excitation and emission spectra of AgLnW(2)O(8) (Ln=Eu or Tb) show that energy transfer from tungstate to Eu and Tb occurs and that Eu3+ ions occupy a unique crystallographic site with C-2 site symmetry.

Spectroscopic properties of the C-phycocyanin-allophycocyanin conjugate and the isolated phycobilisomes from Spirulina platensis

C-phycocyanin (CPC) and allophycocyanin (APC) were purified from Spirulina platensis, then the CPC was attached covalently to the APC by reacting their epsilon-amino groups. The excitation energy could be transferred from the CPC to the APC in the CPC-APC conjugate. Intact phycobilisomes (PBS), consisting of CPC, APC, colourless linker polypeptides, and APC B or L-cm, were isolated from S. platensis. Spectroscopic properties of the isolated PBSs kept at 20 degrees C for various times showed that the connection between the APC and the APC B or L-cm was looser than that between the CPC and the APC in the isolated PBSs. The CPC-APC conjugate was more stable than the isolated PBSs, and the linker polypeptides had a minor influence on the excitation energy transfer characteristic between different phycobiliproteins in the PBS.