Preferred provider organization
A preferred provider organization is a subscription-based medical care arrangement. A membership allows a substantial discount below the regularly charged rates of the designated professionals partnered with the organization. Preferred provider organizations themselves earn money by charging an access fee to the insurance company for the use of their network (unlike the usual insurance with premiums and corresponding payments paid either in full or partially by the insurance provider to the medical doctor). They negotiate with providers to set fee schedules, and handle disputes between insurers and providers. PPOs can also contract with one another to strengthen their position in certain geographic areas without forming new relationships directly with providers. This will be mutually beneficial in theory, as be billed at a reduced rate when its insureds utilize the services of the "preferred" provider and the provider will see an increase in its business as almost all insureds in the organization will use only providers who are members. PPOs have gained popularity because, although they tend to have slightly higher premiums than HMOs and other more restrictive plans, they offer patients more flexibility overall.
Eosinophil peroxidase
The protein contains only a single modular domain. In this respect it is primarily a metabolic enzyme or terminal effector; it has little role in cellular signalling pathways. The overall structure of the four mammalian heme peroxidases (MPO, LPO, EPO and TPO) is almost identical. However, MPO is unique in existing as a catalytic dimer bridged by a disulphide bond. One of the first aspects known of eosinophil peroxidase was that it was highly cationic, as indicated by its high isoelectric point (see Protein). Eosinophil peroxidase has not been characterized by X-ray crystallography. However, a direct correspondence between the absorption spectra of EPO, TPO and LPO as well as high sequence similarity allows us to compare the properties of the three. Myeloperoxidase's characteristics are somewhat different, owing to its multimerization state as well as its alternative heme linkage. Further, a homology model has been created for EPO based on the X-ray diffraction structure.