title: Structural Basis for Polymer Packing and Solvation Properties of the Organogermanium Crystalline Polymer Propagermanium and Its Derivatives.
abstract: Of organogermanium compounds known to have an immunostimulatory action, propagermanium [PGe; 3-oxygermylpropionic acid polymer, (C3 H5 GeO3.5 )n] is the only one used as a pharmaceutical agent, to treat the hepatitis B virus in Japan. However, because of lack of information about its structure, PGe has been confused with a polymeric solid, repagermanium (RGe, Ge-132, poly-trans-[(2-carboxyethyl) germasesquioxane], (C18 H30 Ge6 O21 )n), which has the same essential formula as PGe. To clarify this issue, the structure of PGe was analyzed using X-ray diffraction (XRD). PGe has a polymeric ladder-shaped structure of a concatenated eight-membered ring composed of Ge-O bonds, which is clearly distinguished from the infinite sheet structure in RGe. Moreover, we observed temperature or moisture-dependent transformations among these compounds using powder XRD. For instance, PGe was easily dissolved in water, and transformed to RGe by exposure to water vapor, but transformed into another straight-chain structure when exposed to aqueous solution. As a result of these findings, PGe was indicated to have labile polymer packing against RGe. These characteristics of PGe may affect pharmaceutical properties such as respective stability and solubility, which indicate its unique impact on physiological activity.
authors.affiliation: Protein Crystal Analysis Division, Japan Synchrotron Radiation Research Institute, Sayo-gun, Hyogo, Japan.
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Mizuno
authors.affiliation: Division of Physics, Faculty of Pure and Applied Sciences, Tsukuba Research Center for Interdisciplinary Materials Science (TIMS) and Center for Integrated Research in Fundamental Science and Engineering (CiRfSE), University of Tsukuba, Tsukuba, Ibaraki, Japan.
authors.forename: Eiji
authors.initials: E
authors.lastname: Nishibori
authors.affiliation: Pharmaceutical Technology Laboratories, Sanwa Kagaku Kenkyusho Company, Ltd., Inabe, Mie, Jpaan.
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Oka
authors.affiliation: Drug Development Center, Sanwa Kagaku Kenkyusho Company, Ltd., Nagoya Aichi, Japan.
authors.forename: Takahito
authors.initials: T
authors.lastname: Jomori
authors.affiliation: Structural Materials Science Laboratory, RIKEN SPring-8 Center, Sayo-gun, Hyogo, Japan.|Research and Utilization Division, Japan Synchrotron Radiation Research Institute, Sayo-gun, Hyogo, Japan.
authors.forename: Masaki
authors.initials: M
authors.lastname: Takata
authors.affiliation: Protein Crystal Analysis Division, Japan Synchrotron Radiation Research Institute, Sayo-gun, Hyogo, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Kumasaka
mesh_terms: D000970:Antineoplastic Agents / Q000737:chemistry*; D011232:Chemical Precipitation; D018360:Crystallography, X-Ray; D004355:Drug Stability; D005857:Germanium / Q000737:chemistry; D006358:Hot Temperature; D007369:Interferon Inducers / Q000737:chemistry*; D007536:Isomerism; D008958:Models, Molecular; D008968:Molecular Conformation; D015394:Molecular Structure; D008970:Molecular Weight; D009942:Organometallic Compounds / Q000737:chemistry*; D058105:Polymerization; D033362:Powder Diffraction; D011422:Propionates; D012995:Solubility; D014867:Water / Q000032:analysis / Q000737:chemistry
chemical_list: D000970:Antineoplastic Agents; D007369:Interferon Inducers; D009942:Organometallic Compounds; D011422:Propionates; D005857:Germanium; D014867:Water; C066750:propagermanium
keywords: X-ray powder diffractometry; crystal structure; crystallography; solvation; stability