Structure of the mixed-metal carbonate KAgCO3 revisited: order-disorder (OD) polytypism and allotwinning
ACTA CRYSTALLOGRAPHICA SECTION B-STRUCTURAL SCIENCE CRYSTAL ENGINEERING AND MATERIALS
Authors: Hans, Philipp; Stoeger, Berthold; Weil, Matthias; Zobetz, Erich
Abstract
Crystals of KAgCO3 belong to an order-disorder (OD) family of structures composed of layers of two kinds. There are two polytypes with a maximum degree of order [MDO1: Pccb; MDO2 : Ibca, doubled a-axis compared with MDO1], which are both realised to a different extent in two crystals under investigation [volume fraction MDO1: MDO2 in crystal (I): 0.0216:0.9784 (3) and in crystal (II): 0.9657:0.0343 (3)]. Sharp diffraction spots and the absence of diffuse scattering indicate highly ordered macroscopic domains. The structure of KAgCO3 was refined concurrently against all reflections using an allotwin model (addition of the intensities of both domains). It is shown that a disorder model refined against reflections of only one domain can lead to a significant overestimation of the volume fraction of this domain.
Propionic acidemia: identification of twenty-four novel mutations in Europe and North America
MOLECULAR GENETICS AND METABOLISM
Authors: Perez, B; Desviat, LR; Rodriguez-Pombo, P; Clavero, S; Navarrete, R; Perez-Cerda, C; Ugarte, M
Abstract
Propionic acidemia is an inherited metabolic disease caused by the deficiency of the mitochondrial protein propionyl-CoA carboxylase (PCC), one of the four biotin-dependent enzymes. PCC is a multimeric protein composed of two different alpha- and beta-PCC subunits, nuclearly encoded by the PCCA and PCCB genes, respectively. Mutations in either gene cause the clinically heterogeneous disease propionic acidemia. In this work we describe the mutational analysis of PCCA and PCCB deficient patients from different European countries (Spain, Italy, Belgium, Croatia, and Austria) and from America (mainly USA). We report 24 novel PA mutations, nine affecting the PCCA gene and 15 affecting the PCCB gene. They include six missense mutations, one nonsense mutation, one point exonic mutation affecting splicing, seven splicing mutations affecting splice sequences, and nine short insertions or deletions, only two in-frame. We have found a highly heterogenous spectrum of PCCA mutations, most of the PCCA deficient patients are homozygous carrying a unique genotype. The PCCA mutational spectrum includes a high proportion of short insertions or deletions affecting one nucleotide. In the PCCA mutant alleles analyzed we have also found one single nucleotide change, a novel nonsynonymous SNP. On the other hand, the PCCB deficient patients carry a more reduced spectrum of mutations, 50% of them are missense. This work represents an extensive update of the mutational study of propionic acidemia providing important information about the worldwide distribution of PA mutations and representing another essential part in the study of the phenotype-genotype correlations for the prediction of the metabolic outcome and for the implementation of treatments tailored to each PA patient. (C) 2002 Elsevier Science (USA). All rights reserved.