Insights into Brønsted Acid Sites in the Zeolite Mordenite

The unique feature of the zeolite catalysts is the presence of catalytically active acidic hydroxyls, also known as Brønsted acid sites (BAS), in the zeolite micropores of molecular dimensions. The accessibility and catalytic properties of BAS depend on their local environment, and it is therefore important to know the exact locations of BAS and the number of BAS in these locations. This paper reports a detailed FT-IR investigation into BAS present in the acidic and partially Na-exchanged samples of industrially important mordenite (MOR) zeolite. Our results demonstrate the existence of (at least) six distinct BAS that can be visualized by six single bands in Fourier self-deconvolution traces of the IR spectra. The quantitative estimates for the amounts of these distinct BAS were obtained using the six-band deconvolution method developed in this work. These estimates show that in the purely acidic H-MOR sample about 25% of BAS are located in eight-membered ring (8-MR) channels (O1–H and O9–H hydroxyls), ∼13% of BAS are at the intersections between the side pockets and 12-MR channels (O5–H hydroxyls), and ∼62% of BAS are located in 12-MR channels (∼39% correspond to O2–H and/or O10–H hydroxyls and the remaining 23% to O3–H and O7–H hydroxyls). These quantitative data demonstrate that the acid sites are distributed quite evenly between oxygen atoms in different crystallographic positions, thus revealing the complexity of the experimental identification of distinct BAS in mordenites and explaining the variety of the earlier suggestions regarding their positions in these zeolites

Analytical “bake-off” of whole genome sequencing quality for the Genome Russia project using a small cohort for autoimmune hepatitis

<div><p>A comparative analysis of whole genome sequencing (WGS) and genotype calling was initiated for ten human genome samples sequenced by St. Petersburg State University Peterhof Sequencing Center and by three commercial sequencing centers outside of Russia. The sequence quality, efficiency of DNA variant and genotype calling were compared with each other and with DNA microarrays for each of ten study subjects. We assessed calling of SNPs, indels, copy number variation, and the speed of WGS throughput promised. Twenty separate QC analyses showed high similarities among the sequence quality and called genotypes. The ten genomes tested by the centers included eight American patients afflicted with autoimmune hepatitis (AIH), plus one case’s unaffected parents, in a prelude to discovering genetic influences in this rare disease of unknown etiology. The detailed internal replication and parallel analyses allowed the observation of two of eight AIH cases carrying a rare allele genotype for a previously described AIH-associated gene (<i>FTCD</i>), plus multiple occurrences of known <i>HLA-DRB1</i> alleles associated with AIH <i>(HLA-DRB1-03</i>:<i>01</i>:<i>01</i>, <i>13</i>:<i>01</i>:<i>01 and 7</i>:<i>01</i>:<i>01</i>). We also list putative SNVs in other genes as suggestive in AIH influence.</p></div

<i>HLA-DRB1</i> and <i>FTCD</i> genotypes.

<p><i>HLA-DRB1</i> and <i>FTCD</i> genotypes.</p

Sample description.

<p>Sample description.</p

Raw read quality control parameters.

<p>Raw sequence read QC parameters are shown for three sequencing centers (colored differently).</p

Genotype comparison.

<p>(A) Concordance of WGS genotypes with microarray genotypes. The concordance was estimated based on the trio data as the ratio of microarray SNPs with identical genotypes in WGS results. (B) Comparison of the three WGS datasets between each other in terms of precision, sensitivity and F-measure for pairwise comparisons. Color legend is given on the top right. (C) Concordance of genotypes in the three WGS datasets for all variants, SNPs and indels. Color legend is given on the top right.</p

Comparison of sequencing results (N = 17 parameters).

<p>Comparison of sequencing results (N = 17 parameters).</p