Dispersion-corrected energy barriers for silylene addition to white phosphorus, a density functional investigation into substituent effects

Schoeller W. Dispersion-corrected energy barriers for silylene addition to white phosphorus, a density functional investigation into substituent effects. THEORETICAL CHEMISTRY ACCOUNTS. 2010;127(3):223-229.A density functional investigation into differently substituted silylenes with respect to the first step in the addition to white phosphorus is presented. The investigations include dispersion corrections in the density functional treatment. They become sizable for the transition state geometries for the silylenes as they become increasingly substituted by bulky groups. Hence, dispersion corrections are essential for a quantum chemical treatment of real molecules using density functional theory. The different singlet-triplet energy separations of differently substituted silylenes were also investigated and compared with calculated activation barriers for the first step in the addition reaction

Human-specific protein isoforms produced by novel splice sites in the human genome after the human-chimpanzee divergence

<p>Abstract</p> <p>Background</p> <p>Evolution of splice sites is a well-known phenomenon that results in transcript diversity during human evolution. Many novel splice sites are derived from repetitive elements and may not contribute to protein products. Here, we analyzed annotated human protein-coding exons and identified human-specific splice sites that arose after the human-chimpanzee divergence.</p> <p>Results</p> <p>We analyzed multiple alignments of the annotated human protein-coding exons and their respective orthologous mammalian genome sequences to identify 85 novel splice sites (50 splice acceptors and 35 donors) in the human genome. The novel protein-coding exons, which are expressed either constitutively or alternatively, produce novel protein isoforms by insertion, deletion, or frameshift. We found three cases in which the human-specific isoform conferred novel molecular function in the human cells: the human-specific IMUP protein isoform induces apoptosis of the trophoblast and is implicated in pre-eclampsia; the intronization of a part of <it>SMOX</it> gene exon produces inactive spermine oxidase; the human-specific NUB1 isoform shows reduced interaction with ubiquitin-like proteins, possibly affecting ubiquitin pathways.</p> <p>Conclusions</p> <p>Although the generation of novel protein isoforms does not equate to adaptive evolution, we propose that these cases are useful candidates for a molecular functional study to identify proteomic changes that might bring about novel phenotypes during human evolution.</p