Remote dipole effects as a means to accelerate [Ru(amino alcohol)]-catalyzed transfer hydrogenation of ketones

A new generation of 2-aza-norbornyl amino alcohol ligands for the catalytic transfer hydrogenation reaction of aromatic ketones was synthesized. Extremely active catalysts were formed by introducing a ketal functionality at the rear end of the ligand. Acetophenone was reduced in 96% ee at low catalyst loading, substrate to catalyst ratio, S/C 5000, within 90 minutes with isopropyl alcohol as the hydrogen donor. It was found that the dioxolane substituent in the ligand increased the turnover frequency, TOF50, from 1050 h(-1) to 3000 h(-1) at an S/C ratio of 1000. Introduction of a methyl group at the carbinol carbon resulted in TOF50 as high as 8500 h(-1). Transfer hydrogenation of a range of aromatic ketones was evaluated and found to reach completion within 30 minutes at room temperature, and excellent enantioselectivity, up to 99 % ee, was obtained. A possible explanation for the enhanced activity was provided by density functional calculations, which showed that the presence of a remote dipole in the ligand lowered the transition state energy.

Sequence and analysis of chromosome 3 of the plant Arabidopsis thaliana

Arabidopsis thaliana is an important model system for plant biologists. In 1996 an international collaboration (the Arabidopsis Genome Initiative) was formed to sequence the whole genome of Arabidopsis and in 1999 the sequence of the first two chromosomes was reported. The sequence of the last three chromosomes and an analysis of the whole genome are reported in this issue. Here we present the sequence of chromosome 3, organized into four sequence segments (contigs). The two largest (13.5 and 9.2 Mb) correspond to the top (long) and the bottom (short) arms of chromosome 3, and the two small contigs are located in the genetically defined centromere. This chromosome encodes 5,220 of the roughly 25,500 predicted protein-coding genes in the genome. About 20% of the predicted proteins have significant homology to proteins in eukaryotic genomes for which the complete sequence is available, pointing to important conserved cellular functions among eukaryotes.

Identification of an L-dopa decarboxylase gene from Sorangium cellulosum So ce90

During a screening program intended to identify genes encoding enzymes typical for secondary metabolism in Sorangium cellulosum So ce90, an aromatic amino acid decarboxylase gene (ddc) was detected. Expression of ddc in Escherichia coli and subsequent enzyme assays with cell-free extracts confirmed the proposed function derived from amino acid sequence comparisons. In contrast to other aromatic amino acid decarboxylases of eukaryotic origin, the S. cellulosum Ddc converted only L-dihydroxy phenylalanine. This is the first report of a gene encoding an L-dihydroxy phenylalanine decarboxylase in bacteria.

Progress in Arabidopsis genome sequencing and functional genomics

Arabidopsis thaliana has a relatively small genome of approximately 130 Mb containing about 10% repetitive DNA. Genome sequencing studies reveal a gene-rich genome, predicted to contain approximately 25000 genes spaced on average every 4.5 kb. Between 10 to 20% of the predicted genes occur as clusters of related genes, indicating that local sequence duplication and subsequent divergence generates a significant proportion of gene families. In addition to gene families, repetitive sequences comprise individual and small clusters of two to three retroelements and other classes of smaller repeats. The clustering of highly repetitive elements is a striking feature of the A. thaliana genome emerging from sequence and other analyses.

New lessons for combinatorial biosynthesis from myxobacteria. The myxothiazol biosynthetic gene cluster of Stigmatella aurantiaca DW4/3-1

The biosynthetic mta gene cluster responsible for myxothiazol formation from the fruiting body forming myxobacterium Stigmatella aurantiaca DW4/3-1 was sequenced and analyzed. Myxothiazol, an inhibitor of the electron transport via the bc(1)-complex of the respiratory chain, is biosynthesized by a unique combination of several polyketide synthases (PKS) and nonribosomal peptide synthetases (NRPS), which are activated by the 4'-phosphopantetheinyl transferase MtaA. Genomic replacement of a fragment of mtaB and insertion of a kanamycin resistance gene into mtaA both impaired myxothiazol synthesis. Genes mtaC and mtaD encode the enzymes for bis-thiazol(ine) formation and chain extension on one pure NRPS (MtaC) and on a unique combination of PKS and NRPS (MtaD). The genes mtaE and mtaF encode PKSs including peptide fragments with homology to methyltransferases. These methyltransferase modules are assumed to be necessary for the formation of the proposed methoxy- and beta-methoxy-acrylate intermediates of myxothiazol biosynthesis. The last gene of the cluster, mtaG, again resembles a NRPS and provides insight into the mechanism of the formation of the terminal amide of myxothiazol. The carbon backbone of an amino acid added to the myxothiazol-acid is assumed to be removed via an unprecedented module with homology to monooxygenases within MtaG.

Sequence and analysis of chromosome 4 of the plant Arabidopsis thaliana

The higher plant Arabidopsis thaliana (Arabidopsis) is an important model for identifying plant genes and determining their function. To assist biological investigations and to define chromosome structure, a coordinated effort to sequence the Arabidopsis genome was initiated in late 1996. Here we report one of the first milestones of this project, the sequence of chromosome 4. Analysis of 17.38 megabases of unique sequence, representing about 17% of the genome, reveals 3,744 protein coding genes, 81 transfer RNAs and numerous repeat elements. Heterochromatic regions surrounding the putative centromere, which has not yet been completely sequenced, are characterized by an increased frequency of a variety of repeats, new repeats, reduced recombination, lowered gene density and lowered gene expression. Roughly 60% of the predicted protein-coding genes have been functionally characterized on the basis of their homology to known genes. Many genes encode predicted proteins that are homologous to human and Caenorhabditis elegans proteins.

Childhood diabetes: behavioral research

The major emphasis of behavioral research related to childhood diabetes has been on the child's physical and emotional outcomes, the family's response, and adherence issues. This research review focuses on adherence and related youth and family functioning. Descriptive and intervention studies are critiqued. Common conceptual and methodological issues are discussed with recommendations for future research.

The complete nucleotide sequence of the egg drop syndrome virus: an intermediate between mastadenoviruses and aviadenoviruses

The complete nucleotide sequence of an avian adenovirus, the egg drop syndrome (EDS) virus, was determined. The total genome length is 33,213 nucleotides, resulting in a molecular weight of 21.9 x 10(6). The GC content is only 42.5%. Between map units 3.5 and 76.9, the distribution of open reading frames with homology to known genes is similar to that reported for other mammalian and avian adenoviruses. However, no homologies to adenovirus genes such as E1A, pIX, pV, and E3 could be found. Outside this region, several open reading frames were identified without any obvious homology to known adenovirus proteins. In the region organized similarly as other adenoviral genomes, most homologies were found to an ovine adenovirus (OAV strain 287). The highest level of amino acid identity was found for the hexon proteins of EDS and OAV. The virus-associated RNA (VA RNA) was identified thanks to the homology with the VA RNA of fowl adenovirus serotype 1 (FAV1). Similarities with FAV1 were also found in the fiber protein. Our results demonstrate that the avian EDS virus represents an intermediate between mammalian and avian adenoviruses. The nucleotide sequence and genomic organization of the EDS virus reflect the heterogeneity of the aviadenovirus genus and the Adenoviridae family.

Mosaic open reading frames in the Arabidopsis thaliana mitochondrial genome

In the mitochondrial genome of Arabidopsis thaliana eight mosaic open reading frames arose by recombination of fragments duplicated from one or more mitochondrial genes. These duplications represent unedited sequences, suggesting their derivation from genomic DNA rather than RNA. Five of the chimeric reading frames contain the information for the N-terminus of the original polypeptide and 5' upstream regions. These observations suggest that the generation of novel open reading frames in plant mitochondria can occur rather easily by chance extensions of duplicated gene fragments. The presence of so many mosaic open reading frames in the normal Arabidopsis thaliana mitochondrial genome suggests that such recombined sequences interfere only occasionally and fortuitously with the peak mitochondrial performance presumably required during pollen maturation, and usually do not cause a cytoplasmic male sterile phenotype.

The nucleotide sequence of Saccharomyces cerevisiae chromosome IV

The complete DNA sequence of the yeast Saccharomyces cerevisiae chromosome IV has been determined. Apart from chromosome XII, which contains the 1-2 Mb rDNA cluster, chromosome IV is the longest S. cerevisiae chromosome. It was split into three parts, which were sequenced by a consortium from the European Community, the Sanger Centre, and groups from St Louis and Stanford in the United States. The sequence of 1,531,974 base pairs contains 796 predicted or known genes, 318 (39.9%) of which have been previously identified. Of the 478 new genes, 225 (28.3%) are homologous to previously identified genes and 253 (32%) have unknown functions or correspond to spurious open reading frames (ORFs). On average there is one gene approximately every two kilobases. Superimposed on alternating regional variations in G+C composition, there is a large central domain with a lower G+C content that contains all the yeast transposon (Ty) elements and most of the tRNA genes. Chromosome IV shares with chromosomes II, V, XII, XIII and XV some long clustered duplications which partly explain its origin.

The mitochondrial genome of Arabidopsis thaliana contains 57 genes in 366,924 nucleotides

We have determined the complete sequence of the mitochondrial DNA in the model plant species Arabidopsis thaliana, affording access to the first of its three genomes. The 366,924 nucleotides code for 57 identified genes, which cover only 10% of the genome. Introns in these genes add about 8%, open reading frames larger than 100 amino acids represent 10% of the genome, duplications account for 7%, remnants of retrotransposons of nuclear origin contribute 4% and integrated plastid sequences amount to 1%-leaving 60% of the genome unaccounted for. With the significant contribution of duplications, imported foreign DNA and the extensive background of apparently functionless sequences, the mosaic structure of the Arabidopsis thaliana mitochondrial genome features many aspects of size-relaxed nuclear genomes.

Genomic recombination of the mitochondrial atp6 gene in Arabidopsis thaliana at the protein processing site creates two different presequences

In the mitochondrial genome of the flowering plant Arabidopsis thaliana the atp6 open reading frame is located on the border of one of the repeats resulting in two copies with different presequence extensions. The two presequences of 135 and 97 amino acids respectively show no similarity to each other, while the mature protein sequences are identical. Both preproteins are most likely synthesized in Arabidopsis mitochondria from promoter elements upstream of each copy. The presence of two arrangements in the mitochondrial genome of fertile Arabidopsis plants suggests this recombination to be unrelated to a cytoplasmic male sterile phenotype. This recombination precisely at the mature protein terminus is reminiscent of the domain shuffling model in protein evolution.

copia-, gypsy- and LINE-like retrotransposon fragments in the mitochondrial genome of Arabidopsis thaliana

Several retrotransposon fragments are integrated in the mitochondrial genome of Arabidopsis thaliana. These insertions are derived from all three classes of nuclear retrotransposons, the Ty1/copia-, Ty3/gypsy- and non-LTR/LINE-families. Members of the Ty3/gypsy group of elements have not yet been identified in the nuclear genome of Arabidopsis. The varying degrees of similarity with nuclear elements and the dispersed locations of the sequences in the mitochondrial genome suggest numerous independent transfer-insertion events in the evolutionary history of this plant mitochondrial genome. Overall, we estimate remnants of retrotransposons to cover > or = 5% of the mitochondrial genome in Arabidopsis.

A school-based self-management program for youth with chronic health conditions and their parents

The Self-Management Program was a school-based intervention for 65 school-aged children with a chronic health condition and their parents. Through the peer group process, a cognitive-behavioural intervention was used to promote the child's self-management of the stresses associated with the chronic condition. Groups were also held to support parents in helping the child to use the newly acquired self-management strategies. A pre- and post-test waiting control group design examined treatment effects on therapeutic adherence, child self-responsibility, and child self-efficacy. Children in the intervention group, in comparison to those in the control group, showed significantly higher therapeutic adherence and more self-responsibility in the management of the health condition. By two months, the improvements in self-responsibility had begun to fade as reported by the children, but remained significant as reported by the parents. No significant differences were found on the self-efficacy measure. Goal attainment, child and parent learning, and consumer satisfaction were also found to be evident.

Nucleotide sequence analysis of a 32,500 bp region of the right arm of Saccharomyces cerevisiae chromosome IV

We have sequenced a region containing 32.5 kb of the right arm of chromosome IV of Saccharomyces cerevisiae. Twenty open reading frames (ORFs) greater than 100 amino acids could be identified in this region. Six ORFs correspond to known yeast genes, including DOA4, UBC5 and UBC3, the gene products of which are involved in ubiquitin metabolism. UBC5 is preceded by the two tRNA genes tRNA-Arg2 and tRNA-Asp. Six genes were discovered with homologies to non-yeast genes or with homologies to other yeast ORFs. One of these could be identified as ribosomal protein gene RPS13. The putative function of eight ORFs remains unclear because comparison to different DNA or protein databases revealed no significant patterns. The sequence from cosmid 2F21 was obtained entirely by a combined subcloning and walking primer strategy, and has been deposited in the EMBL data library under Accession Number X84162.

A nursing assessment standard for early intervention: family coping

Professional standards of practice provide a basis for valid and reliable assessments and quality assurance. The purpose of this case study research was to evaluate a nursing standard, Family Coping, in two families with an infant with cerebral palsy. An assessment protocol was developed from the Family Coping standard and provided the basis for a comprehensive assessment. The case study provided the format and methodologies for implementing the assessment protocol. Patterns of family coping were derived from data collection that occurred at different times and through the use of multiple methods and respondents. The findings of this study confirmed the value of multiple sources of evidence for deriving a diagnosis from which a plan of treatment could be developed. The Family Coping standard proved to be useful for nursing practice by providing a theoretically and empirically based standard for guiding the assessment of family coping.

Physical mapping of the mitochondrial genome of Arabidopsis thaliana by cosmid and YAC clones

As part of the worldwide efforts at molecular analysis of Arabidopsis thaliana as a model plant the complete structure of the mitochondrial genome has been determined. The mitochondrial DNA molecules were mapped by restriction fragment analysis of more than 300 cosmid clones and purified mitochondrial DNA. The entire genome of 372 kb is contained in three different configurations of circular molecules and is split into two additional subgenomic molecules of 234 kb and 138 kb, respectively. These arrangements result from recombinations of the two sets of repeats present in combinations of inverted and/or direct orientation. Alignment of YAC clones confirms the in vivo presence of continuous DNA molecules of more than 300 kb in A. thaliana mitochondria. The presence of this comparatively large mitochondrial genome in a plant with one of the smallest nuclear genomes shows that different size constraints act upon the different genomes in plant cells.