ABSTRACT
Unique tunable aryl imidazolium ionic liquids successfully catalyzed Friedel-Crafts acylation and thioesterification in sealed tubes. These reactions can form a C-C bond and a C-S bond with high atom economy. Ionic liquids exhibited high activity and catalyzed essential reactions with good to excellent yields while retaining their catalytic activities for recycling.
Subject(s)
Imidazoles/chemistry , Ionic Liquids/chemistry , Lewis Acids/chemistry , Sulfhydryl Compounds/chemistry , Acylation , Catalysis , EsterificationABSTRACT
Helicobacter pylori is a bacterium that causes chronic active gastritis and peptic ulcers. Drugs targeting H. pylori phosphopantetheine adenylyltransferase (HpPPAT), which is involved in CoA biosynthesis, may be useful. Herein, we report the expression in Escherichia coli and purification of recombinant HpPPAT and describe a crystal structure for an HpPPAT/CoA complex. As is the case for E. coli PPAT (EcPPAT), HpPPAT is hexameric in solution and as a crystal. Each protomer has a well-packed dinucleotide-binding fold in which CoA binds. Structural characterisation demonstrated that CoA derived from the E. coli expression system bound tightly to HpPPAT, presumably to initiate feedback inhibition. However, the interactions between the active-site residues of HpPPAT and CoA are not identical to those of other PPATs. Finally, CoA binding affects HpPPAT thermal denaturation.
Subject(s)
Helicobacter pylori/enzymology , Nucleotidyltransferases/chemistry , Amino Acid Sequence , Coenzyme A/chemistry , Crystallography, X-Ray , Enzyme Stability , Escherichia coli/genetics , Molecular Sequence Data , Nucleotidyltransferases/genetics , Protein Multimerization , Protein Structure, Quaternary , Protein Structure, Secondary , Recombinant Proteins/chemistry , Recombinant Proteins/genetics , Spectrophotometry, UltravioletABSTRACT
Interleukin-1 beta (IL-1ß) is an important cytokine in the immune system. The properties of avian IL-1ßs are less well understood than the mammalian IL-1ßs, and there is no available structure of avian IL-1ßs in the Protein Data Bank. Here, we report the crystal structures of wild-type and Y157F mutant IL-1ßs from chicken. Both the wild-type and mutant IL-1ßs share a beta-trefoil conformation similar to that of human IL-1ß and also have an internal hydrophobic cavity. However, the cavity sizes clearly differ from that of human IL-1ß due to the packing of hydrophobic residues. Our studies also reveal that the relative thermal stability of IL-1ßs does not correlate with cavity size but rather is dependent on the amino acid residues present around the cavity. This cavity serves as a scaffold for maintaining the structure of the IL-1ß core region but does not have a biological function per se. Moreover, we found that human IL-1ß cannot induce chemokine expression in chicken fibroblasts or elevate plasma cortisol levels in chickens, implying a lack of cross-species bioactivity. Close examination reveals that significant structural and sequence differences occur in the terminal and some loop regions between human and chicken IL-1ßs. These variable regions have been shown to be critical for receptor binding, thus resulting in a lack of species cross-reactivity between human and chicken IL-1ß.
Subject(s)
Chickens , Interleukin-1beta/chemistry , Interleukin-1beta/immunology , Amino Acid Sequence , Animals , Biophysical Phenomena , Chemokines/genetics , Chemokines/metabolism , Chickens/blood , Chickens/immunology , Crystallography, X-Ray , Fibroblasts/metabolism , Humans , Hydrocortisone/blood , Immunoassay , Molecular Sequence Data , Mutant Proteins/immunology , Protein Interaction Mapping , Recombinant Proteins/chemistry , Recombinant Proteins/immunology , Structural Homology, Protein , TemperatureABSTRACT
The aim of this study was to evaluate attitudes toward life and death among nursing students after attending the life and death studies (LDS) program. Both qualitative and quantitative methods were used to collect data. The pretest-posttest control group design randomly assigned students to an experimental (n = 47) or control group (n = 49). The 13-week course included lectures, video appraisal, games, simulations, films, books, assignments and group sharing. Statistical and content analysis were used to analyze qualitative and quantitative data. The findings showed a significant improvement in perception of the meaningfulness of life in four categories of improvement: expanded viewpoint, sadness about death, treating life sincerely, and instilling hope in life. The qualitative data indicated that a positive change in meaning of life was associated with interaction with others and self-reflection.
