Highly Efficient Method for Solvent-Free Synthesis of Diarylmethane and Triarylmethane from Benzylic Alcohols Using P2O5/Al2O3 or P2O5/SiO2 at Room Temperature

A highly efficient procedure for the synthesis of triarylmethane and diarylmethane via benzylation of aromatic hydrocarbons from benzyl alcohols using supported P2O5 on SiO2 and/or Al2O3 under solvent-free conditions is described. Excellent yields of triarylmethane and diarylmethane were obtained using P2O5-SiO2 (50% W/W) and/or P2O5-Al2O3 (50% W/W) at room temperature. The reusability of both supported P2O5 on SiO2 and Al2O3 were examined. Both supported reagents show favorable activities in first and second runs, however, a decline in reactivity was observed in following attempts. The reaction is scalable to >0.03 mole amounts.Keywords: Diarylmethane, triarylmethane, aromatic alcohol, P2O5, silica gel, alumin

18S rRNA processing requires base pairings of snR30 H/ACA snoRNA to eukaryote-specific 18S sequences

The H/ACA RNAs represent an abundant, evolutionarily conserved and functionally diverse class of non-coding RNAs. Many H/ACA RNAs direct pseudouridylation of rRNAs and snRNAs, while members of the rapidly growing group of ‘orphan' H/ACA RNAs participate in pre-rRNA processing, telomere synthesis and probably, in other nuclear processes. The yeast snR30 ‘orphan' H/ACA snoRNA has long been known to function in the nucleolytic processing of 18S rRNA, but its molecular role remained unknown. Here, we provide biochemical and genetic evidence demonstrating that during pre-rRNA processing, two evolutionarily conserved sequence elements in the 3′-hairpin of snR30 base-pair with short pre-rRNA sequences located in the eukaryote-specific internal region of 18S rRNA. The newly discovered snR30-18S base-pairing interactions are essential for 18S rRNA production and they constitute a complex snoRNA target RNA transient structure that is novel to H/ACA RNAs. We also demonstrate that besides the 18S recognition motifs, the distal part of the 3′-hairpin of snR30 contains an additional snoRNA element that is essential for 18S rRNA processing and that functions most likely as a snoRNP protein-binding site

Pseudouridine synthase 1: a site-specific synthase without strict sequence recognition requirements

Pseudouridine synthase 1 (Pus1p) is an unusual site-specific modification enzyme in that it can modify a number of positions in tRNAs and can recognize several other types of RNA. No consensus recognition sequence or structure has been identified for Pus1p. Human Pus1p was used to determine which structural or sequence elements of human tRNASer are necessary for pseudouridine (Ψ) formation at position 28 in the anticodon stem-loop (ASL). Some point mutations in the ASL stem of tRNASer had significant effects on the levels of modification and compensatory mutation, to reform the base pair, restored a wild-type level of Ψ formation. Deletion analysis showed that the tRNASer TΨC stem-loop was a determinant for modification in the ASL. A mini-substrate composed of the ASL and TΨC stem-loop exhibited significant Ψ formation at position 28 and a number of mutants were tested. Substantial base pairing in the ASL stem (3 out of 5 bp) is required, but the sequence of the TΨC loop is not required for modification. When all nucleotides in the ASL stem other than U28 were changed in a single mutant, but base pairing was retained, a near wild-type level of modification was observed

Optimization of Ribosome Structure and Function by rRNA Base Modification

BACKGROUND: Translating mRNA sequences into functional proteins is a fundamental process necessary for the viability of organisms throughout all kingdoms of life. The ribosome carries out this process with a delicate balance between speed and accuracy. This work investigates how ribosome structure and function are affected by rRNA base modification. The prevailing view is that rRNA base modifications serve to fine tune ribosome structure and function. METHODOLOGY/PRINCIPAL FINDINGS: To test this hypothesis, yeast strains deficient in rRNA modifications in the ribosomal peptidyltransferase center were monitored for changes in and translational fidelity. These studies revealed allele-specific sensitivity to translational inhibitors, changes in reading frame maintenance, nonsense suppression and aa-tRNA selection. Ribosomes isolated from two mutants with the most pronounced phenotypic changes had increased affinities for aa-tRNA, and surprisingly, increased rates of peptidyltransfer as monitored by the puromycin assay. rRNA chemical analyses of one of these mutants identified structural changes in five specific bases associated with the ribosomal A-site. CONCLUSIONS/SIGNIFICANCE: Together, the data suggest that modification of these bases fine tune the structure of the A-site region of the large subunit so as to assure correct positioning of critical rRNA bases involved in aa-tRNA accommodation into the PTC, of the eEF-1A•aa-tRNA•GTP ternary complex with the GTPase associated center, and of the aa-tRNA in the A-site. These findings represent a direct demonstration in support of the prevailing hypothesis that rRNA modifications serve to optimize rRNA structure for production of accurate and efficient ribosomes

Point Mutations in Yeast CBF5 Can Abolish In Vivo Pseudouridylation of rRNA

In budding yeast (Saccharomyces cerevisiae), the majority of box H/ACA small nucleolar RNPs (snoRNPs) have been shown to direct site-specific pseudouridylation of rRNA. Among the known protein components of H/ACA snoRNPs, the essential nucleolar protein Cbf5p is the most likely pseudouridine (Ψ) synthase. Cbf5p has considerable sequence similarity to Escherichia coli TruBp, a known Ψ synthase, and shares the “KP” and “XLD” conserved sequence motifs found in the catalytic domains of three distinct families of known and putative Ψ synthases. To gain additional evidence on the role of Cbf5p in rRNA biosynthesis, we have used in vitro mutagenesis techniques to introduce various alanine substitutions into the putative Ψ synthase domain of Cbf5p. Yeast strains expressing these mutated cbf5 genes in a cbf5Δ null background are viable at 25°C but display pronounced cold- and heat-sensitive growth phenotypes. Most of the mutants contain reduced levels of Ψ in rRNA at extreme temperatures. Substitution of alanine for an aspartic acid residue in the conserved XLD motif of Cbf5p (mutant cbf5D95A) abolishes in vivo pseudouridylation of rRNA. Some of the mutants are temperature sensitive both for growth and for formation of Ψ in the rRNA. In most cases, the impaired growth phenotypes are not relieved by transcription of the rRNA from a polymerase II-driven promoter, indicating the absence of polymerase I-related transcriptional defects. There is little or no abnormal accumulation of pre-rRNAs in these mutants, although preferential inhibition of 18S rRNA synthesis is seen in mutant cbf5D95A, which lacks Ψ in rRNA. A subset of mutations in the Ψ synthase domain impairs association of the altered Cbf5p proteins with selected box H/ACA snoRNAs, suggesting that the functional catalytic domain is essential for that interaction. Our results provide additional evidence that Cbf5p is the Ψ synthase component of box H/ACA snoRNPs and suggest that the pseudouridylation of rRNA, although not absolutely required for cell survival, is essential for the formation of fully functional ribosomes

Deep Rest: An Integrative Model of How Contemplative Practices Combat Stress and Enhance the Body’s Restorative Capacity

Engaging in contemplative practice like meditation, yoga, and prayer, is beneficial for psychological and physical well-being. Recent research has identified several underlying psychological and biological pathways that explain these benefits. However, there is not yet consensus on the underlying overlapping physiological mechanisms of contemplative practice benefits. In this article, we integrate divergent scientific literatures on contemplative practice interventions, stress science, and mitochondrial biology, presenting a unified biopsychosocial model of how contemplative practices reduce stress and promote physical health. We argue that engaging in contemplative practice facilitates a restorative state termed "deep rest," largely through safety signaling, during which energetic resources are directed toward cellular optimization and away from energy-demanding stress states. Our model thus presents a framework for how contemplative practices enhance positive psychological and physiological functioning by optimizing cellular energy consumption. (PsycInfo Database Record (c) 2024 APA, all rights reserved)