Enzymatic synthesis and some properties of a model primitive tRNA

Summary A model primitive tRNA with the nucleotide sequence GGCCAAAAAAAGGCCp was synthesized using T₄ RNA ligase. The nucleotide sequence of this newly synthesized oligonucleotide was confirmed by ladder analysis of several enzymatic digestion products. The secondary structure of the oligonucleotide was examined by comparison of the products of its digestion by single- and double-strand-specific nucleases with those of the digestion of the intermediate oligonucleotide GGCCAAAAAAA_OH. The results indicated that the two GGCC segments of the 5 and 3 ends of the model tRNA may form base pairs in solution. The same conclusion was derived from the result of affinitycolumn chromatography of the model oligonucleotide. When³²pGGCCAAAAAAAGGCC_OH was passed through a poly(U)-agarose column, about 70% of the applied sample bound to the poly(U)-agarose. In contrast, when the model oligonucleotide was passed through a poly(C)-agarose column, only 15% of the sample bound to the poly(C)-agarose. These results indicate that the newly synthesized oligonucleotide adopts a hairpin structure in solution. Two aspects of a potential biological activity of the synthetic model tRNA were examined. It was found that the oligonucleotide can bind to poly(U)-programmed 30S ribosomes and is recognized by Q replicase as a template for RNA synthesis.     

Detection and Characterization of UDP-Glucose:Flavonoid O-Glucosyltransferases in the Leaves of Prunus ? yedoensis Matsum

A novel O-glucosyltransferase (I4'GT) which catalyzes the transferof D-glucose from UDP-D-glucose to position 4' of prunetin (4',5-dihydroxyl-7-methoxyisoflavone)was isolated from the leaves of Prunus ? yedoensis Matsum. andpurified 66-fold by precipitation with ammonium sulfate andchromatography on DEAE-cellulose. UDP-glucose:flavonol 3-O-glucosyltransferase(F3GT) was also isolated and purified 50-fold in the same manner.The molecular weights of both I4'GT and F3GT were estimatedby elution from a column of Sephadex G-100 to be about 51,000Da. The pH optima for I4'GT and F3GT activities were 8.0 and7.5, respectively. The specificities of I4'GT and F3GT for thesugar donor were quite strict, and only UDP-glucose could serveas glucosyl donor, both ADP-D-glucose and GDP-D-glucose beingineffective. The apparent K_m values for UDP-glucose and prunetinwere 10.0µM and 1.20µM, respectively, for I4'GT.The K_m values for UDP-glucose and quercetin were 9.8 µMand 1.21 µM, respectively, for F3GT. The activities ofboth I4'GT and F3GT were stimulated by 1 mM Mg*⁺ and stronglyinhibited by 1 mM Cu²⁺, 1 mM Zn²⁺ and various reagents thatreact with sulfhydryl groups. (Received May 16, 1990; Accepted September 3, 1990)     

Astaxanthin protects mitochondrial redox state and functional integrity against oxidative stress

Mitochondria combine the production of energy with an efficient chain of reduction–oxidation (redox) reactions but also with the unavoidable production of reactive oxygen species. Oxidative stress leading to mitochondrial dysfunction is a critical factor in many diseases, such as cancer and neurodegenerative and lifestyle-related diseases. Effective antioxidants thus offer great therapeutic and preventive promise. Investigating the efficacy of antioxidants, we found that a carotenoid, astaxanthin (AX), decreased physiologically occurring oxidative stress and protected cultured cells against strong oxidative stress induced with a respiratory inhibitor. Moreover, AX improved maintenance of a high mitochondrial membrane potential and stimulated respiration. Investigating how AX stimulates and interacts with mitochondria, a redox-sensitive fluorescent protein (roGFP1) was stably expressed in the cytosol and mitochondrial matrix to measure the redox state in the respective compartments. AX at nanomolar concentrations was effective in maintaining mitochondria in a reduced state. Additionally, AX improved the ability of mitochondria to remain in a reduced state under oxidative challenge. Taken together, these results suggest that AX is effective in improving mitochondrial function through retaining mitochondria in the reduced state.     

Studies on the Chemical Synthesis of Potential Antimetabolites. 371. Synthesis of 3-Deazaadenine Nucleosides Modified at the Sugar Moiety

Abstract

Several types of 3-deazaadenine pentofuranosides, represented by 9-(3-deoxy-β-D-glycero-pent-3-enofuranosyl)-3-deazaadenine (1), 9-(5-deoxy-β-Q-erythro-pent-4-enofuranosyl)-3-deazaadenine (2) and 9-β-D-xylo-furanosyl-3-deazaadenine (3), were prepared starting from 6-chloro-9-β-D-ribofuranosyl-3-deazaadenine (4).     

Synthesis and antimalarial activity of calothrixins A and B, and their N-alkyl derivatives

We synthesized calothrixin B using our developed biomimetic method and derived N-alkyl-calothrixins A and B. The in vitro antimalarial activity of the calothrixin derivatives, including calothrixins A and B, against the Plasmodium falciparum FCR-3 strain was evaluated. All test compounds exhibited antimalarial activity over a concentration range of 6.4×10(-6)-1.2×10(-7) M.     

3-Desoxyanthocyanin and other phenolics in the water fernAzolla

The phenolic compounds ofAzolla imbricata andA. japonica have been examined in the present study. Both species were found to contain luteolinidin 5-glucoside and several phenolic compounds, particularly chlorogenic acid, aesculetin, caffeic acid 3,4-diglucoside and 6-(3′-glucosylcaffeoyl)-aesculetin. In addition, glucose esters ofp-coumaric acid and glucose, 1,6-diester of caffeic and chlorogenic acids were present in a small amount. The acid- and alkali-hydrolyzates ofAzolla plants yielded caffeic acid and aesculetin present at the level of about 0.047% and 0.012% in fresh plants, and a large part of the caffeic acid seems to be present as the ester.