Structural basis for the RNA binding selectivity of oligonucleotide analogues containing alkylsulfide internucleoside linkages and 2'-substituted 3'-deoxyribonucleosides.

In this report we describe the synthesis of oligonucleotides containing sulfide-linked dinucleoside units, namely rT(2'OH)sdT, rT(2'OMe)sdT, dTsrU(2'OMe) and dT(2'OMe)srU(2'OMe). We also describe the interactions of such oligomers with complementary DNA and RNA targets, and provide the structural basis for their remarkable RNA binding selectivity. In all cases, the Tm values of the S/P-chimera duplexes were lower than those of the corresponding unmodified duplexes. We attribute this to steric interactions between the 5'sulfur and the atoms of the nearby base/sugar residues. The 2'-substituents (i.e., 2'OH or 2'OMe) vicinal to the alkylsulfide internucleoside linkage significantly perturb the structure and stability of the duplexes formed with DNA, and more so than with RNA. The introduction of three rT(2'OH)sdTp (or rT(2'OMe)sdTp) units into an oligodeoxynucleotide sequence was sufficient to abolish binding to complementary DNA but not RNA. The same three substitutions with dTsrU(2'OMe)p and dT(2'OMe)srU(2'OMe)p did not abolish binding to DNA but the resulting complexes had poor thermal stability. The RNA-binding 'selectivity' exhibited by these oligomers is attributed to the tendency of the 2'-substituted (branched) furanoses to adopt the C3'-endo pucker, a conformation that is inconsistent with the B-form structure of helical DNA. The preference of these sugars to exist often exclusively in the C3'-endo form is attributed to stereoelectronic effects, namely gauche and anomeric effects. Our findings support the hypothesis that nucleoside analogues puckered exclusively in the C3'-endo form may result in them being especially good binders of targeted mRNA [S.H. Kawai (1991), Ph.D. Thesis, McGill University; Kawasaki et al. (1993) J. Med. Chem. 36, 831-841].     

秦艽体细胞胚不同发育阶段几种同工酶的特性

以秦艽（ＧｅｎｔｉａｎａｃｒａｓｓｉｃａｕｌｉｓＤｕｔｈｉｅｅｘＢｕｒｋｉｌｌ）无菌苗幼嫩茎叶为外植体,在ＭＳ培养基上诱导出胚性愈伤组织及体细胞胚。本文比较了秦荒体细胞胚发育过程中几种酶的活性及同工酶变化。过氧化物酶与细胞色素氧化酶均在球形胚阶段出现一活性高峰;酯酶同工酶在体细胞胚发育过程中伴有特征带Ｅ＿２、Ｅ＿６的出现;酸性磷酸酯酶的活性与体细胞胚发育程度呈正相关。所以认为只要综合运用这几种同工酶的实验数据,就可以灵敏检测体细胞胚的发育进程。     

Bilayer orientation of membrane-bound NH2 groups across microsomal vesicles and their role in the function of gastric K+-stimulated adenosine triphosphatase

The transversal distribution of the free NH₂ groups associated with phosphatidyl ethanolamine and the intrinsic membrane proteins of the purified pig gastric microsomes was quantitated and their relations to the function of the gastric K⁺-stimulated ATPase was investigated. Three different chemical probes such as 2,4,6-trinitrobenzene sulfonic acid (TNBS), 1-fluoro-2,4-dinitrobenzene (FDNB), and 2-methoxy-2,4-diphenyl-3(2H)-furanone (MDPF) were used for the study. The structure-function relationship of the membrane NH₂ groups was studied after modification with the probes under various conditions and relating the inhibition of the K⁺-stimulated ATPase to the ATPase-dependent H⁺ accumulation by the gastric microsomal vesicles. TNBS (2 mm) inhibits nearly completely the K⁺-stimulated ATPase and the vesicular dye accumulation, both in presence and absence of valinomycin plus K⁺. Both the K⁺-ATPase and dye uptake were largely (about 50%) protected against TNBS inhibition if the treatment with TNBS was carried out in presence of 2 mm ATP. TNBS and FDNB labeled 70% of the total microsomal PE; the intra- and extravesicular orientation being 48 and 22%, respectively. The presence or absence of ATP did not have any effect on the TNBS labeling of microsomal PE. ATP, however, significantly (P < 0.05) reduced the labeling of protein-bound NH₂ groups of gastric microsomes by TNBS. The intra- and extravesicular orientation of the protein NH₂ groups were 60 and 40%, respectively. Eighteen percent of the total protein-NH₂ appeared to be associated with the K⁺-stimulated ATPase; the rest being associated with non-ATPase proteins of the microsomes. About half (50%) of the total free NH₂ groups of the K⁺-stimulated ATPase were exposed to the vesicle exterior and were found to play critical roles in gastric ATPase function. The generation of florescence after MDPF conjugation of gastric microsomes was largely (50%) inhibited by ATP. ATP also protected completely the MDPF inhibition of gastric K⁺-stimulated ATPase and dye uptake.     

Studies in African Cyperaceae 20. New taxa and combinations in Pycreus Beau v.

One new species, five new subspecies and one variety of the genus Pycreus , are described from East Africa, viz. Pycreus micromelas Lye, P. sanguinolenlus (Vahl) Nees ssp. nairobiensis Lye, P. longistolon Kükenthal ssp. airofusca Lye, P. lanceolatus (Poiret) C. B. Clarke ssp. ugandensis Lye, P. flavescens (L.) Reichenb. ssp. laevinux Lye, P. flavescens (L.) Reichenb. ssp. microglumis Lye, and P. flavescens (L.) Reichenb. var. castaneus Lye.
In addition eight new combinations are made, viz. P. alms (Turrill) Lye, P. af–rozonatus Lye, P. niger (Ruiz & Pavon) Cufod. ssp. elegantulus (Steudel) Lye, P. macrostachyos (Lam.) J. Raynal ssp. tremulus (Poiret) Lye, P. flavescens (L.) Reichenb. ssp.fallaciosus (Cherm.) Lye, P. flavescens (L.) Reichenb. ssp. intermedius (Steudel) Lye, and P. flavescens (L.) Reichenb. ssp. tanaënsis (Kükenthal) Lye.     

Studies in African Cyperaceae 21. New taxa and combinations in Kyllinga Rottb.

Eight new species, one new subspecies and one new variety of Kyllinga are described from tropical Africa, viz. Kyllinga brunneoalba Lye, K. afropumila Lye, K, albogracilis Lye, K. aureovillosa Lye, K. alba–purpurea Lye, K. rhizomafragilis Lye, K. microbracleata Lye, K. afro–occidentalis Lye, K. erecta Schumacher ssp. albescens Lye, and K. melanosperma Nees var. hexalata Lye. In addition nine new combinations are made, viz. Kyllinga peteri (Kükenthal) Lye, K. bigibbosa (Fosberg) Lye, K. odorata Vahl ssp. appendiculata (K. Schum.) Lye, K. alba Nees ssp. ascolepidioides (H. Cherm.) Lye, K. nervosa Steudel ssp.flava (C.B.C1.) Lye, K. melanosperma Nees ssp. elata (Steudel) Lye, K. brevifolia Rottb. ssp. lurida (Kükenthal) Lye, K. bre–vifolia Rottb. ssp. intricata (H. Cherm.) Lye, and K. comosipes (Mattf. & Kükenthal) Agnew & Hanid ssp. decolorans (Kükenthal) Lye.     

Studies in African Cyperaceae 19. The genera Anosporum Nees and Sorostachys Steudel

The two genera Anosporum Nees and Sorostachys Steudel, both with a congested inflorescence and an eucyperoid culm– and leaf–anatomy, are reestablished. They have previously been placed in Cyperus s.l. Anosporum contains three distinct species, two of which are found in Africa. Sorostachys contains two species, one of which is found in Africa. Three new combinations are made, viz. Anosporum pec–tinatus (Vahl) K. Lye, Sorostachys pulchellus (R.Br.) K. Lye, and S. leucocephalus (Retz.) K. Lye.     

Stimulation of ovine myometrial activity by 6-keto prostaglandin E1

6-keto prostaglandin E₁ (6KE) is a metabolite of PGI₂, which we have shown previously inhibits spontaneous myometrial activity. In the present study we examined the effects of 6KE on uterine electrical and mechanical activity in non-pregnant ovariectomized sheep. 6KE stimulated uterine activity in a dose-dependent fashion. The effect was enhanced by pre-treatment with estradiol (E2). It was not influenced by pre-treatment with meclofenamic acid and was not associated with significant changes in the concentrations of 13,14 dihydro 15-keto PGF_2α in vena cava plasma. After E2 treatment, 6KE had 0.2–0.3 of the stimulatory activity of PGF_2α. In the absence of E2, the uterine response to both 6KE and PGF_2α was decreased. In animals in which spontaneous myometrial activity was inhibited by PGI2, the uterus remained responsive to 6KE. We conclude that in the ovariectomized non-pregnant sheep 6KE stimulates uterine activity, and that the effect is independent of endogenous PG production.     

Studies in African Cyperaceae 24. New taxa and combinations in Ascolepis and Isolepis

One new species, three new subspecies and two new varieties of Ascolepis Steudel and one new species of Isolepis R. Br. are described from East Africa, viz. Ascolepis lineariglumis Lye, A. lineariglumis Lye var. pulcherrima Lye, A. protea Welw. ssp. rhizomatosa Lye, A. protea Welw. ssp. atropurpurea Lye, A. protea Welw. ssp. chrysocephala Lye, A. pusilla Ridley var. microcuspis Lye, and Isolepis keniaensis Lye. Two new combinations are made, viz. Ascolepis protea Welw. ssp. anthemiflora (Welw.) Lye and A. protea Welw. ssp. bellidiflora (Welw.) Lye.     

用亲和层析技术分离纯化天冬氨酸酶

<正> 亲和层析技术做为现代生化实验室常用的提纯方法,具有专一性强,活力损失小,分离步骤少等优点。天冬氨酸酶是重要的酶制剂,以往见报的分离纯化工艺步骤繁琐,活力损失大。本文报道的新工艺是用聚乙二醇(PEG)/磷酸钾双水相抽提;DEAE-sophadex A-50柱层析除PEG和部分杂蛋白;环氧氯丙烷活化载体,底物作配基的亲和层析技术获得了电泳纯的天冬氨酸酶。