Sulphur-aromatic interactions in proteins

The geometry of sulphur-aromatic interactions in globular proteins has been analysed using crystallographic data derived from 36 proteins, solved to resolutions of 2 Å or better. About half of all sulphur atoms from cyst(e)ine and methionine residues are in contact ( 6 Å from ring centroid) with an aromatic ring (phenylalanine, tyrosine or tryptophan). Compared to carbon and nitrogen atoms the interacting sulphur atoms express an affinity towards the edge of the aromatic rings, and avoid the region above the ring in the vicinity of the π-electrons. This preference is similar to that previously found for oxygen atoms around phenylalanine rings, and may be electrostatic in origin.

Sulfw-aromatic interaction Protein Side-chain contact Cyst(e)ine Methionine Packing     

Two new fossil matoniaceous stem genera from Tasmania, Australia

Two new genera, Tasmanopteris and Heweria, from Tasmania are the first definite permineralized rhizomes assignable to the Matoniaceae. Tasmanopteris richmondii sp. nov., of mide-Mesozoic age, is from the Lune River site in southwestern Tasmania and is composed of four or more annular solenostelos separated by cortices with an inner mesarch xylem ring and outer exarch xylem rings. Secretory canals occur in the cortices between the protoxylem clusters of its outer xylem rings. The specimen of Heweria kempii sp. nov., which is very similar to extant Matonia, was collected from a Lower Tertiary conglomerate in central Tasmania but was reworked from older sediments. Anatomically, the rhizomes of Heweria consist of 3–6 annular solenosteles with the inner and middle xylem rings being mesarch, whereas the outer ring is exarch. Roots arise opposite the protoxylem clusters of the outermost ring. Epidermal hairs on the stems of this genus are like those of living Matonia in being attenuate, uniseriate, and multicellular.

Associated venation pattern of partially preserved leaves, isolated sporangia, annuli, and spores in this specimen provide additional support for the relationships of this fossil to modern Matonia.     

苹果轮纹病病害名称之规范

苹果轮纹病(apple ring rot)为苹果重要病害,严重危害果实和枝干,甚至造成幼树枯死等。苹果轮纹病可引起果实腐烂、枝干疣突、溃疡、粗皮等症状,导致苹果轮纹病病害汉语名称使用混乱,如苹果轮纹病、苹果干腐病、苹果果实轮纹病、苹果枝干轮纹病、轮纹烂果病等。病原拉丁学名的使用亦相当混乱,葡萄座腔菌Botryosphaeria dothidea、贝林格葡萄座腔菌B. berengeriana、贝林格葡萄座腔菌梨生专化型B. berengeriana f. sp. pyricola、七叶树壳梭孢Fusicoccum aesculi、锹冢大茎点霉Macrophoma kuwatsukai、梨生囊孢Physalospora pyricola和梨生球座菌Guignardia pyricola等学名都在被使用。本文根据近些年来国内外的研究新进展,认为苹果轮纹病是一类复合病害,与欧美国家发生的白腐病为同一种病害,其病原包括葡萄座腔菌B. dothidea和锹冢葡萄座腔菌B. kuwatsukai。建议将该复合病害汉语统称为苹果轮纹病,英文采用apple ring rot。鉴于两种病原在我国苹果产区的普发性,建议在病害发生规律及抗病育种等研究中,对于葡萄座腔菌和锹冢葡萄座腔菌均需充分重视。     

Reactions of benzocyclobutene chromium complexes with carbon, nitrogen and oxygen nucleophiles: nucleophilic addition and unexpected proximal ring opening reactions

Tricarbonyl(η⁶-1-oxobenzocyclobutene)chromium(0) (1) can be transformed to tricarbonyl(η⁶-1-endo-hydroxybenzocyclobutene) chromium(0) derivatives with substituents R (R=CH₃, CH=CH₂, (CH₂)₄CH=CH₂, (CH₂)₄OSi(Me)₂tBu) at Cl on the exo face of the complex. The relative configuration is proven by an X-ray crystal structure analysis of the trimethylsilyl ether 8 (C₁₆H₁₈CrO₄Si: a=8.693(1), b=9.490(1), c=11.063(1) Å, =97.51(1), β=110.32(1), γ=95.38(1)°, triclinic, space group P (No.2), R=0.037, R_w=0.052 for 4609 observed reflections. Attempts directed at an intramolecular cycloaddition of the ortho-quinodimethane complex derived from 17 by anion promoted ring opening unexpectedly resulted in the formation of 12 as the product of an opening of the proximal bond of the anellated ring located between the hydroxy group and the coordinated aromatic ring in 16. The fact that the intermolecular cycloaddition reaction for 16 is possible in the presence of a dienophile is taken as evidence for an equilibrium between the alcoholate 17 and the two ring opened products 16 and 18. The proximal ring opening of 6 is not observed when the free organic ligand 21 is used as the educt. Ketone complexes 1 and 25 undergo proximal ring opening reaction when treated with alcoholate or primary amines.     

Age of arboreous Tamarix austromongolica and its growth response to environment in Tongde County of Qinghai,China

Aims The objectives were to identify the age of the arboreous Tamarix austromongolica in the flood plain area of the Qinghai Plateau and clarify the response patterns of T. austromongolica’s growth to the environmental factors. We focused on social issues about whether the T. austromongolica should be protected and how to protect in the reservoir area of a hydropower station. Methods In this study, arboreous T. austromongolica in both reservoir submerged and non-submerged areas were sampled and measured based on the dendrochronology method. The ages were estimated based on the geometrical characteristics of the pith and the identified age of the inner ring. The correlation and response analysis showed the relationship between T. austromongolica’s growth and environmental factors. Important findings We accurately determined the age and historical growth dynamics of the T. austromongolica with large diameter at breast height (DBH). The results showed a special accretion phenomenon in arboreous T. austromongolica, which accelerated the DBH increasing, i.e. no direct relationship existed between the plants’ DBH and ages of the individuals. Radial growth of T. austromongolica, increased rapidly in the 1970s and 1980s and began to stabilize in the late 1980s, and mainly responded to the runoff in July and August of the Yellow River. Increasing runoff would promote the radial growth of T. austromongolica. The growth of the immaturate plant showed significant negative correlation with the wind speed in the growing season. The results will be of theoretical significance to the formation of the special morphology of the T. austromongolica, and will provide scientific practical guidance in designing the protection schemes.     

Heptamegacanthus niekerki n. g., n. sp. (Acanthocephala: Oligacanthorhynchidae) from the south-east African insectivore Chrysospalax trevelyani (Günther, 1875)

Heptamegacanthus niekerki n. g., n. sp. is described from the giant golden mole Chrysospalax trevelyani (Günther, 1875) from south-east Africa. It differs from other genera and species in the family mainly by its smaller size, and the number and greater size of hooks in the anterior ring. The family Oligacanthorhynchidae is briefly discussed and a host-parasite list is given for the family Chrysochloridae.     

Nonpeptidic HIV protease inhibitors possessing excellent antiviral activities and therapeutic indices. PD 178390: a lead HIV protease inhibitor

With the insight generated by the availability of X-ray crystal structures of various 5,6-dihydropyran-2-ones bound to HIV PR, inhibitors possessing various alkyl groups at the 6-position of 5,6-dihydropyran-2-one ring were synthesized. The inhibitors possessing a 6-alkyl group exhibited superior antiviral activities when compared to 6-phenyl analogues. Antiviral efficacies were further improved upon introduction of a polar group (hydroxyl or amino) on the 4-position of the phenethyl moiety as well as the polar group (hydroxymethyl) on the 3-(tert-butyl-5-methyl-phenylthio) moiety. The polar substitution is also advantageous for decreasing toxicity, providing inhibitors with higher therapeutic indices. The best inhibitor among this series, (S)-6-[2-(4-aminophenyl)-ethyl]-(3-(2-tert-butyl-5-methyl-phenylsulfanyl)-4-hydroxy-6-isopropyl-5,6-dihydro-pyran-2-one (34S), exhibited an EC₅₀ of 200 nM with a therapeutic index of >1000. More importantly, these non-peptidic inhibitors, 16S and 34S, appear to offer little cross-resistance to the currently marketed peptidomimetic PR inhibitors. The selected inhibitors tested in vitro against mutant HIV PR showed a very small increase in binding affinities relative to wild-type HIV PR. C_max and absolute bioavailability of 34S were higher and half-life and time above EC₉₅ were longer compared to 16S. Thus 34S, also known as PD 178390, which displays good antiviral efficacy, promising pharmacokinetic characteristics and favorable activity against mutant enzymes and CYP3A4, has been chosen for further preclinical evaluation.     

Control of reproduction in female cockroaches with special reference to Nauphoeta cinerea—I. First pre-oviposition period

Prior to the first oviposition, a receptivity centre, perhaps neurosecretory cells in the brain, controls the female's acceptance of courting males. In L. maderae this centre is affected by starvation. A brief exposure to food can induce mating but is inadequate for oöcyte development. Before the first ovulation starvation has no effect on receptivity in N. cinerea.

In N. cinerea mechanical stimulation caused by the firm insertion of the spermatophore in the bursa copulatrix releases stimuli via the nerve cord to the brain which render the female unreceptive and, at the same time, increases the activity of the corpora allata resulting in rapid development of the oöcytes.

The mechanical presence of the oötheca in the uterus also has two principal effects. Like spermatophore insertion, it inhibits mating. But its effect on the corpora allata is inhibitory, rather than stimulatory, and, consequently, the oöcytes remain underveloped for almost the entire gestation period. The effectiveness of inhibitory stimulation from the stretched uterus depends upon the period in the reproductive cycle in which it occurs-i.e. on the physiological state of the female. In N. cinerea uterine stretching inhibits mating and oöcyte development after oviposition or during gestation but is not effective when exerted during the first pre-oviposition period. In P. surinamensis, uterine stretching does not inhibit the corpora allata prior to the first ovulation but does prevent oöcyte development during gestation.

In fed L. maderae and N. cinerea there appears to be a synergistic action of nutrition and mating in controlling the rate of oöcyte development. Mating (mechanical) and feeding (chemical) stimuli are both usually required for activating the corpora allata to their fullest extent so that the oöcytes mature at their maximum rate. There is some indication that mating stimuli in N. cinerea and L. maderae are effective in further stimulating the corpora allata only if the corpora allata have reached a certain level of activity, if activating stimuli have begun to occur in the brain, or if the mating stimulus occurs in combination with nutritional factors. Thus, the corpora allata in starved virgin females of N. cinerea become sufficiently active so that some yolk is deposited in the oöcytes but these oöcytes do not mature; mating is effective in further stimulating the endocrine glands in these starved females and oviposition occurs in about the normal period. In starved virgins of L. maderae the corpora allata are virtually inactive and yolk is not deposited in the oöcytes; mating has no effect on oöcyte development in starved females. D. punctata differs from both the above species in that the corpora allata in the virgin female usually remain inactive whether she feeds or starves. Mating stimuli alone can activate the corpora allata, in fed or starved females, and consequently the oöcytes mature.     

CP6679, a new injectable cephalosporin. Part 1: synthesis and structure-activity relationships

A series of cephalosporins bearing a 5,5-fused ring system, an (imidazo[5,1-b]thiazolium-6-yl)methyl group, at the C-3 position were synthesized and evaluated for in vitro antibacterial activities. CP6679 (1s) and its analogues showed potent antibacterial activities against Gram-positive and Gram-negative bacteria, including Pseudomonas aeruginosa. They were also highly active against methicillin-resistant Staphylococcus aureus (MRSA). CP6679 (1s) showed more potent antibacterial activity than ceftazidime (CAZ) or cefpirome (CPR) against Pseudomonas aeruginosa and MRSA.     

Synthesis of 1,1-difluoro-5-(1H-9-purinyl)-2-pentenylphosphonic acids and the related methano analogues. Remarkable effect of the nucleobases and the cyclopropane rings on inhibitory activity toward purine nucleoside phosphorylase

A series of 1,1-difluoro-5-(1H-9-purinyl)-2-pentenylphosphonic acids, (E)-2a,b and (Z)-2a,b, as well as the related methano analogues (±)-3a,b and (±)-4a,b were prepared for evaluation of their PNP inhibitory activities. The cyclopopane ring and the hypoxanthine residue were found to increase the profile of inhibitory activity. The IC₅₀ and K_i values of difluoro{(1R*,2S*)-2-[2-(6-oxo-6,9-dihydro-1H9-purinyl)ethyl]cyclopropyl}methylphosphonic acid (±)-3b toward PNP purified from Cellulomonas sp. were determined to be 70 nM and 8.8nM, respectively.     

Notes on Technic: Simple, Reliable Detection of Latex Microspheres in High Quality Tissue Sections

Latex microspheres used in biological research have been visualized by light microscopy in mounts of cell suspensions, disrupted cells, or cleared tissues (Mishima et al 1987, Koonce et al 1986, LeFevre et al 1978); in unembedded coverslip monolayers (Koerten et al 1980); in fixed (Cornwall and Phillipson 1988) or unfixed (Wells et al 1988) frozen sections; in paraffin sections cleared and deparaffinized with n-butyl alcohol (Callebaut and Meeussen 1989); and in tissues embedded in resins suitable for transmission electron microscopy, such as Spurr's (Hampton et al 1987), Epon (Herzog and Miller 1979), or Ladd Low Viscosity Epon (LeFevre et al 1985). Paraffin embedding, and some plastic embedments, are impractical for demonstration of latex beads because the beads are dissolved by such organic solvents as xylene, dioxane, or chloroform (Van Furth and Diesselhoff-Den Dulk 1980), propylene oxide (Lentzen et al 1984), amyl acetate (Okada et al 1981), or toluene, the solvent in commonly used mounting media such as Fisher Permount (personal observation). The space remaining after dissolution of a bead is not maintained with paraffin embedding as it is with resin embedding. Even after plastic embedding, the resolving power of light microscopes may be inadequate to distinguish such spaces from other spaces found in and between cells. Latex beads are stable in methanol (Van Furth and Diesselhoff-Den Dulk 1980), ethanol. and n-butyl alcohol (Callebaut and Meeussen 1989).     

A novel resolution of a pharmaceutically important bridged bicyclic ketone intermediate via selective enzymatic reduction with a commercially available ketoreductase

An efficient route to the pharmaceutically important (6S,9R)-11-oxo-5,6,7,8,9,10-hexahydro-6,9-methanobenzocyclooctene intermediate has been demonstrated via kinetic resolution of 11-oxo-5,6,7,8,9,10-hexahydro-6,9-methanobenzocyclooctene using a commercially available ketoreductase. Biocatalytics KRED 101 has been shown to selectively reduce the (6R,9S) enantiomer leaving behind the desired (6S,9R) enantiomer. This novel reaction is the first demonstration of a high yielding (44% versus 50% maximum theoretical yield) highly stereoselective (>99% ee) resolution of a bicyclic ketone, via enzymatic reduction using a commercially available ketoreductase, where the stereochemistry of the substrate is determined by a bridged ring system. Several challenges were overcome, including enhancing the selectivity of the enzyme by controlling temperature and increasing substrate solubility by employing a combination of cyclodextrin and organic co-solvent in the aqueous reaction system.     

Climate, land-use and Prosopis ferox recruitment in the Quebrada de Humahuaca, Jujuy, Argentina

Prosopis ferox grows in upper-elevation, inter-montane valleys between 2600 and 3800 m in Northwestern Argentina and Southern Bolivia. Throughout its range, P. ferox has largely been used as local fuel, building material and food for livestock. In order to evaluate the causes of the recent increase in P. ferox density and range distribution, we compare tree recruitment of P. ferox at 15 stands in the Quebrada de Humahuaca, Jujuy, Argentina, with the environmental and socioeconomic changes in the past 150–200 years. Based on tree recruitment, a general pattern of greater establishment from the mid-1970s to 1990 was identified. This regional pattern is consistent with precipitation variations during the 20th century showing abundant rainfall in the 1970s and 1980s. In addition, historical records indicate that the density of domestic grazers decreased dramatically in the second half of the 20th century. The reduction of browsing by livestock might have also favored the P. ferox recruitment over this interval. However, during the 1990s reduced establishment has occurred at a time of low stock densities suggesting significant precipitation is necessary for the expansion and establishment of these forests. Simply reducing stocking levels will not lead to the long-term recovery of these forests.     

Polarised absorption spectroscopy of chlorophyll-lipid membranes

A technique has been developed for measuring visible absorption spectra of chlorophyll in lipid membranes. An expression is derived which enables the directions of the transition moments of the different absorption bands to be determined from polarisation data. It is found that the transition moments of the principal blue and red absorption bands of chlorophyll a make angles of 26° and 36.5° respectively with the plane of the membrane. On the assumption that these two transitions lie in the plane of the porphyrin ring and are mutually perpendicular, it may be deduced that the plane of the porphyrin ring is tilted at approx. 48° to the membrane surface. For chlorophyll b the transition moments of the blue and red bands are found to make angles of 29.5° and 36.5° with the plane of the bilayer, giving an angle of tilt of the porphyrin ring of approx. 51°.

These results are compared with measurements of dichroism in vivo.     

Synthesis, characterization and bioactivity of a novel iron(III) 18-metallacrown-6 complex with S-donor ligands

The reaction of 4-salicyloyl thiosemicarbazide (H₃st) (1) with FeCl₃ · 6H₂O in methanol solution gives a novel 18-metallacrown-6 [Fe(st)(H₂O)]₆ · 21H₂O (2). The structure containing S–Fe bonds was determined for 2 by using X-ray crystallography. The ring of the metallacrown was consisted of six interlink [Fe–N–N] repeated units. And the ligand enforces the metal ions to form the stereochemistry as a propeller configuration with alternation Λ/Δ form. The largest diameters of the disc-shaped hexanuclear ring are about 7.44 Å at entrance, 9.91 Å at the central of the cavity, respectively. The structural integrity and stability of the metallacrown ring were studied by electronspray ionization ESI-MS and UV–Vis spectroscopy. The results show that it is stable and soluble in methanol. Antibacterial screening data show that the complex 2 weakened dramatically the antibacterial activity of the ligand H₃st.     

A novel esterase from a psychrotrophic bacterium, Acinetobacter sp. strain no. 6, that belongs to the amidase signature family

A novel esterase that belongs to the amidase signature family was found in a psychrotrophic bacterium, Acinetobacter sp. strain no. 6, isolated from Siberian soil. The gene coding for the esterase, named EstA8, was cloned, and an open reading frame of 1488 bp corresponding to 496 amino acid residues was identified. EstA8 showed 30% sequence identity with 6-aminohexanoate-cyclic-dimer hydrolases from Pseudomonas sp. strain NK87 and Flavobacterium sp. strain K172, which degrade a by-product of the nylon-6 industry. EstA8 was overproduced in Escherichia coli JM109 under the control of the lac promoter of pUC118 and purified. Consistent with the fact that the source microorganism is cold-adapted, the enzyme was unstable at moderate temperatures. It lost 75% of its original activity by incubation at 40 °C for 30 min. Despite its structural similarity to 6-aminohexanoate-cyclic-dimer hydrolase, 6-aminohexanoate cyclic dimer did not serve as the substrate. EstA8 is a member of the amidase signature family, but its esterase activity toward p-nitrophenyl esters, such as p-nitrophenyl acetate, was much higher than its amidase activity toward p-nitroanilides, such as p-nitroacetanilide.     

Structures of the galactomannans from seeds of Annona muricata, Arenga saccharifera, Cocos nucifera, Convolvulus tricolor, and Sophora japonica

Galactomannans were isolated from ripe seeds of Annona muricata (Annonaceae), Convolvulus tricolor (Convolvulaceae), Sophora japonica (Leguminosae), and from immature seeds of Arenga saccharifera and Cocos nucifera (both Palmae). Their sugar compositions were determined and their structures studied by the methylation and periodate-oxidation techniques. All the galactomannans studied are of the leguminous type, the molecules having main chains consisting of (1→4)-linked β- -mannose residues, with differing proportions of side chains consisting of single - -galactose residues linked to the main chains by (1→6)-bonds. The molecular weights were found to vary from 6,000 (Sophora) to 17,000 (Arenga). The isolation of the galactomannan of Annona is the first recorded occurrence of this type of polysaccharide in the family Annonaceae, whereas there has been a previous report of the occurrence of a galactomannan in the Convolvulaceae; the study of the structure of the Sophora galactomannan is the first one in the tribe Sophoreae of the Leguminosae.     

Molecular phylogeny and taxonomic revision of Chlamydomonas (Chlorophyta). I. Emendation of Chlamydomonas Ehrenberg and Chloromonas Gobi, and description of Oogamochlamys gen. nov. and Lobochlamys gen. nov

The genus Chlamydomonas (including Chloromonas) is one of the largest green algal genera comprising more than 600 species. To initiate a comprehensive analysis of the phylogeny and systematics of the genus, we determined nuclear-encoded SSU rRNA sequences from 32 strains of Chlamydomonas, Chloromonas and Chlorogonium with emphasis on oogamous taxa and related strains, and incorporated these into global molecular phylogenetic analyses of 132 strains of Chlorophyceae. In addition, we studied the morphology and reproduction of oogamous and related strains by light microscopy. We recognize and designate 18 monophyletic lineages (clades) within the Chlorophyceae, 11 of which are confined to the CW (basal bodies displaced clockwise) subgroup. The majority of clades recognized within the Chlorophyceae do not correspond to any of the traditional classification systems, which are still largely based on the organization level. Strains assigned to Chlamydomonas and Chloromonas were found in seven different clades confirming the polyphyly of the two genera as presently conceived. To initiate the taxonomic revision of Chlamydomonas, C. reinhardtii is proposed as the conserved type of the genus. In consequence, species in clades other than the clade containing C. reinhardtii must be transferred to other genera, a process initiated in this contribution. The oogamous strains studied represent a monophyletic lineage, which is described as Oogamochlamys gen. nov. comprising three species (O. gigantea, O. zimbabwiensis and O. ettlii spec. nov.). The sister clade to Oogamochlamys consists of isogamous strains characterized by chloroplasts with incisions and is described as Lobochlamys gen. nov. with two species (L. culleus and L. segnis). Another clade is characterized by asteroid or perforated, parietal chloroplasts and contains the type species of Chloromonas (C. reticulata). Thus, the polyphyletic Chloromonas (traditionally defined as “Chlamydomonas without pyrenoids”) can be legitimized as a monophyletic genus by restriction to this clade and is here emended on the basis of chloroplast characters (the clade contains strains with or without pyrenoids thus rejecting the character “absence of pyrenoids”).     

基于黄山松树轮重建华东天目山地区1809—2018年4—7月平均气温

利用浙江北部西天目山高海拔黄山松树轮样品,建立了340年的整轮、早材和晚材宽度年表,根据子样本信号强度大于0.8的标准,确定年表的可靠时段为1810—2019年,通过对年表与气候要素进行相关分析,研究了树轮生长对气候的响应。结果表明: 黄山松径向生长对气温的响应远高于对降水的响应。综合考虑原始序列和一阶差序列相关分析结果,发现早材宽度与上年生长季前期平均气温、平均最高气温显著相关,晚材宽度与上年5月和当年9月平均气温、平均最高气温显著相关。整轮响应时段与早材较为一致,但相关性较低。最优相关组合为早材宽度与上年4—7月平均气温。基于这一关系,重建了华东天目山地区1809—2018年4—7月平均气温,方差解释量达61.5%,原始序列和一阶差序列均通过分段检验。重建气温序列中的偏冷时段为1834—1964年,偏暖时段为1809—1833和1965—2018年。20世纪60年代以来,气温进入快速上升阶段,从低频趋势上看,20世纪80年代之后气温达到过去210年来的最高水平。空间相关分析表明,重建序列较好地代表了华东地区气温的变化情况,与华东地区的区域重建序列对比也具有较好的一致性。黄山松在华东地区古气候重建方面具有较大潜力。