f-Element/crown ether complexes. 26. Crystallization of two hydrated forms of hydrogen bonded complexes of NdCl3·nH2O and 15-crown-5. Crystal structures of [Nd(OH2)9]Cl3·15-crown-5·H2O and [NdCl2(OH2)6]Cl·15-crown-5

When slowly evaporated, the reaction of NdCl₃· nH₂O with 15-crown-5 in a 3:1 mixture of acetonitrile:methanol produces two crystalline hydrates. The decahydrate, [Nd(OH₂)₉]Cl₃·15-crown-5·H₂O, is orthorhombic, P2₁2₁2₁, with (at −150 °C) a = 10.571(4), b = 15.220(7), c = 15.686(7) Å, and D_calc = 1.71 g cm⁻³ for Z = 4. These crystals are stable to the moisture in air. Each Nd is nine-coordinate with tricapped trigonal prismatic geometry. The nine coordinated water molecules are hydrogen bonded to two symmetry related crown ethers, all three chloride ions, and the tenth water molecule. The crown has a total of six hydrogen bonds, four on one side (two to a single oxygen atom) and two on the other. This ether exhibits conformational disorder. The hexahydrate, [NdCl₂(OH₂)₆]Cl·15-crown-5 is deliquescent, dissolving in air and recrystallizing as [NdCl₂(OH₂)₆]Cl. Crystals of this complex are monoclinic, P2₁/n, with (at 20 °C) a = 9.821(3), b = 16.978(9), c = 12.849(8) Å, β = 94.06(5)°, and D_calc = 1.80 g cm⁻³ for Z = 4. The Nd atom exists in a distorted dodecahedral geometry with one chlorine in an A site and one in a B site. The coordinated chlorine atoms accept hydrogen bonds producing polymeric zigzag hydrogen bonded chains along c. The third noncoordinated chloride ion accepts four hydrogen bonds, three from one formula unit and one from a second formula unit related by a unit translation along a. The crown ethers accept five hydrogen bonds, two on one side, and three on the other, thus separating the zigzag chains along b.     

f-Element/crown ether complexes. 1. Synthesis and structure of [Y(OH2)8]Cl3·(15-crown-5)

The crystal and molecular structure of [Y(OH₂)₈]Cl₃·(15-crown-5) has been determined by single- crystal X-ray diffraction. The complex crystallizes in the monoclinic space group P2₁/n with Z = 4. Lattice parameters are a = 9.202(2), b = 17.247(3), c = 15.208(3) Å, and β = 92.39(2)°. The structure was solved by Patterson and Fourier techniques and refined by least-squares to a final conventional R value of 0.081. The Y(III) ion is eight coordinate, bonded to the oxygen atoms of the eight water molecules. Three of the water molecules are hydrogen bonded to crown ether molecules. The three chloride ions participate in hydrogen bonds with the remaining five water molecules. The YO(water) distances range from 2.322(6) to 2.432(7) Å and average 2.37(4) Å. The average O(water)···Cl and O(water)···O(crown) hydrogen bonded separations are 3.08(4) and 2.76(7) Å, respectively.     

The reproductive morphology of Dumontia incrassata (O. F. Müller) Lamouroux

The reproductive morphology of Dumontia incrassata (O. F. Müller) Lamouroux is described from New Hampshire, U.S.A. populations. Mature carpogonial and auxiliary branches are usually 5 and 6 celled, respectively, but both may range from 4 to 9 cells. Auxiliary branches are more numerous than carpogonial branches; however, the ratio of carpogonial to auxiliary branches increases towards the apex of the frond. A linear relationship exists between the position of the generative auxiliary cell and the number of cells in the auxiliary branches. In most cases the third cell from the top of the auxiliary branch becomes the generative auxiliary cell. The probabilities for different positions of the generative auxiliary cells are summarized. During spermatangial development, four mother cells are initially produced per cortical cell initial; subsequently, successive spermatangia are cut off obliquely and on opposite sides of each mother cell. Monoecious asexual plants of D. incrassata are described, as well as an irregular tetraspore development.Scientific Contribution Number from the New Hampshire Agriculture Experiment Station; also issued as contribution No. 81 of the Jackson Estuarine LaboratoryScientific Contribution Number from the New Hampshire Agriculture Experiment Station; also issued as contribution No. 81 of the Jackson Estuarine Laboratory     

Restoration of β-galactosidase to Escherichia coli M15. Complementation studies

Carboxymethylated beta-galactosidase from Escherichia coli was dissociated at 100 degrees C to form carboxymethylated fragments A and B. The mol.wts. of carboxymethylated fragments A and B were determined by gel filtration to be 64300 and 22400 respectively. Sodium dodecyl sulphate/polyacrylamide-gel electrophoresis of carboxymethylated fragments A and B that had been pretreated with 2-mercaptoethanol and sodium dodecyl sulphate yielded mol.wts. of 64000 and 22100 respectively. Carboxymethylated fragments A and B had arginine as their C-terminal amino acid. When a crude extract of E. coli M15 was filtered through a column of Sepharose 6B, it was found that carboxymethylated fragment B could restore beta-galactosidase activity when added to fractions having mol.wts. estimated to be 123000, 262000 and 506000. These fractions are referred to as ;complementable fractions'. Similarly, it was found that carboxymethylated fragment A could restore enzyme activity to tractions having mol.wts. estimated to be 63000, 253000 and 506000. Estimates of the molecular weights of the beta-galactosidase activity obtained by restoration with carboxymethylated fragments A and B were made by filtering the active enzyme through another column of Sepharose 6B. The enzyme obtained by complementation with carboxymethylated fragment B, i.e. the complemented enzyme, had mol.wt. 525000, and that obtained with carboxymethylated fragment A had mol.wts. of 525000, 646000 and 2000000. The latter finding suggests that multiple forms of complemented beta-galactosidase can exist.     

The life-history of Haementeria costata (Fr. Müller) (Glossiphoniidae: Hirudinea)

The frequency of occurrence of Haementeria costata in the waters of north-eastern Poland is 66.5%. This leech is usually found in shallow water zones frequented by water fowl and mammals.The different numbers of individuals taking food and different amounts of food consumed at one meal during successive feedings resulted in individuals of a cohort reaching sexual maturity at the age of 1, 2, and 3 years and surviving for 1.5, 2.5 and 3.5 years, respectively. The differences in weight and age of individuals of populations in their natural environment and in the laboratory depend on the accessibility of food.     

Molecular phylogeny of three Mesalina (Reptilia: Lacertidae) species (M. guttulata, M. brevirostris and M. bahaeldini) from North Africa and the Middle East: another case of paraphyly?

Mesalina is a widespread lacertid genus occurring throughout the Saharo-Sindian region from North Africa to Pakistan. It has been through a series of taxonomic revisions, but the phylogenetic relationships among the species remain unclear. In this study we estimate the phylogeographic structure of M. guttulata across most of its distributional range and we evaluate the relationships between M. guttulata and the sympatric species M. brevirostris and M. bahaeldini using partial mitochondrial DNA (mtDNA) sequences (cyt b and 16S). M. guttulata and M. brevirostris represent species complexes, whereas M. bahaeldini considered before as M. guttulata is a recently described species with very restricted distribution. Here we present the first evidence that M. guttulata is a paraphyletic taxon with respect to M. bahaeldini, while M. brevirostris proves to be a polytypic species or even a species complex, confirming previous studies. Although mtDNA markers have several properties that make them suitable for phylogeographic studies, they are not free of difficulties. Phylogeographic inferences within and between closely related species can be mislead by introgression and retention of ancestral polymorphism (incomplete lineage sorting). However, the present distribution pattern, the estimated times of divergence and the significant variation in morphology within M. guttulata led us to accept that the paraphyletic pattern observed, is most likely due to inaccurate taxonomy. Our hypothesis is that what has hitherto been considered as intraspecific variation, actually reflects species-level variation. Furthermore, our biogeographic analyses and the estimated time of divergences suggest that the present distribution of M. guttulata was the result of several dispersal and vicariant events, which are associated with historical changes (climatic oscillations and paleogeographic barriers) of late Miocene and Pliocene period.     

C-Nucleosides via Glycosyl Alkynyl Ketones. Synthesis of 5(3)-Phenyl-3(5)-(β-D-ribofuranosyl) Pyrazole

Abstract

A β-D-ribofuranosyl phenylethynyl ketone (3) has been synthesized and shown to be a suitable intermediate for heterocyclic elaboration to C-nucleosides. Cyclization of 3 with hydrazine hydrate produces the title C-nucleoside.     

Effects of tissue extract of adults on metamorphosis in Ascidia mentula O.F. Müller and Ascidiella scabra (O.F. Müller)

Unhatched, but fully developed larvae of two solitary ascidians Ascidia mentula O.F. Müller and Ascidiella scabra (O.F. Müller) were incubated in a variety of adult tissue extracts, which an earlier study had shown to accelerate metamorphosis. Our study confirmed this observation and showed, furthermore, that tissue extracts induce tail resorption in unhatched larvae of Ascidiella. For both species, the most active induction of metamorphosis was obtained with tunic tissue extracts. The results indicate that chemical stimulation without the presence of tactile cues may initiate metamorphosis. We suggest that the ability of tunic extracts to induce metamorphosis may explain juvenile establishment on adult ascidians and their aggregated distribution found in nature.     

M.BstF5I-2 and M.BstF5I-4 DNA Methyltransferases from BstF5I Restriction–Modification System of Bacillus stearothermophilus F5

The BstF5I restriction–modification system from Bacillus stearothermophilus F5 includes four site-specific DNA methyltransferases, thus differing from all known restriction–modification systems. Here we demonstrated for the first time that one bacterial cell can possess two pairs of methylases with identical substrate specificities (methylases BstF5I-1 and BstF5I-3 recognize GGATG, whereas methylases BstF5I-2 and BstF5I-4 recognize CATCC) that modify adenine residues on both DNA strands. Different chromatographic methods provide homogenous preparations of methylases BstF5I-2 and BstF5I-4. We estimated the principal kinetic parameters of the reaction of transfer of methyl group from the donor S-adenosyl-L-methionine to the recognition site 5"-CATCC-3" catalyzed by BstF5I-2 and BstF5I-4 DNA [N6-adenine]-methyl-transferases from the BstF5I restriction–modification system.     

Purification and characterization of NAD(P)H quinone reductase from the latex of Hevea brasiliensis Müll.-Arg. (Euphorbiaceae)

NAD(P)H quinone reductase [NAD(P)H-QR] present in the latex of Hevea brasiliensis Müll.-Arg. (Euphorbiaceae) was purified to homogeniety from the B-serum fraction obtained by freeze-thawing of the bottom fraction of ultracentrifuged fresh latex. The purification protocol involved acetone fractionation, heat treatment, ion exchange chromatography and affinity chromatography. The M(r) determined by SDS-PAGE for the protein subunit was 21 kDa, and the molecular mass of the native enzyme estimated by gel filtration was 83 kDa, indicating that the native enzyme is a homotetramer. The enzyme showed pH stability over a range of 6 to at least 10 (with an optimum at pH 8) and thermal stability up to 80 degrees C. High NAD(P)H-QR activity (70%) was still retained after 10 h of preincubation at 80 degrees C. A comparable substrate specificity for this enzyme was observed among menadione, p-benzoquinone, juglone, and plumbagin, with only duroquinone generating a lower activity. Positive correlations between latex NAD(P)H-QR activity and rubber yield per tapping [fresh latex (r=0.89, P<0.01), dry rubber (r=0.81, P<0.01)] together with flow time (r=0.85, P<0.01) indicated that enzyme activity could possibly be used as a marker to predict the yield potential of selected clones.     

M. R. Irwin (1897–1987) Pioneer in Immunogenetics

In Memoriam

M. R. Irwin (1897–1987) Pioneer in Immunogenetics     

Nico M. van Gelder (1933–2005)

IN MEMORIAM

Nico M. van Gelder (1933–2005)     

Remembering John M. Olson (1929–2017)

Light-driven H⁺, Cl^? and Na⁺ rhodopsin pumps all use a covalently bound retinal molecule to capture light energy. Some H⁺-pumping rhodopsins (xanthorhodopsins; XRs) additionally contain a carotenoid antenna for light absorption. Comparison of the available primary and tertiary structures of rhodopsins pinpointed a single Thr residue (Thr216) that presumably prevents carotenoid binding to Na⁺-pumping rhodopsins (NaRs). We replaced this residue in Dokdonia sp. PRO95 NaR with Gly, which is found in the corresponding position in XRs, and produced a variant rhodopsin in a ketocarotenoid-synthesising Escherichia coli strain. Unlike wild-type NaR, the isolated variant protein contained the tightly bound carotenoids canthaxanthin and echinenone. These carotenoids were visible in the absorption, circular dichroism and fluorescence excitation spectra of the Thr216Gly-substituted NaR, which indicates their function as a light-harvesting antenna. The amino acid substitution and the bound carotenoids did not affect the NaR photocycle. Our findings suggest that the antenna function was recently lost during NaR evolution but can be easily restored by site-directed mutagenesis.