Organolanthanoids. XIII. Bis(pentadeuterocyclopentadienyl)ytterbium(II)

The complex (C₅D₅)₂Yb(dme) (dme = 1,2- dimethoxyethane) has been prepared by reaction of Tl(C₅D₅) with ytterbium metal in dme and is isostructural with (C₅H₅)₂Yb(dme). Thermal desolvation under vacuum yields (C₅D₅)₂Yb, for which essentially identical high resolution neutron powder diffraction data were obtained at 294 K and 77 K, but the structure could not be determined.     

Lindernia kinmenensis sp. nov. (Scrophulariaceae) from Kinmen (Taiwan)

Lindernia kinmenensis Y. S. Liang, C. H. Chen, & C. L. Tasi sp. nov. from Kinmen (Taiwan) is described. The new species belongs to section Torenioides and is most similar to L. crustacea. It differs from the latter by the following characters: calyx pubescent between the ridges (vs pubescent on ridges), with (2)3(4) bristles on the ridge near the apex of the calyx‐lobes (vs without such bristles), corolla shorter, 6–8 mm long (vs 7–11 mm long) and pale purple (vs purple or blue), posterior theca with obtuse (vs acute) apex. This species is usually found in sandy wetlands. A line drawing, colour photos and SEM micrographs of pollen and seed as aids for identification are provided.     

Linkage of plasminogen (PLG) and apolipoprotein(a) (LPA) in baboons.

Four allelic forms of serum plasminogen (PLG) were detected in baboons (Papio hamadryas Linneaus 1758) by isoelectric focusing and were determined to be inherited as autosomal codominant traits. Linkage analysis of data from 179 progeny and their parents revealed that PLG is tightly linked (lod score = 30.20) to the gene encoding apolipoprotein(a) (LPA), as in humans. No recombinant individuals were identified. This is the first linkage detected between PLG and LPA in any species other than humans and is the first genetic linkage identified in a nonhuman primate species by family studies.     

Photophysical properties of Pr(III) and Er(III) complexes of poly(pyrazolyl)borates.

The complexes [M(L(1))(2)(NO(3))] and [M(L(2))(NO(3))(2)](M = Pr, Er; L(1)= the tetradentate ligand dihydrobis-[3-(2-pyridyl)pyrazolyl]borate; L(2)= the hexadentate ligand hydrotris-[3-(2-pyridyl)pyrazolyl]borate) were prepared and their structural and photophysical properties studied. All complexes are 10-coordinate. Crystallographic analysis of [M(L(1))(2)(NO(3))](M = Pr, Er) showed that for the smaller Er(iii) ions steric congestion at the metal centre results in two of the Er-N(pyridyl) distances being particularly long, which does not occur with the larger Pr(iii) ion that is better able to accommodate 10-fold coordination. On UV irradiation, both Pr(iii) complexes show, in the visible region of their luminescence spectra, transitions originating from both the (3)P(0) level (at ca. 21,000 cm(-1)) and the (1)D(2) level (at ca. 17,000 cm(-1)), a consequence of the fact that the lowest triplet state of the coordinated pyrazolylborate ligands lies at ca. 24,000 cm(-1) in each case so is high enough in energy to populate both levels. This contrasts with Pr(iii) complexes based on diketonate ligands in which the lower triplet energies of the ligands result in emission from the (1)D(2) level only. At longer wavelengths, near-infrared luminescence arising from the (1)D(2) emissive level is observed with lifetimes (in both the solid state and solution) being in the range 50-110 ns. For both Er(iii) complexes, luminescence at 1530 nm occurs following UV excitation of ligand-centred transitions. In CH(2)Cl(2) both complexes gave dual-exponential luminescence, with the major component having a lifetime characteristic of an intact Er(iii) complex (approximately 1.5 micros) and the minor component being much shorter lived (0.2-0.5 micros), suggestive of a species in which a ligand is partially detached and the metal is solvated, with the two forms interconverting slowly. This behaviour is consistent with the steric congestion and long M-N(pyridyl) bonds that were observed in [Er(L(1))(2)(NO(3))]. In the solid state both Er(iii) complexes gave very weak luminescence, which could be fitted to a single exponential decay with a lifetime similar to the longer-lived of the solution components.     

Rhabditis (Rhabditis) freitasi sp.n. and Rhabditis (Rhabditis) costai sp.n. (Nematoda-Rhabditidae) isolated from bovine otitis

The author described two new species of Nematoda-Rhabditidae collected from the auditory meatus of catle with ear infection: Rhabditis (Rhabditis) freitasi sp.n. from Formosa county in the state of Goiás and Rhabditis (Rhabditis) costai sp.n. from Sert?ozinho county in the state of S?o Paulo.     

Lp(a) interactions.

In this report, we have summarized our recent studies on lipoprotein(a) (Lp(a)) and its interactions with apolipoprotein B-containing lipoproteins (ApoB-Lp). These findings implicate the kringle-4-like domains of Apo(a) in the binding of Lp(a) to other ApoB-Lp and point to proline as important in this interaction. Other studies have indicated that Lp(a) interacts with the subendothelial extracellular matrix (ECM) and that Lp(a) is inversely related to plasma triglycerides. Since Apo(a) also has an affinity for ApoB-Lp, enhanced binding of Apo(a) to the arterial wall could increase the accumulation of LDL in the matrix and thus promote the development of cardiovascular disease.     

Redescription of Monhystrella parvella (Filipjev) comb.n. (Nematoda, Monhysteridae)

The type of material of Monhystrella parvella (Filipjev, 1931) comb.n. from Abyssinia (Ethiopia) is redescribed and figured in detail. Data on the genital system and the ontogeny of this species are given. Monhystera filiformis sensu Gerlach, 1951 nec Bastian, 1865 of the Black Sea at Pomorie (Bulgaria) is synonymised with M. parvella . The Black Sea specimens have a shorter pharynx, a longer tail and differ also from the Abyssinian specimens in the shape of the tail and the spinneret outlet.     

Chromatin models. Thermal denaturation studies of (Lysx, Leuy)n-and (Lys)n(Leu)m-DNA complexes.

The structural transitions of (Lysx, Leuy)n-DNA and (Lysx)n(Leuy)m-DNA complexes have been studied by thermal denaturation utilizing simultaneous absorption and circular dichroism (CD) measurements [R. Mandel and G.D. Fasman (1974), Biochem. Biophys. Res. Commun. 59, 672]. These complexes are used as models for nucleohistones. At amino acid/nucleotide ratios r less than 1, the copolymers bind to DNA in a ratio of one amino acid residue per nucleotide, and such binding stabilizes the DNA double helix against thermal denaturation relative to the unbound regions. The leucine residues in the copolymers stabilize the bound portion of the complex against thermal denaturation but to a lesser degree than does poly(L-lysine). This study confirms the hypothesis that absorption melting profiles reflect only the change in secondary structure (helix-coil transition) of DNA. It was found that, in the absence of a higher ordered structure (condensed), the CD melting profile also reflects this same conformational transition, and the melting temperatures, Tm, in CD are equal to those in absorption. However, when a higher ordered structure (tertiary) exists in the complex, then the CD melting profile will be dominated by the structural transitions related to the melting of the higher ordered asymmetric structure in the condensed state, followed by the melting of the secondary structure. Under such circumstances, the Tm obtained from absorption may be slightly different from that of the CD, since only the secondary structural changes are being reflected in absorption. The relevance of these studies to the structure of chromatin is discussed.     

Polypeptide models of collagen. Solution properties of (Gly-Pro-Sar)n and (Gly-Sar-Pro)n.

Our studies on the solution conformation of (Gly-Pro-Sar)_n and (Gly-Sar-Pro)_n synthesized as polypeptide models for collagen are reported. It is found that, while (Gly-Pro-Sar)_n exists in ordered triple-helical conformation, (Gly-Sar-Pro)_n remains as a disordered random coil in water. Addition of certain helix-promoting solvents seems to generate order in (Gly-Sar-Pro)_n.     

The status of Phaiophleps lyckholmi (Dusen) R. G. Foster (Iridaceae)

An examination of the south Patagonian and Fuegian plant, Phaiophleps lyckholmi (Dusén) R. C. Foster, shows that it can be distinguished from the more widespread P. biflora (Thunb.) R. C. Foster by its leaf anatomy and perianth colour; these taxa can also be separated on the lengths of the peduncle and filament-tube, and on the shape of the perianth tube, although there is some overlap in these features. Because of the intermediates it is proposed that the two taxa be recognized as subspecies– P. biflora subsp. biflora , occupying grassland and dwarf-shrub communities at altitudes below 700 (-1000) m, reaches north to c. 46^o S latitude in Patagonia, while P. biflora subsp. lyckholmi (Dusén) D. M. Moore Stat. nov., is restricted to open habitats above (150-) 1050 m in Tierra del Fuego and Patagonia south of 48^o 50's latitude.     

Specific and dual antagonists of alpha(4)beta(1) and alpha(4)beta(7) integrins.

N-(3,5-Dichlorophenylsulfonyl)-(R)-thioprolyl biarylalanine 10a has been identified as a potent and specific antagonist of the alpha(4)beta(1) integrin. Altering the configuration of thioproline from R to S led to a series of dual antagonists of alpha(4)beta(1) and alpha(4)beta(7), and the N-acetyl analogue 8b was found to be the most potent dual antagonist. A binding site model for alpha(4)beta(1) and alpha(4)beta(7) is proposed to explain the structure-activity relationship.     

1H NMR study of the binding of Bis(acridines) to d(AT)5.d(AT)5. 1. Mode of binding

1H NMR has been used to investigate the mode of binding to d(AT)5.d(AT)5 of a series of bis(acridine) derivatives connected by different types of linker chains. The length and character (ionic, aliphatic, rigid, and flexible) of the linker chains are found to have a profound effect on the binding of these derivatives to the DNA. Bis(acridine) derivatives with linker chains shorter than 9 A monointercalate under the conditions used in the NMR study, whereas those bis(acridines) with chains of 9.8 A or longer bisintercalate. We find no evidence for the violation of the so-called neighbor exclusion principle. Although all of the bis(acridines) contain the same chromophores, their NMR spectra clearly demonstrate that they form complexes with d(AT)5.d(AT)5 which have different structures. This emphasizes the important effect that the linker chain has on the structure of the intercalation complex.     

铁线莲属威灵仙组修订(续)

对铁线莲属铁线莲亚属 Clematis subgen. Clematis 中的欧洲铁线莲 C. vitalba L.演化干的原始群威灵仙组sect. Clematis 进行了全面修订,确定此组共含有73种和45变种。写出了威灵仙组的分类学简史及地理分布;对威灵仙组中各亚组的亲缘和主要区别特征以及铁线莲亚属欧洲铁线莲演化干中各群的亲缘关系进行了讨论。将威灵仙组分为5个亚组,写出了分亚组检索表和各亚组的分种检索表,以及各种植物的形态描述、地理分布、生长环境等,并附有多幅插图。在5亚组中,欧洲铁线莲亚组     

Dissimilatory Fe(III) and Mn(IV) reduction.

The oxidation of organic matter coupled to the reduction of Fe(III) or Mn(IV) is one of the most important biogeochemical reactions in aquatic sediments, soils, and groundwater. This process, which may have been the first globally significant mechanism for the oxidation of organic matter to carbon dioxide, plays an important role in the oxidation of natural and contaminant organic compounds in a variety of environments and contributes to other phenomena of widespread significance such as the release of metals and nutrients into water supplies, the magnetization of sediments, and the corrosion of metal. Until recently, much of the Fe(III) and Mn(IV) reduction in sedimentary environments was considered to be the result of nonenzymatic processes. However, microorganisms which can effectively couple the oxidation of organic compounds to the reduction of Fe(III) or Mn(IV) have recently been discovered. With Fe(III) or Mn(IV) as the sole electron acceptor, these organisms can completely oxidize fatty acids, hydrogen, or a variety of monoaromatic compounds. This metabolism provides energy to support growth. Sugars and amino acids can be completely oxidized by the cooperative activity of fermentative microorganisms and hydrogen- and fatty-acid-oxidizing Fe(III) and Mn(IV) reducers. This provides a microbial mechanism for the oxidation of the complex assemblage of sedimentary organic matter in Fe(III)- or Mn(IV)-reducing environments. The available evidence indicates that this enzymatic reduction of Fe(III) or Mn(IV) accounts for most of the oxidation of organic matter coupled to reduction of Fe(III) and Mn(IV) in sedimentary environments. Little is known about the diversity and ecology of the microorganisms responsible for Fe(III) and Mn(IV) reduction, and only preliminary studies have been conducted on the physiology and biochemistry of this process.     

1H NMR study of the binding of bis(acridines) to d(AT)5.d(AT)5. 2. Dynamic aspects

Measurements of the 1H NMR spectra and relaxation rates were used to study the dynamic properties of 9-aminoacridine (9AA) and four bis(acridine) complexes with d(AT)5.d(AT)5. The behavior of the 9AA (monointercalator) and that of C8 (bisintercalator containing an eight-carbon atom linker chain) are entirely similar. For both compounds, the lifetime of the drug in a particular binding site is 2-3 ms at approximately 20 degrees C, and neither affects the A.T base pair opening rates. The complex with C10 (bisintercalator containing a 10-carbon atom linker chain) is slightly more stable than the C8 complex since its estimated binding site lifetime is 5-10 ms at 29 degrees C. Base pairs adjacent to the bound C10 are destabilized, relative to free d(AT)5.d(AT)5, but other base pairs in the C10 complex are little affected. Bis(acridine) pyrazole (BAPY) and bis(acridine) spermine (BAS) considerably stabilize those base pairs that are sandwiched between the two acridine chromophores, but in the BAS complex proton exchange from the two flanking base pairs appears to be accelerated, relative to free d(AT)5.d(AT)5. The lifetime of these drugs in specific binding sites is too long (>10 ms) to be manifested in increased line widths, at least up to 41 degrees C. An important conclusion from this study is that certain bisintercalators rapidly migrate along DNA, despite having large binding constants (K>10(6) M-1). For C8 and C10 complexes, migration rates are little different from those deduced for 9AA. The rigid linker chain in BAPY and the charge interactions in BAS retard migration of these two bisintercalators. These results provide new parameters that are useful in understanding the biochemical and biological properties of these and other bisintercalating drugs.     

Block oligopeptides (L-lysyl)m-(L-alanyl)n-L-Tyrosyl-(L-Alanyl)n-(L-Lysyl)m. II. Circular dichroism and pulsefluorimetry conformational studies

The conformation of chromatographically pure block oligopeptides (L -lysyl)_m-(L -alanyl)_n- L -tyrosyl-(L -alanyl)_n-(L -lysyl)_m with n = 3 and m = 6 or 3 is investigated. By circular dichroism it is shown that these peptides may exhibit a partially α-helical structure depending upon pH, ionic strength, solvent, and temprerature. An attempt is made to describe the helical content of these small peptides by utilizing the data obtained on high-molecular-weight poly(L -lysine). By measurement of the quantum yield and the decays of the peptides fluorescence, it is shown that, in aqueous solution, at neutral pH, the fluorescence of the peptides is quenched by interactions with the peptide carbonyl groups. The decays are multiexponential, which shows the presence of several conformations of the phenolic chromophore relative to the peptide chain. The addition of methanol, which induced the helix formation, decreases the quenching of the fluorescence and the multiexponential character of the decays. In presence of sodium hydroxide, which further increases the helical content of the peptides, a dynamic quenching occured that can be attributed to interactions between the phenol hydroxyl group of tyrosine (ith residue) and the ε-amino groups of the (i+4)th and (i -4)th lysyl residues.     

Protonated polynucleotide structures. IX. Disproportionation of poly (G)-poly (C) in acid medium

The interaction between poly (G) and poly (C) was investigated in neutral and acid medium by optical methods. Three main points arise from this investigation. (1) The formation of poly (G)·poly (C) was complete only above an ionic strength of about 0.6M [Na⁺]. Lowering the ionic strength increased the amounts of free poly (G) and free poly (C) that could be detected. (2) When titrating towards acid pH values a transition took place which was characterized by potentiometry, mixing curves, and circular dichroism: a three-stranded poly (G)·poly (C)·poly (C⁺) complex was formed analogous to the transition observed for the acid titration of poly (I)·poly (C). (3) Even when the poly (G)·poly (C) complex was incompletely formed (at low ionic strength) in neutral medium all poly (C) entered the triple-stranded complex.     

Determinants of ligand binding specificity of the alpha(1)beta(1) and alpha(2)beta(1) integrins.

The alpha(1)beta(1) and alpha(2)beta(1) integrins are cell surface collagen receptors. Cells expressing the alpha(1)beta(1) integrin preferentially adhere to collagen IV, whereas cells expressing the alpha(2)beta(1) integrin preferentially adhere to collagen I. Recombinant alpha(1) and alpha(2) integrin I domains exhibit the same collagen type preferences as the intact integrins. In addition, the alpha(2) integrin I domain binds echovirus 1; the alpha(1) I domain does not. To identify the structural components of the I domains responsible for the varying ligand specificities, we have engineered several alpha(1)/alpha(2) integrin I domain chimeras and evaluated their virus and collagen binding activities. Initially, large secondary structural components of the alpha(2) I domain were replaced with corresponding regions of the alpha(1) I domain. Following analysis in echovirus 1 and collagen binding assays, chimeras with successively smaller regions of alpha(1) I were constructed and analyzed. The chimeras were analyzed by ELISA with several different alpha(2) integrin monoclonal antibodies to assess their proper folding. Three different regions of the alpha(1) I domain, when present in the alpha(2) I domain, conferred enhanced collagen IV binding activity upon the alpha(2) I domain. These include the alpha3 and alpha5 helices and a portion of the alpha6 helix. Echovirus 1 binding was lost in a chimera containing the alphaC-alpha6 loop; higher resolution mapping identified Asn(289) as playing a critical role in echovirus 1 binding. Asn(289) had not been implicated in previous echovirus 1 binding studies. Taken together, these data reveal the existence of multiple determinants of ligand binding specificities within the alpha(1) and alpha(2) integrin I domains.     

Energetics of the B-H transition in supercoiled DNA carrying d(CT)x.d(AG)x and d(C)n.d(G)n inserts.

We have studied the B-H transition in the d(AG)x inserts of varying length under superhelical stress. The new data and previously published results for the d(G)31 insert are treated within a phenomenological model of the B-H transition, making it possible to obtain, for the first time, the energy parameters of the B-H transition in the d(AG)x and d(G)n sequences.