bluuebunny/crossref_metadata_2025 huggingface dataset:
Hydrogen-Bond Networks of Mellitate Anions ([C6(COO)6H6−n]n−) in Salts with Pyridine Derivatives
Authors: Kobayashi Norihito , Naito Toshio , Inabe Tamotsu
Published: July 2003

Single crystals of mellitate anion ([C6(COO)6H6−n]n−) salts with 3-aminopyridinium, [3-NH2C5H4NH+]3[C6(COO)6H33−] (1), 4-methylpyridinium, [4-CH3C5H4NH+]2[CH3C5H4N]2[C6(COO)6H42−] (2), [4-CH3C5H4NH+]2[C6(COO)6H42−]·2CH3OH (3), pyridinium, [C5H5NH+]2[C6(COO)6H42−]·2H2O (4), 3-methylpyridinium, [3-CH3C5H4NH+]2[C6(COO)6H42−] (5), [3-CH3C5H4NH+]5[C6(COO)6H33−][C6(COO)6H42−]·CH3OH (6), and isoquinolinium, [C9H7NH+]2[C6(COO)6H42−]·CH3OH (7), [C9H7NH+]2[C9H7NH0.50.5+][C6(COO)6H3.52.5−]·CH3OH (8) have been structurally characterized. In these crystals, strong hydrogen-bonds between the mellitate anions are formed. Various arrangements that depend on the deprotonation number, n, have been found. All hydrogen-bonds found between the anions are combinations of a carboxy and a carboxylato group. The “triangular hydrogen-bond” unit between the anions, in which three anions are connected by the three hydrogen-bonds to form a triangle, in the salt with n = 3, induces the two dimensional (2-D) sheet self-organizing structure in this crystal. “Dual hydrogen-bond” units between the anions, in which two pairs of the hydrogen-bonds connect the neighboring anions, have been found in the salts with n = 2 or 2.5. The repetition of the co-planer “dual hydrogen-bond” induces the anion one-dimensional (1-D) belt structure, while the combination of the standing and co-planer “dual hydrogen-bond” units induces the 2-D grid structure. These 2-D grids are further linked by hydrogen-bonds to form a channel. In all the salts (n = 3, 2, 2.5), the counter cation molecules are arranged in the space defined by the anion network.
Graph-Theoretical Re-interpretation of NICS Values for Polycyclic Aromatic Hydrocarbons: Naphthalene and Azulene
Authors: Aihara Jun-ichi , Oe Sumio
Published: July 2003

Even for the simplest polycyclic aromatic hydrocarbons, such as naphthalene and azulene, the nucleus-independent chemical shift (NICS) calculated at a ring center does not always represent local aromaticity. NICS reflects currents induced in many cyclic paths in a π-system.
Improved Selectivity for Cu(II) of Methyl-Substituted Poly(pyrazolyl)borates, [HB(3-Mepz)3]− and [B(3-Mepz)4]−, through Steric Contact
Authors: Kitano Tsuyoshi , Sohrin Yoshiki , Hata Yasuo , Wada Hiroki , Hori Takeyoshi , Ueda Kazumasa
Published: July 2003

The separation of first-series transition metal and Cd2+ ions has been studied by solvent extraction using methyl substituted poly(pyrazolyl)borates. These ligands did not extract all of the studied metal ions at a lower pH compared to the parent ligands, and the selectivity was high for Cu(II) and low for Fe(II), although the extracted species were A2M complexes as well (A−: poly(pyrazolyl)borate, M2+: metal ion) for all the four ligands. An examination of the structures of the nine complexes determined the present and related ones, which were previously determined elsewhere, revealed that 3-methyl groups of the pyrazolyl rings are arrayed around a metal ion, and that the distances between the methyl groups are smaller than the sum of van der Waals radii of the methyl groups. This suggests that the interligand contact of 3-methyl groups decreases the stability of the complexes. Since the geometry in the copper complexes with these ligands is square bipyramid, the increase in steric energy caused by the interligand contact seems to be smaller than that for those complexes having similar ionic radii. Moreover, the spin state of the iron complexes with these ligands is high-spin due to interligand contact. Thus, while the interligand contact causes a general decrease in the stability of all the complexes, the effect is smallest for Cu(II) and largest for Fe(II), resulting in a unique selectivity.
A New Type of Neptunyl(VI) Hydroxide which is Topologically Similar to α-UO2(OH)2
Authors: Nakada Masami , Kitazawa Takafumi , Saito Takashi , Wang Junhu , Takeda Masuo , Yamashita Toshiyuki , Saeki Masakatsu
Published: July 2003

A new type of neptunyl(VI) hydroxide α-NpO2(OH)2I which is topologically similar to α-UO2(OH)2 has been synthesized from the thermal decomposition of the orthorhombic type NpO2(OH)2·H2O II. The powder X-ray diffraction patterns and 237Np Mössbauer spectra have shown that properties of α-NpO2(OH)2I are different from those of the reported β-NpO2(OH)2III, which is similar to β-UO2(OH)2.
In Situ Measurement of Aggregate Formation Kinetics of Nickel(II)-Pyridylazoaminophenol Complex at the Heptane-Water Interface by Centrifugal Liquid Membrane Spectrophotometry
Authors: Yulizar Yoki , Watarai Hitoshi
Published: July 2003

Complex formation of nickel(II) with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (HL) and the aggregation of the monomer complex at the heptane-water interface have been kinetically studied by using centrifugal liquid membrane (CLM) spectrophotometry. The interfacial aggregation of ligand in NiL2 complex was observed as the growth of a remarkably intense and narrow absorption band (J-band) at 588 nm, showing a bathochromic shift from the absorption maximum of the monomer complex (569 nm), accompanied by a decrease of the absorbance of the free ligand at 452 nm. The formation of aggregate was initiated when the interfacial concentration of the monomer complex attained the critical aggregation concentration (cac) of 2.4 × 10−10 mol cm−2. The initial formation rate of the interfacial aggregate was proportional to concentrations of both free Ni(II) and free ligand after the attainment of cac. The observed rate constant for the aggregation, 4.1 × 101 M−1 s−1, was smaller than the formation rate constant of NiL2 complex at the interface. A long period observation of the profile of absorbance change showed an oscillation of the interfacial aggregate concentration until all of the ligand was consumed, suggesting a subsequent flocculation of the aggregate in the rotating cell.
Crystal Structures and Magnetic and Gas-Occlusion Properties of Microporous Materials Containing Infinite Chains of Mononuclear Metal (Cu(II), Zn(II), and Ni(II)) Dicarboxylates Unit
Authors: Ohmura Tetsushi , Mori Wasuke , Hasegawa Mari , Takei Tohru , Ikeda Toshiya , Hasegawa Eiko
Published: July 2003

A new series of microporous materials containing infinite chains of a mononuclear metal (Cu(II), Zn(II), Ni(II))-pyridine unit bridged by dicarboxylates (copper(II) terephthalate-pyridine 1a, copper(II) terephthalate-4-phenylpyridine 1b, zinc(II) fumarate-pyridine 2a, zinc(II) terephthalate-pyridine 2b, nickel(II) fumarate-pyridine 3a, and nickel(II) terephthalate-pyridine 3b) have been prepared. These complexes, which have a regular one-dimensional structure, occlude large amounts of gases. The maximum amount of N2 gas is 0.7–10.7 mole per mole of metal(II) salt, indicating the presence of a large number of micropores. A porous structure, which is formed by stacking and self-assembly of the linear metal(II) dicarboxylates, was determined by X-ray crystallography. We have elucidated the paramagnetic properties of 1a, 1b, 3a, and 3b by magnetic measurement (SQUID), whereas 2a and 2b were found to be diamagnetic. The magnetic susceptibilities of 1a and 1b obey the Curie-Weiss law over the range of 70–300 K (θ = −1.4 K and θ = +5.5 K, respectively); the obtained Weiss constants (θ) indicate the existence of small antiferromagnetic interactions (1a) and ferromagnetic interactions (1b). The different magnetic behaviors between 1a and 1b demonstrate that hydrogen bonding between the carboxylate groups and coordinated water molecules plays an important role in determining the bridge geometries and super-exchange interaction between the Cu(II) ions through the Cu–O–C–O–H–O–Cu pathways. In contrast to those of the copper(II) complexes, the magnetic susceptibilities of 3a and 3b obey the Curie law.
One-Pot Speciation Method for Cr(III) and Cr(VI) with APCD/DIBK Extraction System Based on Difference in Rate of Complex Formation
Authors: Honma Yoshiro
Published: July 2003

A simple speciation of chromium oxidation states based only on the difference in reaction rates of Cr(III) and of Cr(VI) has been developed. This speciation, which was carried out in an ammonium 1-pyrrolidinecarbodithioate (APCD)/diisobutyl ketone (DIBK) extraction system, required no sample splitting. At the first extraction, Cr(VI) was extracted into a DIBK phase, and Cr(III) remaining in the sample was extracted secondly after replacement of the phase by fresh DIBK. Inert Cr(III) was extracted directly without the oxidation process. The concentration of chromium in the extract was measured by AAS. In the first extraction, 0.4–0.5% of Cr(III) was extracted and 0.2% of Cr(VI) was carried over to the second extraction. Using artificial seawater, the detection limit (3σ) and the relative standard deviation (n = 5, at 100 μg/L) were 10 μg/L and ca. 4% (concentration factor = 2). Interferences of heavy metal ions were examined; 5-fold cation group (Mn2+, Fe3+, Ni2+, Cu2+ and Zn2+) and 1-fold anion group (VO3−, Mo7O246− and WO42−) exhibited negative errors of 5 and 10% in Cr(III) determination respectively. Validity of the method was checked with the standard reference material JAC-0032 (river water); total chromium was determined as 11.0 μg/L (certified value is 10.1 ± 0.2 μg/L).
Three-Dimensional Zinc(II) Coordination Polymer with Strong Blue Fluorescent Emission Formed by Parallel Interlocking of (4,4) Two-Dimensional Networks
Authors: Wang Yan , Ouyang Xing-Mei , Li Yi-Zhi , Sun Wei-Yin
Published: July 2003

A novel coordination polymer, [Zn(NCS)2(L)2]·2H2O, with strong blue fluorescent emission was prepared by an assembly reaction of 1,2-bis(3-pyridylmethyleneamino)ethane (L) with Zn(ClO4)2 and NaSCN. A crystallographic analysis indicates that the structure of the complex contains (4,4) two-dimensional layers, which interlock each other in parallel to form a three-dimensional framework.
Chiral Fluorescent Labeling Reagent Derived from Rhodamine B for Flurbiprofens
Authors: Matsui Masaki , Higeta Takahiro , Kimura Masahiro , Funabiki Kazumasa , Nakaya Ken-ichi
Published: July 2003

A lactam-type enantiomeric fluorescent labeling reagent was prepared from Rhodamine B. This reagent showed its absorption and emission maxima at λ 557 and 580 nm in an acetonitrile–acetic acid (9:1) mixed solution, respectively. Racemic Flurbiprofens reacted with this reagent to produce diastereomeric esters, which were separated by non-chiral high-performance liquid chromatography (HPLC).
Glycosylation Using Hemiacetal Sugar Derivatives: Synthesis of O-α-d-Rhamnosyl-(1→3)-O-α-d-rhamnosyl-(1→2)-d-rhamnose and O-α-d-Tyvelosyl-(1→3)-O-α-d-mannosyl-(1→4)-l-rhamnose
Authors: Hirooka Motoko , Yoshimura Asako , Saito Izumi , Ikawa Fumio , Uemoto Yoko , Koto Shinkiti , Takabatake Ayano , Taniguchi Aya , Shinoda Yoshika , Morinaga Aya
Published: July 2003

O-α-d-Rhamnopyranosyl-(1→3)-O-α-d-rhamnopyranosyl-(1→2)-d-rhamnopyranose, a repeating trisaccharide of the O-specific polysaccharides (OPSs) of Pseudomonades, and O-α-d-tyvelopyranosyl-(1→3)-O-α-d-mannopyranosyl-(1→4)-l-rhamnopyranose, a trisaccharide composing the OPSs of Salmonella typhi, were synthesized by in-situ activating glycosylation reactions using hemiacetal sugar derivatives. Allyl 2,4-di-O-benzyl-α-d-rhamnopyranoside was prepared via the direct ditritylation of allyl α-d-mannopyranoside. 3-O-Acetyl-2,4-di-O-benzyl-d-rhamnopyranose was used as a precursor for the moiety of d-tyvelose (3,6-dideoxy-d-arabino-hexose, 3,6-dideoxy-d-mannopyranose, 3-deoxy-d-rhamnose) of the salmonella trisaccharide.
Palladium(II)-Catalyzed Michael-Type Hydroarylation of Nitroalkenes Using Aryltins and Sodium Tetraarylborates
Authors: Ohe Toshiyuki , Uemura Sakae
Published: July 2003

A variety of aryltin compounds and sodium tetraarylborates can be employed for Michael-type hydroarylation reactions of nitroalkenes to afford β-arylnitroalkanes in moderate to good yields in the presence of either LiCl, MgCl2, or CaCl2 and a catalytic amount of palladium(II) salt (0.05 molar amount) in acetic acid. Results show that 50–70% of aryl groups out of all in these aryl compounds can be transferred to the products in this hydroarylation. The addition of a catalytic amount (0.05–0.10 molar amount) of a Lewis acid chloride, BiCl3 or SbCl3, much improves the product yield in some cases.
Polymer-Supported Sulfinimidoyl Chlorides: A Convenient Reagent for Oxidation of Alcohols
Authors: Matsuo Jun-ichi , Kawana Asahi , Yamanaka Hiroyuki , Kamiyama Hiroaki
Published: July 2003

Two polymer-supported sulfinimidoyl chlorides, i.e., 4-(N-tert-butylchlorosulfinimidoyl)phenoxymethylpolystyrene (3) and 4-(N-tert-butylchlorosulfinimidoyl)polystyrene (10), were prepared from chloromethylpolystyrene and polystyrene, respectively. Stoichiometric or catalytic oxidation of various primary and secondary alcohols using these polymer-supported sulfinimidoyl chlorides proceeded smoothly, and the corresponding aldehydes and ketones were conveniently prepared in good-to-high yields by simple work-up procedures. The polymer-supported oxidant 10 was recycled repeatedly by chlorination of a used polymer 11 with N-chlorosuccinimide (NCS) after stoichiometric oxidation.
Enhancement of the Efficiency of the Low Temperature Method for Kinetic Resolution of Primary Alcohols by Optimizing the Organic Bridges in Porous Ceramic-Immobilized Lipase
Authors: Sakai Takashi , Hayashi Kyoko , Yano Fumika , Takami Mie , Ino Megumi , Korenaga Toshinobu , Ema Tadashi
Published: July 2003

For the enhancement of enantioselectivity and acceleration of the reaction rate in the lipase-catalyzed resolution of primary alcohols, the use of a very low reaction temperature (−30 °C) and an immobilized lipase on organic bridges-coated porous ceramic support was found to be highly effective. Furthermore, the structure of the organic bridges greatly influenced the temperature effect between ln E and 1/T as well as the reaction rate. Among the organic bridges examined in the resolution of (±)-2-hydroxymethyl-1,4-benzodioxane, the 6-(2-methylpropanoyloxy)hexylsilanetrioxyl bridge was the best choice for both the E value and the reaction rate at −30 °C.
Electrooxidative Conversion of Aldehyde and Ketone Phenylhydrazones into the Methoxy(phenylazo)alkanes
Authors: Okimoto Mitsuhiro , Nagata Yuji , Takahashi Yukio
Published: July 2003

Several aldehyde and ketone phenylhydrazones were converted into the corresponding methoxy(phenylazo)alkane derivatives by electrochemical oxidation in MeOH.
Alkylthio-functionalized Polymers Containing Alternating Phenylene and Thiophenediyl/Bithiophenediyl Repeating Units: the Synthesis and Characterization
Authors: Xu Jingmei , Ng Siu Choon , Chan Hardy Sze On
Published: July 2003

Alkylthio(SR)-functionalized polymers poly(3-alkylthio-2,5-thiophenediyl-1,4-phenylene-alt-4-alkylthio-2,5-thiophenediyl-1,4-phenylene) (P1, alkyl = butyl, octyl and dodecyl) and poly[4,4′-bis(alkylthio)-2,2′-bithiophene-5,5′-diyl-alt-1,4-phenylene] (P2, alkyl = butyl, octyl and dodecyl) have been synthesized by Grignard coupling and FeCl3 oxidation methods, respectively. Spectral measurements indicate that they are highly fluorescent, with quantum yields comparable to those of their alkyl(R)-functionalized analogues, poly(3-alkyl-2,5-thiophenediyl-1,4-phenylene-alt-4-alkyl-2,5-thiophenediyl-1,4-phenylene) (P1′, alkyl = butyl, octyl and dodecyl) and poly(4,4′-dialkyl-2,2′-bithiophene-5,5′-diyl-alt-1,4-phenylene) (P2′, alkyl = butyl, octyl and dodecyl). P1 and P2 are thermally less stable than P1′ and P2′, because of the alkylthio group instead of an alkyl group. Modulated differential scanning calorimetry (MDSC) studies reveal a plasticizing effect exerted by the long side chains on the glass transitions (Tg) of the polymers. The P2 series of polymers exhibit a much higher Tg than the P1 series, ascribable to a greater resistance to segmental rotation in the former structure. A cyclic voltammetric study of polymers indicates that they are n-dopable. When doped by I2 or FeCl3, high doping levels of the polymers can be deduced from the weight change, XPS and elemental analysis, but conductivities are not high.
Optical CO2 Sensor with the Combination of Colorimetric Change of pH Indicator and Internal Reference Luminescent Dye
Authors: Nakamura Naoki , Amao Yutaka
Published: July 2003

A new optical CO2 sensor based on luminescence intensity changes of europium(III) complex, tris(thenoyltrifluoroacetonato)europium(III) dihydrate complex ([Eu(tta)3]) due to the absorption change of pH-indicator dye (thymol blue) with CO2 was developed and its CO2 sensing properties were investigated. The observed luminescence intensity (I) from [Eu(tta)3] at 613 nm increased with increasing the CO2 concentration. The ratio I0/I100, where I0 and I100 represent the detected luminescence intensities from a layer exposed to 100% nitrogen and 100% CO2, respectively, that we takes the sensitivity of the sensor is estimated to be 16.0. The response times of the sensing film were 4.0 s for switching from nitrogen to CO2, and 36 s for switching from CO2 to nitrogen. The signal changes were fully reversible and no hysterisis was observed during the measurements.
Effect of Surface Oxidation of Active Carbon on Ammonia Adsorption
Authors: Liu Chun Yi , Aika Ken-ichi
Published: July 2003

The behavior of ammonia adsorption was studied on various types of surface-treated active carbon (HNO3-AC, H2SO4-AC, HCl-AC, NaOH-AC, CuO-AC, and H2-AC) under 0–75 kPa and 323–473 K. Amount of ammonia adsorption on active carbon was increased by the surface oxidation through acid treatment or metal nitrate decomposition. It was decreased by the hydrogen treatment at 1173 K. The equilibrium amount of ammonia adsorption was found to relate with the amount of surface organic oxygen. Ammonia adsorption was analyzed through the isotherm and classified into three types: (1) strong adsorption relating to surface organic oxygen content and being independent of pressure, (2) weak adsorption relating to surface organic oxygen content and depending upon the pressure, (3) van der Waals adsorption. The model well represented the data, and the average relative error was 10%. When the samples are assumed to be used for ammonia separation with temperature swing adsorption method (323–473 K, 40 kPa), H2SO4-treated active carbon was found to have the highest ammonia separation capacity (2.58 mmol g−1).
Synthesis of Nanocrystalline BP via Benzene-Thermal Co-reduction of PCl3 and BBr3
Authors: Gu Yunle , Chen Luyang , Qian Yitai , Zhang Wanqun
Published: July 2003

Nanocrystalline boron phosphide (BP) powders 10 to 40 nm in size have been synthesized via a sodium co-reduction of PCl3 and BBr3 in benzene at 300 °C. X-ray diffraction data show a cubic pattern with lattice constant a = 4.539 Å.
Comparative Studies of the Formation of Surface Relief Grating. Amorphous Molecular Material vs Vinyl Polymer
Authors: Ando Hiroyuki , Takahashi Toru , Nakano Hideyuki , Shirota Yasuhiko
Published: July 2003

Comparative studies have been performed on the formation of surface relief grating (SRG) using an amorphous molecular material, 4-[di(biphenyl-4-yl)amino]azobenzene (DBAB), and a vinyl polymer containing DBAB as a pendant chromophore. It was found that SRG was formed more rapidly for the photochromic amorphous molecular material than for the corresponding vinyl polymer.
Use of nucleotide analogs by class I and class II CCA-adding enzymes (tRNA nucleotidyltransferase): Deciphering the basis for nucleotide selection
Authors: CHO HYUNDAE D. , OYELERE ADEGBOYEGA K. , STROBEL SCOTT A. , WEINER ALAN M.
Published: July 2003

We explored the specificity and nature of the nucleotide-binding pocket of the CCA-adding enzyme (tRNA nucleotidyltransferase) by using CTP and ATP analogs as substrates for a panel of class I and class II enzymes. Overall, class I and class II enzymes displayed remarkably similar substrate requirements, implying that the mechanism of CCA addition is conserved between enzyme classes despite the absence of obvious sequence homology outside the active site signature sequence. CTP substrates are more tolerant of base modifications than ATP substrates, but sugar modifications prevent incorporation of both CTP and ATP analogs by class I and class II enzymes. Use of CTP analogs (zebularine, pseudoisocytidine, 6-azacytidine, but not 6-azauridine) suggests that base modifications generally do not interfere with recognition or incorporation of CTP analogs by either class I or class II enzymes, and that UTP is excluded because N-3 is a positive determinant and/or O-4 is an antideterminant. Use of ATP analogs (N6-methyladenosine, diaminopurine, purine, 2-aminopurine, and 7-deaza-adenosine, but not guanosine, deoxyadenosine, 2′-O-methyladenosine, 2′-deoxy-2′-fluoroadenosine, or inosine) suggests that base modifications generally do not interfere with recognition or incorporation of ATP analogs by either class I or class II enzymes, and that GTP is excluded because N-1 is a positive determinant and/or the 2-amino and 6-keto groups are antideterminants. We also found that the 3′-terminal sequence of the growing tRNA substrate can affect the efficiency or specificity of subsequent nucleotide addition. Our data set should allow rigorous evaluation of structural hypotheses for nucleotide selection based on existing and future crystal structures.
Stereospecificity of short Rev-derived peptide interactions with RRE IIB RNA
Authors: LITOVCHICK ALEXANDER , RANDO ROBERT R.
Published: July 2003

The essential HIV-1 regulatory protein Rev binds to the Rev responsive element (RRE) of the HIV-1 mRNA. A short α-helical peptide derived from Rev (Rev 34–50) and a truncated form of the RRE sequence (RRE IIB) provide a useful in vitro system to study the interactions between Rev and RRE. The current studies focus on evaluating the specificity of the binding interactions between Rev 34–50 and RRE IIB. The binding of L- and D-Rev peptides to natural and enantiomeric RRE IIB RNA was studied by fluorescence spectroscopy. D-Rev and L-Rev peptides bind to RRE IIB with similar affinities. CD measurements are consistent with a nonhelical, probably β-hairpin, conformation for D-Rev in the complex. The binding affinities of D/L Rev peptides to L-RRE IIB RNA are also similar to those with natural D-RRE IIB. Furthermore, the conformations of L- and D-peptides when bound to L-RRE are reciprocal to the conformations of these peptides in complex with D-RRE. RNA footprinting studies show that L- and D-Rev peptides bind to the same site on RRE IIB. Our results demonstrate lack of stereospecificity in RRE RNA–Rev peptide interactions. However, it is quite possible that the interactions between full-length Rev protein and RRE are highly specific.
Perturbation of transcription elongation influences the fidelity of internal exon inclusion in Saccharomyces cerevisiae
Authors: HOWE KENNETH JAMES , KANE CAROLINE M. , ARES MANUEL
Published: July 2003

Unknown mechanisms exist to ensure that exons are not skipped during biogenesis of mRNA. Studies have connected transcription elongation with regulated alternative exon inclusion. To determine whether the relative rates of transcription elongation and spliceosome assembly might play a general role in enforcing constitutive exon inclusion, we measured exon skipping for a natural two-intron gene in which the internal exon is constitutively included in the mRNA. Mutations in this gene that subtly reduce recognition of the intron 1 branchpoint cause exon skipping, indicating that rapid recognition of the first intron is important for enforcing exon inclusion. To test the role of transcription elongation, we treated cells to increase or decrease the rate of transcription elongation. Consistent with the “first come, first served” model, we found that exon skipping in vivo is inhibited when transcription is slowed by RNAP II mutants or when cells are treated with inhibitors of elongation. Expression of the elongation factor TFIIS stimulates exon skipping, and this effect is eliminated when lac repressor is targeted to DNA encoding the second intron. A mutation in U2 snRNA promotes exon skipping, presumably because a delay in recognition of the first intron allows elongating RNA polymerase to transcribe the downstream intron. This indicates that the relative rates of elongation and splicing are tuned so that the fidelity of exon inclusion is enhanced. These findings support a general role for kinetic coordination of transcription elongation and splicing during the transcription-dependent control of splicing.
A structural linkage between the dimerization and encapsidation signals in HIV-2 leader RNA
Authors: LANCHY JEAN-MARC , IVANOVITCH JOHN D. , LODMELL J. STEPHEN
Published: July 2003

The 5′ untranslated leader region of retroviral RNAs contains noncoding information that is essential for viral replication, including signals for transcriptional transactivation, splicing, primer binding for reverse transcription, dimerization of the genomic RNA, and encapsidation of the viral RNA into virions. These RNA motifs have considerable structural and functional overlap. In this study, we investigate the conformational dynamics associated with the use and silencing of a sequence in HIV-2 RNA that is involved in genomic RNA dimerization called stem–loop 1 (SL1) and its relationship with a flanking sequence that is known to be important for encapsidation of viral RNAs. We demonstrate that a long-distance intramolecular interaction between nucleotides located upstream of the primer-binding site domain and nucleotides encompassing the Gag translation start codon functionally silences SL1 as a dimerization element. This silencing can be relieved by mutation or by hybridization of an oligonucleotide that disrupts the long-distance interaction. Furthermore, we identify a palindrome within the packaging/encapsidation signal Ψ (just 5′ of SL1) that can either serve as an efficient dimerization signal itself, or can mediate SL1 silencing through base pairing with SL1. These results provide a tangible link between the functions of genomic RNA dimerization and encapsidation, which are known to be related, but whose physical relationship has been unclear. A model is proposed that accounts for observations of dimerization, packaging, and translation of viral RNAs during different phases of the viral replication cycle.
A common speed limit for RNA-cleaving ribozymes and deoxyribozymes
Authors: BREAKER RONALD R. , EMILSSON GAIL MITCHELL , LAZAREV DENIS , NAKAMURA SHINGO , PUSKARZ IZABELA J. , ROTH ADAM , SUDARSAN NARASIMHAN
Published: July 2003

It is widely believed that the reason proteins dominate biological catalysis is because polypeptides have greater chemical complexity compared with nucleic acids, and thus should have greater enzymatic power. Consistent with this hypothesis is the fact that protein enzymes typically exhibit chemical rate enhancements that are far more substantial than those achieved by natural and engineered ribozymes. To investigate the true catalytic power of nucleic acids, we determined the kinetic characteristics of 14 classes of engineered ribozymes and deoxyribozymes that accelerate RNA cleavage by internal phosphoester transfer. Half approach a maximum rate constant of ~1 min−1, whereas ribonuclease A catalyzes the same reaction ~80,000-fold faster. Additional biochemical analyses indicate that this commonly encountered ribozyme “speed limit” coincides with the theoretical maximum rate enhancement for an enzyme that uses only two specific catalytic strategies. These results indicate that ribozymes using additional catalytic strategies could be made that promote RNA cleavage with rate enhancements that equal those of proteins.
Ribozyme speed limits
Authors: EMILSSON GAIL MITCHELL , NAKAMURA SHINGO , ROTH ADAM , BREAKER RONALD R.
Published: July 2003

The speed at which RNA molecules decompose is a critical determinant of many biological processes, including those directly involved in the storage and expression of genetic information. One mechanism for RNA cleavage involves internal phosphoester transfer, wherein the 2′-oxygen atom carries out an SN2-like nucleophilic attack on the adjacent phosphorus center (transesterification). In this article, we discuss fundamental principles of RNA transesterification and define a conceptual framework that can be used to assess the catalytic power of enzymes that cleave RNA. We deduce that certain ribozymes and deoxyribozymes, like their protein enzyme counterparts, can bring about enormous rate enhancements.
Contamination during removal of cement in revision hip arthroplasty
Authors: Nogler M. , Lass-Flörl C. , Wimmer C. , Mayr E. , Bach C. , Ogon M.
Published: July 2003

Instruments used in surgery which rotate or vibrate at a high frequency can produce potentially contaminated aerosols. Such tools are in use in cemented hip revision arthroplasties. We aimed to measure the extent of the environmental and body contamination caused by an ultrasound device and a high-speed cutter.

On a human cadaver we carried out a complete surgical procedure including draping and simulated blood flow contaminated with Staphylococcus aureus (ATCC 12600). After cemented total hip arthroplasty, we undertook repeated extractions of cement using either an ultrasound device or a high-speed cutter. Surveillance cultures detected any environmental and body contamination of the surgical team.

Environmental contamination was present in an area of 6 x 8 m for both devices. The concentration of contamination was lower for the ultrasound device. Both the ultrasound and the high-speed cutter contaminated all members of the surgical team. The devices tested produced aerosols which covered the whole operating theatre and all personnel present during the procedure. In contaminated and infected patients, infectious agents may be present in these aerosols. We therefore recommend the introduction of effective measures to control infection and thorough disinfection of the operating theatre after such procedures.
Tissue reactions adjacent to well-fixed hydroxyapatite-coated acetabular cups
Authors: Røkkum M. , Reigstad A. , Johansson C. B. , Albrektsson T.
Published: July 2003

Ten acetabular cups coated with hydroxyapatite (HA) had originally been inserted in five primary and five revision total hip replacements. The thickness of the HA was 155 ± 35 μm. The cups, which were well-fixed, were retrieved, with their adherent tissue, at reoperation after 0.3 to 5.8 years because of infection (five hips), wear of polyethylene (three hips), and instability (two hips).

Undecalcified sections showed a direct contact between bone and osteoid-like tissue which had formed directly onto the HA coating. The area within the threads and their mirror images, as well as the implant-tissue interfaces consisted of similar amounts of bone and soft tissue. Degradation of HA was seen in all hips. The mean thickness of the remaining HA coating was 97 μm (95% CI 94 to 101). The metal interface comprised 66% HA. The HA-tissue interface contained more bone than soft tissue (p = 0.001), whereas the metal-tissue interface included more soft tissue than bone (p = 0.019). Soft tissue at the implant interface and poor replacement of HA by bone may interfere with long-term fixation.
Synovial impingement in the ankle
Authors: Molloy S. , Solan M. C. , Bendall S. P.
Published: July 2003

Inversion injuries of the ankle are common and most are managed adequately by functional treatment. A significant number will, however, remain symptomatic.

Synovial impingement is one cause of continuing pain. This condition is often difficult to diagnose because the physical signs and investigations are non-specific. If the diagnosis is made, treatment by arthroscopic debridement has been shown to be highly effective. Our aim was to describe a new physical sign to help in the diagnosis of anterolateral synovial impingement in the ankle.

A cadaver dissection demonstrated the anatomical basis for the physical sign and a prospective clinical study involving 73 patients showed that the lateral synovial impingement test had a sensitivity of 94.8% and a specificity of 88%.

We describe the test and conclude that this physical sign will be of use to practitioners treating patients with chronic pain in the ankle after injury.
Early results of the Souter-Strathclyde unlinked total elbow arthroplasty in patients with osteoarthritis
Authors: Espag M. P. , Back D. L. , Clark D. I. , Lunn P. G.
Published: July 2003

We have carried out a retrospective review of 11 Souter-Strathclyde primary total elbow arthroplasties in ten patients with osteoarthritis, over a period of nine years. The diagnosis was primary osteoarthritis in nine elbows and post-traumatic arthritis in two. The mean follow-up was 68 months (15 to 117).

Although no patient was symptomatic, radiological review revealed evidence of loosening affecting three humeral and two ulnar components, one of which subsequently failed and was revised at 97 months. There were no dislocations, deep infections or mechanical failures. Complications included two superficial wound infections and two neurapraxias of the ulnar nerve which resolved.

This study shows that the unlinked Souter-Strathclyde total elbow arthroplasty can be considered for patients with osteoarthritis and gives good symptomatic relief and improvement in function.
Role of abrasion of the femoral component in revision knee arthroplasty
Authors: Siddique M. S. , Rao M. C. , Deehan D. J. , Pinder I. M.
Published: July 2003

We carried out 60 revision procedures for failed porous coated anatomic total knee replacements in 54 patients, which were divided into two groups. The 14 knees in group I had a well-fixed femoral component at surgery which was retained, and in the 46 knees in group II both tibial and femoral components were loose and were revised using a variety of implants. Our review comprised clinical and radiological assessment.

A total of 13 knees required a second revision. Six (42%) in group I failed very early (mean 2.1 years) when compared with seven (15%) in group II (mean 6.8 years). Failure was due to wear of the polyethylene insert by the abraded, retained femoral component (crude odds ratio 4.07; 95% CI 1.07 to 15.5). We recommend a complete change of primary bearing surfaces at the time of revision of an uncemented total knee replacement in order to prevent early wear of polyethylene.
A femoral component with proximal HA coating
Authors: Skinner J. A. , Kroon P. O. , Todo S. , Scott G.
Published: July 2003

We describe the survival at ten years of 100 femoral components of the Freeman hip prosthesis. It is proximally hydroxyapatite (HA)-coated and was fixed without cement. Radiological assessment identified radiolucent lines (RLLs) and lytic lesions and was used to measure migration.

The criterion of failure was revision or impending revision for aseptic femoral loosening. No femoral components were revised or are awaiting revision for aseptic loosening, giving 100% survival at ten years (95% confidence interval, 95.7 to 100), although 59 were at risk at ten years. Two components were revised for fracture of a ceramic head with damage to the trunnion. Although well fixed in each, for survival analysis we evaluated the hip as if the patient had died.

Twelve acetabular components were revised and at each operation the femoral component was found to be well fixed, was not disturbed and remained in the survival analysis. Three patients were lost to follow-up, and 12 died with well-functioning prostheses. Radiologically, all except one of the components appeared to be well fixed with no RLLs and no lytic lesions at the latest follow-up. The mean vertical migration was 0.4 mm at one year, 0.8 mm at two years and 1.4 mm at ten years. One component had migrated 7.6 mm at ten years (2.1 mm in year 1) and developed RLLs in Gruen zones I and II. The symptoms, however, were only minor and revision was not indicated.

Our study has shown that proximal HA coating gives effective fixation for a femoral component.
Iliosacral screw fixation of the posterior pelvic ring using local anaesthesia and computerised tomography
Authors: Ziran B. H. , Smith W. R. , Towers J. , Morgan S. J.
Published: July 2003

Various techniques have been used for the fixation of the posterior pelvis, each with disadvantages specific to the technique. In this study, a new protocol involving the placement of posterior pelvic screws in the CT suite is described and evaluated.

A total of 66 patients with unstable pelvic ring injuries was stabilised under local anaesthesia with sedation. The mean length of time for the procedure was 26 minutes per screw. There were no technical difficulties or misplaced screws and no cases of infection or nonunion. All patients stated that they would choose to have the CT scan procedure again rather than a procedure requiring general anaesthesia. The charges for the procedure were approximately £1840 ($2800) per operation. CT-guided placement of iliosacral screws is a safe, feasible, and cost-effective alternative to radiologically-guided placement in the operating theatre in selected patients.
Doxycycline inhibits bone resorption by human interface membrane cells from aseptically loose hip replacements
Authors: Ong S. M. , Taylor G. J. S.
Published: July 2003

Matrix metalloproteinases (MMPs) may have a role in the process of aseptic loosening. Doxycycline has been shown to inhibit MMPs. Our aim was to investigate the potential pharmacological effect of doxycycline on aseptic loosening. We used radiolabelled mouse calvariae cultured with human interface membrane cells from aseptically loosened hips.

Bone resorption was confirmed in this model. The effect of doxycycline was assessed by culturing dead radiolabelled bone discs with cells from the interface membrane with doxycycline. The control group consisted of the same culture system without doxycycline. Supernatant 45calcium and the total 45calcium remaining in the bone discs at the completion of the culture were used to measure osteolysis.

We found that doxycycline can inhibit osteolysis at the interface membrane of aseptically loosened hips. This may have therapeutic implications for the treatment of patients with aseptic loosening of total joint replacements.
Diagnosis of a tear of the tibiofibular syndesmosis
Authors: Takao M. , Ochi M. , Oae K. , Naito K. , Uchio Y.
Published: July 2003

In 52 patients we compared the accuracy of standard anteroposterior (AP) radiography, mortise radiography and MRI with arthroscopy of the ankle for the diagnosis of a tear of the tibiofibular syndesmosis. In comparison with arthroscopy, the sensitivity, specificity and accuracy were 44.1%, 100% and 63.5% for standard AP radiography and 58.3%, 100% and 71.2% for mortise radiography. For MRI they were 100%, 93.1% and 96.2% for a tear of the anterior inferior tibiofibular ligament and 100%, 100% and 100% for a tear of the posterior inferior tibiofibular ligament. Standard AP and mortise radiography did not always provide a correct diagnosis. MRI was useful although there were two-false positive cases. We suggest that arthroscopy of the ankle is indispensable for the accurate diagnosis of a tear of the tibiofibular syndesmosis.
The role of the posterior cruciate ligament in total knee replacement
Authors: Misra A. N. , Hussain M. R. A. , Fiddian N. J. , Newton G.
Published: July 2003

We randomised 129 knees which were to be replaced using a standard posterior-cruciate-ligament (PCL)-retaining cemented total knee replacement into two groups. In one the PCL was retained in the normal way and in the other it was resected. They were well matched, with a predominance of women, and a mean age of 67 years.

There was no statistically significant difference in the Hospital for Special Surgery scores at a mean of 57 months (56 to 60) between the two groups although 21 patients (24 knees) were lost to follow-up. Relief from pain, correction of deformity, range of movement, stability and strength were comparable in both. Radiological assessment showed femoral rollback in approximately 20% of knees with a slightly higher incidence in the PCL-resected group. There was no significant loosening detected in either group at review at two years.

At five years, one knee in the PCL-retained group had been revised because of infection and one patient in each group was awaiting revision for loosening.

Our findings have shown no significant difference in the five-year results for a PCL-retaining total knee replacement if the PCL is excised or preserved. This suggests two important points. First, the PCL is not functional in most patients with a total knee replacement even when retained. Secondly, patients with an excised PCL show a good result with a PCL-retaining implant, thereby questioning the need for a posterior stabilised design in such a situation.
Treatment of primary degenerative arthritis of the elbow by ulnohumeral arthroplasty
Authors: Phillips N. J. , Ali A. , Stanley D.
Published: July 2003

Between 1990 and 1996 we performed 20 consecutive ulnohumeral arthroplasties for primary osteoarthritis of the elbow.

The outcome was assessed using the Disabilities of Arm, Shoulder and Hand Score (DASH) and the Mayo Elbow Performance Score (MEPS) at a mean follow-up of 75 months (58 to 132). There were excellent or good results in 17 elbows (85%) using the DASH score and in 13 (65%) with the MEPS (correlation coefficient 0.79). The mean fixed flexion deformity had improved by 10° and the range of flexion by a mean of 20°.

In 16 elbows (80%) the benefits of surgery had been maintained, and of 16 patients working at the time of operation, 12 (75%) had returned to the same job.

There was no correlation between radiological recurrence of degenerative changes and the amount of fixed flexion deformity, the flexion arc, or the elbow scores.
Regulation of expression of α-smooth muscle actin in cells of Dupuytren’s contracture
Authors: Hindman H. B. , Marty-Roix R. , Tang J-B. , Jupiter J. B. , Simmons B. P. , Spector M.
Published: July 2003

Our aims were to describe the distribution of α-smooth muscle actin (SMA)-containing cells in Dupuytren’s tissue in vivo and to determine the effects of selected agents in regulating the expression of SMA in Dupuytren’s cells in vitro.

In selected hypercellular zones of Dupuytren’s nodules up to 40% of the cells contained SMA, as shown by immunohistochemistry. A lower percentage (20%) of SMA-containing cells was found in regions of lower cellularity. A notable finding was that treatment in vitro of Dupuytren’s cells with platelet-derived growth factor significantly reduced the content of SMA. Cells from the same patients showed a significant increase in expression of SMA in response to treatment with transforming growth factor, which confirmed recent findings. In addition, interferon-γ, which has been previously used as a treatment for Dupuytren’s disease in a clinical study, had no reproducible effect on the expression of this actin isoform. Our findings are of significance for the conservative management of contractures.
Strain on the human sciatic nerve in vivo during movement of the hip and knee
Authors: Fleming P. , Lenehan B. , O’Rourke S. , McHugh P. , Kaar K. , McCabe J. P.
Published: July 2003

Injuries to the sciatic nerve are an occasional complication of surgery to the hip and acetabulum, and traction is frequently the causative mechanism. In vitro and animal experiments have shown that increased tensile strain on peripheral nerves, when applied for prolonged periods, impairs nerve function.

We have used video-extensometry to measure strain on the human sciatic nerve during total hip replacement (THR). Ten consecutive patients with a mean age of 72 years undergoing primary THR by the posterior approach were recruited, and strains in the sciatic nerve were measured in different combinations of flexion and extension of the hip and knee, before dislocation of the hip. Significant increases (p = 0.02) in strain in the sciatic nerve were observed in flexion of the hip and extension of the knee. The mean increase was 26% (19% to 30%). In animal studies increases of this magnitude have been shown to impair electrophysiological function in peripheral nerves. Our results suggest that excessive flexion of the hip and extension of the knee should be avoided during THR.
Hyperbaric oxygen therapy as a treatment for stage-I avascular necrosis of the femoral head
Authors: Reis N. D. , Schwartz O. , Militianu D. , Ramon Y. , Levin D. , Norman D. , Melamed Y. , Shupak A. , Goldsher D. , Zinman C.
Published: July 2003

A vascular necrosis (AVN) of the head of the femur is a potentially crippling disease which mainly affects young adults. Although treatment by exposure to hyperbaric oxygen (HBO) is reported as being beneficial, there has been no study of its use in treated compared with untreated patients. We selected 12 patients who suffered from Steinberg stage-I AVN of the head of the femur (four bilateral) whose lesions were 4 mm or more thick and/or 12.5 mm or more long on MRI. Daily HBO therapy was given for 100 days to each patient. All smaller stage-I lesions and more advanced stages of AVN were excluded. These size criteria were chosen in order to compare outcomes with an identical size of lesion in an untreated group described earlier. Overall, 81% of patients who received HBO therapy showed a return to normal on MRI as compared with 17% in the untreated group. We therefore conclude that hyperbaric oxygen is effective in the treatment of stage-I AVN of the head of the femur.
Peripheral bone mineral density in patients with distal radial fractures
Authors: Wigderowitz C. A. , Cunningham T. , Rowley D. I. , Mole P. A. , Paterson C. R.
Published: July 2003

Fractures of the distal forearm are widely regarded as the result of “fragility”. We have examined the extent to which patients with Colles’ fractures have osteopenia. We measured the bone mineral density (BMD) in the contralateral radius of 235 women presenting with Colles’ fractures over a period of two years. While women of all ages had low values for ultra-distal BMD, the values, in age-matched terms, were particularly low among premenopausal women aged less than 45 years. This result was not due to the presence of women with an early menopause. This large survey confirms and extends the findings from earlier small studies. We consider that it is particularly important to investigate young patients with fractures of the distal forearm to identify those with osteoporosis, to seek an underlying cause and to consider treatment.
Vascular malformations of the lower limb with osseous involvement
Authors: Breugem C. C. , Maas M. , Breugem S. J. M. , Schaap G. R. , van der Horst C. M. A. M.
Published: July 2003

Vascular malformations are rare congenital lesions which often have associated skeletal changes. Over a period of ten years, 90 patients at our clinic had a vascular anomaly of the lower limb, examined by either CT or MRI. Of these, 18 (20%) had bony involvement. A questionnaire was sent to these patients (8 men, 10 women) to evaluate their age of presentation, initial symptoms and current complaints. Radiological imaging revealed 15 low- and three high-flow lesions. The mean age at presentation to a physician was six years of age. Pain was the most common complaint. Disparity in leg length of 2 cm or more was observed in ten patients. Of the 16 patients with muscle infiltration, 13 had four or more muscles involved. Treatment by resection alone would require radical surgery.