bluuebunny/crossref_metadata_2025 huggingface dataset:
Rhodium(II)‐Catalyzed CH Insertions with {[(4‐Nitrophenyl)sulfonyl]imino}phenyl‐λ3‐iodane
Authors: Nägeli Ivo , Baud Corine , Bernardinelli GéErald , Jacquier Yvan , Moraon Mary , Müllet Paul
Published: December 2004

The [Rh2(OAc)4]‐catalyzed decomposition of {[(4‐nitrophenyl)sulfonyl]imino}phenyl‐λ3‐iodane (NsNIPh) resulted in formal insertions into CH bonds, activated by phenyl or vinyl groups, or by O‐substituents. Scope and limitations of the reaction were investigated. Yields of up to 84% were achieved in the most favorable cases. Yields were enhanced by electron‐releasing substituents and decreased by steric hindrance. Aziridination competed with allylic insertion with olefinic substrates. The insertion reaction proceeded with retention of configuration. With chiral RhII catalysts, a modest asymmetric induction was observed. A mechanism involving direct insertion by a Rh‐complexed nitrene into the CH bond is proposed.
Fluorescence Quenching of 2,2′‐Bithiazole‐Containing Calix[4]arenes by Copper(I). Access to the corresponding [ML2], [ML], and [M2L] copper(I) complexes
Authors: Pellet‐Rostaing Stephane , Regnouf‐de‐Vains Jean‐Bernard , Lamartine Roger , Meallier Pierre , Guittonneau Sylvie , Fenet Bernard
Published: December 2004

The complexing behaviour of 2,2′‐bithiazole‐containing calix[4]arenes towards Cu1 was investigated. The extinction of the intrinsic blue fluorescence of the free ligands upon addition of stoichiometric amounts of the metallic salt was used as complexation probe. This extinction was directly related to the chelation of the metal and allowed the controlled synthesis of new mono‐ and dimetalic complexes which were fully characterized.
Photochemistry of Isothiocoumarin (= 1H‐[2]benzothiopyran‐1‐one)
Authors: Bethke John , Kopf Jürgen , Margaretha Paul , Pignon Bernard , Dupont Léon , Christiaens Léon E.
Published: December 2004

Irradiation (λ = 350 nm) of 1H‐[2]benzothiopyran‐1‐one (2) in the solid state affords selectively and in good yield 6aα, 6bα, 12bα, 12cα ‐tetrahydrocyclobuta[1, 2‐c:4, 3‐c′]bis([2]benzothiopyran)‐5, 8‐dione (3), the head‐to‐head (HH) cis‐cisoid‐cis‐cyclodimer of 2, X‐Ray analysis of 2 confirms that this reaction proceeds according to the well‐established topochemical principles. The same dimer 3 is obtained in low yields on irradiation of 10−1 M solutions of 2 in either MeOH or MeCN, while no conversion at all is observed in benzene. On irradiation of 2 in MeCN in the presence of tetrachloroethene, the [2 + 2] photocycloadduct 4 is formed in good yield, the conversion 2 → 4 being efficiently quenched by naphthalene. In contrast, no reaction is observed ‐on irradiation of 2 in the presence of 2, 3‐dimethylbut‐2‐ene, neither in polar nor in apolar solvents.
Pyranosyl‐RNA: Further Observations on Replication
Authors: Bolli Martin , Micura Ronald , Pitsch Stefan , Eschenmoser Albert
Published: December 2004

Replication (single‐turnover) of pyranosyl‐RNA (= p‐RNA) sequences can be accomplished reliably by template‐directed ligation of 2′, 3′‐cyclophosphates of short oligomers. The ligation process was studied using (mostly) octamers as templates and tetramers as ligands. The transcription of the sequence pr(GGGCGGGC) into the (antiparallel) complementary sequence pr(GCCCGCCC) by ligation of two molecules of pr(GCCC)‐2′, 3′‐cp was investigated in detail; In aqueous 1.5M LiCI solution of pH 8.5 at room temperature (0.45 mM ligand, 0.15 m,M template), the reaction proceeds in up to 60% yield within a week. It is limited by concomitant hydrolysis of cyclophosphate groups of both reactand and ligation product as the only efficient side reaction, the latter occurring ca. three times more slowly than ligation. No ligation at all is observed in the absence of template. The reaction is highly regioselective: the (4′ → 2′) phosphodiester junction is formed exclusively; no isomeric (4′ → 3′) junctions are found. For ligation to occur, template and ligand must be homochiral and must have the same sense of chirality; with chiro‐diastereoisomeric tetramer‐2′, 3′‐cyclophosphates containing a single enantio‐ribopyra‐nosyl unit, no ligation is observed, except to a minor extent in the case of the diastereoisomer that has that unit at the 4′‐end. Observations made in experiments involving six different octamer templates containing isomeric base sequences indicate that the ligation process does not tolerate a mismatch at ligation sites. However, ligation still takes place when a mismatch occurs at either end of the (octamer) template. Ligation efficiencies differ widely, depending on the nature, as well as the sequence, of participating bases. These differences can be understood qualitatively by considering the relative stability of ternary pre‐ligation complexes, together with the differences in interstrand base stacking at ligation sites, Dominance of the latter over intrastrand base stacking is the feature of the p‐RNA structure that appears to determine most of the characteristic properties of p‐RNA.

As regards the etiological context of our work on nucleic‐acid alternatives, it is essential that the chemical properties found for p‐RNA be compared with the corresponding properties of RNA. In the RNA series, the two ligations of the replicative cycle r(GGGCGGGC) ⟺ r(GCCCGCCC) using the corresponding ribofuranosyl‐te‐tramer 2′, 3′‐cyclophosphates as ligands are found to proceed also, though somewhat less efficiently than in the p‐RNA series; however, the ligation step produces exclusively the unnatural (5′ → 2′) phosphodiester junctions instead of the natural (5′→ 3′) junctions. This is in sharp contrast to p‐RNA, where template‐controlled 2′, 3′‐cyclophosphate ligations produce the ‘correct’ phosphodiester junctions.
‘Three‐Component Reaction’ with aromatic thioketones, phenyl azide, and dimethyl fumarate
Authors: Mlostoń Grzegorz , Romański Jaroslaw , Linden Anthony , Heimgartner Heinz
Published: December 2004

The reaction of thiobenzophenone (= diphenylmethanethione; 8a) or 9H‐fluorene‐9‐thione (8b) and methyl fumarate (9) in excess PhN3 at 80° yields a mixture of diastereoisomeric thiiranes 10 and 11 (Scheme 1). A mechanism involving the initial formation of 1‐phenyl‐4, 5‐dihydro‐1H‐1, 2, 3‐triazole‐4, 5‐dicarboxylate 12 by 1, 3‐dipolar cycloaddition of PhN3 and 9 is proposed in Scheme 2. The diazo compound 13, which is in equilibrium with 12, undergoes a further 1, 3‐dipolar cycloaddition with thioketones 8 to give 2, 5‐dihydro‐1, 3, 4‐thiadiazoles 14. Elimination of N2 yields the thiocarbonyl ylide 15 which cyclizes to the corresponding thiirane. Desulfurization of the thiiranes 10 and 11 with hexamethylphosphorous triamide leads to the olefinic compounds 16 (Scheme 3). The crystal structures of 10a, 11a, and 16b were determined.
β‐Loop, γ‐loop, and helical peptide conformations in cyclopeptides containing a steroidal pseudo‐amino acid
Authors: Albert Dieter , Feigel Martin
Published: December 2004

The steroidal pseudo‐amino acids 3ã‐amino‐5β‐cholan‐24‐oic acid (2a), 12ã‐acetoxy‐3ã‐ammonia‐5β‐cholan‐24‐oic acid (2b), and 7ã,12ã‐diacetoxy‐3ã‐amino‐5β‐cholan‐24‐oic acid (2c) are used as rigid spacers in the backbone of the cyclic peptides cyclo(–2a–Phe‐Phe–)2 (1a), cyclo(–2b–Phe‐Phe–)2 (1b), and cyclo(–2c‐Phe‐Phe–)2 (1c). A homogeneous β‐loop conformation is found in the peptide chains of 1a and 1b, while 1c exists as a mixture of ã‐helical and γ‐loop conformations. The structure and homogeneity of the conformations are established by several NMR techniques and are supported by molecular‐dynamics calculations. The peptide conformations depend on the distance and attraction of the two large and lipophilic steroidal parts of the cyclic molecules.
Hybridnaturstoffe: Synthese cyclischer Hydroxamsäuren der Estra‐1,3,5(10)‐trien‐Reihe
Authors: Scherlitz‐Hofmann Ina , Dubs Manuela , Krieg Reimar , Schönecker Bruno , Kluge Michael , Sicker Dieter
Published: December 2004

An approach to a new class of cyclic hydroxamic acids is described leading to a formal combination of a benzoxazine subunit related to some natural aglucones occurring in plants with the steroidal skeleton from two members of the estra‐1,3,5(10)‐triene series. The annelation procedure for a 4‐hydroxy‐1,4‐oxazine moiety to the aromatic A‐ring in estrone (1) and 1‐hydroxy‐4‐methylestra‐1,3,5(10)‐trien‐17‐one (7), used as steroidal precursors, proceeds in four or three steps, respectively (Schemes 1 and 2, resp.). First, a 2‐nitro group is introduced regioselectively by a novel nitrosation‐oxidation procedure or by conventional nitration (→ nitrophenols 2 and 8). Reaction of the phenolic unit of 2 and 8 with methyl bromoacetate or ethyl chlorooxoacetate gives rise to the nitro esters 3, 4, 9, and 10, which are subjected to reductive cyclization either by means of Zn dust in ammonium chloride solution (for the acetates) or of H2/Pt(S)/C (for the sensitive oxalates). Hence, the novel cyclic hydroxamic acids 5, 6, 11, and 12 of the estra‐1,3,5(10)‐triene series are obtained.
Glycosylidene Carbenes. Part 25. Glycosidation of ginkgolides B and A
Authors: Weber Martin , Vasetla Andrea
Published: December 2004

Ginkgolide B (1b) has been glucosylated in THF with the glucosylidene‐derived diazirine 2 under thermal or photochemical conditions. Depending on the amount of 2, we obtained either monoglucosides (5–8), diglucosides (13–17), or triglucosides (21–23). In keeping with earlier results, the use of THF as solvent led mostly to β‐D‐glucosides. The modest regioselectivity in the formation of the monoglucosides, glucosylated either at OC(1) or OC(10), is rationalized on the basis of the relative kinetic acidity of the intra‐ and intermolecularly H‐bonded OH groups of 1b. The tertiary HOC(3) of the monoglucosides was more readily glucosylated than the secondary HOC(1) or HOC(10) (H‐bonded). Glucosidation with 3.5 equiv. of 2 led to triglucosides, with the tri‐β‐D‐glucoside 21 (42%) as the major product. Catalytic hydrogenation afforded the free glucosides 9–12, 18–20, and 24. The di‐ and triglucosides are readily soluble in H2O. Glucosidation with 2 of the ginkgolide‐A‐derived tertiary alcohol 25 yielded 93% of the β‐D‐anomeric glucoside 26. Similarly, glycosidation of 25 with the lactosylidene‐derived diazirine 34 proceeded with a very high stereoselectivity, yielding 92% of the β‐D‐lactoside 35, that was deprotected to the H2O soluble acetate 36.
Methyl and Phenylmethyl 2‐Acetyl‐3‐{[2‐(dimethylamino)‐1‐(methoxycarbonyl)ethenyl]amino}prop‐2‐enoate in the Synthesis of heterocyclic systems: Preparation of 3‐amino‐4H‐pyrido‐[1,2‐a]pyrimidin‐4‐ones
Authors: Selič Lovro , Grdadolnik Simona Golič , Stanovnik Branko
Published: December 2004

Methyl 2‐acetyl‐3‐{[2‐(dimethylamino)‐1‐(methoxycarbonyl)ethenyl]amino}prop‐2‐enoate (4) and phenyl‐methyl 2‐acetyl‐3‐{[2‐(dimethylamino)‐1(methoxycarbonyl)ethenyl]amino}prop‐2‐enoate (5) were prepared in three steps from the corresponding acetoacetic esters, and used as reagents for the preparation of N3‐protected 3‐amino‐4H‐pyrido[1,2‐a]pyrimidin‐4‐ones 10–12, 5H‐thiazolo[3,2‐a]pyrimidin‐5‐one 13, 4H‐pyrido[1,2‐a]‐pyridin‐4‐one 19 and 2H‐1‐benzopyran‐2‐ones 20–23. Free 3‐amino‐4H‐pyrido[1,2‐a]pyrimidin‐4‐ones 24–26 were prepared from 10–12 by removal of the 2‐(methoxycarbonyl)‐3‐oxobut‐1‐enyl or 3‐oxo‐2‐[(phenyl‐methoxy)carbonyl]but‐1‐envl as N‐protecting group by various methods.
Biocatalytic Deracemization of 1,4‐Benzodiazepines in the Synthesis of Enantiomerically Pure Serine
Authors: Avdagić Amir , Šunjić Vitomir
Published: December 2004

An efficient stereocontrolled synthesis of (S)‐N‐Cbz‐serine (Cbz = benzyloxycarbonyl; 12) and of its (R)‐enantiomer is reported. Kinetic resolution of the easily available racemic 3‐(hydroxymethyl)‐1,4‐benzodiazepin‐2‐ones is performed in the key step via acetylation by the immobilized Mucor miehei lipase (Lipozyme IM) at 60°. This method is characterized by high enantiomer purity (ee's ges; 99%) of the intermediary alcohols (+)‐8 and (+)‐9 and acetates (−)‐10 and (−)‐11, as well as of the final products (S)‐ and (R)‐N‐Cbz‐serine, simple recycling of the biocatalyst, complete recovery of 2‐aminobenzophenones (3 and 4) and their recycling into production of 1,4‐benzodiazepines, and possibility to selectively racemize ‘wrong’ enantiomers of the alcohols 8 and 9 in the presence of Amberlite CG 400.
Synthesis of New Nucleosides by coupling of chloropurines with 2‐ and 3‐deoxy derivatives of N‐methyl‐D‐ribofuranuronamide
Authors: Volpini Rosaria , Camaioni Emidio , Vittori Sauro , Barboni Luciano , Lambertucci Catia , Cristalli Gloria
Published: December 2004

The synthesis of new deoxyribose nucleosides by coupling chloropurines with modified D‐ribose derivatives is reported. The methyl 2‐deoxy‐N‐methyl‐3‐O‐(p‐toluoyl)‐α‐D‐ribofuranosiduronamide (α‐D‐8) and the corresponding anomer β‐D‐8 were synthesized starting from the commercially available 2‐deoxy‐D‐ribose (1) (Scheme 1). Reaction of α‐D‐8 with the silylated derivative of 2,6‐dichloro‐9H‐purine (9) afforded regioselectively the N9‐(2′‐deoxyribonucleoside) 10 as anomeric mixture (Scheme 2), whereas β‐D‐8 did not react. Glycosylation of 9 or of 6‐chloro‐9H‐purine (17) with 1,2‐di‐O‐acetyl‐3‐deoxy‐N‐methyl‐β‐D‐ribofuranuronamide (13) yielded only the protected β‐D‐anomers 14 and 18, respectively (Scheme 3). Subsequent deacetylation and dechlorination afforded the desired nucleosides β‐D‐11, β‐D‐12,15, and 16. The 3′‐deoxy‐2‐chloroadenosine derivative 15 showed the highest affinity and selectivity for adenotin binding site vs. A1 and A2A adenosine receptor subtypes.
Synthesis of Chiral C2‐Symmetric Binucleating Ligands
Authors: Fahrni Christoph J. , Pfaltz Andreas
Published: December 2004

The synthesis of a series of chiral enantiomerically pure C2‐symmetric binucleating ligands is reported. Ligands of type 1–4, which consist of a phenolic or heterocyclic unit bridging two chiral dihydrooxazole rings. are readily accessible from chiral amino alcohols. Ligands 5a and 5b are composed of a cyclic urea or thiourea unit, respectively, and two 3,4‐dihydro‐2H‐pyrrole rings containing a stereogenic center next to the N‐atom. Compounds of this type are readily assembled from ethane‐1,2‐diamine and an imidothioic ester derived from pyroglutamic acid. These new ligands, which can coordinate two metals in close proximity to each other, are of interest regarding possible applications in asymmetric catalysis.
First Preparative Enantiomer Resolution of Pirlindole, a Potent Antidepressant Drug
Authors: de Tullio Pascal , Felikidis Apostolos , Pirotte Bernard , Liégeois Jean‐François , Stachow Monique , Delarge Jacques , Ceccato Attilio , Hubert Philippe , Crommen Jacques , Géczy Joseph
Published: December 2004

Pirlindole is an antidepressant drug. It acts principally as reversible inhibitor of monoamine oxidase‐A (RIMA) and appears relatively potent in comparison with reference drugs. Pirlindole possesses stereogenic center but is generally used as racemate. In this work, the first preparative resolution of its enantiomeric couple is described. Whereas selective crystallization of salts of chiral acid failed, two asymmetric synthetic pathways were also examined; however, without success. Finally separation and isolation of enantiomers of pirlindole was completed by using the derivatization method coupled with preparative HPLC. Optical purity of each isomer was determined by chiral HPLC. The specific rotation of each antipode was also determined.
Induction of an Enantiomeric Excess in a Calix[4]arene/Bipyridine‐Based chiral copper(i) complex
Authors: Regnouf‐de‐Vains Jean‐Bernard , Lamartine Roger , Fenet Bernard
Published: December 2004

Introduction of the non‐complexing chiral (S)‐2‐methylbutoxy substituent close to the complexing site of a bis[(bipyridinyl)methoxy]calixarene podand resulted in the induction of an enantiomeric excess of ca. 30 % in the corresponding chiral CuI complex. Structural investigations by high‐resolution NMR studies led us to propose the left‐handed prohelical [CuI(bpy)2] substructure for the major enantiomer.
Enantioselective Dicarbonylation of Styrene to Isotactic Poly[1‐oxo‐2‐phenylpropane‐1,3‐diyl] with phosphinodihydrooxazole‐palladium(ii) complexes: Model studies for enantioface selection preliminary communication
Authors: Aeby Anton , Bangerter Felix , Consiglio Giambattista
Published: December 2004

The first steps, believed to be involved in the highly enantioselective copolymerization of styrene and carbon monoxide to poly[1‐oxo‐2‐phenylpropane‐1,3‐diyl] with phosphinodihydrooxazole‐palladium(II) complexes, were investigated. The insertion of carbon monoxide into [Pd(Me)(PˆN)(solvent)] TfO (PˆN = (S)‐2‐[2‐(5H‐benzo[b]phosphindol‐5‐yl)phenyl]4‐benzyl‐4,5‐dihydrooxazole (1)) and of styrene into [Pd(Me)(PˆN)(solvent)] TfO were highly regioselective (alkyl and acyl substituents trans to N); moreover, the olefin insertion took place with essentially complete enantioface discrimination.
Stereochemistry of the Inhibition of δ‐Chymotrypsin with Optically Active cis‐Decaline‐Type Organophosphates: 31P‐NMR studies
Authors: Furegati Stefan , Ganci Walter , Przibille Georg , Rüedi Peter
Published: December 2004

Investigation of the inhibition of δ‐chymotrypsin with the four novel, optically active, axially and equatorially substituted cis‐3‐(2,4‐dinitrophenoxy)‐2,4‐dioxa‐3λ5‐phosphabicyclo[4.4.0]decan‐3‐ones (= 3‐(2,4‐dinitrophenoxy)hexahydro‐4H‐1,3,2‐benzodioxaphosphorin 2‐oxides) showed only the equatorially substituted enantiomer (−)‐4b to be an irreversible inhibitor of the enzyme, and (−)‐4b at pH 7.8 revealed a quickly rising resonance at −2.49 ppm assigned to the hydrolysis product 8 and later, while inhibition proceeded, a second one at −4.08 ppm. attributed to the δ‐chymotrypsin adduct 7 (Scheme 3). Comparision of the latter signal with the 31P‐NMR chemical shifts of the covalent phosphoserine model compounds (−)‐6a (−5.67 ppm, axial substitution) and (+)‐6b (−4.02 ppm, equatorial substitution) suggests that the inhibition proceeded via neat retention of the configuration at the P‐atom of (−)‐4b yielding the equatorially substituted covalent Ser195 adduct 7.
Monoterpene Dimers from Lisianthius seemannii
Authors: Rodriguez Sylvain , Wolfender Jean‐Luc , Hostettmann Kurt , Stoeckli‐Evans Helen , Gupta Mahabir P.
Published: December 2004

A new acylated dimeric secoiridoid glycoside, seemannoside A (2), has been isolated from the aerial parts of Lisianthius seemannii (GRISEB) O. KUNTZE (Gentianaceae). The structure was established by spectroscopic analysis (UV, MS, 1H‐ and 13C‐NMR, and 2D‐NMR experiments) and chemical reactions as (E‐4′‐O‐p‐coumaroyl)lisianthioside. The structure of the (Z)‐isomer (seemannoside B, 3), also present in the plant, was confirmed by LC/UV/1H‐NMR analysis. The active principle, 6, responsible for the antifungal activity of the apolar extract against Cladosporium cucumerinum, has been isolated. Its structure has been established by NMR spectroscopy and X‐ray crystallographic analysis as a rare type of aglycone monoterpene dimer.
Progress in splat‐cooling of dental alloys
Authors: Johnson L. B. , Carwile A. C.
Published: December 2004

Improved techniques in preparing and sizing dental alloy powders containing Ag, Sn, and Cu have led to amalgams with higher strengths and less spread in dimensional change but very poor shelf life. Since maximum strengths occurred for amalgams containing about 15% more Sn than previously reported, and consequently presumably more of the weak γ2 phase, the higher strengths are difficult to understand.

The poor shelf life may be explained by oxidation of the highly reactive splatcooled alloy or possibly by the existence of highly reactive metastable phases which transform fairly rapidly to the less reactive equilibrium ones.
Crevice corrosion in orthopedic implant metals
Authors: Levine D. L. , Staehle R. W.
Published: December 2004

Studies of orthopedic implant alloys in crevice configuration suggest that cobalt‐chromium alloys such as Haynes‐Stellite 25 are the best choice for multicomponent implants. It is also shown that severe crevice attack may result from use of mixed metals.
Fracture characteristics of acrylic bone cements. II. Fatigue
Authors: Freitag Thomas A. , Cannon Stephen L.
Published: December 2004

The vital first phase of the overall materials study to protract the life of total joint replacements is the identification of the fracture toughness and fatigue properties of bone cements. Information gained from fatigue testing, performed in a manner which simulates in vivo conditions, and fracture toughness, which is a measure of the propensity of a crack to propagate, is the first step towards the prediction of the life of the total joint replacement. Part I of this study identified the fracture toughness characteristics of two acrylic bone cements, while the present work has been concerned with determining the fatigue behavior by means of tests conducted in a rotating bending fatigue apparatus. Fatigue specimens were fabricated under conditions which approximated clinical procedures and then tested while immersed in bovine serum at 37°C in order to simulate in vivo conditions. In addition, a similar study was completed on specimens tested in air at ambient temperature for purposes of comparison. Testing was conducted in both of these environments on specimens containing zero and 10.0 wt % BaSO4. Cyclic loading frequency was maintained between 1200 and 1400 cycles/min in order to insure that crack propagation was the sole mechanism of failure, i.e., failure via cyclic thermal softening was obviated.

Results of this phase of the study, when analyzed by a Student t‐test at the 90% confidence level with four degrees of freedom, indicate that the fatigue life of specimens tested in bovine serum at 37°C is superior to that of specimens tested in air at ambient temperature. The addition of BaSO4 to Simplex‐P cement, while not significant at the 90% confidence level, was significant in increasing the fatigue life in air at the 80% confidence level; however, this effect was not noticeable when testing in bovine serum at 37°C. Examination of the fracture surfaces enabled calculation of the critical stress intensity factor which when compared with values from an earlier work showed good agreement.
Collagen sponge: Theory and practice of medical applications
Authors: Chvapil Milos
Published: December 2004

Theoretical as well as practical–clinical applications of one form of collagen (collagen sponge) as a biodegradable material is reviewed. The role of porosity of the sponge and surface characteristics of the meshwork in relation to cell ingrowth are considered essential features of collagen sponge. Rate of resorption and antigenicity could be controlled by graded crosslinking of collagenous framework. Four basic examples of clinical use of collagen sponge are presented: as wound (burn) dressing material, as a matrix for bone and cartilage repair, as an intravaginal contraceptive diaphragm, and as surgical tampons.
Blood‐compatible materials by fluid perfusion
Authors: Predecki Paul , Russell P. A. , Newman M. M.
Published: December 2004

The feasibility of preventing platelet adhesion to porous foreign surfaces in contact with blood by passing (perfusing) a physiologic fluid through the pores into the blood was tested. Porous‐walled tubes of Teflon (Gore‐tex) and aluminosilicate ceramic were perfused with lactated Ringer's solution at rates between 3.13 and 0.3 cc/min per cm2 of perfused surface and exposed to heparinized and unheparinized flowing human whole blood for periods of 3–6 min. Under these conditions, with 0.159 cm I.D. tubes and a mean blood flow rate of 8.3 cm/sec, the adhesion of all blood cells was prevented, compared with the adhesion of 1 to 8 × 106 platelets/cm2 on the nonperfused controls. The adhesion of plasma proteins was also markedly reduced as determined by bromophenol blue staining.

The critical perfusion rate to prevent platelet adhesion to Gore‐tex (0.5 μ pore size, 60% pore volume) was found to be between 0.04 and 0.3 cc/ (min · cm2). The boundary layer produced by a perfused segment of porous tubing prevented platelet adhesion for several centimeters downstream from the perfusing segment under experimental conditions used.
Thromboresistance of graft‐type copolymers with hydrophilic–hydrophobic microphase‐separated structure
Authors: Nakashima Toshihide , Takakura Koichi , Komoto Yoshiaki
Published: December 2004

Graft‐type copolymers composed of hydrophilic poly (hydroxyethyl methacrylate) (PHEMA) as a backbone and a small amount of hydrophobic poly (methylmethacrylate) (PMMA) as a long branch exhibit excellent thromboresistance.

The interrelationship between the thromboresistance and microstructure of the graft‐type copolymers as well as the water structure in the hydrated polymers has been investigated. It was concluded that both the structure of hydrophobic domain dispersed in the hydrophilic matrix and the water bound to the polymer may be responsible for the excellent thromboresistance of the graft‐type copolymers.
Compliance as a factor effecting the patency of a copolyurethane vascular graft
Authors: Lyman D. J. , Fazzio F. J. , Voorhees H. , Robinson G. , Albo D.
Published: December 2004

A new solid‐wall vascular graft which has a compliance approximating that of the natural artery has been prepared from a copolyether–urethane material. Six of nine of these compliant grafts implanted in dogs were patent on removal, the longest implant time being 77 days for a 4‐mm I.D. femoral artery graft. This is in contrast to noncompliant grafts of the same copolyurethane in which failure usually occurred within 48 hr.
Microporous glassy fillers for dental composites
Authors: Mabie C. P. , Menis D. L.
Published: December 2004

A microporous filler giving greatly improved finishability, systemic nontoxic X‐ray opacification, low thermal expansion (27.2 × 10−6/°C), and satisfactory translucencies has been developed for dental composite resin restorations. These fillers are prepared from frits obtained by the low‐temperature calcination of gelled inorganic sols followed by a pulsed high‐temperature treatment. Composites prepared from these fillers are within the range of commercial products with regard to strength and setting contraction.
Transport properties of hydrolyzed polyacrylonitrile
Authors: Dabrovská L. , Praus R. , Stoy V. , Vacik J.
Published: December 2004

Measurements of the permeability coefficients of various compounds up to a molecular weight of about 70,000 have shown clearly that membranes prepared from hydrolyzed polyacrylonitrile are about 10 times more permeable than those made of poly(2‐hydroxyethyl) methacrylate. The higher permeability is probably due more to the higher water content (about 75%) than to the type of network. The high mechanical strength of the membranes and their good permeability to compounds possessing a comparatively high molecular weight seem to designate the material for some new applications in medicine.
A novel technique for studying the adsorption of plasma proteins on hydrophobic surfaces
Authors: Bagnall R. D. , Annis J. A. D. , Arundel P. A.
Published: December 2004

A method is shown for deducing the surface area of a pendant drop from the same profile photograph as is normally used to determine interfacial tension. Manipulation of such drops by a micrometer syringe then enables the pendant drop to be used as a surface balance for studying adsorption from bulk solutions. Results are given for the compression of films from solutions of albumin, γ‐globulin, fibrinogen, albumin–γ‐globulin mixture and albumin–γ‐globulin–fibrinogen mixture, and from serum, plasma, and blood at the isooctane–buffer interface. It is suggested that γ‐globulin and fibrinogen films are unfolded at the interface but that albumin films are different in that they consist of an inner, unfolded layer and an outer, globular layer. A film from serum resembles that from γ‐globulin alone, and not that from albumin–γ‐globulin mixture, whereas a film from plasma resembles that of fibrinogen at low compression and that of albumin–γ‐globulin–fibrinogen mixture at high compression. A film from blood is shown to resemble that from plasma.
Tissue response to allergenic leachables from dental materials
Authors: Kallus T. , Hensten‐Pettersen A. , Mjör I. A.
Published: December 2004

In addition to toxic reactions to dental materials, some individuals may develop or exhibit hypersensitivity reactions to leachable components. An experimental model combining the guinea pig maximization test for induction of hypersensitivity and the subcutaneous implantation of dental cements is described. Guinea pigs immunized with AH 26, an epoxy‐bisphenol resin, showed an increased tissue response to AH26 implants. Guinea pigs immunized with zinc oxide–eugenol did not show a similarly increased response, possibly because of an anti‐inflammatory effect of eugenol. The experimental model may prove useful in predicting the effect of leachable allergens from dental materials in sensitized individuals.
The glutaraldehyde‐stabilized porcine aortic valve xenograft. II. Effect of fixation with or without pressure on the tensile viscoelastic properties of the leaflet material
Authors: Lee J. Michael , Boughner Derek R. , Courtman David W.
Published: December 2004

We have examined the tensile viscoelastic properties of circumferential and radial strips of porcine aortic valve leaflets following fixation in glutaraldehyde and formaldehyde, with or without pressure. After aldehyde treatment, the radial strips remained weaker and less stiff than circumferential strips and responded slightly differently to the treatment. After fixation, with or without pressure, the radial strips showed large changes in stress‐strain and hysteresis responses due to initial loading, and there was a twofold reduction in tensile strength and final stiffness. For strips in both directions, fixation without pressure produced doubled extensibility and a ramping stress‐strain curve. Permanent (plastic) deformation of 5–20% occurred as a result of cyclic loading, stress relaxation, and creep experiments. Pressure fixation, however, produced little change in stress‐strain results other than a simple shift to lower strain and produced no plasticity. Both methods of fixation reduced stress relaxation and creep. Mechanical test results are consistent with a loss of ground substance matrix during fixation. Reductions in tensile strength after fixation may be due to “riveting” of collagen geometry, producing local stress concentrations.
Isolation of serum protein organometallic corrosion products from 316LSS and HS‐21 in vitro and in vivo
Authors: Woodman J. L. , Black J. , Jiminez S. A.
Published: December 2004

An investigation into blood‐borne organometallic compounds that arise from the corrosion of metals used in orthopedic prosthetic devices was conducted using an in vivo rat model with an implantation time of 10 days and an in vitro human serum model with an incubation time of 5 days. Both models involved 316LSS and HS‐21

Haynes Stellite 21: Stellite Division of Cobalt Corporation, Kokomo, Indiana (An alloy of very similar composition to ASTM F‐75)

in the spherical powder form of 55 ± 5 μm microns in diameter at three different surface areas to body weight ratios. Gel chromatography on cross‐linked dextran (G‐200) was used to fractionate the serum proteins which bound the metal ions (chromium, cobalt, and nickel) released and identify them. Atomic‐absorption‐spectrophotometry analysis measured the concentration of the metal ions in each serum protein peak as well as whole serum from both models, and red cell and tissue from the in vivo model. Within the serum proteins, the metal ions were bound to two of the principal serum protein peaks. Similar distributions of the metals among the serum protein peaks were not noted.
Component wear of total knee prostheses using Ti‐6Al‐4V, titanium nitride coated Ti‐6Al‐4V, and cobalt‐chromium‐molybdenum femoral components
Authors: Peterson C. D. , Hillberry B. M. , Heck D. A.
Published: December 2004

A knee simulator was used to study the wear of carbon fiber reinforced UHMWPE(Poly Two) (Poly Two is a registered trademark of Zimmer, USA) tibial and patellar components against Ti‐6Al‐4V, titanium nitride (TiN)‐coated Ti‐6Al‐4V, and cobaltchromium‐molybdenum femoral components. The prostheses tested were regular sized Miller‐Galante total knees mounted on 316L stainless steel fixtures using bone cement. An environmental chamber surrounded the knee and maintained bovine serum lubricant at 37°C. The specimens were tested using consecutive blocks of 464 level walking steps, 8 ascending stairs and 8 descending stairs for a total of 100,000 steps. The wear mechanisms found on the tibial components were scratching, carbon fiber associated damage, surface deformation, pitting, minor abrasion, and delamination. Three forms of carbon fiber associated damage were identified; fibers pulled from the surface, broken fibers, and UHMWPE removed from the surface fibers. The SEM evaluation revealed a pit forming mechanism. No correlation was found between femoral component material and tibial surface damage. Visual examination of the femoral components revealed no signs of wear or scratching on the cobalt‐chromium‐molybdenum or TiN‐coated Ti‐6Al‐4V components. There were, however, many light surface scratches on the uncoated Ti‐6Al‐4V components, which were also observed in a supplementary test of an uncoated Ti‐6Al‐4V component tested with a conventional polyethylene tibial component.
Hydrogels for buccal drug delivery: Properties relevant for muco‐adhesion
Authors: de Vries M. E. , Boddé H. E. , Busscher H. J. , Junginger H. E.
Published: December 2004

In order to develop a muco‐adhesive hydrogel for buccal drug delivery it is necessary to understand fully the properties determining adhesiveness as well as mechanisms involved. In this study we measured glass transition temperatures, water contact angles and the peel‐ and shear detachment forces from porcine oral mucosa, of acrylic acid and butyl acrylate copolymers. The contact angle maximizes at 50% butyl acrylate content. The glass transition temperature decreases from 0% to 100% butyl acrylate. There seems to exist a certain combination of contact angle and glass transition temperature which is related to adhesiveness. This strongly suggests that, in order to obtain a muco‐adhesive hydrogel, at least two properties have to be optimized: (1) the polarity of the polymer surface and (2) the molecular mobility of the polymer groups.
Organoapatites: Materials for artificial bone. I. Synthesis and microstructure
Authors: Stupp Samuel I. , Ciegler Glenn W.
Published: December 2004

We have synthesized a new family of materials we termed organoapatites which may be useful in the formulation of artificial bone. These materials are synthesized by nucleation and growth of apatite crystals in media containing poly(amino acids) or synthetic organic polyelectrolytes using strict atmospheric, temperature, and pH control. The macromolecules used to synthesize the organoapatites include poly(L‐lysine), poly(L‐glutamic acid), and poly(sodium acrylate). The products were characterized by x‐ray diffraction, scanning electron microscopy, surface area measurements, elemental analysis, and spectroscopic techniques. Organoapatites were found to contain large surface area morphologies with small crystallites which mature slowly based on analysis of Ca/P ratios. The organic macromolecules are thought to induce nucleation of crystals but also to quench their growth, thus becoming intimately dispersed in a mineral network. The organomineral particles harvested from the reaction medium contain polymernetted microcrystals, and for this reason the synthetic approach can be used to modulate crystal maturation and biological response. It is likely that the preparative approach mimics some aspects of natural bone matrix synthesis and could be specially useful in the preparation of mineral implants containing intimate dispersions of small amounts of biomolecules such as growth factors, special drugs, or bioadhesives.
Microbial adherence on poly(methyl methacrylate) (PMMA) surfaces
Authors: Chang Chung‐Che , Merritt Katharine
Published: December 2004

Infection remains a major complication following the use of implanted biomaterials. Often these infections are caused by low‐virulence organisms or by a mixture of organisms (polymicrobial). In this study two methods were used to quantitate the bacteria which had adhered to poly(methyl methacrylate) (PMMA) samples. The bacteria were eluted from the sample using an ultrasonic cleaner. The number eluted was then counted by colony counts, which determines viable organisms and by particle counting which counts both viable and nonviable organisms. A known adherent strain of Staphylococcus epidermidis and a strain of Proteus mirabilis were used. In general the adherence of S. epidermidis was greater than that of Proteus. When the two organisms were used together, there was an alteration in the adherence pattern which generally increased the adherence of Proteus and had no effect or decreased the adherence of S. epidermidis. The use of both quantitation techniques provided important information on the adherence of organisms to PMMA to which gentamicin had been added. It was evident that organisms did adhere to the PMMA plus gentamicin samples but were not viable when eluted. The amount of adherence to PMMA plus gentamicin was similar to that of PMMA alone at 30 min but was markedly decreased at 24 h. There was a considerable dead biofilm mass on the PMMA plus gentamicin samples which might be a significant promoter of late infections by providing a surface attractive to other strains of bacteria.
Leucite content of selected dental porcelains
Authors: Piché Peter W. , O'Brien William J. , Groh Carole L. , Boenke Kenneth M.
Published: December 2004

Leucite is a major crystalline component of dental porcelains. The presence of tetragonal leucite in dental porcelains increases their coefficients of thermal expansion due to its high coefficient of thermal expansion (20–25 × 10−6/°C). This is particularly useful for those porcelains designed for bonding to precious metals and nickel alloys. The purpose of this study was to determine the leucite content of selected commercial dental porcelains in relation to their coefficient of thermal expansion values. The weight fraction of leucite was determined with quantitative x‐ray diffraction using copper as an internal standard. Coefficient of thermal expansion values were determined using a thermal dilatometric analyzer. Five commercial body porcelains were studied. Leucite was not detected in samples of Vitadur N and Duceram LFC. An ANOVA showed that there was a significant difference in the weight fraction of leucite for Silhouette, Ceramco II, and Optec HSP porcelains. Linear regression revealed a correlation (R = 0.91) between weight fraction of leucite and the coefficient of thermal expansion for those samples containing leucite. Ducram LFC, which is recommended by the manufacturer for use with metals and leucite‐containing porcelains, had no detectable leucite although the coefficient of thermal expansion was found to be 13.2 ± 0.4 × 10−6/°C at 25–472°C. A low glass transition temperature contributed to the high average coefficient of thermal expansion value. © 1994 John Wiley & Sons, Inc.
In vivo induction of macrophage Ia antigen (MHC class II) expression by biomedical polymers in the cage implant system
Authors: Petillo O. , Peluso G. , Ambrosio L. , Nicolais L. , Kao W. J. , Anderson J. M.
Published: December 2004

Examination of the cellular components in the inflammatory exudate, which infiltrates subcutaneous cages, can be used to monitor the progress of an inflammatory response to an implanted material. Of particular interest is the study of monocyte/ macrophage infiltration into the implanted cages containing biomaterials, as macrophages may initiate a wide spectrum of responses upon interaction with a foreign material. In this study, the authors propose a technique using subcutaneous tissue cages in conjunction with cytofluorimetric analysis of exudate leukocytes to evaluate the monocyte/macrophage cell activation in response to different materials. The studies reported here used several materials. The studies reported here used several materials (thermoplastic and elastomeric polymers) as the challenging agent, to demonstrate whether polymers, chemically different from each other, could differentially activate macrophages to carry out their proinflammatory role more effectively. The materials tested included: poly(etherurethane ureas) (PEUU A'), poly(etherurethane ureas) with a surface active additive, Methacrol®, (PEUUC'), polymethylsiloxane (PDMS), polyetherimide, (PEI), and polyetheretherketone, (PEEK). For all the tested materials, the maximum numbers of exudate cells and of Ia‐positive macrophages were found on day 7, although the entity of the cell increase was associated with the material used for the implant. Similarly, the percentage of Ia‐positive macrophages varied according to the specific polymer present in the cages after 7 days. By day 14, the percentage of Ia‐positive macrophages decreased with individual exudates showing 19–32% Ia‐positive cells depending on the different type of material. Only in the case of PDMS did the percentage of Ia‐positive macrophages remain the same as compared with control empty cage macrophages. © 1994 John Wiley & Sons, Inc.
A systematic preparation of new contracted Gaussian‐type orbital sets. IV. The effect of additional 3s functions introduced by the use of the six‐membered 3dGTOs
Authors: Tatewaki Hiroshi , Sakai Yoshiko , Huzinaga Sigeru
Published: December 2004

The Gaussian‐type basis sets for molecular calculations are usually prepared by an atomic SCF program in which spherical coordinates are used. On the other hand, many molecular SCF and CI programs are written by using the Cartesian coordinates and as a result six‐membered d‐type functions (x2, y2, z2, xy, yz, zx)e−γr2 are often used. They contain one additional 3s function which does not exist in the atomic calculation. Therefore, we shall have an incorrect, deeper molecular binding energy, unless we readjust the atomic total energy by adding the 3s orbital to the original basis set. Some examples are shown in the case of Cu2 molecule, where we have found that the correction is quite appreciable, which was overlooked in previous work.
Isomer discrimination by topological information approach
Authors: Bonchev D. , Mekenyan O. V. , Trinajstić N.
Published: December 2004

A comparative analysis of ten topological indices is made. No index is found to discriminate isomers uniquely. A combined topological index, named the superindex, consisting of a number of topological indices is proposed. Information theory is applied to express all components of the superindex on a common quantitative scale. The superindex is tested on the sample of 427 graphs consisting of all acyclic, monocyclic, and bicyclic graphs with 4–8 vertices.
The conformation of alkyl sulfoxides
Authors: Tai Julia C.
Published: December 2004

Parameters for sulfoxides used in force field MM1 were modified to be incorporated into force field MM2. The conformations of ten alkyl sulfoxides were then calculated using MM2 with these new parameters. The alkyl groups used were methyl, ethyl, isopropyl, and t‐butyl. It was found that of the many possible conformations for these compounds, only one or two stable conformers exist, and that the number of these conformers agrees with the number of reported SO stretching frequencies in almost every case. No apparent correlation between the vibration frequency and the molecular structure was found.
Molecular orbital theory of the hydrogen bond. 24. Ground‐state water–uracil complexes
Authors: Del Bene Janet E.
Published: December 2004

Ab initio SCF calculations with the STO‐3G basis set have been performed to investigate the structural, energetic, and electronic properties of mixed water–uracil dimers formed at the six hydrogen‐bonding sites in the uracil molecular plane. Hydrogen‐bond formation at three of the carbonyl oxygen sites leads to cyclic structures in which a water molecule bridges N1H and O2, N3H and O2, and N3H and O4. Open structures form at O4, N1H, and N3H. The two most stable structures, with energies of 9.9 and 9.7 kcal/mole, respectively, are the open structure at N1H and the cyclic one at N1H and O2. These two are easily interconverted, and may be regarded as corresponding to just one “wobble” dimer. At 1 kcal/mole higher in energy is another “wobble” dimer consisting of an open structure at N3H and a cyclic structure at N3H and O4. The third cyclic structure at N3H and O2 collapses to the “wobble” dimer at N3H and O4. The two “wobble” dimers are significantly more stable than the open dimer formed at O4, which has a stabilization energy of 5.4 kcal/mole. Uracil is a stronger proton donor to water through N1H than N3H, owing to a more favorable molecular dipole moment alignment when association occurs through H1. Hydration of uracil by additional water molecules has also been investigated. Dimer stabilization energies and hydrogen‐bond energies are nearly additive in most 2:1 water:uracil structures. There are three stable “wobble” trimers, which have stabilization energies that vary from 7 to 9 kcal/mole per water molecule. Hydrogen‐bond strengths are slightly enhanced in 3:1 water:uracil structures, but the cooperative effect in hydrogen bonding is still relatively small. The single stable water–uracil tetramer is a “wobble” tetramer, with two water molecules which are relatively free to move between adjacent hydrogen‐bonding sites, and a stabilization energy of approximately 8 kcal/mole per water molecule. Within the rigid dimer approximation, successive hydration of uracil is limited to the addition of one, two, or three water molecules.
Molecular orbital theory of the hydrogen bond. 25. Water–uracil complexes in excited n → π states
Authors: Del Bene Janet E.
Published: December 2004

Hydrogen bonding of uracil with water in excited n → π* states has been investigated by means of ab initio SCF‐CI calculations on uracil and water–uracil complexes. Two low‐energy excited states arise from n → π* transitions in uracil. The first is due to excitation of the C4O group, while the second is associated with excitation of the C2O group. In the first n → π* state, hydrogen bonds at O4 are broken, so that the open water–uracil dimer at O4 dissociates. The “wobble” dimer, in which a water molecule is essentially free to move between its position in an open structure at N3H and a cyclic structure at N3H and O4 in the ground state, collapses to a different “wobble” dimer at N3H and O2 in the excited state. The third dimer, a “wobble” dimer at N1H and O2, remains intact, but is destabilized relative to the ground state. Although hydrogen bonds at O2 are broken in the second n → π* state, the three water–uracil dimers remain bound. The “wobble” dimer at N1H and O2 changes to an excited open dimer at N1H. The “wobble” dimer at N3H and O4 remains intact, and the open dimer at O4 is further stabilized upon excitation. Dimer blue shifts of n → π* bands are nearly additive in 2:1 and 3:1 water:uracil structures. The fates of the three 2:1 water:uracil trimers and the 3:1 water:uracil tetramer in the first and second n → π* states are determined by the fates of the corresponding excited dimers in these states.
Model for diffusion‐limited electrochemiluminescence
Authors: Akins Daniel L. , Snider Arthur David
Published: December 2004

An approximate analytic expression is derived, based on a novel model for the reactive–diffusive processes in a electrochemiluminescence (ecl) experiment. The physical system treated is one in which ecl is produced by stepping the voltage of a planar electrode to the diffusion‐limited reduction value for an emitter species in the presence of a bulk oxidant precursor (9,10‐DPA with benzoyl peroxide). The unknown rate constants are determined by a least‐squares curve‐fitting computer code. The model, though crude, provides an excellent fit to the ecl intensity versus time data, including the rise portion of the curve.