bluuebunny/crossref_metadata_2025_split huggingface dataset:
Role of the Preparation Procedure in the Formation of Spherical and Monodisperse Surfactant/Polyelectrolyte Complexes
Authors: Luan Yuxia , Ramos Laurence 
Published: April 2007

AbstractComplexes formed by a double‐tail cationic surfactant, didodecyldimethyl ammonium bromide, and an anionic polyelectrolyte, an alternating copolymer of poly(styrene‐alt‐maleic acid) in its sodium salt form, were investigated with respect to variation in the charge ratio (x) between the polyelectrolyte negative charges and the surfactant positive charges. The morphology and microstructure of the complexes were studied by light microscopy and small‐angle X‐ray scattering for different preparation conditions. Independent of the sample preparation procedure and the charge ratio x, the X‐ray results show that the microscopic structure of the complexes is a condensed lamellar phase. By contrast, the morphology of the complexes changes dramatically with the preparation procedure. The complexes formed by mixing a surfactant solution and a polyelectrolyte solution strongly depend on x and are always extremely heterogeneous in size and shape. Surprisingly, we show that, when the two solutions interdiffuse slowly, spherical complexes of micrometric and rather uniform size are systematically obtained, independently on the initial relative amount of surfactant and polyelectrolyte. The mechanism for the formation of these peculiar complexes is discussed.
A Bioorganometallic Approach for the Electrochemical Detection of Proteins: A Study on the Interaction of Ferrocene–Peptide Conjugates with Papain in Solution and on Au Surfaces
Authors: Mahmoud Khaled A. , Kraatz Heinz‐Bernhard 
Published: April 2007

AbstractIn this paper, a new bioorganometallic approach for the detection of proteins using surface‐bound ferrocene–peptide conjugates is presented. Specifically, a series of peptide conjugates of 1′‐aminoferrocene‐1‐carboxylic acid (ferrocene amino acid, Fca) is synthesized: Boc‐Fca‐Gly‐Gly‐Tyr(Bzl)‐Arg(NO2)‐OMe (2), Thc‐Fca‐Gly‐Gly‐Tyr(Bzl)‐Arg(NO2)‐OMe (3), Thc‐Fca‐Gly‐Gly‐Tyr(Bzl)‐Arg(NO2)‐OH (4), Boc‐Fca‐Gly‐Gly‐Arg(Mtr)‐Tyr‐OMe (7), Thc‐Fca‐Gly‐Gly‐Arg(Mtr)‐Tyr‐OMe (8), Thc‐Fca‐Gly‐Gly‐Arg(Mtr)‐Tyr‐OH (9), Thc‐Fca‐Gly‐Gly‐Arg‐Tyr‐OH (10). The peptide is conjugated to the C‐terminal side of Fca and compounds 4, 7–10 possess a thiostic acid linked to the N‐terminal side of Fca in order to facilitate formation of thin films on gold substrates. Competitive inhibition towards papain was determined for Thc‐Fca‐Gly‐Gly‐Tyr(Bzl)‐Arg(NO2)‐OH (4), Thc‐Fca‐Gly‐Gly‐Arg(Mtr)‐Tyr‐OH (9) and Thc‐Fca‐Gly‐Gly‐Arg‐Tyr‐OH (10). The binding interaction between the peptide modified substrates and papain enzyme was studied using real‐time surface plasmon resonance (SPR) imaging. Peptide 10 showed the strongest binding affinity to papain. Adsorption/desorption rate constants were ka=1.75±0.05×105 M−1 s−1 and kd=2.90±0.05×10−2 s−1. Interactions of papain with Fca–peptide 10 were investigated by cyclic voltammetry. The interaction results were also verified by measuring the electrochemical response of the peptide–papain interaction as function of increasing enzyme concentration. A linear relationship was observed for papain concentration of up to 80 nM. Shifting to higher potentials as well as decrease in the overall signal intensity was observed. The detection limit was 4×10−9 M.
Assembly of Infinite Silver(I) Columns, Chains, and Bridged Aggregates with Supramolecular Synthon Bearing Substituted Phenylethynides
Authors: Zhao Liang , Zhao Xiao‐Li , Mak Thomas C. W. 
Published: April 2007

AbstractStructural correlation in a series of eight silver(I) complexes bearing substituted phenylethynide ligands was systematically investigated through variation of the position or steric bulk of substituents on the aromatic ring. All coordination frameworks are constructed with the supramolecular synthon ArCC⊃Agn (Ar=4‐MeC6H4, 3‐MeC6H4, 2‐MeC6H4, 4‐tBuC6H4, 3,5‐(CF3)2C6H3; n=4, 5), and the presence of coexisting ligands was found to influence the supramolecular assembly. The role of π–π stacking, CH⋅⋅⋅π and Ag–C(aromatic) interactions in stabilizing the coordination networks is also discussed.
First Synthesis of 2′‐Deoxyfluoropuromycin Analogues: Experimental Insight into the Mechanism of the Staudinger Reaction
Authors: Charafeddine Adib , Dayoub Wissam , Chapuis Hubert , Strazewski Peter 
Published: April 2007

AbstractThe N6,N6‐dedimethyl‐2′‐deoxyfluoro analogue of puromycin (= 3′‐deoxy‐N6,N6‐dimethyl‐3′‐[O‐methyltyrosylamido]adenosine), its 2′,3′‐regioisomer and a 3′‐cytidyl‐5′‐(2′‐deoxyfluoro)puromycyl dinucleotide analogue were synthesized following an approach involving i) the diastereospecific nitrite‐assisted formation of a lyxo nucleosidic 2′,3′‐epoxide from an adenosine‐2′,3′‐ditriflate derivative in a biphasic solvent mixture; ii) the regio‐ and stereoselective epoxide ring opening with sodium azide under mildly acidic aqueous conditions, iii) the stereospecific introduction of the fluor atom using DAST and iv) the reaction between the nucleosidyl or dinucleotidyl azide and an active ester of the N‐protected amino acid using highly efficient solution conditions for the Staudinger–Vilarrasa coupling, to obtain the corresponding carboxamide directly from the in situ formed iminophosphorane. This coupling reaction furnished sterically quite demanding amides in 94 % isolated yields under very mild conditions and should therefore be of a more general value. Under certain reaction conditions we isolated (amino)acyltriazene derivatives from which dinitrogen was not eliminated. These secondary products are trapped and stabilized witnesses of the first intermediate of the Staudinger reaction, the phosphatriazenes (phosphazides, triazaphosphadienes) which usually eliminate dinitrogen in situ and rapidly rearrange into iminophosphoranes, unless they are derived from conjugated or sterically bulky azides and phosphines. The acyltriazenes could either be thermally decomposed or converted to the corresponding N‐alkyl carboxamides through proton‐assisted elimination of dinitrogen. All compounds were carefully characterized through MS spectrometry, 1H, 19F, 31P and 13C NMR spectroscopy.
Topological Study of Pseudo‐Cubic Hydrogen‐Bond Networks in a Binary System Composed of Primary Ammonium Carboxylates: An Analogue of an Ice Cube
Authors: Yuge Tetsuharu , Tohnai Norimitsu , Fukuda Takeyoshi , Hisaki Ichiro , Miyata Mikiji 
Published: April 2007

AbstractHierarchical classification and single‐crystal X‐ray analysis of unique pseudo‐cubic hydrogen‐bond networks composed of primary ammonium carboxylates were carried out. The networks consist of four carboxylate anions and four primary ammonium cations at the corners of the cube, and twelve charge‐assisted NH⋅⋅⋅O hydrogen bonds on the sides of the cube. The configuration of the carboxylate anions generates topological diversity in the network. The results of this hierarchical classification showed that pseudo‐cubic hydrogen‐bond networks composed of primary ammonium carboxylates can form nine topologically different networks. These pseudo‐cubic networks are a subset of the networks formed by octameric water in the form of an “ice cube”. The classification system can be applied to other pseudo‐cubic networks in a similar way. A survey of crystal structures based on combinations of triphenylacetic acid with various alkylamines (carbon numbers up to eight) and examination of the CSD (Cambridge Structural Database) showed eight salts that form such networks in their crystal structures. These structures are classified into six topologically different networks. Similar networks composed of other salts are also discussed from a topological point of view.
Selective Treatment of Cancer: Synthesis, Biological Evaluation and Structural Elucidation of Novel Analogues of the Antibiotic CC‐1065 and the Duocarmycins
Authors: Tietze Lutz F. , Major Felix , Schuberth Ingrid , Spiegl Dirk A. , Krewer Birgit , Maksimenka Katja , Bringmann Gerhard , Magull Jörg 
Published: April 2007

AbstractNovel diastereomerically pure β‐D‐galactosidic prodrugs (+)‐12 a–e of the cytotoxic antibiotics CC‐1065 and the duocarmycins were prepared for an antibody directed enzyme prodrug therapy (ADEPT) using 4 as a substrate via a radical cyclization to give rac‐5 and rac‐6 followed by a chromatographic resolution of the enantiomers of rac‐5, glycosidation and linkage to the DNA‐binding units 10 a–e. These only slightly toxic compounds can be toxified enzymatically by an antibody–β‐D‐galactosidase conjugate at the surface of malignant cells to give the cytotoxic drugs, which then alkylate DNA. The new prodrugs were tested in in vitro cytotoxicity assays showing excellent QIC50 values of 4800 and 4300 for (+)‐12 a and (+)‐12 b, respectively. The absolute configuration of precursor (+)‐5 was determined by comparison of the experimental CD spectrum with the theoretically predicted CD spectra and by X‐ray structure analysis.
Organometallic Polymers Assembled from Cation–π Interactions: Use of Ferrocene as a Ditopic Linker Within the Homologous Series [{(Me3Si)2NM}2⋅(Cp2Fe)]∞ (M=Na, K, Rb, Cs; Cp=cyclopentadienyl)
Authors: Morris J. Jacob , Noll Bruce C. , Honeyman Gordon W. , O'Hara Charles T. , Kennedy Alan R. , Mulvey Robert E. , Henderson Kenneth W. 
Published: April 2007

AbstractAddition of ferrocene to solutions of alkali metal hexamethyldisilazides M(HMDS) in arenes (in which M=Na, K, Rb, Cs) allows the subsequent crystallization of the homologous series of compounds [{(Me3Si)2NM}2⋅ (Cp2Fe)]∞ (1–4). Similar reactions using LiHMDS led to the recrystallization of the starting materials. The crystal structures of 1–4 reveal the formation of one‐dimensional chains composed of dimeric [{M(HMDS)}2] aggregates, which are bridged through neutral ferrocene molecules by η5‐cation–π interactions. In addition, compounds 3 and 4 also contain interchain agostic MC interactions, producing two‐dimensional 44‐nets. Whereas 1 and 2 were prepared from toluene, the syntheses of 3 and 4 required the use of tert‐butylbenzene as the reaction media. The attempted crystallization of 3 and 4 from toluene resulted in formation of the mixed toluene/ferrocene solvated complexes [{(Me3Si)2NM)2}2⋅ (Cp2Fe)x⋅(Tol)y]∞ (in which M=Rb, x=0.6, y=0.8, 5; M=Cs, x=0.5, y=1, 6). The extended solid‐state structures of 5 and 6 are closely related to the 44‐sheets 3 and 4, but are now assembled from a combination of cation–π, agostic, and π–π interactions. The charge‐separated complex [K{(C6H6)2Cr}1.5(Mes)][Mg(HMDS)3] (15) was also structurally characterized and found to adopt an anionic two‐dimensional 63‐network through doubly η3‐coordinated bis(benzene)chromium molecules. DFT calculations at the B3 LYP/6–31G* level of theory indicate that the binding energies of both ferrocene and toluene to the M(HMDS) dimers increases in the sequence Li<Na<K. This pattern is a consequence of the larger metals allowing more open coordination spheres to support cation–π contacts. By comparison, binding of the isolated metal cations to the aromatic groups follow the reverse order K<Na<Li. A combined analysis of theoretical and experimental data suggest that ferrocene is a stronger cation–π donor than toluene for the lighter metals, but that this difference is eliminated on descending the group.
6‐Substituted Pyrrolo[3,4‐c]pyrazoles: An Improved Class of CDK2 Inhibitors
Authors: Brasca Maria Gabriella , Albanese Clara , Amici Raffaella , Ballinari Dario , Corti Luca , Croci Valter , Fancelli Daniele , Fiorentini Francesco , Nesi Marcella , Orsini Paolo , Orzi Fabrizio , Pastori Wilma , Perrone Ettore , Pesenti Enrico , Pevarello Paolo , Riccardi‐Sirtori Federico , Roletto Fulvia , Roussel Patrick , Varasi Mario , Vulpetti Anna , Mercurio Ciro 
Published: April 2007

AbstractWe have recently reported a new class of CDK2/cyclin A inhibitors based on a bicyclic tetrahydropyrrolo[3,4‐c]pyrazole scaffold. The introduction of small alkyl or cycloalkyl groups in position 6 of this scaffold allowed variation at the other two diversity points. Conventional and polymer‐assisted solution phase chemistry provided a way of generating compounds with improved biochemical and cellular activity. Optimization of the physical properties and pharmacokinetic profile led to a compound which exhibited good efficacy in vivo on A2780 human ovarian carcinoma.
Meta‐analysis of racial disparities in survival in association with socioeconomic status among men and women with colon cancer
Authors: Du Xianglin L. , Meyer Tamra E. , Franzini Luisa 
Published: April 2007

AbstractBACKGROUND.Few studies have addressed racial disparities in survival for colon cancer by adequately incorporating both treatment and socioeconomic factors, and the findings from those studies have been inconsistent. The objectives of the current study were to systematically review the existing literature and provide a more stable estimate of the measures of association between socioeconomic status and racial disparities in survival for colon cancer by undertaking a meta‐analysis.METHODS.For this meta‐analysis, the authors searched the MEDLINE database to identify articles published in English from 1966 to August 2006 that met the following inclusion criteria: original research articles that addressed the association between race/ethnicity and survival in patients with colon or colorectal cancer after adjusting for socioeconomic status. In total, 66 full articles were reviewed, and 56 of those articles were excluded, which left 10 studies for the final analysis.RESULTS.The pooled hazard ratio (HR) for African Americans compared with Caucasians was 1.14 (95% confidence interval [95% CI], 1.00–1.29) for all‐cause mortality and 1.13 (95% CI, 1.01–1.28) for colon cancer‐specific mortality. The test for homogeneity of the HR was statistically significant across the studies for all‐cause mortality (Q = 31.69;P< .001) but was not significant across the studies for colon cancer‐specific mortality (Q = 7.45;P= .114).CONCLUSIONS.Racial disparities in survival for colon cancer between African Americans and Caucasians were only marginally significant after adjusting for socioeconomic factors and treatment. Attempts to modify treatment and socioeconomic factors with the objective of reducing racial disparities in health outcomes may have important clinical and public health implications. Cancer 2007. © 2007 American Cancer Society.
Cost‐effectiveness of colorectal cancer screening with computed tomography colonography
Authors: Pickhardt Perry J. , Hassan Cesare , Laghi Andrea , Zullo Angelo , Kim David H. , Morini Sergio 
Published: April 2007

AbstractBACKGROUNDPrior cost‐effectiveness models analyzing computed tomography colonography (CTC) screening have assumed that patients with diminutive lesions (≤5 mm) will be referred to optical colonoscopy (OC) for polypectomy. However, consensus guidelines for CTC recommend reporting only polyps measuring ≥6 mm. The purpose of the current study was to assess the potential harms, benefits, and cost‐effectiveness of CTC screening without the reporting of diminutive lesions compared with other screening strategies.METHODSThe cost‐effectiveness of screening with CTC (with and without a 6‒mm reporting threshold), OC, and flexible sigmoidoscopy (FS) were evaluated using a Markov model applied to a hypothetical cohort of 100,000 persons age 50 years.RESULTSThe model predicted an overall cost per life‐year gained relative to no screening of $4361, $7138, $7407, and $9180, respectively, for CTC with a 6‒mm reporting threshold, CTC with no threshold, FS, and OC. The incremental costs associated with reporting diminutive lesions at the time of CTC amounted to $118,440 per additional life‐year gained, whereas the incidence of colorectal cancer was reduced by only 1.3% (from 36.5% to 37.8%). Compared with primary OC screening, CTC with a 6‒mm threshold resulted in a 77.6% reduction in invasive endoscopic procedures (39,374 compared with 175,911) and 1112 fewer reported OC‐related complications from perforation or bleeding.CONCLUSIONSCTC with nonreporting of diminutive lesions was found to be the most cost‐effective and safest screening option evaluated, thereby providing further support for this approach. Overall, the removal of diminutive lesions appears to carry an unjustified burden of costs and complications relative to the minimal gain in clinical efficacy. Cancer 2007. © 2007 American Cancer Society.
Quality of life after surgery, external beam irradiation, or brachytherapy for early‐stage prostate cancer
Authors: Litwin Mark S. , Gore John L. , Kwan Lorna , Brandeis Judson M. , Lee Steve P. , Withers H. Rodney , Reiter Robert E. 
Published: April 2007

AbstractBACKGROUND.The primary treatments for clinically localized prostate cancer confer equivalent cancer control for most patients but disparate side effects. In the current study, the authors sought to compare health‐related quality of life (HRQOL) outcomes after the most commonly used treatments.METHODS.A total of 580 men completed the Medical Outcomes Study Short Form‐36, the University of California‐Los Angeles (UCLA) Prostate Cancer Index, and the American Urological Association Symptom Index before and through 24 months after treatment with radical prostatectomy (RP), external beam radiation therapy (EBRT), or brachytherapy (BT).RESULTS.General HRQOL did not appear to be affected by treatment. Obstructive and irritative urinary symptoms were more common after BT (P < .001). Urinary control and sexual function were better after EBRT than BT (P < .001 and P = .02, respectively) and better after BT than RP (P < .001 and P = .01, respectively). Among potent men, recovery of sexual function was best after EBRT and was equivalent after bilateral nerve‐sparing surgery or BT. Sexual bother was more common than urinary or bowel bother after all 3 treatments. Bowel dysfunction was more common after EBRT or BT than RP (P < .001).CONCLUSIONS.In the current study, treatment for localized prostate cancer was found to differentially affect HRQOL outcomes. Urinary control and sexual function were better after EBRT, although bilateral nerve‐sparing surgery diminished these differences among potent men undergoing RP. BT caused more obstructive and irritative symptoms, while both forms of radiation caused more bowel dysfunction. These results may inform medical decision‐making in men with localized prostate cancer. Cancer 2007. © 2007 American Cancer Society.
Impact of Bridging Units on the Dynamics of Photoinduced Charge Generation and Charge Recombination in Donor–Acceptor Dyads
Authors: Van Vooren Antoine , Lemaur Vincent , Ye Aijun , Beljonne David , Cornil Jérôme 
Published: April 2007

AbstractWe estimate, at a full quantum‐chemical level, the various molecular parameters governing the rate of photoinduced charge generation and charge recombination in model organic structures containing a donor and an acceptor unit in view of the possible use of such systems in organic solar cells. The rate of through‐space excitation dissociation, as predicted in the framework of the Marcus–Levich–Jortner theory, is found to be low in comparison to intramolecular decay processes when the donor and acceptor molecules are lying in a head‐to‐tail arrangement and high when the donor and acceptor molecules are superimposed in a cofacial arrangement. The charge separation rates for side‐by‐side donor–acceptor dyads are significantly increased by promoting through‐bond interactions in covalently linked donor and acceptor units. This has motivated a detailed quantitative analysis of the influence of the nature, size, and conformation of the bridging moiety on the calculated transfer rates.
Early weaning decreases play‐fighting behavior during the postweaning developmental period of wistar rats
Authors: Shimozuru Michito , Kodama Yuka , Iwasa Takashi , Kikusui Takefumi , Takeuchi Yukari , Mori Yuji 
Published: April 2007

AbstractWe examined the influence of early weaning on the development of play‐fighting behaviors and anxiety status in Wistar rats. Pups were divided into two groups, those weaned at postnatal day (PD) 16 (early‐weaned group) and those weaned at PD30 (normally weaned group), and were housed in pairs of the same sex. Playful interactions were measured for each pair once a week from 4 to 7 weeks of age. Thereafter, during early adulthood, all the rats were subjected to the elevated plus‐maze test. The frequencies of pinning and playful attack were less in the early‐weaned group than in the normally weaned group. In the elevated plus‐maze test, rat pups in the early‐weaned group had higher anxiety levels. The results showed that deprivation of mother–pup interactions during the preweaning period decreases affiliative interactions between cage mates, including play‐fighting behaviors during the postweaning developmental period, and increases anxiety levels during early adulthood. © 2007 Wiley Periodicals, Inc. Dev Psychobiol 49: 343–350, 2007.
Assessment of motor control using kinematics analysis in preschool children born very preterm
Authors: Sagnol Christophe , Debillon Thierry , Debû Bettina 
Published: April 2007

AbstractThe aim of this study was to better understand the mechanisms underlying the motor difficulties encountered by children born very preterm (VPT) without major sequelae from preterm birth. We compared the organization of visuo‐manual aiming in preterm and full term (FT) preschool aged children based on performance and kinematics data. Twenty preterm (4 females, 16 males) and 20 sex‐ and age‐matched FT children were divided into two age groups (mean age: 3 years‐4 months, and 5 years). Comparison of the performance data showed differences between the older preterm and FT children. Kinematics data revealed differences in movement control between the younger preterm and FT children. The younger FT children did not differ from the older children. In addition, there was an effect of age on both performance and kinematics data for the preterm children only. The pattern of results suggests difficulties in integrating sensory information for movement control in the preterm groups, leading to a delay in the development of visuo‐manual coordination. Kinematics analyses may help identify children at risk for poor school performance. © 2007 Wiley Periodicals, Inc. Dev Psychobiol 49: 421–432, 2007.
Infants' visual‐proprioceptive intermodal perception with imperfect contingency information
Authors: Schmuckler Mark A. , Jewell Derryn T. 
Published: April 2007

AbstractTwo experiments explored 5‐month‐old infants' recognition of self‐movement in the context of imperfect contingencies between felt and seen movement. Previous work has shown that infants can discriminate a display of another child's movements from an on‐line video display of their own movements, even when featural information is removed. These earlier findings were extended by demonstrating self versus other discrimination when the visual information for movement was an unrelated object (a fluorescent mobile) directly attached to the child's leg, thus producing imperfect spatial and temporal contingency information. In contrast, intermodal recognition failed when the mobile was indirectly attached to infants' legs, thus eliminating spatial contingencies altogether and further weakening temporal contingencies. Together, these studies reveal that even imperfect contingency information can drive intermodal perception, given appropriate levels of spatial and temporal contingency information. © 2007 Wiley Periodicals, Inc. Dev Psychobiol 49: 387–398, 2007.