bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamic Chemical Devices: Photoinduced Electron Transfer and Its Ion‐Triggered Switching in Nanomechanical Butterfly‐Type Bis(porphyrin)terpyridines
Authors: Linke‐Schaetzel Myriam , Anson Christopher E. , Powell Annie K. , Buth Gernot , Palomares Emilio , Durrant James D. , Balaban Teodor Silviu , Lehn Jean‐Marie
Published: November 2005

A series of butterfly‐type molecular constructs has been prepared in good yield by using a double Stille coupling synthetic protocol. They are composed of a terpyridine (terpy) scaffold and two wings composed of appended porphyrins that are capable of switching from an extended W geometry to a compact U geometry upon cation coordination of the terpy unit. The porphyrin moieties exist in the constructs either as free bases or they can be sequentially metallated, thus giving rise to wings of different “colours”. Stationary and time‐resolved emission studies of the HZn, ZnAu and Zn2Au constructs show that the electronic properties are strongly dependent on the geometry. In the extended W conformation an energy‐transfer process is seen from the free base to the Zn‐metallated porphyrin. In the U conformation in Zn2Au the donor luminescence resulting from the singlet excited state of the Zn wing is strongly, quenched not only due to the heavy atom effect but also due to a fast electron‐transfer process to the ground state of the Au wing. Furthermore, the binding of (α,ω)‐diamine substrates to the ZnII–porphyrin sites can also influence the conformation of the system. For the Zn2Zn construct, single‐crystal diffraction experiments with synchrotron radiation allowed the structure to be solved by direct methods and fully refined; it shows the expected U conformation. The central Zn atom is six‐coordinate, whereby the zinc atom is coordinated by the η3‐terpy ligand as well by monodentate and semi‐chelating acetate anions. The structure is made rigid by hydrogen bonds involving the aqua ligands on the outer Zn centres and acetate oxygen atoms. The present system thus represents a double‐trigger‐modulated optomechanical switching device with selective substrate binding for either metal atoms or tailored ligands. Both energy‐ and electron‐transfer processes can be controlled opening a means of improving the on/off ratio in future constructs.
Origin of Stereoinduction by Chiral Aminophosphane Phosphinite Ligands in Enantioselective Catalysis: Asymmetric Hydroformylation
Authors: Carbó Jorge J. , Lledós Agustí , Vogt Dieter , Bo Carles
Published: November 2005

The origin of stereoinduction by chiral aminophosphane phosphinite (AMPP) ligands in asymmetric hydroformylation was investigated with a theoretical approach. The roles of the stereogenic center at the aminophosphane phosphorus atom (NP*) and of the chirality of the backbone were analyzed by considering three experimentally tested cases: 1) P‐stereogenic yielding highee, 2) P‐nonstereogenic yielding lowee, and 3) P‐stereogenic yielding lowee. We succeeded in reproducing the experimentally observed trends for the three studied AMPP ligands. Our results indicated that alkene insertion into the rhodium–hydride bond is the selectivity‐determining step, and not alkene coordination. Additional calculations on model systems revealed that the different nonbonding weak‐type interactions of styrene with the substituents of the NP* stereogenic center in an axial position is responsible for stereodifferentiation. The chirality of the AMPP backbone plays a secondary role. The rationalization of the stereochemical outcome is not straightforward, because two competitive equatorial/axial reaction paths, showing opposite asymmetric induction, must be considered. Construction of stereochemical models and evaluation of stereoinduction for novel ligand systems suggested that two prerequisites are required to improve the performance of AMPP‐type ligands in asymmetric hydroformylation: 1) combination of stereorecognition and stereohindrance by substituents at the NP* atom, and 2) more rigid backbones.
Silica Self‐Assembly and Synthesis of Microporous and Mesoporous Silicates
Authors: Rimer Jeffrey D. , Fedeyko Joseph M. , Vlachos Dionisios G. , Lobo Raul F.
Published: November 2005

The microstructure of silica in basic aqueous solutions containing organic cations and prepared from monomeric precursors is reviewed and interpreted within the context of classical ideas of self‐assembly of molecular aggregates. The solution properties can be understood by using the pseudo‐phase separation approach coupled to the acid–base chemistry of silanol groups and the Poisson–Boltzmann equation. The silica nanoparticles frequently observed in these systems have a core–shell structure with silica in the core and the organic cations at the shell. Individual particles are observed when the forces between particles are repulsive—as is the case for small cations such as tetramethylammonium or tetrapropylammonium—and extended structures such as M41S materials are formed when the forces are attractive—‐as is the case for surfactants such as cetyltrimethylammonium. These ideas are useful to understand the evolution of zeolite synthesis gels from nucleation to crystal growth. Although at room temperature the silica and the organic cations are segregated, upon heating the organic cations are embedded within the particles. This transformation signals the onset of structure direction whereby the size and geometry of the organic cation induce changes in the structure of silica that may lead to zeolite nuclei.
Controlling the Nature of Mixed (Phthalocyaninato)(porphyrinato) Rare‐Earth(III) Double‐Decker Complexes: The Effects of Nonperipheral Alkoxy Substitution of the Phthalocyanine Ligand
Authors: Wang Rongming , Li Renjie , Li Yong , Zhang Xianxi , Zhu Peihua , Lo Pui‐Chi , Ng Dennis K. P. , Pan Na , Ma Changqin , Kobayashi Nagao , Jiang Jianzhuang
Published: November 2005

The half‐sandwich rare‐earth complexes [MIII(acac)(TClPP)] (M=Sm, Eu, Y; TClPP=meso‐tetrakis(4‐chlorophenyl)porphyrinate; acac=acetylacetonate), generated in situ from [M(acac)3]⋅n H2O and H2(TClPP), were treated with 1,8,15,22‐tetrakis(3‐pentyloxy)phthalocyanine [H2{Pc(α‐OC5H11)4}] (Pc=phthalocyaninate) under reflux in n‐octanol to yield both the neutral nonprotonated and protonated (phthalocyaninato)(porphyrinato) rare‐earth double‐decker complexes, [MIII{Pc(α‐OC5H11)4}(TClPP)] (1–3) and [MIIIH{Pc(α‐OC5H11)4}(TClPP)] (4–6), respectively. In contrast, reaction of [YIII(acac)(TClPP)] with 1,4,8,11,15,18,22,25‐octakis(1‐butyloxy)phthalocyanine [H2Pc(α‐OC4H9)8] gave only the protonated double‐decker complex [YIIIH{Pc(α‐OC4H9)8}(TClPP)] (7). These observations clearly show the importance of the number and positions of substituents on the phthalocyanine ligand in controlling the nature of the (phthalocyaninato)(porphyrinato) rare‐earth double‐deckers obtained. In particular, α‐alkoxylation of the phthalocyanine ligand is found to stabilize the protonated form, a fact supported by molecular‐orbital calculations. A combination of mass spectrometry, NMR, UV‐visible, near‐IR, MCD, and IR spectroscopy, and X‐ray diffraction analyses, facilitated the differentiation of the newly prepared neutral nonprotonated and protonated double‐decker complexes. The crystal structure of the protonated form has been determined for the first time.
Unusual High‐Temperature Structural Behaviour in Ferroelectric Bi2WO6
Authors: McDowell Neil A. , Knight Kevin S. , Lightfoot Philip
Published: November 2005

The crystal structure of Aurivillius phase ferroelectric Bi2WO6 has been studied in detail as a function of temperature by using high‐resolution powder neutron diffraction. In agreement with an earlier study, a transition from space group P21ab to B2cb occurs at about 660 °C. This transition corresponds to the loss of one octahedral tilt mode within the perovskite‐like WO4 layer of the structure. A second, reconstructive, phase transition occurs around 960 °C, corresponding to the ferroelectric Curie point; in contrast to previous suggestions, the structure of this high‐temperature phase contains layers of stoichiometry WO4, with WO6 octahedra sharing edges and corners, and with the fluorite‐like Bi2O2 layers remaining essentially unchanged. This structure is closely related to that of the ambient temperature phase of lanthanide‐doped derivatives, for example, Bi0.7Yb1.3WO6 recently reported. This phase‐transition behaviour is in stark contrast to that of other members of the Aurivillius family, such as SrBi2Ta2O9 and Bi4Ti3O12, which retain the archetypal Aurivillius connectivity at all temperatures.
A Starburst‐Shaped Heterometallic Compound Incorporating Six Densely Packed Gd3+ Ions
Authors: Livramento João Bruno , Sour Angélique , Borel Alain , Merbach André E. , Tóth Éva
Published: November 2005

The heterotritopic ligand [bpy(DTTA)2]8− has two diethylenediamine‐tetraacetate units for selective lanthanide(III) coordination and one bipyridine function for selective FeII coordination. In aqueous solution and in the presence of these metals, the ligand is capable of self‐assembly to form a rigid supramolecular metallostar structure, {Fe[Gd2bpy(DTTA)2(H2O)4]3}4−. We report here the physicochemical characterization of the dinuclear complex [Gd2bpy(DTTA)2(H2O)4]2− and the metallostar {Fe[Gd2bpy(DTTA)2(H2O)4]3}4− with regard to potential MRI contrast agent applications. A combination of pH potentiometry and 1H NMR spectroscopy has been used to determine protonation constants for the ligand [bpy(DTTA)2]8− and for the complexes [Fe{bpy(DTTA)2}3]22− and [Y2bpy(DTTA)2]2−. In addition, stability constants have been measured for the dinuclear chelates [M2bpy(DTTA)2]n− formed with M = Gd3+ and Zn2+ (log KGdL = 18.2; log KZnL = 18.0; log KZnHL = 3.4). A multiple field, variable‐temperature 17O NMR and proton relaxivity study on [Gd2bpy(DTTA)2(H2O)4]2− and {Fe[Gd2bpy(DTTA)2(H2O)4]3}4− yielded the parameters for water exchange and the rotational dynamics. The 17O chemical shifts are indicative of bishydration of the lanthanide ion. The exchange rates of the two inner‐sphere water molecules are very similar in the dinuclear [Gd2bpy(DTTA)2(H2O)4]2− and in the metallostar (kex298 = 8.1±0.3×106 and 7.4±0.2×106 s−1, respectively), and are comparable to kex298 for similar GdIII poly(amino carboxylates). The rotational dynamics of the metallostar has been described by means of the Lipari–Szabo approach, which involves separating global and local motions. The difference between the local and global rotational correlation times, τlO298 = 190±15 ps and τgO298 = 930±50 ps, respectively, shows that the metallostar is not completely rigid. However, the relatively high value of S2 = 0.60±0.04, describing the restriction of the local motions with regard to the global one, points to a limited flexibility compared with previously reported macromolecules such as dendrimers. As a result of the two inner‐sphere water molecules, with their near‐optimal exchange rate, and the limited flexibility, the metallostar has a remarkable molar proton relaxivity, particularly at high magnetic fields (r1 = 33.2 and 16.4 mM−1 s−1 at 60 and 200 MHz, respectively, at 25 °C). It packs six efficiently relaxing GdIII ions into a small molecular space, which leads, to the best of our knowledge, to the highest relaxivity per molecular mass ever reported for a GdIII complex. The [bpy(DTTA)2]8− ligand is also a prime candidate as a terminal ligand for constructing larger sized, FeII (or RuII)‐based metallostars or metallodendrimers loaded with GdIII on the surface.
Mollusk Shell Formation: A Source of New Concepts for Understanding Biomineralization Processes
Authors: Addadi Lia , Joester Derk , Nudelman Fabio , Weiner Steve
Published: November 2005

The biological approach to forming crystals is proving to be most surprising. Mollusks build their shells by using a hydrophobic silk gel, very acidic aspartic acid rich proteins, and apparently also an amorphous precursor phase from which the crystals form. All this takes place in a highly structured chitinous framework. Here we present ideas on how these disparate components work together to produce the highly structured pearly nacreous layer of the mollusk shell.
A Family of Ferro‐ and Antiferromagnetically Coupled Decametallic Chromium(III) Wheels
Authors: Low David M. , Rajaraman Gopalan , Helliwell Madeleine , Timco Grigore , van Slageren Joris , Sessoli Roberta , Ochsenbein Stefan T. , Bircher Roland , Dobe Christopher , Waldmann Oliver , Güdel Hans‐Ulrich , Adams Mark A. , Ruiz Eliseo , Alvarez Santiago , McInnes Eric J. L.
Published: November 2005

The synthesis and crystal structures of a family of decametallic CrIII “molecular wheels” are reported, namely [Cr10(OR)20(O2CR′)10] [R′=Me, R=Me (1), Et (2); R′=Et, R=Me (3), Et (4); R′=CMe3, R=Me (5), Et (6)]. Magnetic studies on 1–6 reveal a remarkable dependence of the magnetic behaviour on the nature of R. In each pair of complexes with a common carboxylate (R′) the nearest neighbour Cr⋅⋅⋅Cr magnetic exchange coupling is more antiferromagnetic for the ethoxide‐bridged (R=Et) cluster than for the methoxide analogue. In complexes 2, 4 and 6 the overall coupling is weakly antiferromagnetic resulting in diamagnetic (S=0) ground states for the cluster, whilst in 1 and 5 it is weakly ferromagnetic thus resulting in very high‐spin ground states. This ground state has been probed directly in the perdeuterated version of 1 ([D]1) by inelastic neutron scattering experiments, and these support the S=15 ground state expected for ferromagnetic coupling of ten CrIII ions, and they also indicate that a single J‐value model is inadequate. The ground state of 5 is large but not well defined. The trends in J on changing R are further supported by density functional calculations on 1–6, which are in excellent agreement with experiment. The very large changes in the nature of the ground state between 1 and 2, and 5 and 6 are the result of relatively small changes in J that happen to cross J=0, hence changing the sign of J.
A New Entry to Doubly N‐Confused [26]Hexaphyrins(1.1.1.1.1.1) from Normal [26]Hexaphyrins(1.1.1.1.1.1) through an Unprecedented Double Pyrrolic Rearrangement
Authors: Suzuki Masaaki , Yoon Min‐Chul , Kim Deok Yun , Kwon Jung Ho , Furuta Hiroyuki , Kim Dongho , Osuka Atsuhiro
Published: November 2005

Treatment of hexakis(pentafluorophenyl)‐substituted [26]hexaphyrin(1.1.1.1.1.1) (1) with CuCl in the presence of pyridine and molecular oxygen led to formation of doubly N‐confused [26]hexaphyrin(1.1.1.1.1.1) 2 in a moderate yield through an unprecedented double pyrrolic rearrangement. Macrocycle 2 has been shown to serve as an effective bis‐metal‐coordinating ligand and exhibits attractive optical properties such as a sharp Soret‐like band at 566 nm and low‐energy fluorescence at 1058 nm.
Treatment of local breast carcinoma in Florida
Authors: Voti Lydia , Richardson Lisa C. , Reis Isildinha M. , Fleming Lora E. , MacKinnon Jill , Coebergh Jan Willem W.
Published: November 2005

BACKGROUND

Breast‐conserving surgery combined with radiation (BCSR) is the recommended alternative treatment to mastectomy for local breast carcinoma. However, limited access to healthcare may result in more extensive surgical treatment. The effect of distance to radiation therapy facilities on the likelihood of receiving BCSR was examined in Florida.

METHODS

Local breast carcinomas reported to Florida's statewide registry between July, 1997, and December, 2000 were linked to the Agency of Healthcare Administration inpatient and outpatient databases to supplement the registry's treatment data, resulting in 18,903 local breast carcinoma cases treated with BCSR or mastectomy. The odds of receiving BCSR were modeled as a function of distance to the closest radiation therapy facility, adjusting for health insurance, age, race/ethnicity, and marital status.

RESULTS

Distance to the closest radiation therapy facility was negatively associated with BCSR, with the odds ratio (OR) decreasing by 3% per 5‐mile increase in distance. Compared with the uninsured, privately insured women were 49% more likely to receive BCSR (OR of 1.49; 95% confidence interval [95% CI], 1.20–1.86) and Medicare patients were 37% more likely (OR of 1.37; 95% CI, 1.09–1.72). Age at diagnosis was negatively associated, reducing the odds of BCSR by 1% per year increase in age. Compared with white non‐Hispanic, Hispanic women were 38% less likely to receive BCSR (OR of 0.62; 95% CI, 0.55–0.71). Married women were 23% more likely to receive BCSR compared with singles (OR of 1.23; 95% CI, 1.09–1.40); women who were separated, divorced, or widowed did not differ significantly from single women.

CONCLUSIONS

Distance to radiation therapy facilities may negatively impact the likelihood of BCSR in Florida. Age at diagnosis, insurance type, race/ethnicity, and marital status were associated with BCSR. Future efforts should target the uninsured, Hispanics, the elderly, and the unmarried women to reduce disparities in the administration of BCSR for local breast carcinoma. Cancer 2006. © 2005 American Cancer Society.
The impact of fluor‐18‐deoxyglucose‐positron emission tomography in the management of colorectal liver metastases
Authors: Wiering Bastiaan , Krabbe Paul F. M. , Jager Gerrit J. , Oyen Wim J. G. , Ruers Theo J. M.
Published: November 2005

Fluor‐18‐deoxyglucose‐positron emission tomography (FDG‐PET) has emerged as a promising diagnostic modality in recurrent colorectal carcinoma. Whole‐body FDG‐PET may be an accurate diagnostic modality to determine whether patients with recurrent hepatic disease are suitable candidates for curative resection. Reports on the use of FDG‐PET in patients with recurrent colorectal carcinoma are scarce, especially those on colorectal liver metastases. To assess the usefulness of this emerging modality for the selection of patients to undergo resection for colorectal liver metastases, a systematic (meta)‐analysis of the current literature was conducted. In the absence of randomized controlled clinical trials, a traditional meta‐analysis could not be performed. An alternative strategy was designed to evaluate the current literature. After a literature search, an index score was devised to evaluate the articles with regard to the impact of FDG‐PET in patients with colorectal liver metastases. The index scored articles on several items and, as such, could be considered an objective approach for the assessment of diagnostic, nonrandomized clinical trials. The proposed index proved to be an independent instrument for judging several research questions and was used systematically to address the sensitivity, specificity, and clinical impact of FDG‐PET in patients with colorectal liver metastases. For FDG‐PET, the pooled sensitivity and specificity results were 88.0% and 96.1%, respectively, for hepatic disease and 91.5% and 95.4%, respectively, for extrahepatic disease. For the 6 articles that reported the highest scores on the index, the sensitivity and specificity of FDG‐PET for hepatic metastatic disease were 79.9% and 92.3%, respectively, and 91.2% and 98.4%, respectively, for extrahepatic disease, respectively. For computed tomography, the pooled sensitivity and specificity results were 82.7% and 84.1%, respectively, for hepatic lesions and 60.9% and 91.1%, respectively, for extrahepatic lesions. The percentage change in clinical management due to FDG‐PET was 31.6% (range, 20.0–58.0%) in the articles that scored above the mean and reported this item. For the 6 highest scoring studies, the percentage change in clinical management was 25.0% (range, 20.0–32.0%). Despite apparent omissions in the literature, the combined sensitivity and specificity of FDG‐PET clearly indicated that FDG‐PET has added value in the diagnostic workup of patients with colorectal liver metastases. FDG‐PET can be considered a useful tool in preoperative staging and produced superior results compared with conventional diagnostic modalities, especially for excluding or detecting extrahepatic disease. Cancer 2005. © 2005 American Cancer Society.
The predictive value of apoptosis protease‐activating factor 1 in rectal tumors treated with preoperative, high‐dose‐rate brachytherapy
Authors: Zlobec Inti , Vuong Te , Compton Carolyn C.
Published: November 2005

BACKGROUND

The objective of this study was to assess the value of apoptosis protease‐activating factor 1 (APAF‐1) as a predictive marker of response in rectal tumors treated with preoperative, high‐dose‐rate endorectal brachytherapy.

METHODS

Immunohistochemistry for APAF‐1 was performed on 94 rectal tumor biopsy specimens from patients who were treated on a preoperative, high‐dose‐rate brachytherapy protocol. Tumors were considered positive when > 10% of tumor cells were immunoreactive. The association between APAF‐1 expression and tumor response was made using the chi‐square test.

RESULTS

Forty‐four tumors (43%) were positive for APAF‐1. Thirty tumors had complete pathologic tumor regression after preoperative radiotherapy. Of these, 18 tumors were positive for APAF‐1. A partial response occurred in 35 tumors. Eighteen tumors (51%) were positive for the protein. Only 8 of 29 nonresponsive tumors (28%) were immunoreactive for APAF‐1. A significant association was found between complete tumor regression and positive APAF‐1 status (P = 0.018). APAF‐1 expression in partially responsive tumors was significantly greater than in nonresponsive tumors (P = 0.03).

CONCLUSIONS

APAF‐1 expression in pretreatment rectal tumor biopsy specimens may be useful as a predictive marker of response to preoperative radiotherapy in patients with rectal carcinoma. Cancer 2006. © 2005 American Cancer Society.
From Molecular Double‐Ladders to an Unprecedented Polycatenation: A Parallel Catenated 3D Network Containing Bicapped Keggin Polyoxometalate Clusters
Authors: Shi Zhenyu , Gu Xiaojun , Peng Jun , Yu Xia , Wang Enbo
Published: November 2005

A new three‐dimensional coordination polymer, {Cu3(4,4′‐bpy)3(H2O)[PMo12O40(VO)2]·5H2O}n (1) (4,4′‐bpy = 4,4′‐bipyridine), which represents the first example of 3D polycatenation generated by unprecedented parallel catenation of the 1D double ladders, has been hydrothermally synthesized. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Self‐Assembly and Characterization of Homo‐ and Heterodinuclear Complexes of Zinc(II) and Lanthanide(III) Ions with a Tridentate Schiff‐Base Ligand
Authors: Patroniak Violetta , Stefankiewicz Artur R. , Lehn Jean‐Marie , Kubicki Maciej , Hoffmann Marcin
Published: November 2005

Tridentate Schiff‐base ligand HL (L = C12H9N2O) reacts with lanthanide(III) nitrates to give complexes of formulae [M2L3(NO3)3], where M = Y3+ (1), La3+ (2), Nd3+ (3), Sm3+ (4), Eu3+ (5), Gd3+ (6), Tb3+ (7), Dy3+ (8), Ho3+ (9), Lu3+ (10), and [MM1L3(NO3)x], where M = Eu3+, and M1 = Dy3+ (11), Zn2+ (12); x = 3 for 11 and 2 for 12. The structures of the complexes have been assigned on the basis of the spectroscopic data (solution analysis) and microanalyses. In the case of complexes 3, 5, 8 and 12 the structures have been confirmed by X‐ray crystallography. The structural analysis of the dinuclear complexes showed the presence of two metal atoms [M(1) and M(2)] and three ligands, L. Each lanthanide atom is coordinated to by 9 donor atoms with typical Ln–N and Ln–O distances. Zinc(II) is coordinated to by two oxygen atoms and four nitrogen atoms from two ligands. The metal ions are bridged by the phenoxo oxygen atoms of the ligands. We have obtained a heterodinuclear complex by a rapid one‐step reaction. Quantum mechanical calculations indicated that the formation of heterodinuclear complex 12 is slightly favored energetically over the homodinuclear complex 5. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
New C2‐ and C1‐Symmetric Phosphorus Ligands Based on Carbohydrate Scaffolds and Their Use in the Iridium‐Catalysed Hydrogenation of Ketimines
Authors: Guiu Ester , Aghmiz Mohamed , Díaz Yolanda , Claver Carmen , Meseguer Benjamí , Militzer Christian , Castillón Sergio
Published: November 2005

The C2‐symmetric diphosphinite ligands 10a–d, which have different electron‐donating or electron‐withdrawing groups in the aryl group, and C1‐symmetric phosphinite–phosphite ligands 11a,b, were directly prepared from glucosamine. Various procedures for synthesising the phosphinite function were explored in order to improve the yield of the reaction. Results were best when Ph2PNEt2 was used in the presence of tetrazol as catalyst. These ligands were added to iridium complexes to give catalyst precursors that are active in the hydrogenation of imines 17 and 19. Cationic iridium complexes gave rise to catalytic systems that were more active than the neutral iridium complexes. The use of additives was, in general, detrimental to both the conversion and the enantioselectivity. In the hydrogenation of 17, results were best with ligand 11a (76 % ee), but in the hydrogenation of 19 (70 % ee) they were best with ligand 10b. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Cover Picture: Synthesis and Properties of New Nucleotide Analogues Possessing Squaramide Moieties as New Phosphate Isosters (Eur. J. Org. Chem. 24/2005)
Authors: Seio Kohji , Miyashita Takuhei , Sato Kousuke , Sekine Mitsuo
Published: November 2005

The cover picture shows the electrostatic potential maps of methyl phosphate and N‐methylsquaramide. Various analogs of nucleotides and cyclic nucleotides were synthesized by use of the squaramide moiety as an isoelectronic mimic of the phosphate group. Details are discussed in the article by M. Sekine et al. on p. 5163 ff.
Recent advances in peptide and peptidomimetic stereoisomer separations by capillary electromigration techniques
Authors: Scriba Gerhard K. E.
Published: November 2005

As the stereochemistry of peptides determines their physicochemical properties and biological activities, analytical methods able to discriminate between peptide stereoisomers are important especially with regard to pharmaceutical peptides and peptidomimetics. The present review summarizes recent developments in peptide and peptidomimetic stereoisomer separations by capillary electromigration techniques. The majority of separations were performed by CE while only few reports have been published on the subject of electrochromatography. In addition to systematic studies on the applicability of certain buffer additives and the evaluation of specific experimental conditions, there have been attempts to understand the mechanistic aspects of peptide stereoisomer separations as well as to analyze the structure of peptide–CD complexes.
Progress in capillary electrophoresis of biomarkers and metabolites between 2002 and 2005
Authors: Huck Christian W. , Bakry Rania , Bonn Günther K.
Published: November 2005

Biomarker discovery and metabolite research is a fast‐growing and extremely important domain not only for the early detection of certain diseases but also for controlling its progress as well as in pharmaceutical investigations. For the analytical separation and identification, CE plays an indisputable role. Capillary systems enhancing different selectivity are applied and connected to different kind of detection systems. As the choice of buffer and its composition is responsible for a successful separation, special emphasis is put on solvent effects in this review. Altogether the most important capillary electrophoretic techniques applied for biomarker and metabolites analysis published between 2002 and 2005 are summarized and discussed.
Recent applications of affinity interactions in capillary electrophoresis
Authors: Schou Christian , Heegaard Niels H. H.
Published: November 2005

Systems biology depends on a comprehensive assignment and characterization of the interactions of proteins and polypeptides (functional proteomics) and of other classes of biomolecules in a given organism. High‐capacity screening methods are in place for ligand capture and interaction screening, but a detailed dynamic characterization of molecular interactions under physiological conditions in efficiently separated mixtures with minimal sample consumption is presently provided only by electrophoretic interaction analysis in capillaries, affinity CE (ACE). This has been realized in different fields of biology and analytical chemistry, and the resulting advances and uses of ACE during the last 2.5 years are covered in this review. Dealing with anything from small divalent metal ions to large supramolecular assemblies, the applications of ACE span from low‐affinity binding of broad specificity being exploited in optimizing selectivity, e.g., in enantiomer analysis to miniaturized affinity technologies, e.g., for fast processing immunoassay. Also, approaches that provide detailed quantitative characterization of analyte–ligand interaction for drug, immunoassay, and aptamer development are increasingly important, but various approaches to ACE are more and more generally applied in biological research. In addition, the present overview emphasizes that distinct challenges regarding sensitivity, parallel processing, information‐rich detection, interfacing with MS, analyte recovery, and preparative capabilities remain. This will be addressed by future technological improvements that will ensure continuing new applications of ACE in the years to come.
Recent applications of microemulsion electrokinetic chromatography
Authors: Huie Carmen W.
Published: November 2005

Compared to MEKC, the presence of a water‐immiscible oil phase in the microemulsion droplets of microemulsion EKC (MEEKC) gives rise to some special properties, such as enhanced solubilization capacity and enlarged migration window, which could allow for the improved separation of various hydrophobic and hydrophilic compounds, with reduced sample pretreatment steps, unique selectivities and/or higher efficiencies. Typically, stable and optically clear oil‐in‐water microemulsions containing a surfactant (SDS), oil (octane or heptane), and cosurfactant (1‐butanol) in phosphate buffer are employed as separation media in conventional MEEKC. However, in recent years, the applicability of reverse MEEKC (water‐in‐oil microemulsions) has also been demonstrated, such as for the enhanced separation of highly hydrophobic substances. Also, during the past few years, the development and application of MEEKC for the separation of chiral molecules has been expanded, based on the use of enantioselective microemulsions that contained a chiral surfactant or chiral alcohol. On the other hand, the application of MEEKC for the characterization of the lipophilicity of chemical substances remains an active and important area of research, such as the use of multiplex MEEKC for the high‐throughput determination of partition coefficients (log P values) of pharmaceutical compounds. In this review, recent applications of MEEKC (covering the period from 2003 to 2005) are reported. Emphases are placed on the discussion of MEEKC in the separation of chiral molecules and highly hydrophobic substances, as well as in the determination of partition coefficients, followed by a survey of recent applications of MEEKC in the analysis of pharmaceuticals, cosmetics and health‐care products, biological and environmental compounds, plant materials, and foods.
Recent advances in the application of capillary electrophoresis with mass spectrometric detection
Authors: Klampfl Christian W.
Published: November 2005

This review gives an overview of applications of CE coupled to MS detection published in the literature of the last three years. The works discussed in this paper comprise a wide range of different fields of application. These include important sections such as the analysis of biomolecules, the analysis of pharmaceuticals and their metabolites in different matrices, environmental analysis, and also investigations on the composition of technical products.
Recent applications in capillary electrochromatography
Authors: Eeltink Sebastiaan , Kok Wim Th.
Published: November 2005

In this review research papers on the application of CEC are summarized that have been published between May 2003 and May 2005. First, a short overview is given of trends and developments in CEC that may increase the applicability of the separation technique. Next, application‐oriented research using CEC is described in biochemical studies, including proteomics and genomics, in the analysis of food and natural products, and in pharmaceutical, industrial, and environmental analysis.
Pharmacokinetic applications of capillary electrophoresis: A review on recent progress
Authors: Sung Wang‐Chou , Chen Shu‐Hui
Published: November 2005

This article covers recent publications from 2003 to 2005 on the subject of pharmacokinetic applications of CE. Many analytical methods were validated and more importantly, they were shown to have sufficient sensitivities to access pharmacokinetic data on different models. Because of unique advantages, such as simplified sample preparation methods, small sample amount required, high separation power, and speedy analysis, CE‐based assays were found to gain popularity not only as a second method but also as a major method for many pharmacokinetic studies.
The role of astragaloside in regeneration of the peripheral nerve system
Authors: Cheng Chun‐Yuan , Yao Chun‐Hsu , Liu Bai‐Shuan , Liu Chien‐Ju , Chen Guan‐Wei , Chen Yueh‐Sheng
Published: November 2005

The aim of this study was to evaluate peripheral nerve regeneration across a 15‐mm gap in the sciatic nerve of the rat, using a silicone rubber nerve guide filled with different concentrations of astragaloside (0, 50, 100, and 200 μM). Collagen was also filled in the chambers to prevent the astragaloside from leakage. At the end of 8 weeks, animals from the group treated with astragaloside, especially at the concentration of 50 μM, had a higher rate of successful regeneration across the wide gap, a significantly larger number of myelinated axons, and a greater evoked action potential than the control group. However, the high‐dose astragaloside (200 μM) completely reversed this positive effect of growth‐promoting capability and inhibited nerve regeneration. Thus, astragaloside plays a dual role in anastomosis, being salutary in aiding the growth of axons in peripheral nerve but also detrimental, terminating the nerve regenerative processes if improperly applied. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res, 2006
Investigation into the erosion mechanism of salicylate‐based poly(anhydride‐esters)
Authors: Whitaker‐Brothers Kenya , Uhrich Kathryn
Published: November 2005

Salicylate‐based poly(anhydride‐esters), collectively referred to as PolyAspirin™, hydrolytically degrade into salicylic acid, a nonsteroidal anti‐inflammatory drug (NSAID). The variations of the poly(anhydride‐ester) investigated in this article are linked by adipic acid, suberic acid, or sebacic acid. To elucidate the erosion mechanism of these polymers, water uptake, mass loss, contact angle, and changes in device thickness were monitored as a function of in vitro degradation time. The polymers examined here appeared to primarily undergo surface erosion. The adipate homopolymer absorbed the most water and therefore swelled more than the other versions of the poly(anhydride‐ester). Additionally, the adipate homopolymer eroded most quickly. Increasing the length of the linker moiety decreased the driving force for hydrolysis, which prolonged the lifetime of the polymer sample. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res, 2006
Biocompatibility and degradation of aliphatic segmented poly(ester amide)s: In vitro and in vivo evaluation
Authors: Lips Priscilla A. M. , van Luyn Marja J. A. , Chiellini Federica , Brouwer Linda A. , Velthoen Ingrid W. , Dijkstra Piet J. , Feijen Jan
Published: November 2005

Aliphatic segmented poly(ester amide)s, comprising a crystallizable amide phase and a flexible amorphous ester phase, were investigated for potential use in biomedical applications. By varying the amide content and the type of crystallizable amide segments, the polymer's thermal and mechanical properties can readily be tuned. Polymers with 25 and 50 mol % of amide content are noncytotoxic and sustain growth of fibroblasts onto polymer films. The in vitro degradation of these polymers was followed in PBS (pH 7.4) at 37°C up to 7 months. The poly(ester amide)s showed the characteristics of bulk degradation with a gradual decrease in molecular weight and almost no mass loss. The in vivo degradation of these polymers, followed by subcutaneous implantation in rats up to 6 weeks, was slow and similar to the in vitro degradation. The tissue response upon implantation was followed over 6 weeks. A mild foreign‐body reaction, characterized by the presence of macrophages, and sporadically a lymphocyte, were observed in the first week of implantation. After 6 weeks the implant site is characterized by fibrous encapsulation with no signs of inflammation. The poly(ester amide)s tested are biocompatible, but their in vitro as well as in vivo degradation is very slow. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res, 2006
Chitosan monomer promotes tissue regeneration on dental pulp wounds
Authors: Matsunaga Tsunenori , Yanagiguchi Kajiro , Yamada Shizuka , Ohara Naoko , Ikeda Takeshi , Hayashi Yoshihiko
Published: November 2005

The present study was undertaken to evaluate the applicability of chitosan monomer (D‐glucosamine hydrochloride) as a pulp capping medicament. Bothin vitroandin vivoexperiments were carried out to study the cell metabolism and wound healing mechanisms following the application of chitomonosaccharide. After 3 days of osteoblast culture, alkaline phosphatase (ALP) activity significantly increased in the chitosan group. Reverse transcription polymerase chain reaction analysis revealed that chitosan induced an increase in the expression of ALP mRNA after 3 days and bone morphogenetic protein‐2 mRNA after 7 days of osteoblast incubation. Inflammatory cytokine, interleukin (IL)‐8, synthesis in fibroblasts was strongly suppressed in the medium supplemented with chitosan monomer. Histopathological effects were evaluated in rat experiments. After 1 day, inflammatory cell infiltrations were observed to be weak when compared with the application of chitosan polymer. After 3 days, a remarkable proliferation of fibroblasts was seen near the applied chitosan monomer. The inflammatory cell infiltration had almost completely disappeared. After 5 days, the fibroblastic proliferation progressed, and some odontoblastic cells appeared at the periphery of the proliferated fibroblasts. These findings indicate that the present study is the first report that chitosan monomer acts as a biocompatibly stable medicament even at the initial stage of wound healing in comparison with the application of chitosan polymer. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res, 2006
Rheological and cohesive properties of hyaluronic acid
Authors: Falcone Samuel J. , Palmeri David M. , Berg Richard A.
Published: November 2005

Hyaluronic acid (HA) is a naturally occurring polysaccharide with unique biomedical applications. We have studied the cohesive and rheological properties of HA of three molecular weights (0.35 × 106 –1.80 × 106 Da) and found that the cohesive nature of HA was highly dependent on molecular weight and solution concentration. To a first approximation, the cohesive nature of HA in solution correlates with concentration, independent of molecular weight. Several rheological parameters correlated with molecular weight: zero shear viscosity, complex viscosity, and the complex viscosity at the crossover point. The cohesive properties of the HA solutions, measured by dynamic aspiration (Poyer et al, J Cataract Refract Surg 1998;24:1130–1135), were found to decrease as the zero shear viscosity increases. The cohesive properties of HA polymer in solution were found to correlate with the high frequency complex viscosity and high frequency loss modulus independent of molecular weight. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res, 2006
Gene expression in the cell cycle of human T lymphocytes: I. Predicted gene and protein networks
Authors: Sivozhelezov V. , Giacomelli L. , Tripathi S. , Nicolini C.
Published: November 2005

The key genes involved in the cell cycle of human T lymphocytes were identified by iterative searches of gene‐related databases, as derived also from DNA microarray experimentation, revealing and predicting interactions between those genes, assigning scores to each of the genes according to numbers of interaction for each gene weighted by significance of each interaction, and finally applying several types of clustering algorithms to genes basing on the assigned scores. All clustering algorithms applied, both hierarchical and K‐means, invariably selected the same six “leader” genes involved in controlling the cell cycle of human T lymphocytes. Relations of the six genes to experimental data describing switching between stages of cell cycle of human T lymphocytes are discussed. J. Cell. Biochem. 97: 1137–1150, 2006. © 2005 Wiley‐Liss, Inc.
Gene expression in the cell cycle of human T‐lymphocytes: II. Experimental determination by DNASER technology
Authors: Nicolini Claudio , Spera Rosanna , Stura Enrico , Fiordoro Stefano , Giacomelli Luca
Published: November 2005

Human lymphocytes gene expression before and after PHA stimulation is monitored by DNASER technology, a novel bioinstrumentation entirely constructed in our laboratories as previously reported. The validity of the DNASER measurements is confirmed by standard fluorescence microscopy equipped with CCD. The human lymphocytes gene expression here experimentally probed using commercially available DNA microarrays such as Human Starter, appears compatible both with independent bioinformatic prediction and with existing experimental data, pointing to MYC as the key gene in the G0–G1 transition induced by PHA in resting lymphocytes. It does not escape our notice that in cell biology and cancer research DNASER technology based on microarray constructed with few leader genes identified from bioinformatics represents a meaningful cost‐effective route alternative to massive frequently misleading molecular genomics. J. Cell. Biochem. 97: 1151–1159, 2006. © 2005 Wiley‐Liss, Inc.
Regulation of DNA repair gene expression in human cancer cell lines
Authors: McGurk Claire J. , Cummings Michele , Köberle Beate , Hartley John A. , Oliver R. Timothy , Masters John R.
Published: November 2005

Although most advanced cancers are incurable, the majority of testicular germ cell tumors can be cured using cisplatin‐based combination chemotherapy. The nucleotide excision repair (NER) pathway removes most DNA adducts produced by cisplatin, and the low levels of NER in testis tumor cells may explain why these cancers are curable. Three NER proteins: ERCC1, XPF, and XPA, are present at low levels in testis tumor cell lines, and addition of these proteins to protein extracts of testis tumor cells increases their in vitro DNA repair capacity to normal levels. The aim of this study was to identify the mechanism responsible for the low levels of these DNA repair proteins. The levels of the mRNA transcripts for ERCC1, XPF, and XPA were measured in a panel of 14 different human cancer cell lines, using real‐time PCR. Three ERCC1 splice variants were identified and quantitated. Three alternative transcription start points (TSPs) were identified for ERCC1 but none were testis‐specific. The significantly lower levels of ERCC1, XPF, and XPA protein in testis tumor cell lines cannot be explained solely by differences in transcriptional efficiency or mRNA stability. For ERCC1, post‐transcriptional control by alternative splicing does not account for the testis‐specific low levels of protein expression. Pulse‐chase experiments showed that the half‐life of ERCC1 protein in a testis tumor cell line was not significantly different to that in a prostate cancer cell line. Taken together, these results suggest that constitutive levels of these DNA repair proteins are controlled at the level of translation. J. Cell. Biochem. 97: 1121–1136, 2006. © 2005 Wiley‐Liss, Inc.
Osteogenic differentiation of human mesenchymal stem cells is regulated by bone morphogenetic protein‐6
Authors: Friedman Michael S. , Long Michael W. , Hankenson Kurt D.
Published: November 2005

Bone marrow‐derived mesenchymal stem cells (MSC) are multipotent, self‐renewing, mesodermal‐origin stem cells that are sequestered in the endosteal compartment. MSC are maintained in a relative state of quiescence in vivo but in response to a variety of physiological and pathological stimuli, proliferate and differentiate into osteoblasts, chondrocytes, adipocytes, or hematopoiesis‐supporting stromal cells. Little is understood regarding the cellular or molecular events underlying MSC fate decisions. We report that human MSC (hMSC) cultured in defined, serum‐free conditions respond to a narrow spectrum of growth factors with osteogenic commitment, differentiation, and hydroxyapatite deposition. Of the osteogenic factors we examined, only treatment with bone morphogenetic protein (BMP) results in osteoinduction under defined serum‐free conditions. Among BMP‐2, 4, 6, and 7, BMP‐6 is the most consistent and potent regulator of osteoblast differentiation and, of these BMPs, only BMP‐6 gene expression is detected prior to hMSC osteoblast differentiation. Addition of exogenous BMP‐6 to hMSC induces the expression or upregulation of a repertoire of osteoblast‐related genes including type I collagen, osteocalcin, bone sialoprotein, and their regulatory transcription factors Cbfa1/Runx2, and Osterix. This translates into increased production of osteogenic extracellular matrix (ECM) with subsequent hydroxyapatite deposition. J. Cell. Biochem. 98: 538–554, 2006. © 2005 Wiley‐Liss, Inc.
Intracellular proteolytic activity of cathepsin B is associated with capillary‐like tube formation by endothelial cells in vitro
Authors: Premzl Aleš , Turk Vito , Kos Janko
Published: November 2005

The lysosomal cysteine protease cathepsin B is implicated in degradation of extracellular matrix (ECM), a crucial step in a variety of physiological and pathological processes, including tumor dissemination and angiogenesis. In this study, we analyzed the contribution of extracellular and intracellular cathepsin B activity on the formation of capillary‐like tubular structures by human umbilical vein endothelial cells (HUVECs) grown on Matrigel matrix, using general and specific cysteine protease inhibitors. We demonstrated, by confocal assay using quenched fluorescent protein substrate DQ‐collagen IV, that endothelial cells degrade ECM both intracellularly and pericellularly. Intracellular cathepsin B activity detected by degradation of Z‐Arg‐Arg cresyl violet substrate was co‐localized with the products of DQ‐collagen IV degradation in the perinuclear region and in the capillary‐like tubular structures. Treatment of cells with membrane‐permeable CA‐074 Me effectively abolished intracellular cathepsin B activity, and resulted in reduced tube length (32.3 ± 9.4% at 10 µM), total tubule area (49.6 ± 12.4% at 10 µM), and the number of branch points of tubules (47.5 ± 7.7% at 10 µM) in a dose‐dependent manner. In contrast, CA‐074 (0.1–10 µM), a membrane‐impermeable cathepsin B specific inhibitor, general cysteine protease inhibitors chicken cystatin (5 µM) and E‐64 (10 µM), and the metalloprotease inhibitor Minocycline (10 µM) showed no significant inhibitory effect in our angiogenesis model. These results show that, besides multiple regulatory molecules, intracellular cathepsin B also contributes to the neovascularization process and should be considered as a potential therapeutic target. J. Cell. Biochem. 97: 1230–1240, 2006. © 2005 Wiley‐Liss, Inc.
Reaction of nitrones with silyl ketene acetals: A DFT study
Authors: Milet Anne , Gimbert Yves , Greene Andrew E.
Published: November 2005

Theoretical calculations at the DFT level indicate that the reaction of a nitrone with a silyl ketene acetal proceeds, contrary to previous suggestions, through a classical 1,3‐dipolar cycloaddition, followed by a silyl group transfer step to give the open‐chain product. Introduction of a diffuse basis set is necessary to describe properly nitrones. The influence of a Lewis acid has been studied. © 2005 Wiley Periodicals, Inc. J Comput Chem 27: 157–162, 2006