bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of naturally‐occurring 5′‐pyrophosphate‐linked substituents on the binding of adenylic inhibitors to ribonuclease a: An X‐ray crystallographic study
Authors: Holloway Daniel E. , Chavali Gayatri B. , Leonidas Demetres D. , Baker Matthew D. , Acharya K. Ravi 
Published: February 2009

AbstractRibonuclease A is the archetype of a functionally diverse superfamily of vertebrate‐specific ribonucleases. Inhibitors of its action have potential use in the elucidation of the in vivo roles of these enzymes and in the treatment of pathologies associated therewith. Derivatives of adenosine 5′‐pyrophosphate are the most potent nucleotide‐based inhibitors known. Here, we use X‐ray crystallography to visualize the binding of four naturally‐occurring derivatives that contain 5′‐pyrophosphate‐linked extensions. 5′‐ATP binds with the adenine occupying the B2 subsite in the manner of an RNA substrate but with the γ‐phosphate at the P1 subsite. Diadenosine triphosphate (Ap3A) binds with the adenine in syn conformation, the β‐phosphate as the principal P1 subsite ligand and without order beyond the γ‐phosphate. NADPH and NADP+ bind with the adenine stacked against an alternative rotamer of His119, the 2′‐phosphate at the P1 subsite, and without order beyond the 5′‐α‐phosphate. We also present the structure of the complex formed with pyrophosphate ion. The structural data enable existing kinetic data on the binding of these compounds to a variety of ribonucleases to be rationalized and suggest that as the complexity of the 5′‐linked extension increases, the need to avoid unfavorable contacts places limitations on the number of possible binding modes. © 2009 Wiley Periodicals, Inc. Biopolymers 91: 995–1008, 2009.This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
Optimization of elastin‐like polypeptide fusions for expression and purification of recombinant proteins in plants
Authors: Conley Andrew J. , Joensuu Jussi J. , Jevnikar Anthony M. , Menassa Rima , Brandle Jim E. 
Published: February 2009

AbstractThe demand for recombinant proteins for medical and industrial use is expanding rapidly and plants are now recognized as an efficient, inexpensive means of production. Although the accumulation of recombinant proteins in transgenic plants can be low, we have previously demonstrated that fusions with an elastin‐like polypeptide (ELP) tag can significantly enhance the production yield of a range of different recombinant proteins in plant leaves. ELPs are biopolymers with a repeating pentapeptide sequence (VGVPG)n that are valuable for bioseparation, acting as thermally responsive tags for the non‐chromatographic purification of recombinant proteins. To determine the optimal ELP size for the accumulation of recombinant proteins and their subsequent purification, various ELP tags were fused to green fluorescent protein, interleukin‐10, erythropoietin and a single chain antibody fragment and then transiently expressed in tobacco leaves. Our results indicated that ELP tags with 30 pentapeptide repeats provided the best compromise between the positive effects of small ELP tags (n = 5–40) on recombinant protein accumulation and the beneficial effects of larger ELP tags (n = 80–160) on recombinant protein recovery during inverse transition cycling (ITC) purification. In addition, the C‐terminal orientation of ELP fusion tags produced higher levels of target proteins, relative to N‐terminal ELP fusions. Importantly, the ELP tags had no adverse effect on the receptor binding affinity of erythropoietin, demonstrating the inert nature of these tags. The use of ELP fusion tags provides an approach for enhancing the production of recombinant proteins in plants, while simultaneously assisting in their purification. Biotechnol. Bioeng. 2009;103: 562–573. © 2009 Wiley Periodicals, Inc.
Parameters Influencing the Release of Tertiary Alcohols from the Surface of “Spherical” Dendrimers and “Linear” Stylomers by Neighbouring‐Group‐Assisted Hydrolysis of 2‐Carbamoylbenzoates
Authors: Trachsel Alain , de Saint Laumer Jean‐Yves , Haefliger Olivier P. , Herrmann Andreas 
Published: February 2009

AbstractSize is not all! Investigation of the controlled release of tertiary alcohols from the surface of dendrimers and “stylomers” as polymer model systems (see scheme) showed that the polarity of the conjugates and structural modifications in close proximity to the release unit have a stronger influence on the rates of hydrolysis than the size (generation) or shape (linear or spherical) of the macromolecules.magnified imageThe influence of structural and physico‐chemical parameters on the release of a volatile tertiary alcohol (2‐methyl‐1‐phenyl‐2‐propanol) by neighbouring‐group‐assisted cyclisation of 2‐carbamoylbenzoates at neutral pH was investigated by comparing the covalent‐bond cleavage from the surface of linear, comblike poly(propylene imine) “stylomers” and their corresponding spherical, globular dendrimers. Determination of the kinetic rate constants for the stepwise intramolecular cyclisation of the 2‐carbamoylbenzoate moiety by using HPLC showed that the polarity of the conjugates, and thus their solubility in the aqueous reaction medium, has a stronger influence on the rates of hydrolysis than the size (generation) or shape (linear or spherical) of the macromolecules. Furthermore, structural modifications in close proximity to the release unit, such as the presence of functionalities with catalytic activity, have a strong impact on the release efficiency of the active molecules. An understanding of the physico‐chemical parameters determining the local environment of the covalent‐bond cleavage site is therefore an important prerequisite to transfer the characteristics of small molecules to larger structures such as oligomers and polymers and thus to design efficient macromolecular conjugates for the controlled delivery of bioactive compounds.
The Quest for Ring Opening of Oxaphosphirane Complexes: A Coupled‐Cluster and Density Functional Study of CH3PO Isomers and Their Cr(CO)5 Complexes
Authors: Krahe Oliver , Neese Frank , Streubel Rainer 
Published: February 2009

AbstractOpening gambit: A high‐level theoretical study on the relative stabilities of oxaphosphirane isomers and their Cr(CO)5 complexes is reported (see picture). Furthermore, thermodynamics and kinetics of possible ring‐opening reactions of these complexes in the presence of a {Cp2TiIIICl} fragment are theoretically investigated. The CO bond cleavage is predicted to be the most efficient pathway, thus leading to reactive intermediates that are attractive for synthetic applications.magnified imageA high‐level theoretical study on the relative stabilities of oxaphosphirane isomers and their Cr(CO)5 complexes is reported. Furthermore, thermodynamics and kinetics of possible ring‐opening reactions of these complexes in the presence of a {Cp2TiIIICl} fragment are theoretically investigated. The CO bond cleavage is predicted to be the most efficient pathway thus leading to reactive intermediates that are attractive for synthetic applications. The ring‐opening reaction is predicted to not lead to the most favorable product (a coordinated phosphinidene oxide species). Rather, the ring‐opening product is separated by a substantial barrier of about 24 kcal mol−1 from the thermodynamically most favorable species.
Two‐Dimensional Oligo(phenylene‐ethynylene‐butadiynylene)s: All‐Covalent Nanoscale Spoked Wheels
Authors: Lei Shengbin , Ver Heyen An , De Feyter Steven , Surin Mathieu , Lazzaroni Roberto , Rosenfeldt Sabine , Ballauff Matthias , Lindner Peter , Mössinger Dennis , Höger Sigurd 
Published: February 2009

AbstractRound and round: Covalently bound spokes induce an efficient template‐directed cyclization towards a rigid molecular wheel (see figure) and afford dramatically increased shape‐persistence properties compared with non‐strutted macrocycles.magnified imageThe synthesis and characterization of a shape‐persistent two‐dimensional (2D) organic compound is described in detail. In a rational modular synthesis of a dodecaacetylene precursor and its subsequent template‐aided cyclization, we obtained a molecularly defined, stable, C6‐symmetric, rigid, spoked wheel. Peripheral tert‐butyl groups and alkyl chains attached to the plane of the molecule provide sufficient solubility, so that the 2D oligomer can be fully characterized by MALDI‐MS, GPC, and 1H NMR, UV/Vis absorption, and fluorescence spectroscopy. Molecular mechanics and dynamics simulations indicate that the most stable conformer of the molecule in vacuum is a shallow boat conformation with a small dihedral angle. Comparisons with the precursor as well as a ring‐only structure clearly reveal the high rigidity of the title compound. Small‐angle neutron scattering (SANS) experiments in [D8]THF and CDCl3 affirm the rigid backbone structure in solution, that is, a radius of about 2.7 nm and a thickness of about 0.22 nm. STM investigations illustrate that the wheel molecules adsorb with their molecular plane parallel to the surface and can form hexagonal crystalline domains (unit cell parameters are a=b=6.0±0.2 nm and θ=60±2°), with the tert‐butyl groups on the apexes staggered. Such staggering induces chirality in the organized domains. AFM investigations demonstrate that the wheel molecules inside overlayers organize in the same way as in the layer directly in contact with the surface. This indicates an epitaxial growth characteristic of the film.
New Polyalkynyl Dendrons and Dendrimers: “Click” Chemistry with Azidomethylferrocene and Specific Anion and Cation Electrochemical Sensing Properties of the 1,2,3‐Triazole‐Containing Dendrimers
Authors: Camponovo Jérémy , Ruiz Jaime , Cloutet Eric , Astruc Didier 
Published: February 2009

AbstractDendrimers for ion sensing: The synthesis and use of new tris‐alkynyl dendrons are reported. So‐called “click” reactions of the dendrimers described with azidomethylferrocene give 27‐ferrocenyl, 81‐ferrocenyl, and 243‐ferrocenyl dendrimers. Electrochemical recognition of oxo‐anions and Pd2+ cations has been compared using the three polyferrocenyl dendrimers.magnified imageThe synthesis and use of the new tris‐alkynyl dendrons 2 to 5 are reported, including the Williamson reaction of 5 with 9‐iodo (9), 27‐iodo (11), and 81‐iodo (12) dendritic cores to yield 27‐alkynyl (13), 81‐alkynyl (14), and 243‐alkynyl (15) dendrimers. So‐called “click” reactions of these three dendrimers with azidomethylferrocene (20) give 27‐ferrocenyl (16), 81‐ferrocenyl (17), and 243‐ferrocenyl (18) dendrimers. Electrochemical recognition of oxo‐anions (H2PO4− and ATP2−) and Pd2+ cation has been compared using the three polyferrocenyl dendrimers. Derivatization of Pt electrodes with the dendrimers for recognition becomes more facile with increasing size of the dendrimer. This first “click” dendrimer bearing 243‐ferrocenyl groups is the best one in the series to obtain robust, recyclable modified Pt electrodes, whereas previous “click” ferrocenyl dendrimers have not been suitable for this purpose.
Palladium‐Catalyzed Cyclopropanation of Alkenyl Silanes by Diazoalkanes: Evidence for a Pd0 Mechanism
Authors: Berthon‐Gelloz Guillaume , Marchant Mélanie , Straub Bernd F. , Marko Istvan E. 
Published: February 2009

AbstractPd0 does the trick! Alkenyl silanes are efficiently cyclopropanated by diazoalkanes at low Pd loadings (see scheme). Clear evidence for the involvement of a Pd0 resting state for this reaction is given.magnified imageAlkenyl silanes are efficiently converted to the corresponding silyl cyclopropanes in the presence of a slight excess of diazomethane (2–4 equiv) and a low loading of Pd(OAc)2 (<0.5 mol %). Diazoethane and diazobutane can also be employed and yield silyl cyclopropanes with diastereoselectivities of up to 10:1 for the trans isomer. When conducted on a 4 g scale, the reaction only required a catalyst loading of 5×10−3 mol %, which corresponds to a turnover frequency of 40 000 h−1. Competition experiments revealed that vinyl silanes can be selectively cyclopropanated in the presence of an aliphatic terminal alkene and styrene. The complex [Pd02(DVTMS)3] (38, DVTMS=divinyltetramethyldisiloxane) proved to be an exceptionally active catalyst for the cyclopropanation reaction, giving complete conversion at −35 °C in 1 min. Intermolecular and intramolecular competition experiments with DVTMS (36), both with Pd(OAc)2 and 38, provided strong evidence for a Pd0(alkenyl silane)3 resting state. Detailed density functional calculations on the reaction pathways for the cyclopropanation of trimethylvinylsilane and DVTMS by diazomethane with Pd0 corroborated the experimental observations.
Enantioselective Total Synthesis of (−)‐Candelalides A, B and C: Potential Kv1.3 Blocking Immunosuppressive Agents
Authors: Oguchi Takamasa , Watanabe Kazuhiro , Ohkubo Kôichi , Abe Hideki , Katoh Tadashi 
Published: February 2009

AbstractPotential immunosuppressive agents: Candelalides A, B and C (see figure), novel blockers of the voltage‐gated potassium channel Kv1.3, have been efficiently synthesized for the first time in a convergent and unified manner starting from (+)‐5‐methyl‐Wieland–Miescher ketone. The method explored has potential for preparing various types of candelalide analogues for the structure–activity relationship studies.magnified imageNovel Kv1.3 blocking immunosuppressants, (−)‐candelalides A, B and C, were efficiently synthesized for the first time in a convergent and unified manner starting from (+)‐5‐methyl‐Wieland–Miescher ketone. The synthetic method involved the following key steps: i) a strategic [2,3]‐Wittig rearrangement of a stannylmethyl ether to install the stereogenic center at C9 and the exo‐methylene function at C8 present in the decalin portion; ii) a straightforward coupling of a trans‐decalin portion (BC ring) and a γ‐pyrone moiety through the C16C3′ bond to assemble the requisite carbon framework; and iii) a construction of a characteristic di or tetrahydropyran ring (A ring) by internal nucleophilic ring closure of a hydroxy aldehyde or a hydroxy epoxide. The present total synthesis has fully established the absolute configuration of these natural products.
Optical Response Sensitive to the Assembly in a Molecular Material: Ultrathin Film with a Vanishing Electronic Absorption
Authors: Rajesh K. , Radhakrishnan T. P. 
Published: February 2009

AbstractThe characteristic electronic absorption of a zwitterionic molecule arising from an intramolecular charge‐transfer transition observed in the solution and the bulk solid states vanishes completely when the molecules are assembled into mono‐ and multilayer Langmuir–Blodgett films (see figure). Microscopy and spectroscopy investigations and computational modeling provide insight into this remarkable phenomenon.magnified imageOptical properties of single‐component molecular materials can often be described in terms of modest perturbations on the responses of the molecular building blocks; in specific systems, the modifications may be more pronounced. In all cases, however, the effects are broadly independent of the form of assembly, such as thin films, nanostructures and crystals, even though variations may exist at the quantitative level. We present a very different situation encountered with an amphiphilic molecule possessing a strongly polar head group that shows similar electronic absorption spectra in the solution as well as the bulk solid state, but a dramatically different one in ultrathin Langmuir–Blodgett (LB) films. The lowest energy absorption is switched off completely in the latter. It is demonstrated further that a metastable form of the LB film exhibiting the normal molecular spectrum can be generated, although its lowest energy absorption decays and vanishes over a period of time. The Langmuir films formed at the air/water interface and the corresponding LB films are examined through pressure–area isotherms, microscopy and spectroscopy. The experimental observations coupled with models constructed through computational investigations allowed us to interpret the unusual optical responses, which are a result of the specific supramolecular 2D assembly in the LB film and the impact of the neighboring molecular dipoles on the intramolecular charge transfer transition. The present study illustrates that selective molecular design and directed assembly can be exploited to elicit dramatic changes in physical responses of molecular materials and realize novel effects in molecular nanostructures.
Solid‐State Enantiopure Organic Nanocubes Formed by Self Organization of a C3‐Symmetrical Tribenzotriquinacene
Authors: Strübe Jörg , Neumann Beate , Stammler Hans‐Georg , Kuck Dietmar 
Published: February 2009

AbstractCubic aggregation: The racemic C3‐symmetrical tribenzotriquinacene 1 was synthesized and found to crystallize in cubic aggregates consisting of eight homochiral molecules. The major driving force for this unique supramolecular aggregation may be attributed to the 24 equivalent sub‐van der Waals interactions between the bromine atoms located at the convex surface of the triquinacene cores, rather than to polar interactions between the nitrobenzene units within and between the nanocubes.magnified image
Photo‐Induced Spin Transition of Iron(III) Compounds with π–π Intermolecular Interactions
Authors: Hayami Shinya , Hiki Kenji , Kawahara Takayoshi , Maeda Yonezo , Urakami Daisuke , Inoue Katsuya , Ohama Mitsuo , Kawata Satoshi , Sato Osamu 
Published: February 2009

AbstractPhoto‐switching: The LIESST effect could be observed by introducing π–π intermolecular interaction even for iron(III) spin‐crossover (SCO) compounds being the relatively small ΔrHL. Introduction of strong intermolecular interactions can be widely used in the design of a variety of optically switchable molecules (see figure).magnified imageIron(III) spin‐crossover compounds [Fe(pap)2]ClO4 (1), [Fe(pap)2]BF4 (2), [Fe(pap)2]PF6 (3), [Fe(qsal)2]NCS (4), and [Fe(qsal)2]NCSe (5) (Hpap=2‐(2‐pyridylmethyleneamino)phenol and Hqsal=2‐[(8‐quinolinylimino)methyl]phenol) were prepared and their spin‐transition properties investigated by magnetic susceptibility and Mössbauer spectroscopy measurements. The iron(III) compounds exhibited spin transition with thermal hysteresis. Single crystals of the iron(III) compounds were obtained as suitable solvent adducts for X‐ray analysis, and structures in high‐spin (HS) and low‐spin (LS) states were revealed. Light‐induced excited‐spin‐state trapping (LIESST) effects of the iron(III) compounds were induced by light irradiation at 532 nm for 1–3 and at 800 nm for 4 and 5. The activation energy Ea and the low‐temperature tunneling rate kHL(T→0) of iron(III) LIESST compound 1 were estimated to be 1079 cm−1 and 2.4×10−8 s−1, respectively, by HS→LS relaxation experiments. The Huang–Rhys factor S of 1 was also estimated to be 50, which was similar to that expected for iron(II) complexes. It is thought that the slow relaxation in iron(III) systems is achieved by the large structural distortion between HS and LS states. Introduction of strong intermolecular interactions, such as π–π stacking, can also play an important role in the relaxation behavior, because it can enhance the structural distortion of the LIESST complex.
Evaluation of hypertensive males for primary coronary heart disease events using conventional risk factors and maximal exercise testing
Authors: Hossack K. F. , Bruce R. A. , De ROUEN T. A. 
Published: February 2009

AbstractWhereas hypertension is a risk factor for primary coronary heart disease events, the relative contributions of other risk factors and abnormal responses to symptom‐limited maximal exercise are not well‐established. After 5.2±1.5 years of follow‐up of 633 men with clinically‐diagnosed hypertension based upon criteria of examining physicians (whether or not the men were currently treated for hypertension), 54 primary events were revealed. The annual coronary heart disease (CHD) event rate of 16.9/1000 men at risk was significantly higher than the annual rate of 3.6/1000 found for healthy men (p<0.0001).Variables associated with increased risk were smoking cigarettes, risk factor count or tally, chest pain during exercise, percentage of functional aerobic impairment, and percentage heart rate impairment, the latter two variables suggesting early evidence of left ventricular dysfunction on strenuous exertion. Ischemic ST depression was not an important predictor. The three exercise variables were included in an exercise predictor count, and multivariate analysis revealed that this count and the risk factor count were the most important predictors of primary CHD events. Combining the risk factor count and the exercise predictor count, three groups with increasing risk of primary CHD events were identified. In those persons with both a risk factor count and exercise predictor count of zero, the annual rate was 7.3 events/1000 man‐years; when either count was one or more, the rate was 15.5 events/1000 man‐years; when both counts were one or more, the rate was 49.5 events/1000 man‐years.
The distribution and severity of coronary artery disease and left ventricular dysfunction among patients with single coronary artery disease and angina pectoris
Authors: Vieweg W. V. R. , Warren S. E. , Alpert J. S. , Hagan A. D. 
Published: February 2009

AbstractThe distribution and severity of coronary artery disease and left ventricular dysfunction were evaluated in 103 patients with single coronary artery disease and angina pectoris. The coronary arterial patterns were separated into right (76), mixed (18), and left (9) systems depending upon the blood supply to the inferior surface of the left ventricle. The following relationships were noted:(1) In patients with single coronary artery disease and angina pectoris, coronary arterial lesions are similar among right, mixed, and left systems.(2) In order of frequency, single coronary artery disease occurred most commonly in the left anterior descending coronary artery (55), next most commonly in the right coronary artery (36), and least commonly in the circumflex/obtuse marginal coronary artery (12).(3) Left ventricular wall motion abnormalities were seen in descending order of frequency: patients with right coronary artery (50%), left anterior descending coronary artery (36%), and circumflex/obtuse marginal coronary artery (25%) disease.
Coronary arterial and left ventriculographic findings in patients with double‐vessel disease and angina pectoris
Authors: Vieweg W. V. R. , Warren S. E. , Alpert J. S. , Hagan A. D. 
Published: February 2009

AbstractThe distribution and severity of coronary artery disease and left ventricular wall abnormalities are described in 119 patients with double‐vessel disease and angina pectoris. The coronary arterial patterns were divided into right (84), mixed (17), and left (18) systems, depending upon the blood supply to the inferior surface of the left ventricle. Patterns of double‐vessel disease were separated into those with 50% or greater reduction of luminal diameter involving the left anterior descending and circumflex/obtuse marginal arteries (2‐LC), circumflex/obtuse marginal and right coronary arteries (2‐CR), and left anterior descending and right coronary arteries (2‐LR). The following relationships were noted:(1) Left anterior descending and right coronary artery disease occurs with twice the frequency of 2‐LC or 2‐CR disease, supporting the thesis that of the three major coronary arteries, the circumflex/obtuse marginal arteries contribute least to angina pectoris.(2) The mid portion of the left anterior descending artery is most commonly involved and the left main coronary artery least commonly involved in patients with double‐vessel disease.(3) Left ventricular wall motion abnormalities are found in one‐half of patients with double‐vessel disease and angina pectoris with hypokinesis usually found in all areas except at the apex where dyskinesis is usually seen.