bluuebunny/crossref_metadata_2025_split huggingface dataset:
Complex Formation of Divalent Metal Ions with Uridine 5′‐O‐Thiomonophosphate or Methyl Thiophosphate: Comparison of Complex Stabilities with Those of the Parent Phosphate Ligands
Authors: Da Costa Carla P. , Okruszek Andrzej , Sigel Helmut 
Published: July 2003

AbstractThe stability constants of the 1:1 complexes formed in aqueous solution between Mg2+, Ca2+, Sr2+, Ba2+, Mn2+, Co2+, Ni2+, Zn2+, or Cd2+ (M2+) and methyl thiophosphate (MeOPS2−) or uridine 5'‐O‐thiomonophosphate (UMPS2−) (PS2−=MeOPS2− or UMPS2−) have been determined (potentiometric pH titrations; 25 °C; I = 0.1 M, NaNO3). Comparison of these results for M(PS) complexes with those known for the parent M(PO) phosphate species, where PO2−=CH3OPO${_{3}^{2-}}$ or UMP2− (uridine 5′‐monophosphate), shows that the alkaline earth metal ions, as well as Mn2+, Co2+, and Ni2+ have a higher affinity for phosphate groups than for their thio analogues. However, based on the linear log K${_{{\rm M}({\rm R} \char45 {\rm PO}_{3})}^{{\rm M}}}$ versus pK${_{{\rm H}({\rm R} \char45 {\rm PO}_{3})}^{{\rm H}}}$ relationships (R‐PO${_{3}^{2-}}$=simple phosphate monoester or phosphonate ligands with a non‐interacting residue R) it becomes clear that the indicated observation is only the result of the lower basicity of the thiophosphate residue. In contrast, the thio complexes of Zn2+ and Cd2+ are more stable than their parent phosphate ones, and this despite the lower basicity of the PS2− ligands. This stability increase is identical for M(MeOPS) and M(UMPS) species and amounts to about 0.6 and 2.4 log units for Zn(PS) and Cd(PS), respectively. Since no other binding site is available in MeOPS2−, this enhanced stability has to be attributed to the S atom. Indeed, from the mentioned stability differences it follows that Cd2+ in Cd(PS) is coordinated by more than 99% to the thiophosphate S atom; the same value holds for Pb(PS), which was studied earlier. The formation degree of the Sbonded isomer amounts to 76±6 % for Zn(PS) and is close to zero for the corresponding Mg2+, Ca2+, and Mn2+ species. It is further shown that Zn(MeOPS)(aq)2+ releases a proton from a coordinated water molecule with pKa≈6.9; i.e., this deprotonation occurs at a lower pH value than that for the same reaction in Zn(aq)2+. Since Mg2+, Ca2+, Mn2+, and Cd2+ have a relatively low tendency for hydroxo complex formation, it was possible, for these M2+, to also quantify the stability of the binuclear complexes, M2(UMPS−H)+, where one M2+ is thiophosphate‐coordinated and the other is coordinated at (N3)− of the uracil residue. The impact of the results presented herein regarding M2+/nucleic acid interactions, including those of ribozymes (rescue experiments), is briefly discussed.
Acceptor Specificity and Inhibition of the Bacterial Cell‐Wall Glycosyltransferase MurG
Authors: Liu Haitian , Ritter Thomas K. , Sadamoto Reiko , Sears Pamela S. , Wu Min , Wong Chi‐Huey 
Published: July 2003

AbstractA continuous fluorescence coupled enzyme assay was developed to study the acceptor specificity of the glycosyltransferase MurG toward different lipid I analogues with various substituents replacing the undecaprenyl moiety. It was found that most lipid I analogues are accepted as substrates and, amongst these, the saturated C14 analogue exhibits the best activity. This substrate was used to evaluate the inhibition activity of such antibiotics as moenomycin, vancomycin, and two chlorobiphenyl vancomycin derivatives. A vancomycin derivative with a chlorobiphenyl moiety on the aglycon section was identified as a potent inhibitor of MurG.
Structures and Stabilities of Small DNA Dumbbells with Watson–Crick and Hoogsteen Base Pairs
Authors: Escaja Nuria , Gómez‐Pinto Irene , Rico Manuel , Pedroso Enrique , González Carlos 
Published: July 2003

AbstractThe structures and stabilities of cyclic DNA octamers of different sequences have been studied by NMR and CD spectroscopy and by restrained molecular dynamics. At low oligonucleotide concentrations, some of these molecules form stable monomeric structures consisting of a short stem of two base pairs connected by two mini‐loops of two residues. To our knowledge, these dumbbell‐like structures are the smallest observed to date. The relative stabilities of these cyclic dumbbells have been established by studying their melting transitions. Dumbbells made up purely of GC stems are more stable than those consisting purely of AT base pairs. The order of the base pairs closing the loops also has an important effect on the stabilities of these structures. The NMR data indicate that there are significant differences between the solution structures of dumbbells with G–C base pairs in the stem compared to those with A–T base pairs. In the case of dumbbells with G–C base pairs, the residues in the stem form a short segment of a BDNA helix stabilized by two Watson–Crick base pairs. In contrast, in the case of d〈pCATTCATT〉, the stem is formed by two A–T base pairs with the glycosidic angles of the adenine bases in a syn conformation, most probably forming Hoogsteen base pairs. Although the conformations of the loop residues are not very well defined, the thymine residues at the first position of the loop are observed to fold back into the minor groove of the stem.
Improvement of Hepatocyte‐Specific Gene Expression by a Targeted Colchicine Prodrug
Authors: van Rossenberg Sabine M. W. , Sliedregt‐Bol Karen M. , Koning Gerben , van den Elst Hans , van Berkel Theo J. C. , van Boom Jacques H. , van der Marel Gijs A. , Biessen Erik A. L. 
Published: July 2003

AbstractColchicine, an established tubulin inhibitor, interferes with the trafficking of endocytotic vesicles and thereby promotes the escape of lysosome‐entrapped compounds. To improve its potency and cell specificity, a targeted prodrug of colchicine was synthesized by conjugation to a high‐affinity ligand (di‐Nα,Nε‐(5‐(2‐acetamido‐2‐deoxy‐β‐D‐galactopyranosyloxy)pentanomido)lysine, K(GalNAc)2) for the asialoglycoprotein receptor on parenchymal liver cells. The resulting colchicine–K(GalNAc)2 conjugate bound to this receptor with an affinity of 4.5 nM. Confocal microscopy studies confirmed rapid uptake and receptor dependency of a prodrug conjugated with fluorescein isothiocyanate. Colchicine–K(GalNAc)2 substantially increased the transfection efficiency of polyplexed DNA in parenchymal liver cells in a concentration‐ and receptor‐dependent fashion. Colchicine–K(GalNAc)2 was found to enhance the transfection efficiency by 50‐fold at 1 nM, whereas the parental colchicine was ineffective. In conclusion, this nontoxic colchicine–K(GalNAc)2 conjugate can be a useful tool to improve the transfection efficiency of hepatic nonviral gene transfer vehicles.
Chemical Restriction: Strand Cleavage by Ammonia Treatment at 8‐Oxoguanine Yields Biologically Active DNA
Authors: Meyer Christoph , Meyer Dominik , Bickle Thomas A. , Giese Bernd 
Published: July 2003

AbstractCleavage of DNA single and double strands at an 8‐oxoguanine‐containing nucleotide occurs in 90 % yield if the modified oligonucleotide is treated with NH3 and O2 at 60 °C. The mechanism of this oxidative cleavage reaction was studied, and the reaction was applied to the generation of single‐stranded overhangs on PCR‐amplified DNA that can be ligated. As an example, the lac Z′ gene was amplified by PCR with 8‐oxoguanine modified primers, restricted by ammonia treatment, ligated into a plasmid vector, transformed in Escherischia coli cells, and screened for blue colonies. This method guarantees efficiencies comparable to the standard cloning procedure with restriction enzymes, and it allows the design of any 3′‐overhang independent of the sequence of the cloned DNA.
Synthetic Potential of Molluscan Sulfatases for the Library Synthesis of Regioselectively O‐Sulfonated D‐Galacto‐Sugars
Authors: Uzawa Hirotaka , Nishida Yoshihiro , Sasaki Kenji , Minoura Norihiko , Kobayashi Kazukiyo 
Published: July 2003

AbstractThe substrate specificities of three molluscan sulfatases (E.C. 3.1.6.1; snail, abalone, and limpet origins) were investigated with assorted p‐nitrophenyl (pNP) di‐O‐sulfonated β‐D‐galactopyranosides and β‐lactosides [3,6‐SO3 Gal (1), 3′,6′‐SO3 Lac (2), 4, 6SO3 Gal (3), 2,6‐SO3 Gal (4), 3,4‐SO3 Gal (5), and 3,6‐SO3 GalNAc (6); Ac, acetyl; Gal, galactose; Lac, lactose] together with mono‐O‐sulfonated β‐D‐galactopyranoside [pNP 3SO3‐Gal (7)] and tri‐O‐sulfonated α‐D‐galactopyranoside [2,3,6‐SO3‐α‐Gal (11)]. Some notable differences between the substrate specificity of the three sulfatases were disclosed; snail sulfatase hydrolyzed the 3O‐ and 2O‐sulfo groups of 1 and 4, respectively, to afford 6SO3 Gal (9) in high yields, while the abalone enzyme did not act on 4. Only the limpet enzyme could cleave the 3O‐sulfo groups of 7 to give pNP β‐galactoside. In contrast, every enzyme could utilize 11 as a good substrate to afford a mixture of 6SO3‐α‐Gal (13) and 2,6‐SO3 α‐Gal (12). None of the enzymes could cleave the O‐sulfo groups of 5 and 6, which indicates that a primary 6O‐sulfo group tends to promote the enzymatic hydrolysis of O‐sulfo groups at the secondary positions.
Cover Picture: Chemical Restriction: Strand Cleavage by Ammonia Treatment at 8‐Oxoguanine Yields Biologically Active DNA (ChemBioChem 7/2003)
Authors: Meyer Christoph , Meyer Dominik , Bickle Thomas A. , Giese Bernd 
Published: July 2003

AbstractThe cover picture shows a chemical restriction method in which DNA double strands are cleaved at the position of the artificial base 8‐oxoguanine (Goxo). As as result of the mild cleavage conditions, the DNA fragments remain biologically active and can be used in gene cloning experiments. As an example, the lac Z′ gene was amplified by PCR with 8‐oxoguanine‐modified primers, restricted by treatment with ammonia, ligated into a plasmid vector, transformed in Escherichia coli cells, and screened for blue colonies. This method guarantees efficiencies comparable to the standard cloning procedure, and allows the design of any 3′ overhang, independent of the sequence of the cloned DNA. Further information can be found in the article by Giese et. al. on pp. 610–614
Automatic detection and tracking of moving image target with CNN‐UM via target probability fusion of multiple features
Authors: Kim Hyongsuk , Roska Támas , Chua Leon O. , Werblin Frank 
Published: July 2003

AbstractA high speed target detection and tracking algorithm for a CNN‐UM chip is presented in this paper. The target confidence value is computed based on the fusion of target existence probabilities of features using products of weighted sums. The target decision is done with such a confidence value and target initiation is done through the temporal accumulation of the confidence. The probability of the target existence for each feature is created in the region of influence depending on the reliability and the strength of the feature. By virtue of the analogic parallel processing structure of the CNN‐UM (Roska T, Chua LO. The CNN universal machine: an analogic array computer. IEEE Trans. Circuits Systems II 1993;CAS‐40: 163–173), real time tracking can be achieved with presently available technologies with the speed of several kilo‐frames per second. Due to the utilization of multiple features of target, robust target detection is possible via the proposed algorithm. On‐chip experiments of the proposed target‐tracking algorithm have been done and properties of the proposed approach are disclosed through the various experiments. Copyright © 2003 John Wiley & Sons, Ltd.
Intercept measure of non‐linear stages
Authors: Larsen Torben 
Published: July 2003

AbstractIntercept points are often used to describe the non‐linear performance of transceiver stages. This letter introduces an intercept measure. The intercept measure is a performance parameter including both intercept point and gain parameters. Particularly for low gain stages the intercept measure is useful and is better to use than the traditional output intercept point. The intercept measure is very useful as a single non‐linear performance parameter. Copyright © 2003 John Wiley & Sons, Ltd.
Base coupled differential amplifier: a new topology for RF integrated LNA
Authors: Pascoli S. Di , Fanucci L. , Neri B. , Zito D. 
Published: July 2003

AbstractA new topology of bipolar low noise amplifier (LNA) for RF applications, named base coupled differential (BCD), is presented. The proposed approach is compared by simulation against most classical topologies. The BCD configuration has the key advantage to join an integrated matching on a single‐ended input with a differential output. This is done by using down‐bond wiring, so that no integrated inductors are needed. The main advantages of this new topology are a drastic area reduction and an increased linearity range (or a reduced biasing current with the same linearity) together with a noise figure (NF) and voltage supply reduction. Particularly, the BCD LNA presented in this paper has been designed for 2.44GHz frequency operation. It is characterized by a NF of 1.93dB, a voltage gain (Av) of 19.5dB, an input impedance of 50Ωa third Input‐referred Intercept Point (IIP3) of ‐7.25dBm and a dissipated power (PD) equal to 19mW. Copyright © 2003 John Wiley & Sons, Ltd.
A general approach to continuous‐time Gm‐C filters
Authors: Koziel S. , Szczepanski S. , Schaumann R. 
Published: July 2003

AbstractA general topology for transconductance‐capacitor (Gm‐C) filters is presented that permits any continuous‐time analogGm‐Cfilter to be analysed via a matrix‐description. Based on these matrices, explicit formulas are derived for the transfer function and the sensitivities valid for anyGm‐Cfilter topology. The approach leads to a useful relationship between the passive capacitor network of the filter and the degree of its transfer function. The matrix‐based approach is formulated especially for efficient use in computer‐aided analysis and design of Gm‐C filters, but ‘hand designs’ ofGm‐CIFLF and LF filters are given as illustrative examples. A new, more general definition ofGm‐Cstate‐space filters is proposed. Connections between the state matrices for voltage‐ and current‐mode state‐spaceGm‐Cfilters are formulated and two canonical transformations are defined that convert state‐space filters into direct state‐space ones, i.e. those having only grounded capacitors. Copyright © 2003 John Wiley & Sons, Ltd.
Output universality in maximum efficiency linear power amplifiers
Authors: Rhodes J. D. 
Published: July 2003

AbstractA general linear passive termination is considered for a typical field effect power transistor such that the first m odd harmonics, excluding the fundamental frequency, are open circuited with the remaining harmonics short‐circuited. Under this termination, with the appropriate resistive termination at the fundamental frequency, it is shown that an optimum maximum efficiency of

is universally achieved independent of non‐linearities in the transistor.Furthermore, where higher ordered harmonics are terminated in finite reactive impedances, which is the case with any realizable network, it is shown that the same maximum efficiency is obtained with the correct complex termination at the fundamental frequency.A prototype network is then defined including the output capacitance of the transistor and synthesized in a lowpass form which, when terminated in a shunt resonant circuit and load resistor, will provide the correct impedances at the fundamental and all of the harmonics. Remarkably, this optimum network has a simple formula for the element values in the general (2m+1) th degree network and a rigorous proof is presented in the appendix. Copyright © 2003 John Wiley & Sons, Ltd.
New results on periodic symbolic sequences of second order digital filters with two's complement arithmetic
Authors: Wing‐Kuen Ling Bingo , Kwong‐Shun Tam Peter 
Published: July 2003

AbstractIn this article, the second order digital filter with two's complement arithmetic in Reference 1 is considered. Necessary conditions for the symbolic sequences to be periodic after a number of iterations are given when the filter parameters are at b=a+1 and b=‐a+1. Furthermore, for some particular values of a, even when one of the eigenvalues is outside the unit circle, the system may behave as a linear system after a number of iterations and the state vector may toggle between two states or converge to a fixed point at the steady state. The necessary and sufficient conditions for these phenomena are given in this article. Copyright © 2003 John Wiley & Sons, Ltd.
A pseudo‐viscoelastic approach for transient polymeric flow exiting a channel
Authors: Khayat R. E. , Ashrafi N. 
Published: July 2003

AbstractThe influence of elasticity of a fluid exiting a channel is examined on transient coating downstream. A hybrid spectral/boundary element approach is proposed to solve the problem. The flow inside the channel is assumed to be fully developed. A viscoelastic instability of one‐dimensional plane Couette flow is first determined for a large class of Oldroyd fluids with added viscosity, which typically represent polymer solutions composed of a Newtonian solvent and a polymeric solute. The Johnson–Segalman equation is used as the constitutive model. The velocity profile inside the channel is taken as the exit profile for the emerging free‐surface flow. The flow is assumed to be Newtonian as it emerges from the channel. An estimate of the magnitude of the rate‐of‐strain tensor components in the free‐surface region reveals that they are generally smaller than the shear rate inside the channel. The evolution of the flow front is simulated using the boundary element method. For the channel flow, the problem is reduced to a nonlinear dynamical system using the Galerkin projection method. Stability analysis indicates that the channel velocity may be linear or non‐linear depending on the range of the Weissenberg number. The evolution of the coating flow at the exit is examined for steady as well as transient (monotonic and oscillatory) channel flow. It is found that adverse flow can exist as a result of fluid elasticity, which can hinder the process of blade coating. Copyright © 2003 John Wiley & Sons, Ltd.
C‐reactive protein and depressed mood in a sub‐group of smokers during nicotine abstinence
Authors: Corwin Elizabeth J. , Klein Laura Cousino 
Published: July 2003

AbstractCigarette smokers frequently fail multiple attempts to quit smoking, often because of the unpleasant symptoms that accompany quitting. Similar unpleasant symptoms accompany inflammatory responses during infection and autoimmune disease. The hypothesis that smoking abstinence induces inflammation was tested. Eighteen smokers (n = 18) were evaluated while smoking freely and after 24 h of nicotine abstinence. Immune, cardiovascular and psychological measures were collected. Hunger, nervousness, anxiety, restlessness and irritability increased during abstinence (p < 0.05); systolic blood pressure and heart rate levels decreased (p < 0.05). Analysis demonstrated a split among smokers in response to abstinence compared with smoking freely; some smokers (n = 10) displayed increased C‐reactive protein (CRP, p < 0.05) whereas others (n = 8) responded with decreased CRP (p < 0.05). An increase in symptoms of depressed mood and a fall in heart rate occurred only in those who displayed increased CRP with nicotine abstinence ( p < 0.05), while systolic blood pressure fell only in those whose CRP levels decreased with abstinence ( p < 0.05). Interleukin‐1 and interleukin‐6 did not change with abstinence. The results suggest that 24 h nicotine abstinence does not stimulate inflammation among all smokers, but that a sub‐group of smokers do demonstrate an inflammatory response with significant negative psychological and physiological symptomatology. Copyright © 2003 John Wiley & Sons, Ltd.
Effects of transdermal nicotine on lateralized identification and memory interference
Authors: McClernon F. Joseph , Gilbert David G. , Radtke Robert 
Published: July 2003

AbstractIt has been proposed that nicotine may enhance performance on tasks requiring primarily left hemisphere (LH) resources while impairing right hemisphere (RH)‐based performance. However, this hypothesis has not been directly tested using a lateralized cognitive task. The effects of transdermal nicotine administration on lateralized consonant identification and memory interference were examined in dependent smokers and never‐smokers. In a double‐blind placebo‐controlled design, smokers (n = 24) and never‐smokers (n = 24) were assigned to receive a nicotine or placebo patch. Subjects completed a lateralized letter identification task that required them to identify strings of three consonants presented in the left or right visual field while keeping a word in memory. A distinct right‐visual‐field (RVF) advantage was observed for consonant identification, but this effect was unaltered by nicotine or smoking status. However, nicotine decreased word memory errors on trials where consonants were presented in the RVF and increased errors on LVF trials. Nicotine may enhance LH‐based cognitive performance by increasing LH cognitive resources or by reducing the influence of RVF distracting stimuli. These findings are consistent with a model of the lateralized effects of nicotine on cognitive performance. Copyright © 2003 John Wiley & Sons, Ltd.
The platelet‐poor plasma 5‐HT response to carbohydrate rich meal administration in adult autistic patients compared with normal controls
Authors: Vered Yaffa , Golubchik Pavel , Mozes Tamar , Strous Rael , Nechmad Allon , Mester Roberto , Weizman Abraham , Spivak Baruch 
Published: July 2003

AbstractThere are cumulative data indicating involvement of the 5‐HT system in autistic disorder. Most studies examining 5‐HT function have focused on whole blood 5‐HT content. The carbohydrate‐rich meal test (CRMT) is a dietary manipulation that could significantly influence platelet‐poor plasma (PPP) 5‐HT levels and reflect the responsiveness of the serotonergic system in ‘free’ plasma. In this study, CRMT was used as an indicator of 5‐HT responsivity in drug‐free adults with autistic disorder (n = 7), compared with normal controls (n = 10). The PPP 5‐HT levels were measured at baseline and during 3 h after administration of the CRMT. A significant elevation in PPP 5‐HT levels in adult autistic patients was reached 60 min after meal administration (p < 0.03 vs control and p = 0.05 vs baseline) and a significant decrease was noted after 120 min (p < 0.01 vs baseline). In contrast to the biphasic response of the autistic patients, normal controls exhibited a gradual linear increase of PPP 5‐HT levels. Our results indicate that in adult autistic patients, the pattern of PPP 5‐HT responsivity to a dietary challenge of CRMT is dysregulated compared with normal controls and provide further support for the role of 5‐HT in autism. Copyright © 2003 John Wiley & Sons, Ltd.