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PubMed2006

Effect of Ni and Pd on the geometry, electronic properties, and active sites of copper clusters.

The geometry, electronic properties, and active sites of copper clusters doped with Ni or Pd atoms, Cu(n)()(-)(1)M (n = 2-6; M = Ni, Pd) have been investigated using first-principles methods. Planar structures are energetically favorable in Cu(n)()(-)(1)Ni (n = 2-6). However, for Pd-doped clusters, three-dimensional structures are competitive in energy, and for n = 6, the most stable structure is not planar. Several properties of doped copper clusters present odd-even oscillations as the number of copper atoms grow. The different atomic ground-state configuration of Ni and Pd determines the bonding and electronic properties of doped copper clusters. The interaction between impurities and copper atoms can modify the chemical hardness and active sites of doped copper clusters markedly inducing directionality in the reactivity. This effect is relevant to the behavior of catalysts as well as in the growth of metallic films.

Journal Article↗

PubMed2005

Microporous nanocomposites of Pd and Au nanoparticles via hierarchical self-assembly.

Microporous nanocomposites of Pd and Au nanoparticles were generated by utilizing electrostatic interaction between oppositely charged Au nanoparticles coated with carboxylate groups (Au-COO-) and spherical aggregates of Pd nanoparticles (Pd- NH3+) with a mean diameter of 80+/-20 nm stabilized and cross linked by octa(aminopropyl)silsesquioxane octahydrochloride (POSS-NH3+). Amide bonds were formed between the reactive ion couples that are well defined in the Pd-Au colloidal nanocomposites during a subsequent chemical reaction to generate more stable nanocomposites with improved chemical and physical properties.

Journal Article↗

PubMed2006

Electrochemical characterization of gold stepped surfaces modified with Pd.

Three different single crystals, Au(111), Au(332), and Au(331), were used as the substrate for palladium deposition in the underpotential deposition (UPD) regime. The Au(111) single crystal was used for control experiments to compare the behavior of the vicinal surfaces. Cyclic voltammetry in 0.1 M sulfuric acid solution, as well as electrochemical impedance spectroscopy (EIS) were used to study the hydrogen adsorption on the Pd thin films. Our results suggest that the voltammetric peaks at approximately 0.3 V versus the reversible hydrogen electrode (RHE) are related to the adsorption of hydrogen at large palladium terraces, and that at least two adjacent Pd rows are needed in order for the adsorption to take place. Further cycling to more positive potentials leads to the oxidation and slow dissolution of the Pd film. The behavior of the oxidation cycles is explained in terms of a higher stability of Pd at the steps.

Journal Article↗

PubMed2005

Size-dependence of surface plasmon resonance and oxidation for Pd nanocubes synthesized via a seed etching process.

Pd nanocubes between 8 and 50 nm in size were synthesized at the same concentration of Na2PdCl4 precursor by controlling the number of seeds formed in the nucleation stage. Increasing the concentration of FeCl3, an oxidative etchant for Pd, reduced the number of seeds and led to formation of larger Pd nanocubes. The larger nanocubes exhibited surface plasmon resonance peaks in the visible region, the locations of which matched with the results of the discrete dipole approximation calculation. While the nanocubes of 25 and 50 nm in size oxidized in air to form Pd@PdO core-shell structures, the 8-nm nanocubes were stable in air for over 90 days.

Crystallization↗

PubMed2005

Optical properties of Pd-Ag and Pt-Ag nanoboxes synthesized via galvanic replacement reactions.

Silver nanocubes dispersed in water were transformed into Pd-Ag or Pt-Ag nanoboxes by adding either Na(2)PdCl(4) or Na(2)PtCl(4). By controlling the amount of noble metal salt added, and therefore the molar ratio of Na(2)PdCl(4) or Na(2)PtCl(4) to Ag, we could tune the surface plasmon resonance peak of the nanostructures across the entire visible spectrum, from 440 to 730 nm. Replacement of Ag with Pd resulted in the formation of a nanobox composed of a Pd-Ag alloy single crystal, but the nanobox formed after replacement of Ag with Pt was instead composed of distinct Pt nanoparticles. DDA calculations suggest that both nanoboxes absorb light strongly, with Q(abs)/Q(sca) approximately 5. After galvanic replacement, Pd-Ag and Pt-Ag nanostructures remain SERS active, suggesting their use as a SERS probe for studying the dependence of interfacial chemistry on composition.

Journal Article↗

PubMed1994

Angiotensin II AT2 receptor stimulation extends the upper limit of cerebral blood flow autoregulation: agonist effects of CGP 42112 and PD 123319.

The effects of the angiotensin II AT2 receptor ligands CGP 42112 and PD 123319, the AT1 antagonist losartan, and the nonselective angiotensin II antagonist Sar1,Ile8-angiotensin II on the upper limit of CBF autoregulation were studied in pentobarbital-anesthetized rats. Blood pressure was increased by intravenous phenylephrine infusion, while CBF was measured continuously from the parietal cortex by laser-Doppler flowmetry. Intravenous infusions of CGP 42112 (0.1 and 1 mg kg-1 min-1) and PD 123319 (0.36 and 1 mg kg-1 min-1) shifted the upper limit of CBF autoregulation toward higher blood pressures without affecting baseline CBF. Sar1,Ile8-angiotensin II (4 micrograms kg-1 min-1) had no effect on baseline CBF or CBF autoregulation but antagonized the effect of CGP 42112 and PD 123319. Losartan (10 mg/kg i.v. bolus) reduced baseline blood pressure and CBF and shifted the autoregulation curve toward higher blood pressures. Sar1,Ile8-angiotensin II blocked the effect of losartan on baseline CBF but not on CBF autoregulation. These results suggest that both CGP 42112 and PD 123319 exert their effects on CBF autoregulation through stimulation of angiotensin II AT2 receptors. The mechanism by which losartan affects CBF remains unclear.

1-Sarcosine-8-Isoleucine Angiotensin II↗

PubMed2005

Oxidation of magnesia-supported Pd-clusters leads to the ultimate limit of epitaxy with a catalytic function.

Oxide-supported transition-metal clusters and nanoparticles have attracted significant attention owing to their important role as components of model catalysts, sensors, solar cells and magnetic recording devices. For small clusters, functionality and structure are closely interrelated. However, knowledge of the structure of the bare cluster is insufficient as the interaction with the chemical environment might cause drastic structural changes. Here we show by ab initio simulations based on the density functional theory that the reaction with molecular oxygen transforms small, non-crystalline, magnesia-supported Pd-clusters to crystalline Pd(x)O(y) nano-oxide clusters that are in epitaxy with the underlying support. Restructuring of the Pd backbone is controlled by the electrostatic interaction with magnesia leading to a strong reduction of the O2 dissociation barrier. The supported Pd(x)O(y) clusters are likely to serve as Mars-van Krevelen oxygen reservoirs in catalytic oxidation reactions as observed for PdO overlayers and demonstrated here for the oxidation of CO molecules.

Catalysis↗

PubMed2025

Cancer-induced nerve injury promotes resistance to anti-PD-1 therapy.

Perineural invasion (PNI) is a well-established factor of poor prognosis in multiple cancer types1, yet its mechanism remains unclear. Here we provide clinical and mechanistic insights into the role of PNI and cancer-induced nerve injury (CINI) in resistance to anti-PD-1 therapy. Our study demonstrates that PNI and CINI of tumour-associated nerves are associated with poor response to anti-PD-1 therapy among patients with cutaneous squamous cell carcinoma, melanoma and gastric cancer. Electron microscopy and electrical conduction analyses reveal that cancer cells degrade the nerve fibre myelin sheets. The injured neurons respond by autonomously initiating IL-6- and type I interferon-mediated inflammation to promote nerve healing and regeneration. As the tumour grows, the CINI burden increases, and its associated inflammation becomes chronic and skews the general immune tone within the tumour microenvironment into a suppressive and exhaustive state. The CINI-driven anti-PD-1 resistance can be reversed by targeting multiple steps in the CINI signalling process: denervating the tumour, conditional knockout of the transcription factor mediating the injury signal within neurons (Atf3), knockout of interferon-α receptor signalling (Ifnar1-/-) or by combining anti-PD-1 and anti-IL-6-receptor blockade. Our findings demonstrate the direct immunoregulatory roles of CINI and its therapeutic potential.

Animals↗

PubMed2007

A Bayesian population PK-PD model of ispinesib-induced myelosuppression.

The goal of the present analysis is to fit a Bayesian population pharmacokinetic pharmacodynomic (PK-PD) model to characterize the relationship between the concentration of ispinesib and changes in absolute neutrophil counts (ANC). Ispinesib, a kinesin spindle protein (KSP) inhibitor, blocks assembly of a functional mitotic spindle, leading to G2/M arrest. A first time in human, phase I open-label, non-randomized, dose-escalating study evaluated ispinesib at doses ranging from 1 to 21 mg/m(2). PK-PD data were collected from 45 patients with solid tumors. The pharmacokinetics of ispinesib were well characterized by a two-compartment model. A semimechanistic model was fit to the ANC. The PK and PD data were successfully modelled simultaneously. This is the first presentation of simultaneously fitting a PK-PD model to ANC using Bayesian methods. Bayesian methods allow for the use of prior information for some system-related parameters. The model may be used to examine different schedules, doses, and infusion times.

Adult↗

PubMed2003

Altered behavioral response to dopamine D3 receptor agonists 7-OH-DPAT and PD 128907 following repetitive amphetamine administration.

Behavioral sensitization, the progressive and enduring enhancement of certain behaviors following repetitive drug use, is mediated in part by dopaminergic pathways. Increased locomotor response to drug treatment, a sensitizable behavior, is modulated by an opposing balance of dopamine receptor subtypes, with D1/D2 dopamine receptor stimulation increasing and D3 dopamine receptor activation inhibiting amphetamine-induced locomotion. We hypothesize that tolerance of D3 receptor locomotor inhibition contributes to behavioral sensitization. In order to test the hypothesis that expression of behavioral sensitization results in part from release of D3 receptor-mediated inhibition, thereby resulting in decreased response to D3 receptor agonists, we examined the effect of repetitive amphetamine administration on the behavioral response to the D3 receptor preferring agonists 7-OH-DPAT and PD 128907. D3-selective effects have recently been described for both drugs at a low dose. At 1 week following completion of a repetitive treatment regimen, amphetamine-pretreated rats displayed a decreased response to D3-selective doses of both 7-OH-DPAT and PD 128907, when compared to animals receiving saline pretreatment. Moreover, in addition to the quantitative alteration in response, there was a change in the inter-relation between response to amphetamine and D3 agonist. A highly significant inverse relation between locomotor inhibitory response to PD 128907 and the locomotor-stimulant response to amphetamine was observed prior to amphetamine treatment. In contrast, 10 days following repetitive amphetamine treatment, the relation between response to PD 128907 and amphetamine was not detected. The observed behavioral alteration could not be accounted for by changes in D3 receptor binding in ventral striatum. These findings suggest a persistent release of D3 receptor-mediated inhibitory influence contributes to the expression of behavioral sensitization to amphetamine.

Amphetamine↗

PubMed2004

Synthesis, characterization, and stereochemistry of S-bridged Co(III)MCo(III)(M = Pd(II), Pt(II)) trinuclear complexes containing two non-bridging thiolato groups: building blocks for the construction of chiral heterometallic aggregates.

The reaction of fac(S)-[Co(aet)(3)](aet = aminoethanethiolate) with [PdCl(4)](2-) in a 2:1 ratio in water gave an S-bridged Co(III)Pd(II)Co(III) trinuclear complex composed of two mer(S)-[Co(aet)(3)] units, [Pd[Co(aet)(3)](2)](2+)([1](2+)). In [1](2+), each of the two mer(S)-[Co(aet)(3)] units is bound to a square-planar Pd(II) ion through two of three thiolato groups, leaving two non-bridging thiolato groups at the terminal. Of two geometrical forms, syn and anti, possible for [Pd[Co(aet)(3)](2)](2+), which arise from the difference in arrangement of two terminal non-bridging thiolato groups, [1](2+) afforded only the syn form. A similar reaction of fac(S)-[Co(aet)(3)] with [PtCl(4)](2-) or trans-[PtCl(2)(NH(3))(2)] produced an analogous Co(III)Pt(II)Co(III) trinuclear complex, [Pt[Co(aet)(3)](2)](2+)([2](2+)), but both the syn and anti forms were formed for [2](2+). Complexes [1](2+) and syn- and anti-[2](2+), which exclusively exist as a racemic(DeltaDelta/LambdaLambda) form, were successfully optically resolved with use of [Sb(2)(R,R-tartrato)(2)](2-) as the resolving agent. The reaction of syn-[2](2+) with [AuCl[S(CH(2)CH(2)OH)(2)]] led to the formation of an S-bridged Co(III)(4)Pt(II)(2)Au(I)(2) octanuclear metallacycle, [Au(2)[Pt[Co(aet)(3)](2)](2)](6+)([3](6+)), while the corresponding reaction of anti-[2](2+) afforded a different product ([[4](3+)](n)) that is assumed to have a polymeric structure in [[Au[Pt[Co(aet)(3)](2)]](3+)](n).

Journal Article↗

PubMed2005

Synthesis and characterization of novel Pd(II) complexes with chelating and non-chelating heterocyclic iminocarbene ligands.

The imidazolium salts [3-R1-1-{2-Ar-imino)-2-R2-ethyl}imidazolium] chloride (C-N; Ar = 2,6-iPr2C6H3; R1/R2 = Me/Me (a), Me/Ph (b), Ph/Me (c), 2,4,6-Me3C6H2 (d), 2,6-iPr2C6H3 (e)) react with Ag(2)O to give Ag(I) iminocarbene complexes (C-N)AgCl (4a-e) in which the iminocarbene ligand is bonded to Ag via the imidazoline-2-ylidene carbon atom. The solid-state structures of 4b and 4d were determined by X-ray crystallography and revealed the presence of monomeric (carbene)AgCl units with Z and E configurations at the imine C=N bonds, respectively. Carbene transfer to Pd occurs when compounds 4b-e are treated with (COD)PdCl2 to yield bis(carbene) complexes (C-N)2PdCl2 (6b-e) containing two kappa1-C bonded iminocarbene moieties. NMR spectroscopic data indicated a trans coordination geometry at Pd. This conclusion was supported by an X-ray structure determination of 6b which clearly demonstrated the non-chelating nature of the iminocarbene ligand system. EXSY 1H NMR spectroscopy suggests that the non-chelating structures undergo E/Z isomerization at the imine C[double bond, length as m-dash]N double bonds in solution. The preparative results contrast our earlier report that the reaction between 4a and (COD)PdCl2 results in a chelating kappa2-C,N bonded iminocarbene complex (C-N)PdCl2. The coordination mode and dynamic behavior of the iminocarbene ligand systems have been found to be dramatically affected by changes in the substitution pattern of the ligand system. Sterically unencumbered systems (a) favor the formation of kappa2-C,N chelate structures containing one iminocarbene moiety per metal upon coordination at Pd(II); these complexes were demonstrated to engage in reversible, solvent-mediated chelate ring-opening reactions. Sterically encumbered systems (b-e) form non-chelating kappa1-C iminocarbene Pd(II) complexes containing two iminocarbene ligands per metal. Transannular repulsions across the chelate ring are believed to be the origin of these structural differences.

Journal Article↗

PubMed2006

Synthesis and characterisation of benzyl phosphino-thioether and -thiolato Pd(II) complexes and their applications in Suzuki coupling reactions.

The synthesis of the benzyl phosphinothioether derivatives Ph(2)PCH(2)CH(Et)SR and their corresponding palladium complexes are reported, where R = CH(2)Ph, R = CH(2)-3,5-Me-C(6)H(3) and R = 1-CH(2)C(10)H(7)(5). Crystallographic data obtained for the complexes Pd(3)Cl(2) and Pd(4)Cl(2) show intra- and inter-molecular pi-pi interactions between the aromatic rings on the P and S substituents, and NOE experiments for Pd(4)Cl(2) show that these interactions persist in solution. The performance of the phosphinothioether palladium complexes in aryl-aryl cross-coupling reactions is compared with that of the corresponding complex of the parent phosphinothiolato ligand Ph(2)PCH(2)CH(Et)S(-)(1). High turnover numbers up to 2000000 are reported for the coupling of bromobenzene, using the palladium dimer [Pd(1)I](2) as the catalyst precursor. Kinetic studies show a linear dependence of the reaction on catalyst loading. The effect of other variables on the cross-coupling reaction, such as temperature, solvent and base, is also reported.

Journal Article↗

PubMed1997

Cardiovascular and renal effects of endothelin receptor blockade with PD 145065 and interaction with urodilatin.

Role of endogenous endothelins (ET) in the control of cardiovascular system and renal function, and ET interaction with urodilatin (URO) were studied in anaesthetized rats. Activity of ET was blocked using PD 145065 (5 mg kg-1 body wt i.v.) a non-selective antagonist of ETA and ETB receptors. PD 145065 decreased mean arterial blood pressure (MBP) from 114 +/- 4 to 109 +/- 4 mmHg and the renal blood flow (RBF) from 6.6 +/- 0.3 to 5.8 +/- 0.4 mL min-1 (P < 0.02) and increased renal vascular resistance (RVR) from 17.7 +/- 1.2 to 20.1 +/- 2.1 mmHg min mL-1. Heart rate (HR) and renal function were not affected. URO was infused i.v. at 0.1 nmol min-1 kg-1 body wt without or with previous ET receptor blockade. After pre-treatment with PD 145065, infusion of URO decreased MBP more than did URO alone: 15 +/- 3% vs. 7 +/- 2% (P < 0.05). RVR and HR did not change after URO alone but decreased with URO given to PD 145065 treated rats (19 +/- 5% and 14 +/- 3%, respectively, P < 0.01). It is concluded that in anaesthetized surgically prepared rats endogenous ET can cause renal vasodilation, in contrast to constriction of systemic vasculature. Enhancement by ET blockade of vascular systemic and renal effects of URO supports ET interaction with natriuretic peptides in the control of cardiovascular and renal function.

Animals↗

PubMed2001

Growth optimization of Pediococcus damnosus NCFB 1832 and the influence of pH and nutrients on the production of pediocin PD-1.

AIMS: Optimization of the growth of Pediococcus damnosus NCFB 1832 and the production of pediocin PD-1 by traditional fermentation methods. METHODS AND RESULTS: Fermentation studies were conducted in De Man Rogosa and Sharpe (MRS) broth (Oxoid), preadjusted to specific pH values, and in MRS broth supplemented with various nitrogen sources, MnSO4, MgSO4 and Tween 80. The production of pediocin PD-1 closely followed the growth curve of Ped. damnosus NCFB 1832. Maximum levels of bacteriocin activity (3249 AU ml(-1)/O.D.max) were recorded in MRS broth with an initial pH of 6.7. In media with an initial pH of 4.5 bacteriocin activity as low as 222 AU ml(-1)/O.D.max was recorded. The highest bacteriocin activity was recorded in growth conditions allowing the greatest pH variation (highest DeltapH). The addition of bacteriological peptone (1.7%, w/v), MnSO4 (0.014%, w/v) and Tween 80 (3%, v/v) to MRS and adjustment of the medium pH to 6.7 resulted in a further increase in activity (from 3249 to 5078 AU ml(-1)/O.D.max). The same medium, but with an initial pH of 6.2, resulted in an 82.5% decrease in bacteriocin activity. CONCLUSIONS: Pediocin PD-1 production is not only stimulated by the presence of specific growth factors (e.g., bacteriological peptone, MnSO4 or Tween 80), but may also be stimulated by the lowering in pH during growth (highest DeltapH), and thus also the amount of organic acids produced. SIGNIFICANCE AND IMPACT OF THE STUDY: The production of pediocin PD-1 by the wild-type producer strain was significantly improved by using a defined medium and traditional fermentation methods.

Anti-Bacterial Agents↗

PubMed2003

Association of a putative regulatory polymorphism in the PD-1 gene with susceptibility to type 1 diabetes.

The immunoreceptor programmed cell death-1 (PD-1) is reported to play an important role in the regulation of peripheral tolerance in rodents, and it was recently shown that a polymorphism in a regulatory site of the PD-1 gene is associated with susceptibility to the autoimmune disease systemic lupus erythematosus (SLE) in humans. We investigated the existence of single-nucleotide polymorphisms (SNPs) in the PD-1 gene in patients with type 1 diabetes in comparison with healthy control subjects, by analyzing 94 children and adolescents with type 1 diabetes diagnosed before their eighteenth birthday (male : female = 52 : 42) and 155 control subjects. Polymorphisms in the complete PD-1 gene (minus the large intron 1) were detected by sequencing. In total, we identified 14 SNPs, of which six have been previously described, including an intronic 7146G/A SNP. We found this polymorphism to be associated with the development of type 1 diabetes [found in 12.2% of diabetic individuals vs 6.8% in controls; odds ratio (OR) = 1.92]. The associated allele is previously shown to alter a transcription factor-binding site (RUNX1/AML1), and the results of this study suggest that this allele could act as an additional susceptibility allele to type 1 diabetes.

Adolescent↗

PubMed2001

Achilles tendon (TA) size and power Doppler ultrasound (PD) changes compared to MRI: a preliminary observational study.

AIM: To assess whether abnormal Achilles tendon (TA) magnetic resonance imaging (MRI) and spectral ultrasound (US) features have associated development of microvascular power Doppler (PD) flow. MATERIALS AND METHODS: In a prospective, controlled and blinded study six patients with TA symptoms were compared to five with other ankle abnormalities. Two radiologists independently measured the mean maximal anteroposterior diameter on MRI and conventional US (categorized as normal <6 mm, mild 6.1-10 mm, moderate 1.1-1.5 cm and severely enlarged > 1.6 cm), assessed morphology and studied the vessels using power Doppler. They formed a consensus over discrepancies. Sonography of the contralateral side within 24 h was used as a control. RESULTS: Twenty-one tendons in six women and five men, aged 45-77 years (mean 57.6 years), were examined, 12 tendons were of normal US morphology and size (< 6 mm), and did not exhibit PD's flow (interobserver agreement K > 0.74). Of the 12 tendons studied by MRI five were normal, seven tendons were enlarged, five of which had a proportionate increase in PD flow at the margin on the deep surface and four also had vessels in the centre of the tendon. All five of these tendons had high signal on T2-weighting (T2W). Of the two mildly enlarged tendons of intermediate signal on T1 and T2W, one showed PD flow and the other did not. CONCLUSIONS: In patients with TA disease power Doppler ultrasound shows proliferation of vessels in enlarged, abnormal tendons demonstrated on MRI and standard ultrasound, in the absence of definite tears.

Achilles Tendon↗

PubMed2002

Altered methylation pattern of the G6 PD promoter in Rett syndrome.

Rett syndrome (RTT) is a neurodevelopmental disorder that almost exclusively affects girls. Recently mutations in MECP2, that encodes the methyl CpG binding protein 2 (MeCP2), have been found to cause RTT. MeCP2 has a role in gene silencing. It binds to methylated cytosine in the DNA and recruits histone deacetylases. We studied the methylation pattern of the promoters of two X chromosomal genes, G6 PD and SYBL1, in patients with RTT and in a control group. Both genes undergo X inactivation which correlates with promoter methylation. A 1 : 1 ratio of methylated versus non-methylated alleles was expected. In the control group a median ratio of 47 : 53 of methylated to non-methylated alleles was found at the G6 PD promoter locus. In 22 patients with RTT the median ratio was significantly different, 33 : 67 (p < 0.0001). Analysis of the SYBL1 promoter revealed an almost identical median ratio of methylated versus non-methylated alleles (RTT 47 : 53; control 49 : 51), however, the range was wider in the RTT group (RTT 23 : 77 to 56 : 44; control 43 : 57 to 55 : 45). There was no apparent correlation between G6 PD promoter methylation status and mutations in the MeCP2 gene or the severity of the clinical phenotype in our patient group. The finding of reduced methylation at the G6 PD promoter is an interesting finding and suggests that there could be widespread dysregulation of X chromosomal genes in Rett syndrome.

Chromosomal Proteins, Non-Histone↗