Ultrafast relaxation of photoexcited superfluid He nanodroplets.

The relaxation of photoexcited nanosystems is a fundamental process of light-matter interaction. Depending on the couplings of the internal degrees of freedom, relaxation can be ultrafast, converting electronic energy in a few fs, or slow, if the energy is trapped in a metastable state that decouples from its environment. Here, we study helium nanodroplets excited resonantly by femtosecond extreme-ultraviolet (XUV) pulses from a seeded free-electron laser. Despite their superfluid nature, we find that helium nanodroplets in the lowest electronically excited states undergo ultrafast relaxation. By comparing experimental photoelectron spectra with time-dependent density functional theory simulations, we unravel the full relaxation pathway: Following an ultrafast interband transition, a void nanometer-sized bubble forms around the localized excitation (He[Formula: see text]) within 1 ps. Subsequently, the bubble collapses and releases metastable He[Formula: see text] at the droplet surface. This study highlights the high level of detail achievable in probing the photodynamics of nanosystems using tunable XUV pulses.

Overexpression of TFAP2C in invasive breast cancer correlates with a poorer response to anti-hormone therapy and reduced patient survival.

The AP-2gamma transcription factor encoded by the TFAP2C gene is a member of a family of homologous DNA binding proteins that play essential roles during vertebrate embryogenesis but show a restricted pattern of expression in the adult. Elevated expression of the AP-2alpha and AP-2gamma family members has been associated with a number of neoplasms, particularly breast cancer. Here we present an exploratory immunohistochemical study of an archival primary breast tumour series (n = 75) with parallel clinicopathological data using a new, well-characterized antibody to AP-2gamma. Heterogeneous, exclusively nuclear expression of AP-2gamma was found in the epithelial and myoepithelial compartments of normal breast and within tumour epithelial cells. In the breast cancer series, the most notable association was a correlation between elevated levels of AP-2gamma and shortened patient survival (p = 0.0009*). This relationship was also conserved in ER-positive and ErbB2-negative patients; sub-groups generally considered to have a relatively good prognosis. When patient data for survival and duration of treatment response on anti-hormone therapy were examined by multivariate analysis, AP-2gamma was revealed in this study to be an independent predictor of outcome for both survival (p = 0.005) and response to anti-hormone therapy (p = 0.046). Studies using in vitro models confirmed that while tamoxifen response is associated with lower levels of AP-2gamma, acquisition of resistance to this and other anti-hormone measures (eg faslodex or oestrogen deprivation) is associated with high levels of nuclear AP-2gamma. Together these data suggest that elevated tumour AP-2gamma expression can contribute to the failure of cells to growth arrest following anti-hormone treatment and lead to sustained growth and poorer patient outcome.

Application of mean-field and surface-hopping approaches for interrogation of the Xe3+ molecular ion photoexcitation dynamics.

The dissociation dynamics of the excited Xe(3) (+) molecular ion through the Pi(12)(u) and Pi(12)(g) conical intersection was interrogated by computational simulation in which no adjustable parameters were used. The electronic ground and excited state potential energy surfaces were generated by the diatomics-in-molecules method, and the Ehrenfest mean-field and Tully surface-hopping approaches treated the nonadiabatic interactions. Reproduction of the experimental spectrum of the symmetric photofragmentation as a function of excitation energy was obtained within the region of interest (2.5-3.75 eV), with the exception of a 0.25 eV width on the red side of the spectral apex. Good agreement was obtained with the experimental dissociated photofragment kinetic energy spectra. It was determined that the greatest contribution to the nonadiabatic coupling between the two states originated from the bending vibrational mode of the molecule in the Sigma(12)(u), ground electronic state before excitation.

Cholestasis protects the liver from ischaemic injury and post-ischaemic inflammation in the mouse.

BACKGROUND AND HYPOTHESIS: Cholestasis is associated with high morbidity and mortality in patients undergoing major liver surgery, but the mechanisms responsible remain elusive. Increased ischaemic liver injury and inflammation may contribute to the poor outcome. METHODS: Common bile duct ligation (biliary obstruction with hyperbilirubinaemia) or selective ligation of the left hepatic duct (biliary obstruction without hyperbilirubinaemia) was performed in C57BL/6 mice before 1 h of hepatic ischaemia and 1, 4 or 24 h of reperfusion. Infection with the intracellular hepatic pathogen Listeria monocytogenes for 12 and 48 h was used to study ischaemia-independent hepatic inflammation. RESULTS: Cholestatic mice showed considerable protection from ischaemic liver injury as determined by transaminase release, histological liver injury and neutrophil infiltration. In cholestatic mice, reduced injury correlated with a failure to activate nuclear factor kappaB (NFkappaB) and tumour necrosis factor alpha (TNFalpha) mRNA synthesis, two key mediators of post-ischaemic liver inflammation. After selective bile duct ligation, both the ligated and the non-ligated lobes showed blocked activation of NFkappaB as well as reduced induction of TNFalpha mRNA synthesis and neutrophil infiltration. By contrast, infection with L monocytogenes showed comparable activation of NFkappaB and hepatic recruitment of neutrophils 12 h after infection. CONCLUSION: Cholestasis does not increase but rather dramatically protects the liver from ischaemic injury and inflammation. This effect is mediated by a systemic factor, but not bilirubin, and is associated with a preserved capacity to trigger an inflammatory response to other stimuli such as a bacterial pathogen.

Effects of static and dynamic perturbations on isotropic hyperfine coupling constants in some quinone radicals.

The effects of solvent dielectric response on the isotropic hyperfine coupling constants of the 1,4-benzoquinone, 1,4-naphthoquinone and 9,10-anthraquinone anions and 1,4-naphthalenediol cation radicals were studied by electron spin resonance (ESR) spectroscopy and by the theoretical density functional method within the polarizable continuum model. Experimental results demonstrate that the isotropic hyperfine coupling constants can be obtained with high accuracy and that the effects of solvent impurities can be minimized by careful sample preparation. The results obtained correlate well with theoretical predictions from density functional theory calculations. For 1,4-naphthalenediol both the solvent dielectric response as well as rotational averaging of the hydroxy groups were calculated. The overall results highlight the importance of static and dynamic perturbations to the couplings and aid in the assignation process of the couplings to specific magnetic nuclei.

Cardiac malformations, adrenal agenesis, neural crest defects and exencephaly in mice lacking Cited2, a new Tfap2 co-activator.

The protein EP300 and its paralog CREBBP (CREB-binding protein) are ubiquitously expressed transcriptional co-activators and histone acetyl transferases. The gene EP300 is essential for normal cardiac and neural development, whereas CREBBP is essential for neurulation, hematopoietic differentiation, angiogenesis and skeletal and cardiac development. Mutations in CREBBP cause Rubinstein-Taybi syndrome, which is characterized by mental retardation, skeletal abnormalities and congenital cardiac defects. The CBP/p300-interacting transactivator with ED-rich tail 2 (CITED2) binds EP300 and CREBBP with high affinity and regulates gene transcription. Here we show that Cited2-/- embryos die with cardiac malformations, adrenal agenesis, abnormal cranial ganglia and exencephaly. The cardiac defects include atrial and ventricular septal defects, overriding aorta, double-outlet right ventricle, persistent truncus arteriosus and right-sided aortic arches. We find increased apoptosis in the midbrain region and a marked reduction in ErbB3-expressing neural crest cells in mid-embryogenesis. We show that CITED2 interacts with and co-activates all isoforms of transcription factor AP-2 (TFAP2). Transactivation by TFAP2 isoforms is defective in Cited2-/- embryonic fibroblasts and is rescued by ectopically expressed CITED2. As certain Tfap2 isoforms are essential in neural crest, neural tube and cardiac development, we propose that abnormal embryogenesis in mice lacking Cited2 results, at least in part, from its role as a Tfap2 co-activator.

Effect of ischaemic preconditioning, cardiopulmonary bypass and myocardial ischaemic/reperfusion on free radical generation in CABG patients.

OBJECTIVE: To investigate the free radicals (FR) generation after ischaemic preconditioning and cardiopulmonary bypass and during reperfusion in CABG patients, and the role of ischaemic preconditioning. METHODS: Forty-three CABG patients were randomised into an ischaemic preconditioning and a control group. The protocol for ischaemic preconditioning was two cycles of 2-min ischaemia followed by 3-min reperfusion. Free radicals were measured using electron spin resonance spectroscopy. Global and right heart functions were collected. RESULTS: The free radicals generation in coronary sinus blood in the ischaemic preconditioning group was 9.7 and 16.6% after the ischaemic preconditioning protocol and 10 min after declamping, 6.8 and 13.3% in the controls. The free radicals in arterial samples were, respectively, 21, 14, 10 and 9% at 10 min, 1, 2 and 24 h after reperfusion. Cardiac index (CI) and right ventricular ejection fraction (RVEF) were improved by ischaemic preconditioning. CONCLUSION: Both ischaemic preconditioning and cardiopulmonary bypass induced free radicals generation. Although ischaemic preconditioning had no effect on free radicals generation after the operation, it protected against postoperative stunning.

Effect of ischemic preconditioning on myocardial protection in coronary artery bypass graft patients : can the free radicals act as a trigger for ischemic preconditioning?

OBJECTIVE: To investigate the interrelationship of free radicals (FRs), ischemic preconditioning (IP), and hemodynamic function in coronary artery bypass graft (CABG) patients. DESIGN: Prospective, randomized, and controlled clinical study. PATIENTS: Forty CABG patients were randomized into an IP group (n = 20) and a control group (n = 20). INTERVENTION: The IP group was preconditioned with two cycles of two-min ischemia followed by 3-min reperfusion before cross-clamping. MEASUREMENT AND RESULTS: FR content in coronary sinus blood was measured directly using alpha-phenyl-N-tert-butylnitrone-electron spin-trapped spectroscopy. A small amount of FRs was generated after the IP protocol (5.6% above the baseline) but not in control subjects. A larger amount was generated 10 min after declamping in both groups (8.4% in IP protocol and 7.7% in control subjects). Hemodynamic function recovered better in the IP group at 1 h and 6 h after declamping. There was a significant negative correlation between FR generation after declamping and left ventricular stroke work index (LVSWI) at 1 h and 6 h after declamping (r = -0.71 and - 0.59, respectively) in the control subjects but not in the IP group. There was a significant positive correlation between FR generation after the IP protocol and cardiac index at 1 h and 6 h (r = 0.50 and 0.61, respectively) and LVSWI at 1 h and 6 h (r = 0.56 and 0.54, respectively) after declamping in the IP group but not in the control subjects. CONCLUSION: FR generation after the operation correlates with ventricular functional depression in CABG patients. IP protects the stunning heart but does not alter FR generation. The association of better hemodynamic recovery after CABG with FR generation during the IP period suggests that FRs might act as one of the triggers for IP.

Archaeal RNA polymerase subunits F and P are bona fide homologs of eukaryotic RPB4 and RPB12.

The archaeal and eukaryotic evolutionary domains diverged from each other approximately 2 billion years ago, but many of the core components of their transcriptional and translational machineries still display a readily recognizable degree of similarity in their primary structures. The F and P subunits present in archaeal RNA polymerases were only recently identified in a purified archaeal RNA polymerase preparation and, on the basis of localized sequence homologies, tentatively identified as archaeal versions of the eukaryotic RPB4 and RPB12 RNA polymerase subunits, respectively. We prepared recombinant versions of the F and P subunits from Methanococcus jannaschii and used them in in vitro and in vivo protein interaction assays to demonstrate that they interact with other archaeal subunits in a manner predicted from their eukaryotic counterparts. The overall structural conservation of the M. jannaschii F subunit, although not readily recognizable on the primary amino acid sequence level, is sufficiently high to allow the formation of an archaeal-human F-RPB7 hybrid complex.

Effect of allopurinol on myocardial oxygen free radical production in coronary bypass surgery.

OBJECTIVES: Allopurinol protects the heart from reperfusion injury. The aim of this study was to investigate myocardial free radical production during reperfusion with and without allopurinol treatment in coronary artery bypass grafting patients randomized into allopurinol (n = 14) or placebo (n = 13) groups. DESIGN: Allopurinol (1 g) was given blind prior to cardiopulmonary bypass and prior to opening the aorta. Oxygen free radicals were measured before anesthesia in arterial blood, before cross-clamping and 1 and 10 min after reperfusion in arterial and coronary sinus blood. Levels were measured as relative concentrations by the electron spin resonance method. RESULTS: One minute after reperfusion the level of spin-trapped radicals in arterial blood was elevated significantly (p = 0.016) in the allopurinol group, from 7.7 (SE: 0.8) to 8.6 (1.4) and non-significantly (p = 0.074) in the placebo group, from 7.3 (0.7) to 8.3 (0.8). Ten minutes after reperfusion the arterial values were 8.6 (1.5) in the allopurinol and 7.6 (0.7) in the placebo group, the sinus values being 7.6 (1.3) and 8.3 (0.8), respectively. Myocardial free radical production was -0.94 (1.21) in the allopurinol and +0.79 (0.96) in the placebo group after 10 min reperfusion, the difference being significant (p = 0.043). CONCLUSIONS: All patients in both groups had an increasing tendency to free radical production during early reperfusion. Patients treated with allopurinol showed less myocardial production of free radicals, indicating that its protective effect may be due to its antioxidative properties.

The Drosophila homologue of the 64 kDa subunit of cleavage stimulation factor interacts with the 77 kDa subunit encoded by the suppressor of forked gene.

During mRNA 3' end formation, cleavage stimulation factor (CstF) binds to a GU-rich sequence downstream from the polyadenylation site and helps to stabilise the binding of cleavage-polyadenylation specificity factor (CPSF) to the upstream poly-adenylation sequence (AAUAAA). The 64 kDa subunit of CstF (CstF-64) contains an RNA binding domain and is responsible for the RNA binding activity of CstF. It interacts with CstF-77, which in turn interacts with CPSF. The Drosophila suppressor of forked gene encodes a homologue of CstF-77, and mutations in it affect mRNA 3' end formation in vivo. A Drosophila homologue for CstF-64 has now been isolated, both through homology with the human protein and through protein-protein interaction in yeast with the suppressor of forked gene product. Alignment of CstF-64 homologues shows that the proteins have a conserved N-terminal 200 amino acids, the first half of which is the RNA binding domain with the second half likely to contain the CstF-77 interaction domain; a central region variable in length and rich in glycine, proline and glutamine residues and containing an unusual degenerate repeat motif; and then a conserved C-terminal 50 amino acids. In Drosophila, the CstF-64 gene has a single 63 bp intron, is transcribed throughout development and probably corresponds to l(3)91Cd.

Crystallization and preliminary diffraction studies of the RNA polymerase subunit RPB5 from Saccharomyces cerevisiae.

Crystals of the RNA polymerase subunit RPB5 from Saccharomyces cerevisiae have been obtained by vapour-diffusion techniques. The protein has been overexpressed in bacterial cells as a fusion with glutathione S-transferase. Two monoclinic crystal forms can be grown under different sets of conditions. In both cases, the diffraction is consistent with space group P21, with unit-cell parameters a = 45. 3, b = 135.3, c = 47.3 A, beta = 118.6 degrees for crystal form I and a = 48.4, b = 137.1, c = 47.1 A, beta = 118.6 degrees for crystal form II.

RNA polymerase subunit H features a beta-ribbon motif within a novel fold that is present in archaea and eukaryotes.

The archaeal H and eukaryotic RPB5 RNA polymerase subunits are highly homologous and are likely to play a fundamental role in transcription that extends from archaea to humans. We report the structure of subunit H, in solution, from the archaeon Methanococcus jannaschii using multidimensional nuclear magnetic resonance. The structure reveals a novel fold containing a four-stranded mixed beta sheet that is flanked on one side by three short helices. The dominant feature is beta-ribbon motif, which presents a hydrophobic, basic surface, and defines a general RNA polymerase architectural scaffold.

In vitro assembly of an archaeal D-L-N RNA polymerase subunit complex reveals a eukaryote-like structural arrangement.

Archaeal RNA polymerases (RNAPs) resemble the eukaryotic nuclear RNAPs in complexity, and many of their subunits display a high degree of sequence similarity to their eukaryotic counterparts. Here we describe specific protein-protein contacts present between individual recombinant RNAP subunits from the archaeon Methanococcus jannaschii. Subunits D and L interact specifically with each other in two-hybrid assays. D also interacts under the same conditions with the RPB11 and AC19 subunits from the yeast Saccharomyces cerevisiae, suggesting that essential elements of the binding surface between these proteins have been conserved across the archaeal/eukaryotic evolutionary domain boundary. Interactions between L and RPB3 or AC40 were, however, not detectable. Recombinant D and L subunits associate under in vitro conditions and copurify with each other during size-exclusion chromatography. Addition of an another recombinant subunit (N) to the D-L complex results in the formation of a triple complex. This D-L-N complex resembles the RPB3-RPB11-RPB10 or AC40-AC19-RPB10 complexes in eukaryotic RNAPIIand RNAPI/RNAPIII, respectively. Our data provide evidence for a close similarity in the quaternary arrangement of a subset of archaeal and eukaryotic RNA polymerase subunits and the conservation of the protein-protein contacts formed between them.

Thermodynamics of complexation of magnesium and calcium ions with dichloromethylenediphosphonate.

Thermodynamic parameters for the complexation of CA(2+) and Mg(2+) ions by dichloromethylenediphosphonate (clodronate) ligand were obtained by potentiometric and calorimetric techniques. The measurements were conducted at an ionic strength of 0.10M [(CH(3))(4)NCl]) and at 25 degrees C. The potentiometric data were consistent with a model involving the presence of ML(2-)MHL(-) and M(2)L species (L = tetranegative clodronate anion). The enthalpies of formation of the ML(2-) and MHL(-) complexes were obtained from calorimetric data. Attempts to determine the enthalpies of formation of the M(2)L species were unsuccessful due to the limited solubilities of these species.

A solution hybridization method for quantification of mRNAs: determining the amount and stability of oncogene mRNA.

A solution hybridization method for the quantification of specific mRNAs is described. This assay utilizes complementary RNA probes prepared by in vitro transcription, sandwich hybridization in solution, and affinity-based hybrid collection. The possibility of using this method for crude biological samples without purifying mRNAs makes it ideal when accurate quantification of multiple samples is needed. Human N-myc oncogene transcript was used as a model and as little as 0.24 pg (2 X 10(5) molecules) of N-myc mRNA could be detected. Using this assay it was shown that human neuroblastoma IMR-32 cells contain approximately 500 N-myc mRNA molecules per cell having a half-life of approximately 35 min.