Acetal photocatalytic formation from ethanol in the presence of TiO2 rutile and anatase.

The decomposition of ethanol, one of the most important biomass platform molecules, was investigated under green conditions, ambient temperature, atmospheric pressure and air for the synthesis of acetal in the presence of TiO2 activated under UV-A radiation. The impact of ethanol concentration, of the nature of TiO2 (rutile, anatase or mixture), of the photo-deposition of Pt under air or argon were all factors under investigation. Whatever the conditions and the nature of catalyst used, acetaldehyde was initially formed before reacting with ethanol to form acetal, a promising fuel additive. However, the subsequent generation of acetal differs depending on the conditions and the nature of catalyst. In the absence of a noble metal, rutile TiO2 leads to an increase in acetal formation at equivalent acetaldehyde formation. This behavior is discussed considering the acidic and basic properties of rutile and anatase phases together with H+ generated under UV. In the presence of Pt, under air or Ar, the acetal formation begins at a lower concentration of acetaldehyde due to the in-situ photo-deposition of Pt. However, whereas acetal formation is similar for Pt/anatase and Pt/rutile phase under air, under Ar, less acetal is generated on Pt/rutile in agreement with the production of more H2.

A nucleic acid triple helix formed by a peptide nucleic acid-DNA complex.

The crystal structure of a nucleic acid triplex reveals a helix, designated P-form, that differs from previously reported nucleic acid structures. The triplex consists of one polypurine DNA strand complexed to a polypyrimidine hairpin peptide nucleic acid (PNA) and was successfully designed to promote Watson-Crick and Hoogsteen base pairing. The P-form helix is underwound, with a base tilt similar to B-form DNA. The bases are displaced from the helix axis even more than in A-form DNA. Hydrogen bonds between the DNA backbone and the Hoogsteen PNA backbone explain the observation that polypyrimidine PNA sequences form highly stable 2:1 PNA-DNA complexes. This structure expands the number of known stable helical forms that nucleic acids can adopt.

Development of a Children's Trust in General Physicians Scale.

BACKGROUND: Researchers have developed scales assessing adults' trust beliefs in physicians and found that those are associated with measures of health behaviour and physical health. The purpose of the research was to develop a Children's Trust in General Physicians Scale (CTGPS) and examine its relation to health behaviour: adherence to medical regimes. METHODS: The participants were 128 children (68 girls and 60 boys) in Study 1 and 198 children (105 girls and 93 boys) in Study 2 who attended years 5 and 6 of elementary school in UK (mean ages = 10 years and 10 months and 10 years and 7 months respectively). The children completed the nine-item CTGPS and reported their trust in doctors and (in Study 2) adherence to medical regimes. Parents also reported those behaviours. RESULTS: Principal components analysis and confirmatory factor analysis of the CTGPS yielded the expected three factors: Honesty, Emotional and Reliability. The CTGPS had acceptable internal consistency and, as evidence for its validity, was associated with reported trust in doctors. The results from Study 2 confirmed that the CTGPS was associated with adherence to medical regimes. CONCLUSION: A CTGPS was developed that is associated with adherence to medical regimes.

Cytidine deaminase. The 2.3 A crystal structure of an enzyme: transition-state analog complex.

We have solved the structure of Escherichia coli cytidine deaminase (CDA) complexed to the transition state analog, 5-fluoroprimidin-2-one riboside. The monomer of the alpha 2 CDA dimer is composed of a small N-terminal alpha-helical domain with no obvious connection to the active sites, and two, larger, core domains. The two core domains have nearly identical tertiary structures and are related by approximate 2-fold symmetry, but lack internal amino acid sequence homology. Comparison of the core domain structure with known structures by sequence homology and structural compatibility searches suggests that the CDA tertiary structure cannot be superimposed on any known protein structure. The two active sites per dimer are formed across the subunit interface. The N-terminal core domain provides a pyrimidine nucleoside and zinc-binding pocket and the structurally homologous C-terminal core domain in the other monomer covers this active-site cleft, completely sequestering the ligand from solvent. The deeply buried zinc-binding site is formed by a novel "topological switch point" at the amino termini of two alpha-helices in consecutive alpha-beta-alpha-beta segments. The transition state analog is bound as a covalent hydrate at C4. The inhibitor hydroxyl oxygen atom interacts both with the zinc atom and the Glu104 carboxylate group, affording high differential affinity for the hydroxyl group relative to a hydrogen atom, in a manner reminiscent of that observed in adenosine deaminase (ADA). Unlike the latter enzyme, the zinc atom is coordinated in a tetrahedral ligand field to two cysteine and one histidine ligands, plus the hydroxyl group. Moreover, the inhibitor stereochemistry is of the opposite hand from that of the corresponding ADA inhibitor at C4(R), but is the same at the hydroxyl group O4(S). A consequence of these stereochemical differences is that in CDA a single conserved carboxylate side-chain, Glu104, can provide all of the necessary proton transfer functions involved in generating the zinc hydroxide nucleophile, and protonating the pyrimidine ring nitrogen atom and leaving amino group. The differences in zinc ligands, ligand-binding stereochemistry, and tertiary structures of CDA and ADA strongly suggest that the common features of transition state stabilization arose by convergent evolution.

Electrophysiological effects of endothelin-1 and their relationship to contraction in rat renal arterial smooth muscle.

The electophysiological effects of endothelin-1 (ET-1) and their relationship to contraction remain unclear in the renal circulation. Using endotheliumdenuded arteries from the main branch of the renal artery proximal to the kidney of the rat, we have examined its effects on tension and conducted parallel patch-clamp measurements using freshly isolated smooth muscle cells from this tissue. Pharmacological experiments revealed that ET-1 produced constriction of renal arteries dependent on the influx of extracellular Ca(2+), mediated solely through ET(A) receptor stimulation. Current-clamp experiments revealed that renal arterial myocytes had a resting membrane potential of approximately 32 mV, with the majority of cells exhibiting spontaneous transient hyperpolarizations (STHPs). Application of ET-1 produced depolarization and in those cells exhibiting STHPs, either caused their inhibition or made them occur regularly. Under voltage-clamp conditions cells were observed to exhibit spontaneous transient outward currents (STOCs) inhibited by iberiotoxin. Application of voltage-ramps revealed an outward current activated at approximately -30 mV, sensitive to both 4-AP and TEA. Taken together these results suggest that renal arterial myocytes possess both delayed rectifying K(+) (K(V)) and Ca(2+)-activated K(+) (BK(Ca)) channels. Under voltage-clamp, ET-1 attenuated the outward current and reduced the magnitude and incidence of STOCs: effects mediated solely as a consequence of ET(A) receptor stimulation. Thus, in conclusion, activation of ET(A) receptors by ET-1 causes inhibition of K(V) and BK(Ca) channel activity, which could promote and/or maintain membrane depolarization. This effect is likely to favour L-type Ca(2+) channel activity providing an influx pathway for extracellular Ca(2+) essential for contraction.

Navy Asbestos Medical Surveillance Program, 1995-1999: demographic characteristics and smoking status.

A descriptive study of the Navy Asbestos Medical Surveillance Program is presented from data provided by the Navy Environmental Health Center in Norfolk, Virginia, with an emphasis on demographic characteristics and smoking. Analysis of 79,598 physical examinations for the period 1995 to 1999 revealed that Navy and Marine Corps civil service employees constituted 90% and Navy active duty personnel constituted 9%. Most personnel reported "no current exposure, have prior exposure" to asbestos (Navy active duty, 77%; civil service employees, 61%). Current smoking rates per year decreased for Navy active duty (from 34.6% to 28.7%) and civil service workers (from 26.0% to 21.6%), both reductions being significant for trend. Logistic regression for current smoking showed higher rates for Navy active duty and those with "direct" asbestos exposure, whereas those 50 years or older and of Asian ethnicity had lower smoking rates. These findings provide programmatic insights for the Asbestos Medical Surveillance Program and suggest areas for further study.

House dust mites in naval ships, military barracks, and homes in the Hampton Roads area of Virginia.

This survey was undertaken to determine the possible exposure of military personnel to house dust mites in ships, barracks, and homes in the Hampton Roads area of Virginia. During the period from April 1, 1982 through August 31, 1983, 524 dust samples were collected with vacuum cleaners. Mites were extracted from aliquots of dust, counted, and identified as to species and life stage. Dermatophagoides pterynssinus (European house dust mite) was more common in private homes, while Dermatophagoides farinae (North American house dust mite) was more common on ships. Berthing compartments had the highest density of mites of areas sampled aboard ships. There appears to be a trend between the density of personnel and mites. Ships had a smaller percentage of mite-infested samples than houses.

Analysis of the role of the Shine-Dalgarno sequence and mRNA secondary structure on the efficiency of translational initiation in the Euglena gracilis chloroplast atpH mRNA.

Chloroplast mRNAs in Euglena gracilis fall into two classes. One class has a Shine-Dalgarno sequence 5' to the AUG start codon while the other group of mRNAs does not have any conserved sequence elements near the start codon. The chloroplast mRNA encoding the atpH gene has been selected as an example of a message which has a Shine-Dalgarno sequence (GGAGUU) located in the initiation region. Mutations in the Shine-Dalgarno sequence result in 2-5-fold reductions in the efficiency of the message in initiation complex formation depending on the precise mutation. Secondary structure mapping of the initiation region of the atpH mRNA suggests that a number of mRNA conformations are present in an equilibrium mixture. Mutations in the Shine-Dalgarno sequence had little effect on the overall structure of the mRNA. Directed mutations which place the Shine-Dalgarno sequence into a region of higher secondary structure drastically reduce the activity of the message. The monocistronic form of the atpH mRNA has a 5'-untranslated leader region slightly over 70 nucleotides in length. Deletions in the leader suggest that a minimum length of 10 bases 5' to the start codon is important for activity in initiation. The presence of the full leader increased efficiency in initiation about 2-fold compared to messages with leaders 25-40 residues in length.

Incomplete factorial search for conditions leading to high quality crystals of Escherichia coli cytidine deaminase complexed to a transition state analog inhibitor.

We have used an incomplete factorial design (Carter, C. W., and Carter, C. W., Jr. (1979) J. Biol. Chem. 254, 12219-12223) to find conditions for growing high quality crystals of Escherichia coli cytidine deaminase (EC 3.5.4.5). Crystals grow at pH 6.0 in hanging or sitting drops with either 1.6 M ammonium sulfate or 2.4-2.5 M sodium phosphate as precipitant. Both conditions produce crystals with identical morphologies and unit cell constants. The space group is P3(1)21 (or its enantiomorph P3(2)21), and the unit cell constants are a = b = 120.3 A, c = 78.4 A. The asymmetric unit is most reasonably one dimer of 66,000 Mr. The crystal size is very dependent on the supersaturation ratio, S = [initial protein concentration]/[equilibrium protein concentration], exhibiting a maximum at S = 7.7. The largest crystals diffract to at least 2.5 A and have a lifetime of 4 to 5 days in the x-ray beam at room temperature. The enzyme in these crystals is complexed with the transition state analog inhibitor 1-(beta-D-ribofuranosyl)-5-fluoropyrimidin-2-one (5-fluoropyrimidin-2-one riboside). We have collected data from parent crystals and from a heavy atom derivative in which the transition state analog is replaced by the active site directed inhibitor 5-(chloromercuri)cytidine.

Two-step purification of tryptophan-accepting tRNA from Bacillus stearothermophilus.

Tryptophan-accepting tRNA has been purified essentially to homogeneity from Bacillus stearothermophilus. Crude tRNA was chromatographed first on benzoylated DEAE-cellulose and then on Sepharose 4B with reverse salt gradient elution. The product has tryptophan acceptor activity in excess of 2 nmol [14C]tryptophan per A260 unit. This procedure avoids costly aminoacylation, a step characteristic of other one- and two-step procedures. In two separate purifications 7 and 11 mg of tRNAtrp were prepared from 750 and 1000 g of frozen cells, respectively. This yield compares favorably with that from other procedures. The pure tRNAtrp has been crystallized under several different conditions.

Fidelity of G protein beta-subunit association by the G protein gamma-subunit-like domains of RGS6, RGS7, and RGS11.

Several regulators of G protein signaling (RGS) proteins contain a G protein gamma-subunit-like (GGL) domain, which, as we have shown, binds to Gbeta5 subunits. Here, we extend our original findings by describing another GGL-domain-containing RGS, human RGS6. When RGS6 is coexpressed with different Gbeta subunits, only RGS6 and Gbeta5 interact. The expression of mRNA for RGS6 and Gbeta5 in human tissues overlaps. Predictions of alpha-helical and coiled-coil character within GGL domains, coupled with measurements of Gbeta binding by GGL domain mutants, support the contention that Ggamma-like regions within RGS proteins interact with Gbeta5 subunits in a fashion comparable to conventional Gbeta/Ggamma pairings. Mutation of the highly conserved Phe-61 residue of Ggamma2 to tryptophan, the residue present in all GGL domains, increases the stability of the Gbeta5/Ggamma2 heterodimer, highlighting the importance of this residue to GGL/Gbeta5 association.

Right to left shunt measurement in patients suspect for pulmonary embolism.

31 patients suspect for acute pulmonary emboli were studied by measuring arterial PO2 (room air) and right to left shunt (100% oxygen breathing) to determine if measurement of the right to left shunt aided in the diagnosis of pulmonary embolism. Ventilation/perfusion or serial perfusion lung scans were performed on each patient. All patients exhibited arterial hypoxemia (PaO2 less than or equal to 80) and 27 had a shunt greater than 7%. The shunt was 15.1 +/- 3.6% in 9 patients with lung scans highly suggestive of emboli. 20 patients with lung scans of low probability for emboli had significantly less shunting averaging 10.9 +/- 3.7%. 5 patients of the latter group had shunts averaging 15.2 +/- 3.8% attributable to occult pneumonia not initially apparent. An increased right to left shunt fraction is not diagnostic of pulmonary emboli, but a normal one makes the diagnosis unlikely.