NUCLEAR MAGNETIC RESONANCE STUDIES OF ASPHALTENES AND COALS. A NEW APPROACH TO OBTAINING ASPHALTENE STRUCTURAL PARAMETERS WITH DIPOLAR DEPHASING

ABSTRACT

Apparent carbon aromaticities, fa, of some asphaltenes have been measured by n.m.r. in solution and compared with those obtained by the CP/MAS technique on solid samples. The aromaticities were also measured for several Alberta plains coals. From the 1H solution spectra and 13C solid nmr spectra of asphaltenes, some of their skeletal features, not obtainable from solution spectra only, have been suggested.     

Initial symptoms of nicotine dependence in adolescents

OBJECTIVES: It has been assumed that nicotine dependence has a slow onset and occurs only after prolonged daily use of tobacco. A cohort of young adolescents was followed to determine when the first symptoms of nicotine dependence occur with respect to the duration and frequency of tobacco use. DESIGN: A cohort of 681 seventh grade students (age 12-13 years) from seven schools in two small cities in central Massachusetts was followed over one year. Detailed information regarding tobacco use was obtained in individual confidential interviews conducted in school three times over the year. The latency time to the onset of symptoms of nicotine dependence was measured from the time a subject first smoked at a frequency of at least once per month. RESULTS: 22% of the 95 subjects who had initiated occasional smoking reported a symptom of nicotine dependence within four weeks of initiating monthly smoking. One or more symptoms were reported by 60 (63%) of these 95 subjects. Of the 60 symptomatic subjects, 62% had reported experiencing their first symptom before smoking daily or began smoking daily only upon experiencing their first symptom. DISCUSSION: The first symptoms of nicotine dependence can appear within days to weeks of the onset of occasional use, often before the onset of daily smoking. The existence of three groups of individuals-rapid onset, slower onset, and resistant-distinguishable from one another by their susceptibility to nicotine dependence, is postulated.     

Analysis of xylem formation in pine by cDNA sequencing

Secondary xylem (wood) formation is likely to involve some genes expressed rarely or not at all in herbaceous plants. Moreover, environmental and developmental stimuli influence secondary xylem differentiation, producing morphological and chemical changes in wood. To increase our understanding of xylem formation, and to provide material for comparative analysis of gymnosperm and angiosperm sequences, ESTs were obtained from immature xylem of loblolly pine (Pinus taeda L.). A total of 1,097 single-pass sequences were obtained from 5' ends of cDNAs made from gravistimulated tissue from bent trees. Cluster analysis detected 107 groups of similar sequences, ranging in size from 2 to 20 sequences. A total of 361 sequences fell into these groups, whereas 736 sequences were unique. About 55% of the pine EST sequences show similarity to previously described sequences in public databases. About 10% of the recognized genes encode factors involved in cell wall formation. Sequences similar to cell wall proteins, most known lignin biosynthetic enzymes, and several enzymes of carbohydrate metabolism were found. A number of putative regulatory proteins also are represented. Expression patterns of several of these genes were studied in various tissues and organs of pine. Sequencing novel genes expressed during xylem formation will provide a powerful means of identifying mechanisms controlling this important differentiation pathway.     

The conserved carboxyl terminus and zinc finger-like domain of the co-chaperone Ydj1 assist Hsp70 in protein folding

Ydj1 is a member of the Hsp40 (DnaJ-related) chaperone family that facilitates cellular protein folding by regulating Hsp70 ATPase activity and binding unfolded polypeptides. Ydj1 contains four conserved subdomains that appear to represent functional units. To define the action of these regions, protease-resistant Ydj1 fragments and Ydj1 mutants were analyzed for activities exhibited by the unmodified protein. The Ydj1 mutant proteins analyzed were unable to support growth of yeast at elevated temperatures and were found to have alterations in the J-domain (Ydj1 H34Q), zinc finger-like region (Ydj1 C159T), and conserved carboxyl terminus (Ydj1 G315D). Fragment Ydj1 (1-90) contains the J-domain and a small portion of the G/F-rich region and could regulate Hsp70 ATPase activity but could not suppress the aggregation of the model protein rhodanese. Ydj1 H34Q could not regulate the ATPase activity of Hsp70 but could bind unfolded polypeptides. The J-domain functions independently and was sufficient to regulate Hsp70 ATPase activity. Fragment Ydj1 (179-384) could suppress rhodanese aggregation but was unable to regulate Hsp70. Ydj1 (179-384) contains the conserved carboxyl terminus of DnaJ but is missing the J-domain, G/F-rich region, and a major portion of the zinc finger-like region. Ydj1 G315D exhibited severe defects in its ability to suppress rhodanese aggregation and form complexes with unfolded luciferase. The conserved carboxyl terminus of Ydj1 appeared to participate in the binding of unfolded polypeptides. Ydj1 C159T could form stable complexes with unfolded proteins and suppress protein aggregation but was inefficient at refolding denatured luciferase. The zinc finger-like region of Ydj1 appeared to function in conjunction with the conserved carboxyl terminus to fold proteins. However, Ydj1 does not require an intact zinc finger-like region to bind unfolded polypeptides. These data suggest that the combined functions of the J-domain, zinc finger-like region, and the conserved carboxyl terminus are required for Ydj1 to cooperate with Hsp70 and facilitate protein folding in the cell.     

Protein folding activity of Hsp70 is modified differentially by the hsp40 co-chaperones Sis1 and Ydj1

Specification of Hsp70 action in cellular protein metabolism may occur through the formation of specialized Hsp70:Hsp40 pairs. To test this model, we compared the ability of purified Sis1 and Ydj1 to regulate the ATPase and protein-folding activity of Hsp70 Ssa1 and Ssb1/2 proteins. Ydj1 and Sis1 could both functionally interact with Ssa1, but not the Ssb1/2 proteins, to refold luciferase. Interestingly, Ydj1:Ssa1 could promote up to four times more luciferase folding than Sis1:Ssa1. This functional difference was explored and could not be accounted for by differences in the ability of Sis1 and Ydj1 to regulate Ssa1 ATPase activity. Instead, differences in the chaperone function of Ydj1 and Sis1 were observed. Ydj1 was dramatically more effective than Sis1 at suppressing the thermally induced aggregation of luciferase. Paradoxically, Sis1 and Ydj1 could bind similar quantities of chemically denatured luciferase. The polypeptide binding domain of Sis1 was found to lie between residues 171-352 and correspond to its conserved carboxyl terminus. The conserved carboxyl terminus of Ydj1 is also known to participate in the binding of nonnative polypeptides. Thus, Ydj1 appears more efficient at assisting Ssa1 in folding luciferase because its contains a zinc finger-like region that is absent from Sis1. Ydj1 and Sis1 are structurally and functionally distinct Hsp40 proteins that can specify Ssa1 action by generating Hsp70:Hsp40 pairs that exhibit different chaperone activities.     

Donor–Acceptor C60‐Containing Polyferrocenylsilanes: Synthesis,Characterization, and Applications in Photodiode Devices

A series of polyferrocenylsilane (PFS) random copolymers containing covalently bound pendant [C₆₀]fullerene groups, the first well‐characterized metallopolymers with pendant C₆₀ units, have been prepared and characterized. The fullerene content of the prepared copolymers ranges from 7 to 24% relative to monomer unit. The desired copolymers were synthesized in three steps: metal‐catalyzed ring opening polymerization of sila[1]ferrocenophanes was performed to synthesize random copolymers of poly(ferrocenylmethylphenylsilane‐co‐ferrocenylchloromethylsilane); the resulting random PFSs were then functionalized by reaction with 11‐azido‐1‐undecanol to give PFSs with pendant azide groups; the desired donor–acceptor C₆₀‐containing PFSs were then synthesized by the reaction of the azide group in the side chains with C₆₀ in toluene at 110 °C. The resulting C₆₀‐containing PFSs are air‐stable and soluble in aromatic solvents, chloroform, or THF. The UV‐vis spectra of these materials show broad absorption up to 800 nm. Thin films of these materials were examined as the active layer in rare examples of all solid‐state sandwich‐type diode devices based on ferrocene‐fullerene dyads. The devices exhibit photoconducting and photovoltaic responses, with an open circuit potential of ca. 0.3 V under white light illumination.     

Psychiatric hospital admission rates: Facts and artifacts.

Examined types of patient admissions in the 1st yr of a new psychiatric hospital opening to address issues raised by I. Silverman and D. Saunders (see record 1982-01855-001). It was found that, for all patients residing in the county where the new facility was located, 39%, 48%, and 13% were transfer admissions, readmissions, and 1st admissions, respectively. By using a more valid definition of the same criterion variable (admission rates), these results question Silverman and Saunders's interpretation of the same data. (French abstract) (3 ref) (PsycINFO Database Record (c) 2011 APA, all rights reserved)