Expression and functional analysis of aspartate transcarbamoylase and role of de novo pyrimidine synthesis in regulation of growth and development in Arabidopsis.

Aspartate transcarbamoylase (ATCase, EC 2.1.3.

Palladium-catalyzed [3+2] cycloaddition of carbon dioxide and trimethylenemethane under mild conditions.

Carbon dioxide undergoes a Pd-catalyzed [3+2] cycloaddition with trimethylenemethane (TMM) under mild conditions (1 atm, 75 degrees C, 30 min) to produce a gamma-butyrolactone product in 63% yield, when the Pd-TMM complex is generated from 2-(acetoxymethyl)-3-(trimethylsilyl)propene. The reaction reported here is more rapid than the all-carbon [3+2] cycloaddition, and only the gamma-butyrolactone is produced in a competition experiment. With substituted substrates, the reaction is completely regioselective, producing the product derived from the kinetic Pd-TMM complex.

Effects of discontinuities in the DNA template on abortive initiation and promoter escape by Escherichia coli RNA polymerase.

Using singly gapped or nicked templates containing the T7A1 promoter, we have measured several kinetic parameters related to the process of transcription initiation by Escherichia coli RNA polymerase, confirming and extending previous results using a population of randomly gapped templates. A reduced probability of transcript abortion at RNA lengths of 6 and 7 nucleotides and a lower ratio of abortive to productive initiation events was observed for some discontinuous templates, consistent with models attributing abortive initiation to the accumulation of strain in the initiating complex. The effect of DNA discontinuity on abortion of shorter RNA transcripts (2-3 nucleotides) was less pronounced; abortion at these short chain lengths may primarily be attributed to the low stability of the RNA-DNA hybrid.

To avoid or deter: interactions among defensive and escape strategies in sabellid worms.

Numerous studies demonstrate how sessile marine organisms utilize chemical, structural, and nutritional deterrents to persist in predator-rich environments. Little is known, however, about how mobile, more behaviorally complex species minimize predation by integrating avoidance and deterrence strategies. We investigated this using sabellid polychaete worms from the Caribbean and temperate western Atlantic.

Emission wavelength dependence of fluorescence lifetimes of bacteriological spores and pollens.

Concern about biological terrorism has greatly increased in the 21st century, and correspondingly, so has the need for accurate detection and identification of biological hazards, such as Bacillus anthracis. Optical techniques have been shown to be useful for this purpose. Use of fluorescence lifetimes as a function of emission wavelength for different materials using point- detection methods appears to be an additional viable option.

Effect of a synesthete's photisms on name recall.

A multilingual, colored-letter synesthete professor (MLS), 9 nonsynesthete multilingual professors and 4 nonsynesthete art professors learned 30 names of individuals (first and last name pairs) in three trials. They recalled the names after each trial and six months later, as well as performed cued recall trials initially and after six months. As hypothesized, MLS recalled significantly more names than control groups on all free recall tests (except after the first trial) and on cued recall tests.

Teaching technical and professional skills using a laboratory exercise: A comparison of two methods of plasmid preparation.

This laboratory exercise encourages upper level biochemistry students to build and expand upon previously developed laboratory skills and knowledge as they conduct a comparison of two methods of plasmid preparation based upon cost, quality of product, production time, and environmental impact. Besides creating an environment that mimics a more realistic practice of science, there are several key learning objectives. First, students will learn to effectively plan and manage time so that they can meet a scientific goal.

Genes, enzymes and regulation of arginine biosynthesis in plants.

Arabidopsis genes encoding enzymes for each of the eight steps in L-arginine (Arg) synthesis were identified, based upon sequence homologies with orthologs from other organisms. Except for N-acetylglutamate synthase (NAGS; EC 2.3.

Effects of phosphate limitation on expression of genes involved in pyrimidine synthesis and salvaging in Arabidopsis.

Arabidopsis seedlings grown for 14 d without phosphate (P) exhibited stunted growth and other visible symptoms associated with P deficiency. RNA contents in shoots decreased nearly 90%, relative to controls. In shoots, expression of Pht1;2, encoding an inducible high-affinity phosphate transporter, increased threefold, compared with controls, and served as a molecular marker for P limitation.

"Seeing things in my head": a synesthete's images for music and notes.

We explored synesthetic experiences (photisms) elicited by music and notes for GS, a 22-year-old female college student, who is a genuine digit synesthete (Mills et al 1999 Cognitive Neuropsychology 16 181-191). After extensive interviews, we conducted five studies using synthesizer notes in different octaves and in different instrument sounds. GS described, drew, or selected her photisms from alternatives.

The color of two alphabets for a multilingual synesthete.

Interviews with a multilingual synesthete (MLS), who experiences colored letters for Roman and Cyrillic alphabets and for digits, revealed stable synesthetic experiences over 2 1/2 - 5 years. Colors of Cyrillic letters were based on Roman letters. Four Stroop tests involving both types of letters showed that MLS was able to name print color faster if the colors matched her synesthetic colors, showing that synesthesia is automatic.

Facing disability with resources from Aristotle and Nietzsche.

Suddenly unable to walk, I found resources for facing disability in the works of Aristotle and Nietzsche, even though their respective ethical schemes are incommensurable. Implementing Amélie Rorty's notion of crop rotation, I show how each scheme offers the patient something quite indispensable, having to do with how each has its own judgmentally-motivated psychological underpinnings. Aristotle's notion of empathy, wherein the moral move occurs whenever we take up someone else's good as our own, is empowering, especially to those who face an imperiled embodiment.

The roles of specific template nucleosides in the formation of stable transcription complexes by Escherichia coli RNA polymerase.

We have examined the effects of removing individual template nucleosides on promoter escape by Escherichia coli RNA polymerase in vitro. The ability of DNA templates containing random single nucleoside gaps generated by hydroxyl radical treatment to support the production of stable ternary transcription complexes was analyzed. On two templates containing different promoter and initial transcribed regions, we found that removal of nucleosides on the template strand in the region from -13 to at least +8 relative to the transcription start site interfered with ternary complex formation.

Spectrophotometric studies of complexation of C60 with aromatic hydrocarbons.

The equilibrium constants for complexation of C60 with naphthalene, phenanthrene and pyrene in toluene have been determined by UV visible spectroscopy. The magnitude of the equilibrium constants was found to increase with decreasing ionization potential of the donor. Values for complexation enthalpy have been determined for the first time for C60/aromatic hydrocarbons.

Isolation and characterization of a cDNA encoding a pea ornithine transcarbamoylase (argF) and comparison with other transcarbamoylases.

We used a PCR-based library screening method to isolate a 1.4 kb pea leaf cDNA encoding ornithine transcarbamoylase (OTCase). The cDNA contains a single major ORF of 375 amino acids whose deduced sequence exhibits a high degree of homology with other OTCases.

Molecular cloning and characterization of the pyrB1 and pyrB2 genes encoding aspartate transcarbamoylase in pea (Pisum sativum L.).

We cloned cDNAs encoding two different pea (Pisum sativum L.) aspartate transcarbamoylases (ATCases) by complementation of an Escherichia coli delta pyrB mutant. The two cDNAs, designated pyrB1 and pyrB2, encode polypeptides of 386 and 385 amino acid residues, respectively, both of which exhibit typical chloroplast transit peptide sequences.

A semi-natural habitat for housing small, nonhuman primates.

A semi-natural habitat that was designed to house a social group of squirrel monkeys (Saimiri sciureus sciureus) at Goucher College, in Maryland is described. The design could be readily adapted for use with other small primate species.

Interaction of porphyrins and metalloporphyrins with nucleic acids.

Differences in the interpretation of the details of the binding of porphyrins and metalloporphyrins to nucleic acids do exist, in part arising from the fact that different experimental techniques require different experimental conditions. For example, uv/vis absorption and CD spectroscopy use mumol/L and 10 to 100 mumol/L concentrations of drug and polymer respectively; whereas NMR uses mmol/l concentrations, increasing the likelihood of DNA aggregation. Differences in solvent conditions can have a profound effect on binding; changes in binding mode with changes in ionic strength have been observed for two of the porphyrins studied.

Self-assembly of porphyrins on nucleic acid templates.

The cis and trans isomers of dicationic bis(4-N-methylpyridyl)diphenylporphine show a much greater tendency to aggregate than similar tetracationic porphyrins. Upon binding to nucleic acids these aggregating dicationic porphyrins form long-range structures on the polymer template giving intense circular dichroism signals whose profile reports the helical sense of the DNA.

Mental curve tracing with elementary stimuli.

It has been proposed that certain spatial relations are determined by an operation, or "visual routine," that can trace along a boundary (Ullman, 1984). This proposal was supported by Jolicoeur, Ullman, and Mackay's (1986) finding that the time required to determine if two Xs are on the same curve increased monotonically with the separation of the Xs along that curve. In the present study the generality of the curve tracing hypothesis was explored across four experiments by using elementary stimuli that eliminated interweaving curves, displaced the fixation point away from the curves and target Xs, and provided a simple alternative to curve tracing--namely, determining whether or not the Xs fell on the same side of the figure.

Heterosexual involvement of unmarried under-graduate females in relation to self-evaluations.

It was hypothesized that a higher degree of heterosexual involvement among unmarried female undergraduates would be associated with more positive self-evaluations. This idea was investigated among 79 college women tested as freshmen, and again as sophomores, juniors, and seniors. Self-esteem, ratings of physical attractiveness, ratings of future marriage, and seriousness about boyfriend increased over the years, while number of different men dated declined.

Carol Gilligan's theory of sex differences in the development of moral reasoning during adolescence.

Gilligan's work, which focuses on sex differences in moral reasoning, the perception of violence, the resolution of sexual dilemmas and abortion decisions, poses a major challenge to Kohlberg's theory by introducing a feminist perspective of moral development. Kohlberg had shown that the average female attained a moral judgment rating of stage three (good boy-nice girl), while adolescent males score at level four (law and order) and are more likely to move on to postconventional levels. Gilligan suggests that these findings reveal a gender bias, not that females are less mature than boys.