Fast, efficient and selective deprotection of the tert-butoxycarbonyl (Boc) group using HCl/dioxane (4 m).

Fast, efficient and selective deprotection of the tert-butoxycarbonyl (Boc) group of various amino acids and peptides was achieved by using hydrogen chloride (4 m) in anhydrous dioxane solution for 30 min at room temperature. In the cases studied in our laboratory, this protocol provided superior selectivity to deprotect Nalpha-Boc groups in the presence of tert-butyl esters and tert-butyl ethers, including thio-tert-butyl ethers, but not phenolic tert-butyl ethers.     

Determination of opipramol in human plasma by high-performance liquid chromatography with photometric detection using a cyanopropyl column

A high-performance liquid chromatographic method is described for the determination of opipramol in human plasma. Opipramol was extracted into tert.-butylmethyl ether, separated on a cyanopropyl silica column and detected at 254 nm. Imipramine was used as internal standard. The limit of quantitation was 250 pg/ml using 1.5 ml plasma. Precision was better than 9%, inaccuracy less than 8%. The assay is more sensitive than previously published methods, and it has been applied to the analysis of plasma samples from a pharmacokinetic study.     

Plant litter feedback and population dynamics in an annual plant,<Emphasis Type="Italic"> Cardamine pensylvanica</Emphasis>

The presence of litter has the potential to alter the population dynamics of plants. In this paper, we explore the effects of litter on population dynamics using a simple experimental laboratory system with populations of the annual crucifer, Cardamine pensylvanica. Using a factorial experiment with four densities and three litter levels, we determined the effect of litter on biomass and plant fecundity, and the life stages responsible for these changes in yield. Although litter had significant effects on seed germination and on seedling survivorship, we show, using a population dynamics model, that these effects were not demographically significant. Rather, the potential effect of litter on population dynamics resulted almost entirely from its effect on biomass. Persistent litter suppressed plant biomass and apparently removed the direct density effect present in the absence of litter. Thus, litter changed the shape of the recruitment curve from slightly humped to asymptotic. In addition to changing the shape of the recruitment curve, litter reduced the carrying capacity of the populations. Thus, the population dynamics model indicated that not all statistically significant responses were dynamically significant. Given the potential complexity of litter effects, simple population models provide a powerful tool for understanding the potential consequences of short-term responses. Received: 8 September 1999 / Accepted: 5 April 2000     

Conformational heterogeneity of the bacteriopheophytin electron acceptor HA in reaction centers from Rhodopseudomonas viridis revealed by Fourier transform infrared spectroscopy and site-directed mutagenesis.

The light-induced Fourier transform infrared (FTIR) difference spectra corresponding to the photoreduction of either the HA bacteriopheophytin electron acceptor (HA-/HA spectrum) or the QA primary quinone (QA-/QA spectrum) in photosynthetic reaction centers (RCs) of Rhodopseudomonas viridis are reported. These spectra have been compared for wild-type (WT) RCs and for two site-directed mutants in which the proposed interactions between the carbonyls on ring V of HA and the RC protein have been altered. In the mutant EQ(L104), the putative hydrogen bond between the protein and the 9-keto C=O of HA should be affected by changing Glu L104 to a Gln. In the mutant WF(M250), the van der Waals interactions between Trp M250 and the 10a-ester C=O of HA should be modified. The characteristic effects of both mutations on the FTIR spectra support the proposed interactions and allow the IR modes of the 9-keto and 10a-ester C=O of HA and HA- to be assigned. Comparison of the HA-/HA and QA-/QA spectra leads us to conclude that the QA-/QA IR signals in the spectral range above 1700 cm-1 are largely dominated by contributions from the electrostatic response of the 10a-ester C=O mode of HA upon QA photoreduction. A heterogeneity in the conformation of the 10a-ester C=O mode of HA in WT RCs, leading to three distinct populations of HA, appears to be related to differences in the hydrogen-bonding interactions between the carbonyls of ring V of HA and the RC protein. The possibility that this structural heterogeneity is related to the observed multiexponential kinetics of electron transfer and the implications for primary processes are discussed. The effect of 1H/2H exchange on the QA-/QA spectra of the WT and mutant RCs shows that neither Glu L104 nor any other exchangeable carboxylic residue changes appreciably its protonation state upon QA reduction.     

Identification of Culturable Oligotrophic Bacteria within Naturally Occurring Bacterioplankton Communities of the Ligurian Sea by 16S rRNA Sequencing and Probing

Abstract Typical marine bacteria (i.e., obligately oligotrophic) that were numerically dominant members of naturally occurring marine communities were identified by cloning and sequencing the amplified 16S rRNA genes obtained from dilution cultures of the original samples. The data reported here refer to two different habitats of a marine pelagic environment (28 miles offshore, in the northwestern Mediterranean Sea). The samples were taken from the water column at two representative layers, i.e., the 30-m depth, corresponding to the chlorophyll maximum layer, and the 1800-m depth, representative of a deep, oligotrophic environment. Three major lineages were found in the 16S rDNA clone libraries prepared from the two samples, two of which could be assigned to the Vibrio and the Rhodobacter groups. The third lineage was a distant relative of the genus Flavobacterium, but it was not closely related to any marine isolate. Six oligonucleotide probes, either complementary to the conserved sequence domains or selectively hybridizing to the clone sequences, were designed for use as hybridization group-specific and strain-specific probes. A single-mismatch discrimination between certain probes and nontarget sequences was demonstrated by detecting the probes' specificity at different hybridization and washing conditions. The screening of the clone libraries with the obtained probes revealed that neither the 30-m sample higher dilution nor the 1800-m one were pure cultures. While some representatives of the Vibrio group were found in both the surface and the deep sample, the members of the Flavobacterium and Rhodobacter lineages were detected only in the deep and the euphotic layers, respectively. We suggest an approach for analyzing autochthonous marine bacteria able to grow in unamended seawater. Received: 19 May 1998; Accepted: 29 October 1998     

Variable modes of inheritance of morphometrical traits in hybrids between Drosophila melanogaster and Drosophila simulans.

We investigated body-size inheritance in interspecific sterile hybrids by crossing a Drosophila simulans strain with 13 strains of Drosophila melanogaster, which were of various origins and chosen for their broad range of genetic variation. A highly significant parent-offspring correlation was observed, showing that the D. melanogaster genes for size are still expressed in a hybrid background. Superimposed on to this additive inheritance, the size of hybrids was always less than the mid-parent value. This phenomenon, which at first sight might be described as dominance or overdominance, is more precisely interpreted as a consequence of a hybrid breakdown, that is, a dysfunction of the parental genes for size when put to work together. This interpretation is enforced by the fact that phenotypic variability was much more prevalent in hybrids than in parents. We also analysed body pigmentation inheritance in the same crosses and got a very different picture. There was no increase in the phenotypic variance of F(1) hybrids and only a low parent-offspring correlation. Apparent overdominance could be observed but in opposite directions, with no evidence of hybrid breakdown. Our data point to the possibility of analysing a diversity of quantitative traits in interspecific hybrids, and indicate that breakdown might be restricted to some traits only.     

New Gene Crt(Curly Roots) Controlling Pea (Pisum sativum L.) Root Development

Using ethyl methane sulfonate (EMS) treatment of the seeds ofline SGE, a new mutant of pea (Pisum sativum L.) with alterationsin root development was obtained. The mutant phenotype dependson the density of the growth substrate: on sand (a high densitysubstrate) the mutant forms a small compact curly root systemwhereas on vermiculite (a low density substrate) differencesbetween the root systems of the mutant and wild type plantsare less pronounced. Genetic analysis revealed that the mutantcarries a mutation in a new pea gene designedcrt (curly roots).Gene crt has been localized in pea linkage group V. The mutantline named SGEcrt showed increased sensitivity to exogenousauxin and an increased concentration of endogenous indole-3-aceticacid (IAA) in comparison with the wild type line SGE. Copyright2000 Annals of Botany Company Pisum sativum L., root development, garden pea mutant, curly roots, auxin, environmental stimulus response     

On Branching Processes and the Early Stages of the Spread of an Epidemic

Branchingprocess(BP)isusedtomodeltheearlystagesofthespreadofasexuallytransmitteddisease.TheearlystagesofAIDSspreadwhichistransmittedbothhomosexuallyandheterosexuallyarestudiedasaBP.