Synthesis of Three New Carbocyclic Analogues of 3′-Deoxy Purine Ribonucleosides

Abstract

The 1-hydroxymethyl-3-cyclopentene (4) was converted, after epoxidation, to two new exocyclic amino carbocyclic nucleosides (1, 2), and a new cyclopentane nucleoside analogue (3), with potential biological activities. The regioselectivity of the epoxidation (4), which is the key step, is governed by steric control using aryl and silyl hydroxyl protecting groups.     

Identification of a complete set of functional markers for the selection of er1 powdery mildew resistance in Pisum sativum L.

Powdery mildew is the most widespread disease of pea (Pisum sativum L.) and causes severe economic losses worldwide. Recessively inherited er1 powdery mildew resistance, successfully used for decades in pea breeding programs, has recently been shown to originate from the loss of function of the PsMLO1 gene. Five er1 alleles, each corresponding to a different PsMLO1 null mutation, have been characterized to date in pea germplasm. In order to aid er1 selection, we aimed to identify functional markers which target PsMLO1 polymorphisms directly responsible for the resistant phenotype. Highly informative cleaved amplified polymorphic sequence (CAPS), derived cleaved amplified polymorphic sequence (dCAPS), sequence tagged site (STS) and high-resolution melting (HRM) markers were developed which enable the selection of each of the five er1 alleles. Taken together, the results described here provide a powerful tool for breeders, overcoming limitations of previously reported er1-linked markers due to the occurrence of recombination with the resistance locus and/or the lack of polymorphism between parental genotypes. The HRM marker er1-5/HRM54 reported here, targeting a mutagenesis-induced er1 allele recently described by us, does not require manual processing after PCR amplification, and is therefore suitable for large-scale breeding programs based on high-throughput automated screening.     

ATM-deficient human neural stem cells as an in vitro model system to study neurodegeneration

Loss of ATM kinase, a transducer of the DNA damage response and redox sensor, causes the neurodegenerative disorder ataxia-telangiectasia (A-T). While a great deal of progress has been made in elucidating the ATM-dependent DNA damage response (DDR) network, a key challenge remains in understanding the selective susceptibility of the nervous system to faulty DDR. Several factors appear implicated in the neurodegenerative phenotype in A-T, but which of them plays a crucial role remains unclear, especially since mouse models of A-T do not fully mirror the respective human syndrome. Therefore, a number of human neural stem cell (hNSC) systems have been developed to get an insight into the molecular mechanisms of neurodegeneration as consequence of ATM inactivation. Here we review the hNSC systems developed by us an others to model A-T.     

An innovative approach to grape metabolomics: stilbene profiling by suspect screening analysis

Suspect screening analysis is a targeted metabolomics approach in which identification of compounds relies on specific available information such as their molecular formula and isotopic pattern. This method was applied to the study of grape metabolomics with an UPLC/MS high-resolution Q-TOF mass spectrometer (nominal resolution 40,000) coupled with a Jet Stream ionization source. The present paper describes the detailed qualitative and quantitative study of grape stilbenes, the principal polyphenols associated with the beneficial effects of drinking wine. For identification of compounds, a new database was expressly constructed from the molecular information of potential metabolites of grape and wine from the literature and other electronic databases. Currently, GrapeMetabolomics contains about a thousand putative grape compounds. If untargeted analysis of a sample provides identification of a new compound with a sufficiently confident score, it is added to the database. Thus, by increasing the number of samples studied, GrapeMetabolomics can be expanded. This method is effective for identification of the molecular formulae of several hundred metabolites in two runs (positive and negative ionization) with minimal sample preparation, and can also be used to analyse some single classes of compounds involved in cell and tissue metabolism. With this approach, a total of 18 stilbene derivatives was identified in two grape samples (Raboso Piave and Primitivo) on the basis of accurate mass measurements and isotopic patterns, and identification was confirmed by MS/MS analysis. The approach can also potentially be applied to the metabolomics of other plant varieties.     

The Use of Climatic Niches in Screening Procedures for Introduced Species to Evaluate Risk of Spread: A Case with the American Eastern Grey Squirrel

Species introduction represents one of the most serious threats for biodiversity. The realized climatic niche of an invasive species can be used to predict its potential distribution in new areas, providing a basis for screening procedures in the compilation of black and white lists to prevent new introductions. We tested this assertion by modeling the realized climatic niche of the Eastern grey squirrel Sciurus carolinensis. Maxent was used to develop three models: one considering only records from the native range (NRM), a second including records from native and invasive range (NIRM), a third calibrated with invasive occurrences and projected in the native range (RCM). Niche conservatism was tested considering both a niche equivalency and a niche similarity test. NRM failed to predict suitable parts of the currently invaded range in Europe, while RCM underestimated the suitability in the native range. NIRM accurately predicted both the native and invasive range. The niche equivalency hypothesis was rejected due to a significant difference between the grey squirrel’s niche in native and invasive ranges. The niche similarity test yielded no significant results. Our analyses support the hypothesis of a shift in the species’ climatic niche in the area of introductions. Species Distribution Models (SDMs) appear to be a useful tool in the compilation of black lists, allowing identifying areas vulnerable to invasions. We advise caution in the use of SDMs based only on the native range of a species for the compilation of white lists for other geographic areas, due to the significant risk of underestimating its potential invasive range.     

Elevated atmospheric CO2 modifies responses to water-stress and flowering of Mediterranean desert truffle mycorrhizal shrubs

Predicted increases in atmospheric concentration of carbon dioxide (CO₂) coupled with increased temperatures and drought are expected to strongly influence the development of most of the plant species in the world, especially in areas with high risk of desertification like the Mediterranean basin. Helianthemum almeriense is an ecologically important Mediterranean shrub with an added interest because it serves as the host for the Terfezia claveryi mycorrhizal fungus, which is a desert truffle with increasingly commercial interest. Although both plant and fungi are known to be well adapted to dry conditions, it is still uncertain how the increase in atmospheric CO₂ will influence them. In this article we have addressed the physiological responses of H. almeriense × T. claveryi mycorrhizal plants to increases in atmospheric CO₂ coupled with drought and high vapor pressure deficit. This work reports one of the few estimations of mesophyll conductance in a drought deciduous Mediterranean shrub and evaluates its role in photosynthesis limitation. High atmospheric CO₂ concentrations help desert truffle mycorrhizal plants to cope with the adverse effects of progressive drought during Mediterranean springs by improving carbon net assimilation, intrinsic water use efficiency and dispersal of the species through increased flowering events.     

Psychiatric disorders and SLC6A4 gene variants: possible effects on alcohol dependence and alzheimer’s disease

Molecular Biology Reports - Serotoninergic system is one of the most important neurotransmission systems investigated in the field of psychiatry. Extensive evidence reveals how alterations of this...     

1H-NMR Investigation of the Interaction of the Amino Terminal Domain of the LexA Repressor with a Synthetic Half-Operator

Abstract

A synthetic half-operator DNA-duplex, d(GCTACTGTATGT), containing a portion of the proposed recognition sequence (CTGT) of serveral “SOS” genes, has been synthesized. The dodecamer has been characterized through ¹H-NMR spectroscopy. Complete assignment of exchangeable hydrogen bonded imino protons has been acheived by applying 1D NOE techniques and an analysis of the temperature dependence of the chemical shifts. In order to determine the specific role of the CTGT consensus sequence in the overall recognition process, the oligonucleotide duplex has been titrated with the amino terminal DNA binding domain of the LexA repressor. The observation of substantial changes of ¹H-NMR chemical shifts in the imino proton region upon interaction with the protein strongly suggests that the protein binds specifically to the operator DNA. The largest deviations of ¹H-NMR chemical shifts upon protein binding have been observed for protons assigned to the CTGT segment, thus strongly suggesting a direct involvement of this sequence in the binding process. At high potassium chloride concentrations the ¹H-NMR chemical shift deviations are reverted which is consistent with the known drop in the affinity constant of LexA for operator DNA at high salt concentrations.