Effect of a modified thymine on the structure and stability of [d(TGGGT)]4 quadruplex

Telomeric guanine-rich sequence can adopt quadruplex structures that are important for their biological role in chromosomal stabilisation. G quartets are characterised by the cyclic hydrogen bonding of four guanine bases in a coplanar arrangement and their stability is ion-dependent. In this work we compare the stability of [d(TGGGT)]₄ and [d(T*GGGT)]₄ quadruplexes. The last one contains a modified thymine, where the hydroxyl group substitutes one hydrogen atom of the methyl group of the thymine in the [d(TGGGT)]₄ sequence. We used a combination of spectroscopic, calorimetric and computational techniques to characterise the G-quadruplex formation. NMR and CD spectra of [d(T*GGGT)]₄ were characteristic of parallel-stranded, tetramolecular quadruplex. CD and DSC melting experiments reveal that [d(T*GGGT)]₄ is less stable that unmodified quadruplex. Molecular models suggest possible explanation for the observed behaviour.     

Illustrations cliniques en cardiologie

The examples and clinical cases presented in this section are not intended to be considered as absolute models in terms of image quality or device parameter settings. They must initiate an individual analysis according to CT parameters and image quality. Nevertheless, they present practically different CT levels which can be used according to the clinical context and the type of device.     

Respect for outsiders? respect for the law? the moral evaluation of high scale issues by US immigration officers

High-scale morality is the study of moral ideas and sentiments deployed in relations that encompass multiple, geographically or socially distant populaces. The envisioning of distant people, their attributed moral personhood, the evaluation of their perceived behaviour, and the rectification of wrongs through the use of powerful organizations are key topics in high-scale morality. High-scale morality differs from existing anthropological approaches that emphasize local ethnography or contrastive moral ideas; it addresses the moralization of issues like world hunger, the drug trade, or international migration. The officers of the US Immigration and Naturalization Service understand and evaluate legal and illegal immigrants, as well as directly enacting moral rectification for the US polity. As they resolve moral dilemmas on their job, they utilize pervasive models for moral thought and action in capitalist, individualist, stratified, and bureaucratized societies. The article finishes by considering directions in which anthropology can contribute to understanding the moral dimension of global issues.     

Microbiome dynamics of human epidermis following skin barrier disruption

Background

Recent advances in sequencing technologies have enabled metagenomic analyses of many human body sites. Several studies have catalogued the composition of bacterial communities of the surface of human skin, mostly under static conditions in healthy volunteers. Skin injury will disturb the cutaneous homeostasis of the host tissue and its commensal microbiota, but the dynamics of this process have not been studied before. Here we analyzed the microbiota of the surface layer and the deeper layers of the stratum corneum of normal skin, and we investigated the dynamics of recolonization of skin microbiota following skin barrier disruption by tape stripping as a model of superficial injury.

Results

We observed gender differences in microbiota composition and showed that bacteria are not uniformly distributed in the stratum corneum. Phylogenetic distance analysis was employed to follow microbiota development during recolonization of injured skin. Surprisingly, the developing neo-microbiome at day 14 was more similar to that of the deeper stratum corneum layers than to the initial surface microbiome. In addition, we also observed variation in the host response towards superficial injury as assessed by the induction of antimicrobial protein expression in epidermal keratinocytes.

Conclusions

We suggest that the microbiome of the deeper layers, rather than that of the superficial skin layer, may be regarded as the host indigenous microbiome. Characterization of the skin microbiome under dynamic conditions, and the ensuing response of the microbial community and host tissue, will shed further light on the complex interaction between resident bacteria and epidermis.     

Cell cycle and behaviour in Euplotes crassus: an attempt at describing the biological relationship between its cellular and organismic natures

The two-faced nature of protozoa allowed us to study the relationship between cell cycle and behaviour in Euplotes crassus; the former represents one of the most typical cellular traits, the latter is one of the most significant characteristics of an organism. Dividing cells of E. crassus were isolated on a slide and recorded for 11 h: the classic ethographic parameters were calculated every 60 min. The percentage of mobile cells went from 0-100% in the first 2.5 h. This value was maintained for 6.5 h, but from 9 h the value began to drop, reaching 0% at 11 h. The relative frequency of leftward arcs was very high in the first hour, the radius and length of the arcs increased from 1-7 h; velocity showed a similar trend, peaking at 7 h. All our results showed that the behaviour of this ciliate is heavily affected by its cell-division cycle.     

Mapping of citrullinated fibrinogen B-cell epitopes in rheumatoid arthritis by imaging surface plasmon resonance

Introduction  

Rheumatoid arthritis (RA) frequently involves the loss of tolerance to citrullinated antigens, which may play a role in pathogenicity. Citrullinated fibrinogen is commonly found in inflamed synovial tissue and is a frequent target of autoantibodies in RA patients. To obtain insight into the B-cell response to citrullinated fibrinogen in RA, its autoepitopes were systematically mapped using a new methodology.     

5'-Modified G-quadruplex forming oligonucleotides endowed with anti-HIV activity: synthesis and biophysical properties

Oligodeoxyribonucleotides of sequence d(5'TGGGAG3') carrying bulky aromatic groups at the 5' end were found to exhibit potent anti-HIV activity [Hotoda, H., et al. (1998) J. Med. Chem. 41, 3655-3663 and references therein]. Structure-activity relationship investigations indicated that G-quadruplex formation, as well as the presence of large aromatic substituents at the 5'-end, were both essential for their antiviral activity. In this work, we synthesized some representative examples of the anti-HIV active Hotoda's 6-mers and analyzed the resulting G-quadruplexes by CD, DSC, and molecular modeling studies, in comparison with the unmodified oligonucleotide. In the case of the sequence carrying the 3,4-dibenzyloxybenzyl (DBB) group, identified as the best candidate for further drug optimization, we developed an alternative protocol to synthesize the 5'-DBB-thymidine phosphoramidite building block in higher yields. The thermodynamic and kinetic parameters for the association/dissociation processes of the 5'-conjugated quadruplexes, determined with respect to the unmodified one, were discussed in light of the molecular modeling studies. The aromatic groups at the 5' position of d(5'TGGGAG3') dramatically enhance both the equilibrium and the rate of formation of the quadruplex complexes. The overall stability of the investigated quadruplexes was found to correlate with the reported IC50 values, thus furnishing quantitative evidence for the hypothesis that the G-quadruplex structures are the ultimate active species, effectively responsible for the biological activity.     

Ultrasound imaging in an experimental model of fatty liver disease and cirrhosis in rats

Background

Atypical scrapie was first identified in Norwegian sheep in 1998 and has subsequently been identified in many countries. Retrospective studies have identified cases predating the initial identification of this form of scrapie, and epidemiological studies have indicated that it does not conform to the behaviour of an infectious disease, giving rise to the hypothesis that it represents spontaneous disease. However, atypical scrapie isolates have been shown to be infectious experimentally, through intracerebral inoculation in transgenic mice and sheep. The first successful challenge of a sheep with 'field' atypical scrapie from an homologous donor sheep was reported in 2007.

Results

This study demonstrates that atypical scrapie has distinct clinical, pathological and biochemical characteristics which are maintained on transmission and sub-passage, and which are distinct from other strains of transmissible spongiform encephalopathies in the same host genotype.

Conclusions

Atypical scrapie is consistently transmissible within AHQ homozygous sheep, and the disease phenotype is preserved on sub-passage.